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HUB2021S > Skin & Thermoregulation > Flashcards

Skin & Thermoregulation Flashcards

1
Q

What is Thermoregulation?

A

The HOMEOSTATIC PROCESS responsible for MAINTAINING OUR BODY TEMPERATURE WITHIN A HEALTHY RANGE, even when the surrounding environmental temperature is different

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2
Q

What is a Homeotherm?

A

(Warm-blooded)

Regulates internal body temperature in spite of environment

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3
Q

What is a Poikilotherms?

A

(Cold-Blooded)

Internal temperature is governed by environment

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4
Q

What is a normal body temperature range?

A

37.5 degC ±1 degC

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5
Q

Why is thermoregulation important?

A
  1. Temperature extremes injure tissues
    • Protein Denaturation:
      o High Temps: Cause alteration of structure of protein mols but not the amino acid sequence
      o Cold Temps: 1- Ice crystals damage cell mechanically; 2-Cytoplasm solute becomes more concentrated = leads to denaturation
  2. It is the fundamental variable affecting biological process
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6
Q

Where is Thermoregulation centrally coordinated from?

A

The Hypothalamus

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7
Q

What is the thermal set point?

A

The set point around which body temperature fluctuates

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8
Q

What are the functions of the skin?

A
  1. Protect - both immune & mechanical
  2. Sensory function
  3. Thermoregulation - both evaporative and insulating
  4. Vit D3 synthesis
  5. Excretion of waste products
  6. Stores water, fat, glucose, VitD
  7. Regulation of fluid status
  8. Keratin production
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9
Q

What is the Integumentary System?

A
  1. Skin (Cutaneous membrane)
  2. Appendages/Accessory structures:
    o Hair
    o Nails
    o Glands
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10
Q

What are the layers of the skin?

A
  1. Epidermis
  2. Dermis
  3. Hypodermis
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11
Q

Which is the most superficial layer of the skin?

A

Epidermis

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12
Q

Epidermis General

A
  • Avascular

- 40-50 rows of stacked squamous epithelial cells

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13
Q

Specialised cells of the Epidermis

A
  • Keratinocytes
  • Melanocytes
  • Langerhans cells
  • Merkel cells
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14
Q

Keratinocytes

A
  • Produce keratin

- Makes skin tough, scaly & water resistant

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15
Q

What is Keratin?

A

A fibrous protein forming the main structural constituents of hair, feathers, hoofs, claws, horns etc.

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16
Q

Melanocytes

A
  • Produce pigment melanin
  • Found in basal layer
  • Protect skin against UV radiation & sunburn
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17
Q

Langerhans Cells

A
  • Immune Function

- Pathogen detection & elimination

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18
Q

Merkel Cells

A
  • Tactile sensation

- Connect to nerve endings in the dermis

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19
Q

What are the Epidermal Layers of the Skin?

A
  1. Stratum Basale (Basal Layer)
  2. Stratum Spinosum
  3. Stratum Granulosum
  4. (Only in hands & feet) Stratum Lucidum
  5. Stratum Corneum
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20
Q

Stratum Basale

A
  • Deepest layer of epidermis

- Contains stem cells, keratinocytes, melanocytes, Merkel cells

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21
Q

Stratum Spinosum

A
  • Langerhans cells, spiny keratinocytes (spine = spinosum)
    o Desmosomes =
    cellular projections on
    keratinocytes
  • Function of desmosomes:
    o Hold keratinocytes
    together
    o Reduce friction
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22
Q

Stratum Granulosum

A
  • Has Keratinocytes (these produce waxy lamellar granules)
  • Far from the dermis and nutrient supply, so start to die
  • Function:
    o Waterproof the skin
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23
Q

Stratum Lucidum

A
  • Found in thicker skin of hands & feet
  • Several rows of clear, dead keratinocytes
  • Is protective
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24
Q

Stratum Corneum

A
  • Top layer of epidermis
  • Multiple rows of flattened dead keratinocytes
  • Continually shed from the surface
  • Replaced by cells arriving from the lower layers
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25
Q

What is the function of the Dermis?

A
  1. Strength

2. Elasticity

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26
Q

Characterisation of the Dermis

A
  • Deep vascular layer of the skin
  • Dense irregular connective tissue
  • Nervous tissue, blood & blood vessels
  • 2 layers:
    o Papillary Layer
    o Reticular Layer
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27
Q

Papillary Layer of Dermis

A
  • Superficial dermal layer between epidermis and dermis
  • Dermal papillae = finger like extensions which protrude superficially towards the dermis
    o Increases SA of
    dermis
  • Contains nerves (touch, pain, temp) & blood vessels (provide nutrients and O2)
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28
Q

Reticular Layer of Dermis

A
  • Thicker and tougher part of dermis
  • Dense irregular connective tissue
  • Many collagen & elastin fibres
  • Gives strength and elasticity
29
Q

Characterisation of the Hypodermis

A
  • Not technically part of skin
  • Layer of loose connective tissue
  • Also known as: Subcutaneous Tissue
30
Q

Function of the Hypodermis

A
  1. Movable link between skin and underlying muscles & bones

2. Fat storage area - energy depot & insulation

31
Q

What is the function of hair?

