Nervous System Chapter 9. Functions Stimulate all movement Receive sensory input Store and integrate information Maintain homeostasis.
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Nervous System
Chapter 9
Functions• Stimulate all movement
• Receive sensory input
• Store and integrate information
• Maintain homeostasis
Organization• Two main divisions:
1. Central Nervous System (CNS)
a. Brain and spinal cord
b. Command and sensory integration center.
2. Peripheral Nervous System (PNS)
a. All nerves that communicate with spinal cord and cranial region.
Nice concept map to review
with!
Nervous System Cells
Neurons:
carries the nerve impulses, mitosis not possible after reaching maturity
Neuroglial cells:
supports neurons, does not carry impulses, mitosis is possible
throughout lifespan
Neuron cell body
Neuroglial cell nucleus
Neuroglial Cells• Most abundant in CNS
• 5 Major Types:
1. Microglial – phagocytes, protection
2. Oligodendrocytes – forms myelin in CNS
3. Astrocytes – provide support & connection between neurons and blood supply
4. Ependymal cells – lines cavities (Ventricles) of brain & spinal cord, helps form CSF, ciliated
5. Schwann cells – forms myelin in PNS
Can you find two neurons in this picture? What division of the NS is being shown here? What neuroglial cell is not shown here and
why not?
Neurons• Large in size• Very high metabolic rate• Amitotic (no replacing after
destruction), no centrioles• Extreme longevity…over 100
yrs. possible• Cell structures:
- cell body, axon, dendrites, myelin sheath, nodes of Ranvier, nucleus, axon terminals, end bulbs, synapse(If myelinated, will have Schwann cells or
Oligodendrocytes attached to axon)
Basic Neuron Anatomy
Impulses move along a one-way path!
Dendrites
Cell body
Axon
Neurons Structural Differences
1. Bipolar – rare, found in retina of eye
2. Unipolar – afferent (sensory) PNS
3. Multipolar – majority of all neurons; most in brain are multipolar.
Neuron Organization
Neuron types: Sensory, Interneurons, Motor
Neuron Functional Differences
Integrates and coordinates info from afferent, sends out response to efferent
Neuron Pathway Types
**Be able to describe the difference between the pathways.
Nerve Impulse Nerve Impulse ConductionConduction
Neuron at Resting Potential
• Membrane is polarized (charged!)
• -70mv inside cell• Inside more negative
than outside.• What keeps it neg?
Large, negative proteins, chloride ions, and nucleic acids inside.
Leaky membrane allows Na+ and K+ ions to diffuse, so Na/K pump is
always working.
Moving Action
Potential
Animation
Action potentials are pulse-like waves of voltage.
Diffusion and electrochemical attraction move ions in/out
Myelinated axons increase speed of action potential.
Animation 2
Animation
Moving Impulse Along Neurona. Resting potential = -70mvb. Depolarization – reversal of
charges1. Na+ gates open and enters cell2. Potential changes to = +35mv
c. Repolarization – reversal of charges to restore resting pot.1. Na+ gates shut2. K+ gates open and leaves cell
d. Hyperpolarization – 1. Too much K+ moved out than was necessary
e. Refractory period – Fixing overcorrection with active transport. Cannot respond to another stimulus.1. Na/K+ pumps move Na+ out and K+ into cell to re-establish polarity
Animation 2
Animation 3
Synapse• Neurotransmitter
s: communication chemicals (50+ types known!)
• Threshold – minimum amount of stimulus needed for depolarization.
• Reuptake transporters recycle neurotransmitters.
Animation Neuron Communication Video
Neurotransmitters• Excitatory – Increases activity of
postsynaptic neuron.
• Inhibitory – Decreases activity of postsynaptic neuron.
More than one type of neurotransmitter can be released by a single neuron and one neuron can have synapses with several different neurons (convergence and divergence), thus, a single neuron can have receptors for many different types of neurotransmitters.
Common Neurotransmitters• Acetylcholine – Excitatory, skeletal muscle
contraction• Norepinephrine – Excitatory; increase HR.• GABA – Inhibitory, reduces anxiety.• Glutamate – Excitatory, involved in learning
and memory.• Endorphins – Inhibitory, natural opiates.• Serotonin – Involved in regulating
attention, emotions, mood disorders• Dopamine – Contributes in voluntary
movement; feel good emotions, Parkinson’s
Drug Effects on Neurotransmitters
• Pain killers – stop the release or block receptor sites or increase threshold.
