13. cardiac output ii

Question 1

what is contractility

Answer 1

the contractile ability of cardiac muscle at a given preload

Question 2

positive inotropic

Answer 2

increases the contractility of the heart

Question 3

are the sympathetic nervous system and adrenaline positively inotropic or negatively inotropic

Answer 3

positive inotropic
increases force of contraction and therefore storke volume
increases velocity of conduction of cardiac impulse

Question 4

is the parasympathetic nervous system (acetylcholine) positively or negatively inotropic

Answer 4

negatively inotropic

decreases the contractility of the atria

Question 5

when the heart rate is 150bpm with SNS tone the diastolic phase is longer than the systolic phase why

Answer 5

gives more time for the ventricles to fill, and then eject blood in the diastolic phase

Question 6

what is afterload

Answer 6

the pressures that oppose the ejection of blood as it leaves the ventricles
how easily blood leaves the heart into arteries

Question 7

what is afterload influenced by

Answer 7

blood vessel tone ie vasodilation/vasorelaxation

Question 8

what is the capillary hydrostatic pressure

Answer 8

a minimum pressure needed to exchange fluids and substances across capillary networks- capillary exchange

Question 9

what is hypotension and hypertension

Answer 9

hypotension blood pressure s too low

hypertension is when blood pressure is too high

Question 10

what is blood pressure

Answer 10

the force placed on the walls of blood vessels by blood as it flows

Question 11

what is blood pressure determined by

Answer 11

cardiac output x total peripheral resistance (arteriole radius)

Question 12

autoregulation of blood pressure has both sort and long term regukatory mechanisms

Answer 12

short term mechanisms control heart rate, vasoconstriction, vasodilation
long term controls heart rate vasoconstriction vasodilation AND extracellular fluid volume regulation

Question 13

what happens to blood flow to tissues in active tissues

Answer 13

tissue metabolism
increase in metabolites
arterioles dilate brings more blood flow to tissue

Question 14

what are short term controls regulted by

Answer 14

baroreceptor and chemoreceptor

Question 15

what are long term controls of blood pressure controlled by

Answer 15

hormones

Question 16

how does the baroreceptor responf to an increase in blood pressure

Answer 16

baroreceptor is activated inhibits the cardioacceleratory centre and stimulates the cardioinhibitory centre, this will decrease the cardiac output and the heart rate ( release of acetylcholine by the PNS)baroreceptors also inhibit the vasomotor centres to cause vasodilation which will decrease the total peripheral resistance
this will decrease blood pressure

Question 17

how does a baroreceptor respond to a low blood pressure

Answer 17

baroreceptor is inhibited
the cardioacceleratory centre is not inhibited so can increase the cardiac output and heart rate
the vasomotor centre is also not inhibited so vasoconstriction and increased total peripheral resistance (helps move blood)

Question 18

role of peripheral chemoreceptors in the control of blood pressure

Answer 18

located in carotid body

detect changes on co2 pH and O2

Question 19

if there was an increase in CO2 and a decrease in pH how would the peripheral chemoreceptor respond

Answer 19

would stimulate the cardioacceleratory and vasomotor centres and inhibit the cardioinhibitory centre
increases heart rate and cardiac output, and vasoconstriction

Question 20

rule breaker how would a peripheral chemoreceptor respond to an increase in CO2 (and decrease in O2) in the pulmonary circulation

Answer 20

causes constriction the arterioles

Question 21

what is the role of the brain/ central chemoreceptors in the control of blood to the brain

Answer 21

located in the medulla oblongata and is involved in respiratory function
detects an increase in CO2 / a decrease in pH
vasodilation of cerebral vessels
promotes blood flow to the brain