The brain and cranial nerves

Question 1

Cerebrum

Answer 1

-weighs 1.3kg
-100 billion neurones
-outer layer= grey matter, accounts 80% weight
-inner= white matter
-vulnerable to injury through inter cranial pressure
-lobes of cerebrum correspond to bone names of skull

Question 2

Cerebrum structure

Answer 2

-grey matter develops quicker than white matter causes cortical region to roll and fold in on itself
-ridges= gyri
-deepest ridges= fissures
-longitudinal fissure- divides R and L hemispheres
-central sulcus- divides frontal and parietal lobes

Question 3

Frontal lobe

Answer 3

-largest lobe
-higher cognitive activity
-thinking, reasoning, understanding, language
-gives us our personality- auto biographical memory
-inhibited by alcohol and recreational drugs

Question 4

Damage to frontal lobe

Answer 4

-increased display of combativeness
-abusive attitude
-inappropriate sexual activity

Question 5

Areas of cerebral cortex

Answer 5

Brodmann’s areas -numbered regions of cortex that have been mapped to specific cognitive functions
Sensory areas- perception of sensory info
Motor areas- control execution of voluntary movements
Association areas- complex integrative functions eg. memory, personality, traits

Question 6

Primary somatosensory area

Answer 6

-parietal lobe
-in postcentral gyrus
-receive nerve impulses for sensations of touch, pressure, vibration, temperature, pain
-impulse depends on number of neurones present not size of the body part

Question 7

Parietal lobe

Answer 7

-supplied by large arteries
-where most strokes occur causing motor/ sensory paralysis

Question 8

Sensory homunculus

Answer 8

describes the way the somatosensory area is distorted as the impulse is dependent on the number of neurones not the size of the body part
eg. larger region of the somatosensory area receives impulses from the lips/ fingers compared to the thorax/ hip- more receptors in lips

Question 9

Motor area

Answer 9

-located in precentral gyrus of frontal lobe
-controls voluntary contractions of muscles
-homunculus map, more area devoted to muscles involved with skilled, complex or delicate movement

Question 10

Location primary visual area

Answer 10

-located at posterior tip of occipital lobe
-mainly on medial surface

Question 11

Primary gustatory area (taste) location

Answer 11

-located inferior to primary somatosensory areaP

Question 12

Primary auditory area location

Answer 12

-superior part of the temporal lobe

Question 13

Primary olfactory area location

Answer 13

-inferior medial temporal lobe

Question 14

White matter in cerebrum and tracts

Answer 14

-consists primarily of myelinated axons in 3 types of tract:
1. association tracts- conduct impulses between gyri in the same hemisphere
2. commissural tracts- conduct impulses between gyri from one hemisphere to another
3. projection tracts- conduct impulses to lower parts of the CNS or vice versa

Question 15

Corpus callosum

Answer 15

-one of the 3 important groups of commissural tracts
-thick band axons connects hemispheres

Question 16

Basal nuclei

Answer 16

-part of grey matter
-conspicuous centres of cell bodies deep in cortex
-3 basal nuclei help initiate and terminate movements
-control subconscious contractions of skeletal muscles eg. swinging arms when walking

Question 17

Limbic system
-3 integrated systems

Answer 17

-3 integrated systems
-1 and 2= limbic system
1.Reptilian brain- primary instincts and body functions, ANS
2.Mammalian brain- emotions, sexual desire, relationships, learning, memory
3.Cerebral cortex- neo cortex of homo sapiens

Question 18

Limbic system function

Answer 18

-doesn’t represent one part of the brain, its multiple parts that work together
-motivates feelings of primitive nature
-feeding, fighting, flight, sexual activity
-inhibited by frontal lobe

Question 19

Diencephalon

Answer 19

gives rise to hypothalamus and thalamus

Question 20

Medulla oblongata structure

Answer 20

-extends from pons above and continuous with spinal cord below
-2.5cm long
-pyramid shape, base upwards
-lies just within cranium

