17 - The Spinal Cord and Spinal Nerves

Questions and Answers

What are the superior and inferior boundaries of the spinal dura mater?

The superior boundary is the foramen magnum of the occipital bone. The inferior boundary is the second sacral vertebra.

What are the three spinal meninges?

Dura mater, Arachnoid mater, Pia mater

What portion of the spinal cord connects with sensory and motor nerves of the upper limbs?

The cervical enlargement.

What is the difference between a horn and a column in the spinal cord?

A horn is an area of gray matter, and a column is a region of white matter. Signup and view all the answers

What is the comparison of various spinal cord segments?

Cervical (8 pairs), Thoracic (12 pairs), Lumbar (5 pairs), Sacral (5 pairs), Coccygeal (1 pair). Signup and view all the answers

Why are all spinal nerves classified as mixed nerves?

Because their posterior roots contain sensory axons and their anterior roots contain motor axons. Signup and view all the answers

Which spinal nerve branches serve the upper and lower limbs?

The anterior rami. Signup and view all the answers

Which is the only spinal nerve that does not have a corresponding dermatome?

C1. Signup and view all the answers

Why does complete severing of the spinal cord at level C2 cause respiratory arrest?

It prevents descending nerve impulses from reaching the phrenic nerve. Signup and view all the answers

What five important nerves arise from the brachial plexus?

Axillary, musculocutaneous, radial, median, ulnar nerves. Signup and view all the answers

What is the origin of the lumbar plexus?

The roots of spinal nerves L1-L4. Signup and view all the answers

What is the origin of the sacral plexus?

The anterior rami of spinal nerves L4-L5 and S1-S4. Signup and view all the answers

What are the position, origin, and destination of the anterior corticospinal tract?

Located on the anterior side of the spinal cord, originates in the cortex of cerebrum, and ends in the spinal cord. It is a motor tract. Signup and view all the answers

Why is this reflex a somatic reflex?

Because the effector is a skeletal muscle. Signup and view all the answers

What is myelitis?

Inflammation of the spinal cord. Signup and view all the answers

What is meningitis?

Inflammation of the meninges due to an infection. Signup and view all the answers

Where does sensory input travel?

Along the posterior columns and spinothalamic tracts. Signup and view all the answers

Where does motor output travel?

Along direct pathways and indirect pathways. Signup and view all the answers

What are white matter tracts in the spinal cord?

They are highways for nerve impulse propagation. Signup and view all the answers

What is a reflex?

A fast, predictable sequence of involuntary actions in response to changes in the environment. Signup and view all the answers

What are the three connective tissue coverings associated with spinal nerves?

Endoneurium, Perineurium, Epineurium. Signup and view all the answers

How are spinal nerves typically connected with the spinal cord?

By a posterior root and an anterior root. Signup and view all the answers

What are the functions of the spinal cord?

To propagate sensory impulses from receptors to the brain and motor impulses from the brain to effectors. Signup and view all the answers

Study Notes

Spinal Dura Mater

Superior boundary is located at the foramen magnum of the occipital bone.
Inferior boundary extends to the second sacral vertebra.

Spinal Meninges

Composed of three layers:
- Dura mater (outermost)
- Arachnoid mater (middle)
- Pia mater (innermost)

Spinal Cord Structure

Cervical enlargement connects with sensory and motor nerves of the upper limbs.
Gray matter is organized into horns; white matter is organized into columns.

Spinal Cord Segments

Comprises 31 pairs of spinal nerves:
- 8 pairs cervical
- 12 pairs thoracic
- 5 pairs lumbar
- 5 pairs sacral
- 1 pair coccygeal

Spinal Nerves

Classified as mixed nerves because they contain both sensory (posterior roots) and motor (anterior roots) axons.
Anterior rami serve the upper and lower limbs.
C1 is the only spinal nerve without a corresponding dermatome.

Clinical Significance

Complete severing of the spinal cord at level C2 causes respiratory arrest by interrupting nerve impulses to the phrenic nerve, vital for diaphragm contraction.
Five key nerves from the brachial plexus include axillary, musculocutaneous, radial, median, and ulnar.

Plexus Origins

Lumbar plexus originates from spinal nerves L1-L4.
Sacral plexus arises from anterior rami of spinal nerves L4-L5 and S1-S4.

Tracts in the Spinal Cord

Anterior corticospinal tract is a motor tract located on the anterior side of the spinal cord, originating in the cerebral cortex.
Sensory input travels via posterior columns and spinothalamic tracts.
Motor output is transmitted along direct and indirect pathways.

Reflexes

Defined as fast, involuntary responses to stimuli, involving skeletal or smooth muscle actions.
Somatic reflexes specifically target skeletal muscles.

Nervous System Coverings

Spinal nerves are wrapped in three connective tissue coverings:
- Endoneurium
- Perineurium
- Epineurium

Connections to Spinal Cord

Spinal nerves connect by posterior and anterior roots.

Functions of the Spinal Cord

Propagates sensory impulses from receptors to the brain and motor impulses from the brain to effectors via white matter tracts.

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Description

This quiz focuses on the anatomy of the spinal cord and spinal nerves. It covers essential topics such as the boundaries of the spinal dura mater and the layers of the spinal meninges. Perfect for students studying neuroanatomy or preparing for exams.