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Clin Phys 1 > Clin Phys Week 10 E > Flashcards

Clin Phys Week 10 E Flashcards

1
Q

What is the formula for blood pressure?

A

CO x TPR = Blood pressure

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2
Q

What are the main factors that influence blood pressure?

A

Cardiac output (CO)

Total peripheral resistance (TPR)

Blood volume

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3
Q

What does total peripheral resistance depend on? What does this mean in terms of vasodilation and vasoconstriction? Can TPR ever be truly calculated?

A

r to the power of 4 ( r = radius of vessels)

Vasodilation causes a drop in total peripheral resistance.

Vasoconstriction causes a rise in total peripheral resistance.

TPR cannot be completely calculated, we can estimate but never truly know the exact total peripheral resistance

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4
Q

What causes an increase in the diameter of blood vessels (vasodilation)?

A

Decreased O2

Increased CO2 and other metabolites

Increased nitric oxide

Decreased sympathetic stimulation

Histamine release

Heat

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5
Q

What causes a decrease in the diameter of blood vessels (vasoconstriction)?

A

Increased oxygen

Decreased carbon dioxide and other metabolites

Increased endothelin

Increased sympathetic nervous system, vasopressin, angiotensin II

Cold

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6
Q

What blood vessels are affected by the sympathetic nervous system?

A

Most blood vessels with the exception of capillaries

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7
Q

What is the vasomotor centre (what does it have control over, what can it be controlled by)? Where is it located?

A

It transmits impulses to all vessels of the body and is responsible for vascular tone (it keeps blood vessels in a partially contracted state to maintain normal blood pressure). It has control over the heart and peripheral vessels and can both control inhibition and excitation of these using higher brain function e.g. arousal, anger.It is located in the medulla, bilaterally in the reticular substance and the last 3rd of the pons

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8
Q

What are baroreceptors? Where are they located?

A

Located in the carotid sinus and aortic arch

They comprised of spray type nerve endings located in the artery wall and are stimulated when they are stretched. The signals are sent to the vasomotor centre via CN 9 and vagus nerve and reflects the level of arterial pressure.

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9
Q

What is BP maintained by?

A

Autonomic reflex negative feedback

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10
Q

What part of the maintenance of BP controlled by autonomic reflex negative feedback? What does it not have control over?

A

TPR and CO. It does not have any influence over blood volume.

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11
Q

What is orthostatic hypotension?

A

Failure of the autonomic reflex negative feedback causes a lack of blood supply to the head upon standing.

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12
Q

List in order the autonomic reflex negative feedback loop

A
  1. Baroreceptor
  2. Afferent (CN IX and CN X)
  3. Intergrating centre (vasomotor and cardiac centre in the medulla oblongata
  4. Efferent (SNS nerves)
  5. Effectors (arteries and vein walls)
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13
Q

The rapid control of blood pressure integrates which 3 autonomic reflexes?

A

Baroreflexes

Chemoreflexes

Medullary ischemic reflex

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14
Q

What is the result of sympathetic control on blood vessels?

A

Sympathetic control stimulates most vessels to constrict but causes dilates vessels in skeletal and cardiac muscle

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15
Q

Explain the baroreflex and the impacts of increased and decreased BP

A

Baroreceptors are stretch receptors that monitor pressure in aortic arch and in carotid arteries, they send constant signals to the brainstem via afferent CN IX and CN X

An increase in BP: causes a stretch in the arterial wall and causes the rate in signals from the baroreceptors to rise.A higher rate of signals inhibits the vasomotor centre, which decreases sympathetic tone and vasodilation causes BP to drop.

A decrease in BP: causes a decreased stretch in the arteries and causes a drop in the rate of signals sent from the baroreceptors. A lower rate of signals excites the vasomotor centre which increases sympathetic tone and causes vasoconstriction to increase BP.

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16
Q

What is caused by sympathetic stimulation and reciprocal inhibition of parasympathetic stimulation?

A

Almost all arterioles in the body constrict, increasing TPRVeins and other large vessels of circulation are strongly constricted (increasing circulating blood volume)

The heart is stimulated by sympathetic stimulation - increasing cardiac efficiency and increasing CO

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17
Q

Stimulation of the SNS can increase arterial pressure by how much and how quickly once it is activated?

A

Can increase BP by 2-3 times in 5-15 seconds

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18
Q

Inhibiting neural control of BP can reduce BP by how much and how quickly?

A

Can reduce it by 50% in 10-40 seconds

19
Q

What are the limitations of baroreceptors?

A

Stretch receptors: poorly control pressure below 50mmHg and above 170mmHg

20
Q

What happens to baroreceptors when:BP is under 50mmHgBP is over 170mmHg

A

BP under 50mmHg does not stimulate the receptor

BP over 170mmHg the receptor is overstretched

21
Q

Where are chemoreceptors found?

A

In the aortic body and carotid bodies (aortic arch, subclavian arteries, and external carotid arteries)

22
Q

What do chemoreceptors do? What are their primary and secondary roles?

