C and R

• Electrical impulses


  Signals that travel along neurons
• Parts of the nervous system

  • Central nervous system (brain and spinal cord)
  • Peripheral nervous system (nerves and neurons)
• Voluntary actions


  Actions under conscious control
• Involuntary actions


  Actions not under conscious control
• Nerve impulse


  Electrical signal that passes along nerve cells (neurons)
• Types of neurons


  • Motor neuron
  • Relay neuron
  • Sensory neuron
• Motor neuron


  • Cell body at one end, myelin sheath insulating length, nerve endings at other end
• Sensory neuron


  • Cell body in middle, dendrites at one end, axon terminal at other end
• Relay neuron


  • Shorter, more branched out, cell body at one end
• Reflex action


  Automatic and rapid integration and coordination of stimuli with responses of effectors
• Reflex arc


  1. Stimulus affects receptor

  2. Sensory neuron carries impulse to CNS

  3. Relay neuron carries impulse in CNS

  4. Motor neuron carries impulse from CNS to effector

  5. Effector (muscle or gland) carries out response
• Synapse


  Junction between two neurons consisting of a gap across which impulses pass by diffusion of neurotransmitters
• Events at synapse


  1. Vesicles containing neurotransmitters move to cell membrane and release contents into synaptic cleft

  2. Neurotransmitters diffuse across synapse and attach to receptor molecules in next neuron
• Drugs


  Can prevent neurotransmitters from diffusing across synapse, reducing pain sensation
• Sense organs


  Groups of receptor cells that respond to specific stimuli like light, sound, touch, temperature, chemicals
• Parts of the eye

  • Cornea
  • Iris
  • Pupil
  • Lens
  • Retina
  • Optic nerve
• Cornea


  Refracts light
• Iris


  Controls amount of light entering pupil
• Pupil


  Opening in iris through which light enters eye
• Lens


  Can change thickness to focus light onto retina
• Retina


  Contains light receptors (rods and cones) sensitive to light and color
• Optic nerve


  Transmits visual information from retina to brain
• Eye


  • Part of the eye where light enters
  • Lens - can become thicker or thinner to focus light onto the retina
• Retina


  Part of the eye that contains light receptors like rods and cones, sensitive to light and color
• Rods and cones in the retina allow you to identify and detect different colors
• The retina is at the back of the eye, the cornea, iris, and lens are in the front
• You don't need to know much about the other parts of the eye, but you need to know about the suspensory ligaments and ciliary muscles
• Fovea


  Part of the retina where light receptors are most concentrated
• Optic nerve


  Part extending out of the eye that carries visual information to the brain
• Pupil reflex


  1. Pupil size adjusts to control light intensity

  2. When light is low, radial muscles contract to dilate pupil

  3. When light is high, circular muscles contract to constrict pupil
• Pupil reflex


  • Function is to adjust the eye for high or low light intensity
• When light intensity is low

  Radial muscles contract, circular muscles relax to dilate pupil
• When light intensity is high


  Circular muscles contract to constrict pupil
• Antagonistic muscles


  Muscles that oppose the action of each other, like radial and circular muscles in the eye
• Accommodation


  1. Eye adjusts to focus on near and distant objects

  2. For near objects, ciliary muscles contract, suspensory ligaments relax, lens becomes shorter and fatter

  3. For distant objects, ciliary muscles relax, suspensory ligaments tighten, lens becomes thinner and longer
• Rods


  Provide low-detailed black and white images, useful for low light
• Cones


  Provide detailed color images, work in high light intensity
• Rods are more concentrated around the edge of the retina, cones are most concentrated at the center
• Hormone


  Chemical substance produced by a gland and carried in the blood that alters the activity of target organs
• Hormones and their functions

  • Adrenaline - produced in adrenal gland, prepares body for vigorous action
  • Insulin - produced in pancreas, reduces blood glucose concentration
  • Testosterone - produced in testes, causes male sexual characteristics
  • Estrogen - produced in ovaries, causes female sexual characteristics