Chapter 13: The spinal cord and spinal nerves

Question 1

How does the spinal cord and brain contribute to homeostasis.

Answer 1

providing quick, reflexive responses
to many stimuli. The spinal cord is the pathway for sensory input to the brain and motor output
from the brain.

Question 2

Describe the external cross anatomy of the spinal cord.

***The spinal cord extends from the medulla oblongata of the brain to the superior border of the second
lumbar vertebra.

Answer 2

The spinal cord is roughly cylindrical, but slightly flattened anterior/posterior. It extends from the medulla to the superior border of L2. The length ranges from 42-45 cm and is approximately 2 cm in diameter. There is a cervical enlargement from C4-T1 and a lumbar enlargement from T9-T12. The conus medullaris is the tapered inferior end. The filum terminale is an extension of the pia mater that anchors the cord to the coccyx. The cauda equina is the roots of spinal nerves angling inferiorly in the vertebral canal from the end of the spinal cord. 31 pairs of spinal nerves leave the cord at regular intervals through the intervertebral foramina.

Question 3

list the connective tissue coverings/ encircles the spinal cord from superficial to deep
** MASTER BOTH IMAGES 13.1 FROM TEXT

Answer 3

(1)dura mater
(2) arachnoid mater
(3) pia mater

Question 4

Where is the epidural space locate?

Answer 4

space between the dura mater and the wall of the vertebral canal.

Question 5

where is the subdural space found?

Answer 5

Between the dura mater and the arachnoid mater is a thin
subdural space

Question 6

denticulate ligaments

Answer 6

protect the spinal cord against sudden displacement that could result in shock.

Question 7

space between the arachnoid and pia matter.

Answer 7

subarachnoid space, which contains
shock-absorbing cerebrospinal fluid.

Question 8

List and name the four major plexuses of the spinal cord.

Answer 8

Cervical plexus (C1–C5)
Brachial plexus (C5- T1)
Lumbar plexus (L1-L4)
Sacral plexus (L4–S4):

Question 9

Know here the Posterior median
sulcus and the anterior median fissure is in the spinal cord.

Question 10

Internal Anatomy of the Spinal Cord

Answer 10

*Posterior white
column
*Lateral white
column
*Anterior white
column
* Posterior gray horn
*Lateral gray horn
*Anterior gray horn

Question 11

good to know

Answer 11

The posterior gray horn contains axons of sensory neurons and cell bodies of interneurons; the lateral gray horn contains cell bodies of autonomic motor neurons; and the anterior gray horn contains
cell bodies of somatic motor neurons

Question 12

There are 31 pairs of spinal nerves.
(8 12 5 5 1)

Answer 12

cervical nerves 8 C1–C8)
thoracic nerves 12 (T1–T12),
lumbar nerves 5 (L1–L5),
sacral nerves 5 (S1–S5)
coccygeal nerves 1 (Co1)

Question 13

What does the white matter of spinal cord contain?

Answer 13

consists primarily of bundles of myelinated
axons of neurons.

Question 14

H- shaped gray matter

Answer 14

consists of dendrites and cell bodies of neurons, unmyelinated axons, and neuroglia.

Question 15

A mixed nerve

Question 16

Three layers of connective tissue wrappings protect axons:

Answer 16

Endoneurium surrounds individual axons, perineurium surrounds bundles of axons (fascicles), and epineurium surrounds an entire nerve.

Question 17

Branches (rami) of spinal nerves

Answer 17

**Dorsal ramus:
serves dorsal portion
of the trunk
**Meningeal branches:
branch from spinal
nerves, then re-enter the
intervertebral foramen
** Ventral ramus:
serves ventral portion
of the trunk and
upper/lower limbs

Question 18

plexuses

Answer 18

Anterior/ventral ramus:
Axons form networks by joining with axons from adjacent nerves to form plexuses. exception T2 T12 are
intercostal/thoracic nerves.

Question 19

cervical plexuses(C1- C5)

Answer 19

supplies the skin and
muscles of the head, neck, superior portion of
the shoulders and chest, and diaphragm.

Question 20

Brachial plexuses (see slides)

Answer 20

** Provides almost the entire nerve supply to the shoulders and upper limbs.
**branches into
Risk Takers Dont Cautiously Behave
-Roots Trunks Branches Cords
Divisions

Question 21

Lumbar plexus

Answer 21

Provides nerve supply to the
anterolateral abdominal wall, external
genitalia, and parts of the lower limbs.

Question 22

Sacral plexus

Answer 22

Provides nerve supply to the buttocks,
posterior part of the perineum,
posterior thigh, and lower limbs.

Question 23

Whats a dermatome

Answer 23

A dermatome is an area of
skin that is mainly supplied
by a single spinal nerve.

Question 24

Whats a reflex?

Answer 24

a fast, involuntary,
unplanned response to a particular stimulus.
*Reflexes help maintain homeostasis.
*The gray matter of the spinal cord serves as the integrating center for spinal reflexes.

Question 25

Reflex interactions/arcs

Answer 25

*ipsilateral.sensory to posterior gray horn-intergration -motor through anterior gray horn
*contralateral. sensory- dorsal horn- opposite posterior gray horn.

Question 26

stretch reflex

Answer 26

A stretch reflex causes contraction of a muscle that has been stretched.

Question 27

A tendon reflex

Answer 27

A tendon reflex causes relaxation of the muscle attached to the stimulated tendon.

Question 28

A flexor reflex

Answer 28

A flexor reflex causes withdrawal of a limb to avoid injury or pain.

Question 29

The crossed extensor reflex

Answer 29

maintains balance during a withdrawal reflex