A

Responds to changes in blood chemistry (e.g. pH, O2, CO2)

Primary role: adjusts respiration

Secondary role: vasomotor (hypoexmia, hypercapnia and acidosis stimulate chemoreceptors, instruct vasomotor centre to cause vasoconstriction, increased BP, increased lung perfusion and gas exchange

23
Q

What is the stimulus for the medullary ischemic reflex?

A

Inadequate perfusion of the brainstem.

Cardiac and vasomotor centres sends sympathetic signals to heart and blood vessels: Increases cardiac output and increases BP

24
Q

What is artrial control?

A

The atria and pulmonary artery have pressure receptors; a decrease in pressure causes as reflex increase in HR and BP.

  • Artrial stretch causes:A dilation of arterioles in the kidneys
  • Removal the fluid from the kidneys
  • Secretion of atrial natriuretic peptide
25
Q

What does atrial natriuretic peptide do?

A

Promotes excretion of Na and H2O from the kidneys

26
Q

What factors of flight or fight response are seen in skeletal muscle?

A

The body must increase arterial pressure to increase muscle blood flow. Skeletal muscle vessels dilate via local factors and sympathetic control. An increase in arterial pressure assists in maintaining TPR and supplying the muscles with enough blood.

27
Q

What is blood volume regulated by? What is it controlled and monitored by?

A

Hormones. Controlled and monitored by the hypothalamus and pituitary gland

28
Q

Where are receptors for blood volume found?

A

Hypothalamus and kidneys

29
Q

In EFC, what ion does water tend to follow?

A

Na (sodium)

30
Q

What should the osmolarity of EFC be to maintain homeostasis?

A

300mOsm

31
Q

Where is the osmolarity of the of the blood monitored?

A

The hypothalamus

32
Q

What is ADH, where is it secreted from and why?

A

Anti-diuretic hormone. It helps to retain water in the kidneys. It is secreted from the posterior pituitary gland in response to hyperosmolar EFC

33
Q

In which part of the kidneys is the Na concentration in the filtrate monitored?

A

The distant tubule (macula densa)

34
Q

Where is the kidneys is BP monitored?

A

The arterial cells (juxtaglomerular cells)

35
Q

Where is renin secreted from in the kidneys and in response to what?

A

A drop in BP causes the juxtaglomerular cells to secrete the enzyme renin

36
Q

Describe the renin angiotensin aldosterone system:

A

Blood pressure is detected in receptors in the hypothalamus and kidneys, and BP is controlled by hormones and enzyme secreted from the kidneys, liver, lungs, posterior pituitary and adrenal cortex. Renin is produced from the kidneys as a result of low BP. The renin binds with angiotensinogen for the liver to make angiotensin I. Angiotensin converting enzyme from the lungs changes the angiotensin I into angiotensin II.

Angiotensin II acts on:

  • The hypothalamus: to increase thirst and drinking
  • The adrenal cortex: release of aldosterone from adrenal cortex caused the reabsorption of sodium from filtrate in the kidneys
  • The CV system: vasoconstriction
  • The posterior pituitary: ADH release

Results in increase blood volume therefore increase BP

37
Q

Describe what happens when there is a sudden drop in blood pressure

A

Baroreceptors in the aortic arch and carotid sinus detect a decrease in blood pressure because their stretch receptors are not adequately stretch and this causes a slow in the rate of signals sent along CN 9 and CN 10 to the vasomotor centre of the medulla. The medulla creates a sympathetic nervous system reaction, causing peripheral vessels to constrict. This increases TPR. The sympathetic system also stimulates the heart, causing a rise in HR. An increase in HR and an increase in TPR is going to cause a rapid increase in blood pressure.

38
Q

Describe what happens when there is a sudden rise in blood pressure.

A

The baroreceptors in the aortic arch and carotid sinus detect a rise in blood pressure, their stretch receptors are stretched more than optimal range and this causes a rise in signals sent along CN 9 and CN 10 to the vasomotor centre located in the medulla. The medulla send signals along sympathetic nervous system vasodilator fibres to dilate the peripheral blood vessels, reducing TPR. Simultaneously the parasympathetic nervous system acts on the heart, causing a drop in heart rate, decreasing CO and ultimately, with the assistance on a reduced TPR, a drop in blood pressure.

39
Q

What is an intermediate/long term system for addressing an increase in blood pressure?

A

Renin production is reduced in the kidneys. When stretch receptors in the vessels are stretched by the increase in blood pressure, granules in the atria are stimulated to secrete ANP (atrial natriuretic peptide) which promotes excretion of water and salt by the kidneys.The stretch reflex also causes an inhibition in the secreting of ADH from the posterior pituitary gland. This decreases blood volume and therefore causes a drop in blood pressure.

40
Q

What is the normal response of SV, HR and CO to exercise?

A

Increase in all

41
Q

With vigorous exercise, what happens to the myocardium of the left ventricle? Is it reversible?

A

It increases in size and becomes more efficient (not hypertrophic)

It is reversible, unlike hypertrophic which is irreversible

42
Q

What is approximate resting cardiac output?

A

5.0L/min

43
Q

What is cardiovascular drift? What causes it?

A

A gradual decrease in stroke volume and systemic and pulmonary arterial pressures and an increase in heart rate.

Occurs with steady-state prolonged exercise or exercise in a hot environment

44
Q
A

Clin Phys 1 (11 decks)

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