Homeostasis and the Kidney Flashcards
What is homeostasis?
The maintenance of a state of dynamic equilibrium in the body despite fluctuations in internal and external conditions.
Why is homeostasis important?
To ensure optimum conditions for enzymes and cellular processes in the body.
Define negative feedback.
Self-regulatory mechanisms return the internal environment to the optimum when there is a fluctuation.
Define positive feedback.
A fluctuation which triggers changes that result in an even greater deviation from the normal level.
What is the set point?
A desired value or range of values determined by a coordinator.
Describe receptors and effectors.
- Receptors = specialised cells located in sense organs that detect a specific stimulus.
- Effectors = muscles or glands which enable a physical response to a stimulus.
Describe the role of the coordinatior.
Coordinates info from the receptors and sends instructions to the effectors.
State the components of a negative feedback system.
- Set point
- Receptors
- Coordinator
- Effectors
What is the mammalian kidney?
One of a pair of organs in the abdomen that has a role in osmoregulation and nitrogenous excretion.
What is osmoregulation?
The regulation of the water potential of body fluids (e.g. blood, tissue fluid, lymph) by the kidney.
What is osmoregulation important?
- Prevents cells bursting or shrinking when water enters or leaves by osmosis.
- Cellular reactions occur in aqueous solution and so water levels affect concentrations and the rate of reactions in cells.
Define excretion.
The process of removing metabolic waste from an organism.
Describe how excess amino acids are excreted.
- Amino acids deaminated in the liver (removal of amino group) to form ammonia.
- Ammonia converted to urea (less toxic).
- Urea transported into the blood plasma and eliminated by the kidneys.
What is the function of the renal artery?
Supplies blood to the kidneys.
What is the function of the renal vein?
Drains blood from the kidneys.
What is the function of the ureter?
Takes urine to the bladder from the kidneys.
What is the function of the urethra?
Releases urine from the bladder, out of the body.
Describe the gross structure of a mammalian kidney?
- Fibrous capsule (protects kidney).
- Cortex (outer region consists of Bowman’s capsules, convoluted tubules, blood vessels).
- Renal pyramids (cone-shaped subdivisions).
- Renal pelvis (funnel-shaped dilated section of ureter).
- Medulla (inner region consists of collecting ducts, loops of Henle, blood vessels).
What is a nephron?
The functional unit of the mammalian kidney.
Describe the blood vessels associated with a nephron.
- Wide afferent arteriole from renal artery enters renal capsule and forms the glomerulus, a branched knot of capillaries which combine to form narrow efferent arteriole.
- Efferent arteriole branches to form capillary network that surrounds.
Define ultrafiltration.
The removal of smaller molecules, water and ions from the blood in the glomerulus of the kidney at high pressure.
Describe the process of ultrafiltration.
- Occurs in Bowman’s capsule.
- High hydrostatic pressure in glomerulus forces small molecules (e.g. urea, water, glucose, ions) out of capillary fenestrations against osmotic gradient.
- Basement membrane acts as a filter. Blood cells and large molecules (e.g. proteins) remain in capillary.
Why is there a build-up of pressure in the glomerulus?
Afferent arteriole leading into the glomerulus is wider than the efferent arteriole taking blood from the glomerulus.
How are cells of the Bowman’s capsule adapted for ultrafiltration?
- Fenestrations between epithelial cells of capillaries.
- Fluid can pass between and under folded membrane of podocytes.
