0-1 Chapter 14 Brain and Cranial Nerves Flashcards Preview

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Flashcards in 0-1 Chapter 14 Brain and Cranial Nerves Deck (185):
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rostral

toward the forehead

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caudal

toward the spinal cord

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three major portions of the brain

cerebrum, cerebellum, brainstem

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cerebrum

cerebrum is 83% of brain volume; cerebral hemispheres, gyri and sulci, longitudinal fissure, corpus callosum

5

cerebellum

cerebellum contains 50% of the neurons; second largest brain region, located in posterior cranial fossa

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brainstem

brainstem the portion of the brain that remains if the cerebrum and cerebellum are removed; diencephalon, midbrain, pons, and medulla oblongata

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Cerebrum

longitudinal fissure

deep groove that separates cerebral hemispheres

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Cerebrum
gyri

thick folds

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Cerebrum
sulci

shallow grooves

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Cerebrum
corpus callosum

thick nerve bundle at bottom of longitudinal fissure that connects hemispheres

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Cerebellum

about 10% of brain volume
•contains over 50% of brain neurons
•marked by gyri, sulci, and fissures

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Cerebellum

occupies

occupies posterior cranial fossa

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brainstem

what remains of the brain if the cerebrum and cerebellum are removed

14

major components


–midbrain
–pons
–medulla oblongata

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gray matter

the seat of neuron cell bodies, dendrites, and synapses
–dull white color when fresh, due to little myelin
–forms surface layer, cortex, over cerebrum and cerebellum
–forms nuclei deep within brain

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white matter

bundles of axons
–lies deep to cortical gray matter, opposite relationship in the spinal cord
–pearly white color from myelin around nerve fibers
–composed of tracts, bundles of axons, that connect one part of the brain to another, and to the spinal cord

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meninges

three connective tissue membranes that envelop the brain
–lies between the nervous tissue and bone
–as in spinal cord, they are the dura mater, arachnoid mater, and the pia mater
–protect the brain and provide structural framework for its arteries and veins

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dura mater

in cranial cavity -2 layers

•outer periosteal
•inner meningeal

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outer periosteal

equivalent to periosteum of cranial bones

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inner meningeal

continues into vertebral canal and forms dural sac around spinal cord

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cranial dura mater is pressed closely against

cranial bones
•no epidural space
•not attached to bone except: around foramen magnum, sella turcica, the cristagalli, and sutures of the skull
•layers separated by dural sinuses –collect blood circulating through brain

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dura mater

folds inward to extend between parts of the brain

•falx cerebri
•tentorium cerebelli
•falx cerebelli

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falx cerebri

separates the two cerebral hemispheres

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tentorium cerebelli

separates cerebrum from cerebellum

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falx cerebelli

separates the right and left halves of cerebellum

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arachnoid mater

–transparent membrane over brain surface
–subarachnoid space separates it from pia mater below
–subdural space separates it from dura mater above in some places

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pia mater

–very thin membrane that follows contours of brain, even dipping into sulci
–not usually visible without a microscope

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meningitis

inflammation of the meninges
–serious disease of infancy & childhood
–especially between 3 months and 2 years of age
•caused by bacterial and virus invasion of the CNS by way of the nose and throat
•pia mater and arachnoid are most often affected

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bacterial meningitis

can cause swelling the brain, enlarging the ventricles, and hemorrhage

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ventricles

four internal chambers within the brain

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choroid plexus

spongy mass of blood capillaries on the floor of each ventricle

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ependyma

neuroglia that lines the ventricles and covers choroid plexus
–produces cerebrospinal fluid

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cerebrospinal fluid (CSF)

clear, colorless liquid that fills the ventricles and canals of CNS
–bathes its external surface

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CSF continually flows through and around the CNS

–driven by its own pressure, beating of ependymal cilia, and pulsations of the brain produced by each heartbeat

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CSF is reabsorbed by

arachnoid villi

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arachnoid villi

–cauliflower-shaped extension of the arachnoid meninx
–protrudes through dura mater
–into superior sagittal sinus
–CSF penetrates the walls of the villi and mixes with the blood in the sinus

