Circulation

Question 1

Functions of the circulatory system

Answer 1

• Transport oxygen and nutrients to cells.
• To remove waste away from cells.
• Distribute hormones to cells.
• Extracellular fluid homeostasis.
• Thermoregulation.
• Immune defence (wbcs)

Question 2

Explain how a mercury sphygmomanometer works?

Answer 2

Sphygmomanometer: device to measure blood pressure.

1. The arm cuff is placed on the upper arm and pressure is applied until the brachial pulse can not longer be felt.
2. This pressure is above the systolic pressure of the individual, as it is able to overcome the systolic pressure and squeeze the vessels shut.
3. Pressure is slowly relieved from the cuff and Korotkoff sounds are listened to.
4. First clocks heard indicate the opening/ closing of the blood vessels. This indicates the systolic pressure. The clicks being heard are a result of turbulent blood flow.
5. The clicks get quieter as the flow becomes more laminar. When the clicks disappear, blood flow is completely laminar, this is the diastolic pressure.

Question 3

Perfusion

Answer 3

Flow of blood in the vessels to tissues.

Requires a sufficient pressure gradient.

Insufficient perfusion= shock/ hypotension.

Question 4

Distribution of blood in the body

Answer 4

Veins holds the mass majority- 64%

Question 5

Blood pressure equations

Answer 5

BP= Cardiac output x peripheral resistance

BP= Circulating blood volume + circulatory capacity

Question 6

Apex beat

Answer 6

Occurs when the apex of the heart strikes the chest wall as systole.

Question 7

Circulatory capacity

Answer 7

Volume of space that can contain blood.

Influenced by:
Number of blood vessels.
Vasoconstriction.

Question 8

Hypoxemia

Answer 8

Low oxygen content in arterial blood supply.

Leads to hypoxia- low O2 in the tissues.

Causes: due to poor oxygenation of blood, indicating respiratory problems.
Ventilation-perfusion mismatch.
Hypoventilation
Shunt- abnormal hole that allows fluid to move from one part of a tissue to another (i.e between left and right ventricle)

Question 9

Hypoxia

Answer 9

Low oxygen content in tissues.

Hypoxaemia always leads to hypoxia (hypoxemic hypoxia)
Can also be caused by:
Obstruction of blood flow (i.e clot)
Gangrene

Question 10

Anemia

Answer 10

Low oxygen content in the blood due to low haemoglobin content.

The blood can still be adequately ventilated but still lead to hypoxia due to low O2 delivery to tissues.

Question 11

Anoxia

Answer 11

No oxygen supply to tissue locally.

Question 12

Ischemia

Answer 12

Lack of blood flow to tissue, more likely leading to hypoxia and infarction.

Causes:
Obstruction of blood flow in vessels (clot, constriction, closed vessel).
Hypovolemia
Insufficient pressure generation from the heart.

Question 13

Angina pectoris

Answer 13

Pain in the chest caused by damaged cardiomyocytes.

Causes:
Ischemia in coronary arteries
Coronary heart disease
Embolism in coronary arteries

Treatment:
Nitrates

Question 14

Valves in the heart

Answer 14

Atrioventricular:
Mitral (left)
Tricuspid (right)

Semilunar:
Aortic (left)
Pulmonary (right)

All valves normally have three leaflets, except the mitral valve.

Function: prevents backflow of blood into previous chambers

Question 15

Chordae tendineae

Answer 15

Tendons that connect the mitral and tricuspid valve to the papillary muscles.

They relax when the valves open during atrial systole and are tense during ventricular systole, to prevent back flow into atrium.

Question 16

Treatment of myocardial infarction:

MONA

Answer 16

Morphine- pain management

Oxygen- prevents hypoxia

Nitrates- vasodilation, increases blood flow

Aspirin- prevents clots

Question 17

Control of blood volume by the kidneys

Answer 17

NaCl reabsorption into the blood occurs in the kidneys.

Absorption of NaCl causes further absorption of water= increases blood volume= increases blood pressure.

Reabsorption of NaCl influenced by aldosterone.

ADH acts on collecting duct to prevent diuresis. Increased ADH= increased blood volume = increased BP

Question 18

Glomerular filtration rate (GFR)

Answer 18

The volume of fluid filtered from the glomerulus to the Bowman’s capsule in a minute.

Filtration rate is controlled by the afferent and efferent arterioles. Dilation of afferent arteriole and constriction of efferent= higher pressure.

Increase GFR= increased urine output.

Question 19

Filtration of blood in the kidneys

Answer 19

The blood enters the kidneys via renal artery and ultrafiltration occurs at the glomerulus.

Glucose, urea and water are absorbed in the kidneys whilsts larger molecules like rbc and large plasma proteins stay in blood.

Reabsorption of molecules enter peritubular capillaries.

Question 20

Heart failure

Answer 20

Occurs when there is insufficient blood being pumped out of the heart.

Causes:
Mainly previous myocardial infarction (low output chronic)
Dilated cardiomyopathy
Viral myocarditis

Symptoms:
Fatigue
Oedema
Dyspnea (congestive)

Question 21

Syncope

Answer 21

Loss of consciousness caused by insufficient perfusion to the brain.

Causes:
Shock
Hypovolemia
Arrhythmia

Question 22

Shock

Answer 22

Low perfusion due to blood pressure below 90 mm Hg.