Control of heart rate

Question 1

What doe the autonomic nervous system control?

Answer 1

Controls involuntary activities of internal muscles and glands

Question 2

What can the autonomic nervous system be divided into?

Answer 2

Sympathetic nervous system
Parasympathetic nervous system

Question 3

What does the sympathetic nervous system do?

Answer 3

Stimulates effectors and speeds up activity

Question 4

What does the parasympathetic nervous system do?

Answer 4

Inhibits effectors and slows down activity

Question 5

Why is the sympathetic nervous system used?

Answer 5

Helps to cope in stressful situations by heightening awareness and preparing for activity

Question 6

Why is the parasympathetic nervous system used?

Answer 6

Conserves energy and helps replenish bodys reserves

Question 7

What can the opposite actions of the sympathetic and parasympathetic nervous system be described as?

Answer 7

Antagonistic

Question 8

What does myogenic mean?

Answer 8

Contractions are initiated from within the muscle itself

Question 9

What does neurogenic mean?

Answer 9

Muscle contraction is stimulated from external nervous impulses

Question 10

Where does the myogenic impulse of the heart originate?

Answer 10

SAN
Sinoatrial node

Question 11

Where is the SAN located?

Answer 11

Right atrium

Question 12

Conduction of the heart (Process)

Answer 12

Wave of electrical excitation spreads from SAN to both atria, causing them to contract.
Layer of non conductive tissue prevents wave reaching ventricles
Wave of excitation enters AVN (atrioventricular node) between atria
After a short delay, excitation spreads down atrioventricular septum of heart via bundle of His
Bundle of His branches into smaller fibres of Purkyne tissue at base of ventricles
Excitation released from Purkyne tissue, causing ventricles to contract simultaneously

Question 13

What is resting HR of a typical adult human?

Answer 13

70bpm

Question 14

Where are the changes to heart rate controlled in the body?

Answer 14

Medulla Oblongata (found in the brain)

Question 15

What are the 2 centres in the medulla oblongata concerned with HR?

Answer 15

Centre that increases HR via sympathetic nervous system
Centre that decreases HR via parasympathetic nervous system

Question 16

What are the centres in the medulla oblongata stimulated by?

Answer 16

Receptors detecting chemical or pressure changes in the blood.

Question 17

What do chemoreceptors detect?

Answer 17

Changes in pH

Question 18

Where are chemoreceptors found?

Answer 18

Wall of carotid arteries and aorta

Question 19

How do chemoreceptors control pH (process)?

Answer 19

When blood has high CO2 conc, pH is lowered
Chemoreceptors in wall of carotid arteriesand aorta detect this
Chemoreceptors increase frequency of nervous impulses to centre in medulla that increases HR
This centre increases impulse frequency via sympathetic nervous system to SAN
SAN increase production rate of electrical waves and increase HR
This increases blood flow so more CO2 is removed to lings
pH og blood rises to normal and so chemoreceptors reduce frequency of nerve impulses
Medulla oblongata reduce frequency of impulses down sympathetic nervous system to SAN
HR reduces

Question 20

What do baroreceptors detect?

Answer 20

Changes in blood pressure

Question 21

Where are pressure receptors found?

Answer 21

Walls of Carotid arteries and aorta

Question 22

What do pressure receptors do when bp rises high than normal?

Answer 22

Increase nerve impulses to centre in medulla that decreases HR
This centre send impulses via parasympathetic nervous system to SAN
This decreases HR

Question 23

What do pressure receptors do when bp drops lower than normal?

Answer 23

Transmit more nervous impulses to centre in medulla that increases HR.
This centre sends impulses via sympathetic nervous system to SAN
This increases HR