Anatomy and Physiology NOTES 4

8/13/2019 Anatomy and Physiology NOTES 4

1/38

ANATOMY AND PHYSIOLOGY EXAM 4CHAPTER 14: THE BRAIN AND CRANIAL NERVES

-In humans, Brain to Body ratio is very high (smartness)

-Large cerebral cortex

-Expanded frontal lobes (higher functions- self-control/planning ability/reasoning/abstractthinking)

Brain Development

-Neural tube flexes and forms 3 primary vesicles-

The forebrain, the midbrain, and Hindbrain-Encephalization- the further formation of the brain (3 rd and 1 st vesicles divide into secondaryvesicles)

-When a fetus is born- the brain looks a lot like adult brain

-Fetal brain grows very rapidly (there are about 50,000 neurons forming each second)

The telencephalon develops into the cerebrum and lateral ventricles . The diencephalon forms the thalamus, hypothalamus, epithalamus , and third ventricle . The metencephalon becomes the pons, cerebellum , and upper part of the fourth ventricle . The myelencephalon forms the medulla oblongata and lower part of the fourth ventricle .

The mesencephalon (mes enSEF alon), or midbrain, gives rise to the midbrain and aqueduct of themidbrain (cerebral aqueduct) .

Cerebellum- second largest part of the brain (often called little brain)

Cerebrum- the newest edition to brain according to evolutionary history/ where frontal lobe is(planning/reasoning/abstract thought is there)

Protective covering (Meninges) - continuous with meninges of spinal cord

-Cranial meninges have similar function/structure to spinal meninges (same names)

Dura mater- has 2 layers in cranial meninges

-External periosteal layer- superficial layer against bony coverings

-Internal meningeal layer-

Extensions of Dura mater- hard membranes that separate areas (divide intracranial vault in acouple of ways)

8/13/2019 Anatomy and Physiology NOTES 4

2/38

-Falx cerebri- fold of dura mater (descend from dura, vertically, in the longitudinalfissure)

-Longitudinal fissure- separates the 2 hemispheres in cerebrum

-Falx cerebelli- an extension of the dura mater that separates the 2 hemispheres of the

cerebellum.-Tentorium cerebelli- extension of dura mater that is important in clinical setting-tumors are often separated in relation to tentorium cerebelli (supra-tentorium andinfra-tentorium)

-Often in children, tumors are found in infratentorium

-Often in Adults, tumors are found in supra tentorium

-If there is any brain swelling, there will not be much movement in the extension of thedura mater (it could build up intercranial pressure-serious brain injury)

Brain Blood Flow- Brain is a huge amount of the mass of body (in relation to many other bodyorgans) (makes up about 2% of total body weight) (makes up about 20% of blood supply tobrain) brain is a huge consumer- 20% of oxygen/glucose (energy)

-Arteries- oxygenated blood- red

-Internal carotid artery- large supply of blood to brain (anterior portion of brain)

-Vertebral arteries- supply posterior portion of brain.

8/13/2019 Anatomy and Physiology NOTES 4

3/38

-Veins- deoxygenated blood- blue

-Internal jugular vein- important vessels for veinus return

Blood-Brain barrier- keep harmful substances from brain (protects brain)

-there is a huge metabolic cost of this (active transport of glucose molecules acrossbarrier- need transport energy/ ATP)

-Ability to get drugs across barrier- (benefit-antibiotics) (Disadvantage- Old Benadrylmakes you feel drowsy)

Production and flow of CSF

-Cerebrospinal fluid- found in subarachnoid space in brain

-CSF circulates through internal cavities in brain (brain ventricles)

Ventricles - There is one lateral ventricle in each hemisphere of the cerebrum. (Think of them asventricles 1 and 2.) Anteriorly, the lateral ventricles are separated by a thin membrane, theseptum pellucidum . The third ventricle is a narrow slit like cavity along the midline superior tothe hypothalamus and between the right and left halves of the thalamus. The fourthventricle lies between the brain stem and the cerebellum.

-CSF- mechanical protection (shock absorber)/ circulation (take wastes away frombrain/nutrients towards brain)/ maintain homeostasis (maintain PH of blood flow inbrain)

Arachnoid mater-

Pia mater-

The Brain Stem- Superior to spinal cord/ continuous with spinal cord

-Made of midbrain/pons/medulla oblongata

Medulla oblongata- considered the vital functional center of brain-

-Cardiovascular center- controls heart rate/ the force of heartbeats/diameter of bloodvessels

-Respiratory center- controls rate/rhythm of breathing

-Vomiting/coughing/sneezing

-Associated with Cranial nerve nuclei with nerves 8-12

-Portions of 4 th ventricle extends into medulla

Pons- superior to medulla (located anterior to cerebellum)

-considered the bridge that connects the spinal cord with the brain

-Also considered to connect other parts of brain to each other

8/13/2019 Anatomy and Physiology NOTES 4

4/38

-Controls breathing- inhalation/exhalation

-Contain the nuclei associated with 4 pairs of cranial nerves (5-8)

-Nerve 5 emerges directly from pons

-Nerves 6, 7, and 8 emerge from space between pons and medulla

Midbrain- extends from pons (Diencephalon is superior)

-Where cerebral aqueduct is found (pass through midbrain- job is to connect the 3 rd and4 th ventricle

-Posterior part has 4 rounded elevations (superior/inferior colliculi)

-Colliculi are reflex centers (sensory reflexes- visual/auditory/startle reflex)

-The origin of cranial 3 and 4 can be found here

Cerebellum- the second largest portion of brain (sometimes called the little brain)

-Found inferior to cerebrum and posterior to brain stem-Separated from cerebrum by transverse fissure

-Vermis- central constriction- separates the 2 cerebral hemispheres

-Important in comparing intended movements and actual skeletal movements (being ina hurry, a running up a flight of stairs, and missing a step)

-Regulation of posture

-Maintain equilibrium and balance

Diencephalon- superior to mid brain/ located in midbrain-midline (you have to cut brain to see

it)

-Develops from procencephalon (more primitive then cerebral cortex)

-Surrounds third ventricle (CSF circulation)

-Thalamic structures are found here

Thalamus- relay station for sensory impulses that go to cerebral cortex (with the exception ofthe sense of smell- which is associated with hypothalamus)

-has sensations of pain/touch/temperature/pressure all are relayed to thalamus on theirway to higher centers of cerebral cortex

Epithalamus- found superior and posterior in relation to the thalamus

-Pineal gland- gland that secretes melatonin (important for regulation of sleep cycle)(more secreted in darkness than in daylight)

Hypothalamus- hormones found here that control different homeostatic functions

-controls Autonomic nervous system

8/13/2019 Anatomy and Physiology NOTES 4

5/38

8/13/2019 Anatomy and Physiology NOTES 4

6/38

PART FUNCTION

Dissection Shawn Miller, PhotographMark Nielsen

Smooths and coordinates contractions of skeletal muscles. Regulates postureand balance. May have role in cognition and language processing.

