The Regulation Of Heart Rate And Blood Pressure

The Regulation Of Heart Rate And Blood Pressure
16.6 An acute increase in extracellular fluid volume in a human
a. can stimulate both arterial baroreceptors and venoatrial stretch receptors.
b. elicits a reflex vasoconstriction in the skin, muscle and renal circulations.
c. elicits a reflex fall in circulating vasopressin.
d. elicits a rise in circulating atrial natriuretic peptide.
e. elicits a reflex activation of the renin–angiotensin system.
16.7 In the long-term control of arterial blood pressure,
a. the cardiopulmonary stretch receptors help normalize arterial
blood pressure.
b. blood pressure is influenced by extracellular fluid volume.
c. the renal regulation of body salt mass is pivotal.
d. body water mass is coupled to body salt mass via vasopressin.
e. the kidneys regulate extracellular fluid volume, but not red cell mass.
16.8 Regarding the reflex regulation of the cardiovascular system,
a. carotid chemoreceptors cause reflex peripheral vasodilatation during
The Regulation Of Heart Rate And Blood Pressure
b. lung stretch receptors excited by inflation cause a reflex tachycardia.
c. skeletal muscle mechanoreceptors (group III afferents) reflexly inhibit
cardiovagal tone.
d. skeletal muscle metaboreceptors (group IV afferents) reflexly raise blood
pressure during isometric exercise.
e. facial cold receptors cause a reflex tachycardia.
16.9 In the central control of the cardiovascular system,
a. sensory integration begins in the nucleus tractus solitarius of the medulla.
b. a projection from medullary expiratory neurons to the nucleus ambiguus
(cardiac vagal motorneurons) contributes to sinus arrhythmia.
c. a projection from the nucleus tractus solitarius to the hypothalamus
reflexly influences sympathetic vasoconstrictor outflow.
d. the cerebral cortex can raise cardiac output during exercise by
‘central command’.
e. presympathetic neurons in the rostroventrolateral medulla are organized
f. spinal transection raises blood pressure, by interrupting the net
inhibition of spinal preganglionic sympathetic neurons by descending
bulbospinal fibres.
a. involves the dilatation of resistance vessels in skeletal muscle.
b. includes cutaneous venodilatation.
c. causes a fall in blood pressure.
d. involves a rise in heart rate.
e. is organized by the limbic system and periaqueductal grey matter.
f. is impaired in many patients with hypertension.
Cardiovascular receptors, reflexes and central control Questions 109
The Regulation Of Heart Rate And Blood Pressure
Finally, here is a data interpretation problem.
16.11 The regulation of heart rate and blood pressure at the onset of static exercise.
In a study of the human response to exercise, a subject was asked to squeeze an object in the
hand with maximum voluntary force for 4 s.Within two heartbeats of starting the exercise,
heart rate had increased from 68 min1 to 80 min1
. Mean arterial pressure increased from
98 to 110 mmHg by the end of the 4 s.Afferent input from the muscles of the arm was then
blocked by injections of local anaesthetic into the axillary and radial nerves, and the study
repeated.The heart rate increased less, from 68 to 72 min1 by the second beat; blood pressure
increased from 96 to 102 mmHg by the end of the 4 s effort.
a. How could the heart rate be monitored so accurately that it was possibly to detect an
increase within two beats of starting the exercise?
b. Which branch of the autonomic nervous system is more likely to account for a change in
heart rate in under 2 s?
c. What can be inferred from the reduced cardiac response to static exercise after muscle
afferent block by local anaesthetic?
d. What types of muscle receptor might mediate the exercise pressor response?
e. Did afferent blockade completely block the tachycardia at the onset of exercise? How might
the result be interpreted?
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