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Biology Component 3 > The Nervous System > Flashcards

The Nervous System Flashcards

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1
Q

What does the nervous system do?

A

It detects changes inside the body or in their local environment, and arrange process and store information.
It detects a stimulus and initiate response.
In mammals responses too many external and internal stimuli involve the reception of information and its transfer from the receptor to the effector.

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2
Q

What is a stimulus?

A

It is a detectable change in the internal or external environment of an organism that produces a response in the organism.

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3
Q

What are nervous impulses?

A

They are electrical impulses which travel along the neurone and initiate a response in an affective which may be a muscle or gland.

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4
Q

What is the nervous system made up of?

A

The central nervous system and the peripheral nervous system

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5
Q

What is the central nervous system?

A

It is comprise of the brain and spinal-cord which are both surrounded and protected by half protective layer called meninges. The CNS processes information provided by stimulus.

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6
Q

The PNS comprises of two areas what are they?

A

The somatic nervous system and the autonomic nervous system

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7
Q

What is the somatic nervous system?

A

These are pairs of nerves which originate in the brain or spinal cord. These nerves contain fibres of sensory neurones which carry impulses from the receptors to the CNS and motor neurones which carry impulses away from the CNS to the effectors.

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8
Q

What is the autonomic nervous system?

A

It provides unconscious control of the functions of internal organs e.g. heartbeat, digestion.

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9
Q

What does a sensory neurone do?

A

It carries a nerve impulse from the receptor cells to the coordinator.

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10
Q

Describe the journey of the sensory neurone?

A

The nerve impulse begins for the receptors where the receptors send the impulse down the dendrite towards the cell body. The impulse continues and travels away from the cell body to the axon. Impulse reaches the axon terminal which carries it onto the relay neurone in the CNS.

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11
Q

What is the relay neurone?

A

Please lie in the central nervous system, they receive impulses from the sensory neurones and send impulses to the motor neurones.

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12
Q

Describe the journey of the relay neurone?

A

The impulse starts at the dendrites which travels to the cell body, the impulse continues away from the cell body along the axon and ends at the axon terminal/synaptic endings. Relay neurones don’t tend to be myelinated as they’re so small and doesn’t affect the speed of transmission.

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13
Q

What does a motor neurone do?

A

They carry impulses from the coordinator to the effector. The effector then brings about a response.

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14
Q

If you effector is a muscle what is the response?

A

A contraction

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15
Q

If the effector is a gland what is the response?

A

Secretion of hormones.

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16
Q

What is a dendrite and its role?

A

It’s thin extensions which carry impulses towards the cell body

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17
Q

What is the axon and its role?

A

It’s thin cytoplasmic extensions carry and transmit impulses away from the cell body.

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18
Q

What are Schwann cells and its function?

A

These are cells which surround neurones and insulate them electrically. They are wrapped around the body of the axon several times causing the layers to build up this speeds up the nerve impulse.

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19
Q

What is the myelin sheath and it’s role?

A

Schwann cells grow around the axon to form a multilayered fatty sheath, it acts as an electrical insulator which speeds up transmission

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20
Q

What are the nodes of Ranvier?

A

It is areas along the axon where myelin sheath is missing.

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21
Q

What is the cell body?

A

It is part of the neurone which contains the nucleus, mitochondria, RER and several other organelles.

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22
Q

What is a reflex arc?

A

It is a neutral pathway taken by the nervous in pulse of a reflex action with the spinal-cord being the coordinator.

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23
Q

What is a simple reflex?

A

It is an in voluntary response to a non-conscious stimulus and its rapid automatic response.

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24
Q

How does the impulse travels from the stimulus to the effector?

A

STIMULUS –> RECEPTOR –> SENSORY NEURONE–> RELAY NEURONE –> MOTOR NEURONE–> EFFECTOR

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25
Q

What are the two types of cells in a nerve net?

A

Ganglion cells (which provide connections in several directions) and sensory cells which detect stimuli.

