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ICS > The PNS > Flashcards

The PNS Flashcards

1
Q

What is the CNS made up of?

A

The spinal chord and the brain

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2
Q

What 2 sections if the PNS split into?

A

The Afferent (Sensory) and the Efferent (Motor)

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3
Q

In the PNS Efferent/Autonomic system is split into ..?

A

The somatic and the autonomic system

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4
Q

What are the 3 parts of the Autonomic system?

A

The parasympathetic, sympathetic and Enteric

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5
Q

What does the afferent/sensory system do?

A

conduct signals towards the CNS

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6
Q

What does the efferent/motor system do?

A

conducting signals away from the CNS

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7
Q

What is the basic structural and functional unit of the nervous system?

A

neurones

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8
Q

What are neurones?

A

highly specialised cells, that pass information between neurones (via synapses)
-vary greatly in size and shape

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9
Q

What is the role of glial cells in the nervous system?

A

-no direct role in information processing
-They have ancillary roles that are essential to normal functioning of the nervous system
(eg oglidendrocytes and myelin sheaths)

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10
Q

What insulates the neurones in the PNS?

A

schwa cells, the myelin sheath

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11
Q

Look at and revise the the structure of the sensory and motor neurones

A

all good?

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12
Q

What are the different types of cell junctions?

Could you recognise a picture of them all?

A
  • Desmosomes
  • Adheren junctions
  • Tight Junctions
  • Gap Junctions
  • Synapses
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13
Q

What do does a desmosome do?

A

Hold the cell firm but flexible

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14
Q

What do adhering junctions do?

A

Mechanically attach cells

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15
Q

What do tight junctions do?

A

Restrict extracellular molecular movement

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16
Q

What do gap junctions do?

A

They are small protein channels directly connecting cells

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17
Q

What do synapses do?

A

Transmit chemical signals from one neurone to another

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18
Q

What do ATPase pumps do?

A

They are enzymes that use ATP to establish and maintain ion gradients across a membrane

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19
Q

How is the resting potential maintained?

A

-Na+/K+ ATPase pump transports 3Na+ out of the cell and 2k+ into the cell (against concentration gradients) for every ATP hydrolysed

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20
Q

what value is resting potential?

A

about -70mV in neurones (equilibrium reached at -20 to -90mV)

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21
Q

at resting potential what ion are cells more permeable to and why?

A

K+, due to the facilitated diffusion through K+ channels

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22
Q

can large anions move freely through the membrane and what affect does this have on the membrane potential?

A

NO.
-proteins, nucleotides, and phosphate bound ATP cannot move freely through the membrane, negative potential develops on the inside of the membrane

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23
Q

What is hyper polarisation and why does it occur?

A

opening of K+ and Cl- channels increases membrane potential and makes it more negative

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24
Q

Opening Na+ and Ca2+ channels reduces the membrane potential… leads to..?

A

depolarisation

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25
Q

What type of channel gates are there?

A

Ligand gated and Voltage gated

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26
Q

What are ligand gated channels?

A

A signalling ligand binds to a receptor to open or close the channel

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27
Q

What are voltage gated channels?

A

Channels that are opened or closed in response to a change in the membrane potential

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28
Q

What is an action potential?

A

Mechanism by which electrical signals are propagated along the membranes of neurones

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29
Q

What speed are signals conducted along neurones?

A

less than 1m/s

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30
Q

What causes initial depolarisation?

A

Stimulus causes the the opening of Na+ (or Ca2+) voltage gated channels

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31
Q

What happens during depolarisation?

A

Na+ (and Ca2+) channels are closed and K+ channels open, returning the neurone to resting state

32
Q

When is the Action Potential triggered?

A

When the membrane potential rises above the threshold of -55mV

33
Q

How is the wave of depolarisation unidirectional?

A

the voltage gated channels become inactivated following depolarisation

34
Q

Conduction velocity depends on…?

A
  • The size of the cell
  • The electrical capacity of its membrane
  • Myelination
35
Q

How doe the size of the cell affect conduction velocity?

A

Smaller cells have greater resistance so the velocity is reduced

36
Q

How does the electrical capacity of the membrane affect conduction velocity?

A
  • reduce capacitance (ability of the membrane to store charge)
  • myelination increases the conduction velocity
37
Q

what is myelin?

A

lipid and protein containing substance, produced by ogliodendrocytes (CNS) and schwa cells in the PNS

38
Q

What does myelin do?

A
  • Increases the electrical conductance
  • gives neurones their white colour
  • nerve impulses jump from node of ranvier to the next by saltatory conduction
39
Q

Neurotransmission can happen directly and indirectly, how?

A

Directly- gap junctions

Indirectly-chemical synapses

40
Q

Where would you find chemical synapse?

A

either neurone to neurone
or
neurone to effectors
(smooth muscle)

41
Q

How do chemical synapses work?

A
  • membrane depolarisation and Ca2+ causes the vesicles to fuse with the presynaptic membrane and release neurotransmitter into the synaptic cleft
  • neurotransmitter diffuses across the membrane and binds to receptors creating a resonse
42
Q

what is a motor unit?

A

one motor neurone + muscle fibre

43
Q

What does the parasympathetic nervous system do?

A
  • slows down heartbeat
  • constricts bronchi
  • stimulates peristalsis and secretion
  • stimulates relate of bile
  • controls bladder
44
Q

what does the sympathetic nervous system do?

