CHAPTER 6 - STIMULI AND RESPONSE, NERVOUS COORDINATION AND HOMEOSTASIS Flashcards
- survival and response - nervous communication - responses in plants - receptors - control of heart rate - neurones - synaptic transmission - muscle structure - muscle contraction - homeostasis basics - control of blood glucose concentration - diabetes and blood glucose concentration - the kidneys - controlling blood water potential
how do organisms respond to their external environment
- organisms increase their chances of survival by responding to chances in their EXTERNAL ENVIRONMENT
- ANIMALS can MOVE AWAY from HARMFUL ENV, like places that are too hot or too cold
- PLANTS cant move themselves, but they can CHANGE THE WAY THEY GROW IN AN ATTEMPT TO FIND MORE FAVOURABLE ENV CONDITIONS, ex seedlings growing in dark conditions can rapidly develop very long and thin stems to INCREASE their chances of finding light
how do organisms respond to changes in their internal environment
organisms also respond to changes in their internal environment to ensure that the conditions are always OPTIMAL for their metabolism (all the chemical reactions that go on inside them)
define the term ‘stimulus’
- any change in the INTERNAL or EXTERNAL environment
- ex, a change in temp, light intensity or pressure
what are the names of the 2 simple responses in simple mobile organisms
- simple mobile organisms, like woodlice, have SIMPLE RESPONSES to keep them in a FAVOURABLE ENV
- their response can either be TACTIC or KINETIC
what is the tactic response/taxis
- DIRECTIONAL MOVEMENT in response to a stimulus
- the DIRECTION of the STIMULUS affects the response
give a example of how taxis works in simple mobile organisms
- woodlice show a tactic response to LIGHT, they move AWAY from a light source
- this response helps them SURVIVE because it keeps them concealed under stones during the day, where they are safe from predators, and keeps them in damp conditions, THIS REDUCES WATER LOSS
what is the kinetic response/kinesis in simple mobile organisms
- NON DIRECTIONAL/RANDOM movement in response to a stimulus
- the INTENSITY of the STIMULUS affects the response
give an example of kinesis in simple mobile organisms
- woodlice show a KINETIC response to HUMIDITY
- in HIGH HUMIDITY, they MOVE SLOWLY AND TURN LESS OFTEN, so they stay where they are
- as the air gets DRIER, they MOVE FASTER AND TURN MORE OFTEN, so they MOVE INTO A NEW AREA
- this response helps woodlice move from DRIER AIR to MORE HUMID AIR and then stay put
- this IMPROVES their chances of SURVIVAL because it REDUCES THEIR WATER LOSS and HELPS TO KEEP THEM CONCEALED
what is positive taxis
- if an organism moves TOWARDS a stimulus its a positive taxis
what is negative taxis
- if an organism moves AWAY from a stimulus, its a negative taxis
what is a simple response
- simple responses are automatic responses to a stimulus, the organism does NOT choose to where move
what do animals have to do with information in order to respond to changes in the environment
- in order to respond to changes in the environment, an organism needs to PASS INFO between diff areas of its body
- in animals, some of this communication is carried out using nerve impulses
what is the role of receptors
- receptors DETECT STIMULI
- they can be cells or proteins on cell surface membranes
- there are many different types of receptors which detect diff stimuli, ex baroreceptors detect changes in blood pressure
- receptors are specific to one type of stimulus
what is the role of effectors
- cells that BRING ABOUT A RESPONSE TO A STIMULUS to PRODUCE AN EFFECT
- effectors include muscle cells and cells found in glands, like the pancreas
how do receptors and effectors communicate
- receptors communicate with effectors via the NERVOUS SYSTEM or the HORMONAL SYSTEM or sometimes BOTH
what are neurones
- nerve cells
- the nervous stem is made up of a complex network of NEURONES
what are sensory neurones and what is their role
- they transmit electrical impulses from receptors to the CNS (the brain and spinal cord)
what are motor neurones and what is their role
- they transmit electrical impulses from the CNS to effectors
what are relay neurones and what is their role
- they are also known as INTERMEDIATE/INTER/ASSOSCIATION NEURONES
- they transmit electrical impulses between SENSORY neurones and MOTOR neurones
how does nervous communication work
- a STIMULUS is DETECTED by RECEPTOR CELLS and an ELECTRICAL IMPULSE is sent along a SENSORY NEURONE
- when an ELECTRICAL IMPULSE reaches the END of a neurone, CHEMICALS called NEUROTRANSMITTERS take the info across the SYNAPSE GAP to the NEXT NEURONE, where ANOTHER electrical impulse is generated
- the CNS processes the info and sends impulses along MOTOR neurones to an EFFECTOR
give the chain of what is involved in nervous communication
stimulus -> receptors (sensory neurone) -> CNS (motor neurone) -> effectors -> response
give an example of nervous communication
- ex, when you see a friend waving to you and you wave back in response
- STIMULUS - you see a friend waving
- RECEPTORS - light receptors (photoreceptors) in your eyes detect the wave, the electrical impulse is carried by a SENSORY NEURONE to the CNS
- CNS - processes INFO and sends an electrical impulse along a MOTOR NEURONE
- EFFECTORS - MUSCLE cells are stimulated by the MOTOR neurone
- RESPONSE - muscles CONTRACT to make your arm wave
describe the nervous response
- when an ELECTRICAL IMPULSE reached the END of neurone, chemical messengers called NEUROTRANSMITTERS are SECRETED DIRECTLY ONTO CELLS, like muscle cells, so the nervous response is LOCALISED
- NEUROTRANSMITTERS are QUICKLY REMOVED once they have done their job, so the response is SHORT LIVED
- ELECTRICAL IMPULSES are really FAST, so the response is usually RAPID and this allows animals to react QUICKLY to stimuli
describe what takes place in simple reflexes
- a simple reflex is a RAPID, INVOLUNTARY response to a STIMULUS
- the pathway of communication goes through the SPINAL CORD but NOT through the CONSCIOUS PARTS of the BRAIN, so the RESPONSE happens AUTOMATICALLY
- because there is no time to respond, INFO travels really FAST from RECEPTORS -> EFFECTORS
- SIMPLE REFLEXES are PROTECTIVE, they help organisms to AVOID DAMAGE TO THE BODY as the response happens so quickly