Neuroanatomy Exam Ii Somatosensation

Front 1

Where does the spinal cord begin and end?

Back 1

Begins at foramen magnum and ends at L2

Front 2

What is the cauda equina?

Back 2

The space between the end of the SC and the end of the dural sheath at S2 that is filled with dorsal and ventral roots.

Front 3

What happens, in general, to the size of the cord as you go superior to inferior?

Back 3

It gradually decreases in diameter.

Front 4

What are the two enlargements of the spinal cord and what are they associated with?

Back 4

Cervical enlargement and the Lumbosacral enlargement, they are associated with supply to upper and lower limbs, respectively.

Front 5

What are the numbers of the spinal nerves?

Back 5

C1-8
T1-12
L1-5
S1-5
Co

Front 6

What is a dermatome?

Back 6

A dermatomal map that indicates the sensory distribution of each spinal nerve (because SC segments are related to areas of skin and muscle)

Front 7

What kind of matter makes up the cenral and peripheral portions of the spinal cord? What do these types of matter represent?

Back 7

Central: Gray matter, represents cell bodies.
Peripheral: White matter, represents fibers.

Front 8

What are the names of the clefts that separate the 2 halves of the spinal cord?

Back 8

Anterior median fissure
Posterior median sulcus

Front 9

What are the 3 sections of white matter? What are they associated with?

Back 9

Dorsal:
Sensory neuron fibers
Ventral:
Motor neuron fibers
Lateral Column:
Sympathetic neuron fibers

Front 10

What are the 3 sections of gray matter? What are they associated with?

Back 10

Dorsal Horn:
Sensory cell bodies
Anterior Horn:
Cell bodies of skM neurons
Lateral Horn:
Cell bodies of sympathetic fibers (between T1 and L3)

Front 11

What about the gray matter on the lateral areas of spinal cord between S2 and S4?

Back 11

Contains parasympathetic fibers (cell bodies?) but don't form a distinct lateral horn.

Front 12

What do you call the nerves entering the spinal cord?

Back 12

Dorsal roots, afferent, sensory neurons.

Front 13

What do the neurons of the dorsal root do? Where are the cell bodies of these neurons?

Back 13

They enter the spinal cord and project into the posterior horn where they synapse with interneurons or ascend or descend the SC. The cell bodies are in the dorsal root ganglia.

Front 14

What do you call the nerves exiting the spinal cord?

Back 14

Ventral roots, efferent, motor neurons.

Front 15

Where are cell bodies of ventral root located? Be specific about cell type.

Back 15

Anterior horn (somatic neurons)
Lateral area (autonomic neurons)

Front 16

When the dorsal root and ventral root combine it forms what?

Back 16

Spinal nerves

Front 17

What are the levels of organization of a nerve?

Back 17

endoneurium (surrounds each axon and schwann cell), perineurium (surrounds several axons forming fascicles), epineurium (surrounds fascicles to form nerves)

Front 18

Which layer of a nerve is continuous with dura mater?

Back 18

epineurium

Front 19

What are the 5 ascending pathways?

Back 19

Lateral Spinothalamic Tract
Dorsal Column
Spinocerebellar tract
Spinoreticular tract
Spinomesencephalic tract

Front 20

What are the 2 ascending pathways involved in conscious sensation?

Back 20

Lateral Spinothalamic Tract
Dorsal Column

Front 21

What are the 3 ascending pathways involved in unconscious sensation?

Back 21

Spinocerebellar tract
Spinoreticular tract
Spinomesencephalic tract

Front 22

How many neurons make up the ascending conscious sensation pathways? And where do the pathways terminate and what happens when they do?

Back 22

2-3
Thalamus
Another nerve goes from thalamus to the cerebral cortex.

Front 23

What kind of information is transmitted by the Lateral Spinothalamic tract?

Back 23

pain and heat info

Front 24

Where do the nerves from the Lateral Spinothalamic tract cross over? Fibers travel Contralateral or ipsilateral in spinal cord?

Back 24

Almost immediately after entering the spinal cord. Contralateral.

