Chapter 14 brain and cranial nerves anatomy and physiology 1

98%

human brain contains how much neural tissue

3 pounds

how much does the average brain weigh

dura mater

inner fibrous layer(meningeal)

outer fibrous layer(endosteal) fused to periosteum

venous sinuses between 2 layers

arachnoid mater

covers brain, contacts epithelial layer of dura mater

subarachnoid space

between arachnoid matter and pia mater/CSF

pia mater

attached to brain surface by astrocytes

cerebrospinal fluid(CSF)

surrounds all exposed surfaces of CNS

-interchanges with interstitial fluid of brain

Functions of cerebrospinal fluid

1. cushions delicate neural surfaces

2. support brain(floats brain)

3. transports nutrients, chemical messengers, and waste products

choroid plexus

specialized ependymal cells and capillaries

secrete CSF into ventricles(recycles 150 mL every 8 hours)

lateral ventricles(2)

each cerebral hemisphere contains 1 large lateral ventricle

third ventricle

ventricle of diencephalon

connects with 4th ventricle

cerebral(mesencephalic) aqueduct

carries CSF from 3rd to 4th ventricle

fourth ventricle

extends into medulla oblongata

becomes continuous with central canal of spinal cord

central canal

brings CSF to spinal cord

blood supply to brain

IN

internal carotid arteries and vertebral arteries

blood supply to brain

OUT

internal jugular veins

stroke or cerebrovascular accident(CVA)

shuts off blood to portion of the brain, neurons die

blood brain barrier

isolates CNS neural tissue from general circulation

formed by tight junctions

let lipid-soluble compounds go through

astrocytes

they regulate it (release chemicals that control permeability)

what works with the blood brain barrier?

medulla oblongata

allows brain and spinal cord to communicate

-coordinates complex autonomic reflexes(subconscious)

• heart-rate

• blood pressure

• digestion

-control visceral functions

autonomic nuclei(reticular formation) function of medulla oblongata

controls visceral activities

cardiac center and vasomotor center function of medulla oblongata

adjust HR, heart contractions, and blood flow

respiratory rhythmicity center function of medulla oblongata

regulates respiratory rates

relay stations

for sensory and motor pathways

nucleus gracilis and nucleus cuneatus(relay station)

somatic sensory to the thalamus

-touch

solitary nucleus(relay stations)

visceral sensory

olivary nucleus(relay station)

somatic motor

VIII, IX, X, XI, XII

8, 9, 10, 11, 12

cranial nerves with sensory and motor

pons

links cerebellum with mesencephalon, diecenphalon, cerebrum, spinal

functions of pons

1. respiration-apneustic center and pneumotaxic center modify respiratory center activity(breathing)

2. sensory and motor nuclei of cranial nerves- V(5), VI(6), VII(7), VII(8)

3. nuclei and tracts-process and relay information to and from cerebellum

corpora quadrigemina- midbrain(mesencephalon)

2 pairs of sensory nuclei

superior colliculus midbrain(mesencephalon)

visual

inferior colliculus midbrain(mesencephalon)

auditory

cerebral peduncles midbrain(mesencephalon)

contain descending fibers(motor) to cerebellum and ascending fibers(sensory) to thalamus

tegmentum- red nucleus midbrain(mesencephalon)

many blood vessels, subconscious muscle tone

tegmentum-substantia nigra

midbrain(mesencephalon)

pigmented gray matter, regulates basal nuclei, dopamine

cerebellum

an autonomic processing center

functions of cerebellum

1. adjusting the postural muscles

2. programming and fine tuning movements

folia(cerebellum)

surface of cerebellum

highly folded neural cortex

cerebellar hemispheres (cerebellum)

left and right

separated at midline

purkinje cells(cerebellum)

large, branched cells

found in cerebella cortex(superficial layer)

arbor vitae(cerebellum)

highly branched, internal white matter of cerebellum

cerebellar nucleus(cerebellum)

embedded in arbor vitae, relay information to Purkinje cells

superior cerebellar peduncles(cerebellum)

to midbrain and cerebrum

middle cerebellar peduncles(cerebellum)

to pons

inferior cerebellar peduncles (cerebellum)

medulla oblongata and spinal cord

ataxia(cerebellum)

disturbance in muscle coordination

• damage from trauma/stroke

• intoxication

diencephalon

integrates sensory information and motor commands

epithalamus

pineal gland→melatonin

thalamus

filters ascending sensory information for primary sensory cortex

relay information between basal nuclei and cerebral cortex

intermediate mass(thalamus)