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26
Q

What is an example of a nerve net?

A

A hydra, as it doesn’t contain a CNS but a nerve net instead.

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27
Q

What do you do a nerve cell help with in terms of the Hydra?

A

Sensing light and chemicals and detecting physical touch allowing it to sense its environment and act appropriately

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28
Q

How many types of nerve cells are present in hydras and humans?

A

One type of nerve cell is present in the Hydra and sensory and motor neurones are found in the PNS and many different types of found in the CNS.

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29
Q

What is the length of cell processes in the Hydra and humans?

A

Hydra have short self processes and humans have long cell processes.

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30
Q

Is there Myelin sheath present in the Hydra and in a human?

A

There is no myelin sheath present in the hydro but there is myelin sheath present in a human it does have both myelination and unmyelination.

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31
Q

What is the direction of impulse from the point of insolation in a Hydra and in a human?

A

A hydra can have impulses going in both directions where as a human can only have it going in one way.

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32
Q

What is the conduction speed of the hydra and the human?

A

It is slow in the hydra (5m/s) and it is fast in the human(120m/s)

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33
Q

How many stimuli can be detected by the sensory neurone?

A

In a hydra it is limited and in a human there is various stimuli.

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34
Q

How many effectors are in a hydra and a human?

A

Small number of effectors are found in a hydra and skeletal muscles and glands are found in a human.

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35
Q

What is the resting potential?

A

It is the potential difference across the membrane of the cell (difference between the inside and outside of the axon membrane) when no nervous impulses are conducted.

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36
Q

What is the resting potential

A

-70mV

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37
Q

How is the difference of the membrane described as when at -70?

A

It is polarised.

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38
Q

Why is there more negative ions inside the membrane?

A

Large proteins, organic acid e.g pyruvate, organic phosphates e.g ATP 4- in the cytoplasm and from the uneven distribution of inorganic ions.

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39
Q

What is the concentration of ions like inside the atom membrane?

A

There is a higher concentration of K+ ions with a lower concentration of Na+ ions.

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40
Q

What is the concentration of ions like outside the membrane?

A

There is a higher concentration of Na+ ions and a lower concentration of K+ ions.

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41
Q

What is the movement of the ions?

A

They tend to diffuse out of the membrane down a concentration gradient (against a charge gradient), whilst the Na+ tend to diffuse in. Some K+ channels are open so allow K+ ions to leak out. The axon membrane is 100x more permeable to K than to Na, so they tend to move out faster than Na diffusing in.

42
Q

What does the Na/K pump actively transport?

A

3Na+ ions OUT and 2K+ ions IN

43
Q

What does the pump do?

A

It applies a concentration gradient and an uneven distribution of ions across the membrane in order to maintain the concentration. As Na+ is pumped out faster than K+ brought in the outside becomes more positive than the inside, so the inside is negative.

44
Q

What does the pump require?

A

ATP from ATPase activity

45
Q

What is an action potential?

A

It is the rapid rise and fall of electrical potential across a nerve cell membrane as a nervous impulse passes.

46
Q

What is a nerve impulse?

A

It is the movement of ions in and out of the membrane, it is based on sodium and potassium ions.

47
Q

What 4 types of transport proteins does the axon have?

A

A Na/K pump, Voltage gated Na+ channels, voltage gated K+ channels and open K+ channels.

48
Q

What is the threshold value?

A

-55mV

49
Q

What happens during depolarisation?

A

A stimulus causes the voltage gated Na channels to open ( more permeable to Na+ ions )so Na+ can flood in, down their concentration and charge gradient. An influx in Na causes the inside membrane to become more positive than outside. If enough Na+ ions diffuse in to raise the pd above -55mV then all sodium channels will open and Na+ will flood in. The membrane has now depolarised.

50
Q

During depolarisation what value does the potential difference reach?

A

40 mV

51
Q

What happens when depolarisation has occurred?

A

Once it reaches 40mV the Na channels close in order to prevent further influx of sodium.

