3.7 - Homeostasis And The Kidney Flashcards
Define afferent arteriole
The blood vessel that stems from the renal artery and supplies blood to the nephron. It has a larger diameter than the efferent arteriole and divides into a complex system of capillaries, the glomerulus.
What is the antidiuretic hormone (ADH)?
A hormone made by the hypothalamus and secreted by the posterior pituitary gland in response to a fall in blood water potential. It increases the permeability to water of the DCT and the collecting duct, allowing more water to be reabsorbed into the blood.
What is an ascending limb?
The limb of the loop of Henle that rises into the cortex. It is wider in diameter than the ascending limb and its walls are impermeable to water. Sodium ions and chloride ions are moved out of the ascending limb by active transport.
What is Bowman’s capsule?
The cup-like structure at the start of a nephron that surrounds the glomerulus. The inner layer of the capsule, through which filtration of the blood takes place, is composed of podocytes.
What is a collecting duct?
The final region of the nephron that collects urine from the distal convoluted tubules and empties it into the renal pelvis. Its permeability to water is altered by ADH.
What is the coordinator?
Coordinates information from the receptors and sends instructions to the effectors
Explain what the cortex is
The outer region of the kidney
What is deamination?
The removal of the amino group from the molecule. In the liver, amino acids are deaminated to form ammonia, which is then converted to urea
What is the descending limb?
The limb of the loop of Henle that dips down into the medulla. It is smaller in diameter than the ascending limb. The walls of the descending limb are permeable to water, so the filtrate loses water as it moves on.
What is dialysis?
A medical procedure that artificially filters the blood of patients with kidney failure. It relies on a partially permeable membrane between the patient’s blood and dialysis fluid. There are two types: haemodialysis and peritoneal dialysis
What is a distal convoluted tubule (DCT)?
The twisted region of the nephron between the loop of Henle and the collecting duct that alters the concentration of water and salts reabsorbed. Its permeability to water is altered by ADH
What is an effector?
An organ, tissue, or cell that produces a response to a stimulus
What is an efferent arteriole?
The blood vessel that carries blood away from the glomerulus and sub-divides to form a network of capillaries. Its diameter is smaller than the afferent arteriole, creating a build up of hydrostatic pressure in the glomerulus.
What are endocrine glands?
Glands of the endocrine system that secrete hormones directly into the bloodstream.
What is excretion?
The process of moving metabolic waste from an organism. Excretory products differ between organisms.
What is glomerular filtrate?
The fluid produced by ultrafiltration of the blood into the renal capsule. It contains water, glucose, mineral ions and urea.
What is the glomerulus?
A bundle of capillaries located in the renal capsule which are adapted for the filtration of blood. They later merge to form the efferent arteriole.
Define what homeostasis is
Maintaining a constant internal environment around an optimum despite external change.
What is the loop of Henle?
A loop consisting of a descending limb (dips into the medulla) and ascending limb (rises into the cortex) surrounded by blood capillaries. It creates a low water potential in the medulla, enabling the reabsorption of water. The length of the loop varies depending on the mammal’s environment.
What is a mammalian kidney?
One of a pair of organs in the abdomen that has a role in osmoregulation and nitrogenous excretion
Explain what the medulla is
The inner region of the kidney consisting of renal pyramids made up of nephrons.
Define negative feedback
A feedback mechanism that inhibits the original stimulus and reverses the change in conditions, restoring the optimum point.
Explain what a nephron is
The functional unit of the mammalian kidney
What are osmoreceptors?
Sensory cells located in the hypothalamus that detect the concentration of the blood plasma
What are peritubular capillaries?
Small blood vessels supplied by the efferent arteriole that surround the PCT, loop of Henle and DCT, and enable selective reabsorption.
What is positive feedback?
A feedback mechanism that enhances the original stimulus and increases the change in conditions, deviating the system further from the set point.
What is the posterior pituitary gland?
A gland of the endocrine system that secretes hormones (such as ADH) directly into the bloodstream.
Explain what the proximal convoluted tubule (PCT) is
The twisted portion of the nephron between the renal capsule and the loop of Henle. Its walls consist of epithelial cells that are adapted for the reabsorption of glucose and water in the blood.
What is a receptor?
A specialised structure that detects a specific type of stimulus
Define what renal arteries are
Blood vessels that carry oxygenated blood to the kidneys
What is the renal pelvis?
The central region of the kidney that serves as a funnel for the flow of urine into the ureter
What are renal veins?
Blood vessels that drain the kidneys
Explain what selective reabsorption is
the selective reuptake of useful substances (small molecules and ions) in the proximal convoluted tubule using membrane transport proteins.
Define what set point means
A desired value or range of values determined by a coordinator
What is a transplant?
A medical procedure in which an organ or tissue in an individual is replaced
What is ultrafiltration?
The removal of small molecules, water and ions from the blood in the glomerulus of the kidney at high pressure
What is the vasa recta?
Long, U-shaped blood vessels that run parallel to the loop of Henle and supply the medulla with blood
