3.6.1.3 Autonomic control of heart rate Flashcards

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1
Q

What functions does the autonomic nervous system control?

A

heart rate, blood pressure, pupil dilation, digestion

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2
Q

Parasympathetic nervous system

A
  • inhibitory effect on body tissues

- neurones release neurotransmitter acetylcholine

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3
Q

Sympathetic nervous system

A
  • excitatory effect on body
  • neurones release neurotransmitter noradrenaline
  • action of noradrenaline means muscles have increased blood supply more more O2 and glucose
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4
Q

Increase in impulses in parasympathetic system

A
  • more acetylcholine

- slower heart rate

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5
Q

Increase in impulses in sympathetic system

A
  • more noradrenaline

- faster heart rate

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6
Q

What are chemoreceptors and where are they found?

A
  • chemical receptors
  • in aorta, carotid arteries and medulla
  • detect changes in [CO2] & [O2] in blood plasma, and blood pH
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7
Q

What are baroreceptors and where are they found?

A
  • pressure receptors
  • in aorta and carotid arteries
  • detect changes in blood pressure
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8
Q

What increases blood pressure?

A
  • increased heart rate

- increase in blood volume (lower water potential in blood e.g. more salt)

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9
Q

What decreases blood pressure?

A
  • decreased heart rate

- decreased blood volume

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10
Q

Explain how an increase in carbon dioxide changes heart rate

A
  • Increased respiration
  • Increases CO2 in blood produces more carbonic acid to lower pH
  • chemoreceptors in carotid arteries detect the change and send impulses along the sensory neurones to the medulla
  • increase in impulse frequency sent via the sympathetic neurones to the SAN using noradrenaline
  • increased impulses from SAN
  • more contractions of cardiac muscle - heart rate increases
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11
Q

Explain how a decrease in blood CO2 is detected and responded to

A
  • decreased rate of respiration results in less CO2 produces
  • less carbonic acid produced in blood - less acidic pH
  • chemoreceptors in carotid arteries detect this change and send impulses along the sensory neurones to the medulla
  • increase in impulse frequency sent via the parasympathetic neurones to the SAN using acetylcholine
  • SAN sends less impulses / inhibitory effect, so cardiac muscle contracts less - reducing heart rate
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12
Q

Explain how an increase in blood pressure is detected and responded to

A
  • baroreceptors in aorta and carotid arteries detect increase in blood pressure
  • send impulses to medulla
  • increased impulses to the SAN via parasympathetic neurones
  • release of acetylcholine decreases impulses from SAN
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