Cardio 2

Question 1

What is the difference betweenmyogenic and neurogenic hearts?

Answer 1

Neurogenic hearts need neural input to beat, while myogenic hearts contain cells with the intrinsic capability to beat

Question 2

Membrane potential of pace maker cells occurs due to…

Answer 2

increase flow of Na, decreased outward flow of K and increased flow of Ca; an action potential is produced when the L-type channels open at threshold; the large influx of Ca causes rapid depol

Question 3

How is the signal in the heart propagated past the electrically non-conductive fibrous tissue?

Answer 3

through the AV node

Question 4

SA node contains the pace maker cells; if tehy died, other cells would take over

Answer 4

ye

Question 5

What does the PR segment show?

Answer 5

AV nodal delay

Question 6

What does the S-T segment show?

Answer 6

Plateau phase

Question 7

What does the T-P segment show?

Answer 7

Passive ventricular filling while all chambers are at rest

Question 8

What is the equation for mean arterial pressure?

Answer 8

systolic pressure + 1/3 (systolic-diastolic pressure) or cardiac output X total peripheral resistance

Question 9

Cardiac output equation

Answer 9

heart rate X stroke volume

Question 10

How can teh flow resistance be altered?

Answer 10

By chaning arterial radius but contraction or relaxation of smooth muscles

Question 11

What are the mechanisms that regulate arterial blood pressure?

Answer 11

ANS, autoregulation, hormonal/humoral

Question 12

What are the major resistance vessels and why?

Answer 12

Arterioles and because they have a small diameter to offer considerable resistance

Question 13

Major pressure drop going from arteries to arterioles

Answer 13

ye

Question 14

where are pulsatile pressure swings eliminated and why?

Answer 14

in the artieroles and because they have a much lower pressure

Question 15

remember that the arterioles have thick layers of smooth muscle cells innervated by SYMPATHETIC nerve fibres

Answer 15

ye

Question 16

Where is autoregulation most important?

Answer 16

Brain, heart, kidney

Question 17

What is extrinsic control of the blood flow?

Answer 17

neurol and hormonal infleunces with the sympathetic NS dominating

Question 18

Sympathetic stimulation resdistributes teh flow of blood to heart and skeletal muscle by:

Answer 18

Releasing NE or Epinephrine which bind to alpha1-andrenic receptors on most arterioles causing vasconstriction; the lungs and brain do not contain these receptors thus they do not constrict; epinephrine activates beta2-andregenic receptors which causes vasodilation in the heart and skeletal muscles

Question 19

Sympathetic NS constricts veins, enhancing venous return which increased end diastolic volume; more blood is pushed out of the ventricles and therefore stroke volume increases, so cardiac output increases

Answer 19

ye

Question 20

What do baroreceptors do?

Answer 20

Sense a stretch in artery walls during systole; they release action potentials in increasing frequency of pulses the higher MAP is

Question 21

Where is renin released, and what stimulates it?

Answer 21

Released by the kidneys, due to sympathetic system, hypotension, and decreased sodium delivery

Question 22

What is tehend goal of ANG II and Renin cycle?

Answer 22

To increase arterial pressure

Question 23

Renin and angiotensin combine to form angiotensin I due to sympathetic stimulation, hypotension; and sodium delivery; this leads to an increase of aldosterone from the adrenal cortex which will cause renal sodium and fluid retention which increases blood volume (as does thirst) which will lead to higher cardiac output’ along with systemic vasoconstriction, cardiac output will cause an increase in arterial pressure

Answer 23

ye