Chapter 14 - Brain & Cranial Nerves Flashcards Preview

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Flashcards in Chapter 14 - Brain & Cranial Nerves Deck (59):
1

Development of brain

Three to four-week embryo:

forebrain (prosencephalon) 

midbrain (mesencephalon)

hindbrain (rhombencephalon) 

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Development of Brain 

5-week embryo

 

 telencephalon (cerebrum)

diencephalon (thalamushypothalamus & epithalamus)

mesencephalon (midbrain)

metencephalon (pons & cerebellum)

myelencephalon (medulla oblongata).

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Forebrain 

Midbrain 

Hindbrain

Forebrain - Cerebrum & Diecephalon (3) 

Midbrain & cebral aqueduct

Hindbrain - pons & cerebellum + medulla

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Brain stem

consists of?

 

continuation of spinal cord

consists of medulla oblongato, pons & midbrain

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second largest part of the brain. 

posterior to brain stem 

 

Cerebellum

 

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Diencephalon 

superior to brain stem

gives rise to thalamus, hypothalamus & epithalamus

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largest part of brain

cerebrum

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cranial meninges

dura mater - 2 layers (perieosteal & meningeal)

arachnoid mater

pia mater

 

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(3) extensions of the dura mater separate parts of the brain: 

 

1) falx cerebri - seperate the 2 cerebral hemispheres

2) falx cerebelli - seperate the 2 cerebellar hemispheres

3) tentorium cerebelli - seperate cerebrum from cerebellum

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Extensions of the Dura Mater: Brain Blood Flow and the Blood-Brain Barrier

Brain receives approximately _____% of the total blood supply. 
 Internal __ & __ arteries carry blood to brain. 
 Internal _____veins return blood from the brain. 

Blood-brain barrier (BBB) protects brain from?

 

20% 

internal carotid & vertebral arteries - blood to brain

internal jugular veins return blood from brain

 harmful substances. 

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Cerebrospinal Fluid (CSF) 

clear, colourless fluid that protects CNS from chemical & physical injuries, absorbs shock, helps transport nutrients & wastes from blood & nervous tissue

 

circulates through cavities in brain (ventricles) & spinal cord (central canal) & in subarachnoid space

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Ventricles

(3) & cerebral aqueduct

CSF-filled cavities within the brain. 

 1 lateral ventricles - in each hemisphere seperated byb septum pellucidum

third ventricle - along midline superior to hypothalamus

cerebral aqueduct - midbrain

fourth ventricle - between brain stem & cerebellum 

 

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CSF formation & circulation

formed in choroid plexuses of lateral ventricles → interventricular foramina → third ventricle → cerebral aqueduct (midbrain)→ 4rth ventricle → median aperture/lateral apertures (2) → subarachnoid space →central canal 

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Choroid plexus

 

networks of capillaries in the walls of the 
ventricles. 

 

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Ventricles are lined by __ cells

ependymal 

plasma is drawn from choroid plexuses through ependymal cells into ventricles to produce CSF

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CSF is reabsorbed into blood by?

arachnoid villi - extensions of arachnoid that project into dural venous sinuses (sugerior sagittal sinnus)

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Brain Stem (medulla, pons & midbrain) and Reticular Formation 

 

Medulla Oblongata

continous with superior spinal cord

white matter tract contains all sensory & motor tracts between spinal cord & other parts of brain 

white matter bulges on anterior - pyramids formed by large corticospinal tracts that pass from cerebrum to spinal cord

- common site of decussation of tracts - crossing over 

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Centers of the Medulla Oblongata 

 

Vital centers: 

cardiovascular 

respiratory 

also includes centers for vomiting, swallowing, sneezing, coughing and hiccupping. 

houses 5 pairs of cranial nerves (VIII-XII) 

portion of 3rd ventricle found here

 

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Midbrain (mesencephalon) 

Extends from the pons to the diencephalon. 
 Part of the ventricle found here- cerebral aqueduct - connects 3rd & 4rth ventricle

anterior part contains cerebral peduncles 

posterior part - tectum 

superior colliculli, inferior colliculi & substantia nigra

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Cerebral Peduncles - paired bundles of axons in anterior part of midbrain 

consists of?