Question 21

Medulla oblongata functional centres

Answer 21

Cardiovascular centre- rate, force, diameter vessels
Respiratory rhythmicity centre- rate and rhythm breathing
Vomiting, coughing and sneezing centres

Question 22

Pyramids medulla

Answer 22

-2 external bulges formed by motor tracts
-axons from left pyramid cross to the right and vice versa
-decussation of pyramids- so left hemi of brain controls right side muscles and vice versa

Question 23

Pons varolii

Answer 23

-above medulla
-connects spine with brain

Question 24

Mid brain
2 parts

Answer 24

Tectum
-contains colliculus- important route for sensory info
-filters unnecessary info so can concentrate on stimulus
Substantia nigra
-largest nuclear mass in mid brain
-involved automatic movement of skeletal muscle
-failure of this causes parkinson’s

Question 25

Reticular formation

Answer 25

-maintain consciousness, alert, aware
-inactivation of RAS produces sleep, state partial consciousness
-prevents sensory overload by filtering insignificant info

Question 26

Cerebellum location

Answer 26

-2nd largest part of brain
-inferior to cerebrum and posterior to brain stem

Question 27

Cerebellum function

Answer 27

-compares intended movements with what is happening with skeletal muscles
-regulates posture, equilibrium and balance

Question 28

Hypothalamus

Answer 28

-area of diencephalon
-control ANS
-coordinates between NS and endocrine system
-body temperature
-regulates hunger/ thirst
-assists with circadian rhythm

Question 29

Cranial meninges
Function, location, layers

Answer 29

-helps protect brain
-continuous with spinal meninges
-tough outer dura mater
-spidery arachnoid mater
-thin, delicate pia mater

Question 30

Brain blood flow

Answer 30

-consumes 20% of o2 and glucose even when resting
-anteriorly (front), internal carotid arteries supply blood to brain
-posteriorly(back), via vertebral arteries
-internal jugular veins are the venous return

Question 31

Vascular endothelium

Answer 31

-differs in brain capillaries compared to other organs
-forms tight junctions with end feet of nearby astrocytes
-this forms a blood brain barrier which isolates the parenchyma of the brain from blood and substances within it

Question 32

Cerebral spinal fluid
Function

Answer 32

-circulates through cavities in brain= brain ventricles and spinal cord
-absorbs shock and protects brain and spinal cord
-helps transport of nutrients and waste

Question 33

Flow of CSF

Answer 33

-flows continuously between pia mater and arachnoid that is tightly attached to outer dura
-constant pressure
-rate of reabsorption matches rate formation at 20ml per hour

Question 34

CN I

Answer 34

olfactory nerve

Question 35

CN II

Answer 35

optic nerve

Question 36

CN III, IV, VI

Answer 36

-innervate extraocular muscles, allow us to move eyes
-CN III- supply motor input to eyelid muscles and facilitates pupillary constriction

Question 37

CN V

Answer 37

-trigeminal nerve
-major sensory nerve of face
-3 branches which supply area of face:
1.ophthalmic
2.maxillary
3.mandibular

Question 38

CN VII

Answer 38

-facial nerve
-5 somatic branches which innervate muscle of facial expression
-also carries some taste sensations
-paralysis of nerve called bell’s palsy and leads to loss of ability to close eyes, impairment of taste

Question 39

CN VIII

Answer 39

-vestibulocochlear nerve
-vestibular component carries info on balance
-cochlear component enables hearing
-damage causes vertigo, ringing in ears, deafness

Question 40

CN IX

Answer 40

-glossopharyngeal nerve
-taste sensations as well as ANS impulses to salivary glands

Question 41

CN X

Answer 41

-vagus nerve
-carries most of parasympathetic motor efferent to the organs of thorax and abdomen

Question 42

CN XI

Answer 42

-spinal accessory nerve
-supplies somatic motor innervation to the trapezius and sternocleidomastoid muscles ( neck and shoulders)

Question 43

CN XII

Answer 43

-hypoglossal nerve
-solely for tongue
-chew, talk, swallow