DIENCEPHALON

Dissection Shawn Miller, PhotographMark Nielsen

Thalamus: Relays almost all sensory input to cerebral cortex. Contributes tomotor functions by transmitting information from cerebellum and basal nucleito primary motor area of cerebral cortex. Plays role in maintenance ofconsciousness.

Hypothalamus: Controls and integrates activities of autonomic nervoussystem. Produces hormones, including releasing hormones, inhibitinghormones, oxytocin, and antidiuretic hormone (ADH). Regulates emotionaland behavioral patterns (together with limbic system). Contains feeding andsatiety centers (regulate eating), thirst center (regulates drinking), andsuprachiasmatic nucleus (regulates circadian rhythms). Controls bodytemperature by serving as body's thermostat.

Epithalamus: Consists of pineal gland (secretes melatonin) and habenularnuclei.

CEREBRUM

Dissection Shawn Miller, PhotographMark Nielsen

Sensory areas of cerebral cortex are involved in perception of sensoryinformation; motor areas control execution of voluntary movements;association areas deal with more complex integrative functions such asmemory, personality traits, and intelligence. basal nuclei help initiate andterminate movements, suppress unwanted movements, and regulate muscletone. limbic system promotes range of emotions, including pleasure, pain,docility, affection, fear, and anger.

Gyrus- folds of cerebral cortex

Fissures- deep folds of cerebral cortexSulcus- Shallow grooves

8/13/2019 Anatomy and Physiology NOTES 4

7/38

8/13/2019 Anatomy and Physiology NOTES 4

8/38

-linking the left motor cortex with the right motor cortex

-left motor cortex controls the right side of the body

-right motor cortex controls the left side of the body

Basal Nuclei- centers of cell bodies that are found deep in the cortex (help initiate andterminate movements/help suppress unwanted movements/help regulate muscle tone) (helpcontrol subconscious contractions of skeletal muscle- when youre walking you swing yourarms/if you hear something funny you will laugh)

Limbic system- encircle the upper part of the brain stem and corpus callosum

-A ring of structures on the inner border of our cerebrum

-Associated with the floor of the Diencephalon

-Does not represent any one part of brain (it is a functional unit of its own)

-composed of parts of cerebral cortex/diencephalon/ midbrain

-Sometimes called the emotional brain -plays primary role in your range of emotions(pleasure/pain/calmness/affection/fear/anger)

-Works with the cerebrum to help with memory function (remembering something andit brings up a good or bad emotion)

Brain Waves- (EEG- electro encephalogram-electrodes that are placed on the surface of headthat measure brain function electricity coming off of brain)

-EEG are useful in studying normal brain functions/changes- (ex: sleepdisorder/epilepsy/metabolic disorders/sites of trauma)

-EEG are used to determine if life is present (if there is detectable brain activity- theperson is still alive) (brain death- if there is little or no brain activity)

Alpha waves- waves that are present when you are awake and go away when you are asleep

Beta waves- waves that are present with some sort of sensory input (nervous system is in anactive state at that point) and mental activity

Theta waves- waves that can indicate emotional stress and brain disorders

Delta waves- waves that appear only when you are asleep (in adults)

-Delta waves when you are awake can indicate brain damage

8/13/2019 Anatomy and Physiology NOTES 4

9/38

Cranial Nerves- 12 CN (1-12 using roman numerals)

-They come off of our brain (not part of CNS)

-has a single root-mostly mixed sensory and motor tracts (some sensory only)

-Found in head/neck (vagus nerve is the exception)

1- Olfactory- sense of smell2- Optic- sense of sight3- Oculomotor (innervate the Extraocular muscles) supplies motor input to eyelid

muscles/facilitates pupillary constriction4- Trochlear(innervate the Extraocular muscles)5- Trigeminal- the major sensory nerve of the face (has 3 large branches that supply the

different areas of the face- othalamic/maxillary/mandibular branch)6- Abducens(innervate the Extraocular muscles)7- Facial (5 large somatic branches that innervate the muscles of facial expression) Gives a

little bit of taste sensation to the anterior 2/3s of tongue (if we injury this nerve we canget bells palsy - lose innervation of facial expression muscles- inability to closeeyes/impaired taste/loss of control over salivation)

8- Vestibulocochlear nerve- vestibule- inner ear- info about balance/ cochlear- helpsinnervate ears so that we can hear (damage to cranial nerve 8-vertigo/ringing of ears(tinnitus)/potentially deafness)

9- Glossopharyngeal- carry taste sensation/carry ANS impulses(action potentials) tosalivary glands/innervates mechanoreceptors of carotid body/carotid sinus- importantin sensing and dealing with changes in blood pressure)

10- Vagus Nerve- (wandering nerve) the nerve that leaves the head and neck/ responsiblefor carrying parasympathetic efferent motor neurons to organs in the thorax andabdomen

11- Spinal accessory nerve- gives us somatic motor innervation to the trapezius and thesternocleidomastoid

8/13/2019 Anatomy and Physiology NOTES 4

10/38

8/13/2019 Anatomy and Physiology NOTES 4

11/38

CRANIAL NERVE COMPONENTS PRINCIPAL FUNCTIONS

Glossopharyngeal(IX)

Mixed

Sensory Taste from posterior one third of tongue.

Proprioception in some swallowing muscles.

Monitors blood pressure and oxygen and carbon dioxide levelsin blood.

Touch, pain, and thermal sensations from skin of external earand upper pharynx.

Motor(branchial)

Assists in swallowing.

Motor(autonomic)

Secretion of saliva.

Vagus (X) Mixed

Sensory Taste from epiglottis.

Proprioception from throat and voice box muscles.

Monitors blood pressure and oxygen and carbon dioxide levelsin blood.

