Topic 6

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Created by
Lilly May

Cards (79)

  • Stimulus

    A detectable change in the environment
  • Receptors

    Cells that can detect changes in the environment
  • Tropisms

    • Plant responses to their surroundings via growth
    • Can be positive (grow towards stimulus) or negative (grow away from stimulus)
    • Stimuli are light and gravity
  • Auxin (IAA)

    Growth factor that controls cell elongation in shoots and inhibits growth in roots
  • Phototropism

    1. Shoot tip cells produce IAA
    2. IAA diffuses to shaded side
    3. Cells on shaded side elongate
    4. Shoot bends towards light
  • Gravitropism

    1. IAA diffuses to lower side of shoot
    2. Lower cells elongate
    3. Shoot bends upwards against gravity
  • Gravitropism in roots

    1. IAA moves to lower side
    2. Upper cells elongate
    3. Root bends downwards towards gravity
  • Reflex

    Rapid automatic response to protect from danger
  • Reflex arc

    Made up of 3 neurons: sensory, relay, motor
  • Taxis

    Organism moves its entire body towards or away from a stimulus
  • Positive taxis

    Organism moves towards a favorable stimulus
  • Negative taxis

    Organism moves away from an unfavorable stimulus
  • Kinesis

    Organism changes speed of movement and rate of direction changes in response to stimuli
  • Pacinian corpuscle

    Pressure receptor with stretch-activated sodium channels
  • Rods

    Photoreceptors that detect black and white images in low light
  • Cones

    Photoreceptors that detect colour in high light intensity
  • Fovea

    Region of retina with high concentration of cone cells
  • Cardiac muscle

    Myogenic - contracts and relaxes on its own
  • Heartbeat control

    1. SA node sets pace
    2. Depolarization wave spreads to AV node
    3. Delayed conduction to ventricles via bundle of His
    4. Ventricles contract from apex upwards
  • Wave of depolarization

    1. Non-conductive layer of tissue separates atria and ventricles
    2. Wave of depolarization travels down bundle of His
    3. Wave of depolarization travels up through Purkinje fibers
  • Wave of depolarization travels down bundle of His and up through Purkinje fibers

    Causes a slight delay in time for ventricles to contract
  • Delay allows atria to contract and force blood into ventricles before ventricles contract
  • Ventricles contract from apex to base, like squeezing toothpaste from bottom up
  • Cells repolarize, causing cardiac muscle to relax, then cycle repeats
  • Medulla oblongata

    Controls heart rate through autonomic nervous system
  • Parts of autonomic nervous system
    • Sympathetic nervous system
    • Parasympathetic nervous system
  • Sympathetic nervous system impulses
    Increase heart rate
  • Parasympathetic nervous system impulses
    Decrease heart rate
  • Chemoreceptors

    Detect changes in blood pH
  • Pressure receptors

    Detect changes in blood pressure
  • Increased respiratory rate

    Decreases blood pH due to excess CO2 and lactic acid
  • Decreased blood pH

    Increases heart rate to remove excess CO2
  • High blood pressure

    Increases impulses through parasympathetic nervous system to decrease heart rate
  • Low blood pressure

    Increases impulses through sympathetic nervous system to increase heart rate
  • Myelinated motor neuron

    • Cell body with organelles
    • Dendrites carrying action potentials
    • Axon conducting nerve impulses
    • Schwann cells forming myelin sheath
    • Nodes of Ranvier where axon is not insulated
  • Resting potential

    Difference in electrical charge inside and outside axon when no stimulus, around -70mV
  • Maintaining resting potential

    1. Sodium-potassium pump actively transports 2 K+ in and 3 Na+ out
    2. Creates electrochemical gradient causing K+ to diffuse out and Na+ to diffuse in
    3. More K+ diffusing out than Na+ diffusing in results in net negative charge inside
  • Generation of action potential
    1. Stimulus opens Na+ voltage-gated channels
    2. Na+ influx depolarizes membrane beyond threshold
    3. More Na+ channels open, further depolarization
    4. Na+ channels close, K+ channels open, repolarization occurs
    5. Overshoot to -80mV, refractory period
  • All-or-nothing principle

    • If stimulus not large enough to reach threshold, no action potential generated
    • If threshold reached, full action potential always generated
  • Refractory period

    Period after action potential when another cannot be generated immediately