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Neuronal Communication Flashcards

1
Q

What are the two examples of processes that use neuronal communication?

A
  • Homeostasis
  • Cell signalling
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2
Q

What is the nervous system responsible for?

A

detecting changes in the external and internal environment

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3
Q

What is meant by a stimulus?

A

changes in the internal and external environment

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4
Q

What is the role of a neurone?

A

transmit electrical impulses rapidly around the body, to respond to a stimulus

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5
Q

What are the structures of both sensory and motor neurones?

A
  • dendrites
  • cell body
  • nucleus
  • myelin sheath
  • axon
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6
Q

What are the three structures located in a relay neurone?

A
  • dendrite
  • nucleus
  • cell body
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7
Q

What is the function of the cell body in a neurone?

A

contains the nucleus, contains DNA

within the cytoplasm there are large quantities of mitochondria and E.R, which are involved in the production of neurone transmitters

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8
Q

What is the function of a dendrite in a a neurone?

A

(info collectors) responsible for transmitting electrical impulses towards the cell body, may generate an output

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9
Q

What is the function of an axon in a neurone?

A

a singular, elongated nerve fibres that transmit impulses away from the cell body

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10
Q

What is the structure and function of a myelin sheath, in a neurone?

A

(acts as an electrical insulator), increases the speed of a neuronal signal
- made from layers of plasma membrane, with cells called SCHWANN CELLS
(produce these membrane layers by growing around the axon many times - each time one grows, a phospholipid layer is laid down)

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11
Q

What is the nervous system pathway?

A

receptor -> sensory neurone -> relay neurone -> motor neurone -> effector cell

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12
Q

What is the structure of a sensory neurone? (what direction does info travel in)

A

(information from receptors, sent to the CNS)

  • have one dendron - carries the impulse to cell body
  • have one axon - carries impulse away from the cell body
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13
Q

What is the structure of the relay neurone? (what direction does the info travel in)`

A

(transmit impulses between neurones )

  • may have short axons and dendrons
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14
Q

What is the structure of a motor neurone? (what direction does info travel in)

A

(info from the CNS to the effector cell)

  • one long axon, many short dendrites
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15
Q

What are the Nodes of Ranvier, and where are they located?

A

gaps between adjacent SCHWANN CELLS, creates a gap in between the myelin sheath

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16
Q

What is the function of sensory neurones?

A
  • they are specific to a single type of stimulus
  • act as a transducer
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17
Q

What is meant by transducer, and which type of neurone is a transducer?

A

one that converts a stimulus into a nerve impulse, by creating an action potential

(sensory neurone)

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18
Q

What are the 4 main types of sensory receptor in animals?

A
  1. Mechanoreceptors
  2. Chemoreceptors
  3. Thermoreceptors
  4. Photoreceptors
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19
Q

What stimulus do Mechanoreceptors detect and what is an example of a type of cell?

A

stimulus = movement/pressure

cell = Pacinian Corpuscle

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20
Q

What is the function and where are the Pacinian Corpuscle located?

A

located on the skin, and found within the joints
specific sensory receptors that detect pressure change

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21
Q

What is the structure of a Pacinian Corpuscle?

A

nerve ending is surrounded by layers of connective tissue with viscous gel in between the connective tissue
- outside that there is a capsule and a blood capillary

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22
Q

What is found in the membrane of the neurone within a Pacinian Corpuscle cell?

A

there is a sodium ion channel (responsible for transporting sodium across the membrane)
called = stretch mediated sodium channel, because when the channel changes shape, the permeability of the membrane also changes

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23
Q

How does the Pacinian Corpuscle convert mechanical pressure into a nerve impulse?

A
  1. in resting state = stretch mediated sodium ion channels are too narrow to allow sodium through, the neurone has resting potential
  2. When pressure is applied, the cell changes shape, causing the membrane of the neurone to stretch
  3. When it stretches the sodium ion channels present widen, allowing sodium ions to diffuse into the neurone
  4. Influx of ions, changes the potential of the membrane - becomes depolarised (has a generator potential)
  5. The generator potential creates an action potential (nerve impulse passed onto the next neurone
  6. action potential transmitted to CNS
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24
Q

What is meant by resting ptential?