Touch, pain, and thermal sensations from skin of external ear.

Sensations from thoracic and abdominal organs.

Motor(branchial)

Swallowing, vocalization, and coughing.

Motor(autonomic)

Motility and secretion of gastrointestinal organs.

Constriction of respiratory passageways.

Decreases heart rate.

Accessory (XI) Motor

Branchial Movement of head and pectoral girdle.

Hypoglossal (XII) Motor

Somatic Speech, manipulation of food, and swallowing.

Chapter 15: The Autonomic Nervous System

8/13/2019 Anatomy and Physiology NOTES 4

12/38

-ANS has sympathetic and parasympathetic divisions

-ANS job is to contribute to homeostasis in body by responding to subconscious visceralsensations

-Excites or inhibit smooth muscle/ cardiac muscle/ many glands

-Includes autonomic sensory neurons/integration centers (in CNS)/autonomic motor neurons

Enteric Nervous System- specialized network of nerves/ganglia that form an independentnetwork (found in GI tract)

-Somatic motor neurons- takes motor impulse from spinal cord to skeletal muscle

-If this stopped, the muscle would lose muscle tone paralyzed muscle

-Controls breathing

-ANS operates without conscious control

-Integration centers are usually found in hypothalamus/brain stem (regulation for ANS)

-Sensory receptors- interoceptors- located in blood vessels/visceral organs/muscles (foundthroughout nervous system- job is to monitor the conditions of the internal environment)

-Chemoreceptor- monitor carbon dioxide level in blood

-Mechanoreceptors- monitor the degree of stretch in organs/blood vessels

Autonomic motor neurons- increasing (excitability) or decreasing (inhibition) activities in tissues

-Because it cannot be controlled- this is how we monitor people during polygraph (lie-detector) tests

-Biofeedback techniques- (people who do yoga) - learn to control processes likebreathing

How we get information to effectors-

-Pre-ganglionic neuron leads to intermediate ganglion

-Post-ganglionic neuron that innervates an effector

Somatic Nervous System Autonomic Nervous System

Sensory input From somatic senses andspecial senses.

Mainly from interoceptors; some from somatic sensesand special senses.

Control of motoroutput

Voluntary control fromcerebral cortex, withcontributions from basalganglia, cerebellum, brainstem, and spinal cord.

Involuntary control from hypothalamus, limbic system, brain stem, and spinal cord; limited control fromcerebral cortex.

Motor neuron One neuron pathway: Usually two neuron pathway: Preganglionic neurons

8/13/2019 Anatomy and Physiology NOTES 4

13/38

8/13/2019 Anatomy and Physiology NOTES 4

14/38

Inferior mesenteric ganglia- is near the beginning of the inferior mesenteric artery in the middleof the abdomen.

Aorticorenal ganglia- (same as Renal Ganglia)

-Axons can leave sympathetic trunk in 4 different ways:

-Travel with spinal nerves

-Form a network of periarterial (around artery) preganglionic neurons (travel superiorlyand synapse with the cervical ganglia)

-Post-ganglionic axons leave the sympathetic trunk and form sympathetic nerves thatinnervate heart and lungs.

-Pre-ganglionic axons that leave sympathetic trunk without synapsing (form splenicnerve)

-Some axons of some post ganglionic neurons leave sympathetic trunk through gray ramus and

merge with anterior ramus of spinal nerve-Gray Rami Communicantes-sympathetic post ganglionic axons (jobs is to connect ganglia ofsympathetic trunk to spinal nerves)

- Sympathetic nervous system creates a diverging circuit (wide spread)

-A single sympathetic pre ganglionic fiber synapse with 20 or more branches

-Post ganglionic axons terminates with different effectors (Makes sympatheticresponses wide spread)

-Many of the sympathetic responses are very difficult to control (extreme anger)

Parasympathetic division- (the rest and digest response)

-Parasympathetic ganglia (terminal ganglia) - located far from own origin

-the terminal end of pathways near effector organs (located close to where they work)

-Cell body of pre-ganglionic neurons that participate in motor responses in PSNS- located in 4cranial nerves found in brain stem (CN 3/7/9/10)

-Also in lateral gray matter in sacral areas of the spinal cord (S2-S4)

-CN 10 carries about 80% of parasympathetic flow to organs found in thorax and upperabdomen

-Lower abdominal and pelvic organs are innervate by sacral output

-Pelvic splenctic nerves synapse with parasympathetic post ganglionic neurons located in wallsof viscera

-From terminal ganglia post synaptic ganglia innervate smooth muscle and glands. (Walls ofcolon/ureters/urinary bladder/ reproductive organs)

8/13/2019 Anatomy and Physiology NOTES 4

15/38

-Pre synaptic parasympathetic neurons synapse with 4-5 post synaptic neurons

-go to a single visceral effector

-Parasympathetic stimulations goes to nice narrow specific destination

Sympathetic (Thoracolumbar) Parasympathetic (Craniosacral)

Distribution

Wide regions of body: skin, sweat glands,arrector pili muscles of hair follicles, adiposetissue, smooth muscle of blood vessels.

Limited mainly to head and toviscera of thorax, abdomen, and

pelvis; some blood vessels.

Location ofpreganglionic neuroncell bodies and site ofoutflow

Lateral gray horns of spinal cord segments T1 L2. Axons of preganglionic neurons constitutethoracolumbar outflow.

Nuclei of cranial nerves III,VII, IX, and X and lateral graymatter of spinal cord segmentsS2 S4. Axons of preganglionicneurons constitute craniosacraloutflow.

Associated ganglia Sympathetic trunk ganglia and prevertebralganglia.

Terminal ganglia.

Ganglia locations Close to CNS and distant from visceraleffectors.

Typically near or within wall ofvisceral effectors.

Axon length anddivergence

Preganglionic neurons with short axonssynapse with many postganglionic neuronswith long axons that pass to many visceraleffectors.

Preganglionic neurons withlong axons usually synapsewith four to five postganglionicneurons with short axons that

pass to single visceral effector.

White and gray ramicommunicantes

Both present; white rami communicantescontain myelinated preganglionic axons; grayrami communicantes contain unmyelinated

postganglionic axons.

Neither present.

Neurotransmitters Preganglionic neurons release acetylcholine(ACh), which is excitatory and stimulates

postganglionic neurons; most postganglionicneurons release norepinephrine (NE);

postganglionic neurons that innervate mostsweat glands and some blood vessels inskeletal muscle release ACh.

