Topic 6 survival and responsr

• What is a stimulus?


  A change in the environment of an organism
• What is a tactic response?

  Directional movement in response to a stimulus
• What is a kinetic response?

  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?

  Detect stimuli- can be cells or proteins on cell surface membrane , loads of different types
• What are effectors?

  Cells that bring about a response to a stimulus to provide an effect ( muscle cells, glands)
• Receptors communicate with effectors via the .......

  Nervous or hormonal system or both
• What are the 3 types of neurones?

  Sensory neurones

  Motor neurones

  Relay neurones
• What do sensory neurons do?

  They carry impulses from receptors to the CNS.
• What do motor neurones do?


  Transmit electrical impulses from the central nervous system to the effectors
• What do relay neurones do?


  Transmit electrical impulses between sensory neurones and motor neurones
• What is the order of nervous communication including neurones

  Stimulus > receptors > sensory neurones> CNS > motor neurone > effectors > response
• Outline nervous communication

  - Stimulus detected by receptor cells and electrical impulse sent 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?


  Pathway of neurones linking receptors to effectors
• What is a tropism?

  Response of a plant to a directional stimulus
• What is a positive tropism?

  Growth towards the stimulus
• What is a negative tropism?

  Growth away from stimulus
• What is a phototropism?

  Growth of a plant in response to light
• Shoots are .................. phototropic and grow .................. light

  Positively

  Towards
• Roots are ............... phototropic and grow .................. from the light


  Negatively

  Away
• What is gravitropism? ( aka geotropism)

  Growth of a plant in response to gravity
• Shoots are ..................... gravitropic and grow ................ roots are ............... gravitropic and grow ..............


  Negatively

  Upwards

  Positively

  Downwards
• What are growth factors? And where are they produced?

  Hormone like chemicals in plants that speed up or slow down plant growth

  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?


  The potential difference ( or voltage) when a cell is at rest
• When a neurone is in its resting state, the inside is .................. charged compared to the outside(outside is more positive - more NA+ and K+)


  Negatively
• What is a generator potential?


  The change in potential difference due to a stimulus. Generator potential causes an action potential if the stimulus is big enough to reach the threshold level.
• 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?


  An electrical impulse along a neurone triggered if the generator potential is big enough
• 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?


  The frequency of action potentials
• What are pacinian corpuscles?

  Mechanoreceptors-detect mechanical stimuli such as pressure and vibrations
• What is a sensory nerve ending?

  End of a sensory neurone and is wrapped in loads of connective tissue called lamellae
• 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 potential