Neuro Exam 2 Lecture 2

Front 1

What is somatosensory?

Back 1

All sensations arising from the skin, connective tissue, skeletal muscle, periosteum, and teeth

Front 2

What are the sensory systems?

Back 2

-somatosensory
-viscerosensory
-special sensory

Front 3

viscerosensory information is:

Back 3

sensation arising from cranial, thoracic, and abdominal pelvic viscera

Front 4

What are special senses? (meaning it is processed a little bit differently)

Back 4

sensations relating to vision, hearing, balance, equilibrium, olfaction, and taste

Front 5

It takes ____ neurons to get from the initial receptor up to the brain

Back 5

3 neurons- a 3 neuron pathway

Front 6

What are the types (or modalities) of somatosensation?

Back 6

-Discriminative senses:
-discriminative touch,

-vibratory sense,

-conscious proprioception-makes it up to the cerebral cortex (unconscious is in the cerebellum)

(pain, temperature, and crude touch are also somatosensory modalities, but are not discriminative- part of pain pathways)

Front 7

The __________ allows you to adjust and fine tune your movements

Back 7

cerebellum

Front 8

tactile sensation is really talking about:

Back 8

discriminative touch

Front 9

What is discriminative touch?

Back 9

a very fine, well localized sense of touch- you can pinpoint the type of tactile stimulus that is occurring and localize it to your body or face (depending on where stimulus originates).

for example, when you put your clothes on, you are aware of that or when someone taps you on the shoulder, you are aware of that and you know it is coming from the shoulder.

Front 10

What is vibratory sense? How can it be tested?

Back 10

We have specialized receptors that allow us to interpret vibratory types of sensation
-For example, when you are driving in a car you are aware of the vibrations

Can test these by using a tuning fork against a bony prominence, and it resonates.

Front 11

What is conscious proprioception? how is that different from unconscious proprioception?

Back 11

proprioception is by definition awareness of your body in space, so the position and orientation that you are aware of is conscious proprioception. For example, right now I know I am sitting and I am aware of the position of my limbs- allows you to move through your environment appropriately - this proprioceptive stimuli makes it up to the cerebral cortex

Front 12

how is that different from unconscious proprioception?

Back 12

unconscious proprioception initially travels by the same pathways as conscious proprioception, but the cerebellum is involved as it allows you to adjust and fine tune your movements while they are in progress and this is below the level of consciousness (conscious proprioception makes it up to the cerebral cortex, which makes us consciously aware of our position in space)

Front 13

There are two pathways that process the types of discriminative senses. What are they?

Back 13

- Posterior column-medial lemniscus system (PCMLS): body

-Cranial touch system: face

Front 14

If tactile sensation, or discriminative touch, is coming from anywhere in the body, where will it will be processed?

Back 14

in the Posterior column-medial lemniscus system (PCMLS)

Front 15

If tactile sensation, or discriminative touch, is coming from anywhere on the face, where will it will be processed?

Back 15

by the cranial touch system (by a homologous pathway)

Front 16

What is crude touch?

Back 16

The non localizable- like pinching (pain pathway)

Front 17

What pathways are pain, temperature, and crude touch processed by?

Back 17

-Spinothalamic tract (STT): Body

-Cranial pain and temperature system: face

Front 18

The spinothalamic tract (STT) processes pain, temperature, and crude touch if the somatosensation is coming from where?

Back 18

The body

Front 19

The cranial pain and temperature system processes pain, temperature, and crude touch if the somatosensation is coming from where?

Back 19

The face

Front 20

Remember that the somatosensory pathways are _____ neuron pathways.

Back 20

3

1st order, 2nd order, and 3rd order

Front 21

In the somatosensory system, regardless of which pathway is being activated, it is going to begin with the initiation of some stimulus activating a sensory receptor. Most often, what is the sensory receptor?

Back 21

The specialized ending of the pseudounipolar sensory neuron (a specialization at the distal end that is out in your skin, muscle, or connective tissue) of the first order neuron

Front 22

In the somatosensory syestem, every 1st neuron is a _____________ neuron

Back 22

pseudounipolar

Front 23

generally in the somatosensory system, every first order neuron synapses where?

