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Nervous Control Flashcards

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1
Q

Why does timing matter in heart pumping

A

Is atria and ventricles contracted at the same time , bloood wouldn’t flow properly and the heart would be less effective

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2
Q

What does myogenic mean

A

Muscle that can contract without external nerve stimulation, generating its own electrical impulses

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3
Q

Whats the SAN

A

The hearts natural pacemaker located in the right atrium, that initiates each heartbeat

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4
Q

Whats the atrioventricular node

A

Specialised tissue that delays the electrical signal between atria and ventricles

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5
Q

Whats the bundle of his

A

Fast conducting pathway that carries electrical signals from the AVN down the septum

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6
Q

Whats the purkyne tissue

A

Network of fibres that distribute electrical signals throughout the ventricles

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7
Q

Whats depolarisation

A

The electrical change in muscle cells that triggers contraction

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8
Q

3 ways heart rate can be adjusted

A

Sympathetic nerves , parasympathetic nerves and adrenaline

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9
Q

What happens if the bundle of his fails

A

Slow uncoordinated ventricular contractions

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10
Q

What happens is purkyne tissue fails

A

Risk of dangerous irregular rhythms

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11
Q

Whats the main function of the AVN and what happens if it fails

A

Delays signal between atria and ventricles
Heart block - atria and ventricles beat independently

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12
Q

How can a transplanted heart continue to beat

A

It’s myogenic meaning the heart initiates its own contractions without an external electrical impulse

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13
Q

Describe how the SAN acts as a pacemaker to initiate a heartbeat

A

The SAN is located in the wall of the right atrium and) spontaneously initiates/generates a wave of electrical activity/depolarisation;
This electrical activity triggers the heartbeat/contraction of cardiac muscle;

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14
Q

Describe hoe the san initiates a heart beat

A

Acts as a pacemaker maker on teh wall of the right atrium
Cells in SAN depolarise releasing a wave of electrical activity

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15
Q

Scientists investigated a toxin that prevented the heart from depolarising what would then happen to the initiation of a heart beat in this scenario

A

The heartbeat would not be initiated / Heart would stop beating;
Because the sinoatrial node (SAN) is the pacemaker / is responsible for initiating the heartbeat;
The toxin prevents the SAN cells from depolarising, so no wave of electrical activity is generated;

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16
Q

Explain the importance of an AVN delay in a healthy human heart and why this role is critical for partially maintaining stroke volume in a person with atrial fibrillation

A

AVN delay allows the ventricles to fill with the maximum volume of blood.

delay allows time for the atria to fully contract and empty.

Also, for atrial fibrillation, active filling from the atria is lost or reduced.

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17
Q

What is the peripheral nervous system

A

Pairs of nerves that originate from the brain/spinal cord to the rest of the body
Dicvided into secondary and motor nervous system

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18
Q

How is an action potential initiated

A

The Sino atrial node - pacemaker

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19
Q

What does the action potential cause

A

An impulse to travel through the walls of the atria to the AV NODE

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20
Q

How does a heart muscle contract

A

From the apex upwards

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21
Q

Where are the 2 types of nervous receptor found

A

In the walls of teh carotid artery and aorta

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22
Q

What does the medulla oblongata control

A

The rate of the firing action potentials in the SAN

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23
Q

What system increases and decreases heart rate

A

Increase - sympathetic
Decrease - parasympathetic

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24
Q

What happens when blood pressure too high - 4

A

Impulses from the receptor sent to the MO to reduce the HR
Medulla uses the parasympathetic nerve to send impulses to the SA node
SA node decreases the rate of impulses to the AVN to slow heart rate
Prevents high blood pressure

