exam 3 - cardiac output, blood flow, and blood pressure: part #2

Question 1

three things that exercise training does

Answer 1

1. increases the density of coronary arterioles and capillaries
2. increases the production of nitric oxide for promoting vasodilation
3. decreases the compression of the coronary vessels in systol, due to lower cardiac rate

Question 2

what are cardiovascular changes during exercise affected by?

Answer 2

• motor cortex
• sensory feedback from contracting muscles
• baroreceptor reflex

Question 3

the blood flow through dynamically exercising muscles increases due to…

Answer 3

• increased total blood flow (cardiac output)
• metabolic vasodilation in the exercising muscles
• diversion of blood away from the viscera and skin, due to vasoconstriction in these organs (by increased activity of adregnergic sympathetic fibers)

Question 4

why does cerebral blood flow decrease during heavier exercise (>60% maximal oxygen uptake)?

Answer 4

becuse the person hyperventilates, which lowers blood CO2 and produces cerebral vasoconstriction

Question 5

autoregulation

Answer 5

• in a normal range of arterial pressures, cerebral blood flow is regulated almost exclusively by local intrinsic mechanisms
  
  • only when the mean arterial pressure rises to about 200mmHg do sympathetic nerves cause a significant degree of vasoconstriction in cerebral circulation
    
    • this helps to protect arterioles from bursting and to prevent stroke
• achieved by myogenic and metabolic mechanisms

Question 6

the role of carbon dioxide concentration in cerebral vessels (myogenic regulation)

Answer 6

• when carbon dioxide concentration rises as a result of hypoventilation, the cerebral arterioles dilate
  
  • due to decreases in pH of cerebrospinal fluid
• when arterial CO2 falls below normal during hyperventilation, the cerebral vessels constrict

Question 7

hyperemic

Answer 7

blood flow to active brain regions exceeds the aerobic requirements of the active neurons

Question 8

astrocytes role in cerebral blood flow

Answer 8

• astrocytes secrete vasodilator chemicals (including prostglandin E₂ and carbon monoxide) when stimulated by glutamate

Question 9

neurovascular coupling

Answer 9

• neurons, astrocytes, and arterioles function together so that increased neuronal activity in a local brain region is accompanied by an increased cerebral blood flow to that region (functional hyperemia)

Question 10

bradykinin

Answer 10

a polypeptide secreted by sweat glands that stimulates vasodilation

Question 11

what happens to cutaneous blood flow as the temperature warms?

Answer 11

• decreased activity of the sympathetic vasoconstrictor (adrenergic) axons to the skin, allowing dilation
  
  • with further warming, there is increased activity of sympathetic cholinergic axons to the skin; these stimulate sweat glands

Question 12

most important variables affecting blood pressure

Answer 12

• cardiac rate
• stroke volume (determined primarily by the blood volume)
• total peripheral resistance

Question 13

how does sympathetic stimulation affect blood volume indirectly?

Answer 13

by stimulating constriction of renal blood vessels and thus reducing urine output

Question 14

changes in cutaneous blood flow occur as a result of changes in what?

Answer 14

sympathetic nerve activity

Question 15

baroreceptors

Answer 15

• located in aortic arch and carotid sinuses
• stretch receptors
• sensory nerve activity from baroreceptors ascends via the vagus (X) and glossopharyngeal (IX) nerves to the medulla oblongata, which directs the autonomic system to respond appropriately

Question 16

what does the baroreceptor reflex consist of?

Answer 16

1. aortic arch and carotid sinus baroreceptors as the sensors
2. vasomotor and cardiac control centers of the medulla oblongata as the integrating centers
3. parasympathetic and sympathetic axons to the heart and blood vessels as the effectors

Question 17

the reflex of raising or lowering of blood pressure is due mainly to what? secondarily?

Answer 17

• the reflex of raising or lowering blood pressure is due mainly to sympathetic nerve regulation of total peripheral resistance and secondarily to the reflex raising or lowering of cardiac output

Question 18

most important regulator of arterial blood pressure on a beat-to-beat basis? longer term regulation?

