Peripheral Nervous System

Ganglia/ganglion

a cluster of nerve cells in the PNS

Reflex

involuntary immediate response to a stimulus (brain not involved)

What nerves make up the PNS?

nerves outside the CNS (i.e. not brain or spinal cord)

Afferent nerves

receive stimuli from receptors, head into the spinal cord; sensory

Efferent nerves

transmit information to effectors, out from the spinal cord; motor

Mechanical effectors

muscle action

Chemical effectors

glandular secretions

What is the basic function of the PNS?

to process incoming/outgoing information with stored information (memory)

neuroglial/glial cells

supportive functions

Astrocytes

nutrients/suppport

Mircroglial

immune support

Oligodendroglia/Schwann cells

axon insulation/myelination

Oligodendrocytes - CNS

Schwann cells - PNS

Ependymal cells

cells that line the spinal cord/brain central canal

Neurons

functional unit of the nervous system, electrical stimuli transmission

Collection of axons in the PNS is called ____

nerve

Perikaryon

cell bodies of neurons (includes nucleus and organelles)

Dendrites

sensory input, receive signals

Axons

transmit the exiting signal from neuron (either connects to an effector or another nerve)

What is the purpose of myelination?

increases the speed of signal transmission

What is the purpose of synaptic terminals?

release/uptake of neurotransmitters

Somatic nerves

• innervate somatic tissues - muscle, skin

• spinal reflex arc - involuntary control

Visceral nerves (autonomic)

• innervate visceral organs - smooth muscle, glands

• visceral reflex arc - involuntary

Dorsal root

afferent (sensory) fibers

Ventral root

efferent (mobile) fibers

Spinal nerve embryology

• neural crest cells - migrate to specific locations, grow back into CNS and out to tissues

• ectoderm

Interneuron

helps transmit signals, located within spinal cord gray matter

Spinal nerve reflex arc

• involuntary, immediate response to a stimulus

• brain not involved

  • sensory impulse from stimulus

  • afferent nerve

  • dorsal horn/roots of spinal cord

  • ventral root transmit

Cranial nerves

• roots are enclosed in the brain case

• fish, amphibians have up to 6

• amniotes have 10-12 (13?)

Cranial nerve I

• name: olfactory

• sensory

• function: smell

Cranial nerve II

• name: optic

• sensory

• function: sight

Cranial nerve III

• name: oculomotor

• motor

• function: eye movement, blinking

Cranial nerve IV

• name: trochlear

• motor

• function: eye movement

Cranial nerve V

• name: trigeminal

• sensory and motor

• function: face/cheek sensation, jaw movement

Cranial nerve VI

• name: abducens

• motor

• function: eye movement

Cranial nerve VII

• name: facial

• sensory and motor

• function: facial expressions, taste

Cranial nerve VIII

• name: vestibular

• sensory

• function: hearing, balance

Cranial nerve IX

• name: glossopharyngeal

• sensory and motor

• taste, swallowing

Cranial nerve X

• name: vagus

• sensory and motor

• function: viscera, diaphragm, GI tract, pharynx, heart rate

Cranial nerve XI

• name: spinal accessory

• motor

• function: shoulder/neck muscles

Cranial nerve XII

• name: hypoglossal

• motor

• function: hyoid muscle, tongue

Autonomic nervous system

• visceral activity - not voluntary control

• motor - cardiac/smooth muscle, glands, viscera (GI, urogenital, respiratory)

• sensory - BP, O2/CO2, body temperature, viscera activity

• visceral reflexes - maintains internal environment

Sympathetic division of the autonomic nervous system

• thoracolumbar - cell bodies in thoracic, lumbar spinal cord

• “fight or flight” response

  • increased HR, BP

  • decreased GIT

  • splenic contraction

  • dilate coronary arteries

  • mobilize glucose (gluconeogenesis)

  • dilate pupils

Parasympathetic division of the autonomic nervous system

• craniosacral - cell bodies in brain stem, sacral spinal cord

• cranial nerve - V, VII, IX, X

• “rest and digest” - restore body to resting state

  • increased digestion

  • decreased HR, BP

  • constrict coronary arteries

  • promote glycogen (glyconeogenesis)