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IMS Nerves and muscles > 2 Neural signalling > Flashcards

2 Neural signalling Flashcards

(58 cards)

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1
Q

4 factors contribute to membrane resting potential

A
  1. intracellular charged proteins
  2. Na+/K+ pump
  3. sodium ions
  4. potassium ions
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2
Q

intracellular proteins

A

negative groups on surface = -ve

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3
Q

Na+/K+ pump

A

3 Na out
2 K in
= overall net negative p.d

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4
Q

sodium ions

membrane not very permeable to Na ions

A

membrane is only slightly permeable to Na+, so its effects on resting potential are small

net inward diffusion of Na+ slightly adds to the positivity of the cell = brings up to -65mV

both conc + electrical gradient pull Na+ in

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5
Q

potassium gradient

A

K+ out = conc gradient through channels

K+ in = electrical gradient pulls in due to -ve charge in cell

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6
Q

cell resting membrane potential =

A

close to but not equal to the potassium equilibrium potential as there is also a small leak for sodium ions

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7
Q

an action potential is…

away from cell body -> towards axon terminal

A

the means by which a neuron sends information down its axon, away from the cell body.
The action potential (spike/impulse) is an explosion of electrical activity that is created by a depolarising current

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8
Q

at RP

-65mV

A

all voltage gated Na+ and K+ channels closed

non-voltage dependent K+ channels are open

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9
Q

phases of AP 1

A

Na+ channels open
Na+ enters nerve cell
Membrane potential rises towards zero

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10
Q

phases of AP 2 = DEPOLARISATION

A

If threshold potential reached, voltage gated Na+ channels open
Na+ ions flow into cell
Action potential spike results

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11
Q

phases of AP 3 = REPOLARISATION

happen after reversal potential

A

Na+ channels close when Na+ equilibrium potential is reached
Voltage gated K+ channels open and K+ ions flow out of cell
Membrane potential reverses

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12
Q

phases of AP 4 = HYPERPOLARISATION

A

K+ ions continue to flow out of cell while Na+ channels closed
Hyperpolarisation results

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13
Q

AP = all or nothing principle

A

Membrane has to be depolarised beyond threshold for an AP to be generated
Further increase above threshold -> higher AP frequency not larger AP amplitude

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14
Q

absolute refractory period

= on graph the spike up to before hyperpolarisation

A

no further action potentials can be elicited = ensures AP propagation is one way

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15
Q

relative refractory period

= on graph starts at hyperpolarisation (end of repolarisation)

A

a larger stimulus can result in action potential

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16
Q

non-myelinated neuron AP conduction

A

wave along entire length of axon

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17
Q

myelinated neuron AP conduction

A

jumps along between Nodes of Ranvier = faster

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18
Q

Receptor potential caused by

A

detection of stimulus by receptor which then causes an AP is above threshold

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19
Q

stronger the RP

A

higher freq of AP generated

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20
Q

2 main sensory receptors in muscle

A
  1. muscle spindle

2. golgi tendon organ (GTO)

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21
Q

muscle spindle and GTO are both

A 
mechanoreceptors = pressure changes
proprioceptors = position and movement
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22
Q

muscle spindle stimulated when

A

muscle is passively stretched

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23
Q

GTO responds to

A

tension = stimulated when its associated muscle contracts or stretches in response to tension

