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NSF > Nervous system > Flashcards

Nervous system Flashcards

1
Q

CNS

A

brain + spinal cord (together = neuraxis)

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2
Q

nerves in/out CNS

A

sensory/afferent = in

motor/efferent = out (incs glands etc)

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3
Q

response to stimulus

A
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4
Q

segmental reflex

A

just 2 neurons

possible w/o brain (so can be possible when dead)

e/g/ withdrawal reflex when grab toe

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5
Q

patella reflex

A

tap patella + knee kicks out - useful diagnostically to see if sensory + motor + muscle all working
shows there can be multiple sensory pathways at once - patella reflex + to brain saying ‘touched’

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6
Q

spinal cord structure

A
dorsal columns = standard sensory pathways - gracile from hindlimbs (arse) + cuneate to forelimbs

pathways in specific places in spinal cord - injury certain place will therefore cause certain symptoms, useful for diagnosis

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7
Q

upper motor neurones

A

part CNS

corticospinal + corticonuclear motor pathways

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8
Q

lower motor neurones

A

leave CNS + part PNS

2 types:
* alpha-motor
* gamma-motor

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9
Q

cranial + spinal nerves

A

nerves in/out bottom of brain (not many) + nerves in/out spine

v similar

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10
Q

neuron
nerve fibre
nerve
cell body

A

nerve cell
part neuron
‘trunking bunches axons + support cells
nucleus + G. app etc = soma = perikarion

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11
Q

basic properties neurones

A
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12
Q

effect of axon thickness

A

fatter axons conduct faster as less resistance electrical signal, e.g. evolved in squid

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13
Q

main fibre types

A
  1. A
  2. Aa (A delta)
  3. C

defined by characteristics neyronal axon

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14
Q

A fibres

A
  • large, fast, myelinated
  • carry touch + press sensations
  • also many motor neurons this type
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15
Q

Aa fibres

A
  • small, lightly myelinated - bet A + C anatomically
  • important in transmission of pain
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16
Q

C fibres

A
  • smallest, slowest, unmyelinated
  • sensory + autonomic motor neurons
  • inflammatory pain, e.g. heat takes longer feel
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17
Q

saltatory conduction

A

elec current jumps from node to node along myelinated axon

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18
Q

why do myelinated neurons conduct faster

A

myelin insulates = conduction not disspated in tissues = faster

neurons cont salty sol bc salty sols conduct elec

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19
Q

effect cooling on neuronal conduction

A

decreases conduction velocity = decreased speed at which a pots gened + travel to brain = less a pots through = increased refractory periods = less pain

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20
Q

main factors affecting conduction velocity

A
  1. fibre diameter
  2. myelination
  3. temp
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21
Q

refractory period

A

period in which can’t fire a pot
1. absolute = a pot impossible as Na+ channels inactivated
2. relative = stim not big enough cause a pot
* after a pot harder gen another as mem more neg + polarised + some Na+ channs inactivated

Stim 2 irrelevant as threshold already reached + a pot already gened = absolute refractory period + no amount elec stim can change (= won't go back other way = a por one direction only)
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22
Q

types neurones

A
  1. multipolar
  2. pseudo-unipolar
  3. bipolar
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23
Q

multipolar neurone

A
  • standard found most places
  • loads of ways off
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24
Q

pseudo-unipolar neuron

A
  • comes out 1 place but immediately splits
  • sensory neurone - spinal reflex
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25
Q

bipolar neurone

A
  • 2 routes out cell body
  • seen least often
  • sensory neurone - retina
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26
Q

synapse

A
  • junction bet 2 neurones, generally mediated chems
  • give graded excitation post-syn neurone - deviation RMP big enough = a pot gened

causing excitatory (depolarising)/inhibitory (hyperpolarising) postsynaptic pot = EPSP/IPSP

expect 1 neurone to many

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27
Q

electrical synapse

A

ionic current directly 1 cell to another for fast communication + to synch activity grp neurons/muscle cells
* v important in heart to spread contraction

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28
Q

pre-synaptic Ca2+ channel types

A
  1. L-type
  2. N-type
  3. T-type

blocked by several types toxins

structurally sim Na+ v-gated w few aas diff

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29
Q

L-type Ca2+ channel

A
  • main type
  • act for Long time
  • cardiovascular drugs target these
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30
Q

