The Urinary System - Part 1 (week 10) Flashcards
state 4 methods of treating hypertension (high blood pressure)
- diuretics
- beta-adrenergic receptor blockers
- calcium ion channel blockers
- angiotensin-converting enzyme (ACE) inhibitors
explain how diuretics can help reduce blood pressure / treat hypertension
diuretics increase the excretion of Na+ and H2O, decreasing cardiac output with no change in peripheral resistance
explain how beta adrenergic receptor blockers can help reduce blood pressure / treat hypertension
reduce cardiac output by blocking the binding site for norepinephrine / epinephrine
explain how calcium ion channel blockers can help reduce blood pressure / treat hypertension
reduce entry of calcium ions (Ca2+) into vascular muscle cells = weaker contractions = lower peripheral resistance
explain how angiotensin-converting enzyme (ACE) inhibitors can help reduce blood pressure / treat hypertension
the final step in the formation of angiotensin 2 (a vasoconstrictor) is mediated by an ACE. blocking this enzyme causes vasodilation, lowering blood pressure
explain the role of aldosterone of in the renin-angiotensin system
aldosterone is a slow acting steroid hormone that stimulates Na+ reabsorption by the kidney tubules
explain the role of vasopressin (ADH) in the renin-angiotensin system
rapid acting peptide hormone, produced by the hypothalamus and secreted by the posterior pituitary gland, which stimulates water reabsorption
explain the role of angiotensin-converting enzymes (ACE) in the renin-angiotensin system
they are found on endothelial cells and mediate the final step of angiotensin 2 production (a vasoconstrictor)
explain the role of the intra-renal baroreceptors in the renin-angiotensin system
intra-renal baroreceptors detect changes in stretching which is proportional to changes in blood volume which stimulates a change in the production of renin
what do cardiac cells produce which is used in the renin-angiotensin system
atrial natriuretic peptide (ANP)
state the 3 functions of atrial natriuretic peptide (ANP) in the renin-angiotensin system
- inhibits Na+ reabsorption by the kidney tubule cells
- acts on renal blood vessels to increase filtration rate causing Na+ excretion
- inhibits the action of aldosterone
state what it is meant by the key term - Renin
Renin is an enzyme produced by the juxtaglomerular cells, secreted, and stored in the kidneys, which promotes the production of the hormone Angiotensin
state what occurs within hours of blood loss (4 points)
- compensatory movement of interstitial fluid into the capillaries to increase plasma volume (redistribution)
- an increase in thirst (slower)
- a decrease in Na+ and H2O secretion (slower)
- mediated by hormones (renin, angiotensin, aldosterone) and kidney function
state what occurs within days of blood loss (2 things)
- erythropoiesis
2. haematopoiesis
what is the normal human body core resting temperature? and what is the normal range?
- 36.5 - 37.5 degrees
2. 35 - 39 degrees
what proportion of energy from food is lost from the body as heat?
2/3 of all energy liberated from food is lost as heat
what is the value of heat produced by the average body at rest?
1.25 - 1.5 kcal/min
what is the value of heat produced by the average body during exercise?
15 - 20 kcal/min
state the 5 sources of heat gain
- solar radiation
- thermal radiation
- convection
- metabolic heat production
- conduction
state the 5 sources of heat loss
- radiation
- convection
- respiratory evaporation
- conduction
- sweat evaporation
state the 4 values of heat loss at rest, in ambient environmental conditions
(i.e. radiation, convective air currents, conduction and evaporation)
- radiation - 60%
- convective air currents - 12%
- conduction (eg - feet to floor) - 3%
- evaporation (lungs + skin) - 25%
what percentage of heat loss can be lost from evaporation from the skin during exercise?
80% of heat loss can occur via evaporation from the skin during exercise (dependent on humidity)
state the kidneys role in water and electrolyte balance
the kidney cannot restore a body water deficit, but can help to preserve body water and electrolytes during periods of increased loss
state what it is meant by the key term - Renal
the adjective ‘Renal’ means ‘pertaining to the kidney’. the kidneys process the plasma portion of the blood by removing substances from it, and in some cases, adding substances to it
state 3 renal functions
- remove waste products from the body
- remove drugs from the body
- balance the body’s fluids
- involved in gluconeogenesis
- release hormones that regulate blood pressure
- control the production of red blood cells
- produce an active form of vitamin D that promotes strong, healthy bones
state the 4 components of the urinary system
- kidney
- ureter
- bladder
- urethra
state 4 facts about the renal corpuscle
- forms a filtrate from the blood which is free from proteins and cells
- filtrate leaves the corpuscle and enters the proximal tubule
- as it flows through the PT and the DCT, substrates are added/removed
- remainder fluid combines in the collecting ducts and exits the kidneys as urine
state the flow of liquid through the nephron (11 steps)
- glomerulus
- Bowman’s space in Bowman’s capsule
- proximal convoluted tubule (PCT)
- proximal straight tubule (PST)
- descending loop of Henle
- thin loop of ascending loop of Henle
- thick loop of ascending loop of Henle
- distal convoluted tubule
- cortical collecting duct
- medullary collecting duct
- renal pelvis
what is the difference between the afferent and efferent arterioles at the Bowman’s capsule
- afferent = brings blood in
2. efferent = takes blood out
state what it is meant by the key term - podocyte
