functions of neurons; conduction of nerve impulses Flashcards

1
Q

Function of neurons

A

receive stimulus, covert to electrical signal then conducted down axon to specific effector

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2
Q

what 2 types of electric signals does the neurons communicate with?

A

graded potentials; local membrane changes only

action potentials; travel long distances

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3
Q

ion channels.

explain non gated (leak) channels

A

alternate between open and closed

more K+ leak channels

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4
Q

ion channels

explain gated channels
3 types

A

open and close in response to stimulus

ligand gated (respond to chemical stimulus)

mechanically gates (respond t mechanical stimulus - pressures)

voltage gated (respond to change in membrane potential - voltage)

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5
Q

Resting membrane potential.

exists because of a small build up of ? ions inside membrane

equal build up of ? ions in the ECF

sepeattion of electrical charges is form of ?

what is neurons resting membrane potential?

A

-ve

+ve

potential energy

-70mV (inside cell is more -ve, relative to outside = polarised)

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6
Q

3 factors contributing to negative resting membrane potential

A

unequal distribution of ions across membrane - mediated by K+ leak channels

Anions (-ve charged ion) can’t exit cell

Na+/K+ ATPase expesl 3 Na+ ions for every 2 K+ ions transported into cell

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7
Q

Graded potential

definition

what is hyperpolrised?
what is depolarised?

A

small deviation from resting membrane potential of -70 mV

inside has become more -ve

inside has becomes less -ve (more +)

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8
Q

2 types of graded potential

A

Post synaptic (occurs in dendrites or cell body - response to neurotransmitters)

receptor / generator (occur in sensory neurons - response to sensory receptor stimulation)

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9
Q

Graded potential stimulus strength and summation

describe summation

A

summation occurs when 2 or more graded potentials add together to becomes lager in amplitude

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10
Q

Action potential

describe

how is it achieved?

A

series of rapidly occurring events that change and then restore the membrane potential of a neuronal membrane

opening / closing sequence of voltage gates ion channels (Na+ in depolarisation, K+ out repolarisation

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11
Q

Resting state
-70mV > -55mV

all voltage-gated Na+ channels are in the resting state and the voltage gated K+ channels are open or closed?

A

closed

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12
Q

Graded potential phase

A

mechanical / chemical stimulus activates a ligand gated ion channels that result in depolarising GP

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13
Q

Depolarising phase
-55mV > +30mV
voltage gates Na+ channels do what and where does Na+ rush?

the threshold reached, activated gate opens and Na+ does what?

A

open
into cell

enters

change in membrane potential up to +30mV

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14
Q

Repolarising phase

voltage gates Na+ channels inactivating

voltage gated K+ channels do what?

K+ does what?

A

open

flows out

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15
Q

after hyper polarising phase

voltage gated K+ channels are open

voltage gated Na+ channels are in resting state

What does K+ do?

voltaged gates K+ channels open or close?

A

K+ continues to leave cell

close

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16
Q

define refractory period of action potential

A

period of time during which neuron can not generate another action potential

17
Q

what is absolute refraction period?

A

even very strong stimulus will not ring another AP

inactivated voltage gates Na+ channels must return to resting state before reopening

18
Q

what is relative refractory period?

A

supra-threshold stimulus only will be able to start an AP

voltage gated K+ channels are still open but voltage gated Na+ channels have closed

19
Q

Propagation of Action potential.

there are 2 types

A

action potential spreads (propagates) over the surface of axon membrane

continuous

saltatory

20
Q

continuous conduction

where do ions flow?

what does it do to the adjacent portion?

A

voltage gated ion channels in adjacent settings

step by step depolarisation of each adjacent portion

21
Q

saltatory conduction

where does depolarisation occur?

where does the current flow?

A

nodes of ranvier - high density of voltage gated ion channels

current carried by ions flow through ECF from node to node

22
Q

speed of impulse propagation

3 factors
3 axon types

A

myelination

temperature

axon diameter

A fibres
B fibres
C fibres

23
Q

Synapse
definition
2 types

A

functional junction between neurons or between a natron and an effector (muscle or gland)

electrical or chemical

24
Q

Electrical synapse

structure
function

A

AP spreads to next cell through gap junctions

faster two way transmission

cardiac muscle, visceral smooth muscle, brain

25
Chemical synapse
one way information transfer from pre to post synaptic neuron or effector
26
Excitatory postsynaptic potentials occurs as a result of depolarisation of the what membrane? brings membrane further or closer to threshold? postsynaptic membrane becomes more or less excitable?
postsynaptic membrane closer more
27
Inhibitory postsynaptic potential occurs as a result of ? of the postsynaptic membrane brings membrane further or closer from threshold? Postsynaptic membrane becomes more or less excitable?
Hyperpolarisation further less excitable
28
Neurotransmitters Avetylcholine (ACh) released by? 3 function 2 action inactivated by
many PNS neurons and some CNS learning and memory activated muscle action awakening and attention excitatory on NMJ inhibitory at other synapses e.g heart inactivated by AChE
29
dopamine released by function action
CNS neurons regulates skeletal muscle tone, pleasure and addiction inhibitory
30
Norepinephrine (NE) released by function action
CNS & ANS neurons regulates moods, dreaming, awakening from sleep excitatory & inhibitory
31
Epinephrine released by function action
CNS & ANS neurons increased blood flow and heart rate, awareness excitatory & inhibitory
32
Serotonin released by function action
CNS neurons cells in GI tract control of mood sensory perception temperature and appetite regulation induction of sleep inhibitory
33
Amino acids Glutamate GABA released by function action
Glutamate CNS neurons learning and memory regulated development of new nerve contacts excitatory GABA CNS neurons reduce activity of neurons in CNS contribute to muscle control behaviour, cognition inhibitory
34
Endorphins released by function action
CNS and PNS potent analgesic (pain relieving) improved memory and learning pleasure and euphoria generally inhibitory