Preganglionic neurons releaseACh, which is excitatory andstimulates postganglionicneurons; postganglionicneurons release ACh.

Physiological effects Fight or flight responses.

ANS Neurotransmitters-

-There are over 100 Neurotransmitters-

-Only 2 are used to a great degree

8/13/2019 Anatomy and Physiology NOTES 4

16/38

-Acetocholine-(ACh) transmit info from ANS

-Norepinephrine (NE)

-Synapses that uses ACh are cholinergic

-Synapses that use NE are adrenergic

-Neurotransmitters used in the Parasympathetic ganglia are ACh

-Receptors that respond to this release are called cholinergic receptors (nicotinic-found inganglia/muscarinic-found in synapses of effector organs)

-Neurotransmitter used most at sympathetic post ganglionic synapses is NE

-Synapses for sweat glands use ACh at sympathetic post ganglionic synapses

-Neurotransmitter used at parasympathetic post ganglionic synapses is ACh

Visceral Effector EFFECT OF SYMPATHETIC STIMULATION( OR Adrenergic Receptors, Except As Noted )*

Effect Of Parasympathetic Stimulation(Muscarinic ACh Receptors)

Glands

Adrenal medullae Secretion of epinephrine and norepinephrine(nicotinic ACh receptors).

No known effect.

Lacrimal (tear) Slight secretion of tears (). Secretion of tears.

Pancreas Inhibits secretion of digestive enzymes and thehormone insulin ( ); promotes secretion of the

hormone glucagon ( ).

Secretion of digestiveenzymes and the hormoneinsulin.

Posterior pituitary Secretion of antidiuretic hormone (ADH) ( ). No known effect.

Pineal Increases synthesis and release of melatonin (). No known effect.

Sweat Increases sweating in most body regions(muscarinic ACh receptors); sweating on palms andsoles ( ).

No known effect.

Adipose tissu e Lipolysis (breakdown of triglycerides into fattyacids and glycerol) ( ); release of fatty acids into

blood ( and ).

No known effect.

Live r Glycogenolysis (conversion of glycogen intoglucose); gluconeogenesis (conversion ofnoncarbohydrates into glucose); decreased bilesecretion ( and ).

Glycogen synthesis; increased bile secretion.

Kidney, juxtaglomerular

Secretion of renin ( ). No known effect.

8/13/2019 Anatomy and Physiology NOTES 4

17/38

Visceral Effector EFFECT OF SYMPATHETIC STIMULATION

( OR Adrenergic Receptors, Except As Noted )* Effect Of Parasympathetic Stimulation(Muscarinic ACh Receptors)

cell s

Cardiac (Heart) Muscle

Increased heart rate and force of atrial andventricular contractions ( ).

Decreased heart rate;decreased force of atrialcontraction.

Smooth Muscle

Iris, radial muscle Contraction dilation of pupil ( ). No known effect.

Iris, circular muscle No known effect. Contraction constriction of pupil.

Ciliary muscle ofeye

Relaxation to adjust shape of lens for distant vision( ).

Contraction for close vision.

Lungs, bronchialmuscle

Relaxation airway dilation ( ). Contraction airwayconstriction.

Gallbladder andducts

Relaxation to facilitate storage of bile in thegallbladder ( ).

Contraction release of bileinto small intestine.

Stomach andintestines

Decreased motility and tone ( , , );contraction of sphincters ( ).

Increased motility and tone;relaxation of sphincters.

Spleen Contraction and discharge of stored blood intogeneral circulation ( ). No known effect.

Ureter Increases motility ( ). Increases motility (?).

Urinary bladder Relaxation of muscular wall ( ); contraction ofinternal urethral sphincter ( ).

Contraction of muscular wall;relaxation of internal urethralsphincter.

Uterus Inhibits contraction in nonpregnant women ( ); promotes contraction in pregnant women ( ).

Minimal effect.

Sex organs In males: contraction of smooth muscle of ductus(vas) deferens, prostate, and seminal vesicleresulting in ejaculation ( ).

Vasodilation; erection ofclitoris (females) and penis(males).

Hair follicles,arrector pili muscle

Contraction erection of hairs resulting ingoosebumps ( ).

No known effect.

Vascular Smooth Muscle

8/13/2019 Anatomy and Physiology NOTES 4

18/38

Visceral Effector EFFECT OF SYMPATHETIC STIMULATION

( OR Adrenergic Receptors, Except As Noted )* Effect Of Parasympathetic Stimulation(Muscarinic ACh Receptors)

Salivary glandarterioles

Vasoconstriction, which decreases secretion ofsaliva ( ).

Vasodilation, which increasessecretion of saliva.

Gastric glandarterioles

Vasoconstriction, which inhibits secretion ( ). Secretion of gastric juice.

Intestinal glandarterioles

Vasoconstriction, which inhibits secretion ( ). Secretion of intestinal juice.

Coronary (heart)arterioles

Relaxation vasodilation ( ); contraction vasoconstriction ( , ); contraction vasoconstriction (muscarinic ACh receptors).

Contraction vasoconstriction.

Skin and mucosalarterioles

Contraction vasoconstriction ( ). Vasodilation, which may not be physiologically significant.

Skeletal musclearterioles

Contraction vasoconstriction ( ); relaxation vasodilation ( ); relaxation vasodilation(muscarinic ACh receptors).

No known effect.

Abdominal visceraarterioles

Contraction vasoconstriction ( , ). No known effect.

Brain arterioles Slight contraction vasoconstriction ( ). No known effect.

Kidney arterioles Constriction of blood vessels decreased urinevolume ( ).

No known effect.

Systemic veins Contraction constriction ( ); relaxation dilation ( ).

No known effect.