Back 23

In the brainstem (if it is conveying information from the face) or spinal cord

Front 24

generally in the somatosensory system, every second order neuron synapses where?

Back 24

in the thalamus

Front 25

generally in the somatosensory system, every third order neuron synapses where?

Back 25

in the primary somatosensory cortex

Front 26

What type of neuron is a
-first order neuron?
-second order neuron?
-third order neuron?

Back 26

1st- pseudounipolar
2nd- multipolar
3rd- multipolar

Front 27

_______ % of neurons in the nervous system are multipolar

Back 27

99 %

Front 28

The cell body of a second order neuron will be:

Back 28

Wherever the synapse occurs, so either in the spinal cord or the brainstem (in a nucleus somewhere)

Front 29

The axon of the _____ order neuron decussates, which means:

Back 29

2nd order neuron

It means it crosses the midline

Front 30

We process information in the same side of our brain, true or false?

Back 30

False- we process information in the opposite side of our brain, so sensation from the left side is processed in the right side of the brain- pathways in the right side of the brain have to be activated to move the left side of the body (and the other way around)

Front 31

The axons cross at different levels of the neuroaxis, but it is always the axon of the ______ order neuron that does the crossing

Back 31

second

Front 32

The synapse of the second order neuron onto the third order neuron occurs where?

Back 32

In the thalamus

Front 33

The gyrus in the cortex that processes somatosensory information is the:

Back 33

Post central gyrus, so every somatosensory pathway we talk about is going to ultimately bring that information up to the post central gyrus

Front 34

What are the generalities of a first order neuron?

Back 34

-peripheral receptor
-pseudounipolar
-enters spinal cord
-synapses in brainstem or spinal cord

Front 35

What are the generalities of a second order neuron?

Back 35

-multipolar
-cell body in spinal cord or brainstem
-axon decussates
-synapses in thalamus

Front 36

What are the generalities of a third order neuron?

Back 36

-multipolar
-cell body in thalamus
-synapses in primary somatosensory cortex

Front 37

sensory neurons of the periphery are also called:

Back 37

primary afferent nerve fibers

Front 38

the primary afferent nerve fibers, or the peripheral sensory neurons, all have the ____1______ morphology, has a cell body in a _____2______, and has how many processes that leave the cell body?

Back 38

1. pseudounipolar
2. ganglia
3. Has a single process that leaves the cell body, but then that process bifurcates

Front 39

Functionally, the peripheral process of a psuedounipolar neuron functions as a _________, which does what?

Back 39

dendrite (brings information from its receptive ending toward the cell body)

Front 40

sensory Information comes in via:

Back 40

the branches of the peripheral process (ie dendrite), and each one of the branches would have a receptive specialization on it.

Front 41

What would each of the branches of the peripheral process (dendrite) have a receptive specialization on it?

Back 41

Helps it to react to different stimuli in the environment

Front 42

Functionally on a pseudounipolar neuron, the central process functions as a(n) _____1_____, which does the _____2______ of information.

Back 42

1. axon

2. output

Front 43

the central process (axon) of a pseudounipolar neuron can branch extensively, which means:

Back 43

it can activate multiple second order neurons

Front 44

The peripheral process of a pseudounipolar neuron is associated with:

Back 44

a sensory receptor

Front 45

The cell body of a pseudounipolar neuron is found where?

Back 45

in a posterior root ganglion or a cranial nerve ganglion

Front 46

the central process of a psuedounipolar neuron enters where?

Back 46

a posterior horn

Front 47

All of the information that goes to the skin will be processed backwards in the:

Back 47

same neuron

Front 48

The cell body of a sensory neuron is found in:

Back 48

A posterior root ganglion or a cranial nerve ganglion

Front 49

There are some sensory receptors that are quite deep and ones that are really close to the surface. Which give the best discriminative ability?

Back 49

The ones greater to the surface. The deeper ones need a greater magnitude of stimulus to be activated

Front 50

We can categorizes the sensory receptors broadly into three classes. What are the types of cutaneous sensory receptors?

