survival and reflexes?

how can organisms increase their chance of survival?

• by detecting a change and responding accordingly

what 2 environments can organisms detect change in?

• external environments: (e.g- temperature of surroundings)

• internal environments: (e.g- blood glucose concentration)

what 3 components does coordinating a response to the environment involve?

• stimulus - change in environment

• receptors - detect change in environment

• effectors - initiate the response

what are reflex responses?

• quick and automatic responses to stimulus

• they often help an organism respond quickly to a harmful substance, e.g- heat

• the information is not processed in the brain and no decision is made about the response

what is a reflex arc?

• the pathway of neurones involved in a reflex response

• the 3 types of neurones include:

  • sensory

  • intermediate (relay)

  • motor

example of reflex arc: when person withdraws their hand from a hot object

• stimulus: hot object

• receptors: thermoreceptors in the skin detect the heat stimulus

• sensory neurone: carries impulse from thermoreceptors to the intermediate neurone in the spinal chord

• intermediate neurone: carries impulse to motor neurone

• motor neurone: carries impulse to effectors (muscles in arm)

• response: arm moves away from hot object