BIOL 221 Lecture Notes - Lecture 4: Adrenal Medulla, Medulla Oblongata, Vasomotor Center
11 Feb 2020
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Document Summary
The short-term response to falling blood pressure involves three mechanisms: neural control of heart rate, neural control of blood vessel diameter, and adrenal control of heart rate and blood volume. The neural response to decreased blood pressure starts with decreased stimulation of baroreceptors. When baroreceptors are less stimulated, they generate fewer afferent impulses to the cardiovascular centers within the medulla oblongata. The vasomotor center (vmc) and cardioacceleratory center (cac) are not inhibited and the cardioinhibitory center (cic) is not stimulated. Sympathetic outflow to the heart and blood vessels increases and parasympathetic outflow to the heart decreases. The short-term adrenal medullary response to falling blood pressure is slightly slower to take effect than neural control; effects are slightly longer lasting. When blood pressure decreases, stimulation of baroreceptors decreases. Again, they send fewer afferent impulses, which then increases sympathetic outflow to the adrenal medulla. This stimulation (by preganglionic neurons) causes increased release of the adrenal hormones norepinephrine and epinephrine.
