Spinal Cord and Spinal Nerves

Spinal Cord and Spinal Nerves

Carefully read the text on each slide before proceeding to the next.

Image credit: SciTech Daily

The Spinal Cord

The spinal cord is a continuation of the brain stem. It carries information to and from the brain.

Image credit: National Cancer Institute

Multiple Select

Without a spinal cord, a person would be unable... (Check ALL that apply)

• To feel sensation

• To move

• To think

Composition of the Spinal Cord

• The spinal cord is gray on the inside and white on the outside.

• The central gray area is called gray matter and is composed primarily of cell bodies and interneurons.

• The outer white area is called white matter. It is composed primarily of myelinated axons.

• Image credit: histology.leeds.ac.uk

Multiple Choice

What color is myelin?

Nerve Tracts

• Axons in the white matter are grouped together into nerve tracts. For example:

• Pain fibers are grouped together in a particular tract.

• Motor fibers are grouped in other tracts.

• Image credit: KenHub

Multiple Choice

Which part of a neuron transmits signals away from the cell body?

• Dendrites

• Axons

• Nucleus

• Schwann's cells

There are three types of nerves in the human body:

• Sensory nerves are made only of sensory neurons. They deliver information to the Central Nervous System (CNS).

• Motor nerves are made only of motor neurons. They transmit information from the brain and spinal cord (CNS) to the body.

• Mixed nerves contain both motor and sensory neurons. Most of the nerves in your body fall in this category.

Multiple Choice

Which type of neuron (not nerve fiber) enables you to type on your keyboard?

• Sensory

• Motor

• Mixed

Spinal Nerves

• Each nerve is attached to the spinal cord by two roots: the dorsal root and the ventral root.

• Sensory nerve fibers travel to the spinal cord through the dorsal root.

• Motor nerve fibers leave the spinal cord through the ventral root and are distributed to muscles and glands.

• Image credit: Wikipedia

Multiple Choice

Sensations from the body are transmitted through which side of the spinal cord?

• Dorsal

• Ventral

• Medial

Reflexes

Most of the activities that you do every day occur very rapidly and without any conscious control. They are involuntary responses to stimuli from your environment. We call these responses reflexes.

Reflex Arcs

A knee-jerk reaction is an example of a reflex arc. These are the steps involved:

1) A sensory receptor is stimulated by tapping the tendon posterior to the knee.

2) An afferent neuron (sensory, “affect”) carries the impulse to the spinal cord.

3) An efferent neuron (motor, “effect”) carries the impulse to the muscles of the leg.

4) The muscles of the lower leg contract and move the leg in an upward movement. 

Image credit: BioNinja

Multiple Choice

The brain is directly involved in reflexes.

• True

• False

Multiple Choice

If a person has part or all of a body limb amputated, why might they experience “phantom sensations” in that area, such as itching or pain, even though it is no longer a part of their body?

• The efferent, or motor, nerve fiber has not been damaged.

• The wound did not heal properly.

• The remaining afferent, or sensory, nerve fiber is still intact.

• Ghosts.

The Peripheral Nervous System

All of the nerves outside the CNS comprise the peripheral nervous system (PNS). It can be divided into the cranial nerves and the spinal nerves. Both kinds of nerves are classified from where the nerve fiber originates (from the cranium or from the spine).

Cranial nerves originate directly from the brain, not the spinal cord. When it comes to cranial nerves, the name of the nerve indicates the specific anatomical area serviced by that nerve.

Image credit: TeachMeAnatomy.com

Multiple Choice

Which cranial nerve would transmit sensations from your eye?

• Accessory

• Facial

• Optic

• Olfactory

The Autonomic Nervous System

In addition to afferent nerves (bring sensory information from the body to the CNS) and efferent nerves (bring motor information from the CNS to the skeletal muscles), the PNS also contains the autonomic nervous system (ANS). It is composed of nerves that supply the organs (viscera) and glands. The ANS is further divided into the sympathetic and parasympathetic nervous systems.

Carefully read through the flowchart on the next slide before continuing on.

The Autonomic Nervous System

The sympathetic nervous system is activated during periods or stress or times when the person feels threatened in some way.

The parasympathetic nervous system is most active during quiet, non-stressful conditions.

Take your time to look at all the different roles of each system on the next slide before continuing on.

Image credits: Buzzle.com

Multiple Choice

Which system would be active if you were being chased by a bear?

• Sympathetic

• Parasympathetic

Multiple Choice

Which system would be active if you were lounging with your family after Thanksgiving dinner?

• Sympathetic

• Parasympathetic

Let's review...

Carefully read each question before selecting the best answer.

Multiple Choice

Which statement is correct?

• Gray matter is composed of myelinated cell bodies.

• White matter is composed of myelinated axons.

• Gray matter is composed of axon terminals.

• White matter is composed of dendrites.

Multiple Choice

Most nerves in the human body are...

• sensory nerves

• motor nerves

• mixed nerves

Multiple Choice

Motor nerves transmit signals from the CNS to the skeletal muscles via the…

• Dorsal Roots

• Reflex Arcs

• Ventral Roots

Multiple Choice

Reflexes are...

• Voluntary

• Involuntary

• Sympathetic

• Autonomic

Multiple Choice

The sympathetic and parasympathetic nervous systems comprise the...

• Central Nervous System

• Peripheral Nervous System

• Autonomic Nervous System

Open Ended

What is something from this lesson that you are having a hard time understanding?