Back 50

-mechanoreceptors
-nociceptors
-thermoreceptors

Front 51

Which receptors are responsible for touch such as fine, well localized touch, vibratory sense, and proprioception

Back 51

mechanoreceptors (underlie the sensation of touch)

Front 52

There are multiple types of___________, each which is responsible for a different type of touch

Back 52

mechanoreceptors

Front 53

If we are talking about the pain pathways, then we are talking about which receptors?

Back 53

nociceptors

noci= pain

Front 54

What activates the nociceptors?

Back 54

Tissue damage or a damaging sort of stimulus

Front 55

__________ are responsive to changes in temperature. There are both hot and cold ___________.

Back 55

Thermoreceptors

Front 56

All ____________ and _________ are free nerve endings

Back 56

nociceptors and thermoreceptors

Front 57

Although some mechanoreceptors (touch receptors) have free nerve endings, the majority of them have:

Back 57

a connective tissue capsule or something surrounding them

Front 58

What are the two components that increase speed of a nerve fiber?

Back 58

Increased myelination and larger diameter

Front 59

______ and _______ are motor fibers and are the most rapidly conducting fibers

Back 59

1a(fasted)
1b (second fastest)

Front 60

A Beta fibers (A β fibers) are also known as __________

Back 60

type II fibers

Front 61

A β fibers, or type II fibers are large diameter, heavily myelineated fibers. What does this mean?

Back 61

That they are very rapidly conducting (about 90 or more m/s)

Front 62

Which fibers do we use for our fine discriminative touch pathways?

Back 62

A β fibers

Front 63

Which pathways have Aβ fibers?

Back 63

-PCMLS pathway
-Cranial touch pathway

(fine discriminative touch pathways)

Front 64

There are two types of pain and temperature sensation processing fibers. What are they?

Back 64

A Delta ( A 𝛿)

C fibers

Front 65

A Delta ( A 𝛿) and C fibers have ________ nerve endings

Back 65

Free nerve endings

-nociceptors and thermoreceptors

Front 66

What are the pathways that use A Delta ( A 𝛿) and

C fibers

Back 66

STT (spinothalamic tract)

-cranial pain and temp

Front 67

______ fibers are unmyelinated. They are very small, unmyelinated fibers, so they have the slowest conducting in the nervous system

Back 67

C fibers

Front 68

What fibers give the sensation of dull pain (slow, achey, burny pain)

Back 68

C fibers

Front 69

___________ are slightly larger fibers and are thinly myelinated, and are the "fast pain" receptors

Back 69

A Delta ( A 𝛿) fibers

Front 70

C fibers have a maximum speed of ______ m/sec, while A Delta ( A 𝛿) fibers have a maximum speed of ______ m/sec

Back 70

C fibers- 2 m/s
A Delta ( A 𝛿) fibers - 45 m/s

Front 71

A cutaneous area is innervated by a ______ nerve fiber, which allows for what?

Back 71

single nerve fiber

allows for localization of stimuli

Front 72

What is the receptive field?

Back 72

The area of the skin contacted by each of those individual nerve fibers- related to one neuron

Front 73

Receptive field size is inversely related to discriminative ability. The back has _________ receptor fields. What does this mean?

Back 73

large

-low discriminative ability

Front 74

The fingertips have _______ receptive fields, which means:

Back 74

small

high discriminative ability

Front 75

The portion of skin that is innervated (contacted by the receptive endings of each individual nerve fiber) by a single neuron (like one of the neurons of the musculocutaneous nerve) is the _____________ ______ for that neuron

Back 75

receptive field

Each receptive field is related to 1 neuron

Front 76

The __________ the receptive fields, the closer together the points (stimuli) could be and still be distinguished as coming from different points

Back 76

smaller

Front 77

within the musculocutaneous nerve, you have several neurons that are all sensory neurons, that collectively go to one area, but within that area of distribution of that cutaneous nerve, the portion of skin that is innervated by a single neuron is the _________ ______ for that neuron

Back 77

receptive field

Front 78

A _____________ relates to all of the skin that is innervated by all of the sensory neurons that are traveling in one spinal nerve, so that is related to a spinal cord segment.

(area of a skin innervated by all somatosensory fibers of a single spinal nerve)

Back 78

dermatome

Front 79

All of the fibers of the musculocutaneous nerve which continues into the lateral cutaneous nerve arise from which spinal level?

