Nervous Regulation of the Circulation and Rapid Control of Arterial Pressure Flashcards
T/F parasympathetic plays a major role in regulation of circulation
False. Plays a minor role but important role in regulating heart function.
Sympathetic nerves fibers innervate all vessels except
capillaries, precapillary, precapillary sphincters and some metarterioles
Sympathetic nerves release what hormone and activates what receptor?
Noepinephrine on alpha adrenergic receptors on smooth muscle cells in blood vessels.
Adrenal medulla
Holds/releases noepinephrine and epinephrine that’ll be transmitted to blood vessels.
Sympathetic vasoconstrictor especially effect
Kidneys, gut, spleen, and skin but less potent in skeletal muscle and brain.
Sympathetic stimulation increases or decreases arterial pressure?
Increases
Sympathetic stimulation causes 3 things to increase arterial pressure
1-Constricting almost all arterioles of body to increase total peripheral resistance (alpha receptor)
2-Constrict large veins which increases venous return and cardiac output. DECREASES COMPLIANCE (alpha receptor)\
3-Stimulating heart to increase heart rate and contractility (beta receptors)
THESE THREE THINGS ALWAYS HAPPEN WHEN SYMPATHETIC STIMULATON.
Vasomotor Center
Collection of cell bodies in medulla oblongata (brain stem cell) that regulates blood pressure and cardiac function primarily through the ANS.
3 Important areas of the vasomotor center
Vasoconstrictor region
Cardiac region
Sensory region
Vasoconstrictor area tones
Transmits signals CONTINUOUSLY to sympathetic nerve fibers. Sympathetic tone (think how SA node fires continuously)
These impulses maintain partial state of contraction in smooth muscle cells in blood vessels=VASOMOTOR TONE
If you cut sympathetic tone to blood vessels what would happen?
No constriction of blood vessels. So atrial pressure would fall, No noepinephrine would be released to stimulate constriction in blood vessels.
Cardiac centers
1-Cardiac accelerator area: increases HR. Transmits signals to regulate sympathetic nerves to the heart. Noepinephrine activating beta receptors.
2-Cardioinhibitory area: decrease HR. Dorsal motor nuclei of vagus nerve. Transmits parasympathetic impulses to heart through vagus nerve. Acetylcholine actiating muscarinic receptors.
T/F There are parasympathetic nerves to the heart
True
Sensory area
Located in nucleus tractus solitarius (NTS)
Receives sensory input from baroreceptors located in body
Output controls activity of: vasoconstrictor area. cardiac inhibitory area, cardiac accelerator area
REFLEX CONTROL OF CIRCULATORY FUNCTION
Reflex control of circulatory
Reflex= what happens after increase/decrease of blood pressure.
Negative feedback mechanisms (for reflex) for maintaining normal arterial pressure (4)
1-Baroreceptor reflex
2-Chemoreceptor reflec
3-Atrial and pulmonary reflex
4-CNS ischemic response
Baroreceptors
Located in walls of carotid sinus and aortic arch
Sensory afferents (aortic, herings nerve, glossopharyngeal nerve)
Terminate in NTS
Baroreceptors response to changes in pressure
Blood pressure increase= increase impulses to brain
Blood pressure decreases= decreases impulses to brain
Baroreceptor reflex overview
Senses pressure changes
Transmits info to sensory area (NTS)
Symp and parasymp activity altered to bring pressure back to set point. POINT SET BY KIDNEYS
What would happen if there was a decrease in arterial pressure? (dog hit by car or hemorrhaging)
Decreased blood volume causes decrease in arterial pressure
Heart rate increased. Blood pressure decreased.
Reflex tachycardia
Cardiac accelerator area increases nerve firing (sympathetic). Blood vessels constrict in kidneys, GI. Blood flow to kidneys would decrease and resistance to kidneys would increase.
Vasoconstrictor center would increase.
Parasympathetic regulation would decrease.
What would happen when arterial pressure is increased?
Vasoconstrictor firing decreases. Blood vessels dilate. Tissues get more blood. Blood pressure increases, heart rate decreases.
Reflex bradycardia.
Body posture and baroreceptors
Lying–>Standing
Decrease in arterial pressure in head and upper body
Fallnig pressure sensed by BR and increased sympathetic discharge maintains pressure.
Buffer function of the baroreceptors
- reduces moment to moment variations in arterial pressure (tries to keep things constant)
- UNIMPORTANT IN LONG TERM CONTROL OF ARTERIAL PRESSURE (Kidneys job)
Carotid and Aortic Chemoreceptors monitor chemicals if pressure is…
BELOW NORMAL
decrease O2, increase CO2, decrease pH
