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Biology > 5.3 - Neuronal Communication > Flashcards

5.3 - Neuronal Communication Flashcards

1
Q

What are neurones ?

A
  • Specialised animal cells that pass on nerve impulses.
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2
Q

What are the three types of neurons ?

A
  • Sensory neurone
  • Motor neurone
  • Relay neurone
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3
Q

What are sensory neurone ?

A
  • Myelinated neurone
  • ## Pass nervous impulses from Receptors to CNS
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4
Q

What are motor neurones ?

A
  • Myelinated neurone
  • Pass nervous impulses from CNS to muscles/glands.
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5
Q

What are relay neurone ?

A
  • Non-myelinated neurone
  • Connect sensory and motor neurones
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6
Q

What is the structure of neurone ?

A
  • All have a cell body which contains extensions called dendrites and an axon
  • Axon which ends in axon terminal which form synapses with other neurones or muscles
  • Some neurones have a myelin sheath on their dendrites which are formed from Schwann cells with lipid rich cell membranes.
  • Gaps in myelin sheath have Node oof Ranvier
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7
Q

What are sensory receptors?

A

Specialised cells that detect the stimulus

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8
Q

What are the functions of sensory receptors?

A

1) only respond to a specific stimulus e.g mechanical pressure
2) act as transducers - convert stimulus into nerve impulse

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9
Q

Where are examples of where sensory receptors can be found in the body?

A
  • Eye
  • Skin
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10
Q

What is an example of sensory receptors and where is it found ?

A
  • Pacinian Corpuscle
  • Found deep into the skin of animals
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11
Q

What is the structure of the Pacinian Corpuscle ?

A
  • it has a single sensory neuron in its centre
  • ## It is surrounded by a tissue layers called lamellae
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12
Q

What is the function of the Pacinian Corpuscle ?

A
  • only responds to mechanical pressure from the environment for example - like when something touches the skin.
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13
Q

Explain what happens in the pacinian corpuscle

A
  • There are stretch mediated Na+ channels in the membrane
  • transport proteins that open when membrane is stretched or put under mechanical pressure
  • The resulting influx in sodium ions causes membrane to be depolarised.
  • This is referred to as a generator potential - multiple
  • When a threshold is reached action potential is triggered and reached to sensory neurones axon and sent to CNS
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14
Q

What is the biggest nerve?

A

The sciatic nerve

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15
Q

Define what is meant by the term ‘nerve impulse’.

A

A nerve impulse is a moving area of charge.

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16
Q

How does the nerve impulse move ?

A
  • In one direction (RIP LIAM)
  • Nerve impulses always travel in one direction, which are away from a/an Receptor and towards a/an effector .
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17
Q

How is the neurones cell membrane in its resting state ?

A
  • In a neurone’s resting state (when it’s not being stimulated), the outside of the membrane is positively charged compared to the inside. This is because there a more positive ions outside the cell than inside.
    So the membrane is polarised - there’s a difference in charge. The voltage acr the membrane when it’s at rest is called the resting potential — it’s about -70 mV
    The resting potential is created and maintained by sodium-potassium pumps and potassium ion channels in a neurone’s membrane:

The sodium-potassium pumps move sodium ions out of the neurone, but the membrane isn’t permeable to sodium ions, so they can’t diffuse back in. This creates a sodium ion electrochemical gradient (a concentration gradient of ions) because there are more positive sodium ions outside the cell than inside.
The sodium-potassium pumps also move potassium ions in to the neurone, but the membrane is permeable to potassium ions so they diffuse back out through potassium ion channels.
This makes the outside of the cell positively charged compared to the inside.

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18
Q

How do neurone cell membranes become depolarised ?

A
  • When they are. Stimulated
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19
Q

How do sodium potassium ions move across the membrane?

A

-Through ion channels

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20
Q

What is the difference in concentration and charge in the membrane?

A

The electrochemical gradient

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21
Q

What happpens sodium ions moves into the axon ?

A
  • With every sodium that moves into the axon an additional positive charge is added this means that the overall charge inside the axon slowly becomes positive
22
Q

What happens when a potassium ions moves out of the axon ?

