Spinal Cord & Reflexes

Q: What is the spinal cord?

A: A long, tubular structure of nervous tissue that extends from the brainstem down through the vertebral column, transmitting nerve impulses between the brain and body.

Q: What are the main functions of the spinal cord?

A: To relay information between the brain and body and to coordinate reflexes.

Q: Where does the spinal cord begin and end?

A: It begins at the medulla oblongata and ends at the level of the first or second lumbar vertebra (L1–L2).

Q: What protects the spinal cord?

A: The vertebrae, meninges, and cerebrospinal fluid (CSF).

Q: What are the meninges of the spinal cord?

A: The dura mater, arachnoid mater, and pia mater.

Q: What is the epidural space?

A: The area between the dura mater and vertebral wall containing fat and blood vessels.

Q: What is the subarachnoid space?

A: The space between the arachnoid mater and pia mater that contains cerebrospinal fluid.

Q: What is the central canal of the spinal cord?

A: A small, CSF-filled canal running through the center of the spinal cord.

Q: What is gray matter in the spinal cord?

A: The butterfly-shaped inner region made of neuron cell bodies, dendrites, and unmyelinated axons.

Q: What is white matter in the spinal cord?

A: The outer region made up of myelinated axons organized into ascending and descending tracts.

Q: What are ascending tracts?

A: Nerve pathways that carry sensory information from the body to the brain.

Q: What are descending tracts?

A: Nerve pathways that carry motor commands from the brain to the body.

Q: What are spinal nerves?

A: Thirty-one pairs of mixed nerves that connect the spinal cord to specific regions of the body.

Q: How are spinal nerves numbered?

A: According to the vertebral region they emerge from—8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.

Q: What are the two roots of each spinal nerve?

A: The dorsal (posterior) root and the ventral (anterior) root.

Q: What is the dorsal root?

A: The root that carries sensory information into the spinal cord.

Q: What is found in the dorsal root ganglion?

A: The cell bodies of sensory neurons.

Q: What is the ventral root?

A: The root that carries motor signals from the spinal cord to muscles and glands.

Q: What is the difference between sensory and motor neurons in the spinal cord?

A: Sensory neurons bring information in through the dorsal root, and motor neurons send information out through the ventral root.

Q: What is a reflex?

A: An automatic, rapid response to a stimulus designed to protect the body or maintain homeostasis.

Q: What is a reflex arc?

A: The neural pathway through which a reflex occurs, involving sensory input, integration, and motor output.

Q: What are the five components of a reflex arc?

A: Receptor, sensory neuron, integration center, motor neuron, and effector.

Q: What is the receptor in a reflex arc?

A: A structure that detects a stimulus.

Q: What is the sensory neuron in a reflex arc?

A: The neuron that transmits the signal from the receptor to the spinal cord.

Q: What is the integration center in a reflex arc?

A: The region within the spinal cord or brain that processes the information.

Q: What is the motor neuron in a reflex arc?

A: The neuron that carries impulses from the CNS to the effector.

Q: What is the effector in a reflex arc?

A: The muscle or gland that performs the reflex action.

Q: What is a monosynaptic reflex?

A: A reflex involving only one synapse between a sensory and motor neuron, such as the patellar (knee-jerk) reflex.

Q: What is a polysynaptic reflex?

A: A reflex involving one or more interneurons between the sensory and motor neurons, allowing more complex responses.

Q: What is the patellar reflex?

A: A stretch reflex that causes the quadriceps muscle to contract when the patellar tendon is tapped.

Q: What is the withdrawal reflex?

A: A protective reflex that pulls a body part away from a painful stimulus.

Q: What is the crossed extensor reflex?

A: A reflex that helps maintain balance by extending the opposite limb when one is withdrawn.

Q: What is the plantar reflex?

A: A reflex where the toes curl downward when the sole of the foot is stroked in adults.

Q: What is the Babinski sign?

A: An abnormal response in adults where the toes flare upward, indicating possible CNS damage.

Q: What are spinal reflexes?

A: Reflexes processed in the spinal cord without direct involvement of the brain.

Q: What are cranial reflexes?

A: Reflexes processed by the brainstem, such as blinking or swallowing.

Q: What is the function of reflexes in homeostasis?

A: They help maintain stable internal conditions by providing rapid, automatic responses to changes in the body or environment.

Q: What is paralysis?

A: The loss of voluntary motor function, often caused by spinal cord injury or damage to motor neurons.

Q: What is paraplegia?

A: Paralysis of the lower limbs resulting from spinal cord injury in the thoracic or lumbar regions.

Q: What is quadriplegia?

A: Paralysis of all four limbs resulting from spinal cord injury in the cervical region.

Q: What is the cauda equina?

A: A bundle of spinal nerves extending beyond the end of the spinal cord resembling a horse’s tail.

Q: What is the conus medullaris?

A: The tapered, cone-shaped end of the spinal cord.

Q: What is the filum terminale?

A: A fibrous extension of the pia mater that anchors the spinal cord to the coccyx.

Q: What is spinal shock?

A: Temporary loss of all reflexes and motor function below the site of spinal cord injury.

Q: What is a dermatome?

A: An area of skin supplied by a single spinal nerve.

Q: What is a plexus?

A: A network of intersecting spinal nerves that serve specific regions of the body.

Q: Name the four main spinal nerve plexuses.

A: Cervical, brachial, lumbar, and sacral plexuses.

Q: What is the phrenic nerve?

A: A nerve arising from the cervical plexus that controls the diaphragm and is essential for breathing.

Q: What is the sciatic nerve?

A: The largest nerve in the body, arising from the sacral plexus, that controls movement and sensation in the lower limb.