52
Q

What happens during repolarisation?

A

Once the Na+ channels close, the K+ channels open, the membrane is more permeable to K which diffuses out of the membrane down their concentration gradient. K+ ions flood out reducing the pd across the membrane.

53
Q

What happens at hyperpolarisation?

A

As many potassium ions are leaving the axon (more K+ diffusing out then Na+ diffusing in) the potential difference becomes briefly more negative than the resting potential this overshoot is called hyperpolarisation. The voltage gated K+ channels close and the pump restarts pumping K+ in and Na+ out. The resting potential is restored and the membrane is now polarised.

54
Q

What is the refractory period?

A

When concentrations are restored to that of the resting potential. During this time the axon cannot transmit another action potential which insures that the transmission flows in only one Direction.

55
Q

How do you sodium ions move when setting up local currents?

A

They move laterally along in the axon. They depolarise the adjacent section of the membrane.

56
Q

What is the absolute refractory period?

A

It is when the Na+ channels are inactivated for a short time to prevent influx .Once the resting potential is re-established the sodium channels can open so a new action potential can be initiated this is the absolute refractory period and last for 1 m/s.

57
Q

What does the refractory period prevent?

A

The action potential from propagating in the direction it travelled in and that an action potential is being generated in the opposite direction.
A second action potential being generated to close the first – it limits the frequency of the action potentials along a neurone.

58
Q

What is the all or nothing theory?

A

The size of the action potential is independent of the size of the stimulus as long as the stimulus exceeds the threshold value and action potential is generated.

59
Q

Does the size or strength of an impulse make any difference?

A

If the strength of the stimulus causes depolarisation the action potential always has the same strength and size and won’t vary. It will remain the same size as it’s propagated along the axon with no energy being lost in transmission. An increase in intensity of the stimulus doesn’t create a greater action potential however the frequency of action potentials increases along the neurone. A stimulus could generate an action potential in more than one neurone

60
Q

What to say all or nothing law state?

A

That are nervous impulses either initiate it or not, it will always have the same size. This allows the action potentials to act as a filter preventing minor stimuli from setting up nervous impulses to the brain is not overloaded with information.

61
Q

What are the three factors which affect the speed of conduction of nerve impulse?

A

Myelination, diameter of axon and temperature.

62
Q

How does myelination affect the speed of conduction?

A

It’s based on the rate of transmission by insulating the axon (stop ions moving in or out of the membrane) sodium ions flow through the axon but a myelinated nerve only depolarises at low resistance. The voltage gated ion channels are only found at the nodes of ravier, the sheath acts as a good electrical insulator between the nodes.

63
Q

What is saltatory propagation?

A

It is when an action potential can jump large distances from node to node. It is rapid and much faster with myelinated neurones travelling at 100 m/s and unmyelinated neurones having a maximum speed of 1 m/s.

64
Q

How does the diameter of the axon affect the speed of conduction?

A

The greater the diameter the lower the resistance. It will then have a greater volume relative to its areas so more ions can flow through the axon so the impulse travels faster.

65
Q

How does temperature affect the speed of conduction?

A

Ions move faster at high temperatures and at lower temperatures as they have more kinetic energy. As the temperature increases to 40°C speed of transmission increases because of the generation of impulses involves active transport which requires ATP from respiration. Anything which speeds up respiration also speeds up the transmission of nerve impulses.

66
Q

What are the neurones separated by?

A

Synapses

67
Q

What is synaptic transmission?

A

It’s when the impulse arrives at the synaptic end bud, which alters the membranes permeability (depolarising the presynaptic membrane) opening voltage gated calcium channels so Ca2+ can diffuse into the end of the bulb down their concentration gradient. An influx in calcium which causes the synaptic vesicles to move towards and fuse to the presynaptic membrane. Which releases the neurotransmitter into the synaptic cleft. It then diffuses across the synaptic cleft and binds to the receptor (which has two subunits where the acetylcholine can bind to showing cooperative binding). Once the acetylcholine have bonded they change the proteins shape causing the ligand gated Na+ channels to open on the post synaptic membrane., where sodium can diffuse down their concentration. This depolarises the post synaptic membrane and an action potential is initiated.

