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Biology module 5 > Neuronal control > Flashcards

Neuronal control Flashcards

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1
Q

Why are different proteins needed in a membrane to allow diffusion of different ions?

A

Each protein and ion have different shapes so they need to be specific and complementary to each other

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2
Q

What are the roles of sensory receptors?

A

They are specialised cells that transduce the energy of a stimulus into electrical energy in an action potential that is transmitted in a neurone.
Generate receptor potentials on stimulation
If a threshold intensity is reached, the sensory neurone, specific to that receptor is stimulated to generate an action potential.

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3
Q

What is a sensory receptor?

A

A cell, or group of cells, in which a change in the external or internal environment, produces a nerve impulse or action potential.

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4
Q

What must happen for an action potential to be produced?

A

The stimulus must be at or above a certain threshold level

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5
Q

What is a transducer?

A

All receptors are an example of transducers, they are adapted to detect changes in particular forms of energy.

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6
Q

What are the 3 types of neurone?

A

Sensory
Relay
Motor

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7
Q

What are the similarities between sensory and motor neurones?

A

Both have:

Cell body, nucleus, dendrites, axon, (myelin sheath/nodes of Ranvier)

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8
Q

What are the differences between sensory and motor neurones?

A

Only sensory neurones are in the peripheral nervous system and have dendrons, cell body in the middle of the axon, shorter axon. Impulse goes to relay neurone.
Only motor neurones are in the central nervous system and have largest axon, short dendrites, no dendrons and a cell body before the axon. Impulse goes to effector muscle/gland.

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9
Q

In what direction does the dendron/dendrites take the impulse?

A

Towards the cell body

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10
Q

In what direction does the axon take the impulse?

A

Away from the cell body

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11
Q

Structure of all neurones?

A

Long - impulse can travel far.
Plasma membrane lots of gated ion channels to control movement of Ca2+, K+ and Na+ ions.
Na+/K+ pumps use ATP for active transport.
Neurones maintain a potential difference across their plasma membrane.
Cell body has nucleus, mitochondria and ribosomes
Dendrites connect to other neurones
Axon carries impulse away from the cell body
surrounded by fatty layer to insulate, composed of schwann cells

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12
Q

Description of cell body

A

Contains nucleus surrounded by cytoplasm

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13
Q

Description of dendron

A

Short extensions that come from the cell body

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14
Q

Description of axon

A

Elongated nerve fibres - cylindrical and consists of narrow region of cytoplasm surrounded by plasma membrane

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15
Q

Description of myelin sheath

A

Layers of membrane around axon

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16
Q

Description of Nerve-muscle junction

A

Where a nerve joins a muscle

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17
Q

Description of dendrites

A

Small branches of dendrons

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18
Q

Function of cell body

A

Cytoplasm - ER / mitochondria produce neurotransmitters

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19
Q

Function of dendron

A

Divide into smaller branches called dendrites that transmit electrical impulses to cell body

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20
Q

Function of axon

A

Transmit impulse away from cell body

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21
Q

Function of myelin sheath

A

Speed up electrical impulse (insulate axon)

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22
Q

Function of nerve-muscle junction

A

Stimulates muscle fibres to contract

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23
Q

Function of dendrites

A

Transmits electrical impulses to cell body

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24
Q

What is myelin sheath made of?

A

Schwann cells

Lipid and protein

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25
Q

What do Schwann cells do to myelinate a neurone?

A

Wrap around them so the myelin sheath consists of several layers of membrane and thin cytoplasm from the Schwann cells

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26
Q

What does the myelin sheath prevent?

A

Movement of ions across the membrane

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27
Q

Where does the movement of ions still occur in a myelinated neurone?

A

The Nodes of Ranvier

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28
Q

What is called when the action potential jumps from one node of ranvier to another?

A

Saltatory Conduction

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29
Q

How is impulse conduction different in unmyelinated neurones?