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Functions of CSF

buoyancy
protection

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buoyancy

–allows brain to attain considerable size without being impaired by its own weight
–if it rested heavily on floor of cranium, the pressure would kill the nervous tissue

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protection

–protects the brain from striking the cranium when the head is jolted
–shaken child syndrome and concussions do occur from severe jolting

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chemical stability

–flow of CSF rinses away metabolic wastes from nervous tissue and homeostatically regulates its chemical environment

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Blood Supply to the Brain

brain is only 2% of the adult body weight, and receives 15% of the blood
–750 mL/min

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brain barrier system

strictly regulates what substances can get from the bloodstream into the tissue fluid of the brain
•two points of entry must be guarded:
–blood capillaries throughout the brain tissue
–capillaries of the choroid plexus

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blood-brain barrier

protects blood capillaries throughout brain tissue
–consists of tight junctions between endothelial cells that form the capillary walls
–astrocytes reach out and contact capillaries with their perivascular feet

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endothelial cells can

exclude harmful substances from passing to the brain tissue while allowing necessary ones to pass

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blood-CSF barrier

protects the brain at the choroid plexus
–form tight junctions between the ependymal cells
–tight junctions are absent from ependymal cells elsewhere
•important to allow exchange between brain tissue and CSF

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blood barrier system is highly permeable to

water, glucose, and lipid-soluble substances such as oxygen, carbon dioxide, alcohol, caffeine, nicotine, and anesthetics

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slightly permeable

to sodium, potassium, chloride, and the waste products urea and creatinine

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circumventricular organs

(CVOs) –places in the third and fourth ventricles where the barrier is absent
•blood has direct access to the brain

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Hindbrain

Medulla Oblongata

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Medulla Oblongata

•begins at foramen magnum of the skull
•extends for about 3 cm rostrally and ends at a groove between the medulla and pons
•slightly wider than spinal cord

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Medulla Oblongata

nerves & Cranial nerves

•all nerve fibers connecting the brain to the spinal cord pass through the medulla
•four pairs of cranial nerves begin or end in medulla -IX, X, XI, XII

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pyramids

pair of external ridges on anterior surface
contain descending fibers called corticospinal tracts
–carry motor signals to skeletal muscles

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Medulla Oblongata

centers

•cardiac center
•vasomotor center
•respiratory centers
•reflex centers

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cardiac center

–adjusts rate and force of heart

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vasomotor center

–adjusts blood vessel diameter

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respiratory centers

–control rate and depth of breathing

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reflex centers

for coughing, sneezing, gagging, swallowing, vomiting, salivation, sweating, movements of tongue and head

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inferior olivary nucleus

relay center for signals to cerebellum

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reticular formation

loose network of nuclei extending throughout the medulla, pons and midbrain
–contains cardiac, vasomotor & respiratory centers

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metencephalon

develops into the pons and cerebellum

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pons

anterior bulge in brainstem, rostral to medulla

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cerebral peduncles

connect cerebellum to pons and midbrain

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Pons

•ascending sensory tracts
•descending motor tracts
•pathways in and out of cerebellum

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Pons
cranial nerves

V, VI, VII, and VIII

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sensory roles

hearing, equilibrium, taste, facial sensations

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motor roles

eye movement, facial expressions, chewing, swallowing, urination, and secretion of saliva and tears

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reticular formation

reticular formation in pons contains additional nuclei concerned with:
–sleep, respiration, and posture

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midbrain

–short segment of brainstem that connects the hindbrain to the forebrain
–contains cerebral aqueduct
–contains continuations of the medial lemniscus and reticular formation

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midbrain

cranial nerves

contains the motor nuclei of two cranial nerves that control eye movements –CN III (oculomotor) and CN IV (trochlear)

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tectum

roof-like part of the midbrain posterior to cerebral aqueduct

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cerebral peduncles

two stalks that anchor the cerebrum to the brainstem anterior to the cerebral aqueduct

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cerebral peduncles
–each consists of three main components

tegmentum, substantia nigra, and cerebral crus

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tegmentum

•dominated by the red nucleus
•connections go to and from cerebellum

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substantia nigra

•dark gray to black nucleus pigmented with melanin
•motor center that relays inhibitory signals to thalamus & basal nuclei preventing unwanted body movement

