Ch. 13 The Spinal Cord and Spinal Nerves

Self-Quiz Questions

Fill in the blank.

Because they contain both sensory and motor axons, spinal nerves are considered to be                 nerves.

mixed

Fill in the blank.

The five components of a reflex arc, in order from the beginning to the end, are (1) , (2) , (3) , (4) , and (5) .

sensory receptor, sensory neuron, integrating center, motor neuron, effector

True or False.

Gray matter of the spinal cord contains somatic motor and sensory nuclei, autonomic motor and sensory nuclei, and functions to receive and integrate both incoming and outgoing information. 

True.

True or False.

The epidural space is located between the wall of the vertebral canal and the pia mater.

False.

Which of the following is not true?

(1) Dermatomes are areas of the body that are stimulated by motor neurons exiting specific spinal nerves.

(2) The stretch reflex helps to maintain muscle tone.

(3) The Achilles reflex is an example of a stretch reflex.

(4) The abdominal reflex is used to diagnose problems with autonomic reflexes.

(5) Spinal nerves T2-T12 do not enter into the formation of a plexus.

(a) 1, 2, and 4                  (b)  2 and 5                    (c ) 1 and 4

(d) 1, 3, and 5                  (e) 1, 3, and 4

(c ) 1 and 4

(1) Dermatomes are areas of the body that are stimulated by motor neurons exiting specific spinal nerves.

and

(4) The abdominal reflex is used to diagnose problems with autonomic reflexes.

While identifying and labeling cadaver muscles, your lab partner accidentally pokes your finger with a pin. 

Place the following steps in the correct order from beginning to end of your body’s response.

(1) Impulses travel throughout anterior (ventral) root of spinal nerve(s).

(2) Sensory neuron relays impulse to spinal cord.

(3) Motor impulses reach muscles, causing withdrawal of the affected limb.

(4) Integrating centers interpret sensory impulses, and then generate motor impulses.

(5) Sensory receptor activated by stimulus.

(6) Impulse travels throughout posterior (dorsal) root of spinal nerve.

(a) 5, 3, 6, 4, 1, 2 (b) 5, 2, 1, 4, 6, 3 (c ) 5, 2, 6, 4, 1, 3

(d) 3, 5, 1, 2, 4, 6 (e) 2, 1, 5, 4, 6, 3

(c ) 5, 2, 6, 4, 1, 3

(5) Sensory receptor activated by stimulus.

(2) Sensory neuron relays impulse to spinal cord.

(6) Impulse travels throughout posterior (dorsal) root of spinal nerve).

(4) Integrating centers interpret sensory impulses, and then generate motor impulses.

(1) Impulses travel throughout anterior (ventral) root of spinal nerve(s).

(3) Motor impulses reach muscles, causing withdrawal of the affected limb.

The connective tissue surrounding each individual axon is

(a) endoneurium.               (b) epineurium.                      (c ) perineurium.

(e) fascicle.                       (e) arachnoid mater.

(a) endoneurium.

The tracts of the posterior column are involved in

(1) conscious proprioception.

(2) touch.

(3) pain.

(4) thermal sensations.

(5) pressure.

(6) vibration.

(a) 1, 2, 4, and 5              (b) 2, 4, and 6                 (c ) 1, 2, 5, and 6

(d) 3, 4, 5, and 6              (e) 1, 3, 5, and 6

(c ) 1, 2, 5, and 6

(1) conscious proprioception.

(2) touch.

(5) pressure.

and

(6) vibration.

Which of the following is a motor tract?

(a) posterior spinocerebellar                 (b) lateral spinothalamic 

(c ) anterior spinocerebellar                  (d) lateral corticospinal

(e) posterior column

(d) lateral corticospinal

Cutting the posterior root of a spinal nerve would

(a) interfere with the circulation of cerebrospinal fluid.

(b) impair motor control of skeletal muscles.

(c ) interfere with the ability of the brain to transmit motor impulses.

(d) impair motor control of organs.

(e) interfere with the flow of sensory impulses.

(e) interfere with the flow of sensory impulses.

Which of the following statements is false?

(a) The two main spinal cord sensory paths are the spinothalamic and anterior columns.

(b) The spinothalamic tracts convey impulses for sensing pain, temperature, itching, and tickling.

(c ) Direct pathways convey nerve impulses that program automatic movements, help coordinate body movements with visual stimuli, maintain skeletal muscle tone and posture, and contribute to equilibrium.

(e) The direct pathways are motor pathways.

(a) The two main spinal cord sensory paths are the spinothalamic and anterior columns.

Which of the following are true?

(1) The anterior (ventral) gray horns contain cell bodies of neurons that cause skeletal muscle contraction.

(2) The gray commissure connects the while matter of the right and left sides if the spinal cord.

(3) Cell bodies of autonomic motor neurons are located in the lateral gray horns.

(4) Sensory (ascending) tracts conduct motor impulses down the spinal cord.

