AQA A Level Biology - Topic 6 - Survival And Response

AQA A Level Biology - Topic 6 - Survival And Response What is a stimulus? A change in the environment of an organism What is a tactic response? What is a kinetic response? Directional movement in response to a stimulus Non directional random movement in response to a stimulus What is a positive and negative taxis? Positive taxis- organism moves towards stimulus Negative taxis - organism moves away from stimulus What Are receptors? different types What are effectors? cells, glands) Detect stimuli- can be cells or proteins on cell surface membrane , loads of Cells that bring about a response to a stimulus to provide an effect ( muscle Receptors communicate with effectors via the ....... What are the 3 types of neurones? Nervous or hormonal system or both Sensory neurones Motor neurones Relay neurones What do sensory neurons do? What do motor neurones do? effectors What do relay neurones do? neurones They carry impulses from receptors to the CNS. Transmit electrical impulses from the central nervous system to the Transmit electrical impulses between sensory neurones and motor What is the order of nervous communication including neurones Stimulus receptors sensory neurones CNS motor neurone effectors response - Stimulus detected by receptor cells and electrical impulse sent Outline nervous communication along sensory neurone - Electrical impulse reaches end of neurone ,neurotransmitters take info across synapse to the next neurone where another impulse is generated - the central nervous system processs info and sends impulses along motor neurones to effector Explain what neurotransmitters do They're chemical messengers secreted onto target cells creating a localised response which is rapid and short lived as they're quickly removed after they've done their job What is a simple reflex? Rapid involuntary response to a stimulus, goes through spinal cord but not conscious part of the brain - they're protective a fast What is the reflex arc? What is a tropism? Pathway of neurones linking receptors to effectors Response of a plant to a directional stimulus What is a positive tropism? What is a negative tropism? What is a phototropism? Growth towards the stimulus Growth away from stimulus Growth of a plant in response to light Shoots are .................. phototropic and grow .................. light Towards Positively Roots are ............... phototropic and grow .................. from the light Away What is gravitropism? ( aka geotropism) Negatively Growth of a plant in response to gravity Negatively Shoots are ..................... gravitropic and grow ................ roots are ............... gravitropic and grow .............. Upwards Positively Downwards What are growth factors? And where are they produced? speed up or slow down plant growth Hormone like chemicals in plants that Produced in Growing regions of plant and move to where needed What are auxins? plant hormones - growth factors How do auxins work? Produced in tips of shoots and diffuse backwards to stimulate the cell just behind the tips to elongate What is indoleacetic acid ( IAA) ? An auxin that is produced in the tips of shoots and roots Explain the movement and affects of indoleacetic acid in plants Moves around to control tropism- moves by diffusion and active transport over short distances and via the phloem in long distances. This results in different concentrations leading to uneven growth, Root growth is ..................... by high concentrations of IAA . Shoot growth is ................ by high concentrations of IAA Inhibited Promoted What is the resting potential? Negatively The potential difference ( or voltage) when a cell is at rest When a nervous system receptor is in its testing state, the inside is .................. charged compared to the outside What is a generator potential? The change in potential difference due to a stimulus A bigger stimulus excites the membrane more causing a bigger movement in ............ and a bigger change in ............... ................. so a bigger .................. ....................... is produced Ions Potential difference Generator potential What is an action potential? potential is big enough An electrical impulse along a neurone triggered if the generator An action potential is only triggered if the generator potential reaches a certain level called............ Threshold level Action potentials are all one size so the strength of the stimulus is measured by what? frequency of action potentials What are pacinian corpuscles? The Mechanoreceptors-detect mechanical stimuli such as pressure and vibrations What is a sensory nerve ending? t issue called lamellae End of a sensory neurone and is wrapped in loads of connective Explain what happens when a pacinian corpuscle is stimulated Lamellae are deformed and press on sensory nerve ending, this causes s the neurones cell membrane to stretch which deforms the stretch mediated ion channels, channels open and sodium ions diffuse into cell creating generator