4.2 - Human survival in a range of environments

Define homeostasis

Homeostasis is keeping the internal environment of the body constant despite changes in the internal or external environment

What is the external environment

The internal surface where inputs and outputs have not yet crossed the membrane into the internal environment

What does the internal environment consist of?

internal environment is all fluids that surround the body cells

consists of:

• blood plasma

• extracellular fluid

  • provide essential input of cells (nutrients, oxygen) and removes (CO2, urea) and transports molecules like hormones

Intracellular fluid - internal environment of cells (cytosol)

optimum range

where conditions are best for organisms to survive and thrive

tolerance range

conditions move out of optimum range but organisms can survive (but not thrive)

zone of physiological stress

conditions out of optimum if regulatory mechanisms cope then may survive if only for short time until back to optimum
mechanism will try to deal with fluctuations

zone of intolerance

cannot survive

the two body system that play a large role in homeostasis are:

• the nervous system

• the endocrine system

stimulus

something that causes a change

receptors

detects the change

control centre (modulator)

processes change & transmits the message to start a corrective response (typically brain hypothalamus)

effector

muscles and glands trigger corrective response

response

carry out change, corrective response

negative feedback and why is it good?

when a change occurs and body counteracts the affect to bring body back to optimal conditions (set point/norm)

positive feedback

increase/reinforce the stimulus rather than returning to optimal range

interoceptors

detect internal changes (changes in the internal environment) in the body (change in CO2, glucose concentration, water concentration, pH levels)

exteroceptors

located on or near surface of the body and detects external stimuli

how does external temp affect body’s homeostatic control mechanism

external temperature affects our body’s homeostatic control mechanism as the body mechanisms will work to maintain normal core temperature