SKIN PHYSIOLOGY Flashcards
1/ Outline the funtion of selected sensory receptors in skin 2/ Understand how skin bloodflow can be controlled 3/ Describe the structure and function of eccrine sweat glands and their role in thermoregulation 4/ Understand basic mechanisms of heat transfer 5/ Understand 'core body temperature' and how it is monitored 6/ Explain mechanisms for heat loss and heat conservation/generation 7/ Aware of physiological consequences of sever burns
what are the 5 types of skin receptor?
- free nerve endings
- tactile discs
- tactile corpuscles
- lamellar corpuscles
- bulbous corpuscles
what is the most common receptor in skin?
free nerve endings
the fibre characteristics of free nerve endings?
unmyelinated small diameter but also some myelinated
small swellings at distal ends also referred as
sensory terminals at free nerve endings
TRPV1 receptors is
cation channels at free nerve endings
H1 receptors is chemical stimuli for
free nerve endings
pathway of stimuli at free nerve endings?
activation –> APs in afferent sensory axons –> CNS –> somatosensory cortex
what does free nerve endings mainly respond to?
- temperature/thermal
- painful stimuli (nociceptive)
- movement and pressure
itchy respond to histamine is trait of which type of skin receptor?
free nerve endings
where is free nerve endings located?
deepest layer of epidermis
what is the associated structure with free nerve endings?
tactile (merkel) discs
what is the purpose of serotonin 5HT over skin physiology?
communication between tactile epithelial and ner ending
where can you find most tactile discs?
fingertips
which type of skin receptor is good for 2 point discrimination?
tactile disc because small receptive fields
what does tactile disc mainly detect?
- fine touch and light pressure
- texture, shape and edge
where is the tactile corpuscle located?
papillary layer of dermis
(especially hairless skin)
which type of skin receptor could be found around the finger pads, lips, eyelids, external genitalia, soles of feer, nipples?
tactile corpuscle
structure of the tactile corpuscle?
- encapsulated
- spiralling/branching unmyelinated sensory terminals surrounded by modified Schwann cells and thin oval FCT capsule
how does stimuli triggers the tactile corpuscle?
deformation of capsule –> triggers entry of Na+ ions –> nerve terminal –> action potential
what can tactile corpuscle detect?
- delicate ‘fine’ / discriminative touch
- light pressure
- low frequency vibration
if you are reading Braille text, which skin receptor you would most likely be using?
tactile corpuscles and likely tactile discs
which type of skin receptor is scattered deep in dermis and hypodermis
lamellar (pacinian) corpuscles
lamellar corpuscles’ characteristics?
- single dendrite within concentric layers of collagen fibres
- specialised fibroblasts
what are the layers of collagen fibres in lamellar corpuscles being seperated by
gelatinous interstitial fluid
how does lamellar corpuscles transmit signals
deformation of capsule –> opens pressure sensitive Na+ channels in sensory axon –> inner layers covering axon terminal ‘relax’ quickly –> APs discontinued (rapidly adapting)
what type of contact does lamellar corpuscle detect?
- deep pressure
- vibration
where is bulbous corpuscles located?
- dermis and subcutaneous tissue
- joints capsules
why can you find bulbous corpuscles at joint capsules?
- help signal degree of joint rotation - proprioception
- e.g. monitoring slippage of object accross surface skin –> modulate grip in fingers
describe the structure of bulbous corpuscle?
- network of nerve endings
- core collagen fibres
- continuous with surrounding dermis
- capsule through entire structure
function of bulbous corpuscle?
- sustained deep pressure
- stretching/distortion of skin
_____(1)______ muscle in walls of _____(2)______ and _______(3)______ innervated by the ______(4)_______ nervous system
(1): smooth
(2): arteries
(3): pre-capillary
(4): sympathetic
which acts on alpha1 adrenergic receptors?
noradrenaline
pathway of reducing skin bloodflow?
GPCRs coupled to intracellular 2nd messengers –> increased intracellular Ca2+ –> constriction –> reduce skin bloodflow
____(1)_____ SNS activation of _____(2)_____ causes relaxation of arteries to skin to increase skin bloodflow
(1): reducing
(2): alpha1 receptor
reducing activation of alpha1 receptors on vascular smooth muscle cause _____(1)______, therefore increase skin bloodflow
activation of alpha1 receptors cause ____(2)_____, therefore reduce skin bloodflow
(1): vasodilation
(2): vasoconstriction
what are the 4 primary mechanisms of heat transfer?
- radiation
- evaporation
- convection
- conduction
eccrine sweat glands are innervated by?
SNS - adrenaline beta receptors
what is sympathetic cholinergic?
release of ACh onto mACHRs
which area of hypothalamus contains heat and cold sensitive for central thermoreceptors?
preoptic
what happens to the body if body temperature increases above set point?
- reduce SNS activation of alpha1 on skin blood vessel for vasodilation
- increase SNS cholinergic activation of mAChRs on swaet glands –> sweating
- increase respiratory rate
- behavioural changes
what happens to the body if body temperature decreases below set point
- Heat Gain centre activated
- increased generation of body heat through nonshivering or shivering thermogenesis
- conservation of body heat by decrease blood flow –> reduce heat loss by radiation and convection
- countercurrent exchange
how does shivering generate heat?
- oscillatory contractions of agonist and antagonist muscle
- ATP –> ADP + Pi + movement + heat
increase in ________(1)_______ nerve activity and increase in circulating: ______(2)/(3)_______ from adrenal medulla is one of the activities during non-shivering thermogenesis
(1): sympathetic
(2): adrenaline
(3): noradrenaline
increased glycogenolysis in liver and muscle is an example for ____________________ in heat generating mechanism
increase cellular metabolism of non-shivering thermogenesis
how does body produce heat instead of ATP in non-shivering thermogenesis?
‘uncoupling’ of oxidative phosphorylation
what does an increase of thyroxine respond to?
TRH and TSH
what does increase of thyroxine do to the body>
increase basal metabolic rate
which muscle attach hair follicle to upper dermis?
arrector pili (smooth muscle)
which innervate arrector pili muscle?
SNS - alpha1 receptor
how do we have goosebumps?
contraction of arrector pili muscle as a physiological feed forward to pull hair upright, compress sebaceous gland which lubricate skin and dimples skin
which potential complication of severe burn help remind us of normal skin function?
dehydration, hypovolemic shock, infection/sepsis, hypothermia
which system dysfuction can also be caused by severe burn?
- electrolyte imbalance
- hypermetabolism
- GI ulceration
- renal failure
- respiratory dysfunction
what is an example of electrolyte imbalance?
hyperkalaemia - increase of K+
