A&P Chapter 18
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What is a detector?
sensor or receptor
The afferent neural pathway travels from _____ to ______
detector to CNS
What is the coordinating center?
Receives and processes signal from detector then generates an appropriate response
The efferent neural pathway travels from ______ to _______
coordinating center to effectors
What are effectors
carry out the response
What are two types of detectors/receptors for controlling MAP? What do they sense?
- Baroreceptors - stretch, vascular wall distention
- Chemoreceptors - changes in blood o2, co2, pH
What 3 places are control centers for controlling MAP located?
- 1) Medulla
- 2) Cerebral Cortex
- 3) Hypothalamus
What are 3 types of effector cells for controlling MAP?
- 1) Pacemaker cells of the heart
- 2) Vascular smooth muscle cells
- 3) Adrenal Medulla
What are the 3 components of the vasomotor center?
- 1) vasoconstrictor
- 2) vasodilator
- 3) sensory
What is a major function of the vasoconstrictor portion of the vmc? how does it accomplish this?
vasomotor tone - through continuous signaling to sympathetic vasoconstrictor nerve fibers
What is the primary neurotransmitter involved in vasomotor tone?
How does the vasodilator area in the VMC work? What area controls this?
it inhibits vasoconstrictor activity to cause vasodilation. Controlled by the anterior hypothalamus.
What does the cardioaccelerator area of the VMC control?
heart rate and contractility
The lateral and medial area of the vmc have different functions. What are these? How is this accomplished?
Lateral - transmits excitatory signals via sympathetic fibers to the heart to increase rate and contractility (NE -->beta 1 on SA node)
Medial - transmits inhibitory signals via vagus nerve to decrease heart rate and contractility (ach --> m2)
Where is the sensory portion of the vmc? What nerves does it receive input from? What are its effectors?
- 1) Tractus Solitarus in the posterior lateral portions of the medulla and lower pons
- 2) vagus and glossopharyngeal
- 3) vasoconstrictor and vasodilator areas
Where are baroreceptors located?
the carotid sinus and the walls of the aortic arch
Describe the path of the baroreceptors from the carotid sinus to the medulla.
carotid sinus --> Hering's nerve --> glossopharyngeal nerve --> nucleus tractus solitarius of the medulla
Describe the path from the aortic arch to the medulla.
aortic arch --> vagus nerve --> nucleus tractus solitarius of the medulla
What range of mean arterial pressure do the baroreceptors work? Where is it the strongest?
What happens when signals arrive in the Nucleus tractus solitarius?
- 1) vasoconstrictor area in the medulla is inhibited
- 2) vagal parasympathetic center is excited
Where are chemoreceptors located?
- 1) carotid bodies near the carotid bifurcation
- 2) aortic arch
When are the chemoreceptors activated? what do they do?
- 1) in response to decreased o2, pH or increased co2 when the MAP is < 80
- 2) they increase SNS activity
Describe the CNS ischemic response
cerebral ischemia --> increased CO2 --> vasomotor center --> increased sympathetic activity --> incrusted arterial pressure
At what blood pressure in the CNS ischemic Response active?
What is Cushing reaction?
A type of CNS ischemic response when the pressure in the CSF = SBP which causes arteries in brain to compress so that blood supply is cut off --> CNS ischemic response to increase SBP above CSF pressure
What happens in the atrial and pulmonary artery reflexes?
low pressure receptors sense an increase in pressure/blood volume --> lowering arterial pressure
Also, decreased release of ADH, increased GFR, decreased Na reabsorption --> lowering of ECFV
What is the bainbridge reflex?
increase in atrial pressure --> vagus nerve --> VMC --> increased HR/contractility
What is a normal respiratory wave? What does it mean if it increases?
4-6 mmHg, if increased, it indicates hypovolemia
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