sensations and responses

• What are stimuli?


  the senses that evoke responses in an organism
• What are the types of stimuli?

  external stimuli and internal stimuli
• examples of external stimuli are light, temperature, sound, and chemical pressure.
• Examples of internal stimuli are hunger, thirst, pressure, vibration, and infection.
• What is the function of the nervous system?

  To generate coordinate responses according to the external and internal charge.
• what is the function of the of the nervous system? (longer)

  to process information received from the sensory organs and other parts of the body and to activate appropriate actions in response to external/internal stimuli.
• Name the parts of the body included in our nervous system.

  1. brain
  2. spinal cord
  3. nerves
  4. receptors
• name the parts of the body included in our nervous system

  brain, spinal cord, nerves, receptors
• The structural and functional units of the nervous system are neurons, aka nerve cells.
• specialized cells in the sense organs or other parts of the body to receive stimuli is known as receptors.
• neuron has a cell membrane, cytoplasm and nucleus.
• structure of neuron: cell body, cytoplasm, dendrite, dendron, Schwann cell, axon, axonite and synaptic knob.
• Dendron:

  • a short filament
  • carries impulses from the dendrites to the cell body
• Dendrite:

  • Branches of dendron
  • part that receives impulses from the adjacent neuron
• Axon:

  • the longest filament from the cell body
  • carries impulses from the cell body to outside
• axonite:

  • branches of axon
  • carries impulses to the synaptic knob
• Schwann cell:

  • encircles the axon
• synaptic knob:

  • tip of axonite
  • secretes neurotransmitters
• The axon of most of the neurons is repeatedly encircled by myelin, a membrane containing lipids. this is called the myelin sheath.
• myelin sheath in the nerves is formed of schwann cells.
• myelin sheath in the brain and spinal cords are formed of specialized cells called oligodendrocytes.
• myelin sheath has a white shiny color
• the part of the brain and spinal cords where myelinated cells are present in abundance is called white matter and the part where unmyelinated nerve cells are present is called grey matter.