• Caffeine – lowers threshold at synapses so neurons are more easily excited.
• Zoloft/Prozac/Paxil– keeps serotonin in the synapse longer; anti-depressants
• Dilantin – increasing effectiveness of ion transport; treats seizures
Go to Mouse Party for the affects of illegal drugs on neurotransmitters…
The BrainSections 9.11 and 9.13
* Contains approximately 100
Billion neurons
* Weighs about 3 pounds
Meninges: The Coverings
• Three Layers:1. Dura mater – outermost, tough, white2. Arachnoid mater – middle, web-like, CSF in subarachnoid space3. Pia mater – innermost, very thin on top of brain tissue
Meningitis: Inflammation of the meninges and CSF; typical causes are bacteria or virus; spinal tap needed to diagnose
Get your vaccination before college!
Cerebrospinal Fluid - CSF• Clear and colorless• Circulates within the
ventricles and sub-arachnoid space throughout CNS.
• Produced by the ependymal glial cells.
• Provides cushioning, optimum chemical environment, and nutrient/waste exchange.
• Hydrocephalus – too much CSF, blockage usually the cause, can cause neuron damage.
Hydrocephalus
Major Brain Structures• Cerebrum- Divided into 4
lobes:(frontal, parietal, occipital, temporal)
• Diencephalon:(thalamus, hypothalamus,
epithalamus)
• Brain Stem:(midbrain, pons, medulla oblongata)
• Cerebellum
Cerebrum
• Two cerebral hemispheres• Longitudinal fissure separates hemispheres. • Surface area increased with Gyri (ridges) and
Sulci (creases) or Fissures (deep grooves).• Connected by the Corpus Callosum• Function: Intelligence, memory, learning• Cerebral cortex – gray matter, outermost, all
conscious thinking occurs here• Olfactory bulb – sense of smell
Parieto-occipital sulcus
Functions of the Cerebrum
Prefrontal Cortex Problem Solving, Emotion, Complex Thought
Motor Association Cortex Coordination of complex movement
Primary Motor Cortex Initiation of voluntary movement
Primary Somatosensory Cortex Receives tactile information from the body
Sensory Association Area Processing of multi-sensory information
Visual Association Area Complex processing of visual information
Visual Cortex Detection of simple visual stimuli
Wernicke's Area Language comprehension
Auditory Association Area Complex processing of auditory information
Auditory Cortex Detection of sound quality (loudness, tone)
Broca's Area Speech production and articulation
Let’s Probe the brain! – find out how scientists found out where primary motor functions are.
Comparing Human, Dog and Rat Brains
DiencephalonMain structures: 1. Thalamus – main relay
station for sensory impulses (except smell) to the cerebral cortex.
2. Hypothalamus – regulates visceral movement (BP, GI tract, HR), body temperature, water and electrolytes, hunger, thirst, stimulate pituitary, maintains sleep and wake patterns.
3. Epithalamus – contains the Pineal gland which regulates biological clock.
Brain StemThree sections:1. Midbrain – visual and
auditory reflex centers, main motor pathway
2. Pons – “bridge”, relays impulses between: a. medulla/cerebrum b. cerebrum/cerebellum
3. Medulla Oblongata –regulates heart rate, blood pressure, respiration, coughing, sneezing, vomiting, swallowing
Cerebellum
• 2nd largest part of brain• Controls muscular
coordination• Maintains posture• Allows for smooth,
refined movements• Involuntary once
learned
Brain Disorders and Diseases
Common Brain Injuries
• Concussion – abrupt, but temporary loss of consciousness from a blow to the head.
Symptoms: headache, confusion, memory loss, lack of concentration
• Contusion – bruising of the brain due to trauma, leaking capillaries, commonly follows a concussion. Pia mater torn.Signs: Immediate loss of consciousness, loss of reflexes, decreased
blood pressure, cessation of respiration.
• Laceration – tear of the brain, large vessel rupture, cerebral hematoma, increased intercranial pressure.
Brain Tumors
Brain Aneurism
Cerebral thrombosis video
Strokes
Injury Effects
Phineas Gage
Man who survived a terrible brain injury in the 1800’s. First opportunity for scientists to study the frontal lobe and limbic system connection. Limbic system is the emotional region and frontal keeps the limbic region in control.Injury re-enactment video
cdnuolt blveiee taht I cluod aulaclty uesdnatnrd waht I was rdanieg. The phaonmneal pweor of the hmuan mnid, aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteer be in the rghit pclae. The rset can be a taotl mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Amzanig huh? yaeh and yuo Iawlyas tghuhot slpeling was ipmorantt!
