BP: Neurons and synaptic transmission Flashcards

(67 cards)

1
Q

Most of the brain is made up of cells called…

A

… glial cells and astrocytes.

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2
Q

What are neurons?

A

Specialised cells whose function is to move electrical impulses to and from the central nervous system (carry neural information throughout the body).

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3
Q

What gives the brain its impressive processing capabilities?

A

The highly complex neural networks within in.

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4
Q

What must neurons transmit?

A

Must transmit information both within the neuron and from one neuron to the next.

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5
Q

What do the dendrites of neurons receive?

A

Information from sensory receptors or other neurons.

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6
Q

What happens once the dendrites of neurons have received information from sensory receptors?

A

The information is passed down to the cell body and on to the axon.

It then travels down the length of the axon in the form of electrical signal known as an action potential.

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7
Q

What three types of neurons are there?

A
  • Sensory neurons
  • Relay neurons
  • Motor neurons
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8
Q

What things do neurons typically consist of?

A
  • A cell body
  • Dendrites
  • An axon
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9
Q

What are dendrites connected to?

A

The cell body, which is the control center of the neuron.

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10
Q

In a neuron, where does the impulse terminate?

A

The axon terminal.

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11
Q

In many nerves, what is there around the axon?

A

An insulating layer, known as a myelin sheath.

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12
Q

What is a myelin sheath?

A

An insulating layer that forms around the axon of a neuron.

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13
Q

Why is the myelin sheath important?

What happens when this is damaged?

A

It allows the nerve impulses to transmit more rapidly along the axon.

When damaged, the impulses slow down.

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14
Q

What is the length of a neuron?

A

It can vary from a few millimetres up to one metre.

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15
Q

What do sensory neurons do?

A

They carry nerve impulses from sensory receptors to the spinal cord and the brain.

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16
Q

What are sensory receptors?

A

Receptors for vision, taste, and touch etc.

All the senses.

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17
Q

Where are sensory receptors found?

A

They are found in various locations in the body.

For example in the eyes, ears tongue and skin.

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18
Q

What do sensory neurons convert?

A

They convert information from the sensory receptors into neural impulses, which can then travel to the brain.

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19
Q

What happens when impulses from the sensory neurons reach the brain?

A

They are translated into sensations of, for example, visual input, heat, pain etc. so that the organism can react appropriately.

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20
Q

If sensory information does not go to the brain, where does it go?

Why is it more beneficial for it to go there instead?

A

Some sensory neurons terminate at the spinal cord, and this allows reflex actions to occur quickly without the delay of sending the impulses to the brain.

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21
Q

What are relay neurons?

A

The most common type of neuron in the CNS.

They allow sensory and motor neurons to communicate with each other.

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22
Q

Where are relay neurons found?

A

They are only found in the brain or the spinal cord.

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23
Q

What does the term ‘motor neurons’ refer to?

A

To neurons located in the PNS that project their axons outside the PNS and directly or indirectly control muscles.

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24
Q

What do most motor neurons form?