projection of gray that extends into 3rd ventricle from each side

• inbetween left and right thalamus

anterior group(function of thalamus)

part of limbic system(emotions)

medial group(function of thalamus)

provides awareness of emotional states

ventral group(function of thalamus)

relays sensory information

pulvinar-POSTERIOR GROUP

(function of thalamus)

sensory

lateral geniculate-POSTERIOR GROUP

(function of thalamus)

visual

medial geniculate-POSTERIOR GROUP

(function of thalamus)

auditory

mamillary bodies(hypothalamus)

process olfactory and other sensory information

control reflex eating movements

infundibulum(hypothalamus)

narrow stalk connects hypothalamus to pituitary gland

pituitary gland(hypothalamus)

major endocrine gland

• connected to hypothalamus

• interfaces neurons and endocrine systems

functions of hypothalamus

1. Provides subconscious control of skeletal
muscle
2.Controls autonomic function
3.Coordinates activities of nervous and
endocrine systems
4.Secretes hormones
- antidiuretic hormone (ADH)
-oxytocin (OT)
5. Produces emotions and behavioral drives

- the feeding center (hunger)
-the thirst center (thirst)
6.Coordinates voluntary and autonomic functions
7.Regulates body temperature
8.Controls circadian rhythms (day–night cycles)

cerebrum

largest region of the brain, complex movements, conscious thoughts, intellectual functionals

cerebral cortex functions

1. each cerebral hemisphere receives sensory info from, and sends motor commands to the opposite side of body

2. 2 hemispheres have different functions although their structures are alike

3. specific functions and specific region is not precise

longitudinal fissure

separates left and right cerebral hemispheres

cerebral hemisphere

left and right sides of the brain

gyri

folds to increase surface area

sulcus

grooves in between gyri

corpus callosum

connects left and right hemispheres

lobes

under corresponding skull bones

frontal lobe

parietal lobe

temporal lobe

occipital lobe

insula

lies medial to lateral sulcus

central sulcus

divides frontal lobe from parietal lobe

precentral gyrus

gyrus just in front of central sulcus

FRONTAL LOBE

postcentral gyrus

gyrus just behind the central sulcus

PARIETAL LOBE

lateral sulcus

separates frontal lobe from temporal lobe

parieto-occipital sulcus

separates parietal lobe from occipital lobe

white matter

inferior portion(inside) of the cerebrum

association fibers(white matter)

interconnect areas in a cerebral hemisphere

• connects 1 hemisphere

arcuate fibers

part of association fibers

short, connect gyrus to gyrus

• forms arches

longitudinal fasciculi

part of association fibers

connects from frontal lobe to other lobes

commissural fibers(white matter)

cross over fibers(left and right)

corpus callosum

part of commissural fibers

links left and right cerebral hemispheres

• VERY ACTIVE

anterior commissure

part of commissural fibers

links left and right cerebral hemispheres

projection fibers(white matter)

link cerebral cortex with diencephalons, cerebellum, stem and cord

internal capsule

part of projection fibers

entire collection of projection fibers(ascending and descending)

basal ganglia(nuclei)

gray matter under lateral ventricles embedded in white matter of cerebrum

functions of basal ganglia(nuclei)

-processing sensory info and issues motor commands outside of conscious awareness

-subconscious control of skeletal muscle tone

-coordination of learned movement patterns

caudate nucleus

follows curve of lateral ventricle

amygdaloid body

interfaces limbic system with cerebrum, links emotions with memories

lentiform nucleus contains

putaman and globus pallidus

putaman

lateral

globus pallidus

medial

limbic system

lies along border of diencephalons and cerebrum(wants and motivations)

limbic system functions

-establish emotional states

-links conscious functions of the cerebral cortex with unconscious autonomic functions(touch)

-facilitates memory storage and retrieval(emotions)

cingulate gyrus(limbic lobe)

sits superior to corpus callosum

hippocampus

learning and long term memory

tracts inside dentate and parahippocampus

dentate and parahippocampus gyrus

form the posterior and inferior portions of limbic lobe

fornix

tract that connects hippocampus to hypothalamus

precentral gyrus

primary motor cortex

• surface of precentral gyrus

postcentral gyrus

primary sensory cortex

• surface of postcentral gyrus(receives somatic information-touch, pressure, pain, vibration, taste and temp)

visual cortex

occipital lobe

• info from sight receptors