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cerebral crus

•bundle of nerve fibers that connect the cerebrum to the pons
•carries corticospinal tracts

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reticular formation

loosely organized web of gray matter that runs vertically through all levels of the brainstem
•clusters of gray matter scattered throughout pons, midbrain and medulla
•occupies space between white fiber tracts and brainstem nuclei
•has connections with many areas of cerebrum

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Functions of Reticular Formation Networks

somatic motor control
cardiovascular control
pain modulation*****************
sleep and consciousness
habituation

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gaze center

allow eyes to track and fixate on objects

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Cerebellum

the largest part of the hindbrain and the second largest part of the brain as a whole
•consists of right and left cerebellar hemispheres connected by vermis
•contains more than half of all brain neurons, about 100 billion

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cerebellar peduncles

three pairs of stalks that connect the cerebellum to the brainstem

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Cerebellar Functions

•monitors muscle contractions and aids in motor coordination
•evaluation of sensory input
•timekeeping center
•hearing
•planning and scheduling tasks

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forebrain consists of

–the diencephalon
–the telencephalon

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Diencephalon: Thalamus

the “gateway to the cerebral cortex” –nearly all input to the cerebrum passes by way of synapses in the thalamic nuclei, filters information on its way to cerebral cortex
–plays key role in motor control by relaying signals from cerebellum to cerebrum and providing feedback loops between the cerebral cortex and the basal nuclei
–involved in the memory and emotional functions of the limbic system

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hypothalamus

major control center of autonomic nervous system and endocrine system
–plays essential roll in homeostatic regulation of all body systems

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functions of hypothalamic nuclei

–hormone secretion
–autonomic effects
–thermoregulation
–food and water intake
–produce sensations of hunger and satiety
–rhythm of sleep and waking
–memory
–emotional behavior

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epithalamus

very small mass of tissue composed of:
–pineal gland –endocrine gland
–habenula–relay from the limbic system to the midbrain

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Telencephalon

Cerebrum

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cerebrum

largest and most conspicuous part of the human brain
–seat of sensory perception, memory, thought, judgment, and voluntary motor actions

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frontal lobe

–voluntary motor functions
–motivation, foresight, planning, memory, mood, emotion, social judgment, and aggression

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parietal lobe

–receives and integrates general sensory information, taste and some visual processing

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occipital lobe

–primary visual center of brain

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temporal lobe

–areas for hearing, smell, learning, memory, and some aspects of vision and emotion

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insula

–understanding spoken language, taste and sensory information from visceral receptors

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Cerebral White Matter

most of the volume of cerebrum is white matter
–glia and myelinated nerve fibers transmitting signals from one region of the cerebrum to another and between cerebrum and lower brain centers

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three types of tracts

projection tracts, commissural tracts, association tracts

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long association fibers

connect different lobes of a hemisphere to each other

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short association fibers

connect different gyri within a single lobe

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Cerebral Cortex

layer covering the surface of the hemispheres
–only 2 –3 mm thick
–cortex constitutes about 40% of the mass of the brain
–contains 14 –16 billion neurons

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cerebral gray matter found in three places

–cerebral cortex
–basal nuclei
–limbic system

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neural integration

is carried out in the gray matter of the cerebrum

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Cerebral Cortex contains two principal types of neurons

stellate cells
pyramidal cells. -only neurons that leave the cortex and connect with other parts of the CNS

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basal nuclei

Involved in motor control

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limbic system

Creates emotions

cingulate gyrus –

– hippocampus

– amygdala

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higher brain functions

sleep, memory, cognition, emotion, sensation, motor control, and language

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electroencephalogram

(EEG) –monitors surface electrical activity of the brain waves

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brain waves

rhythmic voltage changes resulting from synchronized postsynaptic potentials at the superficial layer of the cerebral cortex

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alpha waves 8 –13 Hz

awake and resting with eyes closed and mind wandering
–suppressed when eyes open or performing a mental task

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beta waves 14 –30 Hz

–eyes open and performing mental tasks
–accentuated during mental activity and sensory stimulation

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theta waves 4 –7 Hz

–drowsy or sleeping adults
–if awake and under emotional stress

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delta waves high amplitude, less than 3.5 Hz

