OPTION D.4-Heart

Question 1

What are the shape of cardiac muscles?

Answer 1

Y-shaped

→ joined end-to-end in a complex network of interconnected cells

Question 2

Intercalated disc

Answer 2

Specialised junction where the end of one muscle cell comes in contact with the end of another muscle cell

Question 3

The difference between cardiac muscle and skeletal muscle?

Answer 3

+ Cardiac muscles are shorted and wider
+ commonly they only have one nucleus per cell
+ many contract even w/ absence of stimulus from nerves

Question 4

What does the intercalated disc consist of?

Answer 4

Double membrane containing gap junctions = provide channels of connected cytoplasm betw/ the cells

Question 5

What does the connected cytoplasms betw/ the cells of the heart muscle allow for?

Answer 5

Rapid movement of ions and a low electrical resistance.

Question 6

What does being interconnected cuz of Y-shape and being electrically connected cuz of gap junctions allow the heart muscles to do?

Answer 6

Allows for a wave of depolarisation to pass easily from one cell to a network of other cells
→ leading to the synchronisation of the contractions

Question 7

How does the contraction from the SA node travel really rapidly through the heart muscles?

Answer 7

+ The gap junctions allow electric charges to flow freely betw/ the cells = contractions that originate in the SA node spreads really rapidly through the heart muscles

Question 8

What is the mechanism that staggers the contraction of the atria and the ventricles?

Answer 8

+ The fibres which connect the SA node to the AV node carry the action potential relatively slow

Question 9

How long is the delay between the arrival of the stimulus from the SA node and the initiation of the impulse with the ventricles?

Answer 9

0.12 sec

Question 10

Which cells take longer to become excited, the SA node or the AV node?

Answer 10

AV node

Question 11

What are the 4 features of the AV node that lead to a delayed initiation of contraction of the ventricles by the AV node?

Answer 11

1) AV node cells hv. smaller diameter and don’t conduct as quickly
2) There are less Na+ channels in the membrane of AV node cells
→ more negative resting potential and a prolonged refractory period within the cells of AV node
3) Fewer gap junctions betw/ cells of AV node
4) More non-conductive connective tissue in the node

Question 12

Why is the delay in contraction caused by the AV node important?

Answer 12

It ensures that the atria contracts and empty the blood into the ventricles before the ventricles contract.
→ contraction of ventricles too early = lead to too small vol. of blood entering the ventricle.

Question 13

What is the route of the signal from the AV node?

Answer 13

+ Atrioventricular bundle receives impulse
+ conducts signal rapidly until pt. where splits into left and right bundle
+ At apex (base) branches connect to Perkinje fibres = conduct signal even more rapidly to the ventricle

Question 14

Modifications of the Perkinje fibres that facilitate the conduction of signals at such a high speed (4)

Answer 14

+ hv. relatively fewer myofibrils
+ Bigger diameter
+ Higher densities of voltage-gated Na channels
+ High #’s of mitochondria and High glycogen stores

Question 15

Where does the contraction of the ventricles begin?

Answer 15

At the Apex

→ it pushes upwards

Question 16

What causes the “lub” sound?

Answer 16

Atrioventricular valves ‘Shut’

Question 17

What causes the “dub” sound?

Answer 17

Semilunar valves shut

Question 18

What are the 2 options of help that the artificial pacemaker can provide to a patient?

Answer 18

1) regular impulse
2) discharge only when a heartbeat is missed
→ it monitors the heart’s rhythm and when it doesn’t beat the ventricle is stimulated w/ a low voltage pulse.

Question 19

What is cardiac arrest?

Answer 19

When the blood supply to the heart becomes reduced and the heart tissues are deprived of oxygen.

Question 20

How are the 2 paddles of a defibrillator applied to a patient’s chest?

Answer 20

The 2 paddles are aligned setting up a diagonal line betw/ the 2 paddles with the heart in the middle.

Question 21

How does a defibrillator work?

Answer 21

+ it will first detect whether or not there is fibrillation happening in the heart
→ then if there is, an electrical charge is given off to restore normal heart rhythm

Question 22

What is Atherosclerosis?

Answer 22

The hardening of the arteries caused by the formation of plaque on the inner lining of the arteries

Question 23

What is a thrombosis?

Answer 23

A blood clot

Question 24

What is Myocardial infarction?

Answer 24

Heart attack

Question 25

What causes hypertension?

Answer 25

The greater resistance to the flow of blood = slow down the blood = greater pressure on the walls of the arteries

Question 26

What is one of the consequence of hypertension?

Answer 26

1) Damage of the cells that line the arteries

→ lead to arteries becoming narrower and stiff

Question 27

What can constant high blood pressure cause?

Answer 27

weaken the arteries causing a section in the wall to enlarge and form a bulge = aneurysm = can burst = internal bleeding

Question 28

What can chronic high blood pressure cause? (2)

Answer 28

1) lead to stroke
→ by weakening blood vessels in the brain causing them to narrow, leak, rupture
→ can lead to blood clot in arteries leading to brain = cause strokes
2) Kidney failure
→ damages both arteries leading to the kidney and capillaries within the glomerulus

Question 29

Factors that correlate to the greater incidence of thrombosis and hypertension (4)

Answer 29

1) Genetic precondition = having parents who hv experienced heart attack
2) Smoking causes high bp cuz nicotine causes vasoconstriction
3) Sedentary lifestyle = lack of exercise correl. w/ obesity and prevents the return of venous blood from extremities = lead to greater risk of clot formation
4) Lower levels of oestrogen
→ males and females after menopause = have higher risk

Question 30

Blood pressure measured in?

Answer 30

mm Hg

Question 31

What does the higher number represent in bp?

Answer 31

Pressure in the artery caused by ventricular systole

Question 32

What does the lower number represent in bp?

Answer 32

Pressure in the artery due to ventricular diastole

Question 33

What is the instrument used to measure bp called?

Answer 33

Sphygmomanometer

Question 34

What is a normal bp?

Answer 34

Systolic = less than 120
Diastolic = less than 80

Question 35

The Cardiac cycle (6)

Answer 35

1) Isometric Relaxation
2) Rapid Filling
3) Diastasis
4) Atrial Systole
5) Isometric contraction
6) Ejection