Tectum 

axons of the corticospinal, corticopontine and 
corticobulbar tracts. 

Tectum- situated posteriorly and contains 4 rounded elevations: 2
superior ones called superior colliculi and 2 inferior ones called inferior colliculi

 

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Midbrain: 

Substantia Nigra

large area with dark pigments. Help control subconscious muscle activities.

Loss of neurons here is associated with Parkinson disease. 

 

 

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Redc Nucleus of Midbrain

: Help control voluntary movements of the limbs

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Midbrain contains cranial nerves....

III-IV

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Reticular Formation

Extends from upper part of spinal cord, throughout brain stem & into 
lower part of diencephalon.

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Part of the reticular formation called the Reticular activating System (RAS) consists of?

 consists of sensory axons that project to the cerebral cortex

S helps maintain consciousness. 

 

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Cerebellum 

vermis

anterior & posterior lobes

flocculonodular lobe

cerebellar cortex

arbor vitae

 

2nd largest part of brain

central constricted area = vermis

anterior and posterior lobes control subconscious aspects of skeletal movement. 

flocculonodular lobe - equilibrium & balance

cerebellar cortex - gray matter in form of parallel folds called folia

arbor vitae - tracts of white matter 

 

 

 

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Cerebellar peduncles 

3 pairs - superior, middle & inferior 

attach cerebellum to brain stem 

functions: coordinate movements, regulate posture & balance 

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Thalamus 

intermediate  mass joins right & left sides of thalamus

(7) major nuclei: anterior, medial, lateral, ventral, intralaminar, midline, reticular

major relay station for most impulse reaching primary sensory areas

transmits info from cerebellum & basal nuclei to primary motor area

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Hypothalamus

inferior to thalamus 

consists of mammillary body, median eminence, infundibulum, and # of nuclei. 

 

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Functions of the Hypothalamus

Control of the ANS

production of hormones 

regulation of emotion & behavioral patterns, eating & drinking, body temp, circadian rhythms 

 

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Epithalamus 

small region superior to thalamus 

consists of pineal gland that secretes melatonin which induces sleep

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Cerebrum 

seat of intelligence

cerebral cortex  - gray matter 

Gyri 

Sulci 

longitudinal fissure

cerebral hemispheres

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Cerebrum 

Gyri 

Sulci 

longitudinal fissure

cerebral hemispheres

Gyri - folds of cortical region 

Sulci - shallow grooves between folds 

longitudinal fissure - seperates cerebrum into right & left halves (contains falx cerebri)

cerebral hemispheres- connected internally by corpus callosum 

 

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Lobes of the cerebrum (4) 

frontal 

parietal 

temporal 

occipital 

 

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Cerebral white matter  consists of ?

myelinated axons in (3) types of tracts 

1) association 

2) commissural 

3) projection 

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myelinated axons in (3) tracts of cerebral white matter

1) association - axons conduct nerve impulses between gyri in same hemisphere

2) commissural - axons conduct nerve impulses to corresponding gyri in opposite hemisphere 

3 groups - corpus callosum, anterior & posterior commissure

3) projection - axons conduct nerve impulses from cerebrum to lower CNS (thalamus, brain stem & spinal cord) 

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Basal Nuclei 

(3) nuclei (masses of gray matter) deep within each cerebral hemisphere 

LENTIFORM NUCLEUS: 

globus pallidus - lateral to thalamus 

putamen - closer to cerebral cortex

CAUDATE NUCLEUS 

corpus striatum = caudate + lentiform

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Basal Nuclei 

functions

Help initiate and terminate movements, suppress unwanted movements & regulate muscle tone. 

