Response - Homeostasis: Key Terms Flashcards
Homeostasis
The maintenance of a constant internal environment
Control mechanism
A set of self-regulating stages comprising of: optimum point, receptor, coordinator, effector and feedback loop
Ectotherm
An animal which gains its heat from its external environment
Endotherm
An animal which gain its heat from internal metabolic activities
Vasodilation
Widening the diameter of arterioles near the surface of the skin, so that warm blood passes close to its surface via capillaries
Vasoconstriction
Narrowing the diameter of arterioles near the surface of the skin, so that less blood volume passes close to its surface via capillaries, retaining heat
Hypothalmus
Part of the brain next to the pituitary gland; the control centre for the ANS
Second messenger model
The way a non-lipid soluble hormone acts on a cell, by triggering production of an intermediary ‘second’ messenger (by activating adenyl cyclase?)
Type 1 diabetes
Insulin dependent, due to body being unable to produce insulin
Type 2 diabetes
Insulin independent, due to glycoprotein receptors on body cells losing responsiveness to insulin
Gluconeogenesis
Conversion of non-carbohydrates into glucose in the liver
Glycogenolysis
Breakdown of glycogen to glucose in the liver
Glycogenesis
Conversion of glucose into glycogen in the liver
Negative feedback
When the feedback causes the corrective measures to be turned off so returns the system to its original level
Positive feedback
When the feedback causes the corrective measures to be turned on so the system deviates even further from its original level
Osmoregulation
The homeostatic control of the water potential of the blood
Nephron
The functional unit of the kdiney
Fibrous capsule
An outer membrane which protects the kidney
Cortex
A lighter coloured outer region made up of renal (Bowman’s) capsules, convoluted tubules and blood vessels
Medulla
A darker coloured inner region made up of loops of Henle, collecting ducts and blood vessels
Renal pelvis
A funnel-shaped cavity that collects urine into the ureter
Ureter
A tube that carries urine to the bladder
Renal artery
Supplies the kidney with blood from the heart via the aorta
Renal vein
Returns blood to the heart via the vena cava
Renal (Bowman’s) capsule
The closed end at the start of a nephron
Proximal convoluted tubule
A series of loops surrounded by blood capillaries which are adapted to reabsorb substance into the blood
Loop of Henle
A long, hairpin loop that extends from the cortex into the medulla of the kidney and back again
Descending limb of loop of Henle
Narrow, thin walls that are highly permeable to water. The filtrate progressively loses water by osmosis as it moves down the limb
Ascending limb of loop of Henle
Wider, with thick walls that are impermeable to water. Sodium ions are actively transported out of this limb which creates a lower water potential in the region of the medulla between the two limbs
Distal convoluted tubule
A series of loops surrounded by blood capillaries
Collecting duct
A tube into which a number of distal convoluted tubules from a number of nephrons empty
Afferent arteriole
A tiny vessel that ultimately arises from the renal artery and supplies the nephron with blood
Glomerulus
A many-branched knot of capillaries from which fluid is forced out of the blood
Efferent arteriole
A tiny vessel that leaves the renal capsule
Blood capillaries
A concentrated network of capillaries that surround the proximal convoluted tubule, the loop of Henle and the distal convoluted tubule and from where they reabsorb mineral salts, glucose and water
Ultrafiltration
Filtration assisted by blood pressure
Reabsorption of water
Process by which all of the glucose and most other valuable molecules are reabsorbed as well as water in the proximal convoluted tubule
Counter-current multiplier
When two liquids flow in opposite directions past one another, the exchange of substance between them is greater than if they flow in the same direction next to each other
Osmoreceptors
Cells in the hypothalmus of the brain that detect a change in water potential
Antidiuretic hormone (ADH)
A hormone produced by the pituitary gland when a decrease in water potential is detected, which makes the walls f the distal convoluted tubule and collecting duct more permeable to water