A

“fight or flight”

  • increases heart rate
  • pupils dilate
  • inhibits flow of saliva
  • prevents peristalsis and secretion
  • bronchiodilation
  • conversion of glycogen to glucose
  • secretion of adrenaline and nor-aadrenaline
  • inhibits bladder contraction
45
Q

What are the 2 types of acetyl choline receptors?

A

Nicotinic (nAchR) and Muscaranic (mAchR)

46
Q

what type of receptors are nicotinic receptors?

A

Ligand gated ion channels…. receptor for Ach

47
Q

What is another name for nicotinic receptors?

A

ionotrophic- fast synaptic transmission

48
Q

Where would you find nicotinic Ach receptors?

A

Autonomic ganglia (sympathetic and parasympathetic)
neuromuscular junctions
and brain and spinal chord

49
Q

What type of receptors are msucaranic Ach receptors?

A

G coupled protein receptors

50
Q

What are muscaranic receptors also known as?

A

metabotrophic - slow synaptic transmission

51
Q

Where would you find muscaranic Ach receptors?

A

postganglionic- parasympathetic
sweat glands, sympathetic
brain

52
Q

What are inotropic receptors? and what do they do?

A
  • allow fast acting transmission where the postsynaptic receptor is directly linked to an ion channel (allowing electrical signal to be generated in the cell)
  • enables membrane depolarising and production of excretory neurotransmission -id Na+/Ca2+ channels opened
53
Q

With inotropic receptors what happens if Cl- or K+ channels are opened?

A
  • hyperpolarisation

- reduced membrane excitability (inhibitory neurotransmission)

54
Q

What are metabotrophic receptors and what do they do?

A
  • They perform slow synaptic transmission (seconds to hours)
  • post synaptic receptor signals to channel proteins are through GCPR
  • they can act directly or indirectly via second messengers
55
Q

What is an example of a metabotrophic receptor..?

A

a gland…

56
Q

Does every cell respond in the same way to the same extracellular signal?

A

No, different cells can respond in different ways to the same extracellular signal… each cell has a programmed response to specific combinations of molecules

57
Q

How are neurotransmitters removed from the synaptic cleft?

A

-enzymatic degradation and reuptake

58
Q

What is the SNARE hypothesis?

A

The vesicular membrane carries a v-SNARE and the target membrane, a t-SNARE. The two SNAREs can form a fusion particle, and with energy input from the hydrolysis of ATP, can cause membrane fusion. Spontaneous fusion is prevented by v- and t-SNARE clamping proteins.

59
Q

What is the reflex arc made up of?

A

A sensory neurone and a motor neurone with a synapse in between

60
Q

What is a pacinian corpuscle and what does it detect?

A

A mechano receptor in the skin, detects change in pressure due to stimulus

61
Q

what is the difference between cardiac and neuronal AP?

A

cardiac is myogenic and has a longer duration

-cardiac has a Ca2+ initiation where as the neurones have a Na+ initiation

62
Q

Look ver the paper provided during the LSRC

A

….

63
Q

what do all post ganglionic innervations of the sympathetic NS use?… what is the exception

A

noradrenaline

-sweat glands and vascular smooth muscle wishing the skeletal muscle (use acetylcholine)

64
Q

Examples of neurotransmitters of the CNS

A

Dopamine, serotonin, glycine.

None of these are in the autonomic region of the PNS

65
Q

Adrenaline is released as a sympathetic response, and causes bronchiodilation, what does this achieve?

A

greater oxygen uptake

bronchioconstriction in response to Adrenaline would be detrimental to increasing the metabolic capacity of individual

66
Q

Which hormones/neurotransmitter causes smooth muscle contractions?

A

Adrenaline

67
Q

How does adrenaline trigger smooth muscle contraction?

A

peripheral blood vessels contract to increase flow to muscles and stem loss of blood from injury

68
Q

Injury, vasoconstriction of vasodilation?

A

Constriction

69
Q

What is myasthenia gravis?n nh

A
  • autoimmune disease resulting from antibodies formed against the nAchR… means that the individual is unable to sustain muscle contraction
  • receptor depletion prevents a sustained AP/muscle contraction
70
Q

Which enzyme breaks down Acetylcholine?

A

AchE- Acetylcholine esterase

71
Q

How would you treat a muscle contraction/sustained AP disorder such as myasthenia gravis?

A
  • boost Ach levels-prevent breakdown using AchE inhibitors
  • immunosupression-corticosteriods
  • plasmapheresis - removing the anti-achR antibodies
72
Q

where is choline acetyltransferase produced?

A

In the cell body of cholinergic neurones (then transported to axon terminal)

73
Q

what does choline acetyltransferase do?

A

synthesises the formation of acetylcholine by catylzing the transfer of an acutely group from acetyl coA to a choline

74
Q

What are catecholamines?

A

small organic molecules that contain an amine group and a benzene ring with 2 hydroxyl groups

75
Q

Give 3 examples of catecholamine neurotransmitters

A
  • adrenaline
  • noradrenaline
  • dopamine
76
Q

adrenaline, noradrenaline and dopamine are synthesised from the same amino acid, which one?

A

tyrosine, which contains a benzene ring

77
Q

which receptors cause skin pain?

A

noci receptors

ICS (11 decks)

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