The Heart

Question 1

what are the properties of the cardiac muscle

cardiac muscle= thick muscular layer found in heart muscle

Answer 1

• myogenic= muscle can contract + relax without nervous system + hormones
• never fatigues = as long as it has a supply of oxygen

Question 2

compare Atria + Ventricles

Answer 2

Atria:
- thinner muscular walls
- because dont need to contract as hard as only pumping blood to ventricles
- elastic walls - to strength when blood enters

ventricles:
- thicker muscular walls to enable bigger contractions
- —>creates higher blood pressure
- —> to enable blood flow to longer distances (to lungs + rest of body)

Question 3

what are the coronary arteries?

Answer 3

• arteries surrounding heart
• branch off from the aorta
• supply the cardiac muscle with oxygenated blood

Question 4

what happens if the coronary arteries become blocked?

Answer 4

• cardiac muscle wont recieve oxygen
• so cells cannot respire
• cells theefore die
• results in myocardinal infraction (heart attack)

Question 5

what is the bundle of his?

Answer 5

• collection of conducting tissue that transmits electrical activity to apex (bottom of heart) + ventricle walls
• along the purkyne fibres

Question 6

how is the heart beat initiated?

this question is about the FIRST HEART BEAT NOT THE ENTIRE CARDIAC CYCLE

the heart beat is initiated from within the heart itself
the heart DOES NOT require an external signal in order to beat

Answer 6

1) cells in the SAN (sinoatrial node) depolarise/become electrically excited
2) triggers wave of electrical excitation to spread across atria
- causes atria to contract
3) electrical excitation detected by AVN (atrioventricular node)
- there is a short delay…
- to ensure ventricles contract AFTER atria have contracted
4) AVN transmits electrical excitation to bundle of his down the purkyne fibres
5) causes ventricles to contract
- ventricles contract from apex, upwards
- ensures maximum volume of blood is pumped out of ventricles

Question 7

outline what happens in the cardiac cycle

Answer 7

1) blood flows into the atria
- through the vena cava + pulmonary vein

2) causes pressure in atria to increase

3) pressure in atria> pressure in ventricles, causes AV (atrioventricular valves) to open

4) blood flows down from atria to ventricles

5) atria contract, push remaining blood from atria to ventricles
- time delay… (so ventricle contracts AFTER atria)

6) ventricles contract, atria relax
7) pressure in ventricles increases
8) atrioventricular valves close, semi-lunar valves open
9) blood pumped from ventricles into arteries

Question 8

what causes the semi-lunar valves to shut?

Answer 8

• pressure in ventricles falls below pressure in pulmonary artery + aorta
• prevents blood flowing back into ventricles

Question 9

what side of the heart is blood oxygenated?

Answer 9

left side

Question 10

what side of the heart is blood deoxygenated?

Answer 10

right side