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25
What happens when blood pressure is too low - 4
Impulses from the receptor sent to the medulla oblongata to increase the heart rate Medulla sends a signal down the sympathetic nerve to the SA node SA node increases the rate of impulses to the AVN and heart rate would increase prevents fainting
26
What do chemoreceptors detect
The levels of oxygen in the blood and the changes in blood pH resulting from c02 dissolving in blood plasma forming carbonic acid
27
Why would the blood have low o2 / high co2 / low ph
Exercise- oxygen is being used updater and more co2 produced by cells due to increases rate of respiration
28
What do receptors do if blood oxygen levels or pH is too low?
They increase the frequency impulses to the medulla oblongata causing an increase in the frequency of impulses sent to the SA node via the sympathetic nerve which increases the heart rate. Increase in the heart rate increase in blood flow to the lungs to help increase a two concentration or remove the excess carbon dioxide.
29
What is an action potential
Temporary reversal of the charges across the axon membrane which increases from -65mv to +40mv depolarising the membrane
30
What is an axon
A single long fibre that carries nerve impulses away from the cell body
31
What is hyper polarisation
When the inside of the axon is more negative than usual
32
What is the refractory period
Time period after an action potential when it is impossible for a further action potential to e generated
33
What is repolarisation
When the resting potential of -65mv is reestablished the axon is described as this
34
What is myelin made of
Shwaan cells
35
What do shwaan cells do
Wrap themselves around the axon and act as an electrical insulator
36
What are the patches of bare neurone membrane called
Nodes of ranvier
37
What is concentrated in the nodes of ranvier
The sodium ion channels
38
In teh action potential what does teh stimulus first cause
Neurone cell membrane to become excited Na + channe;s open So membrane is more permeable so sodium ions diffuse down their electrochemical gradient Membrane becomes less negative
39
What does depolarisation cause in an action potential
When the threshold is reached when the generator potential is large enough the voltage gated na+ io channels open More na+ions flood into the cel making it even more positive than outside the cell
40
41
What occcurs during repolarisation
When the potential difference of the membrane reaches +30mv the Na+ ion channels close and the k+ channels open Membrane is more permeable for potassium so they diffuse out of the cell down their gradient Brings the membrane back to resting potential
42
What is a synapse
Junction between 2 neurones or a neurone and an effector cell
43
Define neurotransmitter
A chemical which is secreted by a neurone within the nervous system to stimulate a target cell
44
What is the cell after the synapse known as
Postsynaptic neurone or cell
45
Where is the neurotransmitter released from
The presynamptic membrane and diffuses across synaptic cleft
46
Where are the neurotransmitter receptors
Postsynaptic membrane
47
What is the gap between teh post and presynaptic membranes
Synaptic cleft
48
Whats the first step of the synapse process
Action potential arrives at the end of the presynaptic neurone
49
What happens when the action potential reaches the neurone
Depolarises the membrane and voltage gated calcium ion channels to open and calcium ions to enter the synaptic knob
50
What happens after calcium ions enter
Causes the vesicles containing AcH to fuse to the presynaptic membrane releasing ACh into the cleft through exocytosis
51
What happens when ACh vesicles get to pre synaptic membrane
ACh diffuses across the cleft and binds to specific receptors on the Postsynaptic membrane
52
What happens after the ACh diffuses across
The neurotransmitter binds to NA+ ion channels which open and an influx of sodium depolarises the Postsynaptic membrane
53
Whats summation
Where the effect of a stimulus is added together When there are more action potentials added together
54
What is it called when an action potential jumps from one node of ranvier to the next
Saltatory conduction
55
What transport protein is involves in the resting potential of a neurone
Sodium potassium pump
56
What transport protein is involved in establishing an action potential
Voltage-gates sodium channel
57
What transport protein is involved in establishing hyperpolarisation in a neurone
Voltage gates potassium channels
58
First step of an axon reestablishing an action potential
The voltage gated sodium channels close
59
2nd step
The voltage gated potassium channels open Causing the overall charge inside the axon to become less positive
60
61
What happens when voltage gated potassium channels remain open
Causes the overall change inside the axon to become even less positive =hyperpolarisation
62
How is the electrochemical gradient of sodium and potassium ions restored
The sodium potassium pump Causes the charge inside the axon to be less ositive than the outside =neurones resting potential
63
Define action potential
The state of a neurone in which the inside of its axon reaches its maximum positive charge
64
Explain how a neurone reestablished resting potential after as action potential
Voltage gated sodium channels close - less diffuse into axon VG potassium channels open, allowing some potassium ions to diffuse out of the axon so charge in axon is less positive VG potassium ion channels remain open, allowing more K+ to diffuse out of axon = less positive inside axon = hyperpolarisation Na+ ions diffuse into axon through regular sodium channels and down their electrochemical gradient SP Pump testers electrochemical gradient - AT 3 Na+ ions out of the axon, at the same time as transporting K+ into axon So inside of axon is less positive than the outside so resting potential has been restored
65
Explain how the axon membrane becomes depolarised
A nerve impulse arrives at the axon The membrane PD changes from negative to positive There is an influx of sodium ions into the axon Voltage gates sodium channels open
66
Explain how the axon membrane becomes repolarised
There is an efflux of potassium ions out of the axon Voltage gates sodium channels close The membrane PD changes from positive to negative Voltage gated potassium channels open
67
What’s the typical PD value when a neurone is at resting potential
-65mV
68
What is the state of the neurone when its at hyperpolarisation
Massive efflux of potassium ions out of the axon Many voltage gated potassium channels open The axon PD is at its maximum negative value
69
What are the 2 main purposes of the refractory period
Ensured unidirectionality of action potentials And ensures discrete impulses
70
During an action potential the membrane potential rises and then falls explain the fall
Na+ channels close K+ open Potassium diffuses out
71
After exercise, some ATP is used to re establish the resting potential in axons explain the resting potential is re established
NA+ actively transported out using sodium potassium pump
72
Sodium and potassium ions can only cross the axon membrane through proteins , why
Can’t pas through phosphilipd belayer because water soluble
73
Describe how a pacinian corpuscle produces a generated potential when stimulated
Deforms stretch mediated sodium channels Sodium ions diffuse I’m and depolarises the membrane
74
Explain how the resting potential of -70mv is maintained in the sensory neurone when no pressure is applied
Membrane more permeable to k+ ions and less to na+ Sodium potassium pump pumps 3 na+ out for 2 k+ = more negative in membrane
75
Explain why vision using the fovea has high visual activity
Each receptors connected to separate neurone
76
Explain why visual using other parts of the retina have high sensitivity to light
Rod cells are very sensitive to light as they produce generator potentials at low light intensities because many generator potentials combine to reach threshold Rods combine in groups
77
Explain how a rise blood pressure results in a decrease in the rate of heart rate
Electrical impulses from pressure receptors sent to medulla oblongata to reduce heart rate Parasympathetic nerve to send more impulses to SA node Decreases impulses from SAN SA node decreases the heart rate of impulses to AVN to slow the heart rate
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