68
Q

What happens is an insufficient amount of ACh is bound?

A

It means that the postsynaptic membrane won’t be depolarise enough to exceed the threshold so an action potential is not produced.

69
Q

What happens if ACh was to remain in the synaptic cleft left?

A

It would continue to bind to the site meaning that the sodium channels would stay permanently open resulting in a permanent depolarisation of the postsynaptic membrane and white repolarise. There will never be another action potential. New impulses would constantly be initiated that the impulses wouldn’t be distinct.

70
Q

How is ACh remaining in the synaptic cleft prevented?

A

Direct uptake of ACh in the presynaptic membrane so none of it remains in the signup tick left which can then find to receptors on the postsynaptic membrane. Active transport of calcium ions out of the synaptic and bulb no exocytosis of ACh can occur.
Hydrolysis of ACh.

71
Q

What is the enzyme called which breaks down acetylcholine found in the synaptic cleft?

A

Acetylcholinesterase

72
Q

What is the products of the breakdown of ACh?

A

Ethanoic acid and choline

73
Q

What happens in the breakdown of ACh?

A

The hydrolysis of products tend to fuse across to synaptic cleft into the presynaptic neurone which reforms acetylcholine this requires ATP when re-forming the neurotransmitter and storing them in the vesicles for the exocytosis. This is why there are several mitochondria found at the axon and bulbs where the ATP is generated

74
Q

Why can impulses only travel in one direction?

A

Repolarisation happens with behind the action potential so depolarisation is unable to occur at that point. Synaptic vesicles are only found at the end of the pre-synaptic neurone.
Neurotransmitter receptors are only found on the postsynaptic membrane.

75
Q

What are the function of synapses?

A

Transmit information between neurones.
Pass impulses in one direction generating precision within the nervous system.
Act as junctions.
Protect the response system from over stimuli because the impulse is always the same size in the matter the size of the stimulus.
Filter out low-level stimuli (all or nothing law)
They allow summation

76
Q

What is temporal summation?

A

It is when the postsynaptic neurone can only be stimulated if there are frequent action potentials in the presynaptic membrane i.e. depolarisation builds up over time in order to reach the threshold value at which an action potential is initiated.

77
Q

What is spatial summation?

A

Is when the postsynaptic neurone may only be stimulated if several presynaptic neurones receive stimulation this all contributes to the growing depolarisation which generates a potential large enough.

78
Q

What is a drug?

A

It is a molecule which has a psychological affect on the body when ingested, inhaled, absorbed or injected. Many drugs act at the synapses and disrupt the normal functioning of the neurotransmitters producing abnormal patterns on the nervous impulses.

79
Q

Name the neurotransmitters?

A

ACh, GABA, monoamines and neuropeptides.

80
Q

What are excitatory drugs (stimulants)?

A

They stimulate the nervous system by creating/ allowing more action potentials in the postsynaptic neurones

81
Q

What are inhibitory drugs (sedatives)?

A

They inhibit the nervous system by reducing the number of action potentials produced.

82
Q

What could happen if a drug was taken continuously?

A

The synapses may start to adapt this can cause a tolerance to drugs e.g. if a drug blocks receptors in the synapses new receptors will be made in order to make up for that ones not in use so more of the drug is needed to be to produce the same effect.

83
Q

What is dependency of a drug?

A

It is when changes have occurred in the CNS meaning individual can’t manage without the drug.

84
Q

What is an agonist?

A

It is a substance which binds to the receptor and activates it like the normal neurotransmitter (it mimics the effect of a neurotransmitter)

85
Q

What is an antagonist?

