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HUBS192 2024 > Lecture 3 > Flashcards

Lecture 3 Flashcards

Skin Physiology

1
Q

What are C-fibres?

A

Unmyelinated axons with small diameters

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2
Q

What are sensory terminals?

A

Free nerve endings which swell at the distal ends of axons

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3
Q

What is an A-delta?

A

Myelinated axons with small diameters

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4
Q

What are different types of sensory terminals?

A

Ion channels and chemically activated channels

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5
Q

What do free nerve endings primarily respond to?

A

Temperature, pain, itching, and the bending of hair in the root hair plexus

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6
Q

What are tactile disks?

A

Free nerve endings in the deepest layer of the epidermis that release serotonin. They have small receptive fields and are sensitive to touch, pressure, texture, shape, edges and low frequency vibration (5-15Hz)

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7
Q

What are tactile corpuscles?

A

Nerves within the papillary layer of the dermis, particularly in hairless skin. They are encapsulated and sensitive to delicate and discriminative touch, light pressure and low frequency vibration (10-50Hz)

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8
Q

What is the capsule of the tactile corpuscle made from?

A

Spiralling / branching unmyelinated sensory terminal are surrounded by modified Schwann cells and then by a thin oval fibrous connect tissue capsule

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9
Q

What does deformation cause in tactile corpuscles?

A

Entry of Na+ ions into the nerve terminal creating an action potential

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10
Q

What are lamellar corpuscles?

A

Nerves found in the dermis and hypodermis of which the single sensory axon terminal lies within concentric layers of collagen fibre and specialised fibroblasts separated by a gelatinous interstitial fluid. They are stimulated by deep pressure and high frequency vibration (250Hz)

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11
Q

What does deformation cause in lamellar corpuscles?

A

Capsule to open and Na+ to enter cell creating an action potential

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12
Q

What are bulbous corpuscles?

A

A network of nerve endings located in the dermis and subcutaneous tissue. They’re intertwined within a core of collagen fibres that are continuous with those of the surrounding dermis. Sensitive to sustained deep pressure and stretching of the skin (proprioception)

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13
Q

What is in the walls of arteries?

A

Smooth muscle tissue

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14
Q

What is smooth muscle tissue controlled by?

A

The sympathetic and parasympathetic nervous system

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15
Q

Constriction of arteries means to…?

A

Reduce blood flow

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16
Q

Dilation of arteries means to…?

A

Increase blood flow

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17
Q

What neurotransmitter do the SNS nerve fibres release?

A

Noradrenaline

18
Q

At the arteries at the cutaneous plexus, what does the NE act on?

A

The alpha 1 adrenergic receptors

19
Q

More SNS activity leads to more activation of the alpha 1 adrenergic receptors which further leads to…?

A

An increase of calcium inside the muscle cells -> more cross-bridges formed and therefore more muscle contraction

20
Q

A decrese in SNS activity leads to less activation of the alpha 1 adrenergic receptors which further leads to…?

A

Relaxation (dilation) of arteries -> increased skin blood flow

21
Q

What is core body temperature?

A

The temperature of the blood within and around the major organs of the body

22
Q

What is the ideal body temperature for your average person?

A

~37 degrees celsius

23
Q

What are the body’s primary mechanisms of heat transfer?

A

Radiation, evaporation, convection, conduction

24
Q

How does radiation occur?

A

Anything not at absolute zero (0k) radiates heat energy through infrared rays. This allows the body to absorb heat from hotter surroundings or give away heat to colder surroundings.

25
Q

How does evaporation occur?

A

The body produces the watery secretion from our eccrine sweat glands as a mechanism for heat loss. As this evaporates off our skin, it takes some heat energy with it.

26
Q

How does convection occur?

A

Our bodies create a heat bubble surrounding us with air in thermal equilibrium, as hot air rises it is replaced with colder air and the process starts again. This makes us feel colder. (wind chill factor)

27
Q

How does conduction occur?

A

Conduction is heat transfer through physical contact. Our bodies create a warm air bubble with the air surrounding us.

28
Q

What are the eccrine sweat glands?

A

The sweat glands found all over the body that produce a watery secretion as a mechanism for heat loss

29
Q

How do the eccrine sweat glands work?

A

SNS nerve fibres release ACh onto mAChRs which are coupled with the g-protein GPCRs to produce the secretion

30
Q

What is nervous sweating?

A

When some eccrine sweat glands are stimulated by adrenaline acting on beta receptors. e.g. sweaty palms

31
Q

Where are the central thermoreceptors located?

A

In the preoptic area of the hypothalamus

32
Q

What happens when body temperature goes above the set point?

A

Decreased SNS activation of alpha 1 receptors on skin blood vessels leading to vasodilation. Increased cholinergic activation of mAChRs on sweat glands leading to sweating. Increased respiratory rate and behavioural changes.

33
Q

When is the body’s heat loss mechanism through radiation, conduction and convection not effective?

A

When environmental temperature > body temperature

34
Q

What happens when body temperature goes below the set point?

A

Shivering thermogenesis, Non-shivering thermogenesis and increased thyroxine

35
Q

What is shivering thermogenesis?

A

Oscillatory contractions of agonist and antagonist muscles. ATP -> ADP + Pi + movement + heat

36
Q

What is non-shivering thermogenesis?

A

Increased SNS nerve activity and increased circulation of adrenaline and noradrenaline from adrenal medulla.
Increased cellular metabolism (glycogenolysis)
‘uncoupling’ of oxidative phosphorylation (brown fat)

37
Q

What does increases thyroxine do?

A

Increases basal metabolic rate in response to TSH and TRH. Only longterm

38
Q

What are the arrector pili muscles?

A

Smooth muscle innervated by the SNS which attaches the hair follicle to upper dermis

39
Q

What does contraction of an arrector pili muscle cause?

A

It pulls the skin up, forming a dimple (goosebump) and compresses sebaceous glands to prevent heat loss via evaporation

40
Q

What are goosebumps an example of?

A

Physiological feed forward

41
Q

What are potential complications of severe burns? Directly to skin function

A

Dehydration and hypovolemic shock, infection / sepsis, hypothermia

42
Q

What are potential complications of severe burns? Related to other aspects of physiology

A

Electrolyte imbalances, hypermetabolism, gastrointestinal ulceration, renal failure, respiratory disfunction

HUBS192 2024 (38 decks)

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