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PHYSIOLOGY II > WEEK XI (Blood Pressure) > Flashcards

WEEK XI (Blood Pressure) Flashcards

1
Q

What is the equation to calculate Mean Arterial pressure (MAP)?

A

MAP = CO X TPR

CO - Cardiac output
TPR - Total peripheral resistance

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2
Q

What is Mean arterial pressure (MAP)?

A

The average pressure exerted by blood on the arterial walls during a cardiac cycle and is determined by both systolic and diastolic blood pressure values

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3
Q

Why is Mean arterial pressure important?

A

Sufficient mean arterial pressure is important to ensure an ADEQUATE DRIVING FORCE for blood flow to reach organs and tissues -> Insufficient pressure can lead to inadequate perfusion and compromise organ function

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4
Q

What can excessively high mean arterial pressure result in?

A

Strain on the heart and blood vessels which increases the risk of cardiovascular complications

(e.g hypertension can lead to vascular damage and increase the likelihood of small blood vessel rupture)

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5
Q

How does the body use neural mechanisms to regulate mean arterial pressure?

A

Neural mechanisms involve the sympathetic nervous system and baroreceptor reflexes that help maintain blood pressure within a normal range

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6
Q

How does the body use Hormonal mechanisms to regulate mean arterial pressure?

A

Hormonal regulation involves RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM which influences blood volume and systemic vascular resistance

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7
Q

How does the body use Local autoregulatory mechanisms to regulate mean arterial pressure?

A

Local autoregulatory mechanisms allow individual tissues to adjust their resistance to maintain a relatively constant blood flow despite changes in systemic mean arterial pressure

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8
Q

What determines Mean arterial pressure?

A
  • Cardiac output
  • Total peripheral resistance
  • Blood volume
  • Distribution of blood flow
  • Neural and Hormonal regulation
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9
Q

What is Cardiac output and what determines it?

A

Cardiac output is the volume of blood pumped by the heart per minute (stroke volume X heart rate)

determined by:
- PRELOAD (degree of stretch on cardiac muscle fibres before contraction determined by venous return to heart)
- CONTRACTILITY
- AFTERLOAD (resistance heart must overcome to eject blood into systemic circulation)

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10
Q

What is Total peripheral resistance and what determines it?

A

TPR is the resistance encountered by blood flow in the systemic circulation

determined by:
- ARTERIOLAR CONSTRICTION/DILATION
- VISCOSITY OF BLOOD
- BLOOD VESSEL LENGTH (longer vessels offer greater resistance to flow)

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11
Q

What is blood volume and what determines it?

A

The total volume of blood circulating in the body

determined by:
- FLUID INTAKE AND ABSORPTION
- FLUID LOSS
- REGULATION BY THE KIDNEYS

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12
Q

What can distribution of blood flow be determined by?

A

Vasoconstriction and Vasodilation

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13
Q

What can activation of the sympathetic nervous system lead to?

A

Vasoconstriction and increased heart rate affecting both CO and TPR

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14
Q

Which hormones contribute to blood pressure regulation?

A
  • Renin
  • Angiotensin
  • Aldosterone
  • Antidiuretic Hormone (ADH)
  • Atrial natriuretic peptide (ANP)
  • Endothelin
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15
Q

What is MAP constantly monitored by?

A

Baroreceptors

[deviations from the normal MAP trigger reflex responses to restore it to its normal value]

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16
Q

What is the difference between Short-term adjustments to MAP and Long-term adjustments to MAP?

A

SHORT-TERM = occur within seconds and involve alterations in cardiac output (CO) and total peripheral resistance (TPR) -> Autonomic influences lead to changes in heart rate, contractility, venous constriction/dilation and arteriolar constriction/dilation

LONG-TERM = takes minutes to days involve adjusting total blood volume -> normal salt and water balance is restored through urine output and thirst regulation

17
Q

Describe the Baroreceptor reflex

A

Receptors are the CAROTID SINUS BARORECEPTORS and AORTIC ARCH BARORECEPTORS which are sensitive to changes in MAP

Baroreceptors in the autonomic nervous system generate action potentials in response to arterial pressure -> When MAP increases the RECEPTOR POTENTIAL in the baroreceptors increases leading to an INCREASED RATE OF FIRING in the AFFERENT NEURONS (opposite when decreases) -> MEDULLA in the brain stem adjusts balance between sympathetic and parasympathetic activity in response to afferent impulses -> Parasympathetic stimulation decreases HR and STROKE VOLUME while sympathetic stimulation increases HR, STROKE VOLUME and induces ARTERIOLAR and VENOUS CONSTRICTION

18
Q

What is the Baroreceptor reflex?

A

A feedback mechanism that responds to changes in mean arterial pressure (MAP) to maintain blood pressure within a normal range

19
Q

What happens when MAP rises above normal?

A

Baroreceptors increase their firing rate -> Decrease in sympathetic and increase in parasympathetic activity -> Decreased HR, stroke volume and vasodilation -> Decreasing CO and TPR sonf bringing blood pressure back to normal

20
Q

What happens when MAP falls below normal?

A

Baroreceptor activity decreases -> Increase in sympathetic and decrease in parasympathetic output -> Increased HR, stroke volume, vasoconstriction, CO and TPR -> Rise in blood pressure back to normal

21
Q

What are the factors that influence the cardiovascular system and blood pressure?

