1. Spinal Cord and Reflexes

2. Spinal Cord
Begins at the base of the brain and extends to the disk between the first and second lumbar vertebrae (just below the ribs).

3. Anatomy of the Spinal Cord
Surrounded by bone, meninges, and cerebrospinal fluid (CSF).
Core of gray matter (interneurons, cell bodies) surrounded by white matter (mainly myelinated nerve fibers).
Central canal passes through the center, is filled with CSF.

4. The Reflex Arc Automatic, involuntary response to stimuli.
1. Receptor (receives stimulus) to sensory neuron
2. Sensory to interneuron to motor neuron.
3. Motor neuron sends message to effector(s).

5. Spinal Reflexes
Stretch reflex: ensures muscle maintains proper length.
Muscle fibers stretch, message sent from sensory to motor neurons, stimulate muscles to contract.
Ex: knee-jerk reflex, postural reflexes
Withdrawal reflex: painful stimulus causes withdrawal.

7. Other Reflexes Controlled by the brain stem.
Visceral reflexes
Controlled by the brain stem.
Responsible for heart and breathing rate, blood pressure, digestion, sneezing, coughing, and vomiting.