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HUBS 192 > Dermis 3 > Flashcards

Dermis 3 Flashcards

1
Q

What are the types of receptors

A 
Free nerve endings
Tactile (merkel) discs 
Tactile (meissner) corpuscles 
Lamellar (pacinian) corpuscles
Bulbus (ruffini) corpuscles
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2
Q

Describe free nerve endings

A

Can be un/myelinated.

Small swellings at distal end (receptors) that have receptors that function as cation channels.

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3
Q

What do free nerve endings mainly respond to

A

Temperature
Painful stimuli (myelinated initial sharp pain unmyelinated slower aching pain)
Itch (chemical - histamine)
Light touch receptors (peritrichial - around hair follicles)

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4
Q

Describe Tactile (Merkel) discs

A

Free nerve endings in deepest layer of epidermis.
Associated with large disc shaped (Merkel) cells
Very small receptive fields - abundant in fingertips

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5
Q

What do Tactile (Merkel) discs mainly respond to

A

Sensitive physical features; Texture, shape and edges

Fine touch and light pressure

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6
Q

Describe Tactile (Meissner) corpuscles

A

Papillary layers of dermis (hairless skin)
Modified Schwann cells (not myelin forming) surrounded by a thin fibrous connective tissue capsule - deformation triggers Na+ channels

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7
Q

What do Tactile (Meissner) corpuscles mainly respond to

A

Delicate ‘fine’ or discriminative touch - shape/textural changes
Light pressures
Low frequency vibrations (2-80 Hz)

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8
Q

Describe Lamellar (Pacinian) corpuscles

A

Deep in dermis and hypodermis
Single dendrite surrounded by concentric layers of collagen fibres and fibroblasts
Layers separated by gelatinous interstitial fluid
Deformation opens Na+ channels - rapidly adapting

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9
Q

What do Lamellar (Pacinian) corpuscles mainly respond to

A 
Deep pressure (when first applied)
Vibration - as rapidly adapting (250Hz optimal)
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10
Q

Describe Bulbous (Ruffini) corpuscles

A

Dermis and subcutaneous tissue

Network of nerve endings intertwined with core of collagen fibres (continuous with dermis) - capsule surrounds structure

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11
Q

What do Bulbous (Ruffini) corpuscles mainly respond to

A

Deep pressure and stretching or distortion points of the skin
Signals continuous states of deformation - heavy prolonged touch and pressure
Degree of joint rotation (Proprioception)
Finger nails - slippage/grip

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12
Q

How is blood flow controlled

A

Precapillary sphincter muscles around artery controlled by sympathetic nervous system

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13
Q

How does the sympathetic nervous system effect blood flow

A

Noradrenaline - GPCRs coupled to receptors (2nd messenger system) opens Ca+ channels and constricts blood vessels lowering blood flow to dermis layer of skin

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14
Q

What does changing blood flow do

A

Helps control thermoregulation and blood pressure

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15
Q

What are the forms of thermoregulation

A

Radiation
Conduction
Convection
Evaporation

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16
Q

Describe radiation

A

Anything not at absolute 0 looses heat. When an object is colder than it’s surroundings it can gain heat from them

17
Q

Describe conduction

A

When in contact with object or air/water. Gradient for heat exchange - Heat moves from higher to lower. When there is no gradient there is no loss of heat

18
Q

Describe Convection

A

Transfer of heat to air/water. When we heat a layer around our skin and it moves we will then loose more heat heating up the next layer and it continues

19
Q

Describe evaporation

A

Heat loss - Best when external temperature is high. Loose the heat required to evaporate the water from our skin. In hot climates this is our only way of loosing heat.

20
Q

How do sweat glands work during thermoregulation

A

Sympathetic nervous system - ACh neurotransmitter

Some Beta receptors can also be activated by adrenaline (Why we sweat when nervous and excited)

21
Q

How do we detect a change in core body temp

A

Central thermoreceptors - In Preoptic area of Hypothalamus

22
Q

What happens when body temp goes above ‘set point’

A

Vasodilation - Reduce sympathetic nerve stimulation
Sweating - Increase SNS activity on sweat glands
Behavioural changes - Increased respiratory rate (Increases air flow and evaporation)

23
Q

How can we use our blood vessels to increase body temp

A

Counter current exchange - Warm blood from arteries transfers heat to cold blood from vein
Increases SNS to constrict blood flow to dermis

24
Q

How does shivering help increase body temp

A

Shivering - Increase tone of skeletal muscle , creating oscillatory contractions of agonist/antagonist (Mediated by stretch receptors

25
Q

What are the other non-shivering ways of increasing body temp

A

Increase SN activity and increase circulating adrenaline/noradrenaline
Increased cellular metabolism
‘Uncoupling’ of oxidative phosphorylation - produce heat instead of ATP (Adipose tissue - lypolysis)

26
Q

How does thyroxin help increase the bodies temp

A

Increase BMR which increases heat

May take several weeks exposure to cold before thyroxin secretion levels increase

27
Q

Describe the arrector pili muscles

A

Smooth muscle
Controlled by SNS (alpha 1 receptors)
Attaches hair follicle to upper dermis

28
Q

What does the arrector pili muscle do

A

When contacted pulls hair upright and dimples skin (Goosebumps)
Compresses sebaceous glands (lubricate skin)
Example of physiological feed forward - skin detects temp and sends message to hypothalamus causing a shiver and activating pili (before core body temp changes)

29
Q

Describe characteristics of a 1st degree burn

A

Superficial - outer layers of epidermis
Red/pink, dry, painful
Skin remains water and bacterial barrier
(e.g. mild sunburn)

30
Q

Describe characteristics of a 2nd degree burn

A

Epidermis & varying amounts of dermis
Red, Painful, moist and blistered
Deeper: Whiteish waxy looking areas. Some tactile receptors may be lost. Loss of Waterproof effect and damage to blood vessels.
Dressing needed to treat

31
Q

Describe characteristics of a 3rd degree burn

A

Full thickness (into subcutaneous tissue - may involve muscle and bone)
Waxy white to deep red or black
Hard, dry, leathery
No pain as sensory nerve endings destroyed
Loss of Waterproof effect and damage to blood vessels
Often skin grafting required to treat

HUBS 192 (36 decks)

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