Carotid sinus receptors:
spray type nerve endings – in the adventitia of the carotid bifurcation
and the internal carotid artery.
Afferent neurons: Innervation – through the branch of n. IX. – Hering´s nerve.
Center of the carotid sinus reflex – tractus solitarius in the medulla,
Efferent neurons: n.X and parasympathetic + sympathetic nerves to vessels.
Effectors: Heart, smooth muscles in the vessels wall.
Stimulation: The baroreceptors are stimulated by distension of the vessels wall – stretch
receptors.
Aortic arch receptors:
in the wall of the aorta.
Affferent pathway:
Innervation – through the vagus)
Center, efferent pathway, effectors and effects – the same as in CSR
Left ventricular receptors:
Afferent and efferent pathways: n. vagus.
Activity and effects of the HP baroreceptors
Normal BP – r. discharge at a slow rate
Increased BP – the discharge rate increases
Decreased BP - - “ - declines
Effects:
BP increase (hypertension): The increased discharge rate evokes rising activity in
cardioinhibitory center and depressoric area of the vasomotor center – bradycardia,
vasodilatation – a fall in BP to the normal level
BP decrease (hypotension): The decreased discharge ... vice versa. Normalization of the BP in
different situations.
Baroreceptor Testing
- Pressure on the SC region – unconstant stimulus
Syndrome of the hypersensitive SC (sy HSC)
- Carotid Clamping – proximal or distal to the CS - on experimental
animals
- Cutting the CS nerves - on experiments/ treatment sy HSC
- Application of the drugs eliciting an increase in BP (NE,dopamine)
- Different maneuvers (orthostasis, klinostasis, Valsalva ...)
Orthostatic Reflex
When a person stands – venous return decreases due to hydrostatic pressure of the blood.
A decrease in CO and systemic BP occurs.
Falling BP at the baroreceptors elicits an immediate reflex, with strong sympathetic activity –
vasoconstriction, increase in BP diast., tachycardia.
The aim
– to maintain an adequate perfusion of organs.