The Heart And Cardiovascular System LO

Question 1

Describe the location of the heart

Answer 1

Central but slightly to the left - slightly rotated to the left
Right atrium forms right border
Right ventricle forms inferior border and most of anterior side
Left ventricle forms left border and apex

Question 2

Describe the layers of the pericardium and the heart

Answer 2

Pericardium - outermost layer made of 2 layers:
- fibrous pericardium consists of fibrous tissue
- serous pericardium is a continuous double layer formed by single layer of endothelium cells
Myocardium - specialised cardiac muscle, striated skeletal muscle, rich in mitochondria
Endocardium - thin membrane which lines heart valves and chambers

Question 3

Name the chambers of the heart and the great vessels entering and leaving the heart

Answer 3

Right atrium
Right ventricle
Left atrium
Left ventricle
Superior + inferior vena cava
Aorta
Pulmonary artery
Pulmonary vein

Question 4

Describe function of the blood vessels in the heart

Answer 4

Superior and inferior vena cava bring deoxygenated blood from the body to the right atrium
Pulmonary artery takes deoxygenated blood to the lungs
Pulmonary vein brings oxygenated blood back to the left atrium
Aorta take oxygenated blood to the body

Question 5

Describe where gas and nutrient exchange takes place

Answer 5

Gas exchange takes place in the alveoli where O2 diffuses into the capillaries and CO2 diffuses out
Nutrient exchange also takes place in the capillaries as nutrients are absorbed into the blood stream from the small intestine

Question 6

Explain the cardiac cycle

Answer 6

1) atria fill with blood from superior + inferior vena cava
2) pressure in atria exceeds that in ventricles so valves are pushed open, blood flows passively into ventricles
3) up to 70% of ventricular filling happens due to gravity before contraction
4) atrial systole commences as SA node triggers a wave of contraction, spreading over myocardium
5) when electrical impulse reaches AV node it slows, delaying atrioventricular transmission
6) allows atria to finish emptying before ventricles contract
7) after slight delay AV node triggers its own electrical impulse, spreading to ventricular muscle via AV bundle, bundle branches, purkinje fibres
8) results in wave of contraction, sweeping upwards from apex of heart, across ventricle walls
9) this pumps blood into pulmonary artery and aorta
10) this is followed by complete cardiac diastole where both atria and ventricles are relaxed

Question 7

Describe factors that determine arterial blood pressure

Answer 7

Cardiac output - determined by stroke volume and heart rate. An increase in cardiac output raises both systolic and diastolic blood pressures
Peripheral resistance - heart pumps blood into closed circulatory system against blood that is already there. Affected by diameter of small arteries

Question 8

Explain the baroreceptor reflex

Answer 8

1) Sit within the wall of the aortic and carotid sinuses.
2) They are nerve endings sensitive to pressure.
3) If pressure in the aorta falls baroreceptor firings slow.
4) Cardiovasuclar centre (CVC) responds by increasing sympathetic activity, resulting in an increase in HR and vasoconstriction.
6) Counteracting a fall in blood pressure.

Question 9

Explain how the heart responds to changes in demand

Answer 9

Arteriole can change their diameter.
Contraction of smooth muscle cells in the walls of arterioles causes them to constrict.
Increases resistance of blood flow.
Makes pressure on arteriole side higher.

Question 10

Describe the roles of skeletal muscles and valves in the return of blood to the heart

Answer 10

Veins embedded within skeletal muscle are compressed during contraction causing an increase in blood pressure due to the presence of valves, driving the blood towards the heart

Question 11

Locate the following major arteries: aorta, subclavian, common carotid, internal and external carotids, axillary, brachial, ulnar, radial, femoral, tibial

Answer 11

Aorta - starts at left ventricle, forming an arch and extending down into the abdomen
Subclavian - lies just below the clavicles
Common carotid - neck
Internal carotids - one on each side of the neck
External carotids - run between mandible and lobule
Axillary - starts at outer border of the first rib
Brachial - upper arm, just below shoulder
Ulnar - forearm, closest to pinky
Radial - forearm
Femoral - thigh
Tibial - lower leg

Question 12

Define the pulse and identify the major points for palpitation

Answer 12

Pulse - rhythmical throbbing of the arteries as blood is propelled through them, typically felt in the wrists or neck