Back 79

C6

Front 80

What are three classically tested dermatomes and how do they test them?

Back 80

T4- nipple
T10- umbilicus
L5- great toe

Front 81

What is the difference between a dermatome and a receptive field?

Back 81

a dermatome is an area of skin innervated by all somatosensory fibers of a single spinal nerve, while a receptor field is a cutaneous area (like a part of skin) innervated by a single nerve fiber

Front 82

Our _________ senses allow us to localize

Back 82

discriminative

Front 83

The more highly localized a receptive field, means ___________ discriminative ability

Back 83

high

Front 84

If you have one nerve fiber that branches very extensively and has lots of receptive endings in a very small area, what does this mean?

Back 84

it is high density; high discriminative ability- you can touch two points very close together, and still recognize that they come from two distinct touches (look at slide 8)

Front 85

A receptor is one type of a __________ __________ potential

Back 85

local graded

Front 86

What occurs with varicella zoster?

Back 86

The latent virus resides in sensory ganglia - these virus particles live in the somas of sensory neurons and become reacted upon very specific dermatomes (very painful blistering)

Front 87

What does PCMLS stand for?

Back 87

posterior column medial lemniscus

Front 88

What type of sensation travels along the PCMLS somatosensory pathway?

Back 88

-discriminative touch, conscious proprioception from the body

Front 89

What receptors does the PCMLS use?

Back 89

mechanoreceptors

Front 90

What is the classification of the primary afferent nerve fiber in the PCMLS?

Back 90

A β fibers (A Beta), large diameter, heavily myelinated

Front 91

The PCMLS pathway conveys sensory information from the body, so the cell bodies of the first order neuron in this pathway are all going to be where?

Back 91

In the posterior root ganglion (which posterior root ganglion depends on which dermatome was touched and where that stimulus is- remember there are 31 pairs of spinal nerves)

Front 92

In the PCMLS, the peripheral process is going to be in a:

Back 92

peripheral nerve, such as the lateral cutaneous nerve

Front 93

In the PCMLS, where does the central process enter the spinal cord?

Back 93

the medial division of the posterior root entry zone

Front 94

Once the central process enters the spinal cord in the medial division of the posterior root entry zone, what does it do?

Back 94

It ascends in the ipsilateral fasciculus gracilis, or fasciculus cuneatus, depend on where the touch sensation originated from

Front 95

If the axon of the first order neuron ascends in the ipsilateral fasciculus gracilis, what does this mean?

Back 95

that the touch sensation is from the lower limb

Front 96

If the touch sensation is from the upper limb, where does the axon ascend after entering the medial division of the posterior root entry zone?

Back 96

It ascends in the ipsilateral fasciculus cuneatus

Front 97

Where does the first order neuron of the PCMLS synapse?

Back 97

In the caudal medulla

Front 98

In the PCMLS, the first order neuron ascends in the ipsilateral fasciculus cuneatus if it is above this spinal level____?____ and in the fasciculus gracilis if it is below the same spinal level.

Back 98

T6

Above T6=fasciculus cuneatus
Below T6 =fasciculus gracilis

Front 99

In the PCMLS, where is the cell body of the second order neuron?

Back 99

In the nucleus gracilis (lower limb) or the nucleus cuneatus (upper limb)

Front 100

Which neuron decussates in the PCMLS? Where does this occur?

Back 100

The second order neuron.

The axon decussates as an internal arcuate fiber and forms the contralateral medial lemniscus

Front 101

In the PCMLS, where does the second order neuron synapse? Be specific.

Back 101

In the thalamus. Specifically in the VPL nucleus in the thalamus (ventral posterolateral nucleus)

Front 102

In the PCMLS, where do you find the cell bodies of the 3rd order neuron?

Back 102

in the VPL (Ventral posterolateral nucleus)

Front 103

In the PCMLS, where does the axon of the third order neuron ascend from the VPL?

Back 103

the axon ascends in the posterior limb of the internal capsule

Front 104

In the PCMLS, where does the third order neuron synapse?

Back 104

in the primary somatosensory cortex (AKA post central gyrus, AKA Brodeman's area 3,1,2