A

when the nerve is not sending a signal

the outside of the membrane is more positively charged that the inside (which is more negatively charged)

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25
What does it mean if the membrane is polarised?
the outside of the membrane is more negatively charged than the inside - there is a potential difference across it (about 70mv)
26
How do membranes become polarised?
- sodium/potassium pump in the plasma membrane are pumping sodium ions out the cell, using ATP - it pumps (actively) out 3 sodium ions for every 2 potassium ions that diffuse in
27
What is the sodium potassium pump?
some intrinsic proteins actively transport potassium ions into the axon and sodium ions out of the axon
28
How do nerve impulses start?
- neurones are stimulated by receptor cells/another neurone - stimulus causes the sodium channels to open - causes sodium ions to flow into cell - causes a depolarisation of the membrane potential affects the voltage gated sodium channels nearby and starts an action potential
29
What are the seven stages on the action potential graph? (in order, just draw it out)
1. resting potential 2. depolarisation 3. threshold (-5mv) 4. action potential 5. repolarisation 6. hyperpolarisation (refractory period) 7. repolarisation
30
What is meant by the refractory period?
when the voltage gated sodium ion channels remain closed, this means that the action potential can only be transmitted in one direction
31
In terms of the surface membrane of the neurone, what is happening during the resting potential?
the cell is more positively on the outside and more negatively charged on the inside (-60mv) the sodium - potassium pump is working -> pumps 2 sodium ions out and 2 potassium ions in
32
In terms of the surface membrane of the neurone what is happening during depolarisation?
the voltage gates sodium ions remain open, so sodium is actively being transported inside the neurone the potassium channels close this means that the outside of the neurone becomes more negative on the outside, energy of stimulus triggers the opening of more sodium ion channels
33
In terms of the surface membrane of the neurone what is happening when the threshold is reached (-55mv)?
(positive feedback loop) more voltage gated sodium ion channels open more ions diffuse into the axon to reach the Acton potential
34
In terms of the surface membrane of the neurone what happens when the action potential is reached? (+40mv)
The voltage gates sodium ion channels close and the potassium ion channels open
35
In terms of the surface membrane of the neurone what happens during repolarisation and hyperpolarisation?
-> reduces the charge resulting in the outside of the axon to become more positive hyper = more negative than when it was at resting potential (leads to a refractory period) The sodium ion channels are closed the potassium ion channels are open (AND DIFFUSE OUT OF THE AXON)
36
In terms of the surface membrane of the neurone what happens when it is repolarised?
it always repolarised to resting potential (sodium-potassium pump) same as the resting potential, with the pump axon = repolarised
37
What type of neurone generates an action potential, the way shown on the graph? (with the sodium - potassium pump)
A NON - MYELINATED NEURONE
38
In what type of neurone is an action potential generated via saltatory conduction?
MYELINATED NEURONE
39
What are the key differences between myelinated and non myelinated neurones?
myelinated = - quicker - longer - used in movements non-myelinated = - slower - shorter - still have schwann cells
40
What are the three stages of saltatory conduction?
(draw diagram) 1. sodium ions pass through the protein channels (voltage gated sodium ion channels open) 2. longer localised circuits therefore arise between adjacent nodes 3. action potential then 'jumps' from one node to another
41
How do depolarisation and repolarisation occur during saltatory conduction?
Depolarisation of the axon membrane can only occur at the nodes of Ranvier, where no myelin is present Repolarisation uses ATP in the sodium pump, so this reduces the amount of repolarisation needed
42
What are the two other factors that affect the speed at which an action potential travels?
1. axon diameter 2. temperature
43
How does the axon diameter of a neurone affect the speed at which an action potential travels?
bigger the diameter, the faster the impulse is transmitted (less resistance to the flow of 90ns in the cytoplasm)
44