-Sympathetic stimulations- leads to secretion of NE (in adrenal glands) result of secretion is anincrease in rate and strength of heart beat/ constriction of blood vessels in non-essential organs(decrease gastrointestinal activity) / dilation of blood vessels in essential organs (skeletalmuscle/cerebral cortex)/increase in rate and depth of breathing/ liver converts glycogen toglucose

-Ex: arachnophobia (fear of spiders) - when you see a spider you either fight of flight

Physiology of the ANS

Parasympathetic response-

SLUDD-

-Salivation (increased)

-Lacrimation (increased) -crying

8/13/2019 Anatomy and Physiology NOTES 4

19/38

8/13/2019 Anatomy and Physiology NOTES 4

20/38

-When we are asleep

-When we are learning

-When we are accessing memory

(Ex: when you walk into a Starbucks- you can hear the music from the speakers/you can smellthe coffee/ there are people all around you talking and moving)

Sensory Modalities each type of sensation

-Each sensory neuron carries information for one modality

Somatic senses (body senses) - include tactile sensations(touch/pressure/tickling/itching/thermal sensation/pain/proprioception)

-Proprioception- awareness of position (limbs or joints)

Visceral senses- provide sensory information of internal organs

Special senses- olfaction/vision/hearing

The process of sensation begins in a sensory receptor (can be either specialized cells ordendrites of a sensory neuron)

-Stimulus- activates certain sensory receptors (stimulus- is a change in external/internal

environment) (focus on one set of sensory receptors)-Selectivity- allows stimulus to selectively stimulate certain receptors

-Sensory receptors produce 2 kinds of potentials:

-Generator potential- stimulating the dendrites of the pre-nerve endings/encapsulatednerve endings

-When a generator potential is large enough to reach threshold it will trigger 1 or moreimpulses in the axon (results in propagation of nerve impulse along axon to CNS) itgenerates an action potential

-Receptor potential- sensory receptor that are separate cells produce graded potentials-For sensation to occur there usually needs to be 4 events:

1) Stimulation of sensory receptor have appropriate stimulus that occurs in receptors field

2) Transduction of the stimulus- the sensory receptor converts energy in a stimulus into apotential

3) Generation of nerve impulses- where potentials reach threshold in a first-order neuron

8/13/2019 Anatomy and Physiology NOTES 4

21/38

-First order neuron- first neuron in a specific tract

4) Integration of sensory input- occur when a particular region of the CNS integrates a numberof sensory impulses

-Result is conscious sensation or perceptions

Sensory preceptors can be grouped in many classes: (functional/structurally)

Structure-

Free nerve endings- are bare dendrites; they lack any structural specializations that can be seenunder a light microscope

-Receptors for pain, temperature, tickle, itch, and some touch sensations are free nerveendings

Encapsulated nerve endings- Their dendrites are enclosed in a connective tissue capsule thathas a distinctive microscopic structure for example, Pacinian corpuscles

-Receptors for other somatic and visceral sensations, such as pressure, vibration, andsome touch sensations

Where it is found/ origin of stimuli-

Exteroreceptors- found near external surfaces

Interoceptors- found in internal surfaces (also called visceroceptors) (can be found in bloodvessels/ visceral organs/ muscles/ within nervous system)

-Nerve impulses made by interoceptors are not consciously perceived normally

-When stimulus is very strong there can be activation of them that result inpain/pressure

Proprioceptors- found in muscles/tendons/joints (help feel position/movement)

-Proprioceptors are also located in inner ear (position/movement of whole body)

Type of stimulus detected-

Mechanoreceptors- feel pressure/motion/sound/vibration/gravity (anything mechanical)Thermoreceptors- changes in temperature (hot/cold)

Nociceptors- respond to pain

Photoreceptors- activated by photons of light

Chemoreceptors- changes in chemicals/individual types of molecules (internally)

-Sense of taste and smell

8/13/2019 Anatomy and Physiology NOTES 4

22/38

-Important for differences in chemical stimuli to differences in body fluids

Osmoreceptors- detect changes in osmotic pressure

Basis Of Classification Description

MICROSCOPIC STRUCTURE Free nerve endings Bare dendrites associated with pain, thermal, tickle, itch, and some touch sensations.

Encapsulated nerveendings

Dendrites enclosed in connective tissue capsule for pressure, vibration, and sometouch sensations.

Separate cells Receptor cells synapse with first order sensory neurons; located in retina of eye(photoreceptors), inner ear (hair cells), and taste buds of tongue (gustatory receptorcells).

RECEPTOR LOCATION AND ACTIVATING STIMULI

Exteroceptors Located at or near body surface; sensitive to stimuli originating outside body; provide information about external environment; convey visual, smell, taste, touch, pressure, vibration, thermal, and pain sensations.

Interoceptors Located in blood vessels, visceral organs, and nervous system; provide informationabout internal environment; impulses usually are not consciously perceived butoccasionally may be felt as pain or pressure.

Proprioceptors Located in muscles, tendons, joints, and inner ear; provide information about body position, muscle length and tension, position and motion of joints, and equilibrium(balance).

TYPE OF STIMULUS DETECTED

Mechanoreceptors Detect mechanical stimuli; provide sensations of touch, pressure, vibration, proprioception, and hearing and equilibrium; also monitor stretching of bloodvessels and internal organs.

Thermoreceptors Detect changes in temperature.

Nociceptors Respond to painful stimuli resulting from physical or chemical damage to tissue.

Photoreceptors Detect light that strikes the retina of the eye.

Chemoreceptors Detect chemicals in mouth (taste), nose (smell), and body fluids.

Osmoreceptors Sense osmotic pressure of body fluids.

Adaptation- the receptor/generator potential decrease their amplitude

-amplitude will decrease over time if there is a constant change

8/13/2019 Anatomy and Physiology NOTES 4

23/38

Ex: being in the elevator with a person with really bad cologne on- you can smell it reallywell (because of the tight space), but if you are in a lecture hall with that person you canbarely smell the cologne after a while

-Frequency of nerve impulses going to CNS will decrease (perception of information

decreases even though it is still there)Rapidly adapting sensations- smell/touch/pressure

Mechanoreception - a lot mechanoreceptors and Nociceptors in skin

Nociception - pain is really important in terms of protective function

-Important for survival

-Have free nerve endings that activate by tissue damage (damagethermal/mechanical/chemical)

-Nociceptors found in every tissue in body except brain

Fast pain - occur rapidly (localized/acute pain)

-Happens because nerve impulses propagate along medium diameter/myelinated fibersof the A nerve variety

Slow pain- begins after a stimulus is applied/ gradually increases in intensity (can occur over aperiod of seconds/minutes/hours/days) (Ex: pain associated with a toothache)

-Impulses go over small diameter C fibers (unmyelinated)

Superficial somatic pain- pain that arises from stimulation of receptors in skin

Deep somatic pain - From stimulation of receptors in skeletal muscle/ joints/ tendons/ fascia

