circulation 3

Question 1

besides myogenic heartBEAT set by pacemakers, what do we need for heart ACTIVITY regulation

Answer 1

1. regulating heart RATE- 2 mechanisms

2. carpiac output (Q)=heart rate X stroke volume

Question 2

heart RATE

Answer 2

=intrinsic pacemaker rate+influence of extrinsic controls

-slope of pacemaker potential sets intrinsic heart rate

Question 3

vagal nerve control

Answer 3

-SLOWS heartbeat, negative chronotropy, bradycardia
-cardiac vagal nerve terminals near pacemaker release acetylcholine
ACh HYPERPOLARIZES pacemaker by opening K channels to prolong pacemaker potential
(occurs when holding breathe, face immersion, elevated blood pressure, and when afraid)

Question 4

beta-adrenergic control

Answer 4

increase heart rate, aka positive chronotropy or tachycardia
-CATECHOLAMINES stim beta-adrenoceptors to release adrenaline/epinephrine and noradrenaline/norepinephrine, which SHORTEN PACEMAKER POTENTIAL
(occurs with exercise, stress, emotions, and hypoxia)

Question 5

sotalol

Answer 5

beta-adrenoceptor blocker, given to people with heart attacks to prolong pacemaker potential and make it easier to re-regulate

Question 6

heart rate is ultimately controlled by the…

Answer 6

autonomic nervous system, specifically in the medulla

Question 7

sympathetic controls

Answer 7

• norepinephrine, and epinephrie (latter via adrenal medulla), which increase sodium and calcium influx, increasing rate of DEPOLARIZATION, which increase heartrate
• sympathetic heart rate controlled by medulla

Question 8

parasympathetic controls

Answer 8

• also by medulla
• parasymp neurons release ACh to increase K+ efflux, and decrease Ca influx to HYPERPOLARIZE cells, increasing time for depolarization and decreasing heart rate

Question 9

cardiac control evolution

Answer 9

• tunicates= tubular heart, it and all after have pacemaker cells (myogenics), and all after develop chambered hearts
• only elasmobranchs and vertebrates develop vagus nerve/parasympathetic for ACh and hyperpolarization from K efflux to decrease heart rate

Question 10

adrenaline stores and sympathetic innervation evolution

Answer 10

• adren stores in fish, sharks, and hagfish/lamprey

- adrenal GLAND and cardiac SYMPATHETIC INNERVATION in amph, rept, birds, mammals

Question 11

temperature directly alters intrinsic pacemaker rate

Answer 11

heart rate increases twice as fast as temperature

Question 12

heart rate and body mass

Answer 12

pacemaker rate scales INVERSELY with body mass in endotherms
Mo2=Q(tissue o2 extraction)
mo2=HRSV*(tissue o2 extraction)

Question 13

Fick Equation

Answer 13

cardiac output Q=heartrate (HR)*stroke volume (SV)
-Q= vol blood leaving heart per unit time
SV=volume of blood ejected per beat
HR=heartbeats per minute

Question 14

2 main mechanisms controlling heart rate

Answer 14

-intrinsic pacemaker rate and extrinsic influences

Question 15

2 main extrinsic regulators

Answer 15

vagal nerve control to decrease pacemaker rate, and beta-adrenergic control to increase pacemaker rate