6.Control Of Heart Rate

Question 1

What is the heart?
What controls the rate which heart muscles contract?

Answer 1

The heart is MYOGENIC
The rate at which heart muscles contracts is controlled by WAVES OF ELECTRICAL ACTIVITY.

Question 2

What does Myogenic mean?

Answer 2

Cardiac Muscle(Heart) can contract and relax without receiving external signals so cardiac muscle creates own action potential.

Question 3

Where is SAN located?
What is SAN?

Answer 3

SAN located in RIGHT ATRIUM.
SAN is Sinoatrial node

Question 4

How is contraction caused?
-First thing that occurs in contraction-
[ALEVEL[

Answer 4

1.SAN releases ‘wave of depolarisation’ across atria so atria contracts.
2.Wave of depolarisation reach Antrioventricualr node [AVN]

Question 5

What is the SAN?

Answer 5

SAN is Sinoatrial Node

Question 6

What is the AVN?

Answer 6

AVN is Atrioventricular Node.

Question 7

What is the first part of the heart involved in contraction?

Answer 7

First part of the heart causes electrical activity is Sinoatrial node [SAN]

Question 8

What happens to the AVN when SAN wave of depolarisation reaches the AVN?
What is between atria and ventricle?

Answer 8

AVN release another wave of depolarisation.
Between atria and ventricle there is a NON-CONDUCTIVE LAYER which prevents wave of depolarisation travelling down to ventricles.

Question 9

Where does the wave of depolarisation of AVN travel to?

Answer 9

Wave of Depolarisation from AVN.
Bundle of His(part of AVN) transmits wave down the SEPTUM to the PURKYNE FIBRES in ventricle walls making Ventricle wall as contract.

Question 10

What cause Ventricle walls to contract?
[ALEVEL CONTROL OF HEART RATE]

Answer 10

Bundle of His transmits wave down the septum to the purkyne Fibers in ventricle walls make ventricle walls contract.

Question 11

What contracts first?
[Alevel control of Heart rate]

Answer 11

The Apex(bottom of the heart) then Ventricle walls contract allowing release of blood into blood vessel(Pulmonary Artery/Aorta)

Question 12

How is Resting potential achieve again in control of heart rate?

Answer 12

After ventricle walls contract
Cardiac Muscle relaxes cell are REPOLARISED
Resting potential achieve again so cardiac muscle relax

Question 13

What controls Heart rate and how does it control heart rate?

Answer 13

Medulla Oblongata in brain controls heart rate by the Autonomic Nervous System.
Autonomic Nervous System carries signals to Medulla oblongata which send signals to SAN to control heart rate.

Question 14

What are the two main centres in medulla Oblongata and what does it do?

Answer 14

Two main centres are Sympathetic and Parasympathetic.
Sympathetic:Increase heart rate via sympathetic nervous system linked to SAN
Parasympathetic:Decrease heart rate via the parasympathetic nervous system.

Question 15

Where do Signals travel to to control heart rate?

Answer 15

AVN TO MEDULLA OBLONGATA TO SAN

Question 16

What happens when there is a change in Heart rate?

Answer 16

When there is a change in heart taste the body is going to do the opposite to prevent blood vessel from bursting

Question 17

What happens when there is an increase in pressure change?

Answer 17

1.Detected by pressure receptors in the wall of the aorta and carotoid artery
2.Impulse sent to medulla Oblongata THEN BACK to SAN BY the Parasympathetic nervous system
3.Decrease in frequency of electrical signals so heart rate decreases.

Question 18

What does Parasympathetic nervous system do?

Answer 18

Parasympathetic nervous system decrease.

Question 19

What happens when there is decrease in pressure?

Answer 19

1.Detected by pressure receptors in the Aorta and Cartoid Artery
2.Impulses sent to Medulla Oblongata and back to SAN BY the Sympathetic nervous system.
3.Increase in Frequency of electrical signals so heart rate increases.

Question 20

What causes a decrease in pH?

Answer 20

A decrease in pH levels result due to exercise as high respiration increase production of C02 and lactic Acid

Question 21

What occurs a when there is a decrease in pH levels?

Answer 21

1.Decrease in pH detected by CHEMORECEPTORS in Aorta and Cartoid Artery
2.Impulses sent to medulla Oblongata and back to SAN by the Sympathetic nervous system.
3.Increased frequency of electrical signals to the heart so heart rate increases so Higher volume of Blood is delivered to lungs to remove CO2

Question 22

When is Sympathetic nervous system used?

Answer 22

Sympathetic nervous system used when a decrease…

Question 23

Where are …receptors found?

Answer 23

Walls of Aorta and Cartoid Artery