Ch. 8.2 Skin is a Complex Organ that Contains a Variety of Sensory Receptors

Question 1

What is the epidermis

Answer 1

The outermost and thinnest layer of skin

Question 2

What is the dermis?

Answer 2

The middle layer of skin that contains a rich web of nerve fibers in a network of connective tissue and blood vessels.

Question 3

What is the hypodermis?

Answer 3

The innermost layer of skin that provides an anchor for the muscles, contains Pacinian corpuscles and helps shape the body.

Question 4

What are the three layers of skin?

Answer 4

epidermis, dermis and hypodermis

Question 5

Is skin considered an organ?

Answer 5

Yes

Question 6

How is light touch detected?

Answer 6

By four highly sensitive tactile (touch) receptors.
A. Pacinian corpuscle (vibration)
B. Meissner corpuscle (light touch)
C. Merkel discs (fine touch)
D. Ruffini endings (stretch)

Question 7

What do you know about the Pacinian corpuscles?

Answer 7

1. embedded in the hypodermis
2. large, vague receptive borders
3. detects vibration
4. fast-responding and fast adapting receptors

Question 8

What do you know about the Meissner corpuscles?

Answer 8

1. Most of our ability to perceive the form of an object we touch comes from this receptor and the Merkel discs.
2. fast adapting
3. densely distributed in skin regions where we feel fine details by touch (fingertips, tongue, and lips)

Question 9

What do you know about the Merkel discs?

Answer 9

1. Slow adapting
2. Most of our ability to perceive the form of an object we touch comes from this receptor and the Meissner corpuscles.
3. densely distributed in skin regions where we feel fine details by touch (fingertips, tongue, and lips)

Question 10

What do you know about Ruffini endings?

Answer 10

1. detect stretching of the skin when we move fingers or limbs
2. Very few Ruffini endings but they have large receptive fields.
3. large, vague receptor fields.

Question 11

How does myelination and size of axons affect conduction of action potentials?

Answer 11

larger and more myelination increase the speed of conduct.

Question 12

What is the dorsal column system?

Answer 12

A somatosensory system that delivers most touch stimuli via the dorsal columns of spinal white matter to the brain.

Question 13

What is the dorsal column nuclei?

Answer 13

Collections of neurons in the medulla that receive somatosensory information via the dorsal columns of the spinal cord. These neurons send their axons across the midline and to the thalamus.

Question 14

Why do touch receptors respond to touch?

Answer 14

They make a stretch-sensitive ion channel, using a protein called Piezo that depolarizes the cell when the membrane is stretched.

Question 15

What is a dermatome?

Answer 15

The skin can be divided into bands corresponding to the spinal nerves that carry the axons from the different regions. A dermatome is the region of skin innervated by a particular spinal nerve.

Question 16

Is there plasticity in receptive fields?

Answer 16

yes