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GOATED BRS > Control of heart function > Flashcards

Control of heart function Flashcards

1
Q

What are the 3 major tissues that control heart function?

A

CNS
Blood Vessels
Kidneys

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2
Q

Where is the SAN found?

A

Junction of crista terminalis; upper wall of right atrium & opening of superior vena cava

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3
Q

What molecule regulates the AVN?

A

Ca2+

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4
Q

Where is the AVN found?

A

Triangle of Koch at base of right atrium

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5
Q

What kind of cells are in the bundle of His and describe the pathway

A

Specialised myocytes.

AV node: His bundle > branches at intraventricular septum > apex

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6
Q

What are the purkinje fibres made of?

A

Specialised conducting fibres

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7
Q
A

3 phases: 0, 3, 4
Ca2+ influx
K+ efflux
Na+ influx

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8
Q

What kind of channels create the pre-potential present in the SAN?

A

‘Funny’ channels

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9
Q

How do action potentials vary across the heart?

A

Have different action potential shapes
-Due to different ion currents flowing and different ion channel expression in cell membrane

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10
Q

How and why are cardiac muscle APs different to nerve APs?

A

Compared to nerves, cardiac AP is long (200-300 ms vs. 2-3 ms)
-Duration of AP corresponds to duration of contraction
-Long contractions necessary for effective pumping

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11
Q

def Absolute refractory period

A

Time during which no AP can be initiated regardless of stimulus intensity

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12
Q

def Relative refractory period

A

Period after ARP where an AP can be elicited but only with larger stimulus strength

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13
Q

How many phases are in a cardiac muscle AP and what are they?

A

5

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14
Q

What causes the upstroke in a cardiac muscle AP?

A

Na+ influx

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15
Q

What is different about K+ efflux and Na+ influx in cardiac muscle cells and SA node cells?

A

SA node has K+ efflux only during AP, cardiac muscle AP has K+ efflux continuously, apart from the first influx of Ca2+

SA node has Na+ infux continuously, but cardiac muscle cell has Na+ influx only at the upstroke

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16
Q

How does the sympathetic and parasympathetic nervous system innervate the heart?

A

Sympathetic: Controls SAN, AVN and lower heart fibres

Parasympathetic(Vagus nerve): Controls SAN and AVN only

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17
Q

What is the effect of sympathetic innervation of the heart?

A

‘fight or flight’
↑ HR (chronotropy) – increases the slope of phase 4
↑ force of contraction (inotropy) – increases Ca2+ dynamics

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18
Q

What is the effect of parasympathetic innervation of the heart?

A

‘Rest & digest’
↓ heart rate (HR) – decreases the slope of phase 4

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19
Q

What are the neurotransmitters in pre and post ganglionic fibres in the SNS?

A

Pre-ganglionic fibres use ACh
Post ganglionic fibres use noradrenaline

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19
Q

What is the neurotransmitter in pre and post ganglionic fibres in the PNS?

A

ACh

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20
Q

Between the cardiac plexuses and spinal cord where do sympathetic fibres pass through first?

A

Sympathetic chain(Paravertebral ganglia)

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20
Q

What are the SNS and PNS useful for in heart control?

A

PNS: Heart rate
SNS: Circulation

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21
Q

When innervating the heart, where do the parasympathetic and sympathetic fibres arise from?

A

SNS: Thoracic + Lumbar vertebrae

PNS: Cervical + Sacral vertebrae

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22
Q

What is the function of the vasomotor centre and what comprises it?

A

Transmits impulses distally through spinal cord to almost all blood vessels

Composed of:
-Vasoconstrictor (pressor) area
-Vasodilator (depressor) area
-Cardio-regulatory inhibitory area

23
Q

Where is the vasomotor centre located?

A

VMC(Vasomotor centre) located bilaterally in reticular substance of medulla & lower third of pons

24
Q

What different functions do the lateral and medial portions of the vasomotor centre control?

A

Medial: Transmits signals via vagus nerve to heart that tend to decrease heart rate.

Lateral: Controls heart activity by influencing heart rate and contractility

25
Q

At the SAN, what kind of receptors do Ach(PNS) and NA(SNS) bind to?

A

G-protein coupled receptors which activate a protein cascade(ATP>cAMP>PKA)

26
Q

How is the vasomotor centre excitatorily/inhibitorily controlled?