A

Impulse has to pass through all the membrane instead of jumping from one Node of Ranvier to another

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30
Q

How is the arrangement of Schwann cells and neurones different in an unmyelinated neurone?

A

Un - Axons in 1 Schwann cell that isn’t wrapped around

Myelinated - 1 Axon surrounded in a Schwann cell that is wrapped around

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31
Q

What happens to the speed of transmission in myelinated neurones?

A

Increased. means the action potential reaches the end neurone much quicker so there’s a more rapid response to a stimulus.

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32
Q

What happens to the distance travelled by the impulse in myelinated neurones?

A

Carry impulse much further, from sensory receptors to CNS to effectors

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33
Q

What are non-myelinated neurones normally used for?

A

Carry action potentials over short distances. Normally coordinating body functions like breathing and actions of the digestive system.

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34
Q

When is a neurone at resting potential?

A

When there is no impulse

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35
Q

What does a neurone being polarised mean?

A

Inside the neurone is negative with regards to the outside (about -70 mV)

36
Q

What does the sodium potassium pump do at resting potential?

A

ATPase uses ATP energy to actively transport 3Na+ ions out of the neurone and 2K+ into the neurone

37
Q

Why is the membrane more permeable to, K+ or Na+?

A

K+, there are more channel protein molecules for K+ ions than for Na+ ions

38
Q

What does the membrane being more permeable to K+ cause?

A

More K+ diffuses out then Na+ diffuses in (facilitated diffusion)

39
Q

What are the 2 types of channel that allow K+ and Na+ to diffuse through?

A

Always open channels and voltage-gated channels

40
Q

Which directions are potassium ions pumped?

A

Into axon

41
Q

Which directions are sodium ions pumped?

A

Out of axon

42
Q

What else contributes to the negative charge?

A

Negative ions and negative proteins

43
Q

What is the resting potential of the axon?

A

-70mV

44
Q

What are the stages of an action potential?

A

Resting potential
Depolarised
Hyperpolarised
Repolarised

45
Q

How does an axon become depolarised?

A

Voltage gated Na+ channels open.

Na+ ions diffuse into the axon by facilitated diffusion until they reach +40mV

46
Q

How does an axon become hyperpolarised?

A

Voltage-gated Na+ channels close, voltage-gated K+ channels open.
K+ ions diffuse out of the axon by facilitated diffusion so axon becomes more negative than at resting potential (hyperpolarised)

47
Q

How does an axon become repolarised?

A

K+ and Na+ pump returns change to resting potential

48
Q

Is an impulse passing along the axon during an action potential?

A

Yes

49
Q

What initiates an action potential?

A

Stimuli

50
Q

How is the impulse transmitted along an axon?

A

Local reversal of charge

51
Q

What is the refractory period?

A

Follows an action potential, Na+ voltage-gated channels are closed so another impulse cannot be generated/conducted.
Resting potential needs to be restored by K+ and Na+ ions being redistributed

52
Q

Why is a refractory period important?

A

Ensures impulses are separate

Ensures impulses pass in one direction only.

53
Q

When is a threshold level reached?

A

When a certain number of sodium ions have moved into the axon

54
Q

What happens when a threshold level is reached?

A

Voltage-gated sodium channels open.

More sodium ions move into the axon

55
Q

What is the sodium ions entering the axon and causing voltage-gated sodium channels to open an example of?

A

Positive feedback

56
Q

What is the all or none principle?

A

A stimulus has to be at/above a threshold level for an action potential to be made.
Past the threshold level, an action potential is always the same size.

57
Q

What factors speed up action potential conduction?

A

Myelination
Large axon diameter
Higher temperature

58
Q

How does myelination speed up action potential conduction?

A

Insulation of axon allows for faster conduction.

Longer local circuits

59
Q

How does a large axon diameter speed up action potential conduction?

A

Less resistance to the flow of ions when larger diameter.

Less resistance means depolarisation reaches other parts of the neurone cell membrane quicker

60
Q

How does a higher temperature speed up action potential conduction?

