chapter 18- Exam 3 Flashcards
how do the nerves regulate the circulation
- Redistribution of blood flow
- Increasing pumping activity of the heart
- Rapid control of arterial pressure
- Regulates via the autonomic nervous system
what is apart of the autonomic nervous system
Sympathetic nervous system
Parasympathetic nervous system
what does the Sympathetic nervous system control in circulation
is important in control of circulation
what does the Parasympathetic nervous system control in circulation
is important in regulating heart function
what is the Parasympathetic nervous system main control in circulation
mainly controls heart rate via the vagus nerve
what does the Sympathetic nervous system innervate
Innervate Most vessels
- small arteries,
- arterioles,
- large veins
- heart
what doesNT the Sympathetic nervous system innervate
Do Not Innervate
- capillaries
- Precapillary sphincters
- some metarterioles
what does the Sympathetic nervous system do for the circulation
Increase vascular resistance
where are the sympathetic vasoconstrictor systems located
Vasoconstrictor fibers are distributed throughout all segments of the circulation
where is the sympathetic vasoconstrictor systems in the MOST
Distribution is greater in kidneys, gut, spleen, and skin
where is the sympathetic vasoconstrictor systems in the LEAST
Less potent in coronary circulation and the brain
what equals arterial pressure
Q x total peripheral resistance
what can increase arterial pressure
=constricting arterioles
=constricting veins
=directly increasing Q
what does constricting arterioles do for increasing arterial pressure
which increases total peripheral resistance
what does constricting veins do for increasing arterial pressure
(mostly veins, but some other large vessels) increasing venous return and cardiac output
what does directly increasing Q do for increasing arterial pressure
by increasing heart rate and contractility
what does the vasomotor center do
VMC transmits impulses downward through the cord to almost all blood vessels
where is the VMC located
is located bilaterally in the reticular substance of the medulla and the lower third of the pons
what is the VMC composed of
- vasoconstrictor area
- vasodilator area, and
- sensory area
what does the vasoconstrictor area of the VMC do
Transmits signals continuously to sympathetic nerve fibers → sympathetic vasoconstrictor tone
***This maintains partial state of contraction in blood vessels called vasomotor tone
Look at slide
9 there is a flow chart
how does the nervous system increase the arterial pressure
via the VMC
how does the VMC increase arterial pressure in seconds
- constricting arterioles
- constricting veins
- directly increases Q
when can rapid increase in arterial pressure occur
during exercise or with a fright
look at slide
10 there is a flow chart at the bottom
when is the arterial baroreceptor reflex important
in short term regulation of arterial pressure
how is the baroreceptor reflex initiated
Reflex is initiated by stretch receptors called baroreceptors or pressoreceptors located in the walls of the large systemic arteries
what does the rise in pressure in the arterial do
A rise in pressure stretches baroreceptors and causes them to transmit signals to the VMC and feedback signals are sent via the automonic nervous system to the circulation to reduce AP back to normal
where are the Baroreceptors located
Baroreceptors are located in the walls of the carotid bifurcation called the carotid sinus and in the walls of the aortic arch
how are signals form the carotid sinus transmitted
Signals from the carotid sinus are transmitted by the Hering’s nerve to the glossopharyngeal nerves and then to the nucleus tractus solitarius (NTS) of the medulla
how are the signals from the arch of the aorta transmitted
Signals from the arch of the aorta are transmitted through the vagus into the NTS
when do the carotid sinus receptors respond
baroreceptors respond to pressures between 60 and 180 mmHg
what do the Baroreceptors respond to
respond to changes in arterial pressure
when are the Baroreceptors the most sensitive
is most sensitive at a pressure of 100mmHg
what happens when a pressure increases and the number of impulses from the carotid sinus increase
1) Inhibition of the vasoconstrictor
2) Activation of the vagal center
what are the fx of the Baroreceptors
**Maintains relatively constant pressure despite changes in body posture
**Opposes either increases or decreases in arterial pressure thereby reducing daily variations in arterial pressure
**They are unimportant in long term control of arterial pressure because the baroreceptors adapt
Look at slides
14, 15
what are chemoreceptors
Chemoreceptors are chemosensitive cells sensitive to oxygen lack, CO2 excess, or H ion excess
where are chemoreceptors located
are located in carotid bodies near the carotid bifurcation and on the arch of the aorta
what does the activation of chemosensitive receptors result in
in excitation of the vasomotor center
when are chemoreceptors stimulated
they will not stimulated until pressure falls below 80mmHg
– look at slide 16 at pic and chart
when is the CNS ischemic response activated
in response to cerebral ischemia
what happens when there is reduced cerebral blood flow
causes CO2 buildup which stimulates vasomotor center thereby increasing arterial pressure
what is the most powerful activators of the sympathetic vasoconstrictor system
CNS Ischemic response
–look at slide 17 at the pic and the flow chart at the bottom
when will the CNS ischemic response be activated
CNS Ischemic response is not activated until pressure falls below 60mmHg; Greatest activation occurs at pressures of 15-20mmHg
what is a special type of CNS ischemic response
cushing reaction
what effect does a prolonged CNS ischemia response have
Prolonged CNS ischemia has a depressant effect on the vasomotor center
what do the low pressure receptor in the atria and the pulmonary arteries do
minimize arterial pressure changes in response to changes in blood volume
what activates the low pressure receptors
Increases in blood volume activates low pressure receptors which in turn lower arterial pressure
what does the activation of the low pressure receptors enhances
Na and water
how does the activation fo the low pressure receptors enhances NA and water
- Decreasing rate of antidiuretic hormone
- Increasing glomerular filtration rate
- Decreasing Na reabsorption
