14.5: Control of heart rate

Question 1

The autonomic nervous system

Answer 1

Controls the involuntary activities of internal muscles and glands

Question 2

Two divisions of the autonomic nervous system

Answer 2

the sympathetic nervous system

the parasympathetic nervous system

Question 3

The sympathetic nervous system

Answer 3

Acts like an emergency controller which controls effectors and speeds up any activity.

Question 4

Example of effectors the sympathetic nervous system controls

Answer 4

effectors when we exercise or experience powerful emotions

Question 5

The parasympathetic nervous system

Answer 5

This inhibits effectors and so slows down any activity, controls activities under normal resting conditions.

Question 6

Example of the parasympathetic nervous system functions

Answer 6

conserving energy and replenishing the body’s reserves

Question 7

Relationship between the sympathetic nervous system

and the parasympathetic nervous system

Answer 7

antagonistic (oppose each other)

Question 8

Muscle of the heart

Answer 8

cardiac muscle

Question 9

Myogenic

Answer 9

Contraction without external input

Question 10

Is the cardiac muscle myogenic or neurogenic

Answer 10

myogenic

Question 11

Sinoatrial node (SAN)

Answer 11

A group of cells within the wall of the right atrium of the heart, where the initial stimulus for contraction originates

Question 12

SAN aka

Answer 12

pacemaker

Question 13

SAN has a …

Answer 13

… basic rhythm of circulation it determines for the beat of the heart

Question 14

In the basic control of heart rate,

what causes both atria to contract?

Answer 14

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

Question 15

In the basic control of heart rate,

what prevents the wave of electrical excitation from crossing to the ventricles?

Answer 15

The atriventricular septum is a layer of non-conductive tissue which prevents the wave from crossing to the ventricles

Question 16

In the basic control of heart rate,

after causing the atria to contract, where does the wave of electrical excitation go?

Answer 16

the wave of excitation enters a second group of cells called the atrioventricular node (AVN), which lies between the atria.

Question 17

In the basic control of heart rate,

where does the AVN send a wave of electrical excitation?

Answer 17

the AVN conveys a wave of electrical excitation between the ventricles along a series of specialised muscle fibres called purkyne tissue which collectively make up the bundle of His

Question 18

In the basic control of heart rate,

what does the bundle of His do once its received the wave of electrical excitation?

Answer 18

the bundle of His conducts the wave through the atrioventricular septum where the bundle of His branches into smaller fibres of the purkyne tissue, then a wave of excitation is released, causing the ventricles to contract from the bottom of the heart upwards.

Question 19

Whats makes up the bundle of His

Answer 19

the purkyne tissue

Question 20

What controls changes to the resting heart rate?

Answer 20

the medulla oblongata

Question 21

Two centres in the medulla oblongata

Answer 21

• a centre that increases heart rate which is linked to the SAN by the sympathetic nervous system
• a centre that decreases heart rate which is linked to the SAN by the parasympathetic nervous system

Question 22

Where are chemoreceptors found?

Answer 22

In the wall of the cartoid arteries

Question 23

Cartoid arteries

Answer 23

arteries that serve the brain

Question 24

What are chemoreceptors sensitive to?

Answer 24

sensitive to changes in pH of the blood which result from changes in CO2 conc.

Question 25

Where are pressure receptors found

Answer 25

In the walls of the carotid arteries and the aorta

Question 26

When blood pressure is higher than normal the pressure receptors…

Answer 26

Transmit more nervous impulses to the centre in the medulla oblongata that decreases heart rate.

Question 27

When blood pressure is lower than normal the pressure receptors…

Answer 27

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