Chapter 12

Question 1

nucleus (spinal cord)

Answer 1

Gray part of spinal cord

Question 2

ganglion

Answer 2

is a nerve cell cluster or a group of nerve cell bodies outside of the central nervous system

Question 3

sensory neuron

Answer 3

sensory neurons are activated by physical modalities such as visible light, sound, heat, physical contact, etc., or by chemical signals for example in the case of smell or taste.

Question 4

sensory nerve

Answer 4

is an enclosed, cable-like bundle of sensory nerve fibers in the nervous system.

Question 5

motor neuron

Answer 5

is a nerve cell (neuron) whose cell body is located in the spinal cord and whose fiber (axon) projects outside the spinal cord to directly or indirectly control muscles

Motor neurons are efferent nerves

Question 6

motor nerve

Answer 6

x

Question 7

mixed nerve

Answer 7

contain both afferent and efferent axons, and thus conduct both incoming sensory information and outgoing muscle commands in the same bundle.

Question 8

crossed tract

Answer 8

A tract originating on one side and crosses the midline of the cord

Question 9

uncrossed tract

Answer 9

A tract originating on one side of the cord and terminates on the same side

Question 10

ipsilateral

Answer 10

belonging to or occurring on the same side of the body.

Question 11

contralateral

Answer 11

. relating to or denoting the side of the body opposite to that on which a particular structure or condition occurs.

Question 12

ascending tract

Answer 12

Sensory

the pathways by which sensory information from the peripheral nerves is transmitted to the cerebral cortex. In some texts, ascending tracts are also known as somatosensory pathways or systems.

Functionally, the ascending tracts can be divided into the type of information they transmit; conscious or unconscious:

Conscious tracts – Comprised of the dorsal column-medial lemniscal pathway, and the anterolateral system.

Unconscious tracts – Comprises of the spinocerebellar tracts.

In this article, we shall look at the anatomy of these tracts in some detail, and consider the clinical implications.

Question 13

descending tract

Answer 13

Motor

Question 14

Nerve vs. Neuron

Answer 14

However, they are closely related, as nerves are actually projections of neurons

Question 15

How many spinal nerves are there?

Answer 15

31 pairs of nerves exit from the cord

Question 16

What are there names?

Answer 16

8 cervical

12 thoracic

5 lumbar

5 sacral

Coccygeal

Question 17

What are the components of a spinal nerve?

Question 18

Describe the three meninges of the spinal column and the brain

Answer 18

a. DURA MATER: tough fibrous membrane
b. ARACHNOID: middle membrane ( web-like)
c. PIA MATER: inner delicate membrane

Question 19

Deeper description of the meninges of the spinal cord

Answer 19

Dura mater

Most superficial covering

Thickest membrane

Continuous with the dura matter of the brain (really the meningeal dura)

Separated from the periosteum of the vertebral canal by the epidural space

Arachnoid matter

Middle membrane

Subdural space separate the arachnoid mater from the dura mater

Pia matter

Deepest membrane

Tightly bound to the spinal cord

Subarachnoid space separate the arachnoid materfrom the pia mater

The subarcachnoid apace maintains cerebro spinal fluid

Question 20

Anatomy of Spinal Cord

Answer 20

Question 21

identify the dorsal, lateral and ventral white matter of the spinal cord

Answer 21

Question 22

identify the dorsal, lateral and ventral horns of the gray matter of the spinal cord, the commissures.

Answer 22

Question 23

Define plexus

Answer 23

a network of nerves or vessels in the body.

Question 24

Differentiate among endoneurium, perineurium, epineurium.

Answer 24

Endoneurium surrounds the Schwann cells, which, in turn, surrounds the axon

Perineurium surrounds fascicles

Epineurium binds fascicles to form a nerve

Question 25

The components of a reflex arc

Answer 25

sensory receptor

sensory neuron

interneuron

motor neuron

effector organ

Question 26

Reflex

Answer 26

an automatic response to a stimulus

occurs without conscious thought

they are homeostatic

there are monsynaptic and polysynapti reflexes

Question 27

Reflex arc

Answer 27

the basic functional unit of the nervous system because it is capsble of receiving a stimulus and producing a response

Question 28

What is the difference between a monosynaptic and a polysynaptic reflex?

Answer 28

When a reflex arc consists of only two neurons in an animal (one sensory neuron and one motor neuron), it is defined as monosynaptic. Monosynaptic refers to the presence of a single chemical synapse. In the case of peripheral muscle reflexes (patellar reflex, achilles reflex), brief stimulation to the muscle spindle results in contraction of the agonist or effector muscle.

By contrast, in polysynaptic reflex pathways, one or more interneurons connect afferent (sensory) and efferent (motor) signals. All but the most simple reflexes are polysynaptic, allowing processing or inhibition of polysynaptic reflexes within the spinal cord.
Polysynaptic reflexes because they connect with the brain via longitudinal neurones running the length of the spinal cord they can be inhibited by the conscious control of the brain eg. if you touch a hot object you can over ride the reflex and leave your hand ther if you wanted to!! In contrast you cannot suppress a monsynaptic reflex eg try stopping the knee jerk reflex.