Transcript Spinal Cord and Reflexes

Spinal Cord
and Reflexes
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).
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.

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).

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.

Other Reflexes

Visceral reflexes
◦ Controlled by the brain stem.
◦ Responsible for heart and
breathing rate, blood pressure,
digestion, sneezing, coughing, and
vomiting.