M8IQ1- Homeostasis - Coggle Diagram
- detecting changes from the stable state; made possibly by the presence of receptors in living organisms.
- receptors in animals consist of neurone cells that detect stimuli (any information that causes a response).
- the nervous system has receptors in the sense organs to detect changes in the external environment.
- counteracting changes from the stable state; brought about in living organisms by effectors.
- in mammals, effectors are usually muscles or glands and in plants hormones such as auxins and cytokinins.
- humans can maintain homeostasis by:
- coping with pathogens
- repairing injuries
- maintaining nutrient supply
What is it?
- the process by which organisms maintain a relatively stable environment. to maintain homeostasis, organisms need to detect stimuli from both their internal environment and from the external environment.
- conditions within the body must be maintained at a constant level in order to achieve optimal metabolic efficiency.
- enzymes, responsible for controlling all metabolic activities, within the cell, will only operate within a limited range of temp and acidity.
- any change reinforces itself by causing more change in the same direction; eg, a fire growing larger.
- always causes a system to grow out of control, or shrink away into nothing- never stability.
- the monitoring reinforces and amplifies the situation, causing more of the same situation to take place.
- any change in a system causes a shift in the opposite direction.
- causes a system to maintain stability.
- eg: body temperature too low (stimulus), receptor notifies hypothalamus > start shivering (response), get warmer.
- receptor: measures and monitors conditions
- control centre: decides how to respond
- effectors: carry out commands of the control centre and make necessary adjustments to the system. generally muscles or glands
Body Temp in Humans
- receptor cells in the hypothalamus detect temperature changes from either nervous impulses sent from 'thermoreceptor' cells in the skin or changes in internal blood temperature.
- higher temps: vasodilation (blood vessels dilate and move closer to the skin's surface, allowing heat to escape), sweating and panting. lowers overall blood temp.
- lower temps: vasoconstriction (blood vessels constrict, reducing heat loss), contraction of hair erector muscles to allow hair, fur, or feathers to stand on end. warms blood temp.
Glucose in Humans
- 1. blood glucose level rises
- beta cells in pancreas release insulin into the blood > liver takes up glucose and store it as glycogen/body cells take up glucose > blood glucose level declines.
- 2. blood glucose level falls
- alpha cells in pancreas release glucagon > liver breaks down glycogen and releases glucose > blood glucose level rises.
- both result in homeostasis (glucose levels 90mg/100ml)
Water Balance in Humans
- life cannot exist without water. all living cells are about 75% water.
- water is the solvent of life
- water is involved in life chemistry
- water is involved in diffusion and osmosis
- water is involved in temperature regulation
- water supports and cushions cells and organs.
- if the balance of water and solutes in cells is not maintained at an optimal concentration, water may move into cells causing them to burst (lysis- animal cells) or too much water may move out, causing cells to shrink (plasmolysis) and the cytoplasm to become too concentrated for normal cell functioning.
- the osmotic pressure of living tissue can also affect the pH of cells; too little water leads to an increase in the concentration of solutes like carbon dioxide, lowering pH.
- both osmotic pressure and pH must be maintained within a range so that enzymes can function under optimal conditions to allow effective metabolism
Temp Control in Endotherms
- all endotherms rely on bodily insulation; fur, feathers, blubber, (structural adaptations) etc, humans mostly rely on technology (behavioural adaptations)
- in hot environments, large ears with good blood supply, panting, and licking forearms help cool bodies.
- in cool environments, thick fur coats or layers of fat help warm bodies.
Role of the Nervous System
- receptors: in sense organs collect information about the external environment. other receptors within the body collect information about the internal environment.
- sensory nerves: electrical impulses carrying a message about a stimulus are sent from receptors along sensory nerves to the spinal cord.
- spinal cord: passes the electrical messages up to the brain. reflexes (fast responses) are processed directly by the spinal cord.
- brain: processes information about external and internal changes. different parts of the brain use different kinds of information.
- spinal cords: if a response is needed then the brain sends electrical messages down the spinal cord and along nerves to effectors.
- effectors: may act tho change internal factors to maintain homeostasis. eg- muscles to make hair stand up, sweat glands to release water.
- many plants (esp northern hemisphere) are deciduous. they shed their leave and shut down their metabolism for the winter, like a hibernating animal.
- their leaves cannot be protected from freezing, so the strategy is to lose the vulnerable parts, survive until next spring, and grow new leaves then.
- warmer temperatures initiates a growing response.
- extreme heat will cause many herbaceous and non-woody plants to die back, leaving only dormant seeds with thick woody coats.
- in extreme heat the underground bulbs and tubers also stay dormant until temperatures and and rainfall are suitable.
- if the plant temperature rises too high enzymes can denature, metabolism is disrupted and the plant can die.