B3

• What is the difference between the central nervous system and the peripheral nervous system?

  • The central nervous system is the brain and the spinal chord.
  • The peripheral nervous system is every other part of the nervous system.
• What is a stimulus?

  A stimulus is a change in the environment.
• What type of neurone connects a receptor to the CNS?

  A sensory neurone.
• What is an effector?

  A part of a body that brings about the response to a stimulus like a muscle or a gland.
• What type of neurone connects the CNS to an effector?

  A motor neurone.
• Describe the reflex arc.

  • Stimulus detected by a receptor.
  • Impulse passed along the sensory neurone to CNS.
  • Impulse passed along motor neurone to effector.
  • Effector brings about the response.

  Stimulus ---> Receptor ---> Sensory neurone ---> CNS ---> Motor neurone ---> Effector ---> Response
• What is the cornea and what is its function?

  The transparent layer in front of the eye that protects the eye from damage.
• What is the iris and what is its function?

  The coloured ring around the pupil that controls its diameter by contracting or relaxing.
• What is the pupil and what is its function?

  The pupil is the hole in the middle of the iris that lets light into the eye.
• What is the optic nerve and what is its function?

  The nerve coming out the back of the eye that sends signals (nerve impulses) to the brain.
• What is the function of the lens?

  The lens focuses the light rays onto the retina.
• What is the retina and what is its function?

  The retina is the back part of the eye and it converts visual stimuli into electrical impulses.
• What do the ciliary body and suspensory ligaments do?

  They control the shape of the lens (accommodation).
• What are rods and what is their function?

  Rods are photoreceptor cells in the retina that detect light and are responsible for vision in low light conditions. They only allow us to see in black and white.
• What are cone cells and their function?

  Cones are photoreceptor cells in the retina that detect different colours and are responsible for seeing colour. Different cone cells respond to red, blue, and green light.
• What is the fovea and its function?

  Central point of the retina that contains only cone cells. It is this region where light is focused the most so that we can see things clearly.
• What are circular muscles and their functions?

  The muscles that are stretched around the pupil.

  In bright light the circular muscles contract.

  In dull light the circular muscles relax.
• What are radial muscles and their function?

  The muscles on the outside of the circular muscle around the pupil, also responsible for pupil size.

  In bright light the radial muscles relax.

  In dull light the radial muscles contract.
• What defect in the eye causes short sightedness?

  The lens focuses light rays in front of the retina so far away objects appear blurry. The person's lens is too strong, or the eyeball is too long.
• How is short sightedness corrected?

  By wearing glasses that have concave lenses.
• What defect in the eye causes long sightedness?

  The lens focuses light behind the retina so nearby objects appear blurry. The person's lens is too weak, or the eyeball is too short.
• How is long sightedness corrected?

  By wearing glasses that have convex lenses.
• What is colour blindness?

  • It is an inherited condition where people find it difficult to tell the difference between colours.
  • It is caused by a defect in the retina and there is currently no cure.
• Where is the cerebrum located and what is its function?

  • It is located at the front of the brain.
  • It controls conscious activities, such as memory and language.
• Where is the cerebellum located and what is is function?

  • It is located at the back bottom of the brain.
  • It controls muscular movement and balance.
• Where is the medulla located and what is its function?

  • It is located in the brainstem in the middle at the bottom.
  • It controls unconscious functions like heart rate and breathing.
• What is the function of the hypothalamus?

  It acts as the regulatory centre and controls things like body temperature, water content and salt balance.
• What is the function of the pituitary gland?

  It releases hormones into the blood.
• Label the brain.

  A) Pituitary Gland

  B) Cerebellum

  C) Cerebrum

  D) Hypothalamus

  E) Medulla

  
• Give 2 reasons why it is difficult to investigate brain function.

  • Surgery is not risk free.
  • People with brain disorders may be unable to consent.
• Why is it difficult to treat brain disorders?

  • The brain and spinal cord are very difficult to access.
  • Tissues in the CNS cannot regenerate.
  • Drugs cannot penetrate the blood-brain barrier.
• What are hormones?

  Hormones are chemical messengers that are secreted by glands of the endocrine system into the bloodstream.
• What are the target cells?

  Target cells are cells with the specific receptor for a hormone that produce an effect when the hormone binds.
• What does the hormone thyroxine control in the body?

  Thyroxine controls metabolic rate.
• Describe thyroxine as a negative feedback system.

  • When the level of thyroxine decreases the pituitary gland produces thyroid stimulating hormone (TSH) which causes the thyroid gland to produce more thyroxine.
  • When the level of thyroxine increases, the pituitary gland produces less TSH.
• When is adrenaline secreted?

  During times of anxiety, fear, or stress.
• Give 3 effects of adrenaline in the body.

  1. Increases heart rate and breathing rate.
  2. Increases blood glucose concentration.
  3. Dilates the pupils.
• What does oestrogen do?

  Oestrogen causes the uterus lining to thicken. Also inhibits FSH production so only one egg matures. It also stimulates LH to be released by the pituitary gland.
• What does progesterone do?

  Progesterone maintains uterus and womb lining. Also inhibits LH and FSH.
• What does FSH do?

  FSH stimulates an egg to mature and stimulates the ovaries to release oestrogen.