week 6-L1 control of heart function

Question 1

what control the heart function?

Answer 1

CNS, blood vessel and kidneys

Question 2

how CNS control of the heart

Answer 2

parasympathetic and sympathetic controls by ANS

Question 3

CNS what does parasympathetic system do?

Answer 3

rest and digest therefore

decrease HR and slope of phase 4

Question 4

CNS what does sympathetic system do?

Answer 4

increase HR and slope of phase 4

increase force of contraction and calcium dynamics

Question 5

chronotropy

Answer 5

increase in heart rate

Question 6

inotropy

Answer 6

increase in contraction force of ventricles from increase calcium dynamics

Question 7

KIDNEY control of the heart

Answer 7

sympathetic innervation only- absence of parasympathetic innervation in the kidney

Question 8

KIDNEY sympathetic control on heart

Answer 8

decrease glomerular filtration- decrease Na excretion

cause increase in blood volume and BP

Question 9

KIDNEY blood volume regulation

Answer 9

detected by venous volume receptors

increase renin secretion- increasing angiotensin II production causing vasoconstriction- blood pressure increase

Question 10

KIDNEY how is blood pressure detected?

Answer 10

arterial baroreceptors

Question 11

BLOOD VESSEL cardiopulmonary circuit

Answer 11

volume sensors in atria and ventricles sending signals through the glossopharyngeal and vagus nerves

Question 12

BLOOD VESSEL decrease in filling

Answer 12

detected by reduction in baroreceptors firing to increase SNS activity

Question 13

BLOOD VESSEL distention

Answer 13

detected by increase in baroreceptors firing to increase the PNS activity and reduce SNS activity

Question 14

features of PNS

Answer 14

pre and post ganglionic fibres release Ach as neurotransmitter and control heart rate

Question 15

features on SNS

Answer 15

pre ganglionic fibres release Ach but post ganglionic fibres release noradrenaline
SNS important in controlling circulation

Question 16

describe the mechanism SNS

Answer 16

beta-1 receptors activation cause Gs stimulation
AC activated converting ATP to cAMP to PKA
increase the HR and BP

Question 17

describe the mechanism of PNS

Answer 17

M2 receptors cause the Gi stimulation that inhibits the conversion of ATP to PKA
reduction in HR and BP

Question 18

what happens if SNS cut off

Answer 18

HR falls below normal

Question 19

what happens if PNS cuts off

Answer 19

HR rise above normal

Question 20

what does cut off CNS or PNS show

Answer 20

that both systems work together to maintain normal HR

Question 21

renal system sympathetic fibre innervation

Answer 21

afferent and efferent arterioles

Question 22

renal afferent arterioles effect of SNS

Answer 22

primary site of SNS activity
alpha 1 adrenoceptor causes vasoconstriction
decrease in glomerular filtration rate causes decrease in Na filtered
Juxtaglomerular cells site of renin synthesis, storage and release- beta 1 adrenoceptor stimulation cause renin secretion

Question 23

designs of circulatory circulation and why

Answer 23

more blood % in vein and venues and less in arteries

increase preload and decrease after-load

Question 24

constriction of veins and arteries

Answer 24

veins- causes reduction in compliance (ability to stretch0 and venous return decreasing preload
arteries- causes increase in after load as blood pressure increases

Question 25

how to regulate blood flow

Answer 25

local and systemic mechanism

Question 26

local mechanism of blood flow regulation

Answer 26

intrinsic smooth muscles or endothelial-derived mediators vasodilators- nitric oxide on smooth muscles and prostacyclin anti platelet and anticoagulant effect vasoconstrictors-thromboxane A2 heavily synthesised in platelets and endothelins from endothelial nucleus

Question 27

systemic mechanism of blood flow regulation

Answer 27

extrinsic to smooth muscles and non derived endothelial mediators vasodilators- kinins bind to receptor on endothelial cells and stimulate no synthesis and atrial natriuretic peptide response to stretch to reduce BP vasoconstrictors- vasopressin binds to V1 receptors on smooth muscles, noradrenaline and angiotensin II stimulate ADH secretion

Question 28

what increases atrial pressure?

Answer 28

blood volume, respiratory movements, SNS activation of veins and skeletal muscle pumps- increase venous pressure that in turn increase venous return

Question 29

cardiac action potential features

Answer 29

longer action potential for longer slower contraction for more efficient pumping 5 phases ranging 0-4

Question 30

Name the 5 phases of cardiac action potential

Answer 30

``` 0- upstroke 1- early repolarisation 2- plateau 3- repolarisation 4- resting membrane potential ```

Question 31

absolute refractory period

Answer 31

time lag during which no AP can be initiated independent of the stimulus intensity- phase 1 and 2

Question 32

relative refractory period

Answer 32

period where an AP can be initiated follow ARP but required high stimulus intensity

Question 33

what defines resting membrane potential

Answer 33

K+ influx

Question 34

what defines upstroke

Answer 34

large increase in membrane to Na+

Question 35

what defines contraction

Answer 35

Calcium influx which release calcium form intracellular store- L-type VGCC during plates phase

Question 36

what defines the 100-200ms cardiac AP

Answer 36

gradual activation of K+ currents outwards balancing and overcoming calcium flow NB large Ik inactive during plateau but increase once cells partially repolarised Ik responsible for full repolarisation

Question 37

what is the role of Ik

Answer 37

large and flows during diastole to stabilise the resting membrane potential

Question 38

features of pacemaker (SAN) AP

Answer 38

presence of only phases 0,3,4 | resting membrane potential become prepotential- can initiate another AP due to L-type VGCC and funny current

Question 39

SNS effect on cardiac AP graph

Answer 39

chronotropy- cAMP activates If causing increase slope of phase 4 SAN inotropy- increase calcium dynamics in myocytes

Question 40

B1 receptor activation in renal afferent arterioles will have which initial effect?

Answer 40

secretion of renin

Question 41

which receptor transmits signal from pre to post ganglionic nerves in the SNS?

Answer 41

nicotinic Ach receptor

Question 42

when is the afferent nerve activity in the baroreceptor at its highest

Answer 42

high systolic blood pressure and pulse pressure

Question 43

what effect will activation of renal alpha 1 receptor eventually have on the heart?

Answer 43

increased chronotropy and inotropy