Nervous systems Flashcards

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1
Q

What is a nerve impulse

A

Self propagating wave of electrical disturbance travelling along surface of axon membrane

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2
Q

What is resting potential

A

Potential difference across he axon when a neuron is at rest

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3
Q

What are the charges of inside and outside of an axon

A

Inside is negatively charged relative to outside

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4
Q

What is an axon

A

The long fibre in a neurone tat conducts impulses away from the cell body

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5
Q

What is the purpose of the myelin sheath

A

Made of schwaan cells that insulates the axon, shields the axon from surrounding tissue fluid and insulates it from other neurones

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6
Q

What is depolarisation

A

A rapid temporary reversal of the resting membrane potential

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7
Q

What is re polarisation

A

A return to the resting membrane potential

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8
Q

How is resting potential maintained?

A

Membrane more permeable to potassium ions and less to sodium ions
Sodium ions are actively transported out and potassium ions pumped in

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9
Q

How does MS lead to slower responses to stimuli?

A

Myelin sheath broken down
Impulse is unable to jump from node to node
More depolarisation over length of membrane

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10
Q

How does a lower temperature lead to slower nerve impulse conduction?

A

Ions have less kenetic energy and therefore they diffuse more slowly

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11
Q

What factors affect speed of nerve impulse conduction

A

Myelination
Diameter of axon
Temperature

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12
Q

What is the absolute refractory period?

A

After generation of an action potential
Voltage gated sodium channels are inactivated
They cannot respond to further stimulus

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13
Q

What is a synapse?

A

Junction between neurones

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14
Q

Where are neurotransmitters made and where are they stored?

A

Made in pre synaptic neurones

Stored in synaptic vesicles

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15
Q

What is summation?

A

Arrival of multiple action potentials leading to a build up of neurotransmitter

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16
Q

Why does depolarisation happen?

A

Sodium ion gates open

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17
Q

Why can another action potential not be generated once one has just been generated?

A

Membrane more impermeable to sodium ions
Sodium ion cannot enter axon
Membrane becomes more negative than resting potential

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18
Q

Explain why a neurotransmitter (e.g. acetylcholine) can only bind with one type of receptor protein in the postsynaptic membrane.

A
Unique shape of receptor protein / binding site
Due to (tertiary) structure of protein molecule
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19
Q

What is the role of calcium ions (Ca2+) in synaptic transmission?

A

Cause vesicles to move to presynaptic membrane

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20
Q

How is an action potential generated?

A

Sodium ion channels open;

Allowing rapid influx of sodium ions

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21
Q

How does an increase in exercise cause an increase in heart rate?

A

Chemoreceptors detect rise in PH sends impulse to medulla. More impulses to SAN by sympathetic nervous system.

22
Q

DDT binds to sodium channels, and consequently channels remain open, how does this kill?

A

Neurones remain depolarised

No action potentials generated

23
Q

What does the SAN do?

A

Sends waves of excitation through the atria initiating the heart beat

24
Q

What delays the contraction of the ventricles?

A

Non- conductive tissue prevents electrical impulse from reaching ventricles
Electrical impulse forced via AVN

25
Q

Why is it important that there is a delay before the contraction of the ventricles?

A

Allows the atria to fully contract and empty

26
Q

Why does the left ventricle have the highest blood pressure and why is this important?

A

It has the most cardiac muscle so it contracts at a higher force which is important as it pumps blood to the whole body

27
Q

What is the role of the Purkyne tissue and the bundle of his?

A

Conduct the electrical impulse

28
Q

What is the effect of adrenaline on heart muscle?

A

Beats faster

Beats stronger : myoctyes contract with greater force

29
Q

How does adrenaline increase heart rate?

A

It binds to specific receptors on the membranes of cells in the SAN

30
Q

What do baroreceptors detect?

A

Change in pressure

31
Q

Response to high blood pressure in the heart

A

Detected by baroreceptors
Then via parasympathetic
Releases acetylcholine

32
Q

How are the parasympathetic and sympathetic nervous systems antagonistic?

A

If one system contracts a muscle then the other relaxes

33
Q

The sympathetic nervous system does what to an activity?

A

Speeds up activity

34
Q

The parasympathetic nervous system does what to an activity?

A

Inhibits effectors and so slows down any activity

35
Q

Changes to heart rate are controlled by which region of the brain?

A

Medulla oblongata

36
Q

What do rods detect in the eye?

A

Light vs dark

37
Q

What do cones detect in the eye?

A

Wavelength i.e colour

38
Q

Describe a simple reflex arc

A

Stimulus-receptor-sensory neurone-motor neurone- effector- response

39
Q

What are the types of photoreceptors in the eye?

A

Cones and rods

40
Q

Why do rod cells provide low visual acuity?

A

More than one rod cell shares the same synapse with a biopolar cell. As a result multiple rods need to be stimulated to give a generator potential

41
Q

Why do cone cells provide good visual acuity?

A

each cone cell has its own synapse via a bipolar neurone connecting to the optic nerve

42
Q

The speed of an action potential depends on?

A

Presence or absence of a myelin sheath
Diameter of an axon
Temperature

43
Q

What is the refractory period?

A

A period where the neuron cannot become excited as sodium ion channels enter a recovery stage

44
Q

Why is the refractory period important

A

Prevents action potentials travelling in the wrong direction

45
Q

What are some of the roles of synapses?

A

Prevent action potentials travelling in the wrong direction
Amplify the effects of low frequency action potentials
Inhibitory or excitory

46
Q

What happens when an action potential reaches a synapse?

A

Presynaptic membrane depolarises
Ca2+ channels open
Calcium ions diffuse into presynaptic neurone

47
Q

Roles of calcium ions in transmission across a synapse?

A

Causes the fusion of vesicles filled with neurotransmistter with presynaptic membrane

48
Q

Role of neurotransmitter in transmission across a synapse

A

Released into synaptic cleft
Binds to receptors in the post synaptic membrane which stimulates the opening of Na+ channels allowing Na+ ions to enter neurone

49
Q

What happens to acetylchloline after an action potential has been generated?

A

Acetylchloinesterase hydrolyses it and it diffuses back into presynaptic membrane where it can be reused and prevents continous generation of an action potential

50
Q

Why is the response in heart beat less in diabetic rats?

A
Damage to autonomic nervous system 
Pressure receptors dont work as well 
Damage to medulla 
Change in number of impulses to medulla 
Damage to sympathetic system so doesnt speed up enough