Recording-2025-02-19T19:20:10.011Z

Overview of the Spinal Cord and Reflexes

Central Canal

• 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).

Structure of the Spinal Cord

• 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 and Neuronal Pathways

• Spinal Nerves: Carry sensory and motor information; consist of sensory neurons.

• Ganglion: A cluster of neuron cell bodies in the peripheral nervous system.

Neural Pathways

• 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).

Types of Motor Neurons

• Autonomic Motor Neurons: Controls involuntary responses (e.g., heart, visceral organs).

• Somatic Motor Neurons: Control voluntary movements (e.g., to skeletal muscles).

Reflexes

Definition and Function

• 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.

Components of a Reflex Arc

1. Sensory Receptor: Detects the stimulus (e.g., pain, heat).

2. Sensory Neuron: Sends sensory information to the spinal cord.

3. Interneurons: Relay and process signals between sensory and motor neurons.

4. Motor Neuron: Sends impulses to effectors (muscles or glands).

5. Effector Organ: Carries out the response (muscle contraction or gland secretion).

Types of Reflexes

• 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.