Homeostasis, Hormones & Excretion Flashcards
What is homeostasis
Maintaining a constant internal environment despite changes in external and internal factors
What is negative feedback
The mechanism that reverses a change, bringing the system back to the optimum
What is positive feedback
The mechanism that increases a change, taking the system further away from the optimum
- change is detected and exaggerated
What conditions do cells need to maintain
- temperature
- pH
- aqueous environment that keeps the substances and products in solution
- freedom from toxins and excess inhibitors
What is cell signaling
The way in which cells communicate with each other
Why are multicellular organisms more efficient than single celled organisms
Cells are differentiated
- specialized to Freeform a particular function
What does a good communication system do
- cover the whole body
- enable cells to communicate with each other
- enable specific communication
- enable rapid communication
- enable both short and long term responses
What are the two major systems of communication
- neuronal system
- hormonal system (endocrine)
What is the neuronal system
An interconnected network of neurons that signal to each other across synapse junctions
- enable rapid response to stimuli
What is the endocrine/hormonal system
System that uses the blood to transport its signals
- secrete the hormone directly into the blood
- travels through the body
- only recognized by specific target cells
- enables longer term responses
What are aspects that are maintained by homeostasis
- body temperature
- blood glucose concentration
- blood salt concentration
- water potential of the blood
- blood pressure
- carbon dioxide concentration
Example of the response pathway
- stimuli
- receptor
- communication pathway (cell signaling)
- effector
- response
What sensory receptors
Cells/sensory nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potentials
What processes must occur for negative feedback
- change to the internal environment must be detected
- the change must be signaled to the other cells
- must be an effective response that reverses the change in conditions
What happens to chemical reactions when temperature rises
- occur more quickly
- more kinetic energy
- collide more often
What is an ectotherm
An organism that relies on external sources of heat to maintain body temperature
What are endotherms
Organisms that use heat from metabolic reactions to maintain body temperature
What might ectotherms do if they are too cold
- move into a sunny area
- lie on a warm surface
- expose a larger surface area to the sun
What might ectotherms do if they are too warm
- move out of the sun
- move underground
- reduce the body surface exposed to the sun
Advantages of being an ectotherm
- less of their food is used in respiration
- more of the energy and nutrients gained from food can be converted to growth
- need to find less food
- can survive for long periods without food
Disadvantages of being an ectotherm
- less active in cooler temperatures
- risk of predation
- cannot take advantage of available food when cold
Ways skin has adapted to cool down
- sweat glands produce sweat
- sweat evaporated to increase heat loss
- hairs lie flat
- vasodilation
ways skin has adapted to heat up
- little to no sweat produced
- insulating layer of air is trapped above the skin
- hair erector muscle contracts to pull hair upright
- vasoconstriction
What is vasodilation
Blood cells open up allowing more blood to flow through capillaries
- more heat lost through radiation
