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neuronal communication Flashcards

1
Q

why is communication needed

A

so animals and plants can respond to changes in external and internal environments and coordinate these activities between different organs in plant or animal

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2
Q

what is homeostasis

A

a constant internal environment which is needed for plants and animals as they have enzyme controlled reactions which require optimum conditions to work

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3
Q

internal changes example

A

ph
water potential
temperature
glucose levels

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4
Q

external changes example

A

temperature
humidity
sounds
light

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5
Q

communication style in plants vs animals

A

plants - chemical comm
animals- hormonal and neuronal

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6
Q

what is cell signalling in hormonal and neuronal

A

hormones which allow cells to communicate with eachother over long distance
nervous impulses between adjacent cells

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7
Q

receptors

A

detect a change

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8
Q

sensory receptors examples

A

photoreceptors
chemoreceptors
thermpreceptors
mechanoreceptors

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9
Q

sensory neurone drawing

A

detects change and passes info from receptors to cns

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10
Q

motor neurone drawing

A

passes info from cns to effector to cause response

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11
Q

relay neurone drawing

A

connects sensory and motor neurones

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12
Q

direction of impulse in neurones

A

dendrites to axon

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13
Q

cell body

A

contains nucleus surrounded by cytoplasm
in cytoplasm contains lots of endoplasmic reticulum and mitochondria to produce neurotransmitters

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14
Q

dendrons

A

short extensions
split into dendrites
electrical impulse towards cell body

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15
Q

axons

A

singular elongated nerve fibres
away from cell body
cylindrical and v narrow cytoplasm

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16
Q

myelinated neurones

A

speed up the speed of an impulse by acting as an electrical insulator
axon potential does not need to be regenerated here

