Regulation of Arterial Pressure

Question 1

short term regulation of AP

Answer 1

correction achieved in at least 1-2 hours, usually within a few minutes

affects AP through changes in TPR and CO

Question 2

long-term regulation of AP

Answer 2

corrections take place over horus to days

affects AP through blood volume and CO

Question 3

arterial baroreflex

Answer 3

innervation of carotid sinus and aortic arch

efferent pulses through vagus and sympathetic nerve fibers

glossopharyngeal (IX) and vagus (X) nerves for carrying impoulses to the brain stem, where they synapse to the medulla

Question 4

stimulus for arterial baroreflex

Answer 4

radio distntion by the difference between intravascular pressure and extramural pressure

threshold pressure is about 60 mmHg and the maximum discharge rate occurs at about 200 mmHg

Question 5

What happens to blood pressure if the baroreceptors are lost to the system (denervated)?

Answer 5

the mean pressure does not change appreciably

the distribution of pressure is larger for a 24 hour period in the denervated group

Question 6

brainbridge reflex

Answer 6

lower rates lead to increased right atrial filling

causes an increase in heart rate

only seen at very low sinus rates due to direct contention with baroreceptor reflex

Question 7

atrial stretch receptors

Answer 7

stretch receptors in atrial walls, afferent fibers in sympathetic nerves and vagus nerve

sensitive to filling and atrial contraction

cardiac preload and blood volume are affected

activation produces effects similar to arterial baroreceptor stimulation with involvement of altered renal excretion of water and sodium

Question 8

ventricular baroreceptors and chemoreceptors

Answer 8

stretch receptor on anterior wall of LV

pressor reflex when stretched (increased HR and TPR)

stretch receptor on posterior wall of LV - depressor reflex when stretched (decreased HR and TPR)

Question 9

Bezold-Jarisch Reflex

Answer 9

stretch and chemoreceptors

receptors in the atria, great veins, and LV

activation or stimulation in case of ischemia may result in activation of vagal afferents and efferents

leads to hypotension, nausea,vomiting, and decreased CO

Question 10

effects of high CO2 or low O2 levels on the brain stem CV centers

Answer 10

decreased venous capacitance, increased TPR, coronary dilation, increased heart rate

Question 11

pulmonary mechanoreceptors

Answer 11

stimulation of the lung mechanoreceptors by increased rate and depth of breathing results in a net decrease in cardiac vagal efferent discharges (withdrawal)

Question 12

central chemoreceptor reflex

Answer 12

receptors on the ventral surface of the brainstem

stimuli iinclude hypercapnia, fall in pH, cerebral hypoxia, fall in cerebral perfusion pressure

response is a pressor reflex

Question 13

fight or flight response

Answer 13

heart rate and contractility increases

cardiac output increases

circulating epinephrine dilates blood flow to skeletal muscles

increased sympathetic activity decreases kidney and splanchnic flow

splanchnic cpacitance vessels are constricted

Question 14

neurocardiogenic response (vasovagal syncope)

Answer 14

sudden slowing of the heart due ot increased vagal activity and a skeletal muscle vasodilation because of decreased sympathetic output and increased cholinergic output

causes an abrupt fall in blood pressure

Question 15

diving reflex

Answer 15

intense slowing of the heart due to the parasympathetic nervous system and peripheral vasoconstriction when the face is submerged in cold water

Question 16

somatic afferent cardiovascular reflexes

Answer 16

mechanoreceptors in skeletal muscle tendons help icnrease sympathetic drive during exercise

Question 17

visceral afferent reflexes

Answer 17

activation of abdominal visceral afferents induces a reflex response

remain intact after cervical cord transection

ex. gall bladder and urinary bladder distension raises TPR by sympathoexcitation and increased AMP

Question 18

Cushing response

Answer 18

increase in intracranial pressure

threshold: intracranial and intra-arterial rpessure difference of 30-50 mmHg

Question 19

CNS reflex response

Answer 19

generalized increase in sympathetic vasoconstriction to return cerebral blood flow back to normal

Question 20

complications of severe hemorrhage

Answer 20

arterial pressres drop to below 60 mmHg

cerebral ischemia leads to vasoconstriction and tachycardia

fall in blood flow through carotid and aortic bodies leads to vasoconstriction and bradycardia

loss of more than 30% blood volume for more than 1 hours leads to irreversible hypotension and death

Question 21

rapid resposne to hemorrhage

Answer 21

activation of sympathetics

increase heart rate and contractility

increase constriction of resistance and capacitance vessels

augmented venous tone increases venous return to heart

Question 22

slow resposne to hemorrhage

Answer 22

re-establish plasma volume through renal vasoconstriction, reduced urine formation

renin and angitensin II leadss to aldosterone release and vasopressin release

reduced salt water loss from renal tubules

thirst develops to get more water input

Question 23

cardiovascular shock

Answer 23

condition characterized by multiple organ failure secondary to inadequate tissue perfusion

extreme hypotension and reduced coronary flow leads to reduced AP and tissue hypoxia and eventually ischemia

Question 24

response to weightlessness