Visceral pain- result of Nociceptors stimulation in visceral organs (many times it is felt just deepto skin that overlays the organ) (Ex: if kidney hurts- your back will hurt that is just over thekidney)

Referred pain - a surface far from the organ is sore/hurting (upper neck and shoulder can bereferred pain for liver and gallbladder

8/13/2019 Anatomy and Physiology NOTES 4

24/38

Proprioception-

Muscle Spindles - proprioceptors in skeletal muscles

-Monitor changes in muscle length

-Give information about stretch reflex that the muscles do

-The brain sets an overall level of muscle tone

-Muscle tone - a small degree of contraction that is present when a muscle is at rest

-Each muscle spindle consists of slowly adapting nerves (wrap around 3-10 specializedmuscle fibers)

-Connective tissue anchors spindle to Epimysium and perimysium

-Very dense (many) in muscles that control fine motor movements (eyes/hands)

-Less dense in muscles that control large forceful movements (quadriceps)

Somatic Sensory Pathways-

First-order neuron - Is unipolar in structure (their cell body is located in the dorsal root ganglia-

found just outside CNS) (The other end terminates in the posterior gray horns of spinal cord)Second-order neuron - conduct ascending impulses from brain stem to the thalamus

-all of somatic sensory information from one side of the body reaches the thalamus onthe opposite side (contralateral)

Third-order neuron - conduct impulses from the thalamus to the primary somatosensory area ofthe cortex (thalamus to cerebrum)

8/13/2019 Anatomy and Physiology NOTES 4

25/38

-Happens on the same side of the brain (Ipsilateral)

-Somatic sensory neurons and their neurons give us somatic sensations

-Not evenly distributed throughout the body

-There are peripheral areas of the brain that have the highest density (largest amount ofgray matter)

-Most sensitive areas are the tip our tongue/fingertips/lips

Spinocereballar tracts- there are two major Spinocereballar tracts-

-Carry information from spinal cord to cerebellum

-Not consciously perceived

-Sensory impulses sent along are important for posture/balance/coordination of skilledmovements

Motor activity- begin in the primary motor areas of the precentral Gyrus and in other cerebralintegrative centers

Upper motor Neuron (UMN)- Any motor neuron that is not directly responsible for stimulatingtargeted muscle

-Connect brain to appropriate level in spinal cord

-Basal nuclei/cerebellum influence movements through their effects on UMN

- Direct motor pathways- provide input to lower motor neurons via axons that extend directlyfrom the cerebral cortex

- Indirect motor pathways- provide input to lower motor neurons from motor centers in thebasal nuclei, cerebellum, and cerebral cortex.

Lower motor Neurons (LMNs) - all excitatory and inhibitory signals that control movement-converge on second-order neurons (the second order neurons are called LMNs)

-Descent of neurons that innervate skeletal muscles

-LMNs are sometimes called the final common pathway- because they provide output ofCNS to skeletal muscle fibers

-Axons of the LMNs extend through cranial nerves to skeletal muscles (innervatemuscles of head/face)

-When they go through the spinal nerves they innervate the muscles of limbs and trunk

-Two major tracts are the Lateral and Anterior- corticospinal tracts (start from cortexend in spinal cord

Integrative Functions of the Cerebrum

8/13/2019 Anatomy and Physiology NOTES 4

26/38

The integrative functions include cerebral activities such as sleep and wakefulness, learningand memory, and emotional responses

Humans sleep and awaken in a 24hour cycle called a circadian rhythm

How does your nervous system make the transition between these two states? Because

stimulation of some of its parts increases activity of the cerebral cortex, a portion of thereticular formation is known as the reticular activating system (RAS)

Arousal , or awakening from sleep, also involves increased activity in the RAS.

Learning- is the ability to acquire new information or skills through instruction or experience.

Memory is the process by which information acquired through learning is stored and retrieved.

Immediate memory is the ability to recall ongoing experiences for a few seconds.

Shortterm memory is the temporary ability to recall a few pieces of information for secondsto minutes

Information in shortterm memory may later be transformed into a more permanent type ofmemory, called longterm memory, which lasts from days to years.

The reinforcement that results from the frequent retrieval of a piece of information iscalled memory consolidation.

Long term potentiation (LTP) (ptenshshun) is believed to underlie some aspects ofmemory; transmission at some synapses within the hippocampus is enhanced (potentiated) forhours or weeks after a brief period of highfrequency stimulation.

Chapter 17: The Special Senses -Sensation can be conscious or subconscious in terms of our awareness of it -Can be a response from internal or external stimulus

-Internal stimulus- molecules that transmit taste/smell to chemoreceptors on nose/tongue

-Force of gravity acts on equilibrium receptors in inner ear (sense changes in inertia/motion)-balance

Special sense- smell/taste/vision/hearing/equilibrium

-Head is a very important sensory platform for these senses

-are concentrated in specific locations in the head

-are anatomically distinct structures

8/13/2019 Anatomy and Physiology NOTES 4

27/38

-form complex neural pathways

Olfaction and Gustation (taste)-

-Olfaction- process of perceiving smells

-Both smell and taste are brought about through an interpretation of chemicals that we receiveon our chemoreceptors

-Travel not only to cerebral cortex and limbic system

-We can have emotional responses to certain smells/tastes

-Gustation and olfaction work together (olfaction is much stronger and much more sensitive)

Olfactory epithelium - where we have chemoreceptors of olfaction

-located in superior part of the nasal cavity

-Covering the surface of the cribriform plate of ethmoid bone-Extends along the superior nasal concha

-Consists of 3 kinds of cells:

-Olfactory receptor- bipolar neuron/cilia is attached to it (cilia- olfactory hairs)(Between 10-100 in our nose that respond odor molecules)

-Supporting cells- provides support/nourishment (takes care of olfactoryreceptors

-Basal cells- stem cells replace olfactory receptors

-Because it is more sensitive than gustation- it can be stimulated a 1000 times morethan gustation

-A smell can be detected by a concentration 1/25 th of a billionth of a milligram permilliliter per air

-When an odorant (odor molecule) binds to a receptor- it will initiate a cascade ofevents

1) G protein and secondary messenger lead to the production of C-amp thatstimulates sodium channels to open

2) Inflow of sodium ions that helps us form are generator potentials3) Once generated, nerve impulses travel through the two olfactory nerves toolfactory bulbs to olfactory tract to primary olfactory area in the temporal lobeof the cortex.

