Question

2. Jolene wakes suddenly to her alarm clock and realizes that she is late for her 9:15am CBIO2210 class. She jumps to her feet, feels dizzy and lightheaded for a moment, then hops into the shower. Draw a diagram / flowchart / picture of the sequence of events that occurred when she jumped up that overcame her dizzy feeling and prevented her from losing consciousness. Include the receptors, the control center, at least one effector site, information traveling between receptors / control center / effectors, and the response.

Answer 1

When Jolene woke up and realized that she was late for class, she began hurriedly doing everything. When one stands up suddenly after lying down for a long time, gravity causes blood to pool in the veins of the leg. This sudden decrease in venous return to the heart causes the blood pressure to fall. This can make the person feel dizzy and light-headed. When this happens, the baroreceptors in the aortic arch and carotid sinus get activated and the baroreceptor reflex sets in. The baroreceptor reflex ensures that the blood pressure to the brain is maintained and one does not lose consciousness.

Receptors - Baroreceptors in the Aortic arch and Carotid Sinus

Control center - Brainstem (nucleus of the solitary tract)

Effector sites - Smooth muscles in the walls of the artery

Response - Stimulation of the sympathetic nervous system. Contraction of the smooth muscles in the arteries leading to vasoconstriction and compensatory rise in blood pressure.