LAB 6: SPINAL CORD AND REFLEXES

LAB 6: SPINAL CORD AND REFLEXES

External anatomy of the spinal cord

Meninges - three protective layers surrounding the spinal cord (Dura Mater, Arachnoid Mater, Pia Mater).

Dura mater - The tough, outermost membrane protecting the spinal cord.

Epidural space - the area between the dura mater and the vertebrae, containing fat and blood vessels.

Arachnoid mater - The middle layer of the meninges, containing cerebrospinal fluid (CSF).

Subarachnoid space - The area beneath the arachnoid mater, filled with CSF to cushion the spinal cord.

Cerebrospinal fluid - A clear liquid that protects and nourishes the spinal cord and brain. 

Pia mater - he thin, innermost layer of the meninges that directly covers and protects the spinal cord.

Neuron Structure

Dendrite - The branched extensions of a neuron that receive signals from other neurons and transmit them to the cell body.

Cell Body - The main part of a neuron that contains the nucleus and organelles necessary for cell function.

Axon - A long, thin structure that transmits electrical impulses away from the cell body to communicate with other neurons or muscles.

Synaptic Knob - The terminal end of an axon where neurotransmitters are released to send signals to the next neuron or muscle cell.

Myelin - A fatty substance that surrounds and insulates axons, allowing for faster electrical signal transmission.

Node of Ranvier - Small gaps in the myelin sheath where the axon is exposed, allowing nerve impulses to jump between nodes and speed up conduction.

Reflex arc

Sensory receptor - A specialized structure that detects changes in the environment (stimuli) such as pain, heat, or pressure.

Sensory/afferent neuron - A neuron that carries sensory information from the receptor to the spinal cord.

Integration center - The part of the spinal cord or brain where sensory input is processed, and a response is generated.

Motor neuron -A neuron that carries commands from the central nervous system to muscles or glands.

Effector - The muscle or gland that responds to the motor neuron signal, leading to movement or secretion.

Reflexes

Patellar or knee-jerk - A simple stretch reflex that causes the leg to extend when the patellar tendon is tapped. 

Flexor or withdrawal reflex - A reflex that causes an automatic withdrawal of a body part in response to a painful stimulus (e.g., pulling your hand away from a hot object).

Crossed-extensor reflex - A reflex that occurs in the opposite limb to help maintain balance when the withdrawal reflex is activated (e.g., stepping on a sharp object and shifting weight to the other foot).

Anatomy of a horizontal spinal section

Anterior median fissure - A deep groove on the anterior (front) side of the spinal cord that partially divides it into two halves.

Central canal - A small, fluid-filled channel running through the center of the spinal cord, containing cerebrospinal fluid.

Gray matter - The butterfly-shaped inner region of the spinal cord that contains neuron cell bodies and processes sensory and motor signals.

Posterior (dorsal) horn - The part of the gray matter that receives sensory input from the body.

Lateral horn (T1-L2 only) - A section of gray matter present only in the thoracic and upper lumbar spinal cord, involved in autonomic functions.

Anterior (ventral) horn - The part of the gray matter that contains motor neurons, which send signals to muscles.

White matter - The outer layer of the spinal cord that contains nerve fibers (axons) transmitting signals between the brain and body.

Anterior (ventral) column -A section of white matter that carries motor signals from the brain to the spinal cord.

Posterior (dorsal) column - A section of white matter that carries sensory information about touch and body position to the brain.

Lateral column - A region of white matter that carries both motor and sensory information.

Spinal nerve anatomy

Posterior (dorsal) root - The part of a spinal nerve that carries sensory signals from the body to the spinal cord.

Posterior (dorsal) root ganglion - A cluster of sensory neuron cell bodies located on the dorsal root of the spinal nerve.

Anterior (ventral) root - The part of a spinal nerve that carries motor signals from the spinal cord to muscles.