A

Ions diffuse faster at higher temperature but, like proteins, channels will denature above 40 degrees.

61
Q

What is the definition of synaptic cleft?

A

Gap separating the axon of one neurone from the dendrite of another. 20-30nm across.

62
Q

What is the definition of Presynaptic neurone?

A

Neurone along which the impulse has arrived

63
Q

What is the definition of postsynaptic neurone?

A

Neurone that receives the neurotransmitter

64
Q

What is the definition of synaptic knob?

A

The swollen end of the presynaptic neurone. It contains many mitochondria and large amounts of ER to enable it to manufacture the neurotransmitter.

65
Q

What is the definition of synaptic vesicles?

A

Vesicles containing neurotransmitters. They fuse with the presynaptic membrane and release their contents into the synaptic cleft.

66
Q

What is the definition of neurotransmitter receptors?

A

Receptor molecules that the neurotransmitter binds to in the post synaptic membrane

67
Q

What are the 2 types of neurotransmitter?

A

Excitatory

Inhibitory

68
Q

What are excitatory neurotransmitters?

A

Neurotransmitters that result in the depolarisation of the postsynaptic neurone. If the threshold is reached in the post-synaptic membrane, an action potential is triggered. Eg Acetylcholine.

69
Q

What are inhibitory neurotransmitters?

A

Neurotransmitters that result in the hyperpolarisation of the post synaptic membrane. Prevents an action potential being triggered. Eg Gamma-aminobutyric acid (GABA) - found in some synapses in the brain.

70
Q

What is summation?

A

Each stimulus causes the release of a certain amount of neurotransmitter. A single impulse may not release enough neurotransmitter to trigger an action potential so more than one impulse is needed.

71
Q

What are the 2 types of summation?

A

Spatial

Temporal

72
Q

What is spatial summation?

A

A number of presynaptic neurones connect to one postsynaptic neurone. Each releases neurotransmitter which builds up to trigger an action potential

73
Q

What is temporal summation?

A

When a single presynaptic neurone releases neurotransmitter as a result of an action potential several times over a short period. This builds up in the synapse until the quantity is enough to trigger an action potential

74
Q

What are the roles of a synapse?

A

Ensure impulses are unidirectional
A single stimulus creating a number of simultaneous responses.
Stimuli from different receptors interacting to produce a single result.

75
Q

How does a synapse create a single stimulus creating a number of simultaneous responses.

A

An impulse from one neurone to be transmitted to a number of neurones at multiple synapses.

76
Q

How does a synapse have a stimuli from different receptors interacting to produce a single result.

A

Number of neurones may feed into 1 synapse with a single postsynaptic neurone

77
Q

How does a synapse ensure that an impulse is unidirectional?

A

Neurotransmitter receptors are only on the postsynaptic membrane.

78
Q

What are the 2 effects drugs can have on synapses?

A

Stimulation

Inhibition

79
Q

How can drugs cause stimulation?

A

Mimicking the shape of a neurotransmitter
Stimulating the release of more neurotransmitters
Inhibiting enzymes responsible for breaking down neurotransmitters

80
Q

How does mimicking the shape of a neurotransmitter cause stimulation of a synapse?

A

Bind to neurotransmitter receptor on postsynaptic membrane and trigger action potentials.

81
Q

What is an example of a drug that stimulates the release of neurotransmitters?

A

Amphetamines

82
Q

How does inhibiting enzymes that break down neurotransmitters cause stimulation in a synapse?

A

Prevents neurotransmitters being broken down so they stay in the synapse longer

83
Q

What are the 2 ways to inhibit nervous stimulation?

A

Blocking receptors

Binding to specific receptors

84
Q

How does blocking receptors inhibit nervous stimulation?

A

Neurotransmitters can no longer bind and activate the receptor

85
Q

How does binding to specific receptors inhibit nervous stimulation?

A

Changes shape of receptor so active site isn’t complementary to neurotransmitter

Biology module 5 (7 decks)

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