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:

– Frontal– Parietal – Temporal – Occipital– Insula--function: associated with visceral

functions, integrates autonomic information

BIOL 105—Lab 9---Gross Anatomy Brain 7

Cerebral HemispheresCerebral cortex—gray matter superficially, white matter internally

•Site of conscious mind; conscious behavior involves the entire cortex; no functional area acts alone

– Enables awareness, sensory perception, voluntary movements, communication, memory storage, understanding

•Each hemisphere concerned with contralateral (opposite) side of body

– Lateralization or specialization of cortical function in each hemisphere

BIOL 105—Lab 9---Gross Anatomy Brain 8

Functional areas1. Motor areas—control voluntary movement

2. Sensory areas—conscious awareness of sensation

3. Association areas—integrate information

BIOL 105—Lab 9---Gross Anatomy Brain 9

Cerebral Cortex--Motor Areas •Frontal lobe--controls voluntary movement

– Primary (somatic) motor cortex – Premotor cortex anterior– Broca's area-speech musculature &

comprehension

BIOL 105—Lab 9---Gross Anatomy Brain 10

• Parietal lobes: somatosensory lobe and some association areas– Receives sensory information from skin and

proprioceptors of skeletal muscle, joints, and tendons

– spatial discrimination; identification of body region being stimulated

• Occipital lobe: visual lobe, includes association areas

BIOL 105—Lab 9---Gross Anatomy Brain 11

• Temporal lobes: auditory lobes and includes association areas– Interprets information including pitch,

loudness, and location– Stores memories of sounds and permits

perception of sound stimulus• Wernicke’s area--can speak, but speech often

incoherent and makes no sense

BIOL 105—Lab 9---Gross Anatomy Brain 12

Networks of neurons that span wide areas of brain BUT work together •Limbic system:

• emotional or affective brain; gives emotional responses to odors

• Example: skunks smell bad•Reticular formation- governs brain arousal

BIOL 105—Lab 9---Gross Anatomy Brain 13

Reticular Formation: governs brain arousal •includes RAS•Reticular activating system (RAS)

– Sends impulses to cerebral cortex to keep conscious and alert

– Filters out repetitive, familiar, or weak stimuli

– Inhibited by hypothalamic sleep centers, alcohol, drugs

– Severe injury results in permanent unconsciousness (coma)

BIOL 105—Lab 9---Gross Anatomy Brain 14

Diencephalon•Consists of 3 structures

– Thalamus– Hypothalamus– Epithalamus (Pineal gland)

•Structures enclose third ventricle

BIOL 105—Lab 9---Gross Anatomy Brain 15

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

BIOL 105—Lab 9---Gross Anatomy Brain 20

Medulla Oblongata

•Additional centers regulate– Vomiting Hiccupping Sneezing– Swallowing Coughing

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:

Ventral view: olfactory bulb, pituitary gland, mammillary body,

trigeminal nerve, pons, cerebellum, medulla oblongata, oculomotor nerve, optic tract, optic chiasma, optic nerve, cerebrum

BIOL 105—Lab 9---Gross Anatomy Brain 28

Midsagittal view: corpus callosum, thalamus, hypothalamus, optic chiasma, pituitary gland, pons, cerebellum, arbor vitae, corpora quadrigemina (midbrain), pineal body, cerebral hemisphere.

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

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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