Circulation of Blood

Question 1

What are the functions of the CVS?

Answer 1

• flow of materials (gases/nutrients/hormones/waste)
• temperature regulation
• homeostasis (fluid balance, prevents accumulation of fluid/dehydration of tissues)
• host defence
• reproduction

Question 2

What ventricle of the heart is thicker and for what reason?

Answer 2

The wall of the left ventricle is thicker than the right due to the increase of forces required to pump blood round systemic circulation

Question 3

What is the advantage of the CVS having a parallel arrangment?

Answer 3

If blood supply is obstructed going through one route or to one organ there will be other routes the blood can get through (independent regulation of blood flow)

Question 4

What connects arterioles to capillaries and what is its function?

Answer 4

Pre-capillary sphincters which control the blood flow to capillary beds

Question 5

Explain blood flow of the CVS

Answer 5

During diastole the bicuspid mitral valve opens to allow blood to flow from the left atrium to the left ventricle, then in contraction during systole the valve snaps shut pushing the blood through the aortic valve to the aorta which distributes the blood around the body. The blood returns by the SVC/IVC to the atrium through the tricuspid valve to the right ventricle. During systole the contraction pushes the blood against the pulmonary valve which opens and sends blood through pulmonary circulation

Question 6

Atrioventricular valves

Answer 6

• mitral and tricuspid
• flimsy
• prevent backflow of blood
• have papillary muscles attaches to the chordinae tendinae of the valve the prevent backflow of blood into the atrium

Question 7

Semilunar valves

Answer 7

• aortic and pulmonary
• both tricuspid
• more heavy duty to withstand higher pressures

Question 8

Describe what is contained in cardiac muscle

Answer 8

• cells are branched to allow rapid spread of activity
• connected by intercalated disks which contain gap junctions and desmosomes
• gap junctions aid the spread of electrical activity from one cell to the next by allowing the passage of ions
• desmosomes are adhesive
• striated with actin and myosin thick and thin filaments

Question 9

Explain how muscle fibres in cardiac muscle conduct activity

Answer 9

1% of fibres don’t contract and instead form excitatory and conductive fibres

Question 10

Explain how CNS innervation affects the sinoatrial node

Answer 10

• sympathetic nerves increase SAN depolarisation rate

- parasympathetic nerves decrease SAN depolarisation rate