A

It is a substance which binds to receptor but doesn’t activate it it just prevents the normal neurotransmitter from binding. This would reduce the effect normally produced by the neurotransmitter (this is like competitive inhibitor)

86
Q

What are the different types of drug action?

A

Release of neurotransmitter, binding to the receptors, removal of neurotransmitters and mimicking the action of neurotransmitters.

87
Q

How does Botulinum toxin work?

A

It prevents the release of the neurotransmitter, ACh which controls a voluntary muscles. This causes muscle weakness, paralysis and death (the breathing muscles stop working)

88
Q

How does amphetamine work?

A

It increases the rate release of the neurotransmitter noradrenaline normally associated with stress high blood pressure, increase heart rate, sweating and insomnia.

89
Q

How does curare work?

A

It is a South American arrow poison which blocks acetylcholine receptors on voluntary muscles, leading to flaccid paralysis and death.

90
Q

How do you beta-blockers work?

A

They block receptors for noradrenaline, decreasing heart rate and blood pressure, a treat hypertension.

91
Q

How does anticholinesterases work?

A

It prevents the metabolism of neurotransmitter at voluntary muscles causing spastic paralysis (contracted paralysis) death by suffocation suffocation. Most nerve gases have this affect and some insecticides.

92
Q

How does cocaine work?

A

It slows down the removal of noradrenaline causing high blood pressure, pupil dilation and constipation.

93
Q

How can drugs mimic the action of neurotransmitters?

A

They have the same shape and bind to the postsynaptic neuron in the same way increasing the frequency of action potentials.

94
Q

Name an example of a drug which can mimic the action of neurotransmitters?

A

Nicotine

95
Q

How does nicotine work?

A

It has the same group of atoms including a positively charged nitrogen and nicotine and ascertain Okane allowances to bind to the same receptor. Nicotine increases the frequency of impulses however nicotine is not removed by hydrolysis so continues to initiate impulses. The body could become habituated to nicotine so much needs to be taken in order to get the dark desired effect. If no nicotine is taken in the impulses and not transmitted normally. Reducing and withdrawal of nicotine can be made worse as nicotine increases the release of dopamine in the brain which generates pleasurable sensations.

96
Q

How do organophosphorus insecticides work?

A

They prevent the breakdown of neurotransmitters. These drugs block and then inhibit the enzyme acetylcholinesterase which breaks down acetylcholine into choline and ethanoic acid. As it prevents the breakdown it prolongs the effect of ACh so it’s not hydrolysed so remains in the synaptic left. This causes repeated depolarisation of the postsynaptic neurone with action potentials being repeatedly fired at the postsynaptic neurone

97
Q

What happens if ACh remains at the neuromuscular junction?

A

It will cause repeated muscle contractions resulting in the depletion of ATP, paralysis and death.

98
Q

What are organophosphates?

A

They are esters of phosphoric acid which can be inhaled, absorbed or ingested which include insecticides (malathion, dichlorvos), herbicides (glyphosphate) and nerve gases (sarin).

99
Q

What do nerve gases do?

A

They inhibit acetylcholinesterase at neuromuscular junction, generating repeated uncontrollable contractions of muscles. If it occurs in antagonistic muscle pears it can break bones.

100
Q

What are psychoactive drugs?

A

These drugs primarily act on the central nervous system by affecting different neurotransmitters or their receptors which affects the firing of neurons. This alters the function of the brain causing temporary changes in perception, mood, consciousness and behaviour.

101
Q

What are some therapeutic drugs?

A

Ritalin (a CNS stimulant, inhibit the re-uptake of neurotransmitters, used in ADHD), prozac ( an SSRI, prevents re-uptake of NT’s involved in mods and anxiety) and Paxil.

102
Q

What are some recreational drugs?

A

Nicotine (binds to the acetylcholine receptor and keeps stimulating the receptor once broken down), alcohol ( binds to the GABA receptor (an inhibitory recptor)), cannabis, cocaine, amphetamines, ecstasy and heroin,

Biology Component 3 (9 decks)

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