The central canal is a fluid-filled space in the center of the spinal cord.
The fluid in this space is called cerebrospinal fluid (CSF).
Gray Matter: Contains neuron cell bodies and is organized into:
Dorsal Horn (posterior)
Lateral Horn
Ventral Horn (anterior)
White Matter: Contains myelinated axons and organized into columns:
Dorsal Column
Ventral Column
Lateral Column
Spinal Nerves: Carry sensory and motor information; consist of sensory neurons.
Ganglion: A cluster of neuron cell bodies in the peripheral nervous system.
The ascending pathway carries sensory information to the brain (via interneurons).
The descending pathway carries motor commands from the brain to effectors (muscles or glands).
Autonomic Motor Neurons: Controls involuntary responses (e.g., heart, visceral organs).
Somatic Motor Neurons: Control voluntary movements (e.g., to skeletal muscles).
Reflex: An involuntary reaction in response to a stimulus, which allows faster reaction than conscious thought.
Most reflexes occur in the spinal cord or brain stem rather than higher brain centers.
Sensory Receptor: Detects the stimulus (e.g., pain, heat).
Sensory Neuron: Sends sensory information to the spinal cord.
Interneurons: Relay and process signals between sensory and motor neurons.
Motor Neuron: Sends impulses to effectors (muscles or glands).
Effector Organ: Carries out the response (muscle contraction or gland secretion).
Stretch Reflex: e.g., knee-jerk reflex (involuntary muscle contraction in response to stretching).
Withdrawal Reflex: e.g., flexor reflex (removal of a limb from a painful stimulus); involves sensory receptors as pain receptors.