Lecture 17 (Regulation of arterial BP and CO)

Question 1

What are the key areas of control for regulation of arteriole pressure and cardiac output (CO)? (3)
What type of outflow goes to each of these? (3)

Answer 1

-Heart (parasympathetic outflow)
-Arteries (sympathetic outflow)
-Veins (sympathetic outflow)

Question 2

What is tachycardia?
an bradycardia?

Answer 2

-Tachycardia is an increase in heart rate and increase in counteractivity which means increase in stroke volume

-Bradycardia is a decrease in the heart rate and counteractivity (it is a minor factor of the control mechanism)

Question 3

How does a tachycardia take place? (5)

Answer 3

-Positive ionotropic activity as a result of stimulation from sympathetic nervous system via noradrenaline from sinoatrial node

-CAMP activation activates currents, mixed Na+ K+ current

-Increase in firing of sinoatrial node, so shortening of time it takes for next firing at level of conducting tissue

-Speeds up repolarization

-Activation for CAMP levels and RYE2 means greater uptake into stores of calcium

Question 4

How does a Bradycardia take place? (3)

Answer 4

-After parasympathetic nervous system stimulation there is flattening of slope

-Because of K+ channel activation we get some hyperpolarization

-Larger tonic inhibition of heart rate, if you sever vagal nerve, it increases heart rate as you get rid of tonic inhibition

Question 5

What are short term neural mechanisms for regulation of arteriole pressure and CO? (3)

Answer 5

-Baroreceptor reflex
-Bainbridge reflex
-Chemoreceptors

Question 6

What are long term humoral mechanisms for regulation of arteriole pressure and CO? (3)

Answer 6

-Endocrine and paracrine agents
AngII
-Adrenaline

-Renal pathways – Na+ handling

Question 7

How is stroke volume (SV) calculated?

Answer 7

Stroke Volume = End Diastolic Volume - End Systolic Volume

SV = EDV - ESV

Question 8

What factors do we have to consider for End diastolic volume (EDV)? (2)
and End Systolic Volume (ESV)? (4)

Answer 8

EDV = filling pressure, filling time

EDS = preload, after load, heart rate, inotropic agents

Question 9

What happens in Baroreceptor reflex? (extrinsic heart mechanisms)(5)

Answer 9

-Inhibit Sympathetic Nervous System (SNS)
-Activation of Peripheral Nervous System (PNS)
-Vasodilatation
-Mean arteriole pressure lowers (MAP)
-Total peripheral resistance lowers (TRP)

Question 10

What happens in hypoxia and acidosis (extrinsic heart mechanisms)? (3)

Answer 10

-Chemoreceptors activate
-Increase heart rate
-Vasoconstriction

Question 10

What happens in Bainbridge reflex (extrinsic heart mechanisms)? (3)

Answer 10

-Low pressure atrial receptors

-Under control of ECF

-Promotion of diuresis (brings down extracellular volume, loss of fluid in body)

Question 11

What must be kept the same in heart? (2)

Answer 11

-Input must equal output
-Cardiac Output left and right must be the same!