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Physiology S2 > T2: Heart Innervation > Flashcards

T2: Heart Innervation Flashcards

1
Q

What is an animals resting heart rate dependent on?

A
  • body size
  • metabolic rate
  • autonomic balance
  • species characteristics
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2
Q

Why does data on heart rates differ?

A

due to the differing environmental conditions

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3
Q

Where does the innervation of the heart primarily arise from?

A

AUTONOMIC NERVOUS SYSTEM:
- sympathetic nerves
- parasympathetic nerves (vagus nerve)

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4
Q

What does the autonomic nervous system innervate? Why?

A
  • atria and ventricles
  • to modulate their function and coordination
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5
Q

What sympathetic nerves positively impact heart actions?

A
  • chronotropic (rate of contraction)
  • inotropic (force of contraction)
  • bathmotropic (increase in excitability)
  • dromotropic (rate of conductivity)
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6
Q

What do chronotropic nerves impact?

A

rate of contractions

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7
Q

What do inotropic nerves impact?

A

force of contraction

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8
Q

What do bathmotropic nerves impact?

A

increase in excitability

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9
Q

What do dromotropic nerves impact?

A

rate of conductivity

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10
Q

What is the function of sympathetic stimulation?

A
  • increases the SA node discharge
  • increases AV conduction
  • increases atrial and ventricular contractility
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11
Q

What does sympathetic stimulation do to: contractility, frequency, conduction velocity and irritability?

A

increases!!

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12
Q

What cellular mechanisms exist for sympathetic (SNS) nervous system actions?

A
  • catecholamine norepinephrine
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13
Q

Explain the functioning of norepinephrine.

A
  • catecholamine norepinephrin released
  • norepinephrin binds to adrenergic receptors (alpha/beta(main))
  • adenylyl cyclase is activated
  • enhancement of SA node ion channels rhythmicity
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14
Q

What are the major types of adrenergetic receptors in cardiac tissue?

A
  • alpha
    alpha 1
    alpha 2
  • beta (predominates):
    beta 1
    beta 2
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15
Q

What is the function of beta 1 adrenergic receptors?

A
  • inotropic responses
  • chronotropic responses
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16
Q

What is the function of beta 2 adrenergic receptors?

A

mediate:
- glycogenolysis
- vasodilation

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17
Q

What is the function of alpha 1 adrenergic receptors?

A

minor role (small density)

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18
Q

What is the function of alpha 2 adrenergic receptors?

A
  • inotropic responses
19
Q

What ions, specifically, depolarize and hyperpolarize the SA node?

A

depolarization: Ca2+
hyperpolarization: K+

20
Q

Explain the parasympathetic NS control of the heart.

A

right and left vagus nerves differentially innervate the SA node!

21
Q

What happens when the right vagus nerve is stimulated?

A
  • decreases firing rate of the SA node
  • decreases heart rate!
  • negative inotropic effects excerted in the atria
22
Q

What happens when the left vagus nerve is stimulated?

A
  • inhibits AV conduction
  • produces AV block

negative chronotropic, negative inotropic and negative dromotropic action

23
Q

What does vagal stimulation cause?

A
  • slows discharge rate of the SA node
  • slows/blocks AV conduction
  • decreases atrial contractability
  • decreases ventricular contractability
24
Q

What do vagus nerves do at rest?

A

exert a continuous/tonic restraint on the heart

25
Q

What happens to the heart rate when the vagus nerves are cut or cooled?

A

heart rate becomes greatly accelerated

26
Q

What alters vagal activity?

A

physiological and pathological conditions

27
Q

What nervous system controls the heart?

A

autonomic nervous system

28
Q

Do the sympathetic and parasympathetic nervous systens oppose each other or work together?

A

OPPOSE EACH OTHER!

29
Q

What is the overall action of the sympathetic vs parasympathetic activation?

A

sympathetic- increases heart rate
parasympathetic- decreases heart rate

30
Q

What happens when you apply pressure on the eyeball? (oculocardiac reflex)

A

slows the heart rate

31
Q

What happens when you inhale irritating vapours (eg. anasthetics)?

A

reflex inhibition of the heart
- extrasystole
- bradycardia

32
Q

What is the function of baroreceptors?

A

detect changes in blood pressure at:
- the aortic arch
- the carotid sinus

33
Q

What is the relation of pulse with arterial blood pressure?

A

INVERSELY PROPORTIONAL!
- a rise in pressure causes a decrease of heart rate
- a fall in pressure causes an increase in heart rate

34
Q

What happens to heart rate when pressure is increased in the carotid sinus/aortic arch?

A

heart rate is reduced with an increase in pressure!

35
Q

What is the reflex called which explains the inverse relationship of heart rate with arterial blood pressure?

A

baroreflex

36
Q

Explain the movement of ions in the sodium potassium pump.

A
  • 3 Na+ out
  • 2 K+ in
37
Q

What type of feedback response does the baroreflex have?

A

negative feedback response

38
Q

Where are chemoreceptors located?

A

next to baroreceptors in:
- carotid bodies
- aortic bodies

39
Q

When do chemoreceptors send signals to the cardiovascular center?

A
  • low O2 hypoxia
  • high CO2 hypercapnia
  • high H+ acidosis
40
Q

What is the “chemoreflex”?

A

heart rate altering by arterial blood gases

41
Q

What does the chemoreflex activation do to respiratory rate and depth?

A
  • elevate respiratory rate
  • elevate respiratory depth
42
Q

State examples of hormones affecting the heart.

A
  • epinephrine
  • norepinephrin
  • glucagon
  • mineralocorticoids
  • ACTH
  • vasopressin
  • angiotensin I
  • angiotensin II
  • thyroxine
43
Q

What type of effect (direct or indirect) does oxygen, carbon dioxide and pH have on the cardiorespiratory system? How?

A
  • both! (direct and indirect)
  • via actions on the carotid body and central chemoreceptors
44
Q

How does hypoxia and hypercapnia affect cardiac contractibility?

A

depresses cardiac contractability

hypoxia- too little oxygen
hypercapnia- too much carbon dioxide

Physiology S2 (17 decks)

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