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17
Q

how are myelinated neurones formed

A

by schwann cells producing layers of membrane around axon

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18
Q

what are the small gaps between schwann cells called

A

nodes of ranvier

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19
Q

difference between dendron and axon

A

dendron is towards cell body and axon is away

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20
Q

what does a sensory receptors do

A

converts stimulus into a nervous impulse

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21
Q

what are the 2 main features of a sensory receptor

A

specific to single type of stimulus
act as a transfucer

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22
Q

what is a transducer

A

converts one type of signal to another

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23
Q

mechanoreceptor

A

pressure and movement
found on skin
example is pacinian corpuscle

24
Q

where is pacinian corpuscle found

A

deep in skin and joints
abundant in fingers and soles of feet

25
how does pacinian corpuscle work
normal stage - stretch mediated Na+ channels are narrow and so no movement of Na+. this is resting potential pressure applied - membrane surrounding neurone stretches as lamellae is deformed stretch mediated sodium ion channels widen so Na+ diffuses into the neurone influx of na+ changes potential then generator potential forms as it is depolarised generator potential converted into action potential
26
what is depolarisation
when it becomes less negative so normally a positive ion is entering like Na+
27
process of resting neurones
polarised -70mv sodium potassium pump - intrinsic protein 3 K+ in and 2Na+ out electrochemical gradient form and sodium wants to move in and potassium out however most sodium voltage gated channels are closed so they can’t move in and most potassium gated channels are open so potassium can move out therefore more positive charge is outside the axon and inside is more negative thus -70mv
28
action potential diagram
29
how does an action potential form
1. polarised at -60-70 mV. sodium potassium pump working. most sodium channels are closed. most potassium are open 2. stimulus causes Na+ voltage gated channels to open. Na+ moves into axon down electrochemical gradient. DEPOLARISED, creates generator potential 3. positive feedback. more sodium channels open more sodium in more positive axon 4. once 40 mv reached, Na+ voltage gated channels close and K+ channels open 5. K+ moved out so axon becomes more negative repolarisation 6. k+ continue to move out and becomes more negative than resting potential this is hyperpolarisation 7.k+ voltage gated channels close and sodium potassium pump takes it back to resting
30
when does the refractory period occur
after hyper polarisation this is the short period where action potential cannot be generated as ions are in the wrong place Na+ remain shut and allows sodium and potassium to be redistributed
31
why does voltage gated Na+ channels remain shut during refractory period
so there is no Na+ in axon important to prevent propagation backwards along neurone and action potential does not overlap
32
how does action potential move along neurone
when sodium ions are pumped into the axon they are attracted to the negative charge further along the neurone and also the conc gradient so diffuse along neurone and cause depolarisation of next section meanwhile sodium voltage gated channels of previous section close and k+ open so K+ can move out and cause repolarisation (more negative)
33
do all generator potentials lead to action potential
no as threshold needs to be met of -50 mv
34
how is a bright light or loud sound impulse generated
high intensity stimulus which causes large number of action potentials to be generated
35
what is saltatory conduction
process used for action potential to move along myelinated neurones quickly
36
process of saltatory conduction
repolarisation cannot occur in myelinated areas so jumps from node to node it is faster as everytime channels open and ions move it takes time and atp is required in repolarisation in sodium pump by reducing this impulse is much more quixk and efficient
37
what is a synapse
junction between two neurones
38
what is the gap between two neurones called
synaptic cleft
39
what neurones use ACH as a neurotransmitter
cholinergic neurones
40
process of synapse
action potential arrives at synaptic knob of pre synaptic neurone. this depolarisation causes calcium voltage gated channels to open so calcium ions move in and trigger snare proteins to contract and move vesicles containing the neurotransmitter to the pre synaptic membrane the vesicle fuses w the membrane during exocytosis to release the neurotransmitter in the synaptic cleft neurotransmitter diffuses across the synaptic cleft and binds to complementary receptors on the post synaptic membrane this causes excitatory post synaptic potential to form generator potential (action potential only formed if threshold is met) is neurotransmitter is ACH it binds to receptors in the sodium ion channels to cause sodium ions to move in and generate an action potential
41
what must happen to the neurotransmitter in the post synaptic neurone after action potential forms
must be removed or muscle will continue to contract as ACH will keep binding to sodium channels to they remain open and post synaptic membrane stays depolarised allows recycling if neurotransmitter
42
how is ACH broken down
acetylcholine is hydrolysed by acetylcholenesterase this breaks down ACH into an acetyl group (ethanoic acid) and choline this is taken back to the pre synaptic knob to reform using atp from the mitochondria
43
presynaptic bulb features
lots of mitochondria lots of SER to package neurotransmitter into vesicles lots of vesicles containing acetyl choline has voltage gated calcium channels
44
post synaptic membrane features
has sodium ion channels
45
role of synapse and how it does this
ensures impulse is unidirectional as only pre has neurotransmitter and only post has receptors filter out low level stimuli bcs it is low no action potential forms amplify low level stimuli through summation allow new neuronal pathways to occur
46
what is divergence
one neurone transmits impulse to several neurones
47
what is convergence
several neurone transmits impulse to one neurone
48
what happens if a stimulus is repeated several times
synapse may run out of neuro transmitters which means the person becomes habituated to the stimulus
49
what is summation
combined effect if anything sometimes one neurotransmitter is not enough so needs to be built up sufficiently for action potential to form
50
what is spatial summation
several pre to one post each releases high enough level in synapse to trigger action potential
51
what is temporal summation
when a single pre synaptic neurone releases neurotransmitter as a result of action potential several times over a short period builds up enough to form an action potential
52
what is an inhibitory post synaptic potential
some presynaptic neurones can be in inhibitory neurones and release neurotransmitters that promote the decrease of membrane potential it makes it harder to reach the threshold potential (involves chloride ions)
53
how can chloride ions be used to prevent an action potential
they are negatively charged so hyperpolarise the membrane and prevent depolarisation to reach threshold potential (takes it in opp direction more meg instead of pos)
54
effect of nicotine on synapse
mimics shape of neurotransmitters binds to receptors triggers action potential
55
effect of nerve gas in synapse
inhibits enzymes for breakdown of neurotransmitter so lots of stimulation loss of muscle control
56
effect of alcohol on synapse
binds to GABA receptors and changes shape so that binding of neurotransmitter increases

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