Reflex control of circulation Flashcards
What does short-term (extrinsic) control include?
– neural reflexes
– hormonal mechanisms
What does short-term local control include?
– biomechanical
– humoral
– metabolic
– neural
What does long-term control include?
– blood volume (kidney!)
– vascular remodeling
What does respiratory system include?
peripheral and central interactions
Make a Flow chart describing the baroreflex.
NTS: nucleus tractus solitarii SNS, PNS: sympathetic & parasympathetic nervous system
Make a Schematic sagittal view of the medulla oblongata depicting neural pathways involved in neurogenic hypertension.
What happens, when we suddenly stand up and get dizzy for a moment?
What is Bainbridge reflex
The tachycardia caused by increased venous return
-> Bainbridge found that infusing blood or saline into the animal increased heart rate.
-> This phenomenon occurred even if arterial blood pressure did not increase. He further observed that heart rate increased when venous pressure rose high enough to distend the right atrium, but denervation of the vagi to the heart eliminated these effects.
How does Bainbridge reflex occur in animals?
increased firing of B-fibers. B-fibers send signals to the brain, which then modulates both sympathetic and parasympathetic pathways to the SA node.
How does Bainbridge reflex occur in human?
stretch of SA node
Make a graph for Bainbridge reflex and baroreflex
Alternating activity of sympathetic and parasympathetic influence
-> Match the nerves to appropriate graph
Respiratory sinus arrhitmia
-> What are the central interactions?
During inspiration a (partial) inhibition over vagal activity
Respiratory sinus arrhitmia
-> What are the peripheral causes?
- During inspiration thoracoabdominal pump mechanism aiding venous return
- Negative thoracal pressure keeps it back
- Increased venous return to right atrium
- Bainbridge reflex
- Increased venous flow ejected to the pulmonary circulation, later returning to the left heart
- Increased venous return increases end-diastolic volume→increased stroke volume
- Increased stroke volume increases MABP, thus activating baroreflex
Respiratory sinus arrhitmia
-> One of the peripheral causes: During inspiration, what does thoracoabdominal pump mechanism do?
aiding venous return
What are the interactions between sympathetic and parasympathetic nervous system?
Chemoreflex
Peripheral chemoreceptors are locater at ___ and ___
at the aortic arch and at the bifurcation of the carotid arteries (glomus aorticum and caroticum, aortic and carotid bodies)
What are the primary principles for Central Nervous System Ischemic Response?
Monro-principle and Cushing-reflex
What does Monro-Kellie doctrine (principle) state?
The sum of volumes of brain, cerebrospinal fluid (CSF) and intracerebral blood is constant.
-> An increase in one should cause a reciprocal decrease in either one or both of the remaining two.
Cushing-reflex
-> What is the cushing triad?
Elevated (systolic) blood pressure Bradycardia (slow heartbeat) Tachypnoe (fast breathing
How can Perfusion pressure ensure brain blood flow?
Elevated intracranial pressure
-> Hypoxia in the brainstem
-> Blood pressure elevates (sympathetic activation) to overcome pressure around the brain vasculature
-> Perfusion pressure ensures brain blood flow
What are the possible reasons for brain edema?
- traumatic brain injury
- hyponatraemia (Na3<125 mM)
- brain tumor
- hemorrhage
What are the Hormonal influences on blood pressure for short-term control?
- Epinephrine (norepinephrine)
- Circulating vasoactive substances (e.g. CGRP, SP, VIP, histamine, bradykinin, maybeAch…)
- Angiotensin
What are the Hormonal influences on blood pressure for long-term control?
Influencing blood volume
* Atrial natriuretic peptide (ANP)
* Antidiuretic hormone, a.k.a. (arginine) vasopressin (ADH or AVP)
* Renin-angiotensin- aldosterone system (RAS)
