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LSS: cardiovascular system > lecture 6: cardiovascular control 2 > Flashcards

lecture 6: cardiovascular control 2 Flashcards

1
Q

what is the equation for stroke

A

end diastolic volume - end systolic volume

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2
Q

what is the equation for cardiac output?

A

heart rate x stroke volume

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3
Q

what is the equation for Mean Systemic Arterial Pressure

A

Cardiac Output (CO) x Total Peripheral Resistance (TPR)

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4
Q

what are the two types of circulation?

A

pulmonary and systemic

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5
Q

what do veins have

A

capacitance and they act as reservoirs

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6
Q

what is volume distribution determined by?

A
  • venous tone,
  • gravity,
  • skeletal muscle pump
  • respiratory muscle pump.
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7
Q

what determines venous return?

A

central venous pressure determines venous return which determines stroke volume

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8
Q

what mechanisms determine blood flow?

A

intrinsic and extrinsic

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9
Q

what is the intrinsic mechanism for?

A
  • intrinsic to the smooth muscle

- important for local blood flow to an organ

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10
Q

what is extrinsic mechanism for?

A
  • consists of systemic regulation of hormones

- autonomic nervous system

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11
Q

what is auto regulation? as part of the intrinsic mechanism

A

the intrinsic capacity to compensate changes

in perfusion pressure by changing vascular resistance.

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12
Q

what does the myogenic theory state?

A

smooth muscle responds directly to tension changes in the vessel wall

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13
Q

what does the metabolic theory state?

A

as blood flow decreases metabolites accumulate and vessels dilate in response

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14
Q

what does the injury theory state?

A

this happens if a vessel is injured
Serotonin release from platelets causes
vasoconstriction.

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15
Q

what do the extrinsic mechanisms consist of?

A
  • the systemic regulation of hormones
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16
Q

what hormones are involved as part of the extrinsic mechanism?

A
  1. kinins eg. bradykinin
  2. ANP - vasodilator
  3. circulating vasoconstrictors
    ADH
    NE from adrenal medulla
    angio tension ii from renin secretion
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17
Q

what substances are released from the endothelium?

as part of the intrinsic mechanism?

A
  1. nitric oxide

2.Prostacyclin & Thromboxane A2 – vasodilator and
constrictor respectively

  1. endothelins
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18
Q

what is the sympathetic nervous system needed for?

A

controlling circulation

fight or flight

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19
Q

what is the para-sympathetic nervous system needed for?

A

regulating heart rate

rest and digest

20
Q

what is sympathetic innervation to blood vessels?

A
  • SNS nerve fibres supply all vessels with nerves apart from capillaries pre capillary sphincters and some metarterioles
21
Q

what tissues do more fibres innervate nerves to?

A

kidney
gut
spleen
skin

22
Q

what tissues do less fibres innervate nerves to?

A

skeletal muscles

the brain

23
Q

what is the vasomotor system composed of?

where is it located?

A
  • a pressor
  • a depressor
  • a cardioregulatory inhibitor arrea

it is in the pons and the medulla

24
Q

what do the lateral portions of the VMS control?

what do medial portions of the VMS control?

A

heart rate

signals via vagnus nerves ot decrease heart rate

25
Q

what is the nervous control of the blood vessel diameter?

A
  • vessels always receive sympathetic post-ganglionic nerve
    innervation to maintain vascular tone.

This means nerve activity can dilate OR constrict vessels

there is no PSN innervation to the vascular system

26
Q

Summary of the control of blood vessel radius.

A

insert

27
Q

show a graph of the sympathetic and parasympathetic nerve activity?

A

insert graph

28
Q

how can we get an increase in heart rate?

A
  • Increased SNS activity.
  • Increased plasma levels of adrenaline.
  • Decreased PNS activity
29
Q

how can we control the force of contraction?

A

contractility is controlled by starlings law

  • SNS controls contractility
  • PSM has no action on the contractility of the heart
30
Q

what is the process of controlling the force of contraction?

A
  1. NE binds to adrenoceptors to increase cAMP.
  2. cAMP activates PKA to phosphorylate LTCC, SR Calcium release
    channels and SERCA.
  3. More Ca2+ influx and more Ca2+ reuptake.
  4. Heart rate and contractility altered.
31
Q

how to control stroke volume extrinsically?

A
  • increased sympathetic activity to the heart

- increased plasma adrenaline

32
Q

how to control stroke volume intrinsically?

A
  • a greater EDV
33
Q

what are baroreceptors

A

they are needed for maintenance of blood pressure

34
Q

where are the baroreceptors located?

A

carotid sinus

aortic arch

35
Q

at what range do carotid sinus receptors respond to pressures?

where are they MOST sensitive?

A

60 and 180 mmHg

90 -100 mmHg

36
Q

what is reciprocal innervation?

A
  • when the baroreceptors sense increase in pressure they fire more
  • this means more PNS stimulation
  • there is also an inhibitory neurone which stimulates the SNS arm to decrease SNS activity
37
Q

overall what are the results of reciprocal innervation?

A
  • PNS stimulation of the heart via vagus nerve = decreased HR
  • decreased SNS stimulation means lower HR and stroke volume
  • decreased SNS to the blood vessels also causes dilation
38
Q

what does an increased blood pressure result in?

A
  • this means a huge increase in firing from the baroreceptors
  • more pressure means more firing
39
Q

what does BR activity trigger?

A
  • more traffic in vagus nerve from the VMC
40
Q

what directly reflects the BR activity?

A
  • the PNS activity
41
Q

what does an increase in PSN activity mean?

A

Increase in PNS activity → more ACh production in
SinoAtrialNode → decreases gradient of pacemaker potential →
decrease in heart rate

42
Q

what does less SNS activity result in?

A

decrease in contractility and

increase in vessel radius (vasodilation).

43
Q

what does a change in HR contractility and dilation mean?

A

decrease in blood pressure

44
Q

what happens in great blood loss?

A

= less arterial pressure
= less baroreceptors firing
= reflexes
= decrease in para sympathetic discharge to the heart
= increase in sympathetic to the heart
= increased contractility and heart rate and cardiac output

45
Q

show a diagram of how arterial pressure is maintained:

A

INSERT

LSS: cardiovascular system (17 decks)

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