BIO25 Ch.14: Spinal Cord and Spinal Nerves Flashcards

Flashcards to review the anatomy and physiology of the spinal cord and spinal nerves.

What are the major functions of the spinal cord and spinal nerves?

Structural and functional link between brain and rest of body; spinal reflexes.

Where does the spinal cord extend from?

Extends inferiorly from the brain's medulla through the vertebral canal.

What are the four parts of the spinal cord?

Cervical, thoracic, lumbar, and sacral.

What do the neurons in the cervical enlargement innervate?

Neurons innervating upper limbs.

What do the neurons in the lumbar enlargement innervate?

Neurons innervating lower limbs

What is a nerve?

Cablelike bundle of axons.

What are the connective tissue wrappings of a nerve?

Epineurium, perineurium, and endoneurium.

How many pairs of spinal nerves are there?

31 pairs.

What is the difference between the posterior and anterior roots of a spinal nerve?

Posterior root contains sensory neurons; anterior root contains motor neurons.

What type of nerves are spinal nerves classified as?

Mixed nerves.

What protects the spinal cord?

Bone, meninges, and cerebrospinal fluid.

What canal does the spinal cord pass through?

Vertebral canal.

What does each spinal nerve exit through?

Intervertebral foramen.

What are the spinal cord meninges?

Pia mater, arachnoid mater, and dura mater.

What is the subarachnoid space?

Area deep to arachnoid through which CSF flows.

What does the epidural space house?

Houses adipose, areolar connective tissue, blood vessels.

What is a lumbar puncture used for?

Obtaining CSF for medical diagnosis.

Where does the adult spinal cord end?

Adult spinal cord ends at L1.

Where is the spinous process of L4 located?

Highest points of the iliac crests.

What is gray matter made of?

Neuron cell bodies, dendrites, unmyelinated axons, and glial cells.

What projects from the center of the spinal cord?

Posterior horns, anterior horns, and lateral horns.

What do the posterior horns house?

Axons of sensory neurons and cell bodies of interneurons.

What do the anterior horns house?

Cell bodies of somatic motor neurons.

What do the lateral horns innervate?

Smooth muscle, heart, glands.

What is white matter composed of?

Myelinated axons to and from the brain.

What are the two categories of general sense receptors?

Somatic sensory and visceral sensory.

What do tactile receptors detect?

Detect characteristics of an object.

What do proprioceptors detect?

Detect stretch in joints, muscles, tendons.

What do visceral sensory receptors detect?

Detect changes in an organ?

What are the categories of sensory pathways?

Somatosensory and viscerosensory pathways.

What do somatosensory pathways carry signals from?

Skin, muscles, joints

What do viscerosensory pathways carry signals from?

Viscera

What is the Neuron Chain in the Sensory Pathway?

Primary, secondary, and tertiary neurons.

Where does the primary neuron relay signals from, in the anterolateral pathway?

Skin to spinal cord

Where does the secondary neuron relay signals from, in the anterolateral pathway?

Spinal cord to thalamus.

Where does the tertiary neuron relay signals from, in the anterolateral pathway?

Thalamus to cerebral cortex

What neurons are included in motor pathways?

Upper and lower motor neurons.

Where is the upper motor neuron?

Motor cortex, cerebral nucleus, or brainstem nucleus.

Where is the lower motor neuron?

Cranial nerve nucleus or spinal cord anterior horn.

What may spinal cord injuries leave individuals?

Paralyzed and unable to perceive sensations.

What may prompt use of steroids after spinal cord injury do?

May preserve muscle function

What does the Posterior (dorsal) Ramus innervate?

muscle and skin of the back

What does the Anterior (ventral) Ramus innervate?

anterior and lateral trunk, upper limb, lower limb

What are rami communicantes?

small branches of autonomic fibers that extend between spinal nerve and sympathetic trunk ganglion

What are the four main nerve plexuses?

cervical, brachial, lumbar, and sacral plexuses.

Which spinal nerves form the intercostal nerves?

T1-T11

What forms the cervical plexus?

anterior rami of C1–C4.

What forms the brachial plexus?

anterior rami of C5–T1.

What forms the lumbar plexus?

anterior rami of L1–L4.

What forms the sacral plexus?

anterior rami of L4–S4.

What does the lumbar plexus innervate?

thigh muscles, abdominal wall.

What muscles do anterior division nerves tend to innervate?

flexor muscles

What muscles do posterior division nerves tend to innervate?

extensor muscles

How are minor Brachial Plexus Injuries treated?

rest

How are severe Brachial Plexus Injuries treated?

nerve grafts or transfers

How can a Radial Nerve Injury occur?

fractures or injuries to lateral elbow

What symptoms are caused by Radial Nerve Injury?

paralysis of extensor muscles of forearm, wrist, fingers; anesthesia along posterior arm, forearm, part of hand

How can the Posterior Cord (axillary and radial nerves) be injured?

improper use of crutches

How can the Median Nerve be compressed?

carpal tunnel syndrome

What symptoms are caused by Median Nerve Injury?

paralysis of thenar muscles, lateral lumbricals; anesthesia in part of hand

How can the Ulnar Nerve be injured?

fractures or dislocations of elbow

What symptoms are caused by Ulnar Nerve Injury?

paralysis of most intrinsic hand muscles; sensory loss on medial hand

How can the Superior Trunk (C5–C6) be injured?

excessive separation of neck and shoulder

How can the Inferior Trunk (C8–T1) be injured?

arm excessively abducted

What are reflexes?

rapid, preprogrammed, involuntary responses of muscles or glands to a stimulus

What are the four main properties of a reflex?