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24
Q

muscle spindle found in

Study These Flashcards
A

muscle = modified muscle fibre

25
GTO found in
tendon
26
muscle spindle description
bundle of modified skeletal muscle fibres (intra-fusal fibres) enclosed in connective tissue capsule Intra-fusal fibres detect stretch/initiate reflex
27
GTO description
small bundles of tendon (collagen) fibres enclosed in a layered capsule with dendrites coiling between and around the fibres stimulated when the associated muscle contracts sets up reflex causing muscle to relax and removing stimulation
28
spindle is activated when
muscle is stretched passively = initates a reflex -> when muscle contracts and shortens it’s switched off
29
purpose of muscle spindle
prevent muscle from being overstretched
30
Knee-jerk reflex pathway = monosynaptic pathway as only 1 synapse
* Muscle stretch stretches spindle - increased discharge of sensory nerves * Increased firing of the motoneurone and the muscle contracts * NO SPINAL INTERNEURONE involved in this case. * Effect - reduce the stretch of the muscle. * Specific for the muscle stretched
31
GTO activated when
muscle is actively contracted (also at times when passively stretched)
32
purpose of GTO
tension detector that protects muscle against excess load
33
GTO inverse stretch reflex
Stimulated by excessive tension during muscle contraction or passive stretch Causes a reflex inhibition of the muscle ……relaxation
34
2 types of synapse
1. electrical | 2. chemical
35
electrical synapse
direct passage of current via ions flowing through gap junctions occurs in some parts of CNS
36
chemical synapse
release of vesicles containing chemical transmitter which has an effect on receptors on a target cell
37
gap junctions in electrical synapses pores between cells effectively mean that the cytoplasm of the two cells is in continuity
formed by channels called connexons connexons are made of protein molecules (connexins)
38
process of chemical transmission across synaptic cleft
- AP reaches axon terminal of presynaptic cell - triggers Ca 2+ entry into cell - triggers release of neurotransmitter from vesicles which fuse with presynaptic membrane - transmitter diffuses across the synaptic cleft - acts on specific receptors in the postsynaptic membrane (cell body or dendrite)
39
neurotransmitter =
a substance shown to be released by a neurone and have a physiological action on specific receptors on a target cell
40
neuromodulator =
a substance that is released and modifies the action of a transmitter, but doesn’t have a direct action itself
41
neuroactive substance =
a neutral term if a substance is known to have an effect in the CNS but its precise action is not known
42
different types of neurotransmitter substances
- amines - amino acids - peptides - purines (ATP)
43
7 major neurotransmitters
``` acetylcholine (ACh) norepinephrine dopamine gamma-aminobutyric acid (GABA) glutamate serotonin histamine ```
44
amine neurotransmitters...
``` Dopamine (DA) Noradrenaline (Norepinephrine)(NA) Adrenaline (Epinephrine) Histamine Serotonin ```
45
amino acid neurotransmitters...
Gamma-aminobutyric acid (GABA) Glutamate (Glu) Glycine (Gly)
46
peptide neurotransmitters...
``` Dynorphin Enkephalins Neuropeptide Y (NPY) Calcitonin gene-related peptide (CGRP) Somatostatin Galanin Substance P (SP) Thyrotropin-releasing hormone (TRH) Vasoactive intestinal polypeptide ```
47
Ionotropic receptor
= ion channels and comprise mostly 4 or 5 similar protein subunits arranged around a central pore that is normally closed to ion movements. When the transmitter (ligand) binds it causes a conformational change that briefly opens the pore and ions pass through to cause a rapid change in the resting potential of the underlying cytoplasm effect is to hyperpolarise or depolarise the postsynaptic cell
48
Metabotropic receptor
= single, long protein molecules, mostly crossing the cell membrane 7 times (7 trans-membrane domains) - no ion pore - ligand binds there is a conformational change in the molecule that causes the intracellular part to interact with a G-protein that then sets off a chain of intracellular events, that may include opening of ion channels
49
ionotropic vs metabotropic receptor response speed
ionotropic = faster
50
EPSP =
excitatory post-synaptic potential
51
IPSP =
inhibitory post-synaptic potential
52
binding of what causes EPSP
glutamate, ACh
53
binding of what causes IPSP
GABA, glycine
54
EPSP what ion influx
Na+ = depolarise cell towards threshold potential and may initiate an AP
55
IPSP what ion influx
Cl- = hyperpolarise cell and make may initiation of an AP less likely i.e. inhibition
56
purpose of EPSP
Decrease resting membrane potential (make more +ve) i.e. closer to threshold for depolarization EPSP's add up to produce threshold potential to generate AP
57
purpose of IPSP
Hyperpolarize post synaptic membrane Increase membrane potential i.e. moving it further from threshold for depolarization
58
affect of same postsynaptic neurone can receive numerous excitatory and inhibitory inputs to its cell body
net effect of these EPSPs and IPSPs that determine whether it will fire an action potential

IMS Nerves and muscles (5 decks)

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