Reflexes

• What is a reflex action?

  Reflex actions are responses to changes that do not involve any processing in the brain.
• What are the components of most reflex pathways?

  • Sensory neurone
  • Relay neurone
  • Motor neurone
• How does the brain relate to reflex actions?

  The brain may be informed that the reflex has happened but is not involved in coordinating the response.
• Why do reflex actions have survival value?

  Reflex actions always have a survival value.
• What is the role of the knee jerk reflex?

  The knee jerk reflex is involved in coordinating movement and balance.
• What happens to the quadriceps during the knee jerk reflex?

  The quadriceps contract to straighten the leg.
• How is the quadriceps muscle attached to the lower leg?

  The quadriceps muscle is attached to the lower leg via the patella tendon.
• What triggers the knee jerk reflex when the knee cap is struck?

  Stretch receptors (muscle spindles) increase in length.
• What occurs in the absence of a relay neurone during the knee jerk reflex?

  The motor neurone is directly stimulated, causing the quadriceps to contract.
• What is the role of interneurons in the knee jerk reflex?

  Interneurons delay signalling to the opposing muscle to contract, allowing the leg to move forward.
• How does the cerebrum respond to threats in the fight or flight response?

  The cerebrum uses sensory input from external and internal threats.
• What happens when a threat is recognized in the fight or flight response?

  It stimulates the hypothalamus, activating the sympathetic nervous system and releasing hormones from the pituitary gland.
• What do sensory neurones detect in the fight or flight response?

  Sensory neurones detect environmental stimuli associated with danger.
• What is the role of the amygdala in the fight or flight response?

  The amygdala sends impulses to various parts of the brain, including the hypothalamus.
• What does the hypothalamus do in response to danger?

  The hypothalamus sends impulses via the sympathetic nerves to the adrenal glands.
• What hormone is secreted by the adrenal medulla during the fight or flight response?

  The adrenal medulla secretes the hormone epinephrine/adrenaline.
• How does epinephrine/adrenaline affect the organism during the fight or flight response?

  Epinephrine/adrenaline stimulates target organs and tissues to increase sensory awareness.
• What are the physiological changes during the fight or flight response?

  • Increased heart rate
  • Elevated blood pressure
  • Enhanced energy availability
  • Heightened alertness