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Y1 CAR > physiological regulation of BP > Flashcards

physiological regulation of BP Flashcards

1
Q

what is blood pressure

A

the hydrostatic pressure exerted by the blood against the walls of the blood vessels
- arterial BP = arterial pressure = high
- venous BP =presure in the veins = lower

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2
Q

what is systolic pressure

A

the highest pressure reached during the ejection phase

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3
Q

what is diastolic pressure

A

the lowest pressure reached during ventricular filling stage. (the bottom number on a BP reading

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4
Q

what is mean arterial pressure (MAP)

A

mean arterial pressure drives tissue perfusion with blood
MAP=(2xdiastolic)+systolic
/ 3
diastoli is twice as long as systoli
MAP of ~60 mm Hg is necessary to perfuse coronary arteries, brain and kidneys (minimum, otherwise tissues cant get nutrients)

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5
Q

what is arterial pressure derived from

A

arterial pressure results from the discharge of blood from the heart to the arterial system. this cannot all escape to the venous system before the next beat occurs, hence pressure is created

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6
Q

describe the pressure waveform

A

systolic ejection of blood creates a pressure waveform 1
- blood moving from left ventricle to aorta
- asymmetrical, arterial pulse wave in aorta
- transmitted to the rest of the arterial tree
- due to flexible walls that absorb pressure energy (reduces amplitude) but then return energy to maintain pressure
- dependent on elasticity of the artery walls (allows recoil of vessel walls which is essential for development of siastolic pressure
- recoil makes second peak to maintain pressure

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7
Q

describe how MAP changes around the body

A

dependent upon where in the body it is measured as this will influence the size and shape of arterial pulse 1 and 2
- close to heart: sharp peaks and troughs
- in limbs: pressure waveform more noticeable
- directly related to stroke volume
- inversely related to the compliance (elasticity) ot the arterial vessels
- pressure reduces as progresses to arterioles and capillaries
- increased HR increases MAP (increased HR = increased CO)

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8
Q

describe the normal systolic, diastolic and MAP in domestic animals

A

systolic: 125-145
diastolic: 80-95
MAP:

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9
Q

What is the normal systolic, diastolic and MAP ranges for rats/mice/guinea pigs

A

systolic: 100-120
diastolic: 70-80
MAP:

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10
Q

what are the normal ranges of systolic, disatolic and MAP in birds?

A

Systolic: 175-250
distolic: 150-170
MAP:

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11
Q

what are the normal ranges of systolic, disatolic and MAP in giraffes

A

systolic: 280-350
diastolic: 200-300
MAP:
has to be high in order to pump blood up to brain

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12
Q

how do you measure arterial blood pressure

A
  • sphygmomanometer (non invasive or indirect) in dogs, cats, pigs or horses
  • invasive methods (direct) with fluid in catheter
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13
Q

what factors can affect the measurement of BP

A
  • movement
  • stress
  • position
  • cuff size
  • temperature
  • full bladder
  • posture
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14
Q

is a high pulse pressure the same as a high MAP

A

NO
pulse pressure is simple systolic-diastolic. high pulse pressure does not indicate good tissue perfusion

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15
Q

what organs autoregulate their ABP

A
  • brain
  • kidney
  • heart

have an ability to maintain their local pressure despite arterial pressure changes (up to a certain extent)

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16
Q

what affects MAP

A

cardiac output
- =stroke volume x HR
- starling effect: increased strethcing of heart muscles leads to increased contraction
- increased CO=increased BP
- sympathetic stimulation = increases HR and force of contraction increasing BP
- PSNS activation = decreases HR and slightly decreases force of contraction decreasing BP
total peripheral resistance
- particularly in arterioles
- sympathetic stimulation increases constriction (alpha 1 predominates)
- outflow to veins is temporarily reduced thus increases MAP
- diameter of the arterioles in abdominal region are more effective
blood volume and composition
- loos of blood leads to reduced BP
- suffiecient amount required to overifill the arterial system (so not really relevent)
- increased viscosity causes increase in resistance to blood flow and thus increases MAP
- also increases work of heart

17
Q

describe how BP is regulated short term

A
  • monitored by baroreceptors and chemoreceptors located in the carotid sinus and aortic arch
  • baroreceptors are sensistive to stretch
  • chemoreceptors are sensitive to pO2 and pCO2 changes
  • information from both is regulated in the medulla oblongata
  • the ANS then makes appropriate changes to cardiac function and degree of constriction
  • involves SNS
18
Q

whata are the clinical signs of low blood pressure

A
  • poor pulse quality
  • low demenour
  • prolonged CRT
  • pale/talcy/dry mucous membranes
  • tachycardia
  • poor pulse pressure
  • weakness
  • thirst
  • dyspnoea is severe
  • cold extermities
  • tachypnoea
19
Q

what is the effect of haemorrhage

A
  • decreses preload
  • decreases stroke volume
  • decreases MAP
  • tissue oxygen delivery decreases
  • probably no change in viscosity
20
Q

describe the response to hemorrhage

A
  • baroreceptrs recognize reduced BP
  • sends signal to medulla oblongata
  • ANS increases HR and force of contraction to increase CO
  • sympathetic stimulation = noradrenaline released from nerve endings and acts on B1 receptors in heart
  • PSNS vagal tone decreased
  • HR increases (chronotropic effect
  • increased force of contraction (inotropic effect)
  • SNS stimulates adrenal gland to reduce adrenaline into blood to act on same receptors in hear (has inotropic in chronotropic effects
  • increases sympathetic stimulation of vessels leading to vasoconstriction
  • release of Anti-diuretic hormone from pituitary in response to reduced blood volume to stimulate retention of circulating volume through the kidneys. (ADH also causes vasoconstriction)
  • increases angiotensin II to increase blood vessel tone
  • increases erythropoetin to stimulate erythropoiesis and viscosity
  • decreases atrial natriuretic peptide which reduces the release from the cardiac myocytes in response to diastolic stretch, preventing ANP increased water ecretion and ANP blockade, ADH and noradrenaline release
21
Q

how is longer term control of the blood pressure regulated if high

A

regulation og the volume and composition of the blood by
- increased renal sodium excretion due to increased BP
- renin-angiotensin-aldosterone system response
- action of anti-diuretic hormone
- capillary fluid shift
- largely involves kidneys as they regulate fluid volume and electrolyte (Na mainly) composition of plasma

so when renal artery BP is elevated
- increased perfusion pressure on the kidney
- reduces Na and consequently water reabsorption in proximal tubule of kidney
- more Na and water in urine leading to increased Na and water excretion
- thus Extracellular fluid volume decreases and any elevated BP is reduced

22
Q

what is hypovolemic shock

A

loss of enough vascular fluid to cuase inadequate oxygen delivery to tissues

22
Q

what is hypovolaemia

A

fluid loss from vasculature

23
Q

what is dehydration

A

loss of fluid from extracellular fluid and intracellular fluid

24
Q

in acute hypotension, you do not see skin tenting or an altered PCV. why?

A

these are signs of dehyrdation. hypovolemic patients are not always dehydrates as fluid can be stored in other places

25
Q

what is MAP if reading is 120/75

A

90

26
Q

BP is monitored by what in the aortic arch and carotid sinus

A

baroreceptors

27
Q

i

in response to a transient decrease in BP what is tge body’s cardiac output repsonse

A

increase

28
Q

in response to blood loss, there is activation of the SNS. this leads to activation of which receptors in the heart

A

B1 receptors

Y1 CAR (81 decks)

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