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Quiz 2 > Q2-CB11/Cardiac Output 1 > Flashcards

Q2-CB11/Cardiac Output 1 Flashcards

1
Q

What is cardiac output?

A

the volume of blood ejected from a ventricle per minute (L/min)

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2
Q

equation of cardiac output

A

cardiac output = heart rate x number of beats per minute

CO = HR x number of bpm

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3
Q

What is a cardiac output of a textbook person?

A

5 L/min

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4
Q

What is cardiac output controlled by?

A

either heart rate and stroke volume

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5
Q

what controls cardiac output?

A

it is regulated by the automatic nervous system

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6
Q

What does the ANS do?

A

it controls multiple systems that maintains normal homeostasis

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7
Q

is the ANS subconscious or involuntary?

A

it is involuntary

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8
Q

The only rigorous definition for these is from the anatomy and where on the spine the fibres emerge. What are these places?

A

SNS: thoraco-lumbar (segments T1 to L2 )

PNS: cranio-sacral (cranial nerves III, VII, IX & X, sacral segments 2,3,4)

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9
Q

The Sympathetic NS primarily acts via __________

A

catecholamines

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10
Q

what are catacholamines?

A

Catecholamines are a group of similar substances released into the blood in response to physical or emotional stress.

The primary catecholamines are dopamine, epinephrine (adrenaline), and norepinephrine.

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11
Q

What is released from nerve endings in the Sympathetic NS?

A

noradrenaline

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12
Q

Sympathetic NS action in the heart is mediated via ______ and _______

A

alpha and beta adrenoceptors

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13
Q

What is the most important adrenoceptor for the heart?

A

beta1-adrenoceptor

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14
Q

Where are beta1-adrenoceptors located?

A

all throughout the heart (SA node, AV node, atria, and ventricles)

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15
Q

What is a beta-adrenoceptor?

A

a G-protein coupled receptor linked to an adenylate cyclase

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16
Q

what does a beta-adrenoceptor do?

A

it increases cAMP which then turns on protein kinase A

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17
Q

Where does the main depolarizing curent in the SA node come from?

A

it comes from the Na+/K+ channel, current through this channel is increased by the binding of cAMP

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18
Q

What causes the increase of Ca2+ into myocytes?

A

cAMP/PKA, when Ca2+ levels increase, so does the force of contraction

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19
Q

What ion is crucial for muscle contraction?

A

calcium

20
Q

how is calcium crucial to muscle contraction in the heart?

A

it binds to troponin on the thin filament, allowing the thick filament to interact.

21
Q

explain the SA node action potential.

A
22
Q

What can be said about sympathetic agonists?

A

they are both positive chronotropes and positive inotropes

positive chronotropes increase the rate and positive inotropes increase the force

23
Q

What are some types of beta-blockers?

A

atenolol and propranolol

24
Q

What can be said about beta-blockers?

A

they are negative chronotropes and negative inotropes

negative chronotopes decrease the rate

negative inotropes decrease the force

25
Q

What is the primary neurotransmitter in the parasympathetic NS?

A

acetylcholine (ACh)

26
Q

At what receptors does ACh work at?

A

muscarinic and nicotinic cholinergic receptors

27
Q

What are muscarinic cholinergic receptors?

A

they are G-protein coupled receptors

28
Q

What are nicotinic cholinergic receptors?

A

they are ion channels found in nerves and skeletal muscle

29
Q

Parasympathetic innervation of the heart is via the ____________

A

vagus nerve (cranial nerve X)

30
Q

What is the main cholinergic receptor in the heart?

A

M2 (muscarinic type 2)

31
Q

what does the vagus nerve innervate specifically?

A

the SA node, AV node, and parts of the atria (there is little to none innervation in the ventricles)

32
Q

What does the M2 receptor do?

A

it inhibits adenylate cyclase, which decreases the amt of the cAMP

33
Q

What happens to sodium influx when the amt of cAMP decreases?

A

Na+ influx is decreased so the rate of depolarization is decreased.

since it decreases the rate of SA node firing, heart rate decreases as well

34
Q

what effect does the decrease in cAMP have on atrial and ventricular contraction?

A

it has a small effect on the force of atrial contraction but no effect on the ventricles

(the atrial effect has little if any effect on cardiac output)

35
Q

explain SA node action potential in cholinergic action.

A
36
Q

what 2 divisions of the nervous system innervate the SA node?

A

sympathetic and parasympathetic

37
Q

What is controlled by the balance of the sympathetic and parasympathetic nervous systems?

A

heart rate

38
Q

what is a sign of sympathetic activation?

A

tachycardia

(atropine, the muscurinic antagonist, can cause tachycardia)

39
Q

the natural rate of the SA node is abt 100bpm, but ______ stimulation drops it down to abt 70 bpm

A

vagal

40
Q

what is equation for mean arterial pressure?

A

mean arterial pressure = cardiac output x total peripheral resistance

41
Q

Explain the baroreceptor reflex.

A

it is a negative feedback loop

sensory fibers in the aortic arch and carotid sinus detect a stretch in blood vessel walls(the firing is directly proportional to the stretch)

these fibers then go to the medulla oblongata on the brain stem

the medulla regulates the sympathetic/parasympathetic NS outflow to the heart

42
Q

Explain cardiac changes in exercise.

A

exercise is related to an increase of sympathetic NS activity. Normal feedback via the baroreceptor would be expected to prevent this, BUT instead this looks to be reset in exercise; the effect is the BP is perceived to be too low!

43
Q

What 2 changes does exercise cause in the heart?

A

Increases heart rate and stroke volume

– heart rate can increase approx. 300% to ~200 bpm

– stroke volume can increase approx. 175% to ~125 ml

– overall cardiac output can increase by approx. 500% to 25 L

44
Q

heart rate cannot increase over ______ bpm

A

200

45
Q

why cant heart rate increase over 200 bpm?

A

due to the length in action potential and high rates also decrease perfusion as this occurs in diastole

46
Q

explain cardiac changes in athletes.

A

Athletes have low rates but large stroke volumes

– <60 bpm (bradycardia)

Quiz 2 (18 decks)

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