Spinal cord and Peripheral nervous system \

Spinal cord - Functions  Sensory and motor pathway

Reflex arc (spinal cord)  Reflex center –  Sensory receptor  Sensory neuron  Interneuron (association neuron)  Motor neuron (effector)  An effector organ

Spinal Cord Anatomy  Association neuron  Motor ecrd.html ecrd.html  Gray Matter – “butterfly” interneurons  White Matter – myelinated

Spinal cord Anatomy

Spinal Cord tracts  Sensory  1. Dorsal column 2. Spinothalamic  Ascending tracts  temperature, pressure, pain, light, touch

Spinal cord tracts continued Motor tracts 1. Corticospinal  Decending  Skeletal tone, voluntary muscle movement

Nerves attached to Sp. Cord  Dorsal Root Ganglia – bundle of sensory nerves  Ventral Root Ganglia – bundle of motor fibers

Peripheral Nervous system

Somatic Nervous System  Includes all nerves in the musculoskeletal system, sense organs  Receptor (receives impulse) to Effector (muscle fiber)

Autonomic Nervous System  Motor neurons that control internal organs (involuntary)  Innervate all organs  Two divisions of

Autonomic Nervous System  Sympathetic  “Fight or flight response”  Inhibits digestion  Pupils dilate  Accelerates heart rate  Increase breathing rate.  Parasympathetic  Normal state  Promotes digestion  Pupils constrict  Normal heartbeat  “feed and breed”

The Eye: Photoreceptor  Lens – refraction and focusing  Iris – controls entrance of light into eye  Pupil – window into the eye  Choroid – blood vessels, absorbs stray light

Eye anatomy continued  Sclera – white fiborous layer, protection  Humors –  Aqueous humor – between the cornea an lens  Viterous humor – fills large cavity, gelatinous material

Eye Anatomy continued  Ciliary body – holds lens in place  Retina – contains receptors  Cones – color vision  Rods – black and white vision  Optic Nerve

Rods and Cones Illustration

Eye Anatomy Continued  Optic Nerve – picks up impulse  Ciliary muscles – controls the shape of the lens  Accommodation –  Additional focusing power  Near object – ciliary muscle contracts, lens becomes round

Physiology of sight  Focusing – light rays bent by cornea, focus on the retina, refraction and inverted

Fields of VisionFields of Vision Illustration Refer to Lab on eye dissection

Cross section of head

Normal Vision 20/20  at a distance of 20 feet, you can read a certain line (labeled 20) on the chart and that your vision is normal.  20/40 -

Nearsightedness (myopic) Farsightedness (hyperopia)

Disorders of the Eye: Glaucoma – built up pressure in the eye due to lack of aqueous humor drainage

Vision of a person with Glaucoma

Cataracts- clouding of the lens