CAN YOU READ THIS?
The Spinal Cord
Conus medullaris
Cauda equina
Spinal Cord• Functions – to conduct nerve impulses and
serve as the center of spinal reflexes.• Anatomy of the spinal cord:
1. Ascending tracts – from sensory to brain
2. Descending tracts – from brain to motor
3. Composed of gray and white matter.4. Central canal contains the CSF.
5. Conus medullaris – end of cord at L16. Cauda Equina – cord fans out into nerves.
Nerve structure of the arm
31 pairs of spinal nerves
– Cervical– Thoracic– Lumbar
– Sacral
(What body regions do these nerves connect with?)
Dermatome Map
Check skin sensations to see what nerve has been damaged.
Paraplegia – injury below T1
Quadriplegia – injury above T1
Cross-Section of Spinal Cord
Afferent impulses travel through dorsal root to cord.
Efferent impulses travel through ventral root to effector.
Cross-section of Spinal Cord
Orientation of grey and white matter is opposite of the brain.
Grey matter = cell bodies
White matter = myelinated axons
• Rapid, automatic responses to specific stimuli.• Their purpose is to preserve homeostasis.• Little variability in the responses.• Only a few neurons are needed.• “Wiring” of a single reflex = “Reflex Arc”• Testing somatic reflexes can be used for
diagnostic purposes.• Examples: swallowing, sneezing, vomiting,
and knee jerk.
Reflexes
Reflex Classification
Stretch Reflex: “Patellar reflex”
Muscle spindles = sensory receptors involved in stretch reflexes
Innate Reflex: “Withdrawal reflex”
Lumbar Puncture or Spinal Tap
Needle inserted between 3rd and
4th lumbar vertebrae.
Epidural
Epidural given outside of the dura mater.
Herniated Vertebral Disc
Sciatica
• Compression and/or irritation of a sciatic nerve root or the sciatic nerve itself.
• Symptoms: pain or numbness in back, buttock, and/or parts of the leg and foot
Spinal Tumor and Herniated Disc
Peripheral Nervous System
Sections 14 and 15
READ TONIGHT!!!
Peripheral Nervous System
PNS
Sensory(Afferent)
Motor(Efferent)
SomaticSomatic
(Voluntary)Autonomic
(Involuntary)
Skeletal Muscles Sympathetic Parasympathetic
Visceral
Skin and special senses
General Info
All nerves that branch off the CNS and connect to other body parts.
• Cranial nerves – 12 pairs
• Spinal nerves – 31 pairs
Functions:1. To receive stimulus input and send to
CNS. 2. To relay the response from the CNS to
the appropriate effector organ.
Nerve Anatomy
Afferent or Sensory Nerves
1. Picks up stimuli from:
a. internal environment – visceral nerves
b. external environment – somatic nerves
2. Sends to CNS for interpretation
3. Typically unipolar or bipolar neurons
Somatic nervous system
– All voluntary or conscious activities
– Nerves connect to skeletal muscles
– Pathways have one motor neuron to muscle cells.
– Neurotransmitter: Acetylcholine
Autonomic nervous system
- All involuntary or unconscious activities.- Maintains internal environment- Nerves connect to cardiac, smooth
muscle or glands- Pathways have two neurons synapsing at
a ganglia before effector.- Neurotransmitters: Acetylcholine or
norepinephrine- Two divisions counterbalance each other:
Sympathetic and Parasympathetic
Comparing Motor Neurons
Sympathetic• prepares for energy-expenditure,
excitement or stressful situations• "fight" or take "flight“.• Nerve fibers originate from the thoracic
and lumbar regions of spinal cord.• Short Pre and Long postganglionic fibers
Parasympathetic
• Stimulated during calm and relaxing situations
• "rest" and "digest" .• Nerve fibers originate from the brain and
sacral region.• Long preganglionic fibers and short post
Which pathway is responsible here?
Sympathetic or Parasympathetic
Division of the ANS are distinguished by:
1. Unique origin sites
a. Sacrocranial vs. Thoracolumbar
2. Different lengths of their fibers
a. Preganglionic (long – Para, short – S)
b. Postganglionic (long – S, short – Para)
3. Location of their ganglia
a. P – close to effector
b. S – close to spinal cord
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