a podocyte is the visceral layer of the Bowman’s capsule that surrounds the glomerular capillaries
state 2 structural facts about podocytes
- have ‘filtration slits’ which enable the transfer of liquid
- large number of extensions that help with filtration
state what it is meant by the key term - fenestrae
fenestrae are small pores on the internal surface of the glomerular capillaries - allow soluble substances to exit
blood in the glomerular is separated from fluid in the Bowman’s space by a filtration barrier consisting of 3 layers. state these 3 layers
- single cell lining of the capillary endothelium
- non-cellular protein-rich layer of basement membrane
- single cell lining of the Bowman’s capsule
uniquely, the renal circulation has 2 sets of capillaries. state the names of these 2 types
- glomerular capillaries
2. peritubular capillaries
state the function of the glomerular capillaries
glomerular capillaries are specialised for filtration
state the 2 functions of the peritubular capillaries
- supply the nephron tubules with their own blood supply
2. form the veins where blood vessels leave the kidney
state the names of the two types of nephrons
- Juxtamedullary nephrons
2. Cortical nephrons
state 4 facts about juxtamedullary nephrons
- 15% of all kidney nephrons
- renal corpuscle close to the cortical-medullary junction
- loop of Henle plunges deep into the medullar
- generate osmotic gradient for water reabsorption
state 3 facts about cortical nephrons
- 85% of kidney nephrons
- corpuscle located in the outer cortex
- loop of Henle does not plunge deep into the medullar
state the difference in main functions of juxtamedullary and cortical nephrons
- juxtamedullary - loops of Henle dip deeper into the inner medulla and papilla, and are vital in the concentration of urine
- cortical - have larger glomeruli, and thus have higher glomerular filtration rates (GFR).
state the names of the two sub-units which make up the juxtaglomerular apparatus
- macula densa
2. juxtaglomerular cells (functional)
state 2 facts about the macula densa (part of the juxtaglomerular apparatus)
- part of the ascending loop of henle
2. contain sensors which detect changes in blood composition
state 3 facts about the juxtaglomerular cells (functional part of the juxtaglomerular apparatus)
- secrete Renin
- influence the formation of angiotensin 2
- control blood pressure (vasoconstriction, Na+ and H2O retention)
there are 3 distinct inputs to juxtaglomerular cells that increase Renin secretion. state these 3 inputs
- renal sympathetic nerves
- intra-renal baroreceptors
- macula densa
decreased plasma volume = (3 things) and what is the consequence of these 3 things?
- increased activity of sympathetic nerves
- decreased arterial pressure
- decreased GFR = decreased NaCl delivery to macula densa
= renal juxtaglomerular cells increase renal secretion
state what it is meant by the key term - isotonic solutions
have the same concentration of non-penetrating solutes as extracellular fluid
state what it is meant by the key term - hypotonic solutions
have a lower concentration of non-penetrating solutes compared to normal extracellular fluid (fluid rushes into the cell to dilute intracellular solutes)
state what it is meant by the key term - hypertonic solutions
have a higher concentration of non-penetrating solutes than normal extracellular fluid (water rushes out of the cell to dilute extracellular solutes)
state the 8 steps of osmotic regulation
- excess H2O ingested
- decreased fluid osmolarity (inc^ H2O conc^)
- dec^ firing by hypothalamic osmoreceptors
- posterior pituitary dec^ vasopressin secretion
- dec^ plasma vasopressin
- collecting ducts dec^ tubular permeability to H2O
- dec^ H2O reabsorption
- inc^ H2O excretion
state the 7 steps of volume regulation (from low volumes of water measured)
- dec^ plasma volume
- dec^ venous, arterial and atrial pressures
- posterior pituitary inc^ vasopressin secretion
- inc^ plasma vasopressin
- collecting ducts inc^ tubular permeability to H2O
- inc^ H2O reabsorption
- dec^ H2O excretion
state 2 facts about filtration (basic renal process)
- urine filtration begins with the filtration of plasma from the glomerular capillaries into the Bowman’s space (glomerular filtration produces glomerular filtrate)
- the filtrate is cell free and, except for large proteins, contains all the substrates in virtually the same concentrations as in plasma (ultra filtrate)
state the force which favours filtration
glomerular capillary blood pressure (P-GC)
state the 2 forces which oppose filtration
- fluid pressure in Bowman’s space (P-BS)
2. osmotic force due to proteins in the plasma (pi-GC)
state the average daily intakes of water from liquid and food and what is metabolically processed
- liquid = 1400 mL
- food = 1100 mL
- metabolically processed = 350 mL
total = 2850 mL
state the average daily water loss from 4 different sources
- insensible loss = 900 mL
- sweat = 50 mL
- feces = 100 mL
- urine = 1800 mL
total = 2850 mL
state 3 facts about tubular reabsorption - plasma components
- the filtered loads are very high (eg - water)
- reabsorption of waste products in incomplete (eg - urea)
- reabsorption of useful products is complete (eg - water and salts)
the mechanisms of sodium and water reabsorption can be summarised using what 2 points?
- Na+ reabsorption is an active process occurring in all tubular lumen (except for the descending limb of the loop of Henle)
- water reabsorption is by osmosis and is dependent upon Na+ reabsorption
state what it is meant by the key term - insensible loss
insensible fluid loss is the amount of body fluid lost daily that is not easily measured, from the respiratory system, skin, and water in the excreted stool