A
  • LEFT ATRIAL VOLUME RECEPTORS AND OSMORECEPTORS = regulate water and salt balance -> long-term pressure regulation
  • CHEMORECEPTORS = sensitive to low O2 or high acid levels -> increase respiratory activity to improve oxygenation or eliminate excess CO2
  • CERTAIN EMOTIONS
  • HYPOTHALMIC CONTROL OVER CUTANEOUS ARTERIOLES FOR TEMP REGULATION = blood pressure can drop during vasodilation despite baroreceptor calling for vasoconstriction
  • EXERCISE
22
Q

What are the two types of hypertension?

A
  • SECONDARY HYPERTENSION = caused by an identifiable underlying condition e.g kidney disease
    [problem leads to WATER RETENTION -> expanding blood volume & chronically increasing blood pressure]
  • PRIMARY HYPERTENSION = no specific identifiable cause and is influenced by genetics & lifestyle choices
23
Q

Why is hypertension harmful?

A

Prolonged exposure to elevated blood pressure damages the walls of blood vessels making them more susceptible to ATHEROSCLEROSIS -> Narrows lumens, increases total peripheral resistance which further raises blood pressure -> Harmful positive feedback

24
Q

What is classed as “prehypertension”?

A

Blood pressures between 120/80 and 140/90

Blood pressures in this range can be reduced through appropriate dietary and exercise measures

25
Q

Describe the effect of kidneys in maintaining blood pressure

A

A high-salt diet can increase plasma osmolality leading to the secretion of antidiuretic hormone (ADH) -> Increased ADH levels cause water reabsorption by the kidneys increasing BLOOD VOLUME, CARDIAC OUTPUT and BLOOD PRESSURE -> Kidneys should excrete excess salt and water to prevent

[with age the ability to excrete sodium declines due to a decrease in GLOMERULAR FILTRATION RATE]

26
Q

What happens when there are high levels of aldosterone secretion?

A

High levels of aldosterone secretion stimulates salt and water reabsorption -> indicated by elevated levels of RENIN and increased production of ANGIOTENSIN II (stimulator of aldosterone secretion)

27
Q

What does increased endothelin and decreased nitric oxide do?

A

Increased endothelin (vasoconstrictor) and decreased nitric oxide (vasodilator) increased peripheral resistance -> increases MAP

28
Q

What are complications of hypertension?

A
  • Left ventricular atrophy and systolic heart failure
  • Strokes (rupture of brain vessels)
  • Heart attacks (rupture of coronary vessels)
  • Kidney failure (impaired blood flow through damaged renal blood vessels)
  • Retinal damage
29
Q

What are lifestyle modifications to treat hypertension?

A
  • Quitting smoking
  • Moderating alcohol intake
  • Weight reduction
  • Regular exercise
  • Reducing sodium intake
30
Q

What medications can be prescribed to treat hypertension?

A
  • Diuretics (increase urine volume -> reduce blood volume and pressure)
  • β1-adrenergic receptor blockers (lower BP by decreasing HR)
  • ACE inhibitors
  • Calcium channel blockers
  • Angiotensin II-receptor blockers (ARBs) (block binding -> reduces vasoconstriction and salt/water retention)
31
Q

When does Hypotension occur?

A

When there is a disparity between vascular capacity and blood volume or when the heart is too weak to pump an adequate amount of blood

32
Q

What is Transient orthostatic hypotension?

A

A situation where blood pressure drops temporarily upon changing positions and results from insufficient compensatory response due to gravitational shifts in blood during position changes

33
Q

What happens when a person stands up?

A

Blood pools in the leg veins due to gravity which reduces venous return, stroke volume, cardiac output and blood pressure -> Baroreceptors detect the drop in BP and initiate responses to restore it to normal -> In some individuals the reflex is impaired

34
Q

When does Circulatory shock occur?

A

Occurs when blood pressure drops to a level where adequate blood flow to tissues cannot be maintained

35
Q

What causes circulatory shock?

A
  • HYPOVOLEMIC SHOCK = excessive loss of blood
  • CARDIOGENIC SHOCK = inadequate pumping of blood by a weakened heart
  • VASOGENIC SHOCK = arteriolar vasodilation
  • NEUROGENIC SHOCK = defective vasoconstrictor tone due to neural dysfunction
36
Q

What factors contribute to irreversible shock?

A
  • METABOLIC ACIDOSIS (due to increased lactate production)
  • KIDNEY DYSFUNCTION (electrolyte imbalances & cardiac arrhythmia)
  • RELEASE OF MYOCARDIAL TOXIC FACTOR (by blood-deprived pancreas)
  • ACCUMULATION OF VASODILATOR SUBSTANCES WITHIN ISCHEMIC ORGANS
37
Q

What happens in irreversible shock?

A

Cardiac output declines and total peripheral resistance continues to fall -> Severe hypotension worsens the cardiovascular failure -> Positive-feedback cycle leading to further decline in blood pressure & death

38
Q

What are the effects of Angiotensin II?

A
  • Causes muscular walls of arterioles to constrict -> increasing blood pressure
  • Triggers adrenal glands to release aldosterone and pituitary gland to release ADH

PHYSIOLOGY II (15 decks)

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