Question

Explain how the sympathetic nervous system acts to directly regulate stroke volume. Include a detailed description of the mechanism (include the target cells, the proteins, signaling molecules, ions, and changes in membrane pontial where appropriate). What effect does this have on cardiac output. This will take about half a page to describe

Answer 1

1. The sympathetic influences work in conjugation with parasympathetic influences on the SA node to decrese heart rate.

2. During a short term decrese in blood pressure, the opposite occurs, and the autonomic nervous system act to increse vasoconstriction, increse stroke volume and heart rate.

3. The heart increses because of a decrese in parasympathetic activity of SA node combined with incresed sympathetic activity.

4.The stroke volume increses because of incresed ventricular contractility, manifested by an incresed ejection fraction and mediated by sympathetic nerves to ventricular myocardium.

5. Both sympathetic and parasympathetic innervation that act to increse or decrese heart rate and contractility...

6. Total peripheral resistance increses with vasoconstriction incresing arterial blood pressure making it harder for the heart to expel blood into the arteries thus reducing stroke volume.

7. All signalling molecules act by binding to receptors expressed by their target cells.

8. In many cases, these receptors are expressed on the target cell surface, but some receptors are intracellular proteins located in the cytosol or nucleus.

9. Cell signalling survival depends on elaborate intracellular communication network that coordinates the growth, differentiation and metabolism of the multitude of cells in diverse tissues and organs.

10. Cells within small groups often communicate by direct cell to cell contact of the cardiac muscle.

11.The cellular elements of heart and vascular wall are equipped with array of specific receptors and with complex intracellular machinery that facilitates and drives appropriate responses to external stimuli alters or control the cardiac output and heart rate.