Stimulus occurs / Sensory Receptors Detect the Stimulus / Sensory Neurons Receive the Information and Transmit It to the CNS / CNS Receives the Information and a Response is Decided / Motor Neurons Transmit the Response to the Effectors / Effectors Carry Out the Response / A Response is Given (Motor or Secretory Response)
Light Rays, Reflected off Objects, Pass Through the Cornea, the Aqueous Humour, the Pupil, and Then Reach the Lens. The Lens Changes the Shape to Focus Objects at Different Distances (Accommodation). In the Retina, the Image is Inverted. Photoreceptors in the Retina Convert the Image into Nerve Impulses, Which Are Carried by the Optic Nerve to the Cerebral Cortex.
Myopia: Eyeball is Too Long, Images are Focused in Front of the Retina, Convex Lens / Hypermetropia: Eyeball is Too Short, Images are Focused Behind, Convex Lens / Astigmatism: Irregular Shaped Cornea, Lenses or Surgery / Cataracts: Crystalline Lens Becomes Opaque, Progressive Loss of Vision / Conjunctivitis: Inflammation of the Conjunctiva.
Involuntary Responses: Stimulus is Detected by a Receptor, Sensory Neurons Transmit Nerve Impulses to the Spinal Cord, Relay Neuron in the Spinal Cord Connects the Sensory Neuron to the Motor Neuron, Motor Neuron Carries the Response to a Muscle, the Muscle Carries Out the Response
Somatic NS: Involved in Voluntary Muscle Movement and Involuntary Reflex Acts, Connects the Sensory Receptor to the CNS and Musculoskeletal System / Autonomic Nervous System; Controls Unconscious Automatic Actions, Responds Through Motor Nerves: Sympathetic: Flight or Fight, Responds in Situations of Physical or Emotional Stress, Parasympathetic: Activities for Rest or Digestion.