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B14- RESPONSE TO STIMULI > 14.5- CONTROL OF HEART RATE > Flashcards

14.5- CONTROL OF HEART RATE Flashcards

1
Q

What does autonomic mean?

A

self-governing

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2
Q

What does the autonomic nervous system control?

A

involuntary (subconscious) activities of internal muscles + glands

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3
Q

What are the two divisions of the autonomic nervous system?

A

sympathetic nervous system

parasympathetic nervous system

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4
Q

What does the sympathetic nervous system in general stimulate?

A

effectors and so speed up any activity

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5
Q

What does the sympathetic nervous system act like?

A

emergency controller

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6
Q

What does the sympathetic nervous system control?

A

when we exercise strenuously or experience powerful emotions

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7
Q

What does the sympathetic nervous system help us cope with?

A

help us cope with stressful situations by heightening our awareness + preparing us for activity (fight or flight response)

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8
Q

What does the parasympathetic nervous system in general do?

A

in general inhibits effectors + so slows down any activity

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9
Q

What does the parasympathetic nervous system control?

A

controls activities under normal resting conditions

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10
Q

What is the parasympathetic nervous system concerned with?

A

conserving energy + replenishing body’s reserves

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11
Q

What are the actions of the sympathetic and parasympathetic nervous system like?

A

normally oppose one another

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12
Q

As the actions of the sympathetic and parasympathetic nervous system normally oppose one another, what are they called?

A

antagonistic

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13
Q

What is the muscles of the heart known as?

A

cardiac muscle

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14
Q

Why are the cardiac muscle myogenic?

A

its contraction initiated from within muscle itself, rather than by nervous impulses from outside (neurogenic)

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15
Q

Where is the sinoatrial node (SAN) located?

A

within wall of right atrium of heart

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16
Q

What originates at the SAN?

A

initial stimulus for contraction originates

17
Q

What does the SAN have that determines the beat of the heart?

A

has a basic rhythm of stimulation

18
Q

As the SAN has a basic rhythm of stimulation that determines the beat of the heart, what is it called?

A

pacemaker

19
Q

Sequence of events that control basic heart rate: what spreads out from the SAN? #1

A

wave of electrical excitation spreads out from sinoatrial node across both atria, causing them to contract

20
Q

Sequence of events that control basic heart rate: what does a layer of non-conductive tissue (atrioventricular septum) do? #2

A

prevents wave crossing to ventricles

21
Q

Sequence of events that control basic heart rate: where does the wave of excitation enter after causing the atria to contract? #3

A

enters second group of cells called atrioventricular node (AVN), which lies between atria

22
Q

Sequence of events that control basic heart rate: what does the AVN do after a short delay? #4

A

conveys wave of electrical excitation between ventricles along series of specialised muscle fibres called Purkyne tissue which collectively make up structure called bundle of His

23
Q

Sequence of events that control basic heart rate: what does the bundle of His do the wave? #5

A

conducts wave through AV septum to base of ventricles, where bundle branches into smaller fibres of Purkyne tissue

24
Q

Sequence of events that control basic heart rate: where is the wave of excitation released from? #6

A

from Purkyne tissue, causing ventricles to contract quickly at same time, from bottom of heart upwards

25
Q

What is the resting heart rate of a typical adult human around?

A

70 beats per minute

26
Q

What region of the brain controls the changes to the heart rate?

A

medulla oblongata

27
Q

What two centres does the medulla oblongata have that’s concerned with heart rate and how are they linked to the SAN?

A

centre that increases heart rate, which is linked to SAN by sympathetic nervous system

centre that decreases heart rate, which is linked to SAN by parasympathetic nervous system

28
Q

Where are chemoreceptors found?

A

in wall of carotid arteries (arteries that serve brain)

29
Q

What are chemoreceptors sensitive to?

A

sensitive to changes in pH of blood that results from changes in CO2 conc.

30
Q

In solution what does CO2 form, and so what does this do?

A

CO2 forms acid and so lowers pH

31
Q

When the blood has a higher than normal conc. of CO2, how is this detected?

A

chemoreceptors in wall of carotid arteries + aorta detect this + increase frequency of nervous impulses to centre in medulla oblongata that increase heart rate

32
Q

What does the centre in the medulla oblongata do? (when blood acidic from higher than normal CO2 conc.)

A

centre increases frequency of impulses via sympathetic nervous system to SAN
in turn increases rate of production of electrical waves by SAN + so increases heart rate

33
Q

What does an increased blood flow lead to? (when blood acidic from higher than normal CO2 conc.)

A

leads to more CO2 being removed by lungs and so CO2 conc. of blood returns to normal

34
Q

When the pH of the blood rises to normal, what happens? (when blood acidic from higher )

A

chemoreceptors in wall of carotid arteries + aorta reduce frequency of nerve impulses to medulla oblongata

35
Q

What does the medulla oblongata do when the blood pH has risen to normal? (when blood acidic from higher than normal CO2 conc.)

A

reduces frequency of impulses to SAN, which leads to reduction in heart rate

36
Q

Where do pressure receptors occur?

A

within walls of carotid arteries and aorta

37
Q

How do pressure receptors operate when blood pressure higher than normal?

A

pressure receptors transmit more nervous impulses to centre in medulla oblongata that decreases heart rate
centre sens impulses via parasympathetic nervous system to SAN of heart which leads to decrease in rate at which heart beats

38
Q

How do pressure receptors operate when blood pressure lower than normal?

A

pressure receptors transmit more nervous impulses to centre in medulla oblongata that increase heart rate
centre sends impulses via sympathetic nervous system to SAN, which increases rate at which heart beats

B14- RESPONSE TO STIMULI (5 decks)

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