Introduction to Nervous System

Question 1

What are the 2 parts of the CNS?

Answer 1

brain, spinal cord

Question 2

What constitutes the PNS?

Answer 2

nerves in body, cranial nerves

Question 3

Divisions of PNS?

Answer 3

Sensory division  (somatic and autonomic)
(5 senses, pressure sensing in brain, chemoreceptors, thermoreceptors)

Motor division = somatic division (spinal nerve/cranial nerves) or autonomic division (sympathetic - spinal nerves only) and (parasympathetic division - spinal and cranial nerves)

Question 4

What does the somatic PNS do?

Answer 4

control motor and sensory function for body wall (skin, skeletal muscles)

Question 5

What does the autonomic PNS do?

Answer 5

aka visceral PNS

regulates function of viscera (internal organs, smooth muscle, pupils, sweating, blood vessels, bladder, intestine, glands, heart contraction)

Question 6

What is the sympathetic NS?

Answer 6

fight or flight response

increase HR, dilate pupils, increase blood flow to muscles, inhibit digestion

Question 7

What is the parasympathetic NS?

Answer 7

rest and digest response
can counteract sympathetic (decrease HR, stimulate digestion)
more discrete anatomy largely controlled by cranial nerves

Question 8

Two directions of impulse flow?

Answer 8

sensory = afferent
motor = efferent 

EFFERENT = EXIT

Question 9

What is the importance of afferent/efferent flow?

Answer 9

understand flow of information through brain

E.g. body responds to changing BP by changing vascular tone
baroreceptors in aorta sense pressure in vessel, sends afferent impulse to hypothalamus that sends an efferent motor response

Question 10

Frontal lobe?

Answer 10

from front of brain to central sulcus

personality/conscious decision making

Question 11

Parietal lobe?

Answer 11

behind frontal lobe
contains somatosensory cortex
sensory info from somatic PNS comes here

Question 12

Occipital lobe?

Answer 12

at back of brain

vision

Question 13

Temporal lobe?

Answer 13

one either side of brain
primary auditory cortex
personality (fear, anxiety, food behaviour at amygdala)

Question 14

Cerebellum?

Answer 14

fine motor skills

Question 15

Brain stem?

Answer 15

centres vital for life here

Question 16

What is the function of cortex folds?

Answer 16

to pack neurones into confines of skull (high SA)
sulcus - valley
gyrus - ridge, folds

Question 17

Corpus callosum?

Answer 17

fibrous tract that allows communication between two hemispheres of the brain

Question 18

What are the 12 cranial nerves?

Answer 18

control face and neck
vagus nerve has both afferent and efferent pathways
O O O To Touch And Feel Very Good Velvet Such Heaven

Olfactory I
Optic II
Oculomotor III
Trochlear IV
Trigeminal V
Abducens VI 
Facial VII
Vestibulocochlear VIII
Glossopharyngeal IX
Vagus X
Accessory XI
Hypoglossal XII

Question 19

What 3 layers protect the brain?

Answer 19

meninges - connective tissue layers to protect and supply of blood vessels
dura mater (outer and inner)
arachnoid
pia mater 
(superficially to deeply)

Question 20

What two PNS roots emerge from the spinal cord?

Answer 20

ventral horn - efferent (from spinal cord to body)

dorsal horn - afferent (from peripheries and reflex at spinal cord or to brain)

Question 21

Where does the CNS end?

Answer 21

at the margins of the spinal cord

Question 22

How to distinguish between ventral and dorsal root?

Answer 22

dorsal root ganglia (collection of sensory neurone cell bodies)

Question 23

What is the structure of a nerve?

Answer 23

Spinal nerves contain afferent and efferent axons bundled into fascicles surrounded by perineurium

whole nerve in tough epineurium capsule

individual axons myelinated and wrapped in endoneurium (or if no myelin = nociceptive (pain) )

Question 24

What is resting membrane potential for neurone?

Answer 24

-70mV

Question 25

Process of action potential

Answer 25

Release of NT cause depolarisation - influx of Na+ via VCSCs At +40mV, VGPC open and K+ moves out - repolarisation Hyperpolarisation - rebalance two ions

Question 26

Diameter of synaptic cleft

Answer 26

10nm

Question 27

Synaptic transmission?

Answer 27

Action potential causes release of NT filled vesicles across synaptic cleft NT bind to receptors on post-synaptic neurone

Question 28

How to tell if it is a presynaptic neurone?

Answer 28

lots of NT filled vesicles

Question 29

What other cells are in the brain?

Answer 29

``` glia cells (50% of all cells in brain) - astrocytes form blood brain barrier, wrap podocytes around blood vessels to form junctions to seal blood brain barrier, mop up NT from synapse, sense chemicals in blood and move to synapse ``` microglia - phagocytes of brain (immune cells) oligodendrocytes - myelin producing cells of CNS

Question 30

What are myelin producing cells of PNS?

Answer 30

Schwann cells

Question 31

Difference in regenerative capacity between CNS and PNS?

Answer 31

PNS axons can regenerate after injury - injury stimulates phagocytes to remove debris inhibiting regrowth - not complete regeneration CNS axons are limited - glia inhibit regeneration - glial scars form in place of injured brain tissue - absence of guidance cues to stimulate axon growth

Question 32

How is PNS axon regeneration compromised?

Answer 32

by abnormal axons sprouting and non-specific target reinnervation this may cause neuropathic pain

Question 33

First pathway in involved in sensory perception? | What type specifically?

Answer 33

dorsal column/mediated lemniscus pathway fine touch, vibration, two-point discrimination

Question 34

How does sensory pathway work for stubbed toe?

Answer 34

- nociceptors in toe enter spinal cord grey matter - axons of these neurones travel up spinal cord to brainstem (medulla) - here side of control switches (to contralateral side, not ipsilateral) and second axon sent to thalamus then to primary somatosensory cortex

Question 35

What is the primary somatosensory cortex?

Answer 35

receives all sensory information from body

Question 36

What sensory pathway conveys pain and temperature sensation?

Answer 36

spinothalamic pathway

Question 37

What does damage to dorsal column do?

Answer 37

still feel pain and temp in affected limb if spinothalamic pathway intact

Question 38

Difference between both pathways?

Answer 38

- dorsal column pathway enters spinal column on same side and switched at brainstem - spinothalamic pathway immediately goes to other side of body

Question 39

What is the first motor pathway?

Answer 39

Lateral corticospinal tract

Question 40

Where do motor pathways originate from?

Answer 40

pre central gyrus (motor cortex) and go down via brain steam and jump to other side and go down spinal column

Question 41

What is the second motor pathways for orientation and balance?

Answer 41

Vestibulospinal tract | Ipsilateral

Question 42

If one side of body is working what is likely to be the case?

Answer 42

Damage not to entire somatosensory cortex

Question 43

What tells if an injury is not peripheral?

Answer 43

if reflex activity intact and arm and leg affected

Question 44

Why would a injury be unlikely to be spinal cord injury?

Answer 44

only one side affected