FINAL ch 12

Question 1

The major link between the brain and the peripheral nervous system. It’s responsible for integrating some reflexes as well:

Answer 1

SPINAL CORD

Extends from the foramen magnum to the second lumbar vertebra.

It is segmented:
`Cervical
`Thoracic
`Lumbar
`Sacral

Question 2

How many pairs of spinal nerves are there?

Answer 2

31

Question 3

What enlargement of the spinal cord supplies the upper limbs?

Answer 3

CERVICAL

ENLARGEMENT

Question 4

What enlargement of the spinal cord supplies the lower limbs?

Answer 4

LUMBOSACRAL

ENLARGEMENT

Question 5

What is the CONUS MEDULLARIS?

Answer 5

The tapered inferior end of the spinal cord.

This is immediately inferior to the lumbosacral enlargement.

Question 6

What do we call the origins of the spinal nerves extending inferiorly from the lumbosacral enlargement and conus medullaris?

Answer 6

CAUDA (tail)

EQUINA (horse)

Question 7

What do we call the connective tissue membranes surrounding the spinal cord and brain?

Answer 7

MENINGES

Question 8

This layer of meninges is the most superficial, thickest, and is continuous with the epineurium of the spinal nerves:

Answer 8

DURA MATER (tough mother)

It forms a sac, often called the THECAL SAC, which surrounds the spinal cord. The sac attaches to the rim of the foramen magnum and ends at the level of the second sacral vertebra.

Question 9

This meningeal layer is thin and wispy, and is deep to the dura mater:

Answer 9

ARACHNOID MATER (spiderlike cobwebs)

The space between this membrane and the dura mater is the SUBDURAL SPACE and contains only a very small amount of SEROUS fluid.

Question 10

The deepest meningeal layer. It is bound tightly to the surface of the brain and spinal cord, and forms the FILUM TERMINALE and DENTICULATE LIGAMENTS:

Answer 10

PIA MATER (pie-yah) (affectionate)

Question 11

A connective tissue strand that anchors the conus medullaris and the thecal sac to the first coccygeal vertebra, limiting their superior movement:

Answer 11

FILUM

TERMINALE

Question 12

Between the arachnoid mater and the pia mater is the ? which contains weblike strands of the arachnoid mater, blood vessels, and cerebrospinal fluid:

Answer 12

SUBARACHNOID SPACE

Question 13

Connective tissue septa extending form the lateral sides of the spinal cord to the dura mater:

Answer 13

DENTICULATE
LIGAMENTS

The denticulate (small teeth) ligaments attach to the dura mater by toothlike processes between the exits of the cervical and thoracic spinal nerves.

The denticulate ligaments limit the lateral movement of the spinal cord.

Question 14

This “space” contains nerve roots, blood vessels, areolar connecive tissue and fat. Anesthesia is injected here…

Answer 14

EPIDURAL space.

Question 15

This “space” has a small amount of serous fluid in it:

Answer 15

SUBDURAL space.

Question 16

This “space” has cerebrospinal fluid and blood vessels within web-like strands of arachnoid tissue:

Answer 16

SUBARACHNOID space.

Question 17

What are the 2 deep clefts partially separating the 2 halves of the spinal cord called?

Answer 17

1. ANTERIOR
   MEDIAN
   FISSURE (the visible “line” leading from the gray matter heading toward the naval-side)
2. POSTERIOR
   MEDIAN
   SULCUS (the visible “line” and “bump” leading from the gray matter heading toward the back of the back)

These seemingly divide the vertebral column into 2 equal halves.

Question 18

What are the 3 columns, or FUNICULI, that each half of the white matter of the spinal cord is organized into?

Answer 18

1. VENTRAL column (anterior)
2. DORSAL column (posterior)
3. LATERAL column (side)

Each of these columns is subdivided into TRACTS (FASICULI or PATHWAYS)

Question 19

A collection of axons INSIDE the CNS is called a ?

Answer 19

TRACT

Tracts have different myelination that nerves and lack the extensive connective tissue of nerves. Individual axons ascending to the brain or descending from the brain are usually grouped together within TRACTS. Axons within a given tract carry basically the same type of information. Ex: one ascending tract carries action potentials related to pain and temperature sensations, whereas another carries action potentials related to light touch.

Question 20

A collection of axons OUTSIDE the CNS is called a ?

Answer 20

NERVE

Question 21

The central gray matter of the spinal cord is organized into HORNS. What are the names they are divided into?

Answer 21

1. Posterior (dorsal) horn: thin
2. Anterior (ventral) horn: larger
3. Lateral (associated with the ANS): small

Question 22

What are the connections between the left and the right halves of the spinal cord called?

Answer 22

COMMISSURES

The gray and white commissures contain axons that cross from one side of the spinal cord to the other.

