Mass Transport In Mammals 3 - Cardiac Cycle & Cardiac Output

Question 1

Why is the heart important in the cardiac cycle?

Answer 1

Stimulus for contraction of the heart originates from within the cardiac muscle
So the heart is MYOGENIC

Question 2

What does myogenic mean?

Answer 2

A characteristic of cardiac muscle where it can initiate its own contractions without the need for nervous stimulation

Question 3

Name the 4 stages of the cardiac cycle

Answer 3

Diastole
Atrial systole
Ventricular systole
Diastole 2

Question 4

What happens during diastole?

Answer 4

Atrial filling
Blood moves from a vein into atria down a pressure gradient

Question 5

Which vein goes into the heart and allows blood to flow into atria in diastole?

Answer 5

Vena cava

Question 6

What happens during atrial systole?

Answer 6

Atria contract
Pressure in atria is higher than ventricles
Cuspid valves open and blood moves from atria to ventricles

Question 7

Another name for cuspid valves?

Answer 7

Atrioventricular (AV) valves
easy to remember as they’re between the ATRIA and VENTRICLES

Question 8

What happens during ventricular systole?

Answer 8

Atria relaxes
Ventricle contracts
Pressure increases above atrial pressure so cuspid valves close
Pressure increase above arteriole pressure so semi-lunar (SL) valves open
Blood ejected into arteries

Question 9

What happens during diastole 2?

Answer 9

Ventricles relax
Pressure drops below arteriole pressure so SL valves close

Question 10

State the equation for cardiac output

Answer 10

Cardiac output = heart rate (HR) x stroke volume (SV)

Question 11

What is heart rate and what factors affect HR?

Answer 11

HR = frequency of the heartbeat measured by the number of contractions of the heart per minute
Autonomic intervention
Fitness levels
Hormones

Question 12

What is stroke volume and what factors affect SV?

Answer 12

SV = volume of blood pumped per beat
Heart size
Gender
Contractility

Question 13

What and where is the CCC?
What is the CCC made up of?
What is the CCC controlled by?

Answer 13

CCC = cardiovascular control centre
Located in the medulla oblongata
Made up of cardio-inhibitory and cardio-acceleratory
Controlled by the ANS (autonomic nervous system)

Question 14

What is in the ANS?

Answer 14

Sympathetic nerve ~ fight or flight
Parasympathetic nerve ~ feed and breed

Question 15

What detects blood pressure and where are they?

Answer 15

Baroreceptors in the aorta and carotid artery

Question 16

What do the baroreceptors do?

Answer 16

They send never impulses along sensory nerves to cardio-regulatory centres in the medulla

Question 17

What happens when blood pressure is low?

Answer 17

The CCC sends nerve impulses -> sympathetic acceleratory nerve -> SAN = increases heart rate

Question 18

How do the sympathetic neurones increase heart rate?

Answer 18

Secrete noradrenaline
Binds to receptors in SAN
Increasing rate of impulses from SAN to heart muscle
Increases heart rate

Question 19

What happens when blood pressure is high?

Answer 19

The CCC sends nerve impulses -> parasympathetic vagus nerve -> SAN = decreases heart rate

Question 20

How do parasympathetic neurones decrease heart rate?

Answer 20

Secrete acetylcholine
Binds to receptors in SAN
Decreases rate of impulses from SAN to heart muscle
Decreases heart rate

Question 21

What detects O2 and CO2 concentration of blood and where are they?

Answer 21

Chemoreceptors in medulla, aorta and carotid artery

Question 22

List 3 factors affecting the CCC

Answer 22

Neural control
Hormonal control (adrenaline)
Intrinsic control (venous return)