BIOL 105—Lab 9---Gross Anatomy Brain 1 Central Nervous System (CNS) •CNS consists of brain and spinal cord •Surface anatomy includes cerebral hemispheres, cerebellum and brain stem •Brain regions 1. Cerebral hemispheres 2. Diencephalon 3. Brain stem (midbrain, pons, and medulla) 4. Cerebellum Lab 9, BIO 105
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BIOL 105—Lab 9---Gross Anatomy Brain 1 Central Nervous System (CNS) CNS consists of brain and spinal cord Surface anatomy includes cerebral hemispheres,
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BIOL 105—Lab 9---Gross Anatomy Brain 1
Central Nervous System (CNS)•CNS consists of brain and spinal cord•Surface anatomy includes cerebral hemispheres, cerebellum and brain stem
•Brain regions1. Cerebral hemispheres
2. Diencephalon
3. Brain stem (midbrain, pons, and medulla)
4. Cerebellum
Lab 9, BIO 105
BIOL 105—Lab 9---Gross Anatomy Brain 2
Regions and Organization of the CNS
•Spinal cord – Central cavity surrounded by gray matter
• Gray matter will become the processing part of brain
– External white matter composed of myelinated fiber tracts
• White matter is generally protective in nature
BIOL 105—Lab 9---Gross Anatomy Brain 3
• Brain– Cerebral hemispheres and cerebellum
• Outer gray matter called cortex
BIOL 105—Lab 9---Gross Anatomy Brain 4
Ventricles of the Brain•Ventricles filled with cerebrospinal fluid (CSF)•Lined by ependymal cells• Connected to one another and to central canal of spinal
cord and to subarachnoid space– Lateral ventricles--paired, C-shaped – Third ventricle– Fourth ventricle
BIOL 105—Lab 9---Gross Anatomy Brain 5
Cerebral Hemispheres
• 3 basic regions: cortex, white matter and basal nuclei
• Surface markings increase surface area and thus brain activity
– Ridges (gyri), shallow grooves (sulci), and deep grooves (fissures)
– Longitudinal fissure separates two hemispheres
BIOL 105—Lab 9---Gross Anatomy Brain 6
Cerebral Hemispheres•Deep sulci divide the hemispheres into 5 lobes:
Thalamus-- Function•Gateway to cerebral cortex-is the relay station for brain•Essential role in mediating sensation, motor activities, cortical arousal, learning, and memory•Sorts, edits, and relays ascending input
– regulation of emotion and visceral function– help direct motor cortex– Impulses for memory or sensory integration– Impulses from visual and auditory centers
BIOL 105—Lab 9---Gross Anatomy Brain 16
Hypothalamus•Located below the thalamus•Primarily involved in hormone productionInfundibulum—stalk that connects it to pituitary gland
Hypothalamic Function•Controls autonomic nervous system •Controls endocrine system•Physical responses to emotions •Regulates body temperature, hunger, thirst•Regulates sleep-wake cycles•Biological clock
BIOL 105—Lab 9---Gross Anatomy Brain 17
Epithalamus or Pineal gland (body)
•secretes melatonin—helps regulate sleep-wake cycle•Helps regulate body cycles by monitoring length of day via input from optic nerve
Choroid Plexus:•produce CSF at constant rate;
BIOL 105—Lab 9---Gross Anatomy Brain 18
Brain Stem•Consists of 3 regions
– Midbrain
– Pons
– Medulla oblongata
•Controls automatic behaviors necessary for survival
•Provides pathway for nerve tracts connecting higher and lower brain centers
BIOL 105—Lab 9---Gross Anatomy Brain 19
Medulla Oblongata•Most inferior portion of the brain stem; joins spinal cord at foramen magnum
•Cardiovascular center– Cardiac center adjusts force and rate of heart
contraction– Vasomotor center adjusts blood vessel diameter for
blood pressure regulation•Respiratory centers
– Generate respiratory rhythm– Control rate and depth of breathing (with pontine
centers)•Vestibular nuclei (pons and medulla)—mediate responses that maintain equilibrium
Pons•Bulging brainstem area between midbrain and medulla oblongata•helps maintain normal rhythm of breathing
BIOL 105—Lab 9---Gross Anatomy Brain 21
Cerebellum•Subconscious input from cortex, brain stem and sensory receptors to allow smooth, coordinated movements of skeletal muscles•Arbor vitae—treelike pattern of cerebellar white matter•May compare actual with predicted movement sequences and adjust movement accordingly
BIOL 105—Lab 9---Gross Anatomy Brain 2222Nervous System 22
– Meninges--3 protective connective tissue membranes enclose brain and spinal cord• Dura mater is outermost and strongest
layer• Arachnoid mater is middle layer; has
spidery extensions which secure it to innermost layer.
• Pia mater is innermost layer and clings tightly to CNS.