A

Synapses with muscles to control their contractions

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25
When stimulated, what happens to the **motor neuron?**
It releases neurotransmitters that bind to receptors on the muscle and triggers a response which leads to muscle movement.
26
What happens when the **axon** of the **motor neuron fires?**
The muscle with which it has formed synapses with contracts.
27
What is **muscle relaxation** caused by?
Inhibition of the motor neuron.
28
How are **muscle contractions** formed? ## Footnote *What does their strength depend on?*
Formed when the axon of the motor neuron connected to the muscle fires. ## Footnote *The strength of the muscle contractions depends on the rate of firing of the axons of the motor neuron that control it.*
29
What is **an action potential?**
An electrical signal that travels down the axon of a neuron.
30
What must happen when an **action potential arrives at the terminal?** ## Footnote *How is this achieved?*
The action potential must be transferred to another neuron or to tissue. ## Footnote *To acheive this, the action potential must cross the synapse.*
31
What is a **neurotransmitter?**
A chemical substance that plays an important part in the workings of the nervous system by transmitting nerve impulses across a synapse.
32
What is a **synapse?**
The conjunction of the end of the axon or one neuron and the dendrite or cell body of another.
33
What does the **synapse** consist of?
* The end of the pre-synaptic neuron * Membrane of the postsynaptic neuron * The gap inbetween these two neurons
34
What is the **synaptic gap?**
The physical gap between the pre-synaptic and postsynaptic cell membranes.
35
**The physical gap between the pre-synaptic and postsynaptic cell membranes,** is known as what?
The synaptic gap.
36
What is at the **end of an axon of a nerve cell?**
A number of sacs known as synaptic vesicles.
37
What are **synaptic vesicles?**
The sacs at the end of an axon of a nerve cell.
38
What do **synaptic vesicles contain?**
Chemical messengers/neurotransmitters that assist in the transfer of the impulse across the synaptic gap.
39
What happens as the **action potential** reaches the **synaptic vesicles?**
Their contents are released through a process of exocytosis.
40
What is **exocytosis?**
The process of moving materials from within a nerve cell to the exterior of the cell (the synaptic gap).
41
Once the **neurotransmitter** is released, what happens to it?
It diffuses across the gap between the pre- and post synaptic neuron. Then, it binds to specialised receptors on the surface of the cell that recognise it and are activated.
42
Once **neurotransmitters** have activated **specialised** **receptors**, what happens?
The receptor molecules produce either excitatory or inhibitory effects on the postsynaptic neuron.
43
Describe the process of **synaptic transmission:**
* An action potential arrives at the terminal button at the end of the axon. * This causes the synaptic vesicles to release their contents through exocytosis. * Released neurotransmitters diffuse across the synaptic gap and bind to specialised receptors on the postsynaptic neuron. * These activated receptors produce either excitatory or inhibitory effects.
44
What is **synaptic transmission?**
Refers to the process by which a nerve impulse passes across the synaptic cleft from one neuron to another.
45
Where do **neurotransmitters diffuse?**
Across the synaptic gap, onto specialised receptors on the postsynaptic neuron.
46
In synaptic transmission, where are **specialised receptors found?**
On the postsynaptic neuron.
47
How long does the process of **synaptic transmission last?**
Only a fraction of a second
48
Where do the **effects** of synaptic transmission **terminate?**
The effects terminate at most synapses by a process called 're-uptake'.
49
Describe the process of **re-uptake:**
*Occurs after synaptic transmission.* The neurotransmitter is taken up again by the presynaptic neuron, where it is stored and made available for later release *(it is recycled)*.
50
(After synaptic transmission), what determines the **length** of the the **effects** on the postsynaptic neuron?
How quickly the neurotransmitters return to the presynaptic neuron - *the speed of re-uptake.* ## Footnote *The quicker they are taken back, the shorter the effects on the postsynaptic neuron.*
51
Explain how **some antidepressants** prolong the action of the neurotransmitter:
They inhibit the re-uptake process, so the neurotransmitters can not return to the pre-synaptic neuron.
52
Apart from re-uptake, what else can happen to **neurotransmitters?**
They can be 'turned off' after they have stimulated the postsynaptic neuron.
53
What can happen to **neurotransmitters** once they have stimulated the postsynaptic neuron?
* Re-uptake * Be 'turned off'
54
How are **neurotransmitters 'turned off'?**
Through the actions of enzymed produced by the body, which make the neurotransmitters ineffective.
55
What can **neurotransmitters** be **classified as?**
Excitatory or inhibitory in their action.
56
Give **examples** of **excitatory neurotransmitters:**
Acetylcholine and noradrenaline.
57
What do **excitatory neurotransmittors do?**
Increase the liklihood that an excitatory signal is sent to the postsynaptic cell, which is then more likely to fire.
58
Give **examples** of **inhibatory neurotransmitters:**
Serotonin and GABA.
59
What do **inhibitory neurotransmitters do?**
Decrease the liklihood that an excitatory signal is sent to the postsynaptic neuron, and so decrease the liklihood of the neuron firing.
60
What are **inhibitory neurotransmitters** generally responsible for?
Calming the mind and body, inducing sleep and filtering out unnecessary excitatory signals.
61
An **excitatory neurotransmitter** binding with a **postsynaptic neuron** causes **what**? ## Footnote *What does this result in?*
Causes an electrical change in the membrane of that cell. ## Footnote *This results in an excitatory postsynaptic potential (EPSP).*
62
What is an **EPSP?**
Excitatory post-synaptic potential.
63
What does an **EPSP** lead to?
An increased liklihood that the postsynaptic cell will fire.
64
An **inhibitory neurotransmitter** binding with a postsynaptic receptor, results in what?
An inhibitory postsynaptic potential (IPSP).
65
What will an **IPSP do?**
Make it less likely that the postsynaptic cell will fire.
66
What determines the **likelihood** of a cell firing?
The summation of IPSPs and EPSPs.
67
What is the difference between spatial and temporal summation?
* In spatial summation, large number of EPSPs are generated by different synapses on same postsynaptic neuron at the same time. * In temporal summation, large number of EPSPs are generated at the same synapse by a series of high-frequency action potentials on presynaptic neuron.