PNS ANATOMY AND PHYSIOLOGY

The more attractive nervous system

Introduction

• Tommy, MS1

• Joey, MS1

Learning objectives

1. Students will be able to relate dermatomes and sensory neurons and explain how a dermatome map can be used to locate injury to a nerve root or spinal cord.

2. Students will be able to characterize the different reflexes arcs and their diagnostic value.

3. Students will be able to describe the cortico-spinal tract.4. *Students will learn how to evaluate the PNS using nerve

conduction studies (Dr. Kothari)

LO #1

Students will be able to relate dermatomes and sensory neurons and explain how a dermatome map can be used to

locate injury to a nerve root or spinal cord.

What are Dermatomes?

I love learning! <3

Dermatomes are…

•…the areas of skin supplied by a single nerve originating from a single spinal nerve root.

•Effectively, it’s a map of the body telling you where a sensory signal will enter the CNS.

Ow!

Let’s take a Step back

• The Peripheral nervous system

- All nerves outside of the CNS

- Somatic (Motor and Sensory) and Autonomic (Sympathetic and parasympathetic)

C0, coccygeal plexus

Afferent – From the periphery (towards the spinal cord)

-Sensory

Efferent – To the periphery (away from the spinal cord)

-Motor signals

Afferent

Efferent

Afferent and Efferent

Sensory Receptors

• The afferent root brings back nerve impulses from sensory receptors.

- This is a pathway for receiving signals from the outside world

To the dorsal root!

Sensory receptors• Sensory receptors are nerve endings of sensory nerves. The

ones in your skin (what we’re focusing on) detect everything from heat to pressure, to pain, etc.

• These sensations induce a series of action potentials (remember me?) from the sensory nerves back to the dorsal root of your spinal nerve.

• So…if you were to touch something dimpled, like a basketball, you will get one set of signals vs. if you touched a hot pumpkin spice latte (out now!)

Sensory receptors• Sensory receptors are nerve endings of sensory nerves. The

ones in your skin (what we’re focusing on) detect everything from heat to pressure, to pain, etc.

• These sensations induce a series of action potentials (remember me?) from the sensory nerves back to the dorsal root of your spinal nerve.

• So…if you were to touch something dimpled, like a basketball, you will get one set of signals vs. if you touched a hot pumpkin spice latte (out now!)

Clinical Connection

Let’s think about this.

We have these sensory receptors all over the body

Clinical Connection

Let’s think about this.

We have these sensory receptors all over the body

Each of these regions feeds sensory signals into one pair of spinal nerves

Clinical Connection

Let’s think about this.

We have these sensory receptors all over the body

Each of these regions feeds sensory signals into one pair of spinal nerves

As physicians, why would it be useful to know what region(s) relate to which spinal nerve?

An Example

• Herniated disc

Questions?

LO #2

• Students will be able to characterize the different reflexes arcs and their diagnostic value.

Applying PNS Structure & Function to Medicine

The Reflex Arc

1. Receptor - sense organ in skin, muscle, or other organ2. Sensory neuron - carries impulse towards CNS3. Interneuron - carries impulse within CNS4. Motor neuron - carries impulse away from CNS5. Effector - structure by which animal responds (muscle, gland, etc).

https://www.youtube.com/watch?v=wLrhYzdbbpE

https://www.youtube.com/watch?v=DJ3aOSd7Bg8