–deep sleep in adults

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sleep occurs in cycles called

circadian rhythms
–events that reoccur at intervals of about 24 hours

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sleep

temporary state of unconsciousness from which one can awaken when stimulated

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sleep paralysis

inhibition of muscular activity

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coma or hibernation

states of prolonged unconsciousness where individuals cannot be aroused from those states by sensory stimulation

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sleep spindles

high spikes resulting from interactions between neurons
of the thalamus and cerebral cortex

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slow-wave-sleep(SWS)

EEG dominated by low-frequency, high amplitude delta waves

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rhythm of sleep

controlled by a complex interaction between the cerebral cortex, thalamus, hypothalamus, and reticular formation

HYPOTHALAMUS

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suprachiasmatic nucleus (SCN)

In hypothalamus

another important control center for sleep

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Stage 1

feel drowsy, close our eyes, begin to relax

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Stage 2

pass into light sleep

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Stage 3

moderate to deep sleep

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Stage 4

called slow-wave-sleep(SWS) –EEG dominated by low-frequency, high amplitude delta waves

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cognition

the range of mental processes by which we acquire and use knowledge

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association areas of cerebral cortex

constitutes about 75% of all brain tissue

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parietal lobe association area

perceiving stimuli

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temporal lobe association area

identifying stimuli

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frontal lobe association area

planning our responses and personality

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learning

acquiring new information

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memory

information storage and retrieval

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forgetting

eliminating trivial information; as important as remembering

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amnesia

defects in declarative memory –inability to describe past events

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– anterograde amnesia

unable to store new information

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– retrograde amnesia

– cannot recall things they knew before the injury

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procedural memory

ability to tie your shoes

134

hippocampus

important memory-forming center
Does not store memories

135

amygdala

emotional memory

136

prefrontal cortex

seat of judgment, intent, and control over expression of emotions

137

primary sensory cortex

sites where sensory input is first received and one becomes conscious of the stimulus

138

special senses

limited to the head and employ relatively complex sense organs

139

special senses

5

vision
•hearing
•equilibrium
•taste
smell

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The General Senses

general (somesthetic, somatosensory, or somatic) senses –distributed over the entire body and employ relatively simple receptors

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sensory homunculus

diagram of the primary somesthetic cortex which resembles an upside-down sensory map of the contralateral side of the body
•shows receptors in the lower limbs projecting to the superior and medial parts of the gyrus

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somatotopy

the point-to-point correspondence between an area of the body and an area of the CNS

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Motor Control

the intention to contract a muscle begins in motor association (premotor) area of frontal lobes

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upper motor neurons

pyramidal cells of the precentral gyrus are called upper motor neurons

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lower motor neurons

in the brainstem or spinal cord, the fibers from upper motor neurons synapse with lower motor neurons whose axons innervate the skeletal muscles

146

Highly Important in motor control

basal nuclei
cerebellum

147

Language

language include several abilities: reading, writing, speaking, and understanding words assigned to different regions of the cerebral cortex

148

Wernicke area

Understanding and planning
Plan sent to Broca for execution
permits recognition of spoken and written language and creates plan of speech

149

Broca area

Plan for the muscles movement

generates motor program for the muscles of the larynx, tongue, cheeks and lips

150

aphasia

any language deficit from lesions in same hemisphere (usually left) containing the Wernicke and Broca areas

151

anomic aphasia

can speak normally and understand speech, but cannot identify written words or pictures

152

cerebral lateralization

the difference in the structure and function of the cerebral hemispheres

153

left hemisphere

categorical hemisphere
–specialized for spoken and written language
–sequential and analytical reasoning (math and science)
–breaks information into fragments and analyzes it in a linear way

154

right hemisphere

representational hemisphere
–perceives information in a more integrated holistic way
–seat of imagination and insight
–musical and artistic skill
–perception of patterns and spatial relationships
–comparison of sights, sounds, smells, and taste

155

Cranial Nerves

–most of the input and output travels by way of the spinal cord
–12 pairs of cranial nerves arise from the base of the brain
–exit the cranium through foramina
–lead to muscles and sense organs located mainly in the head and neck

156

Cranial Nerve Pathways

most cranial nerves carry fibers between brainstem and ipsilateral receptors and effectors