A
  • A positive charge is removed. This means that the overall charge inside the axon slowly becomes less positive.
23
Q

Why can sodium and potassium ions only cross the axon membrane through channel proteins, and not by simple diffusion?

A

They are polar
They are hydrophilic
They are charged
They are insoluble

24
Q

Explain sodium potassium pump

A
  • It is a cotransporter
  • It is a carrier protein
    -Transports them against their electrochemical gradient.
  • The sodium-potassium pump is an example of active transport.
  • ## The sodium-potassium pump moves two potassium ions into the axon, and three sodium ions out of the axon.
25
Q

The sodium-potassium pump moves three sodium ions out of the axon while moving two potassium ions into the axon. What does this result in ?

A

As a result, the sodium-potassium pump maintains a more positive charge outside the axon, and a less positive charge inside the axon.

26
Q

How are they stimulated , what are the 5 steps ?

A

Stimulus
depolarisation
Repolarisation
hyper-polarisation
resting potential

27
Q

How are they stimulated , what are the 5 steps ?
(1)

A

a stimulus triggers sodium iron channels in the cell membrane to open if the stimulus is big enough it will trigger a rapid change in potential difference. This sequence of event is known as an action potential.
- step one stimulus – this excites the neuron cell membrane causing sodium iron channels to open the membrane becomes more permeable sodium so sodium ions diffuse into the neuron down the sodium ion electrochemical gradient. This makes the inside of the neuron less negative.

28
Q

How are they stimulated , what are the 5 steps ?
(2)

A
  • Depolarisation if the potential difference reaches the threshold around -50 5MV voltage gated sodium iron channels open more sodium ions diffuse into the neuron this is positive feedback
29
Q

How are they stimulated , what are the 5 steps ?
(3)

A

Repolarisation – at a potential difference of around +30 MV the sodium iron channels close and volt gated potassium iron channels open. The membrane is more permeable to potassium so potassium irons diffuse out of the neuron down the potassium iron concentration gradient. This starts to get the membrane back to its resting potential this is negative feedback.

30
Q

How are they stimulated , what are the 5 steps ?
(4)

A

Hyperpolarisation – potassium ion channels are slow a slow to close so there’s a slight overshoot with too many potassium irons diffuse upon the potential difference becomes more negative than the resting potential so i.e. less than -70 mV

31
Q

How are they stimulated , what are the 5 steps ?
(5)

A

Resting potential – the ion channels are reset. The sodium potassium pump returns the membrane to its resting potential and maintains it until the membranes excited by another stimulus.

32
Q

What happen after this (5 steps )?

A

-after an action potential the neuron cell membrane can’t be excited again straight away this is because the ion channels are recovering and they can’t be made to open – sodium iron channels are closed during repolarisation potassium ion channels are closed during hyperpolarisation this period of recovery is called refractory period

33
Q

How does the action potential move along the neuron?

A

It moves along the neuron as a wave of depolarisation when an action potential happens some of the sodium irons enter the neuron diffuse sideways.
This causes sodium ion channels in the next region of the neuron to open and the sodium ions diffuse into that part.
this causes a wave of depolarisation to travel along the new one. The wave moves away from the parts of the membrane in refractory period because these parts can’t fire an action potential

34
Q

What does the biggest stimulus cause?

A

This causes more frequent impulses
Once the threshold is reached an action potential always fire with the same change in voltage no matter how big the stimulus is
If the threshold isn’t reached an action potential won’t fire this is all or nothing nature of action
Potentials
A big stimulus won’t cause a bigger action, but it will cause them to fire more frequently so if the brain receives a high frequency action potential interprets this is a big stimulus and respond accordingly

35
Q

How do myelinated neurons affect the action potential?

