Chapter 10

• What is sensitivity in organisms?

  An organism’s ability to respond to a stimulus.
• What is a stimulus?


  A change in the environment that causes a reaction in an organism.
• What is the response in the context of sensitivity?

  The resulting reaction to a stimulus.
• What are the two main components of the human nervous system?

  The central nervous system (CNS) and the peripheral nervous system (PNS).
• How does the nervous system regulate bodily functions?

  By coordinating responses to stimuli from the surroundings.
• What happens when there is a stimulus?

  The receptors in our sense organs are stimulated to produce nerve impulses.
• What do nerve impulses do after being produced by receptors?

  They are transmitted by nerves to the central nervous system.
• What role does the central nervous system play after receiving nerve impulses?

  It sends the nerve impulses to the effectors, which are either muscles or glands.
• What is the function of the spinal cord in the central nervous system?

  It is involved mostly in automatic actions known as reflex actions.
• What does the brain do in the central nervous system?


  It integrates visual, auditory, touch, olfactory, and taste information from our sensory organs.
• What is the role of a sensory neurone?


  It transmits nerve impulses from the receptors to the central nervous system.
• What is the function of a relay neurone?


  It transmits nerve impulses within the central nervous system.
• What does a motor neurone do?

  It transmits nerve impulses from the central nervous system to the effectors.
• What is a synapse?


  A synapse is the junction between two neurones.
• What happens at a synapse?


  The neurones release chemicals (neurotransmitters) that help transmit nerve impulses across the synapse.
• What are voluntary actions?


  Activities that are controlled consciously.
• What are involuntary actions?


  Activities that are not controlled consciously.
• What is a reflex action?


  An immediate response to a specific stimulus without conscious control.
• What are the two types of reflex actions?

  Cranial reflexes controlled by the brain and spinal reflexes controlled by the spinal cord.
• What is a reflex arc?

  A reflex arc is the shortest pathway by which nerve impulses travel from the receptor to effector in a reflex action.
• Compare voluntary actions, involuntary actions, and reflex actions.

  • **Voluntary Action**: Controlled by will, requires a stimulus, regulated by the brain, produced by choice, may be slow or quick.
  • **Involuntary Action**: Not controlled by will, requires a stimulus, regulated by the brain, occurs throughout life.
  • **Reflex Action**: A sudden action in response to a stimulus, regulated by the brain or spinal cord, always quick.
• What are the key differences between endocrine and nervous controls?

  • Both involve a stimulus, a transmitted message, and a target organ (effector).
  • Endocrine control is slower and uses hormones, while nervous control is faster and uses nerve impulses.
• What attaches each eyeball to the skull?

  Rectus muscles which control eye movement.
• What is the sclera?

  A tough, white outer covering of the eyeball.
• What is the function of the conjunctiva?

  It secretes mucus to keep the front of the eyeball moist.
• What is the role of eyelashes?

  They shield the eye from dust particles.
• What do tear glands do?

  They secrete tears that wash away dust particles and lubricate the conjunctiva.
• What is the function of eyelids?

  They protect the cornea from mechanical damage and help spread tears over the conjunctiva and cornea.
• What is the iris?

  A circular sheet of muscles that control the size of the pupil and the amount of light entering the eye.
• What is the pupil?


  A hole in the center of the iris that allows light to enter the eye.
• What is the cornea's function?

  It is a dome-shaped transparent layer that refracts light rays into the pupil.
• What is the aqueous chamber?

  It is the space between the cornea and lens filled with aqueous humour, which helps to refract light rays into the pupil.
• What is the ciliary body?


  A thickened region at the front end of the choroid that contains ciliary muscles, which control the curvature of the lens.
• What is the hole in the center of the iris called?

  Pupil
• What is the cornea?

  A dome-shaped transparent layer continuous with the sclera
• What is the function of the cornea?

  It refracts (bends) light rays into the pupil
• What is the aqueous chamber?

  Space between the cornea and lens filled with aqueous humour
• What is the role of aqueous humour?

  It keeps the front of the eyeball firm and helps to refract light rays into the pupil
• What is the ciliary body?

  A thickened region at the front end of the choroid
• What do the ciliary muscles do?

  They control the curvature of the lens