Chapter 12 Part 1- Spinal Cord

Question 1

Where does the spinal cord reside

Answer 1

Extends from foreman magnum to about L2

Question 2

Spinal cord anatomy

Answer 2

Cervical, thoracic, lumbar, sacral
-31 pairs of spinal nerves
- two enlargements (cervical supplies upper limbs and lumbar supplies lower limbs)
-conus medullaris - tapered inferior end
-cauda equina- spinal nerves extending beyond medullaris

Question 3

Meninges of spinal cord

Answer 3

Connective tissue membranes surrounding spinal cord and brain
Dura mater - tough outer layer
Arachnoid Mater - thin and wispy
Pia mater - thin, bound tightly to surface of brain and spinal cord

Question 4

Filum terminale

Answer 4

Formed by pia mater, this anchors the spinal cord to the coccyx and the denticulate ligaments that attach the spinal cord to the dura matter

Question 5

Spaces in meninges

Answer 5

Epidural - contains blood vessels, areolar connective tissue and fat
Subdural- beneath dura
Subarachnoid - CSF fluid and blood vessels within

Question 6

Layer of meninges

Answer 6

Epidural space
Dura mater
Subdural space
Arachnoid mater
Subarachnoid space
Pia mater

Question 8

Denticulate ligaments

Answer 8

Points in the arachnoid mater where nerves exit the spinal cord

Question 9

Arrangement of matter in spinal cord

Answer 9

Gray matter (neuron, cell, cell bodies, dendrites, axons) is inside in a butterfly arranged in horns (anterior, posterior, and lateral)
The white matter is myelinated axons on the outside in ascending and descending columns -dorsal, ventral, and lateral (with nerve tracts)

Question 10

Commissures

Answer 10

Connect left and right halves of spinal cord. Grey has central canal.

Question 11

Roots

Answer 11

Spinal nerves arise from rootless to form roots.
Dorsal root has dorsal root ganglion (a collecting of unipolar sensory neuron cell bodies)
Motor neurons travel through ventral root

Question 12

Where do sensory neurons travel once out of the dorsal root

Answer 12

To the gray matter where they synapse with other neurons or interneurons

Question 13

Where do motor neurons travel once cell bodies live in the spinal cord

Answer 13

Reside in the anterior horn and lateral horn, then travels via the ventral root into spinal nerves

Question 14

Reflexes

Answer 14

Basic functional unit of nervous system and simplest portion capable of receiving a stimulus and producing a response. An automatic response to a stimulus that occurs without conscious thought.

Can be somatic (skeletal) or autonomic (homeostasis)

Question 15

Components of a reflex

Answer 15

Sensory receptor to detect
Sensory neurons to transmit
Interneuron - can be excitatory or inhibitory
Motor neuron
Effector organ- responds with reflex

Question 16

Major reflexes to know

Answer 16

Stretch
Golgi tendon
Withdrawal
Withdrawal with reciprocal innervation
Cross extensor

Question 17

Simplest type of somatic reflex

Answer 17

Stretch - no Interneuron

Question 18

Stretch reflex

Answer 18

Muscles contract in opposition to a stretching force (by means other than yourself (ex- physician tap))

Question 19

Gamma motor neurons

Answer 19

Regulate sensitivity of the muscle spindle so that reflex can still occur

Question 20

Receptor of stretch reflex

Answer 20

Muscle spindle; bundle of 3-10 small skeletal muscle cells contractile only at their ends, that respond to stretch

Question 21

Stretching the muscle causes:

Answer 21

Stretch of spindle
Stimulation of sensory neurons travel through
Stimulation of alpha neurons at spinal cord
Alpha neurons stimulate muscle, causing contraction of the stretched muscle

Question 22

Example of stretch reflex

Answer 22

Patellar reflex - doctor tapping below knee

Question 23

Golgi tendon reflex

Answer 23

Prevents contracting muscles from applying excessive force on tendons. Produces a sudden relaxation of the muscles

Question 24

Receptor of Golgi tendon reflex

Answer 24

Golgi tendon organ. Encapsulated nerve ending in tendon near muscle that detect excessive stretch and tension placed on the tendon.

Question 25

Example of Golgi tendon reflex

Answer 25

Weight lifter suddenly drops heavy weight.

Question 26

Process of Golgi tendon reflex

Answer 26

1. Muscle contracts and tendon is stretched, increasing tension 2. If a great amount of tension is applied, sensory neurons of Golgi are stimulated 3. Sensory neurons stimulate inhibits neurons to releases inhibitory NTs 4. Alpha motor neurons inhibited and relax

Question 27

Alpha motor neurons

Answer 27

Neurons in the spinal cord that are imbedded into skeletal muscle

Question 28

Withdrawal reflex

Answer 28

Function is to remove a body limb or other part away from a painful stimukus

Question 29

Withdrawal reflex subdivisions

Answer 29

Reciprocal - causes relaxation of antagonistic muscles Crossed extensor - causes extension of opposite limb

Question 30

Process of withdraw reflex

Answer 30

1. Step on tack and sensory neurons send input to spinal cord of CNS 2. Excitatory interneurons excite alpha neurons which tell muscle to remove limb 3. Collateral neurons tell brain but synapse on inhibitory interneurons in cord (reciprocal innervation)

Question 31

Receptor of withdrawal reflex

Answer 31

Pain receptors

Question 32

Crossed extensor reflex

Answer 32

Same scenario as withdrawal but sensory neurons create collateral branches that also synapses with excitatory interneurons in spinal cord that cross over white commissure fibers to gray matter and alpha neurons of the other side. Result is alpha motor neuron on side facing injury causes limb to be withdrawn and on other said, the neuron causes extension of other limb to maintain balance

Question 33

How many pairs of spinal nerves

Answer 33

31

Question 34

Where do spinal nerves exit

Answer 34

Through intervertebral foramina, except first pair and last four

Question 35

What regions form plexuses

Answer 35

Cervical, brachial, and lumbar

Question 36

Cervical plexus

Answer 36

C1-c4 -services head and neck structures

Question 37

Major nerve in cervical plexus

Answer 37

Phrenic nerve - from c3-c5 Innervates diaphragm and controls breathing

Question 38

Brachial plexus

Answer 38

C5-T1 Creates several branches (peripheral nerves) -axillary, radial, musculotaneous, ulnar, median

Question 39

Lumbosacral plexus

Answer 39

L1-S4 Serve lower limbs Major nerve— sciatic nerve

Question 40

What does thoracic vertebrae do in terms of spinal nerves

Answer 40

No plexuses.. supports the trunk of the body

Question 41

Peripheral nerves

Answer 41

Named nerves stemming from plexuses Consists of bundles of axons

Question 42

Organization of connective tissue in a peripheral nerve

Answer 42

Endoneurium - between bundles of axons Perineurium - surrounds bundles of axons to form fascicles Epineuarium - groups of fascicles are covered with this making up the entire nerve

Question 43

Numbers of spinal nerve organization

Answer 43

8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal

Question 44

Dermatomal map

Answer 44

Skin area map of sensory nerve distribution by letter and number