Lecture 39 Flashcards
What are the slow and fast methods which lead to diuresis? What does this mean about isotonic losses/gains compared to hypo/hyper tonic?
Vasopressin acts relatively fast with change to osmolarity, isotonic drinks have the same osmolarity as our plasma, this means diuresis doesn’t act until much later (8-10 hours). This shows us the fast system is based on osmolarity and a slow system acts against volume. vomiting is another example of this as you lose both water and salt, this means osmolarity stays the same despite lower circulating volume (only ECF changes for isotonic volume changes). This problem is corrected via the slow process of sodium excretion/retention.
What are some problems hypo/hypervoleamia can lead to?
Hypo-volaemia (low volume) leads to lowered central nervous system function, increase in pulse, lowered urination. hypervolaemia can lead to hypertension and damage to the heart.
What receptors sense ECF volume changes and where are they found?
Changes in ECF volume are sensed by pressure receptors, There are high pressure baroreceptors in the Aortic arch and carotid sinus, they signal to the brainstem cardiovascular centres to increase or decrease renal nerve activity (sympathetic), possibly ADH, low-pressure baroreceptors in the vena cava, right atrium and pulmonary blood vessels, release atrial natriuretic peptide (promotes loss of sodium in the urine to promote water excretion). Lastly is the intra-renal sensors, in the afferent artiole changes in blood pressure change renin secretion, in the macula densa flow rate is sensed via the sodium concentration, also alters renin secretion.
What happens to the information from the receptors for renal handling of Na+
The information about circulating volume from all 3 sensory systems is integrates to regulate the renal handling of Na+ (and hence water). When circulating volume and renal flow are sensed as high Na+ excretion is increased (hence water), this decreases the volume and vice versa.
What are the methods for increasing blood volume?
Renin-angiotensin system (renin enzyme secreted by JGA cleaves angiotensinogen into angiotensin I (in the , this is converted to angiotensin II which acts as a potent vasoconstrictor, stimulates tubular Na+ reabsorption, lowers filtered sodium load stimulates aldosterone release, causes thirst and ADH release from hypothalamus. Also increases aldosterone levels in plasma) Stimuli for this is reduced renal perfusion in afferent arteriole, decresed delivery of NaCl to macula densa and renal sympathetic nerves (activation by baroreceptors).
Aldosterone is a steroid hormone secreted from the adrenal gland stimulated by K+ levels and angiotensin II. Acts on the distal tubule and collecting duct to increase reabsorption of Na+ and secretion of K+.
What are the methods by the kidneys to lower blood volume?
Atrial natriuretic peptide ( secreted by atria in response to increased volume (this lowers plasma aldosterone and increases GFR, increases filtered load of sodium and lowers tubular reabsorption of sodium and renin secretion. These will increase sodium excretion).
