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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
what is the nervous control of the blood vessel diameter?
- 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
Summary of the control of blood vessel radius.
insert
27
show a graph of the sympathetic and parasympathetic nerve activity?
insert graph
28
how can we get an increase in heart rate?
- Increased SNS activity. - Increased plasma levels of adrenaline. - Decreased PNS activity
29
how can we control the force of contraction?
contractility is controlled by starlings law - SNS controls contractility - PSM has no action on the contractility of the heart
30
what is the process of controlling the force of contraction?
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
how to control stroke volume extrinsically?
- increased sympathetic activity to the heart | - increased plasma adrenaline
32
how to control stroke volume intrinsically?
- a greater EDV
33
what are baroreceptors
they are needed for maintenance of blood pressure
34
where are the baroreceptors located?
carotid sinus | aortic arch
35
at what range do carotid sinus receptors respond to pressures? where are they MOST sensitive?
60 and 180 mmHg 90 -100 mmHg
36
what is reciprocal innervation?
- 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
overall what are the results of reciprocal innervation?
- 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
what does an increased blood pressure result in?
- this means a huge increase in firing from the baroreceptors - more pressure means more firing
39
what does BR activity trigger?
- more traffic in vagus nerve from the VMC
40
what directly reflects the BR activity?
- the PNS activity
41
what does an increase in PSN activity mean?
Increase in PNS activity → more ACh production in SinoAtrialNode → decreases gradient of pacemaker potential → decrease in heart rate
42
what does less SNS activity result in?
decrease in contractility and | increase in vessel radius (vasodilation).
43
what does a change in HR contractility and dilation mean?
decrease in blood pressure
44
what happens in great blood loss?
= 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
show a diagram of how arterial pressure is maintained:
INSERT

LSS: cardiovascular system (17 decks)

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