(5) Gray matter in the spinal cord consists of cell bodies of neurons, neuroglia, unmyelinated axons, and dendrites of interneurons and motor neurons.

(a) 1, 2, 3, and 5              (b) 2 and 4                  (c ) 2, 3, 4, and 5

(d) 1, 3, and 5                  (e) 1, 2, 3, and 4

(d) 1, 3, and 5

(1) The anterior (ventral) gray horns contain cell bodies of neurons that cause skeletal muscle contraction.

(3) Cell bodies of autonomic motor neurons are located in the lateral gray horns.

and

(5) Gray matter in the spinal cord consists of cell bodies of neurons, neuroglia, unmyelinated axons, and dendrites of interneurons and motor neurons.

What’s a stretch reflex?

• a reflex resulting in the contraction of a skeletal muscle when it is stretched

• acts as a feedback mechanism to control muscle length by causing muscle contraction

• maintains proper muscle tone

What’s a tendon reflex?

• operates as a feedback mechanism to control muscle tension by causing muscle relaxation when muscle force becomes too extreme

• protects the tendon and muscle from damage due to excessive tension

What’s a flexor (with-drawal) reflex?

Polysynaptic reflex initiated in response to a painful stimulus.

What’s a crossed extensor reflex?

A balance-maintaining reflex.

What’s an intersegmental reflex arc?

Occurs when sensory nerve impulse travels up and down the spinal cord, thereby activating several motor neurons and more than one effector.

What’s a contralateral reflex arc?

Sensory impulses enter on one side of the spinal cord and motor impulses exit on the opposite side.

What’s an ipsilateral reflex arc?

Motor nerve impulses exit the spinal cord on the same side that sensory impulses entered the spinal cord.

What are muscle spindles?

Receptors that monitor changes in muscle length.

What is tendon (Golgi tendon) organs?

Receptors that monitor changes in muscle tension.

What’s a reciprocal innervation?

A neural circuit that coordinates body movements by causing contraction of one muscle and relaxation of antagonist muscles or relaxation of a muscle and contraction of the antagonists.

What’s a monosynaptic reflex?

Reflex arc that consists of one sensory and one motor neuron.

What’s a polysynaptic reflex?

Reflex pathway that contains sensory neurons, interneurons, and motor neurons.

What’s a cervical enlargement?

Area of the spinal cord from which nerves to and from the upper limbs arise.

What’s a lumbar enlargement?

Area of the spinal cord from which nerves to and from the lower libs arise.

What’s a central canal?

Space within the spinal cord filled with cerebrospinal fluid.

What are denticulate ligaments?

Extending the length of the spinal cord, these pia mater thickenings fuse with the arachnoid mater and dura mater and help to protect the spinal cord from shock and sudden displacement.

What’s a cauda equina?

The roots from the nerves that arise from the inferior part of the spinal cord but do not leave the vertebral column at the same level as they exit the cord.

What’s a meningeal branch?

Spinal nerve branch that supplies vertebrae, vertebral ligaments, blood vessels of the spinal cord, and meninges.

What’s a pia mater?

Thin transparent connective tissue composed of interlacing bundles of collagen fibers and some elastic fibers adhering to the spinal cord’s surface.

What’s an arachnoid mater?

Avascular covering of spinal cord composed of delicate collagen fivers and some elastic fibers.

What’s a dura mater?

Superficial spinal cord covering of dense, irregular connective tissue.

What’s a posterior (dorsal) root?

Contains sensory neuron axons and conducts impulses from the peripheral receptors into the spinal cord.

What’s an anterior (ventral) root?

Contains motor neuron axons and conducts impulses from the spinal cord to the peripheral organs and cells.

What’s a posterior (dorsal) ramus?

Spinal nerve branches that serve the deep muscles and skin of the posterior surface of the trunk.

What’s an anterior (ventral) ramus?

Spinal nerve branches that serve the muscles and structures of the upper and lower limbs and the lateral and ventral trunk.

What’s plexus?

The joining together of the anterior rami of adjacent nerves.

What’s a filum terminale?

An extension of the pia mater that anchors the spinal cord to the coccyx.

What’s a cervical plexus?

• provides the nerve supply of the skin and muscle of the head, neck, and superior part of the shoulders and chest

• formed by the anterior rami of C1-C4 with some contribution by C5

• phrenic nerve arises from this plexus

• injury to this plexus can affect breathing

What’s a brachial plexus?

• provides the entire nerve supply of the shoulders and upper limbs

• formed by the anterior rami of C5-C8 and T1

• median nerve arises from this plexus

What’s a lumbar plexus?

• provides the nerve supply of the anterolateral abdominal wall, external genitals, and part of the lower limbs

• formed by the anterior rami of L1-L4

• femoral nerve arises from this plexus

What’s a sacral plexus?

• supplies the buttocks, perineum, and lower limbs

• formed by the anterior rami of L4-L5 and S1-S4

• sciatic nerve arises from this plexus

What’s a coccygeal plexus?

Formed by anterior rami of S4-S5 and coccygeal nerves.