BIOL 105—Lab 9---Gross Anatomy Brain 23
Cerebrospinal Fluid (CSF)•Composition
– Watery solution formed from blood plasma • Contains less protein and different ion
concentrations than plasma– Constant volume
•Functions– Gives buoyancy to CNS structures
• Reduces weight by 97%– Protects CNS from blows and other trauma– Nourishes brain and carries chemical signals
BIOL 105—Lab 9---Gross Anatomy Brain 24
Hydrocephalus•Obstruction blocks CSF circulation or drainage•Fontanelles at skull in newborn allow enlargement of head•Brain damage in adult due to rigid adult skull •Treated by draining with ventricular shunt to abdominal cavity
BIOL 105—Lab 9---Gross Anatomy Brain 25
Blood Brain Barrier•Helps maintain stable environment for brain •Separates neurons from most bloodborne substances•Selective barrier
– Allows nutrients to move by facilitated diffusion– Metabolic wastes, proteins, toxins, most drugs, small
nonessential amino acids, K+ denied– Allows any fat-soluble substances to pass, including
alcohol, nicotine, and anesthetics
•Absent in some areas, e.g., vomiting center and hypothalamus, where necessary to monitor chemical composition of blood
BIOL 105—Lab 9---Gross Anatomy Brain 26
• The BBB in adults consists of a complex cellular system of a highly specialized basal membrane, a large number of pericytes embedded in the basal membrane and astrocytic end feet. Whereas the endothelial cells form the barrier proper, the interaction with adjacent cells seems to be required for the development of the barrier. The brain endothelial cells differ from endothelial cells from other organs in two important ways. First, continuous tight junctions are present between brain endothelial cells. These tight junctions prevent paracellular movement of molecules. Second, there are no detectable transendothelial pathways such as intracellular vesicles. These properties of brain endothelial cells provide a barrier between the blood and
the brain.
BIOL 105—Lab 9---Gross Anatomy Brain 27
LABWORK (includes next slide)
1. Identify and describe the meninges and structures of the brain stem.
2. Identify and describe the cerebellum and structures of the diencephalon.
3. Identify and describe the structures of the cerebrum.
4.State the function of the cranial nerves.
5. Locate the following on diagrams, human brain models, the sheep brain:
On the human brain models, Locate the lobes of the cerebrum, gyri, sulci, and fissures.
BIOL 105—Lab 9---Gross Anatomy Brain 29
Cranial Nerves•Twelve pairs of nerves associated with brain and visible on inferior surface
•Most mixed nerves; two pairs purely sensory
•Most innervate head and neck except the vagus nerve
•Numbered (I through XII) and named from rostral (forward) to caudal
“On old Olympus topmost top, a Finn and German viewed some hops”
"On occasion, our trusty truck acts funny—very good vehicle anyhow"
BIOL 105—Lab 9---Gross Anatomy Brain 30
I: The Olfactory Nerves (sensory)– Sense of smell
II: The Optic Nerves (sensory)•Vision; ability to see
III: The Oculomotor Nerves (motor)– Fibers extend to most extrinsic eye muscles– Controls pupil size, eye movement, iris, and most eye
muscles that move the eye
IV: The Trochlear Nerves (motor)– Primarily controls eye movement
BIOL 105—Lab 9---Gross Anatomy Brain 31
V: The Trigeminal Nerves (mixed motor & sensory)– Largest cranial nerve; fibers extend from pons to face– Three divisions– Conveys sensory impulses from face, head & teeth – Some chewing muscles
VI: The Abducens Nerves (motor)– Controls 1 eye muscle
VII: The Facial Nerves (mixed motor & sensory)– Motor functions: muscles of facial expression,
lacrimal glands and salivary glands, ear sensation
– Sensory function: taste
BIOL 105—Lab 9---Gross Anatomy Brain 32
VIII: The Vestibulocochlear Nerves (mainly sensory; has some motor fibers)
• hearing and equilibrium (balance) receptors
• Formerly called the Auditory Nerve
IX: The Glossopharyngeal Nerves (mixed)• Motor functions – swallowing, some neck
muscles • Sensory functions - taste and general
sensory impulses from pharynx and posterior tongue
BIOL 105—Lab 9---Gross Anatomy Brain 33
X: The Vagus Nerves (motor)•Only cranial nerves that extends (beyond head and neck region) to thoracic & abdominopelvic cavities•Most motor fibers are parasympathetic fibers that help regulate activities of heart, lungs, and abdominal viscera•Sensory fibers carry impulses from thoracic and abdominal viscera, baroreceptors, chemoreceptors, and taste buds of posterior tongue and pharynx
BIOL 105—Lab 9---Gross Anatomy Brain 34
XI: Accessory Nerves (motor)– for neck and head movement (innervate
trapezius and SCM muscle)– Formerly spinal accessory nerve
XII: Hypoglossal Nerves (motor)– Tongue muscles for swallowing and speech
BIOL 105—Lab 9---Gross Anatomy Brain 35
XII: Hypoglossal Nerves (motor)– Tongue muscles for swallowing and speech