N-type Ca2+ channels

A

Neither long not transient = open middle amount time

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31
Q

T-type Ca2+ channels

A

Transient = briefly opening

32
Q

how chem synapse works

A

arrival a pot at pre-synaptic = change mem pot = v-gated Ca2+ channs open = influx Ca2+ = exocytosis NT as vesicles move + fuse presyn mem, NT moves across synaptic cleft + fuses postsyn mem = a pot stimmed + gened next neuron

33
Q

a pot feedback type

A

all or nothing = reach threshold + all Na+ channs open = pos feedback

pos feedback usually pathological

34
Q

acetylcholine recycling

A

Removed synaptic cleft 3 ways:
1. diffusion
2. enz degradation
3. uptake into cells (neurons + glia)

enz acetylcholinesterase (ACHE) breaks down -> choline + acetate - choline taken up into presyn neuron on Na+-choline cotransporter, reformed by enz (AcCoA) + repackaged vesicles to go again

breakdown Ach = end response

small mol NTs (like Ach) packages terminal. large peptide NTs packaged cell body + transported via microtubules

35
Q

how receptors in post-sym mem work

A

ligand-gated ion channels = receptors in post-syn mem
* have central pore whose diameter is altered when transmitter binds receptor

enough EPSPs = reach threshold = a pot
36
Q

hyperkalaemia

A

causes depolarisation = RMP close threshold = neurons more excitable = muscle twitching

K disorder

37
Q

hypokalaemia

A

causes hyperpolarisation = RMP further from threshold = sk muscle weakness

K disorder

38
Q

synaptic summation

A

several presyn end bulbs release NT same time = more likely gen nerve impulse
* consider effects canceling out inhibitory vs excitatory etc
* spatial + temporal

39
Q

drugs involving NTs

A
  1. antagonists = NTs blocked binding
  2. agonists = mimic NT as chemically similar to cause false response
  3. block enzs that degrade NT to prolong action
40
Q

neuromuscular junction is?

NMJ

A

special type synapse bet neuron + sk muscle cell not 2 neurons

41
Q

what is terminal button

A

small knob @ end axon that releases NTs

42
Q

how does NMJ work

A
  • a pot in motor neuron propogated to terminal button
  • presence a pot triggers opening v-gated Ca2+ channs = entry Ca2+ terminal button
  • triggers release Ach by exocytosis
  • Ach diffs across space sepping nerve + muscle cells
  • Ach binds specific receptor sites on motor end plate muscle cell mem (= cholinergic receptors)
  • opens ion channs in mem
  • relatively large movement Na+ into muscle cell vs small K+ out = end-plate pot
  • small EPSPs add up + cause local current flow bet depolarised endplate + adjacent mem
  • = v-gated Na+ channs mem open
  • mem pot depolarises to threshold
  • = a pot gened, propagated through muscle cell

NMJ = always nicotinic receptor

43
Q

diff sk muscle + nerve responses post-syn

A
  • sk muscle RMP tends more neg (~90)
  • a pot sk muscle slower
  • a pot along surface nerve vs down T tubules penetrating muscle (= slower)
  • diff ion channs but analogous
44
Q

v rough how a pot causes contraction in sk muscle

A

a pot running along + into muscle causes tension = Ca2+ released muscle centre

45
Q

sims bet synapse + NMJ

A
  • both consist excitable cells sepped synaptic cleft, preventing direct transmission elec activity
  • axon terminals of both store chem messenger
  • binding NT w receptor sites postsyn mem opens specific channs, allowing ion movement to alter mem pot cell
  • resultant change of both graded pot
46
Q

diffs bet synapse + NMJ

A
  1. neuron-neuron vs motor neuron-sk muscle fibre
  2. NMJ = 1-1 transmission a pot; synapse = summation EPSPs
  3. NMJ always excitatory; synapse excit or inhib
    * sk muscle only inhibited in CNS, not at NMJ
47
Q

what is ANS

A

autonomic nervous sys
* involuntary, often unconscious
* maintains homeostasis
* consistingautonomic sensory neurons, integrating centres CNS, autonomic motor neurons, effector organs in periphery (e.g. smooth muscle, heart, glands)

incs central + peripheral nerve components

48
Q

where is ANS regulated

A

centres in brain - mainly hypothalamus + medulla oblongata (receives input other parts cerebrum)

49
Q

most famous autonomic nerve

A

vagus - sensory + motor components from many systems + controls much parasympathetic sys

50
Q

sensory receptor types

A
  1. chemoreceptors - monitor blood CO2 levels
  2. mechanoreceptors - detect degree stretch walls organs, blood vessels…
  3. baroreceptors - type mech to detect blood press
51
Q

