The Circulatory System

Question 1

where does the right atrium receive blood from?

Answer 1

superior vena cava, inferior vena cava, coronary sinus

Question 2

where does the right ventricle receive blood from, and send blood to?

Answer 2

receives blood from the right atrium, sends blood to the lungs

Question 3

where does the left atrium receive blood from?

Answer 3

pulmonary veins

Question 4

where does the left ventricle receive blood from, and send blood to?

Answer 4

receives blood from left atrium. sends blood all over the body

Question 5

what is the pericardium?

Answer 5

the thin sac surrounding the heart

- keeps heart contained in chest cavity, prevents heart from over-expanding, limits heart motion

Question 6

what are the layers of the heart wall?

Answer 6

epicardium: outer protective layer
myocardium: muscular middle layer
endocardium: inner layer

Question 7

what structures enable the myocardium to behave as a single coordinated unit?

Answer 7

intercalated discs (zone between adjacent cardiomyocytes) contain two types of cell junctions:

• desmosomes: anchoring junctions, keep heart from pulling itself apart
• gap junctions: allow the electrical impulse to move from cell to cell so heart beats synchronously

Question 8

why do cardiac cells have many mitochondria?

Answer 8

because the heart is extremely active and requires a lot of energy to constantly pump blood through circulatory system

Question 9

why is the myocardium of the left ventricle thicker than that of the right ventricle?

Answer 9

right pumps blood to adjacent lungs.

left pumps to the rest of the body.

Question 10

in a resting state… is the intracellular fluid of heart cells more negatively charged than extracellular fluid?

Answer 10

yes. the cells are ‘polarised’ - when electrically stimulated by another cell, the permeability of the cell membrane to positive charged ions increases

Question 11

what is an ECG?

Answer 11

electrocardiogram - sum total of electrical changes of individual cells

Question 12

define depolarisation

Answer 12

electrical activation of the myocardium

Question 13

define repolarisation

Answer 13

restoration of electrical potential of the heart

Question 14

define systole

Answer 14

contraction of the heart

Question 15

define diastole

Answer 15

relaxation of the heart

Question 16

steps of action potential movement through the heart

Answer 16

1. depolarisation of atrial contractile fibres (P wave)
2. atrial systole
3. depolarisation of ventricular contractile fibres (QRS complex)
4. ventricular systole
5. repolarisation of ventricular contractile fibres (T waves)
6. ventricular diastole

Question 17

what is the SA node?

Answer 17

sinoatrial node - pacemaker of the heart

- fires at regular intervals to cause the heart beat at 60-70bpm for a healthy resting heart

Question 18

outline the sequence of excitation during cardiac conduction

Answer 18

1. SA node
2. through atria
3. atrio-ventricular node
4. atrio-ventricular bundle
5. R& L branches
6. purkinje fibres (ventricular contraction)

Question 19

what are some influences on the conduction system?

Answer 19

neurotransmitters and hormones from sympathetic nervous system can modify the heart rate and force of contraction, do not set fundamental rhythm

• parasympathetic nervous system releases acetylcholine
• heart is under parasympathetic dominance at rest

Question 20

what does blood flow through coronary arteries do?

Answer 20

delivers oxygenated blood and nutrients the myocardium

Question 21

what does blood flow through coronary veins do?

Answer 21

removes carbon dioxide and wastes from the myocardium

Question 22

define cardiac output.

Answer 22

the volume of blood ejected from the left or right ventricle into the aorta or pulmonary trunk each minute

Question 23

define stroke volume.

Answer 23

the amount of blood pumped out of the ventricle in one beat

Question 24

what is the cardiac output formula?

Answer 24

CO(mL/min) = SV (mL/beat) x HR (beats/min)

Question 25

what are factors affecting stroke volume?

Answer 25

1. preload: amount of ventricular stretch at the end of diastole
2. contractility
3. afterload: amount of resistance the heart must overcome to open the aortic valve and push the blood volume out into the systemic circulation

Question 26

what is the function of heart valves?

Answer 26

controls flow of blood through the heart, preventing back flow

Question 27

identify each heart valve.

Answer 27

• tricuspid valve
• pulmonic or pulmonary valve
• mitral (bicuspid) valve
• aortic valve

Question 28

identify each layer of blood vessels.

Answer 28

1. tunica interna - innermost layer
2. tunica media - middle layer, smooth muscle and elastic fibres
3. tunica externa - outermost layer, adjacent to surrounding tissue

Question 29

describe the difference between arteries and veins.

Answer 29

arteries are built to endure exposure to much greater pressure than veins
- arterioles can constrict and dilate due to smooth muscle. elastic tissue enables arteries to withstand greater pressure

veins are capacitance vessels and have little elastic.
- veins operate at low pressure, low speed and possess values to prevent back flow

Question 30

why is the radius/diameter of blood vessels important?

Answer 30

radius/diameter of blood vessels are one of the most important ways we can regulate BP, and adapt to environmental changes.

Question 31

what is an anastomosis?

Answer 31

union of the branches of 2 or more arteries supplying blood to the same region of the body - alternate route for blood flow

Question 32

what are capillaries?

Answer 32

microscopic vessels that connect arterioles and venules

Question 33

what are venules?

Answer 33

small vessels that are formed by union of several capillaries

Question 34

what are veins?

Answer 34

formed from union of several venules

Question 35

what is blood pressure, and what is it determined by?

Answer 35

the pressure exerted by the blood against the walls of arteries
- determined by cardiac output and vascular resistance

Question 36

what is resistance, and what does it depend on?

Answer 36

the opposition to blood flow due to friction between blood and the walls of blood vessels - higher resistance = smaller blood flow

• depends on:
  1. diameter of blood vessel lumen
  2. blood viscosity
  3. total blood vessel length
  4. arterial stiffness

Question 37

how is blood pressure regulated?

Answer 37

• medulla oblongata contains cardiovascular centre, which is a group of neurons that regulate heart rate, contractility and blood vessel diameter
• hypothalamus also contains cardiovascular centre (sympathetic only)
  baroreceptors: pressure-sensitive sensory neurons that monitor stretching of the walls of the blood vessels and atria

Question 38

what is auto regulation of blood pressure?

Answer 38

ability of tissue to automatically adjust own blood flow to match metabolic demand for delivery of oxygen and nutrients and removal of wastes

Question 39

what is the mean arterial pressure? (MAP)

Answer 39

MAP = CO x total peripheral resistance

Question 40

what are the major components of blood?

Answer 40

plasma (55%)

cells (45%)

Question 41

state the major functions of blood?

Answer 41

• transportation (dissolved gases, wastes, hormones, enzymes, nutrients etc.)
• maintain body temp
• controls pH
• removes toxins from body

Question 42

state the types of white blood cells.

Answer 42

• basophils: release histamine, cause hypersensitivity reactions/asthma attacks
• neutrophils: role in acute inflammatory response
• eosinophils: digest bacteria and pathogens
• monocytes: phagocytic cells
• lymphocytes: chronic inflammation and long term immunity