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Flashcards in Control Of Heart Rate Deck (12):
1

What does the autonomic nervous system control

The involuntary activities of the internal muscles and glands

2

What does the autonomic nervous system divide into

Sympathetic Nervous system

Parasympathetic nervous system

3

What does the sympathetic nervous system do

Stimulates effectors and so speed up any activity.

It controls effectors when we exercise strenuously or experience powerful emotions

It helps us cope with stressful situations by heightening our awareness and preparing us for activity

4

What does the parasympathetic nervous system do

Inhibits effectors and slows down any activity

It controls activities under normal resting conditions

It is concerned with conserving energy and replenishing the body’s reserves

5

What does it mean when you say that the sympathetic and parasympathetic nervous systems are antagonistic

If one system contracts a muscle, then the other relaxes it

6

Describe the sequence of events that controls the heart rate

Process starts in wall of RA

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

A layer of non conductive collagen tissue prevents the wave crossing to the ventricles

These waves of electrical activity are passed from the SA node to the AV node

After a short delay, the AV node conveys a wave of electrical excitation onto the bundle of his

The bundle of his conducts the wave through the atrioventricular septum to the base of the ventricles, where the bundles branches into smaller fibres of purkyne tissue

The wave of excitation released from the purkyne tissue, causing the ventricles to contract quickly at the same time, from the bottom of the heart upwards

7

What two centres does the medulla oblongata have that are concerned with heart rate

A centre that increases heart rate - which is linked to the SAnode by the sympathetic nervous system

A centre that decreases heart rate, which is linked to the SAnode by the parasympathetic nervous system

8

Where are chemoreceptors found

In the wall of the carotid arteries

9

What makes them sensitive to pH in the blood

Results from changes in co2 concentration, in solution co2 forms an acid and therefore lowers pH

10

Describe the process of control by chemoreceptors

Increase muscular activity

More co2 produced by tissues from increased respiration

Blood pH is lowered

Chemoreceptors in the carotid arteries increase frequency of impulses in the medulla oblongata

Centre in the medulla oblongata that speeds heart rate, increase frequency of impulses to the SA node via the sympathetic nervous system

SA node increase heart rate

Increase blood flow removes carbon dioxide faster

Carbon dioxide concentration returns to normal, and carotid arteries and aorta reduce frequency of nerve impulses to the medulla oblongata

Medulla oblongata reduces frequency of impulses to the SA node, which therefore leads to a reduction in the heart rate

11

What do pressure receptors do when blood pressure is higher then normal

They transmit more nervous impulses to the centre in the medulla oblongata they decreases heart rate.

This centre sends impulses via the parasympathetic nervous system to the SA node or the heart rate, which leads to a decrease in the rate at which the heart beats

12

What do pressure receptors do when blood pressure is lower then normal

They transmit more nervous impulses to the centre in the medulla oblongata that increases heart rate.

This centre sends impulses via the sympathetic nervous system to the SA node, which increases the rate at which the heart beats