Ch 18 Nervous regulation Flashcards
There is sympathetic innervation of the systemic circulation except for?
capillaries
The most important part of the autonomic nervous system for regulating the circulation is the?
sympathetic nervous system
What is the parasympathetics most important circulatory function?
controlling the heart rate by way of parasympathetic nerve fibers (vagus nerve)
Do the sympathetic nerves carry vasoconstrictor nerve fibers or vasodilator nerve fibers?
both; however very few vasodilator
Where is the vasomotor center located?
bilaterally in the reticular substance of the medulla and the lower third of the pons
What does the vasomotor center do?
transmits parasympathetic impulses through the vagus nerves to the heart and sympathetic impulses through the spinal cord and peripheral sympathetic nerves
What is sympathetic vasoconstrictor tone?
The vasomotor system transmits signals continuously to the sympathetic vasoconstrictor nerve fibers at a rate of 0.5-2 impulses per second
vasomotor tone is…
partial state of contraction in blood vessels
What are the 3 major changes the nervous system causes to rapidly increase arterial pressure?
- most arterioles of the systemic circulation are constricted
- The veins (especially the larger ones) are strongly constricted increasing volume
- the heart is directly stimulated by the autonomic nervous system, further enhancing cardiac pumping
T/F: the nervous system is the most rapid mechanism for arterial blood pressure regularion
true
Most well known mechanism for arterial blood pressure control?
Where are they located?
baroreceptor reflex
specific points in the walls of several large system arteries
How do baroreceptors receive input?
A rise in arterial pressure stretches the baroreceptors and causes them to transmit signals to the CNS
Where are baroreceptors most abundant?
the wall of each internal carotid and the wall of the aortic arch
In what situation do baroreceptors respond the most?
Rapidly changing pressures rather than high static pressures
After baroreceptor signals enter the medulla, what happens?
secondary signals inhibit the vasoconstrictor center of the medulla and excite the vagal parasympathetic center
What are the net effects of the signals from the baroreceptors?
- vasodilation of the veins and arterioles throughout the peripheral circulatory system
- decreased heart rate and strength of contraction
Why is the baroreceptor system called the pressure buffer system?
It opposes either increases or decreases in arterial pressure
Why are baroreceptors not important for long term control of blood pressure?
They reset in 1-2 days to the pressure they are exposed
What are chemoreceptors and where are they located?
chemosensitive cells sensitive to low oxygen, carbon dioxide excess, and hydrogen ion excess; in chemoreceptor organs: 2 carotid bodies, one at each bifurcation of each common carotid and 1-3 aortic bodies adjacent to the aorta
Describe what happens in regards to chemoreceptors when arterial pressure falls below a critical level
chemoreceptors become stimulated because of the diminished oxygen and build up of CO@ and H ions. Signals transmitted from the chemoreceptors excite the vasomotor center which elevates the arterial BP
What are the receptors in the atria and ventricles? what is their role?
low pressure receptors
minimizing arterial BP changes in response to changes in blood volume
Stretch of the atria causes reflex _________ of the ________ arterioles in the kidney
dilation
afferent
How can stretch of the atria affect ADH release?
Signals transmitted from the atria to the hypothalamus to decrease secretion of ADH
Explain the Bainbridge reflex
Stretch receptors in the atria that elicit the reflex transmit their afferent signals to the medulla. Efferent signals are transmitted back through vagal and sympathetic nerves to increase HR and strength of contraction