157

most motor fibers of the cranial nerves begin

in nuclei of brainstem and lead to glands and muscles

158

sensory fibers begin in receptors located mainly in

head and neck and lead mainly to the brainstem

159

Cranial Nerve Classification

some cranial nerves are classified as motor, some sensory, others mixed

160

sensory

(I, II, and VIII)

161

motor

(III, IV, VI, XI, and XII)
•stimulate muscle but also contain fibers of proprioception

162

mixed

(V, VII, IX, X)
•sensory functions may be quite unrelated to their motor function
–facial nerve (VII) has sensory role in taste and motor role in facial expression

163

I

Olfactory Nerve
sense of smell
Sensory
Cribiform foramina
Olfactory mucosa to olfactory bulbs to inferior medial of temporal lobe
Ipsilateral

164

II

Optic Nerve
provides vision
Sensory
Optic foramen
Retina to thalamus and occipital lobe
Hemidesicates

165

III

Oculomotor Nerve
Motor
Eye movements
Midbrain to eye muscles and to the levator palpebrae superious (only one not innervated by facial nerve )
Superior orbital fissure
Ipsilateral

166

IV

Trochlear Nerve
eye movement (superior oblique muscle)
Motor
Midbrain to superior oblique muscle of the eye
Superior orbital fissure
CONTRALATERAL

167

V

Trigeminal Nerve - mixed
•largest of the cranial nerves
•most important sensory nerve of the face
•forks into three divisions:
–ophthalmic division (V1) –sensory
–maxillary division (V2) –sensory
–mandibular division (V3) -mixed

168

VI

Abducens Nerve
Motor
Pons to lateral rectus muscle
Superior orbital fissure
provides eye movement (lateral rectus m.)
Ipsilateral

169

VII

Facial Nerve
Mixed
Pons to facial muscles
Style mastoid foramen
Ipsilateral
Main nerve for facial expression
Carrying taste from anterior 2/3 of tongue

170

VIII

Vestibulocochlear Nerve
Sensory
Ipsilateral
Inner ear to pons
Internal acoustic meatus
hearing and equilibrium

171

IX

Glossopharyngeal Nerve
Mixed
Medula to
Jugular foramen


swallowing, salivation, gagging, control of BP and respiration
•sensations from posterior 1/3 of tongue

172

X

Vagus Nerve
Mixed
Attaches to medula down to large intestine
Jugular foramen

Most important parasympathetic
•most extensive distribution of any cranial nerve

Carries taste from cheeks,
•major role in the control of cardiac, pulmonary, digestive, and urinary function
•swallowing, speech, regulation of viscera

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XI

Accessory Nerve
Motor
Medula to trapezius, SCM and paletioglossis
Jugular foramen
Ipsilateral

swallowing, head, neck and shoulder movement

174

XII

Hypoglossal Nerve
Motor
Medula to extrinsic muscles of the tongue
Hypoglossal canal


tongue movements for speech, food manipulation and swallowing

175

Trigeminal neuralgia

(tic douloureux)
–recurring episodes of intense stabbing pain in trigeminal nerve area (near mouth or nose)
–pain triggered by touch, drinking, washing face

176

Bell’s palsy

degenerative disorder of facial nerve causes paralysis of facial muscles on one side

177

functional magnetic resonance imaging (fMRI)

looks at increase in blood flow to an area (additional glucose is needed in active area)

178

positron emission tomography (PET) and MRIvisualize

increases in blood flow when brain areas are active
–injection of radioactively labeled glucose
•busy areas of brain “light up”

179

Cranial nerves

Acromions

Names and functions

Oh once one takes the anatomy final very good vacations are heavenly - names


Some say marry money but my brother says bad business marry money - functions

180

nonfluent (Broca) aphasia

nonfluent (Broca) aphasia

– lesion in Broca area

– slow speech, difficulty in choosing words, using words that only approximate the correct word

181



• fluent (Wernicke) aphasia



– lesion in Wernicke area

– speech normal and excessive, but uses jargon that makes little sense

– cannot comprehend written and spoken words

• anomic aphasia

– can speak normally and understand speech, but cannot identify written words or pictures

182

Cranial V1

.

183

Cranial V2

.

184

Cranial V3

.