Answer 18

• beat-to-beat basis is the baroreceptor reflex
• longer-term regulation achieved by the kidneys, through regulation of blood volume

Question 19

laminar flow

Answer 19

occurs when all parts of a fluid move in the same direction, parallel to the axis of the vessel

Question 20

turbulent flow

Answer 20

when some parts of a fluid move in different directions, churning and mixing the blood

turbulent flow causes vibrations of the vessel, which may produce sounds

Question 21

first Korotkoff sound

Answer 21

when the cuff pressure is equal to the systolic pressure

Question 22

last korotkoff sound

Answer 22

occurs when the cuff pressure is equal to the diastolic pressure

Question 23

pulse pressure

Answer 23

= systolic pressure - diastolic pressure

reflection of stroke volume

Question 24

causes of secondary hypertension

Answer 24

• kidney disease
• arteriosclerosis of the renal arteris
• reduction of renal blood flow, which leads to elevated renin secretion

Question 25

explanation for association between dietary Na and hypertension

Answer 25

• high salt diet increases plasma osmolality –> stimulates ADH secretion –> increased water reabsorption by the kidneys –> increasing blood volume –> increases cardiac output and blood pressure

Question 26

contributors to essential hypertension

Answer 26

• inappropriately high levels of aldosterone secretion, because the person has normal or even elevated levels of renin
• increased activity of the sympathoadrenal system, promoting vasoconstriction and raising peripheral resistance
• peripheral resistance increased by secretion of paracrine regulators including:
  
  • increased endothelin (vasoconstrictor)
  • decreased nitric oxide (vasodilator)

Question 27

final common pathway in essential hypertension

Answer 27

kidney function

Question 28

dietary potassium influence on relationship between dietary salt and hypertension

Answer 28

• a diet low in patassium enhances the ability of a high-sodium diet to raise BP, whereas a high potassium diet has the opposite effect
  
  • a potassium-rich diet increases renal flow and acts as a diuretic to lower blood volume and pressure

Question 29

“silent killer”

Answer 29

hypertension (because most patients are asymptomatic until substantial vascular damage has occurred)

Question 30

drugs that can be prescribed for hypertension

Answer 30

• diuretics
• drugs that block beta-1-adrenergic receptors (i.e. atenolol)
  
  • lower BP by decreasing cardiac rate
• ACE (angiotensin-converting enzyme) inhibitors
• calcium antagonists
• various vasodilators
• angiotensin II-receptor blockers (ARBs) - allows angiotensin II to be formed but blocks the binding of angiotensin II to its receptors
• drugs that inhibit renin activity and reduce activity of renin-angiotensin-aldosterone system

Question 31

most commonly prescribed drugs for treatment of hypertension

Answer 31

• ACE (angiotensin-converting enzyme) inhibitors
• angiotensin II receptor blockers (ARBs)

Question 32

circulatory shock

Answer 32

occurs when there is inadequate blood flow and/or oxygen utilization by the tissues

Question 33

hypovolemic shock

Answer 33

• circulatory shock that is due to low blood volume
• caused by hemorrhage, dehydration, or burns
• the sympathoadrenal system is activated by the baroreceptor reflex
  
  • this causes tachycardia and vasoconstriction (in skin, digestive tract, kidneys, and muscles)
• a person in hypovolemic shock has low blood pressure, a rapid pulse, cold clammy skin, and reduced urine output

Question 34

septic shock

Answer 34

• dangerously low BP that may result for sepsis, or infection
• may occur through the action of a bacterial lipopolysaccharide called endotoxin
  
  • this endotoxin activates the enzyme nitric oxide synthase with macrophages
• tx. with drugs that inhibit the production of nitric oxide

Question 35

anaphylactic shock

Answer 35

• result of severe allergic reaction (bee stings, penicillin)
  
  • widespread release of histamine, causes vasodilation and decrease in total peripheral resistance

Question 36

neurogenic shock

Answer 36

• rapid fall in BP
• decreased sympathetic tone, usually because of upper spinal cord damage or spinal anesthesia

Question 37

cardiogenic shock

Answer 37

• results from cardiac failure
  
  • inadequate cardiac output to maintain tissue perfusion
  • commonly results from infarction
  • may also result from severe cardiac arrhythmias or valve damage

Question 38

most common causes of left ventricular heart failure

Answer 38

• myocardial infarction
• aortic valve stenosis
• incompetence of the aortic and bicuspid valves

Question 39

electrolyte concentration disturbances in heart failure

Answer 39

• high blood K and low blood Ca can cause the heart to stop in diastole
• low blood K and high blood Ca can arrest the heart in systole

Question 40

compensatory responses that occur during congestive heart failure

Answer 40

• activations of sympathoadrenal system
  
  • stimulates cardiac rate, ventricle contractility, and arteriole constriction
  • increased renin secretion and reduced urine output
    
    • this occurs despite an increased secretion of atrial natriuretic peptide (which would have the compensatory effect of promoting salt and water excretion)

Question 41

treatment for CHF

Answer 41

• first line of treatment:
  
  • angiotensin-converting enzyme inhibitors
  • angiotensin II receptor blockers
• beta-adrenergic receptor blockers with digitalis to increase myocardial contractility
• nitroglycerin (vasodilator)
• diurectics