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BIO > Neuronal Communication > Flashcards

Neuronal Communication Flashcards

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Biology 101 flashcards
1
Q

What are sensory receptors?

A

Specialised cells that can detect stimuli.

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2
Q

What is a stimulus?

A

Detectable changes in energy.

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3
Q

What is transduction?

A

The process by which a receptor converts a stimulus into a nerve impulse.

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4
Q

What is a pacinian corpuscle?

A

A mechanoreceptor, detects pressure.

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5
Q

What is the structure of a pacinian corpuscle?

A

A sensory nerve ending wrapped in layers of connective tissue called lamellae.

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6
Q

How does a pacinian corpuscle produce a generator potential?

A

When a pacinian corpuscle is stimulated, the lamellae are deformed and press on the sensory nerve ending. This causes the stretch mediated sodium ion channels to become deformed and open. The influx of sodium ions creates a generator potential.

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7
Q

What thresholds must be reached for a pacinian corpuscle to create a nervous impulse?

A

The stimulus must be above a certain threshold level in order for the stretch mediated sodium ion channels to open causing a generator potential.
The generator potential must be above a certain threshold level to trigger an action potential in the sensory neuron.

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8
Q

What are the two types of cell the nervous system is made from?

A

Neuroglia and Neurones.

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9
Q

What is the role of neuroglia (glial cells)?

A

Packing cells, supporting the neurons, such as performing metabolic functions.

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10
Q

What is the basic role of neurones?

A

To conduct nervous impulses.

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11
Q

What are the 3 types of neuron in the nervous system?

What are their roles?

A

Sensory (from a receptor).
Relay (between sensory and motor).
Motor (to an effector).

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12
Q

What is the structure of a motor neuron?

A

Long myelinated axon with a cell body at one end with dendrites.

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13
Q

What is the structure of a sensory neuron?

A

Myelinated axon and dendron with cell body in the middle.

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14
Q

What is the myelin sheath?

A

Myelin is a fatty material produced by shwann cells to act as an insulator.
Allows the impulse to “jump” between nodes of ranvier, increasing transmission speed.

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15
Q

What is an example of a neuron that is adapted to be non-myelinated?

A

C-fibres.

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16
Q

What is an example of a neurological condition that causes the thinning of the myelin sheath?

A

Multiple sclerosis.

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17
Q

Which way does the impulse travel in a neuron?

A

Down the axon away from the cell body.

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18
Q

What is the resting potential of a neuron?

A

The potential difference in the ion charge across a neuron membrane when it is not transmitting an impulse.
Around -70mV

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19
Q

What is an action potential?

A

Depolarisation of the neuron cell membrane (reversal of the potential difference).
From -70mV to +40mV.

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20
Q

What ions are involved in the depolarisation of a neuron?

A

Na+ and K+

Sodium and Potassium

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21
Q

What are the three different types of ion channel/pump in the neuron membrane?

A

Na+/K+ active transport pumps. (carrier protein)
Na+/K+ voltage-gated channels. (channel proteins)
Na+/K+ leak channels. (channel proteins).

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22
Q

What effect do the Na+/K+ pumps have?

A

3Na+ transported out while 2K+ transported in.

This results in the neuron having an overall negative charge, polarising the membrane.

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23
Q

When are the voltage-gated channels open and what effect do they have?

A

Open and close during an action potential.
Na+ channels being open causes depolarisation.
K+ channels being open causes repolarisation.

24
Q

What is the effect of the leak channels in the neuron membrane?

A

Allow the passive diffusion of Na+ and K+ across the membrane, regulating membrane potential.
Na+ moves in and K+ moves out.
However, the plasma membrane is more permeable to K+ than Na+, so the resting potential is maintained.

25
Q

What causes depolarisation?

A

Sodium ion channels open due to a stimulus, if this causes the membrane potential to rise enough to open the voltage-gated Na+ channels (-40mv), the threshold potential is said to have been reached and the membrane fully depolarises.

26
Q

What happens during depolarisation?

A

Voltage-gated sodium ion channels open and sodium ion flood the neuron depolarising the membrane up to +40mV.

27
Q

How does repolarisation happen?

A

When the membrane has depolarised, the voltage-gated sodium ion channels close, and the voltage-gated potassium ion channels open.
This causes K+ ions to flood out of the neuron, reducing the membrane potential in repolarisation.

28
Q

What is hyperpolarisation?

A

During repolarisation, the membrane potential overshoots slightly, becoming lower than the resting potential (around -75mV).
The resting potential is soon restored after the voltage-gated potassium ion channels are closed.

