the heart as a pump

Question 1

what does the cvs consist of

Answer 1

• the heart
• blood
• blood vessels of vascular system

Question 2

what are the major cardiovascular functions

Answer 2

• delivery
• removal
• transport
• maintenance
• prevention

Question 3

where is the heart located

Answer 3

the pericardium -
a fluid called membranous sac

Question 4

what is the epicardium

Answer 4

the covering of the heart itself, the interlining of the pericardium is continuous with it

Question 5

what are walls of the heart composed of

Answer 5

cardiac muscle cells (the myocardium)

Question 6

what is the endocardium

Answer 6

the inner surface of walls that is in contact with blood

Question 7

layers of the heart wall

Answer 7

outer layer - epicardium
middle layer - myocardium
inner layer - endocardium

Question 8

FUNCTION of epicardium

Answer 8

serves as lubricative outer covering

Question 9

function of myocardium

Answer 9

provides muscular contractions that eject blood from the heart chambers

Question 10

function of endocardium

Answer 10

serves as protective inner lining of the chambers and valves

Question 11

what does the AV valve do

Answer 11

prevents flow from the ventricles back into the atrium

Question 12

name of right and left AV valve

Answer 12

right - tricuspid valve
left - mitral valve

Question 13

what does the pulmonary valve do

Answer 13

prevents the back flow from the pulmonary trunk into the right ventricle

Question 14

what does the aortic valve do

Answer 14

prevents the flow back from the aorta into the left ventricle

Question 15

what is the cardiac cycle

Answer 15

the electrical and mechanical changes that occur in the heart during and following a single heart beat

Question 16

what are two two phases of the cardiac cycle

Answer 16

• the contraction phase (systole)
• the relaxation (filling) phase (diastole)

Question 17

what does alternation of contraction and relaxation allow

Answer 17

movement into and within the heart

always following the path of least resistance (pressure)

Question 18

what is cardiac eject fraction

Answer 18

the amount of blood ejected (LV)/min

formula:
stroke volume (left ventricle contraction) / EDV x 100

Question 19

how to calculate stroke volume

Answer 19

(end diastolic volume (EDV) minus end systolic volume (ESV) ) / EDV

Question 20

what does EF depend on

Answer 20

• volume
• heart chamber dimensions
• ventricular heart rate
• valve function
• preload and after load

Question 21

what is preload

Answer 21

the pressure of the blood on the ventricles at the end of diastole

Question 22

what is afterload

Answer 22

the pressure in the wall of the left ventricle during ejection

Question 23

where does the depolarisation stimulus for the normal heartbeat originate

Answer 23

the sinoatrial node

Question 24

what causes the depolarisation stimulus

Answer 24

a collection of pacemaker cells which fire spontaneously

they exhibit automaticity

Question 25

what type of cells are pacemaker cells

Answer 25

myocytes NOT nerve cells

Question 26

where do nerve cells stop

Answer 26

at the SA node

Question 27

do other cells in the heart exhibit spontaneous automaticity

Answer 27

yes
but in normal conditions the pacemaker cells are those in which show the highest rhythm

(why in healthy normal hearts depolarisation originates from the SA)

Question 28

control of heart rhythm

Answer 28

1. pacemaker generates wave of signals to contract
2. signals delayed at AV node
3. signal pass to heart apex
4. signal spreads through ventricles

Question 29

what acts as cardiac pacemaker

Answer 29

the SA node

Question 30

what is the normal sinus rhythm

Answer 30

60-100 bpm

Question 31

what does depolarisation trigger

Answer 31

depolarisation of atrial myocardium

Question 32

where does the sinus rhythm conduct more rapidly

Answer 32

through AV node

through His bundles and Purkinje fibres

Question 33

what modulates the frequency of heartbeat, HR and force of contraction

Answer 33

the ans

Question 34

do hearts without nervous and endocrine inputs still beat

Answer 34

yes

Question 35

where is the capability of generating rhythmic sponaneous action pontentials most developed

Answer 35

in a small number of cells in the SA node

Question 36

can other areas start rhythmic spontaneous action potentials

Answer 36

yes but their rates are lower than that of the SA

as a result, the entire system is normaly driven by the SA node

Question 37

are cardiac myocytes electrically excitable

Answer 37

yes

Question 38

what is the resting intracellular voltage of myocardial cells

Answer 38

its negative, -90mV

(SA node is -40mV)

Question 39

what is the resting state of the heart (sodium, potassium)

Answer 39

K+ inside the cell
and
Na+ outside the cell

Question 40

when does an action potential occur

Answer 40

when Na+ enters the cell and sets up a depolarising current

Question 41

what does stimulation of a single muscle fibre cause

Answer 41

electrical activity to spread across the myocardium

Question 42

are myocardium cells nerve cells

Answer 42

NO

Question 43

contraction of cardiac muscle steps

Answer 43

1. electrical excitation
2. calcium entry (Na+/K+)
3. Mechanical contraction

Question 44

can after load and preload affect contraction of cardiac muscle

Answer 44

yes