A

Action potentials go faster in myelinated neurons
The myelin sheath is an electrical insulator
In myelinated neurones, depolarisation only happens at the nose of Ranvier
Sodium iron channels are concentrated at the nodes
In a neurone depolarisation only happens at the nodes of Ranvier
-The neurons cytoplasm conducts enough electrical charge to depolarise the next node to the impulse jumps from to node this is called saltatory conduction and it’s really fast
In a non- myelinated neurone, the impulse travels as a wave along the whole length of the axon membrane
This is slower than the saltatory conduction, although it’s pretty quick

36
Q

Explain how resting potential is established and maintained in a neurone

A

The sodium-potassium pump is involved in the establishment of resting potential. At resting potential, the inside of the axon is less positively charged than the outside. The sodium-potassium pump actively transports
3
sodium ions out of the axon for every
2
potassium ions in, so overall, there is a net movement of positive ions out of the axon. There are also carrier proteins in the membrane that pump sodium ions out of the axon. The axon membrane is relatively impermeable to sodium ions, since gated sodium channels are closed. So there is very little diffusion of sodium ions back into the axon. Also, there is diffusion of potassium ions out of the axon via potassium channels down its electrochemical gradient. Overall, this maintains a higher concentration of sodium ions outside the axon, which maintains resting potential.

37
Q

What is a synapse ?

A
  • A junction between a neuron and another neuron and an effective cell, e.g. a muscle or gland
38
Q

What is the synaptic cleft?

A

A tiny gap between the cells at synapse

39
Q

Draw and label a synapse

A

Did you get it correct?

40
Q

Explain synapse

A

The presynaptic neurone (the one before the synapse) has a swelling called a synaptic knob. This contains synaptic vesicles filled with
presynaptic
membrane
synaptic knob
postsynaptic membrane
chemicals called neurotransmitters.
4)
When an action potential reaches the end of a neurone it causes neurotransmitters to be released into the synaptic cleft.
They diffuse across to the postsynaptic membrane (the one after the synapse) and bind to specific receptors.
5)
When neurotransmitters bind to receptors they might trigger an
vesicle filled with
neurotransmitters
action potential (in a neurone), cause muscle contraction
synaptic cleft
receptors
(in a muscle cell), or cause a hormone to be secreted (from a gland cell).
Neurotransmitters are removed from the cleft so the response doesn’t keep happening, e.g. they’re taken back into the presynaptic neurone or they’re broken down by enzymes (and the products are taken into the neurone).
7) There are many different neurotransmitters, e.g. acetylcholine (ACh) and noradrenaline. Synapses that use acetylcholine are called cholinergic synapses. Their structure is exactly the same as in the diagram above.
They bind to receptors called cholinergic receptors, and they’re broken down by an enzyme called acetylcholinesterase (AChE).

41
Q

How do neurotransmitters transmit nerve impulses between neurons?

A

An action potential triggers and calcium influx
Calcium influx causes neurotransmitter release
The neurotransmitter triggers an action potential in the postsynaptic neuron

42
Q

Synapses can be excitatory or inhibitory , explain

A
  • At an excitatory synapse, neurotransmitters depolarise the postsynaptic membrane making it fire an action potential if the threshold is reached.
  • At an inhibitory synapse , when the neurotransmitters bind to receptors on the postsynaptic membrane, they hyper-polarise the membrane preventing an action potential from being fired.
43
Q

What is synaptic divergence ?

A
  • When one neurone connects to many neurones information can be dispersed to different parts of the body
44
Q

What s synaptic convergence ?

A
  • When many neurones connect to one neurone information can be amplified.
45
Q

What happens if a stimulus is weak?

A

If a stimulus is weak only a small amount of neurotransmitter will be released from renew on into the synaptic cleft. This might not be enough to excite the post synaptic membrane to the threshold level and stimulate an action potential.

46
Q

What is summation ?

A

Is where the effect of neurotransmitters can be combined

47
Q

What is summation ?

A

Is where the effect of neurotransmitters can be combined

48
Q

What are the types of summation ?

A
  • Spatial
  • Temporal
49
Q

What is spatial summation ?

A

Spatial summation
When neurones converge (see above), the small amount of neurotransmitter released from each neurone can be enough altogether to reach the threshold in the postsynaptic neurone and trigger an action potential.

50
Q

What is temporal summation ?

A

Temporal summation
Temporal summation is where two or more nerve impulses arrive in quick succession from the same presynaptic neurone. This makes an action potential more likely because more neurotransmitter is released into the synaptic cleft.

Biology (36 decks)

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