bio ch 8

homeostasis

the maintenance of stable internal conditions in a system

gas levels

oxygen is constantly being used in cellular respiration and carbon dioxide is being produced, cells must have a way of gaining oxygen while excreting co2, without enough oxygen ATP cannot be produced, too much CO2 and the pH of the cell will get too low

osmolarity

the balance of water and solutes must be maintained due to osmosis, if extracellular fluids are hypotonic low in solute concentration water will enter the cell and cause it to burst lysis, if extracellular fluids are hypertonic high in solute concentration water will leave the cell and cause it to dry out crenation

temperature

cell structures and rates of crucial reactions can be affected by changes in temperature, if temp too low cell reactions may have a rate too low to be effective, if temps too high chemical structures like tertiary structure of proteins get disrupted and become nonfunctional

sensor, integrator, effector

3 structures necessary to respond to homeostatic disruption

sensor

detect change in internal or external environment, receptor, ex cells in root act as sensor, ex hypothalamus detects changes in body temp

integrator

initiate a response to stimulus, cell tissue or organ, ex plant root cells release hormone that travels to leaves, ex message to muscles or sweat glands

effector

an organ, cell, tissue that gets information from integrating center and causes a change to help homeostasis, ex stomata close, ex muscles shiver or sweat glands

hormones and nervous system

cells working together for homeostasis

negative feedback

when a stimulus produces results and the result inhibits further stimulation, ex thermoregulation warming the body stops when at good temp

positive feedback

when a stimulus produces a results and the result causes further stimulation triggering an event, ex labor, when head pushes oxytocin is released to contract muscles more

homeostatic mechanisms

can reflect common ancestor if similar or evolution if differing

molecular and cellular disruptions

toxins enter, detected by cells tissues, organs, to expel, physiological and immunological responses

other species, human impact, natural events, limitation of water

disruption of ecosystem’s homeostasis