central control of the CVS Flashcards
what is a reflex
- response to a particular stimulus
- specific
- IV
- unpremeditated
list some receptors in the periphery
- aortic arch BR
- carotid sinus BR
- all the afferents synapse at the NTS within the medulla
- convergence of cardiopulmonary afferents from periphery
Describe properties of the vagus PNS
- leaves medulla and doesn’t enter the SC
- long pre-ganglionic N
- cell bodies in medulla
- short post ganglionic (cell bodies near heart)
describe the properties of the SNS
- descending pathways use the SC (sympathetic trunk)
- cell bodies in the SC
- short pre-ganglionic N
- cell bodies at different levels of trunk
- synapse with post-G ( paraV ganglia)
- longer post G leaves the SC -> SAN/AVN/ myocytes
what do aortic arch baroreceptors do?
- measure degree of stretch
- afferents sent via V nerve to NTS (bare nerve endings)
- measure pressure by sensing stretch of vessel
- found in the aortic arch
what do the carotid sinus receptors do?
- found within the carotid arteries
- monitor BP flowing to cerebral circulation
- Carotid sinus nerve feeds into glossoP
both are stretch mediated
why have tonic activity of the receptor?
- allows measurement of BP in both directions (up/down)
- BP drops–> R unloading-> less afferent activity sent to NTS
- graded response proportional to degree of stretch
what does the nucleus ambiguous contain?
- cell bodies of the vagal nerve
- efferents from vagal nerve
maximum receptor sensitivity occurs around what ?
- around what is considered normal BP for that person
- elderly –> ageing increases stiffness of arteries and therefore R sensitivity declines
what does the RVLM contain?
- SNS efferents
- cell bodies of postG neurones
explain the neuronal mechanisms in response to an increased BP?
Ex– afferent –> NTS–> Ex–> NA –> increased vagal outflow –> reduced HR
Ex– afferent–> NTS –> excites inhib N –> RVLM–> reduced cardiac SNS outflow –> reduced contractility
Ex–> afferent –> NTS –> Ex inhib N–> RVLM–> reduced vasomotor SNS outflow –> reduced VR (VD) and reduced TPR
what happens if the high BP is maintained?
- the reflex will reset
- point moves to a higher pressure to retain responsiveness of reflex
what are cardiopulmonary receptors ?
- stretch receptors
- Nerve endings
- atria/ PA/V
- sense volume of CVS
- stimulated by decrease in blood volume
- Low CVP
- vagal afferents with NTS–> release of ADH by posterior PG–> potent VC
- increased water reabsorption in CD
- increased BV and increased TPR
explain how there is integration at higher centres?
- hypothalamus–> can override the reflex
- stress response (hypoT)–> allows BP to increasingly rise in our favour
- central command in exercise emotions–> motor cortex–> imagine exercise and get increased CVS responses
what does the RVLM contain?
- the cell bodies of SNS efferents
