biology - homeostasis & response

• stimulus > receptor > coordinator > effector > response
• reflex actions: rapid, automatic, unconscious responses to stimuli that are triggered by the nervous system, aiding survival by preventng harm to the body.
• homeostasis: the maintenance of a constant internal environment in order to maintain optimum conditions for enzyme function.
• function of a receptor?

  detect changes in the environment (stimuli)
• function of coordination system?

  obtain & process information from receptors
• function of effectors?

  Response to stimuli
• what is the CNS made up of?

  The CNS (Central Nervous System) is made up of the brain and spinal cord.
• The nervous system enables humans to react to their surroundings and to coordinate their behaviour.
• The CNS coordinates the response of effectors which may be muscles contracting or glands secreting hormones.
• Reflex actions are automatic and rapid; they do not involve the conscious part of the brain.
• how reflex actions work via a reflex arc:

  1. stimulus is detected by receptor
  2. an electrical impulse passes along a sensory neuron to spinal cord
  3. at the synapse between a sensory and relay neuron, a chemical diffuses across, and stimulates a new impulse which is passed along the relay neuron.
  4. same process occurs at synapse between motor & relay neuron
  5. at the effector an appropriate response is carried out.
• sensory neuron: neuron that carries information from the senses to the CNS
• relay neuron: a neuron that connects sensory neurons to motor neurons
• motor neuron: a neuron that carries impulses from the CNS to the effector organs
• The brain controls complex behaviour. It is made of billions of interconnected neurones and has different regions that carry out different functions.
• function of cerebral cortex: processing language, memory, reasoning, thought, learning, decision-making, emotion, intelligence and personality.

  function of cerebellum: muscle control, including balance and movement

  function of medulla: controls vital processes like your heartbeat, breathing and blood pressure.

  A) medulla

  B) cerebellum

  C) cerebral cortex

  
• .

  A) cerebral cortex

  B) coordination of muscular activity

  C) medulla

  D) heartbeat/breathing

  
• conditions maintained by homeostatis:

  1. blood glucose concentration
  2. body temperature
  3. water levels
• what is accomodation?

  the alteration of the lens' shape in order to focus on near or distant objects.
• The eye is a sense organ containing receptors sensitive to light intensity and colour
• pupil in dim light: ciliary muscles relax & radial muscles contract, making the pupil larger so more light can enter the eye.
• .

  A) optic nerve

  B) retina

  C) sclera

  D) ciliary muscles

  E) suspensory ligaments

  F) cornea

  G) iris

  H) lense