Neural Control of Blood Pressure Flashcards
which two systems regulate blood pressue?
which is fast which is slow?
- *neuronal system**
- moment to moment regulation (for example when you go from lying down to a standing posture it automatically regulates blood flow to the legs)
- vital for the maintenance of blood pressure after haemorrhage.
- *hormonal system**
- renini-angiotension-aldosterone system
- much slower
why do we need a BP control system? (i.e. what happens if have hypotension & hypertension)
- *BP too low = hypotension:**
- not enough blood & oxygen can reach our end organs
- chronic fatigue and an inability to exercise
- *BP too high = hypertension:**
- arteries can become overstretched
- this can cause aneurysms (due to weakened arterial walls)
- aneursyms can burst & cause massive internal bleeding
what type of feedback (+ / - ) is neuronal control of BP ?
which are receptors detect change in BP?
negative feedback xxxxx
change detected by baroreceptors
where are baroreceptors located?
- *- carotid sinus** in the internal carotid artery (just above the bifurcation of carotid arteries)
- *- aortic sinus**
stretch in the carotid sinus receptors is proportional to blood pressure
what happens when an increase in pressure is detected in baroreceptors?
what is signal pathway after barcoreceptor detect change?
- increase in arterial pressure = stretches the sinus wall
- sensory nerve fibres embedded in the wall also stretched
- The stretch opens mechanically sensitive sodium and calcium channels in the membrane and triggers action potentials in the sensory nerve fibres
- The baroreceptors nerve fibres travel up to the brain in the vagus (X) (from the aortic nerves) and glossopharyngeal (IX) cranial nerves (from the carotid sinus nerves)
describe afferent innervation pathways for baroreceptors
baroreceptors nerve fibres travel up to the brain:
baroreceptors in aortic sinus –> vagus nerve (X) –> solitary tract (NTS) in the medulla oblongata,
baroreceptors in carotid sinus nerves –> sinus nerve –> glossopharyngeal (IX) nerves –> solitary tract (NTS) in the medulla oblongata,
carotid sinus nerve can travel in either glassopharnygeal nerves ( CN IX) or the vagus (CN X) or both
Recent research has indicated that the mechanically sensitive channels in the baroreceptor nerves are the X and/or Y type channels
Recent research has indicated that the mechanically sensitive channels in the baroreceptor nerves are the PIEZO1 and/or PIEZO2 type channels
where do u find cell bodies of carotid sinus afferent fibres?
The cell bodies of the carotid sinus afferents are in the jugular and nodose ganglia
The Nucleus of the solitary tract (NTS) lies near the …. surface of the medulla?
which other parts of medulla does NTS connect to? (2)
The Nucleus of the solitary tract (NTS) lies near the dorsal surface of the medulla
(The NTS can be regarded as an integrating centre for visceral afferent sfrom _mouth, throat and neck)_
NTS connects to the vasomotor centre in the rostral medulla and the nucleus ambiguus in the nearby lateral medulla.
which other parts of medulla does NTS connect to?
NTS connects to the vasomotor centre in the rostral medulla
the nucleus ambiguus in the nearby lateral medulla
explain mechansim of efferent nerve fibres what happens when BP is too high and when too low :)
- *If blood pressure is too low:**
- NTS activates the vasomotor centre which stimulates sympathetic outflow to the heart via the reticulospinal tract
- These activate post-ganglionic sympathetic fibres which release noradrenaline on arteriolar blood vessels
- Noradrenaline acting on alpha 1 adrenoreceptors make arterial smooth muscle contract
- *If blood pressure is too high**
- the NTS activates the nucleus ambiguus which stimulates parasympathetic outflow to the heart via the **vagus nerve
- acts at thesinoatrial node,inhibiting muscarinic receptors to causehyperpolarisationof the cardiac muscle cells andtherefore slow the heart dow**n
AND
- the vasomotor centre is inhibited, which reduces sympathetic outflow
- relaxation of arterioles, lowered heart rate and reduction of TPR.
- This lowers blood pressure back to the desired level.
where do u find the Lateral reticulospinal tract?
If the input from the baroreceptors (i.e. rate of action potential firing) is too low, the vasomotor centre activates the ?? nervous system . The ?? outflow results in a ?? of peripheral arterioles that ?? ??. A rise in ?? increases blood pressure (assuming cardiac output, the outflow in litres/min from the heart, stays constant)
If the input from the baroreceptors (i.e. rate of action potential firing) is too low, the vasomotor centre activates the sympathetic nervous system . The sympathetic outflow results in a constriction of peripheral arterioles that raises total peripheral resistance (TPR). A rise in total peripheral resistance increases blood pressure (assuming cardiac output, the outflow in litres/min from the heart, stays constant)
* what are the three consequences of increased sympathetic outflow after BP being low? *
if BP is too low: sympathetic NS activated / get increased sympathetic outflow, which causes:
- constriction of peripheral arterioles: raises total peripheral resistance (which increases BP)
- increase in HR, which raises cardiac output
- constriction of veins, which raises venous return and preload (and thus raised stroke volume & C.O)