8/13/2019 Anatomy and Physiology NOTES 4

28/38

1) Nerve impulse travels through cranial nerve 1 (olfactory nerve)

2) Goes to olfactory bulb3) Head to olfactory tract in temporal lobe of cortex

The sense of olfaction is the only sensory modality that has direct sensory projection(goes directly to cortex)

-Sensory pathways- they adapt

-Olfactory receptors- adapt very little

Olfactory sensory pathways-

-Decrease activity by 50% within the first minute

-In 1-2 minutes you will be completely accommodated to that smell

Parasympathetic motor- Supporting cells/glands are innervated by facial nerve (CN 7)(component provides parasympathetic motor innervation to lacrimal glands/mucousmembranes in nasal cavity- this is why certain odors make your nose run/make you tear up)

8/13/2019 Anatomy and Physiology NOTES 4

29/38

Gustation (taste)-

Chemicals that stimulate our gustatory receptors (similar to olfaction- they are chemo senses)

-once one of these chemicals dissolves in saliva it can come into contact with gustatoryhair (sense of taste occurs)

-Receptor potential- stimulates exocytosis of synaptic vesicles (gustatory cells)

-Neurotransmitter molecule that triggers a nerve impulse- then it sends information to firstorder sensory neurons (synapse with gustatory cells)

-Gustation is much simpler than olfaction

-There are 5 primary tastes that we can distinguish:

-Sour

-Sweet

-Bitter

-Salty

-Umami (savory or meaty)

-Flavors that we actually taste are a combination of those 5 primary tastes and also fromchemosensory cues from olfactory sense

-Tactile sensation is very important (texture can cause someone to eat or not eat a certainfood)

Taste buds- 10,000 taste buds located on tongue/soft palate (back roof ofmouth)/pharynx/larynx

-Number of taste buds decreases with age

-Gustatory receptor cells--Each taste bud consists of 50 receptor cells that are surrounded bysupporting cells (mature basal cells)

-Basal cells- located near the connective tissue base (multiply and differentiate)

-First become supporting cells around the taste bud- then they become gustatory

receptor cell inside the taste budGustatory hair- single long microvillus structure (project form each receptor cell to the surfacethrough a taste pore)

-Each gustatory receptor cell has a life span of about 10 days

3 different types of papillae: (elevation on tongue that provide a rough texture)

8/13/2019 Anatomy and Physiology NOTES 4

30/38

Vallate papillae- composed of 12 very large papillae

-Found in a row at the back of the tongue

-Each papillae houses 3-100 taste buds

Fungiform papillae- have a mushroom shape

-Scattered throughout entire surface of tongue

-Contain about 5 taste buds each

Foliate papillae- found in small trenches along the lateral margins of tongue

-most of their taste buds degenerate in early childhood

Filliform papillae- found over the entire surface of tongue

-do not house any taste buds (They contain tactile receptors)

-increase friction between tongue and food (makes it easier to move food around in the

oral cavity)

3 cranial nerves that contribute to gustation- (axons of first-order gustatory neurons)

-Facial nerve (7) - serve taste buds in the anterior 2/3s of tongue (mostly fungiform)

-Glossopharyngeal (9) - posterior 1/3s of tongue (Vallate papillae)

8/13/2019 Anatomy and Physiology NOTES 4

31/38

8/13/2019 Anatomy and Physiology NOTES 4

32/38

Lacrimal glands- about the size of an almond

-6 to 12 excretory lacrimal ducts- coming from the lacrimal gland (lacrimal fluid runs fromlacrimal gland into lacrimal ducts and onto the surface of the conjunctiva)

-Often constant lacrimal fluid (tears) that keeps eyes moist/ evaporates off of surface of

eyes (excess of lacrimal fluid- drain inframedially into lacrimal puncta)Lacrimal puncta- 2 opening on extreme edge of eyeball

-Inferior/superior lacrimal canals- from lacrimal puncta to here

- Nasolacrimal duct- from the lacrimal canals to here

Watery eyes-

-Blocked nasolacrimal ducts- obstruction- can be inflammation of nasal mucosa (if you have acold)

-Over production of lacrimal fluid

Wall of eyeball is made into 3 different layers (tunics)

-Fibrous tunic- outer layer (sclera/ cornea-transparent epithelial surface that protects the frontof the eye)

-Cornea- helps focus light into retina (Lasik eye surgery- performed on cornea of eye tocorrect vision)

-Sclera- (white of eye) filled with a lot of collagen fibers (very tough)

-Gives eye its shape/ protects internal anatomy of our eyes

-Vascular tunic (middle tunic) - compose of choroid/cilliary body/iris

Choroid-Major vascular portion

8/13/2019 Anatomy and Physiology NOTES 4

33/38

Cilliary body- contains cilliary muscle- change shape of lenses (adapt to near/far vision)

Iris- colored portion of eyeball- consists of circular and radial smooth muscles

-Nervous tunic (inner tunic) - innermost layer- contains retina

-lines 2/3s of posterior portion of eye

-Retina consists of pigmented epithelium

-Retina- allows light to be absorbed (absorbed rather than scatter)

-Retina doesnt need to cover whole eye, because light only strikes the back of eye

Macula lutea- Retina is sometimes called this

-Fovea centralis- in the center of macula lutea (no rods/no nerve cells)-highconcentration of cones allows us to have very sharp vision

Optic disc- where the optic nerve and retinal vessels enter and exit the eyeball

-because we have this disc, there is a defect where we do not have any rods/cones onthe retina (creates a blind spot in vision-brain will correct for it though)

Photoreceptor cells-

Rods- abundant in the periphery on the retina

Cones- found more densely packed in more central areas

Rod-shape photoreceptors- each eye will contain about 120 of these

-Rods are for low light threshold or low sensitivity

-Produce low level images/black and white images

-With age, rods start to go away

Cones- function in bright light

-Produce high resolution color images

-3 varieties: correspond to pigment they contain (red/green/blue)

-complete loss in cones would result in legal blindness

-deficiency of cones in one type or another is called color-blindness

The Pupillary Response-

Pupil- the opening in the center of the iris-in the pupil there are radial muscles that radiate away from center and circular muscle

-Constriction of inner circular muscle causes pupil to constrict

-Constriction of radial muscles cause pupil to dilate

8/13/2019 Anatomy and Physiology NOTES 4

34/38

Refraction and Image-

-Normal image formation depends on refraction of light waves/accommodation of lenses/constriction of pupil/convergence of the two eyes.

