Intro to PNS

What are the two types of cells in the nervous system?

• Neurons: excitable cells that are specialized for rapid communication of information

• Glial: cells that provide structural and functional support for neurons

What are the components of a neuron

• Cell body: an area containing the nucelus and various organelles; Maybe also be known as the soma or the perikaryon

• Neurites: Numerous thin, tube-like structures projecting from the soma

  • Two types: Dendrites and axons

• Axon terminals

What does the CNS consist of?

Brain and spinal cord

What does the PNS include?

1. ganglia

2. nerves and their branches

3. end organs

   1. sensory receptors

   2. neuromuscular junction

   3. visceromotor endings

What are the two divisions of the Nervous system and describe them

Somatic Division:

• Soma, Gr. Body

• sensory and motor

• innervation of skin, tendons, joints, and skeletal muscles

Visceral Division:

• Viscera, Gr. Guts

• Sensory/motor (autonomic)

• innervation of smooth muscle, cardiac muscle, organs and glands

How many pairs of cranial nerves and spinal nerves are there?

12 pairs of cranial nerves

31 pairs of spinal nerves (cervical, thoracic, lumbar, sacral, coccygeal)

How are spinal nerves numbered?

In cervical:

• spinal nerves are numbered according to the vertebra below

All other spinal nerves: Numbered according to vertebra above

What are spinal nerves formed by? How are they divided?

Formed by union of anterior and posterior nerve roots

• Anterior (ventral) roots = contains primarily motor axons leaving the spinal cord

• Posterior (dorsal) roots = contain primarily sensory axons entering the spinal cord

The spinal nerve divides into:

• ventral ramus: supplies the anterolateral body wall and the extremities

• Dorsal Ramus: supplies structures of the back (excluding extrinsic back musculature)

What are the two types of neurons?

Sensory (afferent neuron) (centripetally)

Motor (efferent neurons) (centrifugally)

Both have somatic and visceral divisions

What is a reflex?

An involuntary, steroeotypeed motor response to a particular sensory stimulus. Mediated by chains of neurons called reflex arc

What are the different nerve fibers a spinal nerve has?

General somatic efferent (GSE) fibers

General somatic afferent (GSA) fibers

General visceral efferent (GVE) fibers

General visceral afferent (GVA) fibers

What is a ganglia? how are they classified?

A collection of neuron cell bodies within PNS;

Classified as Sensory, Autonomic, or enteric

What are the two ganglias in the head?

1. cranial sensory ganglia

   1. sensory neuron cell bodies (somatic/visceral)

2. Cranial parasympathetic ganglia

   1. Visceral motor neuron cell bodies (postganglionic)

What are the body ganglias?

What does the PNS-somatic division do?

innervates skin, tendons, joints, and skeletal muscles

What are somatic plexuses? What are the three major plexus?

nerve fibers from different spinal nerves (levels) intermingling within plexuses; Give rise to individaul NAMED PERIPHERAL NERVES that contains axons from more than one spinal nerve

Cervical: C1-C4

• for neck region and posterior scalp

Brachial Plexus (C5-T1)

• for upper extremities

Lumbosacral plexus (L1-S4)

• for lower extremeties

What is a dermatone? What is the paradox here?

where Sensory neurons within a single spinal nerve innervate a specific area of skin;

The dermatomal pattern DOES NOT CORRESPOND with the cutaneous distribution of named peripheral nerves

What is a myotome?

muscle mass innervated by somatic motor fibers from one spinal nerve (Muscles are commonly innervated by motor neurons from more than one spinal nerve; however certain levels may play a more primary role)

What does the PNS’s visceral division do?

Innervates smooth muscle, cardiac muscle, organs, and glands

List out the visceral plexuses; describe their similarities

Includes:

1. esophagel plexus

2. cardiac plexus

3. pulmonary plexus

4. prevertebral plexus (assocaited with abdominal aorta and lateral wall of pelvis)

• Contains visceral sensroy and visceromotor (autonomic) fibers;

• Visceromotor fibers exit the paravertebral ganglia or anterior spinal rami and travel through splanchnic nerves to reach visceral plexus

What are the two divisions of the autonomic nervous system

Sympathetic:

• controls energy expending processes

• short preganglionic fibers, long postganglionic fibers

Parasympathetic:

• controls energy conserving processes

• long preganglionic fibers, short postganglionic fibers

Where does the SNS preganglionic neurons originate? Where are the postgang. found?

Pre: originates in the thoracic and upper lumbar spinal cord (T1-L2)

Post: located in paravertebral and prevertebral ganglia

Where does the PNS preganglionic neurons originate? Where are the postgang. found?

PRe: brain stem and sacral (S2-S4) spinal cord

Post: cranial parasympathetic ganglia and in walls of organs

Describe the visceral sensory pathways and a consequence in their organization

• The visceral sensory pathways use the same pathway as the visceromotor fibers run in the opposite direction;

• Visceral Afferents of the SNS may carry pain related information. The CNS can misinterpret this information as coming from somatic structures = refered pain

Describe the ENteric Nervous system and its plexus