The Circulatory System 2

Question 1

what is the arctic arch?

Answer 1

fat covered on the heart

Question 2

what is the heart?

Answer 2

a hollow, 4 chambered muscular organ

Question 3

where is the heart located?

Answer 3

in mediastinum

(section of thoracic cavity)

midline between sternum + vertebrae

Question 4

what is the heart surrounded by?

Answer 4

double layered membrane - pericardium

• inner, visceral pericardium covers full heart (epicardium)
• outer parietal pericardium attaches to vessels, sternum + diaphragm
• pericardial activity contains 30-50 ml serous fluid

Question 5

the heart functions as 2 separate functional pumps.

describe this?

Answer 5

• each pump divided into upper chamber + lower chamber
• upper chambers open into lower chambers via valve (tricuspid / mitral)
• left + right pumps separated by septum

Question 6

right sided pump

Answer 6

pulmonary circulation + gaseous exchange

• receives DE-OXYGENATED blood from systemic circulation
• pumps into lungs for re-oxygenation + CO2 removal

ventricle opens into pulmonary artery via pulmonic valve

Question 7

left sided pump

Answer 7

systemic circulation + O2 + nutrient supply

• receives re-oxygenate blood from lungs (p.circulation)
• pumps into systemic circulation

ventricle opens into aorta via aortic valve

Question 8

what are the 2 main types of blood vessels in the heart?

Answer 8

• great cardiac vessels

- the coronary vessels

Question 9

great cardiac vessels

Answer 9

carry blood to + from heart chambers and systemic + pulmonary circulations

inc:

• superior + inferior vena cava
• pulmonary artery
• pulmonary veins
• aorta

Question 10

coronary vessels

Answer 10

= coronary circulation - specialised blood supply system of heart

inc:

• left + right coronary arteries
• coronary sinus, great/middle/anterior + posterior cardiac veins, thebesian veins

Question 11

aorta

Answer 11

• accepts output of left ventricle
• 1st vessel of systemic circulation
• has highest systolic pressure ~140mmHg

Question 12

pulmonary artery

Answer 12

• accepts output of right ventricle
• 1st vessel of pulmonary circulation
• has peak pressure ~25mmHg

Question 13

superior vena cava / inferior vena cava

Answer 13

largest vessels returning deoxygenated blood to right atrium from s.circulation

Question 14

pulmonary veins

Answer 14

largest vessels returning oxygenated blood to left atrium from p.circulation

Question 15

coronary arteries + veins

Answer 15

supply blood to cardiac muscle tissue

branch off from aorta above aortic valve

veins drain blood into right atrium

Question 16

coronary circulation

myocardial O2 + nutrient demand

Answer 16

• heart beats constantly through life

- needs constant + adequate supply of oxygen + nutrients

Question 17

coronary circulation

myocardial O2 + nutrient supply

Answer 17

• supplied by special network of blood vessels

- made of left + right coronary arteries

Question 18

coronary circulation

delicate balance between demand + supply

Answer 18

• reduced coronary blood flow during systole
• disproportionate share of cardiac output
• high O2 extraction -> low O2 reserve

Question 19

what are the benefits of having a one-way opening valve?

Answer 19

• prevents back flow of blood

- ensures unidirectional flow of blood through heart

Question 20

AV valves

Answer 20

• TRISCUPID valve - bet. right atrium + ventricle

- BICUSPID/MITRAL valve - bet. left atrium + ventricle

Question 21

semilunar valves

Answer 21

• PULMONIC valve - bet. right ventricle + pulmonary artery

- AORTIC valve - bet. left ventricle + aorta

Question 22

AV heart valves in function process

Answer 22

• blood returns to heart
• fills atria
• puts pressure against AV vales -> open
• as ventricles fill, AV valves flap -> hang limply into ventricles
• atria contract -> forcing extra blood into ventricles
• ventricles contract -> forcing blood against AV valves cusps
• AV valves close
• papillary muscles contract + chordae tendineae tighten
• prevents valve flaps everting into atria

Question 23

semilunar heart valves in function process

Answer 23

• ventricles contract, intraventricular pressure rises
• blood pushed up against SL valves—> open
• as ventricles relax, intraventricular pressure falls
• blood flows back from arteries
• fills cusps of SL valves + forces them to close

Question 24

what are the 3 layers the heart wall consists of?

Answer 24

• endocardium
• myocardium
• epicardium

Question 25

endocardium

Answer 25

- innermost thin lining of endothelial cells - allows smooth flow of blood - prevents clotting

Question 26

myocardium

Answer 26

- middle layer - made of cardiac muscle | - forms bulk of heart wall

Question 27

epicardium

Answer 27

- protective outer layer | - embeds coronary blood vessels

Question 28

what are the 2 main SPECIALISED types of heart cells?

Answer 28

- contractile cells | - electrical / autorhythmic cells

Question 29

contractile cells

Answer 29

- 99% of heart cells - mainly in myocardium + septum - mediate mechanical, pumping work of heart - form interlacing bundles - arranges spirally around circumference of heart - electrically quiescent - comprise: atrial + ventricular muscle cells

Question 30

what does electrically quiescent mean?

Answer 30

do not normally initiate own AP

Question 31

electrical/autorhythmic cells

Answer 31

- don't contract - specialised for initiating + conducting AP -> activation + contract of muscle cells inc: SAN, AVN, Bundle of His, purkinje fibres

Question 32

cardiacs RMP

Answer 32

- at rest = POLARISED (inside = NEG) - unequal distrib of ions across membrane - opening + closing of ion channels = voltage + time-dependent - K+ channels selectively open in memb at rest (RMP = CLOSER to K+ equilib potential) - slow spontaneous depolarisation in automatic cells

Question 33

define excitability?

Answer 33

ability of cardiac cells to respond to electrical stimulus by firing AP

Question 34

fast AP

Answer 34

high conduction velocity ~1-4m/s

Question 35

slow AP

Answer 35

slow conduction velocity ~0.02-0.1m/s - more easily blocked - liable to conduction failure at high repetition rates

Question 36

define refractoriness?

Answer 36

inability of more than enough stimulus to elicit an AP

Question 37

refractoriness of cardia cells

Answer 37

- happens for some time after previous AP | - gives rise to ABSOLUTE/EFFECTIVE ARP/ERP + relative refractory periods

Question 38

what are the benefits of the refractory period?

Answer 38

protects against premature excitation + tetany

Question 39

time of recovery for fast response

Answer 39

faster recovery of excitability

Question 40

time of recovery for slow response

Answer 40

slower recovery of excitability —> inc risk of conduction block