Cardiac Conduction System

Question 1

What is the systole?

Answer 1

Contraction phase

Question 2

What is the diastole?

Answer 2

Relaxation phase

Question 3

What does the sinotrial node do?

Answer 3

It is the pace maker
- Creates an impulse
- Creates atrial systole

Question 4

How does the Cardiac Conduction System work?

Answer 4

• Sinotrial Node (SAN) creates an impulse which creates atrial systole
• Impulse reaches Atrioventricular Node (AVN) (0.1-0.2s)
• Impulse sent down bundle of HIS
• Goes to Purkinje Fibres which causes ventricular systole

Question 5

What does the AVN node do?

Answer 5

Atrioventricular Node (AVN) holds the impulse from thee SAN for 0.1s-0.2s then releases the impulse into the bundle of HIS

Question 6

What does the bundle of HIS do?

Answer 6

Spreads out the impulse released from the AVN into the Purkinje Fibres

Question 7

What do the Purkinje Fibres do?

Answer 7

Causes the ventricles to contract (ventricular systole)

Question 8

What is the mnemonic for the Cardiac Conduction System? SAABPV

Answer 8

Sally Always Aims Balls Past Vicky

• SAN
• Atrial Systole
• AVN
• Bundle of HIS
• Purkinje Fibres
• Ventricular Systole

Question 9

What is the Sympathetic System?

Answer 9

A part of the autonomic nervous system that speeds up heart rate

Question 10

What is the Parasympathetic System?

Answer 10

A part of the autonomic nervous system that decreases heart rate

Question 11

What are Chemoreceptors?

Answer 11

Tiny structures in the carotid arteries and aortic arch that detect changes in blood acidity causes by an increase or decrease in the concentration of carbon dioxide.

Increased concentration of carbon dioxide will stimulate the sympathetic nervous system, causing heart to beat faster.

Question 12

What are Baroreceptors?

Answer 12

Special sensors in tissues in the aortic arch, carotid sinus, heart and pulmonary vessels that respond to changes in blood pressure to either increase or decrease heart rate.

Question 13

What are Proprioceptors?

Answer 13

Sensory nerve endings in the muscles, tendons and joints that detect changes in muscle movement.

At start of exercise they detect an increase in muscle movement which sends an impulse through the sympathetic nervous system to the SAN to increase heart rate.

Question 14

What is Myoglobin?

Answer 14

An iron-containing muscle pigment in slow-twitch muscle fibres which has a higher affinity for oxygen than haemoglobin.

It stores the oxygen in muscle fibres which can be used quickly when exercise begins.

Question 15

What is Haemoglobin?

Answer 15

An iron-contains pigment found in red blood cells, which combines with oxygen to form oxyhemoglobin.

Red blood cells carry oxygen to the areas needed in the body.

Question 16

What is systolic pressure?

Answer 16

The pressure in the arteries when the ventricles are contracting.

Question 17

What is blood pressure?

Answer 17

The force entered by the blood against the blood vessel wall

Blood flow x resistance

Question 18

What is diastolic pressure?

Answer 18

The pressure in the arteries when the ventricles are relaxing

Question 19

Chemoreceptors simplified

Answer 19

• Chemoreceptors
• Increase in CO2
• Increase in heart rate

Question 20

Baroreceptors simplified

Answer 20

• Baroreceptors
• Increase in blood pressure
• Decrease in heart rate

Question 21

Proprioceptors simplified

Answer 21

• Proprioceptors
• Increase in muscle movement
• Increase in heart rate

Question 22

What is Adrenaline?

Answer 22

A stress hormone that is released by the sympathetic nerves and cardiac nerve during exercise which causes an increase in heart rate.

Question 23

What is Stroke Volume?

Answer 23

The volume of blood pumped out by the heart ventricles in each contraction

Question 24

What is the diastole phase?

Answer 24

When the heart relaxes to fill with blood

Question 25

What is the ejection fraction?

Answer 25

The percentage of blood pumped out by the left ventricle per beat

Question 26

Starlings Law simplified

Answer 26

• Increased venous return • Greater diastolic filling of the heart • Cardiac muscle stretched • More force of contraction • Increased ejection fraction

Question 27

Starlings Law

Answer 27

The greater the venous return the greater the subsequent force of contraction

Question 28

What is the Bohr Shift

Answer 28

When an increase in blood carbon dioxide and a decrease in pH results in a reduction of the affinity of haemoglobin for oxygen. Additional oxygen release from haemoglobin at lower blood pH.

Question 29

What 3 factors are responsible for the increase in dissociation of oxygen from haemoglobin?

Answer 29

• Increase in blood temperature - Higher temperature = readily dissociation • Partial Pressure of carbon dioxide increase - Oxygen dissociates faster • pH

Question 30

Venous Return Definition

Answer 30

The return of blood to the right side of the heart via the vena cava

Question 31

Cardiac Conduction System definition

Answer 31

The conduction system involves the electrical impulses that cause the cardiac cycle of the heart. The cardiac muscle is myogenic, meaning it generates its own impulses.