Physiology Flashcards
Podocytes - location
Make up the inner layer of the bowman capsule
Podocytes - definition
Feet like extensions which extend out from the cell body. These extensions wrap around the capillaries and form a barrier of the capillary wall
Podocytes - function
Act as a barrier of the capillary wall
Mesangial cells
Contractile cells which keep the glomerulus clean and keep it together physically
Provides support to capillaries
Vasa recta (peri-tubular capillaries)- definition
Loops of thin walled blood vessels that arise from the efferent arteriole
They look like hairpins as they descend from the cortex -> medulla
Vasa recta capillaries are freely permeable to salt and water. True or false?
True
Vasa recta - location
Run alongside the loop of henle of the juxtamedullary nephrons
GFR
The rate at which protein-free plasma is filtered from the glomeruli -> bowman capsule per unit time
What is the major determinant of GR?
Blood pressure
Extrinsic regulation of GFR
Baroreceptor reflex
Extrinsic control can over-ride intrinsic control. True or false?
True
Increased arterial blood pressure INCREASES/DECREASES the GFR
Increases (due to vasodilation)
Decreased arterial blood pressure INCREASES/DECREASES the GFR?
Decreases (due to vasoconstriction)
What is used clinically to measure plasma renal flow?
Para-amino hippuric acid (PAH)
ADH - function
Stimulates renal tubular cells to increase water reabsorption.
Changes expression of aquaporins at the distal tubule and collecting duct
What are aquaporins?
Water channels
High ADH levels means LOTS/FEW aquaporin expression?
LOTS of
Low ADH levels means LOTS/FEW aquaporin expression?
FEW
ADH has influence over water AND salt reabsorption. True or False?
False
- water reabsorption only
ADH role in the dehydrated state?
Dehydrated -> increased plasma osmolarity -> increased ADH secretion -> lots of aquaporins expressed -> distal tubule more permeable to water reabsorption
In the dehydrated state, patients have a LARGE/SMALL volume of CONCENTRATED/DILUTE urine?
Small
Concentrated
ADH role in the over hydrated state?
Decreased plasma osmolarity -> decreased ADH secretion -> no aquaporins expressed -> distal tubular cells are impermeable to water -> no water reabsorption
In the over-hydrated state, patients have a LARGE/SMALL volume of CONCENTRATED/DILUTE urine?
Large
Dilute
Nicotine STIMULATES/INHIBITS ADH release?
Stimulates
Alcohol STIMULATES/INHIBITS ADH release?
Inhibits
What is the overall function of aldosterone release?
To increase arterial BP
Increased aldosterone means INCREASED/DECREASED Na reabsorption?
Increased
Increased aldosterone means INCREASED/DECREASED K+ reabsorption
Decreased
- therefore, increased K+ secretion in the urine
When is aldosterone secreted? (state 3 reasons)
When there is a rising plasma conc of K+
When there is a fall in Na+ plasma conc
When RAAS is activated
What is Anti Natriuretic Peptide (ANP) ?
Peptide hormone produced by the heart and stored in atrial muscle cells
When is ANP released?
When atrial muscle cells are stretched 9due to circulating plasma volume)
ANP function?
Decrease plasma volume and lowers BP
What are the 2 mechanisms involved in the process of bladder emptying?
Micturation reflex
Voluntary control
Micturation reflex
Involuntary emptying of the bladder by simultaneous contraction and opening of both the internal and external urethral sphincters
Voluntary control - urine excretion
Over-riding the micturition reflex through voluntary control until there is a convenient time and place to excrete urine
There is deliberate tightening of the external urethral sphincter and surrounding diaphragm