Refraction is the process of bending light waves

-Both cornea and lens of eye can refract light waves

-Both cornea and lens must be functioning to focus light on the right spot for clear vision

-Since the cornea has a fixed shaped, its focal length is also fixed

-Fixed focal length causes the ability of cornea to refract light is fixed

-Lens must change shape to focus light (depends on light waves we are imaging)

Accommodation- increase in the curvature of lens for near vision (change shape of lens)

-Near point vision- is the minimum distance from eye that an object can clearly focus (4 inches-increases with age)

Myopia- nearsightedness- only close objects can be seen clearly (light rays are coming in from adistant object/focused on retina/ appear blurry)

-correcting this involves using concave lenses (negative lenses)

Hyperopia- farsightedness- only distant objects can be seen clearly (light rays coming in from anear object/ focused on retina/ appear blurry)

-Correcting this involves using convex lenses (positive lenses)

Visual TransductionLight adaptation- going from dark conditions to light conditions (very quickly- in a matter ofseconds) (changes when we get older)

Dark adaptation- going from light conditions to dark conditions (can take minutes to occur)

Color blindness- most forms are inherited

-They are an inability to distinguish between certain colors

8/13/2019 Anatomy and Physiology NOTES 4

35/38

-Because of absence or deficiency of the cones (red/green is most common)

Cause night blindness- (nyctalopia) can be caused by prolonged Vitamin A deficiency

-inability to see well in low-light levels

The Visual Pathway

Optic nerve- the axons of the retinal ganglia cells travel back towards the light (exiting theeyeball) - this is where the optic nerve travels

Optic Chiasm- where the axons have a crossing over point

-Some Axons cross to opposite side from where they were originally received

-After they pass through optic chiasm they pass through optic tracts (terminate atthalamus)

-Once they travel to thalamus they synapse with axons that project with primary visualcortex (found in occipital lobe)

Audition- process of hearing (through processing information from organs in the ear)

-The ears also contain receptors for equilibrium

-The ear is really good at picking up a lot of information such as sound vibrations

External ear- air to collect and channel sound waves

Middle ear- contains a bony system that amplify those sound vibrations

Internal ear- produce action potentials to transmit sound/balance information to brain

Pathways for sound transmission- start in ear and move to solid bone in middle ear and soundvibrations are transmitted to endolymph in inner ear.

External ear- includes Auricle (outside part of ear that you can touch/ sometimes called pinna)

-Flap of elastic cartilage covered by skin (contains ceruminous glands)

External auditory canal- approximately 1 inch long and is curved (situated in temporalbone- from external auditory meatus to tympanic membrane)

Tympanic membrane- delineation of outer ear to middle ear

Middle ear- 3 auditory ossicles

-Stapes- shaped like a stirrup

-Incus- shaped like an anvil

-Malleus- shaped like a hammer

8/13/2019 Anatomy and Physiology NOTES 4

36/38

-Tensor tympani and Stapedius- attached to auditory ossicles and dampen vibrations toprevent damage of sudden or loud sounds (Stapedius- one of smallest muscles in body)

-Auditory ossicles- has a lot of mineral-makes them very stiff and good for soundvibration (peanut brittle- very stiff, but break easily)

-Eustachian tube- connect middle ear to nasopharynx (upper portion of throat)-Consists of bone and hyaline cartilage

-It is flat or closed in its passive state

-We equalize pressure in our inner ear by swallowing- opens the tube

Inner ear-

-Outer bony labyrinth- made up of tetras part of temporal bone- divided into 3 areas

Semicircular canals-located above vestibule (contains receptors for dynamicequilibrium)

Vestibule- middle part of bony labyrinth (contains receptors for static equilibrium)

Cochlea- located anteriorly to vestibule (contains receptors for hearing) (snaleshaped (there is perilymph and endolymph)

-Scala vestibuli-channel above the cochlear duct is the scala vestibuli, which endsat the oval window

-Scala tympani-which ends at the round window

-Cochlear duct- a continuation of the membranous labyrinth into the cochlea; itis filled with endolymph

-Perilymph carries vibrations from stapes to oval window (goes up and around thescala vestibule and around scala tympani) - causes endolymph to vibrate

-Endolymph- in cochlear duct- pressure waves cause basilar membrane to vibrate

-Causes hair cells in the spiral organ of Corti to move- move againstgelatinous membrane (tectorial membrane)

-Inner membranous labyrinth-

Spiral ganglia- cell bodies for sensory organs located here (nerve impulses passing along axonsof these neurons- formed from cochlear branch of Vestibulocochlear CN)

Nerve impulses follow CN 8 to medulla/pons/midbrain/thalamus

-Go to primary auditory cortex in temporal lobe

-Slight differences in the impulses arriving in pons that allow us to locate differentsources in sound

8/13/2019 Anatomy and Physiology NOTES 4

37/38

Exam 4-What Dr. Porter said we should know1) What are the major regions of the brain2) What are the differences of brain/spinal cord3) In terms of major regions of the brain, brain stem contains 3 different parts

(pons/medulla/midbrain)4) The diencephalon- made up of 3 parts:

(Thalamus/hypothalamus/Epithalamus)5) Cerebellum-little brain/major cerebral cortex/cerebrum6) Layers covering brain/spinal cord (dura mater is different in brain-has 2

layers)7) Dura mater- has some major extensions that separate different parts of the

brain (major extension that separates cerebrum into 2 hemispheres- Falxcerebri)

8) One of the major ways we protect the brain- harmful substances stoppedfrom blood into brain (blood-brain-barrier)

9) CSF is really important- because it carries chemicals like glucose/takesglucose from blood to neurons/neuroglia

10) CSF- maintain mechanical protection/ pH balance/ circulation11) Structure in brain that is responsible for startle response- inferior

colliculi12) Different parts of the brain and their processes (what they are

responsible for13) Autonomic nervous system

8/13/2019 Anatomy and Physiology NOTES 4

38/38

14) Motor neurons and what activities they regulate (increase/decreaseactivities in activities in effector tissue

15) Post ganglionic neurons/preganglionic neurons in ANS16) Sympathetic/Parasympathetic division (what they do)17) Different receptors- cholinergic-divided into 2 types:

muscaneric/nicotinic