29
Q

How long does the whole process of an action potential last?

A

4-6ms

30
Q

What is the refractory period after an action potential?

A

For a short period, a second action potential cannot take place as the membrane must reach resting potential and also, Na+ channels cannot immediately reopen.

31
Q

What is a local circuit?

A

How action potentials are transmitted along the neuron.

The movement of ions along the neurone caused by an increase in the concentration of ions at one point.

32
Q

What is the role of the myelin sheath in the transmission of an action potential?

A

Myelin prevents the movement of ions across the neuron membrane at the parts of the axon it covers, so depolarization only happens at the nodes of ranvier.

33
Q

How does the electric impulse move between the nodes of ranvier?

A

The charge moves by local current only (diffusion of Na+). No action potentials are formed in the myelin covered length of the neuron.

34
Q

What is the name for how the action potential “jumps” from each node to the next?

A

Saltatory conduction.

35
Q

What are the benefits of myelination?

A

Neurons are insulated from one another, so an action potential travels down a single neuron as it should.
Speeds up nerve impulses due to saltatory conduction.

36
Q

What other factors can increase the speed of impulse transmission?

A

Wider diameter axon. (less resistance to the flow of ions in local circuits)
Increasing temperature. (ions diffuse at a faster rate)

37
Q

What are the 4 purposes of synapses?

A

Unidirectionality.
Removing low level stimulation.
Forming nerve networks.
Learning and memory.

38
Q

How do synapses ensure unidirectionality?

A

Neurotransmitters can only be released from the presynaptic membrane, and receptors are only present on the postsynaptic membrane.

39
Q

How do synapses remove low level stimulation?

A

Weak action potentials will not stimulate enough vesicles to be released to generate an action potential in the next neuron as the threshold is not reached.

40
Q

How do synapses allow nerve networks?

A

One neuron can join to many other neurons as each neuron has many synaptic knobs.

41
Q

How do synapses allow learning and memory?

A

They form specific pathways joining networks of neurons together in the brain.

42
Q

What is the structure of a synapse?

A

Presynaptic neuron with a synaptic bulb.
Synaptic cleft.
Postsynaptic neuron.

43
Q

How is a nervous impulse transmitted across a synapse?

A

Through the use of neurotransmitters.

44
Q

What is the most common neurotransmitter and what is the name for the type of synapse that uses that chemical?

A

Acetylcholine.

Cholinergic synapse.

45
Q

What effect does the arrival of an action potential have at the end of the presynaptic neuron?

A

Causes calcium ion (Ca2+) channels to open letting Ca2+ into the synaptic bulb.

46
Q

What effect do calcium ions have in the synaptic bulb?

A

Causes synaptic vesicles to fuse with the presynaptic membrane, releasing acetylcholine into the synaptic cleft (exocytosis).

47
Q

What happens in the synapse after the neurotransmitter (acetylcholine) is released into the synaptic cleft?

A

Acetylcholine binds to receptor sites on sodium ion channels in the postsynaptic membrane. This causes Na+ to diffuse in following a concentration gradient.

48
Q

What must happen in the synapse for a new impulse to be created in the postsynaptic neuron?

A

The excitatory post-synaptic potential must be above a certain threshold.

49
Q

What happens in the cholinergic synapse after the acetylcholine has acted?

A

The acetylcholine is broken down in the cleft by the enzyme acetylcholinesterase to form acetate and choline. These products are then reabsorbed into the presynaptic neuron and reformed into acetylcholine using ATP.

50
Q

How do agonistic drugs affect neurons at synapses?

A

Increase transmission.

e.g: nicotine (stimulants)

51
Q

How do antagonistic drugs affect neurons at synapses?

A

Block transmission.

e.g: alcohol (depressants)

52
Q

What is summation at a synapse?

A

Where many low-level stimuli join together to produce an action potential in the post synaptic neuron by collectively reaching the excitatory post-synaptic potential.

53
Q

What is a temporal summation at a synapse?

A

One neuron releases multiple vesicles over an amount of time and the neurotransmitter in the cleft builds up to reach the excitatory post-synaptic potential.

54
Q

What is a spacial summation at a synapse?

A

Multiple synaptic bulbs collectively produce enough of the neurotransmitter to generate an action potential in the postsynaptic neuron.

55
Q

What is acclimatisation at a synapse?

A

After multiple signals, the synaptic knob no longer responds to the arriving action potential due to a lack of acetylcholine vesicles.

56
Q

What is the purpose of the refractory period?

A

Ensures the unidirectionality of impulse transmission.

BIO (33 decks)

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