Question 23

This is located in the center of the gray commissure and helps circulate CSF associated with the ventricular system:

Answer 23

CENTRAL CANAL

Question 24

Spinal nerves arise from the spinal cord as “rootlets” and then combine to form these:

Answer 24

ROOTS

The DORSAL (posterior) root has a GANGLION (swelling).
The VENTRAL (anterior) root doesn't. 
The 2 roots merge laterally and form the spinal nerve.

Question 25

These have collections of cell bodies of the unipolar sensory neurons forming the dorsal roots of the spinal nerves:

Answer 25

DORSAL ROOT GANGLION The axons do not synapse in the dorsal root ganglion but pass through the root into the posterior horn of the spinal cord gray matter. The axons either synapse with interneurons in the posterior horn or pass into the white matter and ascend in the spinal cord.

Question 26

Where are the motor neuron cell bodies located in the spinal cord?

Answer 26

The Anterior and Lateral horns of the spinal cord gray matter. Multipolar somatic motor neurons are in the anterior horn. Autonomic neurons are in the lateral horn. Axons of the motor neurons form ventral roots and pass into spinal nerves.

Question 27

What is the basic functional unit of the nervous system?

Answer 27

REFLEX ARC It's the reflex arc because it is the simplest portion capable of receiving a stimulus and producing a response

Question 28

What are the 5 basic components of a reflex arc?

Answer 28

1. sensory receptor 2. sensory neuron 3. interneuron 4. motor neuron 5. effector organ, which responds w/a reflex action The simplest reflex arcs do not involve interneurons.

Question 29

What do we call reflexes that don't have any interneurons?

Answer 29

MONOSYNAPTIC reflex. Ex: Stretch reflex is monosynaptic.

Question 30

Variety of reflexes...

Answer 30

Some integrate within the spinal cord, some within the brain. Some involve excitatory neurons yielding a response, some involve inhibitory neurons that prevent an action. Some have higher brain center influences, such as suppression or exaggeration of reflex responses.

Question 31

What do muscles do in response to a stretching force applied to them?

Answer 31

They contract. This is a STRETCH reflex.

Question 32

What do we call encapsulated specialized muscle fibers with noncontractile centers?

Answer 32

MUSCLE SPINDLES These are the sensory receptors of the stretch reflex. Each spindle consists of 3-10 small, specialized skeletal muscle fibers. The fibers are contractile only at their ends and are innervated by specific motor neurons called GAMMA motor neurons.

Question 33

These neurons originate from the spinal cord and control the sensitivity of the muscle spindle cells:

Answer 33

GAMMA MOTOR NEURONS The term "gamma" refers to motor neurons with small-diameter axons. Additional sensory neurons wrap around the noncontractile centers of the muscle spindle cells. These sensory neurons synapse with motor neurons of the spinal cord called ALPHA motor neurons.

Question 34

What is the name of the motor neurons that the axons of the sensory neurons synapse with in the spinal cord?

Answer 34

ALPHA MOTOR NEURONS These neurons innervate the muscle (effector organ) in which contains the muscle spindle. Alpha neurons have the largest diameter of axons.

Question 35

Sudden muscle stretch results in...

Answer 35

1. Muscle spindles detect stretch of the muscle. 2. Sensory neurons conduct action potentials to the spinal cord. 3. Sensory neurons synapse directly with alpha motor neurons. 4. Alpha motor neurons conduct action potentials to the muscle, causing it to contract and resist being stretched.

Question 36

What prevents contracting muscles from applying excessive tension to tendons?

Answer 36

GOLGI TENDON REFLEX

Question 37

What are the encapsulated nerve endings that have at their ends numerous branches with small swellings adjacent to bundles of collagen fibers in tendons?

Answer 37

GOLGI TENDON ORGANS These are located near the muscle-tendon junction. As a muscle contracts, the attached tendons stretch, resulting in increased tension in the tendon. The increased tension stimulates action potentials in the sensory neurons from the Golgi tendon organs. Golgi tendon organs have a high threshold and are sensitive only to intense stretch. These prevent damage to tendons that could b caused by excessive tension. They produce a sudden relaxation of the muscles.

Question 38

This reflex's function is to remove a limb or another body part from a painful stimulus:

Answer 38

WITHDRAWAL REFLEX There is reciprocal innervation: a phenomenon that reinforces the efficiency of the withdrawal reflex. (Reciprocal innervation is also involved in the stretch reflex) It causes relaxation (inhibition) of extensor muscle when flexor muscle contracts.

Question 39

What do we call the phenomenon that reinforces the efficiency of the withdrawal reflex? It causes relaxation of extensor muscles when flexor muscles contract:

Answer 39

RECIPROCAL | INNERVATION

Question 40

What is another reflex associated with the withdrawal reflex... it initiates extension of the opposite lower limb of the limb experiencing the withdrawal reflex?

Answer 40

CROSSED EXTENSOR REFLEX This helps prevent falls by shifting the weight of the body from the affected to the unaffected limb.