A

Higher centers of the brain such as the hypothalamus can exert powerful excitatory or inhibitory effects on the VMC.

27
Q

By what 3 means is kidney function controlled?

A

Sympathetic innervation(No PNS)
Blood volume
Blood pressure

28
Q

How does decreased blood volume alter kidney function?

A

↑renin secretion > ↑angiotensin-II production: vasoconstriction & ↑blood pressure(via aldosterone)

29
Q

How does increased sympathetic innervation alter kidney function

A

α1-adrenoceptor > vasoconstriction > ↓ glomerular filtration > ↓Na+ excretion: increase in blood volume (aldosterone)

30
Q

What are changes in blood volume detected by?

A

Venous volume receptors

31
Q

How are changes in blood pressure detected?

A

Arterial baroreceptors

31
Q

Where do renal sympathetic fibres innervate on the kidney?

A

Afferent and efferent arterioles

32
Q

What is the site of storage, synthesis and release of renin?

A

Juxtaglomerular cells

33
Q

What do kidney B1-adrenoceptors control?

A

Renin secretion

34
Q

How do baroreceptors control blood pressure in the CP circuit?

A

(Decrease in filling)/Distension > Less/More baroreceptors firing > More/Less SNS activity

35
Q

Which nerves do volume+pressure sensors (also atria & right ventricle) send signals through?

A

Glossopharyngeal + Vagus

36
Q

In the arterial circuit, how do pressure sensors control heart rate?

A

Decrease/Increase in pressure > Less/More baroreceptors firing > More/Less SNS activity

37
Q

What factors are SNS activity based off of in the cardiopulmonary and arterial circuit?

A

CP: Volumes

Arterial: Pressures

38
Q

What are the 2 circulations in the body?

A

Two circulations: pulmonary and systemic
Right heart > lungs > left heart > body

39
Q

What does constriction in veins cause?

A

-Reduced compliance
-Increased venous return

40
Q

What is peripheral venous volume affected by?

A

Peripheral venous tone(SNS)
Gravity
Skeletal muscle pump
Breathing

41
Q

What does central venous pressure dictate?

A

Amount of blood flowing back to the heart, and thus preload and stroke volume

42
Q

What does constriction determine in arteries?

A

Blood flow to downstream organs
Mean arterial blood pressure
The pattern of blood flow to organs

43
Q

Top is atrial pressure

A
44
Q

What is the function of Nitric oxide (NO) and is it a local or systemic factor for blood flow regulation?

A

Local vasodilator

45
Q

What is the function of Prostacylin and is it a local or systemic factor for blood flow regulation?

A

Local vasodilator

46
Q

What is the function of Noradrenaline/Adrenaline and is it a local or systemic factor for blood flow regulation?

A

Systemic vasoconstriction

47
Q

What is the function of Atrial natriuretic peptide (ANP) and is it a local or systemic factor for blood flow regulation?

A

Systemic vasodilator

47
Q

What is the function of Vasopressin (ADH) and is it a local or systemic factor for blood flow regulation?

A

Systemic vasoconstriction

48
Q

What is the function of Angiotensin II and is it a local or systemic factor for blood flow regulation?

A

Systemic vasoconstrictor

49
Q

What is the function of Kinins and is it a local or systemic factor for blood flow regulation?

A

Systemic vasodilator

50
Q

What is the function of Endothelins (ET) and is it a local or systemic factor for blood flow regulation?

A

Local vasoconstrictors

51
Q

What is the function of Thromboxane A2 (TXA2) and is it a local or systemic factor for blood flow regulation?

A

Local vasoconstrictor

52
Q

What is the difference between systemic and local blood flow regulators?

A

Local: Intrinsic to the smooth muscle (or closely associated)
Important for reflex local blood flow regulation within an organ

Systemic: Extrinsic to the smooth muscle
These include the autonomic nervous system & circulating hormones

53
Q

What is the effect of SNS innervation on the afferent glomerular arterioles?

A

α1-adrenoceptor > vasoconstriction
↓ in glomerular filtration rate > ↓Na+ filtered > Increased blood volume

54
Q

What is the function of aldosterone

A

Increase Na+ reabsorption
Increase K+ excretion

55
Q

What is renins’ effect on aldosterone?

A

Renin increases aldosterone

GOATED BRS (57 decks)

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