B14 RESPONSE TO STIMULI

• Stimulus


  A detectable change in the internal or external environment of an organism
• Receptors


  Specific to one type of stimulus, with the coordinator finding an appropriate response
• Taxis


  A specific movement, with directed motion
• Kinesis


  A random movement, with undirected motion
• Positive Taxis


  A specific movement towards a stimulus
• Negative Taxis


  A specific movement away from a stimulus
• Tropism


  The growth of a plant in relation to a directional stimulus
• Growth Factors


  The hormone-like substances which allow plants to respond to light, water and gravity
• IAA


  The name of the growth factor in plants
• Promoted


  Having increased concentration of IAA in the tip of a plant shoot, is cell elongation promoted or inhibited?

  
• Inhibited


  Having increased concentration of IAA in the tip of a plant root, is cell elongation promoted or inhibited?

  
• CNS


  Consists of the brain and the spinal cord in nervous organisation
• PNS


  Consists of pairs of nerves that originate from the brain or spinal cord
• Sensory Neurones


  One division of the PNS which carry nervous impulses from receptors towards the CNS
• Motor Neurones


  One division of the PNS which carry nervous impulses from the CNS towards effectors
• Voluntary Nervous System


  One division of the motor nervous system which carries out nervous impulses to muscle under conscious control
• Autonomic Nervous System


  One division of the motor nervous system which carries out nervous impulses to glands, smooth muscle and cardiac muscle under subconscious control
• 4623751


  The following shows the process of a reflex arc, put the steps in the correct order:

  1) Response

  2) Sensory Neurone

  3) Intermediate Neurone

  4) Stimulus

  5) Effector

  6) Receptor

  7) Motor Neurone
• Importance of Reflex Arcs


  They are important because:

  - They are involuntary so do not require thinking power

  - They are fast due to the short pathway

  - Protect the body from harm
• Features of Sensory Reception


  The Pacinian corpuscle is:

  - Specific to one type of stimulus

  - The producer of a generator potential through acting as a transducer (converts the stimuli into energy)
• Stretch-Mediated


  The name of the sodium channel that is part of the pacinian corpuscle, which are deformed to allow for the movement of sodium ions
• Fovea


  The location of cones in the eye
• Periphery


  The location of rods in the eye
• 1


  The number of cone cells connected to one bipolar cell
• 3


  The number of rod cells connected to one bipolar cell
• Good


  The visual acuity of cones
• Poor


  The visual acuity of rods
• Sensitive


  The sensitivity of rods in low light
• Not Sensitive


  The sensitivity of cones in low light
• Summation


  The reason for the visual acuity of cones and the sensitivity of rods
• Rhodopsin


  The chemical broken down when rods absorb light
• Iodopsin


  The chemical broken down when cones absorb light
• Sympathetic Nervous System


  One division of the autonomic nervous system which speeds up activity and makes someone more aware
• Parasympathetic Nervous System


  One division of the autonomic nervous system which slows down activity in normal circumstances
• Sinoatrial Node


  The group of cells that stimulate atrial systole
• Atrioventricular Node


  The group of cells send electrical signals down the bundle of His and across Purkinje fibres to stimulate ventricular systole
• Medulla Oblongata


  The periphery of the brain with two centres to help increase and decrease heart rate
• Chemoreceptors


  The receptors found in the walls of the carotid artery which detect changes in pH
• 316542

  The following show the steps that control heart rate with variations of pH (changes of CO2 in the blood). Put them in the correct order:

  1) Chemoreceptors detect the change in pH, increasing the frequency of impulses to the centre in the medulla oblongata that increases heart rate

  2) The meulla oblongata reduces the frequency of nervous impulses to the sinoatrial node, returning the heart rate to normal

  3) pH is lowered from high concentration of CO2 in the blood

  4) pH rises to normal levels, which is detected by chemoreceptors

  5) Blood flow increases so more CO2 is removed by the lungs

  6) The centre increases the number of frequencies via the sympathetic nervous system to the sinoatrial node, increasing heart rate
• 1324

  The following show the steps that control heart rate with pressure receptors. Put them in the correct order:

  1) Blood pressure is higher than usual

  2) The centre sends impulses via the parasympathetic nervous system to the sinoatrial node

  3) Pressure receptors detect the change and increases the number of impulses sent to the centre of the medulla oblongata to reduce heart rate

  4) The heart rate decreases