Spinal Cord: Anatomy, Spinal Tracts & Pathways, Somatic Reflexes, Animation

Spinal cord

The communication gateway between the brain and spinal nerves, extending from the brainstem to the level of upper lumbar vertebrae.

Meninges

Three membranes that enclose and protect the spinal cord.

Cauda equina

A bundle of spinal nerve roots descending within the spinal canal before exiting, located in the lower lumbar and sacral regions.

Gray matter

The butterfly-shaped central core of the spinal cord containing cell bodies and dendrites of neurons.

White matter

The surrounding tissue of the spinal cord made of bundles of axons that conducts information up and down the cord.

Spinal tracts

High-speed cables in the spinal cord that carry specific types of information in a one-way traffic between the spinal cord and the brain.

Ascending tracts

Tracts that conduct sensory information up to the brain.

Descending tracts

Tracts that convey motor instructions down the spinal cord.

Contralaterally

When information is transmitted from one side of the body to the other side of the brain.

Ipsilaterally

When information is conducted on the same side all the way through the spinal cord.

Mixed nerves

Spinal nerves that contain both sensory and motor fibers.

Dorsal root

The part of the spinal nerve through which sensory fibers enter the spinal cord.

Ventral root

The part of the spinal nerve through which motor fibers exit the spinal cord.

First-order neurons

Neurons that detect stimuli and transmit signals to the spinal cord.

Second-order neurons

Neurons that synapse with first-order neurons and ascend to the brainstem or thalamus.

Third-order neurons

Neurons that conduct sensory information to the sensory cortex.

Upper motor neuron

A neuron that starts in the motor cortex or brainstem and is part of the motor pathway.

Lower motor neuron

A neuron that continues from the brainstem or spinal cord to the effector organ in the motor pathway.

Somatic reflexes

Fast, involuntary responses of skeletal muscles that do not require input from the brain.

Reflex arc

The pathway involved in a reflex action, composed of a somatic receptor, sensory neuron, interneuron, motor neuron, and effector muscle.

Contralateral pathways

Pathways that involve coordination and responses from both sides of the body during complex reflexes.