Human Nervous System

• What is the function of the nervous system?

  React to surroundings and coordinate responses
• How does a stimulus lead to a response in the body?

  Stimulus converts to impulse, sent to CNS
• What sequence describes how the nervous system works?

  • Stimulus
  • Receptor
  • Coordinator
  • Effector
  • Response
• What is a reflex action?

  Automatic and rapid response without brain input
• Why are reflex actions important?

  They prevent harm and aid survival
• Describe how a reflex action occurs via a reflex arc.

  1. Stimulus detected by receptor
  2. Impulse travels along sensory neurone to spinal cord
  3. Chemical diffuses at synapse to relay neurone
  4. Impulse travels to motor neurone
  5. Effector carries out response
• What is the difference between a reflex pathway and a conscious pathway?

  Reflex uses spinal cord; conscious uses brain
• What is the function of the cerebral cortex?

  Controls consciousness, intelligence, memory, language
• What is the function of the cerebellum?

  Controls muscular coordination
• What is the function of the medulla?

  Controls unconscious activities like breathing
• Why is investigating and treating the brain difficult?

  • Complex and delicate organ
  • Easily damaged
  • Membranes block drug access
  • Unknown functions of brain parts
• What methods do scientists use to determine brain function?

  • Studying brain damage patients
  • Electrical stimulation of the brain
  • MRI scans
• What stimuli are the receptors of the eye sensitive to?

  Light intensity and colour
• What are the two main functions of structures in the eye?

  • Accommodation for focusing
  • Adaptation to dim light
• Describe the structure and function of the retina.

  • Light-sensitive layer at back of eye
  • Stimulated by light, sends impulses to brain
• Describe the structure and function of the optic nerve.

  • Connects eye to brain
  • Carries impulses for image visualization
• Describe the structure and function of the sclera.

  • Tough outer layer of the eye
  • Protects internal structures
• Describe the structure and function of the cornea.

  • Curved transparent layer at front of eye
  • Lets light in and focuses it onto retina
• Describe the structure and function of the iris.

  • Muscle controlling pupil size
  • Adjusts eye to bright and dim light
• Describe the structure and function of the ciliary muscles and suspensory ligaments.

  • Hold lens in place
  • Control lens shape for focusing
• Describe how the iris alters the size of the pupil in bright and dim light.

  • Contracts in bright light to reduce size
  • Relaxes in dim light to increase size
• What is the structure of the iris?

  The iris is a muscle
• What is the function of the iris?

  It controls the size of the pupil
• How does the iris help the eye adjust to lighting conditions?

  By contracting or relaxing to change pupil size
• What do the ciliary muscles and suspensory ligaments do?

  They hold the lens in place
• What is the role of ciliary muscles in vision?

  They control the shape of the lens
• How does the iris alter the size of the pupil in bright light?

  Circular muscles contract, radial muscles relax
• What happens to the pupil in dim light?

  Circular muscles relax, radial muscles contract
• What is accommodation in the eye?

  Alteration of the lens' shape for focus
• How does the eye focus on a nearby object?

  Ciliary muscles contract and lens thickens
• What occurs when the eye focuses on a far away object?

  Ciliary muscles relax and lens thins
• What is myopia?

  Short-sightedness due to a curved lens
• How does myopia affect vision?

  Light is focused in front of the retina
• How can myopia be treated?

  Using glasses with a concave lens
• What is hyperopia?

  Long-sightedness due to a flat lens
• How does hyperopia affect vision?

  Light is focused behind the retina
• How can hyperopia be treated?

  Using glasses with a convex lens
• What are the two types of contact lenses?

  • Hard: Rigid material, long-lasting, must be sterile
  • Soft: Flexible material, shorter lifespan, more comfortable
• What is laser eye surgery?

  Use of lasers to fix visual defects
• How does laser eye surgery treat myopia?

  By reducing the thickness of the cornea