skin p3

Question 1

what are the names of the different skin receptors

Answer 1

• free nerve endings
• tactile/merkel discs
• tactile/meissner corpuscles
• lamellar/pacinian corpuscles
• bulbous corpuscles

Question 2

describe what free nerve endings look like

Answer 2

• mostly unmyelinated small diameter fibres
• some myelinated small diameter fibres
• usually have small swelling at the distal ends –> sensory terminals

Question 3

what do free nerve endings respond mainly to

Answer 3

• temperature
• painful stimuli –> very painful = myelinated, ache = unmyelinated
• some movement and pressure
• itches
• wrap around hair follicles –> detect if mosquito lands on you

Question 4

describe what a tactile/merkel discs look like

Answer 4

• are free nerve endings located in deepest layers of epidermis
• have a large disc shaped epidermal cell

Question 5

what does a tactile/merkel cell do/sensitive to

Answer 5

• the merkel detects the stimuli, it relays it to the nerve endings which generates an action potential
• communicates between the tactile epithelial cell and nerve endings, via serotonin (5HT)
• abundant in fingertips + small receptive fields –> good for 2 point discrimination
• sensitive to:
  - texture,shape and edges
  - fine touch and light pressures

Question 6

where are the tactile/meissner corpuscles located and what do they look like

Answer 6

• located in the papillary layer of dermis –> especially in hairless skin
• they are encapsulated
• spiralling/branching unmyelinated sensory terminals that are surrounded by modified schwann cells, then by a thin oval fibrous connective tissue capsule
• deformation of capsule = entry of na+ ions into nerve terminal&raquo_space; action potential

Question 7

what does the tactile/meissner corpuscles sense

Answer 7

• delicate or discriminative touch
• light pressure
• low frequency vibrations (2 to 80 hertz)

Question 8

what are the 2 types of skin cancer we spoke about

Answer 8

• basal cell carcinoma

- malignant melanoma

Question 9

describe basal cell carcinoma

Answer 9

• is common but usually benign
• affects keratinocytes
• metastasis is rare

Question 10

what are the primary mechanisms for heat transmittion

Answer 10

• radiation
• evaporation
• convection
• conduction

Question 11

describe radiation

Answer 11

• transfer of heat via infrared waves.

- increased vasodilation

Question 12

describe evaporation

Answer 12

• the process of losing heat through the conversion of water to gas
• through sweat

Question 13

describe convection

Answer 13

• the process of losing heat through the movement of air or water molecules across the skin.
• airflow over body takes heat away, reduced by goose bumps

Question 14

describe conduction

Answer 14

• is the process of losing heat through physical contact with another object or body
• touching metal or something cold

Question 15

what does the body do to prevent heat loss

Answer 15

• blood flow to the skin is reduced by constriction of the smooth muscle bands around arterioles (small arteries) –> PRECAPILLARY SPHINCTERS

Question 16

what does the body do to promote heat loss

Answer 16

• the relaxation of the precapillary sphincters increases blood flow to the skin, promoting heat loss

Question 17

what area on the brain contains both the heat LOSS and the heat GAIN center

Answer 17

• preoptic area of the hypothalamus

Question 18

describe the arrector pili muscle

Answer 18

• they are smooth muscles that are innervated by the SNS
• they attach to the hair follicle to the upper dermis
• when contacting, pulls hair upwards making goosebumps
• compresses the sebaceous glands