Spinal cord and Peripheral nervous system

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Spinal cord - FunctionsSensory 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

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Gray Matter – “butterfly” interneuronsWhite Matter – myelinated

Spinal cord Anatomy

Spinal Cord tractsSensory 1. Dorsal column

2. SpinothalamicAscending 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

P e rip he ra l N ervo u s S ys tem

S o m a tic

sym p ath tic N e rvo ussys tem

p a rasym p a the tic n e rvo ussys tem

A u ton o m ic N ervo ussys tye m

P N S

Somatic Nervous System Includes all nerves in the

musculoskeletal system, sense organsReceptor (receives impulse) to Effector

(muscle fiber)

Autonomic Nervous SystemMotor 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 20/20at 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