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BioH111 > functions of neurons; conduction of nerve impulses > Flashcards

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
Q

Chemical synapse

A

one way information transfer from pre to post synaptic neuron or effector

26
Q

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?

A

postsynaptic membrane

closer

more

27
Q

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?

A

Hyperpolarisation

further

less excitable

28
Q

Neurotransmitters

Avetylcholine (ACh)

released by?
3 function
2 action
inactivated by

A

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
Q

dopamine

released by
function
action

A

CNS neurons

regulates skeletal muscle tone, pleasure and addiction

inhibitory

30
Q

Norepinephrine (NE)

released by
function
action

A

CNS & ANS neurons

regulates moods, dreaming, awakening from sleep

excitatory & inhibitory

31
Q

Epinephrine

released by
function
action

A

CNS & ANS neurons

increased blood flow and heart rate, awareness

excitatory & inhibitory

32
Q

Serotonin

released by
function
action

A

CNS neurons
cells in GI tract

control of mood
sensory perception
temperature and appetite regulation
induction of sleep

inhibitory

33
Q

Amino acids

Glutamate
GABA

released by
function
action

A

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
Q

Endorphins

released by
function
action

A

CNS and PNS

potent analgesic (pain relieving)
improved memory and learning
pleasure and euphoria

generally inhibitory

BioH111 (15 decks)

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