ANS peripheral components

A

pre + post ganglionic motor neurones w nuclei in CNS + ganglia

1 sensory neuron, cell body in dorsal root ganglion

not in somatic

52
Q

ganglion

A

collection cell bodies outside CNS

53
Q

pre vs post gang neurons

A

post unmyelinated = bunch together appear grey.

bunch myelinated pre together appear white (myelin whiteish)

54
Q

junction postgang neuron on effector organ vs NMJ

A

postgang:
* can inhibit or excite target
* branched w varicosities
* longer latency - synapse in middle = slower response (fast but direct elec transmission faster)
* greater spatial activation

55
Q

what are varicosities

A

swellings that can all release neurotransmitter - dropping it from number places along, not just at end

56
Q

which muscle type which sys

A

ANS = smooth
SNS = skeletal

57
Q

sympathetic vs parasympathetic

w/in ANS

A

sym = fight or flight
parasym = rest + digest

not mutually exclusive

58
Q

sympathetic general

A

controlled + processing in brain cortex - hypothalamus

T1 = 1st thoracic segment L2 = 2nd lumbar segment
59
Q

parasympathetic general

A

Salivation
Lacrimation - keep eye good cond + lubricated
Urination
Digestion
Defecation

panic response, e.g. peeing yourself asw

60
Q

where does parasympathetic response originate from in neuraxis

A

brainstem cranial nerves + sacral (bottom) spinal cord = craniosacral sys

not from segments spinal cord in between

61
Q

parasympathetic pre + post gang neuron structure

A

long pre, v short post - ganglion often in wall target tissue, e.g. in gut wall/heart
more local as not loads post gang neurons (1:2 pre:post)

62
Q

viscera

A

organs in main body cavity, esp in abdomen

63
Q

balance bet symp + parasymp sys

A

when at rest parasymp more dominant + symp acting low level to maintain homeostasis, then in response fear/excitement symp more dominant w widespread response

64
Q

diff bet somatic + autonomic

A
65
Q

structure neurons sympathetic sys

A

short pre, long post

ganglion far from tissue, often in sympathetic trunk (v close spinal cord + most nerves symp sys pass through)

66
Q

adrenal medulla

structure + function

A
  • centre adrenal gland on end sympathetic nerve
  • chromaffin cells secrete mostly adrenaline (lil bit noradrenaline) directly into bloodstream for generalised symp response
  • ganglion + post-gang neuron all in one in tissue (=technically no postgang)
67
Q

4 options motor pathway autonomic reflex

A
  1. lots together, synapse together, form loop in trunk, leave together, then to extremities - blood vessels, sweat glands, hair erector muscles
  2. straight on to tissue - sep to heart/thoracic viscera (white as lots myelinated postgang neurones)
  3. spinal nerve through symp chain to own ganglion (prevertebral)
  4. synapse in adrenal medulla - special case
68
Q

fight or flight response

A

in anticipation - immediate increase heart rate, mostly due adrenaline + noradrenaline

stress set up to have O2, heart rate etc ready prior to needing to run so get set off straight at max. otherwise would pass out too much activity from sprinting as not enough time build up O2, cardiovascular sys etc

mediated hypothalamus + medulla in brainstem

69
Q

sympathetic ANS NTs

A

short, myelinated pregang releases Ach (bc synapse)
longer, unmyelinated postgang releases noradrenaline

70
Q

parasymp ANS NTs

A

long myelinated pregang releases Ach that binds nicotinic receptors
shorter unmyelinated postgang releases Ach that binds muscarinic receptors

71
Q

nicotinic vs muscarinic

A

both receptor prots Ach acts on

N fast, M slow so ganglions (synapse bet 2 neurons has be) + somatic all fast
* smooth muscle + glands slow = M

72
Q

summary NTs + receptors

A
all pregang neurons release Ach
73
Q

muscarinic receptor details

A

typical G prot coupled receptors
* 5 molecular subtypes known
* most pharmalogical agents non-selective
* M2 + M3 most important

74
Q

G prot coupled as opposed ion channs

A

response slower to start + lasts longer

75
Q

catecholamine postsyn receptors

A
  • alpha1 - typically on blood vessels, e.g. vasoconstriction arterioles
  • alpha2
  • beta1 - typically on heart, e.g. increase heart rate
  • beta2 - in airway for bronchodilation, e.g. ventolin in inhaler B2 agonist

= adrenoreceptors to adrenaline + noradrenaline

76
Q

anaphylactic shock

A

massive drop blood press due allergies, severe injury, etc

NSF (22 decks)

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