Front 25

What kind of information is transmitted by the Dorsal Column?

Back 25

Touch, pressure, and conscious proprioception

Front 26

Where do fibers of the Dorsal Column cross? Do the fibers travel contralaterally or ipsilaterally in the spinal cord?

Back 26

They cross at the midlane at the medulla and they travel ipsilaterally up the spinal cord.

Front 27

What sensation is a combination of both the spinothalamic pathway and the dorsal column?

Back 27

Light touch

Front 28

What sensations are transmitted by the Spinocerebellar tract?

Back 28

Unconscious proprioception

Front 29

Where do the fibers of the Spinocerebellar tract terminate?

Back 29

Cerebellum, NOT thalamus

Front 30

Where do the fibers from the spinocerebellar tract cross? Do the travel contralaterally or ipsilaterally in the spinal cord?

Back 30

The fibers in the spinocerebellar tract do NOT cross, and they therefore travel ipsilaterally in the spinal cord and remain ipsilateral.

Front 31

What sensations are transmitted by the fibers of the spinoreticular tract?

Back 31

Arousal and Withdrawl

Front 32

Where do fibers from the spinoreticular tract terminate?

Back 32

The reticular formation

Front 33

Where do the fibers of the spinoreticular tract cross? Do the fibers travel contralaterally or ipsilaterally up the spinal cord?

Back 33

The fibers cross almost immediately after entering the spinal cord and therefore travel contralaterally up the spinal cord (they follow the same path as spinothalamic tract)

Front 34

What sensations are transmitted byt e fibers of the spinomesencephalic tract?

Back 34

pain

Front 35

Where do the fibers from the spinomesencephalic tract terminate?

Back 35

The superior colliculus - which deals with vision and turning eyes toward painful stimulus.

Front 36

Where do fibers of the spinomesencephalic tract cross? Do they travel contralaterally or ipsilaterally up the spinal cord?

Back 36

The fibers cross almost immediately after entering the spinal cord. Therefore, the fibers travel contralaterally up the spinal cord. These fibers follow the same pathway as the spinothalamic tract.

Front 37

What kind of information is transmitted by the descending pathways?

Back 37

Motor information of the somatic motor system

Front 38

What kind of neurons are involved in the descending pathway?

Back 38

Upper motor neurons and lower motor neurons.

Front 39

Where do upper motor neurons of the descending pathway originate? Do they cross? What do they do?

Back 39

Have cell bodies in motor cortex, cerebellum, or brainstem. They cross at the level of the medulla. They synapse with lower motor neurons in the brainstem or spinal cord.

Front 40

Where do lower motor neurons of the descending pathway originate? Do the cross over? What do they do?

Back 40

The cell bodies are in the anterior horn of the spinal cord or the cranial nerve nuclei. Their axons go directly to the effector organ (muscle).

Front 41

Spinal Cord Lesions:
Hemi-section (right or left half is damaged by lesion)

Back 41

-Loss of pain and temperature sensation contralaterally
-Loss of pressure, touch sensation, and conscious proprioception ipsilaterally
-Ipsilateral paralysis

Front 42

Spinal Cord Lesions:
Posterior column lesions (1/2)

Back 42

-Loss of pressure, touch sensation, and conscious proprioception ipsilaterally

Front 43

Spinal Cord Lesions:
Anterior Spinal Cord (whole anterior half)

Back 43

-bilateral loss of pain and temperature sensation
-bilateral paralysis

Front 44

Spinal Cord Lesions:
Central Lesion at the Level of the Cervical Cord

Back 44

-Bilateral loss of pain and temperature sensation at the level of the lesion.

Front 45

What kind of lesion would cause unilateral loss of all sensory modalities in an entire extremity?

Back 45

Lesion above the spinal cord (in the brain or brainstem)

Front 46

What is a reflex?

Back 46

An automatic (involuntary) response to a stimulus through a reflex arc.

Front 47

What is an example of a somatic reflex? An autonomic reflex?

Back 47

Somatic: removing body from a painful stimulus
Autonomic: regulating BP, CO2 level.

