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Homeostasis
Stage 2 Biology - topic 3: Homeostasis
| Term | Definition |
|---|---|
| tolerance limits | chemical or physical factors that limit the existence, growth, abundance, or distribution of an organism. |
| homeostasis | process by which organisms maintain a relatively stable internal environment |
| nervous system | brain, spinal cord, nerves |
| CNS (Central Nervous System) | brain and spinal cord |
| PNS (peripheral nervous system) | the sensory and motor neurons that connect the CNS to the rest of the body |
| endocrine system | glands secrete hormones that regulate processes such as growth, reproduction, and nutrient use (metabolism) by body cells. |
| sympathetic nervous system | a set of nerves that prepares the body for action in challenging or threatening situations |
| parasympathetic nervous system | a set of nerves that helps the body return to a normal resting state |
| sensory receptors | Specialized cells unique to each sense organ that respond to a particular form of sensory stimulus |
| chemoreceptors | respond to chemicals e.g. spell, taste, osmoreceptors |
| osmoreceptors | respond to the osmolarity of the blood (water homeostasis) |
| thermoreceptors | respond to changes in temperature |
| mechanoreceptors | respond to touch, pressure, vibration, stretch, and itch |
| effector | an organ or cell that acts in response to a stimulus. e.g. muscle or gland |
| stimulus response model | Stimulus to receptor to control centre to effector to response |
| negative feedback | a primary mechanism of homeostasis, whereby a change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation |
| sensory neuron definition | neurons that carry incoming information from the sensory receptors to the brain and spinal cord |
| motor neuron definition | a neuron that sends an impulse to a muscle or gland, causing the muscle or gland to react |
| interneuron definition | a neuron that carries nerve impulses from one neuron to another |
| synapse | the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron |
| synaptic cleft | the narrow gap that separates the presynaptic neuron from the postsynaptic cell. |
| neurotransmitter | chemical messengers that cross the synaptic gaps between neurons |
| direction of nerve impulse | from dendrite to Axon Terminal |
| hormones | chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues |
| endocrine system speed | slow |
| nervous system speed | fast |
| endocrine system duration | long lasting |
| nervous impulse duration | very quick, almost instant |
| target cells | cells that have receptors for a particular hormone |
| hormones chemical structure | proteins, peptides, amino acid derivatives and steroids |
| steroid hormones | can pass through the membrane and bind to a receptor inside the cell |
| non-steroid hormones | cannot pass through membranes, bind to a protein receptor on the membrane |
| insulin production location | beta cells of pancreas |
| glucagon production location | alpha cells of pancreas |
| insulin | a hormone produced by the pancreas or taken as a medication by many diabetics, reduces blood sugar levels |
| glucagon | A protein hormone secreted by pancreatic endocrine cells that raises blood glucose levels; an antagonistic hormone to insulin. |
| insulin target cells | most body cells |
| glucagon target cells | liver cells |
| type 1 diabetes | disorder in which the body cannot produce enough insulin because beta cells have been destroyed |
| TSH (thyroid stimulating hormone) | stimulates secretion of thyroid hormone |
| TSH production location | anterior pituitary gland |
| TRH (thyroxine releasing hormone) | secreted by hypothalamus which triggers pituitary gland to secrete TSH |
| effect of thyroxine on TSH production | thyroxine inhibits TSH and TRH production |
| thyroxine target cells | most body cells |
| thyroxine | Also called thryoid hormone, thyroxine is produced and secreted by cells in the thyroid gland. it targets all cells in the body and increases overall body metabolism. |
| ADH (antidiuretic hormone) | Produced by Posterior lobe of Pituitary Gland. Targets kidneys for water conservation and blood vessels for blood pressure control |
| ADH action on collecting duct | Causes cells to produce more aquaporin to draw more water from the collecting duct back into the blood. |
| osmoregulation | regulation of solute concentrations and water balance |
| nephron | functional unit of the kidney |
| glomerulus | small network of capillaries encased in the upper end of a nephron; where the filtration of blood takes place |
| filtrate in kidneys | squeezed out of the blood vessel in the glomerulus and collected in Bowman's capsule. Pretty much everything from the plasma except proteins which are too big |
| reabsorption in the kidneys | Most of the filtrate (water, glucose, ions) is transported back into the blood except urea, which is waste |
| increased ADH | leads to concentrated urine, due to reabsorption of water, causing increased volume of body fluids |
| decreased ADH | leads to dilute urine and drop in volume of body fluids |
| adrenaline | A hormone released into the bloodstream in response to physical or mental stress |
| adrenaline effects | Increases heart rate, blood flow to muscles and blood sugar level (due to break down of glycogen) |
| negative feedback (body temperature) | When temperature rises above normal, you sweat until your temperature returns to normal - When temperature falls below normal, you shiver until your temperature returns to normal |
Created by:
justineforrest
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