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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
What type of channel gates are there?
Ligand gated and Voltage gated
26
What are ligand gated channels?
A signalling ligand binds to a receptor to open or close the channel
27
What are voltage gated channels?
Channels that are opened or closed in response to a change in the membrane potential
28
What is an action potential?
Mechanism by which electrical signals are propagated along the membranes of neurones
29
What speed are signals conducted along neurones?
less than 1m/s
30
What causes initial depolarisation?
Stimulus causes the the opening of Na+ (or Ca2+) voltage gated channels
31
What happens during depolarisation?
Na+ (and Ca2+) channels are closed and K+ channels open, returning the neurone to resting state
32
When is the Action Potential triggered?
When the membrane potential rises above the threshold of -55mV
33
How is the wave of depolarisation unidirectional?
the voltage gated channels become inactivated following depolarisation
34
Conduction velocity depends on...?
- The size of the cell - The electrical capacity of its membrane - Myelination
35
How doe the size of the cell affect conduction velocity?
Smaller cells have greater resistance so the velocity is reduced
36
How does the electrical capacity of the membrane affect conduction velocity?
- reduce capacitance (ability of the membrane to store charge) - myelination increases the conduction velocity
37
what is myelin?
lipid and protein containing substance, produced by ogliodendrocytes (CNS) and schwa cells in the PNS
38
What does myelin do?
- Increases the electrical conductance - gives neurones their white colour - nerve impulses jump from node of ranvier to the next by saltatory conduction
39
Neurotransmission can happen directly and indirectly, how?
Directly- gap junctions | Indirectly-chemical synapses
40
Where would you find chemical synapse?
either neurone to neurone or neurone to effectors (smooth muscle)
41
How do chemical synapses work?
- 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
what is a motor unit?
one motor neurone + muscle fibre
43
What does the parasympathetic nervous system do?
- slows down heartbeat - constricts bronchi - stimulates peristalsis and secretion - stimulates relate of bile - controls bladder
44
what does the sympathetic nervous system do?
"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
What are the 2 types of acetyl choline receptors?
Nicotinic (nAchR) and Muscaranic (mAchR)
46
what type of receptors are nicotinic receptors?
Ligand gated ion channels.... receptor for Ach
47
What is another name for nicotinic receptors?
ionotrophic- fast synaptic transmission
48
Where would you find nicotinic Ach receptors?
Autonomic ganglia (sympathetic and parasympathetic) neuromuscular junctions and brain and spinal chord
49
What type of receptors are msucaranic Ach receptors?
G coupled protein receptors
50
What are muscaranic receptors also known as?
metabotrophic - slow synaptic transmission
51
Where would you find muscaranic Ach receptors?
postganglionic- parasympathetic sweat glands, sympathetic brain
52
What are inotropic receptors? and what do they do?
- 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
With inotropic receptors what happens if Cl- or K+ channels are opened?
- hyperpolarisation | - reduced membrane excitability (inhibitory neurotransmission)
54
What are metabotrophic receptors and what do they do?
- 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
What is an example of a metabotrophic receptor..?
a gland...
56
Does every cell respond in the same way to the same extracellular signal?
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
How are neurotransmitters removed from the synaptic cleft?
-enzymatic degradation and reuptake
58
What is the SNARE hypothesis?
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
What is the reflex arc made up of?
A sensory neurone and a motor neurone with a synapse in between
60
What is a pacinian corpuscle and what does it detect?
A mechano receptor in the skin, detects change in pressure due to stimulus
61
what is the difference between cardiac and neuronal AP?
cardiac is myogenic and has a longer duration | -cardiac has a Ca2+ initiation where as the neurones have a Na+ initiation
62
Look ver the paper provided during the LSRC
....
63
what do all post ganglionic innervations of the sympathetic NS use?... what is the exception
noradrenaline | -sweat glands and vascular smooth muscle wishing the skeletal muscle (use acetylcholine)
64
Examples of neurotransmitters of the CNS
Dopamine, serotonin, glycine. | None of these are in the autonomic region of the PNS
65
Adrenaline is released as a sympathetic response, and causes bronchiodilation, what does this achieve?
greater oxygen uptake | bronchioconstriction in response to Adrenaline would be detrimental to increasing the metabolic capacity of individual
66
Which hormones/neurotransmitter causes smooth muscle contractions?
Adrenaline
67
How does adrenaline trigger smooth muscle contraction?
peripheral blood vessels contract to increase flow to muscles and stem loss of blood from injury
68
Injury, vasoconstriction of vasodilation?
Constriction
69
What is myasthenia gravis?n nh
- 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
Which enzyme breaks down Acetylcholine?
AchE- Acetylcholine esterase
71
How would you treat a muscle contraction/sustained AP disorder such as myasthenia gravis?
- boost Ach levels-prevent breakdown using AchE inhibitors - immunosupression-corticosteriods - plasmapheresis - removing the anti-achR antibodies
72
where is choline acetyltransferase produced?
In the cell body of cholinergic neurones (then transported to axon terminal)
73
what does choline acetyltransferase do?
synthesises the formation of acetylcholine by catylzing the transfer of an acutely group from acetyl coA to a choline
74
What are catecholamines?
small organic molecules that contain an amine group and a benzene ring with 2 hydroxyl groups
75
Give 3 examples of catecholamine neurotransmitters
- adrenaline - noradrenaline - dopamine
76
adrenaline, noradrenaline and dopamine are synthesised from the same amino acid, which one?
tyrosine, which contains a benzene ring
77
which receptors cause skin pain?
noci receptors

ICS (11 decks)

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