skin p3 Flashcards
what are the names of the different skin receptors
- free nerve endings
- tactile/merkel discs
- tactile/meissner corpuscles
- lamellar/pacinian corpuscles
- bulbous corpuscles
describe what free nerve endings look like
- mostly unmyelinated small diameter fibres
- some myelinated small diameter fibres
- usually have small swelling at the distal ends –> sensory terminals
what do free nerve endings respond mainly to
- temperature
- painful stimuli –> very painful = myelinated, ache = unmyelinated
- some movement and pressure
- itches
- wrap around hair follicles –> detect if mosquito lands on you
describe what a tactile/merkel discs look like
- are free nerve endings located in deepest layers of epidermis
- have a large disc shaped epidermal cell
what does a tactile/merkel cell do/sensitive to
- 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
where are the tactile/meissner corpuscles located and what do they look like
- 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»_space; action potential
what does the tactile/meissner corpuscles sense
- delicate or discriminative touch
- light pressure
- low frequency vibrations (2 to 80 hertz)
what are the 2 types of skin cancer we spoke about
- basal cell carcinoma
- malignant melanoma
describe basal cell carcinoma
- is common but usually benign
- affects keratinocytes
- metastasis is rare
what are the primary mechanisms for heat transmittion
- radiation
- evaporation
- convection
- conduction
describe radiation
- transfer of heat via infrared waves.
- increased vasodilation
describe evaporation
- the process of losing heat through the conversion of water to gas
- through sweat
describe convection
- 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
describe conduction
- is the process of losing heat through physical contact with another object or body
- touching metal or something cold
what does the body do to prevent heat loss
- blood flow to the skin is reduced by constriction of the smooth muscle bands around arterioles (small arteries) –> PRECAPILLARY SPHINCTERS
what does the body do to promote heat loss
- the relaxation of the precapillary sphincters increases blood flow to the skin, promoting heat loss
what area on the brain contains both the heat LOSS and the heat GAIN center
- preoptic area of the hypothalamus
describe the arrector pili muscle
- 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
