Spinal cord and Peripheral nervous system Spinal cord

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 http: //www. bayareapainmedical. com/wspin 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 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