 

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Limbic system

A ring of structures on inner border of cerebrum and floor of diencephalon

 

emotional brain - governs emotional aspects of behavior

also involved in olfaction & memory

 

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Components of the limbic system 

Limbic lobe - cingulate, parahippocampal gyrus & hippocampus 

dentate gyrus

amygdala 

septal nuclei 

mammillary bodies

anterior & medial nucleus 

olfactory bulbs 

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Functional Organization of the Cerebral Cortex: Sensory Areas 

(5) 

 

Primary somatosensory area-
Primary visual area- 
Primary auditory area- 
Primary gustatory area- 
Primary olfactory area-

 

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Cerebrum 

central sulcus 

precentral gyrus

postcentral gyrus

central sulcus - seperates frontal & parietal lobes

precentral gyrus -  frontal: primary motor area

postcentral gyrus - parietal: primary somatosensory area

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  1. Primary somatosensory area- ___ gyrus. 
  2.  Primary visual area- ____________lobe. 
  3. Primary auditory area- ____________lobe. 
  4. Primary gustatory area- base of the __ gyrus. 
  5.  Primary olfactory area- ____________lobe

  1. postcentral gyrus
  2. occipital
  3. temporal
  4. postcentral gyrus
  5. temporal

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Functional Organization of Cerebral Cortex: Motor Areas 

 

primary motor area - precentral gyrus

Broca's speech area - left cerebral hemisphere (speech production) 

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Functional Organization of the Cerebral Cortex: Association Areas 

 

 Somatosensory association area- behind 1° somatosensory area. 
Visual association area- occipital lobe. 
Auditory association area- temporal lobe. 
 Wernick's area- left temporal & parietal lobes (speech comprehension)
 Prefrontal cortex- anterior portion of frontal lobe.

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Cranial Nerves 

12 pairs 

sensory, motor & mixed

name & roman numberic number to identify

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Olfactory (I) Nerve 
 

Sensory nerve. 

Sense of smell
Olfactory cells converge to become olfactory nerve that end in olfactory bulb
 

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Optic (II) Nerve 

 

sensory

vision 

ganglion cells in retina join to form optic nerve 

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Oculomotor (III) Nerve

motor cranial 

originates in midbrain 

supply extrinsic eye muscles to control movement of eye & upper eyelid 

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Trochlear (IV) Nerve 

 

motor cranial nerve

smallest 

originate in midbrain

controls movement of eyeball 

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Trigeminal (V) nerve

largest cranial nerve

mixed 

(3) branches: ophthalmic, maxillary & mandibular 

deal with sensation of touch, pain & temperature.

motor axons supply muscles of mastication

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Abducens (VI) Nerve

motor cranial 

originates in pons

cause abduction of the eyeball (lateral rotation

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Facial (VII) Nerve

mixed cranial

sensory portion - from taste buds of anterior 2/3 of tongue

motor - arises from pons & deal with facial expression

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Vestibulocochlear (VIII) Nerve 

 

sensory cranial 

originates in inner ear

vestibular branch - impulses for equilibrium

cochlear branch - impulses for hearing

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Glossopharyngeal (IX) Nerve

mixed cranial 

sensory: taste buds of posterior 1/3 of tongue 

motor: arise from medulla & deals with release of saliva

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Vagus (X) Nerve

mixed cranial 

distributed from head & neck into thorax & abdomen

sensory: sensations - proprioception & stretching

motor - arise from medulla & supply muscles of pharynx, larynx & soft palate that are involved swallowing & vocalization

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Accessory (XI) Nerve

Motor cranial nerve. 

Divided into cranial accessory and spinal accessory nerves. 

 Supplies sternocleidomastoid & trapezius muscles to coordinate head movements. 

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Hypoglossal (XII) Nerve 

 

motor cranial 

conduct nerve impulses for speech & swallowing

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