A stimulus is required to initiate a reflex, Response is rapid, The response is preprogrammed, The response is involuntary

What is a reflex considered?

a survival mechanism

What is a reflex arc?

neural pathway responsible for generating the response

What does a reflex arc include?

sensory receptor, effector, and neural wiring

What are the five steps involved in a reflex?

Stimulus activates a sensory receptor, The sensory neuron transmit a nerve signal to CNS, Information from the nerve signal is processed in the integration center by interneuron, The motor neuron transmits a serve signal CNS to effector, The effector responds to nerve signal from the motor neuron

What structures can be the reflex integration center?

spinal cord or brain

What can the effector be in a reflex?

skeletal muscle or cardiac muscle, smooth muscle, a gland

What is the difference between monosynaptic or polysynaptic reflexes?

sensory neurons synapse directly with motor neurons or are there interneurons in the reflex arc

What is the full extent of the spinal cord?

Spinal cord extends from the medulla oblongata to L1/L2 vertebrae.

What is the significance of the cervical and lumbar enlargements of the spinal cord?

The cervical enlargement corresponds with innervation of the upper limbs and the lumbar enlargement corresponds with the innervation of the lower limbs.

Describe the arrangement of the connective tissue layers of a nerve.

Epineurium surrounds the entire nerve, perineurium surrounds fascicles of axons, and endoneurium surrounds individual axons.

What is the functional difference between the posterior and anterior roots of the spinal cord?

The posterior root contains sensory axons entering the spinal cord, and the anterior root contains motor axons exiting the spinal cord.

Describe the arrangement and characteristics of the three meningeal layers protecting the spinal cord.

The pia mater is the innermost layer, directly adhering to the spinal cord; the arachnoid mater is the middle layer with a web-like structure; and the dura mater is the outermost, tough layer.

Why is a lumbar puncture typically performed in the lower lumbar region?

A lumbar puncture is typically performed below the L1/L2 level (around L4) to avoid damaging the spinal cord.

Describe the functions of the posterior, anterior, and lateral horns of the spinal cord gray matter.

Posterior horns receive sensory information, anterior horns contain motor neuron cell bodies, and lateral horns (present in T1-L2) contain autonomic motor neuron cell bodies.

What is the main functional difference between tactile receptors and proprioceptors?

Tactile receptors detect touch and pressure, while proprioceptors detect body position and movement.

Describe the role of each neuron in a typical three-neuron sensory pathway.

The primary neuron carries sensory information from the receptor to the spinal cord, the secondary neuron relays the signal to the thalamus (or cerebellum), and the tertiary neuron carries it from the thalamus to the cerebral cortex.

What type of signals does Anterolateral Pathway carry?

Signals related to crude touch, pressure, pain, and temperature.

What are the general locations of the upper and lower motor neurons?

The upper motor neuron originates in the brain, and the lower motor neuron extends from the spinal cord to the muscle.

How might steroids, antibiotics, and neural stem cells be used in treating spinal cord injuries?

Steroids may help preserve muscle function, antibiotics reduce infection risk, and neural stem cells may potentially regenerate CNS axons.

Compare the areas innervated by the posterior ramus, anterior ramus, and rami communicantes.

The posterior ramus innervates the muscles and skin of the back, the anterior ramus innervates the anterior and lateral trunk and the limbs, and the rami communicantes carry autonomic fibers.

Name the four major nerve plexuses and their spinal nerve origins.

Cervical plexus (C1-C4), brachial plexus (C5-T1), lumbar plexus (L1-L4), and sacral plexus (L4-S4).

What are crutch palsy and carpal tunnel syndrome, related to the brachial plexus?

Crutch palsy: injury to the posterior cord (axillary and radial nerves) from improper use of crutches. Carpal Tunnel: Compression of median nerve.

Define a reflex and its key characteristics.

A reflex is a rapid, preprogrammed, involuntary response to a stimulus.

What is the role of the 'integration center' in a reflex arc?

The integration center is a component of the reflex arc where the sensory signal is processed to generate an appropriate motor response.

Compare and contrast monosynaptic and polysynaptic reflexes.

In a monosynaptic reflex, sensory neurons directly synapse on motor neurons. Polysynaptic reflexes involve one or more interneurons between the sensory and motor neurons.

What are the potential consequences of spinal cord injuries?

May lead to paralysis and sensory loss.

What is the fundamental role of the spinal cord and spinal nerves?

Provide a structural and functional link between the brain and the rest of the body.

What is the pia mater?

A delicate layer adhering to spinal cord

What is the arachnoid mater?

A web-like layer, external to pia mater

What is the dura mater?

Tough, outermost layer

What is the specific function of the lateral horns in the spinal cord?

Houses cell bodies of autonomic motor neurons

What are the two main categories of sensory receptors associated with the spinal cord?

Somatic sensory receptors and Visceral sensory receptors

Where do motor pathways begin and what are the minimum neuronal components?

Starts in brain and include at least two neurons

How do the spinal nerves exit the spinal cord?

Divided into posterior and anterior roots