Dermatomes, Peripheral Nerves, and Receptors

Question 1

what is a dermatome?

what is its clinical relevance?

Answer 1

The area of skin supplied by one segment of the spinal cord.

location of a lesion can be determined by which dermatome(s) is/are affected.

Question 2

what is the dermatome for the first cervical and the coccygeal?

Answer 2

haha! they dont have any because their nerves have no dorsal roots

Question 3

what will a spinal nerve innervate?

Answer 3

1 somite

Question 4

what is a somite?

Answer 4

a dermatome, a myotome (muscles) and a sclerotome (bones and ligaments).

Question 5

what are the dermatomes for the following areas:

1. Biceps brachii tendon reflex
2. Triceps tendon reflex
3. Brachioradialis tendon reflex
4. Upper Abdominal superficial reflexes
5. Middle Abdominal superficial reflexes
6. Lower Abdominal superficial reflexes
7. Patellar tendon reflex
8. Achilles tendon reflex

Answer 5

1. C5-C6
2. C6, C7
3. C5, C6
4. T6, T7
5. T8, T9
6. T10, T12
7. L2, L3, L4
8. S1, S2

Question 6

what is shingles?

Answer 6

is the herpes zoster virus that resides dormant in sensory nerves; when reactivated causes pain and rash in the affected dermatomes

Question 7

what nerve does shingles affect?

Answer 7

V1 of CN V

Question 8

Most peripheral receptors utilize what type of nerve fiber?

What nerve fiber do free nerve endings utilize?

Answer 8

Type A-beta

C type fibers

Question 9

What are the 5 types of sensory receptors?

Answer 9

1. Mechanoreceptors
2. Thermoreceptors
3. Nociceptors
4. Electromagnetic receptors
5. Chemoreceptors

Question 10

Sensory receptors can be subdivided into what 2 type of receptors?

Answer 10

1. Encapsulated
2. Non-Encapsulated

Question 11

Some receptors are fast adapting and slow adapting, what does this mean?

Answer 11

Rapidly adapting: is used for information about changes in stimulation

Slow adapting: is used for information about ongoing stimulation

Question 12

• What information do free nerve endings relay?
• Is it fast or slow?
• What can activat these fibers?

Answer 12

• Predominantly pain information, but some touch, pressure, and tickle.
• both fast and slow pain sensation
• Temperature

Question 13

What information do Merkel’s discs relay?

where can we find merkel’s discs?

how are merkel’s discs nerve fibers?

Answer 13

• Two-point discrimination.
• Superficial skin layers of fingertips.
• Slowly adapting, for pressure.

Question 14

what are hair-like follicles?

Answer 14

Free nerve endings wrapped around a hair follicle that act as mechanoreceptors (movement activates the free nerve)

Question 15

what information do Meissner’s corpuscles relay?

are they fast or slow adapting?

Answer 15

• fine touch or two point discrimination and some vibration
• rapidly adapting (fast)

Question 16

what information do Pacinian corpuscle’s relay?

are they fast or slow adapting?

what is another name for Pacinian corpuscle’s?

Answer 16

vibration mainly and deep pressure

fast adapting

Lamellar bodies

Question 17

What information do Ruffini’s corpuscle relay?

where do we find Ruffini’s corpuscle?

Answer 17

propioceptive information of muscles and temperature (heat mainly), also stretching in skin (cutaneous)

in subcutaneous tissue and joints

Question 18

what are Krause’s end bulbs for?

Answer 18

cold sensation

Question 19

neuromuscular spindles are divided into 2 categories of motor neurons, what are they? where do we find each?

Answer 19

1. alpha motor neurons = extrafusal muscle fibers
2. gamma motor neurons = intrafusal muscle fibers

Question 20

There are 2 types of intrafusal muscle fibers?

Answer 20

1. nuclear bag
2. nuclear chain

Question 21

what changes occur in order to

receive proprioceptive information about changes in muscle length?

Answer 21

Activation of gamma motor neurons changes the

shape of these intrafusal fibers (nuclear bag and nuclear chain), activates sensory endings wrapped around the intrafusal fibers and then we get propioception of muscle length

Question 22

what are golgi tendon organs?

how do they work?

What is their purpose?

Answer 22

A ‘capsule’ of loosely arranged tendon fibers.

When the capsule is stretched, free nerve endings inside are activated, and transmit information to the spinal cord, where it synapses on alpha motor neurons.

They provide an inhibitory effect to prevent too much tension on the muscles.

Question 23

what is a myotactic reflex?

what is a inverse myotactic reflex?

Answer 23

a stretch reflex generated by tapping on a deep tendon

occurs at the same time as a myotactic reflex, and acts in relaxation of the antagonistic muscles.