Control of Blood Pressure and Blood Volume Flashcards
What is the reflex arch for controlling the heart and blood vessels?
Reflex responds to sensory neurones that enter the CNS via afferent nerves. Exiting the CNS via efferent nerves or hormones. Effector neurones will affect the heart and blood vessels.
Where does the pre-ganglionic sympathetic neurones innervate?
T1-L2
What are efferent cortical influences?
Emotion,
Volition (power of using ones will)
Efferent complex reflex patterns
Exercise Feeding/satiety (feeling or state of being satisfied) Alerting/defence Thermoregulation Reproduction
Which two hormones effect the kidneys?
Vasopresin (ADH) and Renin-angiotensin
Regulate blood volume and therefore blood pressure
What are baroreceptors?
Stretch receptors
Where are baroreceptors found?
In the neck, runs up into the brain. Found in the aortic arch and carotid sinus.
Baroreceptors found in the carotid sinus are connected to the sinus nerve into the IX glossopharyngeal nerve.
Baroreceptors found in the aortic arch are connected to the aortic nerve into the X vagus nerve which enter the CNS via the medulla.
When do baroreceptors activity affect
Baroreceptors are firing afferent activity to the medulla even at normal arterial pressure.
What does more stretch mean for ABP and baroreceptor afferent activity?
More stretch increase ABP increases baroreceptor afferent activity.
What does less stretch mean for ABP and baroreceptor afferent activity?
Less stretch decreases ABP decreases baroreceptor afferent activity.
What is the effect on sympathetic activity when there is an decrease in ABP
A decrease in ABP decreases baroreceptor afferent activity. Sympathetic activity increases meaning more noradrenaline is released to act on alpha receptors. Arterioles constrict increasing TPR, a decrease in hydrostatic pressure (increasing filtration into capillaries) in addition to constriction of venous vessel there is an increase in EDV. Noradrenaline is also acting on B-receptors causing constriction decreasing ESV. An increase in EDV and a decrease in ESV causes an increase in SV therefore an increase in CO.
ABP = CO x TPR
What is the effect of parasympathetic activity when there is an increase in ABP
A decrease in ABP decreases baroreceptor activity. A decrease in ACh on muscarinic receptors decreases parasympathetic activity to allow an increase in heart rate to increase CO.
ABP = CO x TPR
If there is a large decrease in ABP what reflex is used?
Reflex renal vasocontriction
What mechanism helps maintain cerebral blood flow (CBF)?
Myogenic dilation (60-140 mmHg)
What mechanism achieves functional anaemia and what is this?
Functional anaemia is an increase in blood flow when the tissue is active. Coronary circulation shows functional anaemia as a response to increase cardiac work (reflex, increase HR, increase contractility). More work, more metabolites are released which causes functional hyperaemia.