How does the temperature of a neuron affect the speed at which an action potential travels?
increased temp = faster nerve impulse (40 degrees) any higher sodium potassium pump will denature
45
What is a synapse?
junction between two neurones
46
What is the purpose of a synapse?
- information sent between neurones - can pass across neurotransmitters -new action potential triggered in post synaptic neurone
47
What is meant by a presynaptic neurone?
neurone along which the impulse arrived
48
What is meant by post synaptic neurone?
neurone which receives the impulse e.g. neurotransmitters
49
What is meant by the synaptic cleft?
The gap which separates the axon from one neurone from the dendrite of the next (approx 20 - 30nm)
50
What is meant by the synaptic knob?
the swollen end of the presynaptic neurone, it contains many mitochondria and large amounts of endoplasmic reticulum to enable it to manufacture neurotransmitters
51
What is meant by synaptic vesicles?
versicles containing neurotransmitters, fuse with presynaptic membrane and release the contents into the synaptic cleft
52
What is meant by neurotransmitter receptors?
receptor molecule that NT binds to in post synaptic membrane
53
What is meant by a cholinergic synpase?
Any synapse that uses acetylcholine as a neurotransmitter
54
How do neurotransmitters diffuse across the synaptic cleft (between pre and postsynaptic neurone) to generate an action potential?, Only name the 6 stages.
Step 1: Calcium channels open Step 2: Neurotransmitter release Step 3: Sodium ion channels Step 4: Depolarisation in post synaptic neurone Step 5: Acetylcholinesterase (hydrolytic enzyme Step 6: Remaking Acetylcholine
55
What happens in Step 1: Calcium channels open, in synapse transmission?
- incoming action potential causes depolarisation (a diff in charge on each side of the membrane, more + on outside) in the synaptic knob causes calcium ion channels to open, CA+ floods into synaptic knob
56
What happens in Step 2: Neurotransmitter release, in synapse transmission?
- the influx of calcium ions causes synaptic vesicles to fuse with presynaptic membrane - this releases NT into cleft by exocytosis
57
What happens in Step 3: Sodium ion channels, in synapse transmission?
- neurotransmitter (acetylcholine) is released into the synaptic cleft - acetylcholine binds to the receptor site on the sodium ion channels - sodium ion channels open (when NT joins there is a conformational change - shape change - that opens the channel
58
What happens in Step 4: Depolarisation in the post synaptic neurone, in synapse transmission?
- must be above action potential threshold value (-55mv) - if threshold is reached a new action potential is sent along the axon on post-synaptic neurone
59
What happens in Step 5: Acetylcholinesterase (hydrolytic enzyme), in synapse transmission?
this breaks up acetylcholine into acetyl (ethanoic acid) and choline
60
What happens in Step 6: Remaking Acetylcholine, in synapse transmission?
- Acetyl and choline diffuse back into presynaptic neurone - ATP released by mitochondria is used to recombine the two, recycling it - stored in the synaptic vesicles for further use - more acetylcholine can be made in the S.E.R - sodium ions, in the post synaptic neurones close due to the absence of acetylcholine at their receptor sites
61
What are the two types of neurotransmitter?
1.excitatory 2.inhibitory
62
What is an excitatory neurotransmitter?
results in depolarisation, of post synaptic neurone, when threshold is reached, action potential triggered
63
What is an inhibitory neurotransmitter
results in hyperpolarisation of post synaptic neurone, prevents action potential being triggered
64
How are synapses unidirectional?
- lots of different impulses can combine at a synapse - allows multiple stimuli from different receptors to interact to produce a single response
65
What is summation?
Enables a build up of neurotransmitters in the synapse to generate an action potential
66
What are the two types of summation?
1. Spatial 2. Temporal
67
What happens in spatial summation?
when a number of presynaptic neurones connect to one postsynaptic neurone - each neurone releases NT, which build up to a high enough level to trigger an action potential in a single postsyanptic neurone
68
What happens in temporal summation?
A single presynaptic neurone releases NT as a result of an action potential several times, over a short time = builds up, until quantity is sufficient to trigger an action potential

Biology Kireth (17 decks)

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