Front 48

Are reflexes excitatory or inhibitory?

Back 48

They can be one or the other

Front 49

What are the five components of a reflex arc?

Back 49

Sensory receptor
Sensory neuron
Interneuron (*sometimes)
Motor neuron
Effector organ

Front 50

Stretch Reflex:
What are the main components?
Sensory? Interneuron? Motor?

Back 50

Sensory receptor is called a muscle spindle and it detects sudden stretch. There is NO interneuron, the sensory neuron synapses directly with the motor neuron. The motor neuron causes the muscle to contract.

Front 51

Golgi Tendon Reflex:
Purpose? Sensory receptor? Interneuron? Motor neuron?

Back 51

Purpose of this reflex is to prevent contracting muscles from putting too much tension on tendons. Sensory receptors are called golgi tendon organs and are found in tendons and when they are stretched they are activated. They synapse with an inhibitory internueron that inhibits the motor neuron which relaxes the muscle.

Front 52

Withdrawl reflex:
Purpose? Sensory receptors? Interneuron? Motor neuron?

Back 52

The purpose is to remove body part from painful stimulus. The sensory receptor is pain receptor that activates the sensory neuron which synapses with excitatory interneuron which synapses with motor neuron which stimulate flexor muscles to contract. (at the same time inhibitory neurons send action potentials to motor neurons to relax extensor muscles)

Front 53

Crossed extensor reflex:
Purpose? Sensory Receptor? Interneuron? Motor neuron?

Back 53

Purpose is allow support of the body during the withdrawl reflex. Same sensory receptor as withdrawl - pain receptor. Collateral axons extend through white commissure and synapse with motor neurons on the opposite side of the spinal cord. While the withdrawl reflex causes flexion of one lower limb, the crossed extensor reflex causes extension of the other lower limb.

Front 54

What can inhibit reflexes?

Back 54

Mental control

Front 55

What are the two groups of senses?

Back 55

Special senses and general senses

Front 56

What are the characteristics of special senses and what are some examples?

Back 56

-located in specific areas of the body
-have specialized nerve endings
-sight, hearing, taste, smell, and balance

Front 57

What are the characteristics of general senses? How can we divide this group further?

Back 57

There are receptors all over the body.
2 more groups:
1. Somatic senses: info about the body and environment (touch, pressure, itch, vibration, temp, proprioception, pain)
2. Visceral senses:
Information about internal organs (pain and pressure)

Front 58

Types of sensory receptors (5) and what they are for.

Back 58

Chemoreceptors (chem balance)
Photoreceptors (light)
Mechanoreceptors (pressure)(S)
Thermoreceptors (temp)(S)
Nociceptors (pain)(S)
(S): somatosensory

Front 59

What kind of neurons are somatosensory neurons? Where are the cell bodies?

Back 59

Unipolar, cell bodies in the dorsal root ganglion.

Front 60

How do sensory receptors respond to stimuli?

Back 60

By generating action potentials which will propogate along the nerve to the spinal cord and brain.

Front 61

Examples of ways that sensory information is not perceived.

Back 61

-some sent to cerebellum
-some receptors monitor homeostasis unconsciously
-cortex suppression (ignoring of action potentials-saccades)
-neuromodulators decreasing frequency of action potentials
-Adaptation

Front 62

Sensory Disorders:
Hyperalgesia

Back 62

Stimuli that is normally only mildly uncomfortable is extrememly painful.

Front 63

Sensory Disorders:
Allodynia

Back 63

Normally un-painful stimuli are preceived as painful (swallowing)

Front 64

Sensory Disorders:
Ataxia

Back 64

Uncoordination that is not due to muscle weakness.

Front 65

Sensory Disorders:
What do people with sensory ataxia do to compensate?

Back 65

They use vision to compensate for decreased somatosensory information.

Front 66

Sensory Disorders:
Sensory vs. Cerebellar ataxia

Back 66

Romberg test: stand with feet together first try to stand still with eyes open, then try with eyes closed. If it's cerebellar it's hard both ways, if it's sensory then it's will be easier with eyes open.