A
  1. Protects from Uv radiation

2. Assist with insulation by trapping warm air around the skin

32
Q

Hair in thermoregulation

A 
Cold: 
             o Piloerector muscle 
                contracts and hair 
                stands upright - 
                traps air between 
                follicles

Hot:
o Opposite of above

33
Q

What are the 3 types of glands in the Integumentary System?

A 
1. Sudoriferous (sweat) glands
             o Eccrine/merocrine
             o Apocrine
2. Sebaceous glands
3. Ceruminous Glands
             o Produce wax
34
Q

Characterisation of Eccrine Glands

A
  • Produce sweat
  • Sweat delivered via a duct to surface of skin
  • Lowers temperature of the skin
  • Eliminates waste products
  • Highest number in palms & soles
35
Q

Characterisation of Apocrine glands

A
  • Mostly in armpits and pubic regions
  • Ducts extend into follicles of hairs
    o Sweat exits along
    hair shaft
  • Sweat is a thick oily liquid which is digested by bacteria on skin ->BO
36
Q

What is Hyperhidrosis?

A

Production of too much sweat

37
Q

What is Anhidrosis?

A

Production of too little sweat

38
Q

5 Sensory Functions of Cutaneous Sensation

A
  1. Touch
  2. Pressure
  3. Vibration
  4. temperature
  5. Pain
39
Q

5 Cutaneous Receptors

A
  1. Meissner corpuscle:
    o In superficial dermis
    o Mechanoreceptor -
    light touch & vibration
2. Pacinian (Lamellar) Corpuscle:
             o Mechanoreceptor - 
                deep pressure and 
                vibration
             o In deeper dermis
3. Ruffini Organ:
             o Slowly adapting 
                mechanoreceptor in 
                cutaneous tissue
             o Sensitive to stretch
             o Proprioception
4. Merkels Disks (nerve endings):
             o Mechanoreceptors
             o In basal epidermis and 
                hair follicles
             o Feel mechanical 
                pressure, position, 
                shapes and edges
  1. Free nerve endings
40
Q

How does the body gain heat?

A
  1. Basal Metabolic rate
  2. Muscular Activity
  3. Dietary-induced thermogenesis
  4. Environment
  5. Postural changes
41
Q

What is the Basal metabolic rate?

A

The minimal rate of energy expenditure required to maintain homeostasis AT REST

42
Q

What is metabolism? And what is it responsible for controlling?

A

= Process needed to allow the body to function

  • Temp Regulation (thermogenesis)
  • Blood circulation
  • Breathing
  • Neural function
  • Muscular function
43
Q

What hormones affect Basal metabolic rate?

A
  • Epinephrine (adrenaline)
  • Norepinephrine (noradrenaline)
  • Thyroid Hormone

All increase metabolic rate

44
Q

What is Dietary-Induced Thermogenesis?

A

The amount of energy expenditure above resting metabolic rate due to processing of food for use and storage

45
Q

Effect of posture on thermoregulation

A

Hunched posture makes it easier to maintain body temperature

46
Q

Effect of environmental temperature on thermoregulation

A
  • Heat always moves down a gradient

- If environmental temperature is higher than body surface temperature -> heat with enter body

47
Q

Effect of muscular activity on heat production

A

ATP breakdown provides energy for cells and produces heat

48
Q

What are the 4 main mechanisms of heat loss?

A
  1. Radiation
  2. Conduction
  3. Convection
  4. Evaporation
49
Q

What is radiation? (Heat loss mechanism)

A

Emission of electromagnetic heat waves

50
Q

What is conduction?

A

Heat transfer via direct heat transfer, through a liquid, solid or gas.

  • Circulation transports most of the body heat to the shell, but a small amount of heat moves through the tissues via conduction
51
Q

What is convection?

A

The transfer of heat by circulation or movement of the heated particles of a liquid or gas

52
Q

How does a wetsuit assist in thermoregulation?

A

Limits air/water movement over the skin which prevents heat loss through convection

53
Q

What is evaporation?

A

Process whereby a substance changes from a liquid to a gaseous state due to a change in temp and/or pressure

  • Most important mechanism of heat loss
  • Water vaporisation from:
    1. Skin surface
    2. Respiratory tract
54
Q

What are the heat loss responses of the body (In response to high temps)?

A
  • Vasodilation of surface blood capillaries to increase heat loss by radiation
  • Increased sweating
  • Erector pili muscles relax - hairs lie flat
  • Decreased metabolic rate
55
Q

Heat Conservation Responses of the Body (to conserve heat)

A
  • Vasoconstriction of surface blood capillaries to reduce heat loss by radiation
  • Reduced sweating
  • Erector pili muscles contract - hairs pulled upright
  • Shivering
  • Increased metabolic rate
56
Q

What is the effect of a high relative humidity (e.g. 50%)?

A
  • High Relative humidity (RH) (Vapour Pressure) makes evaporating more difficult because of high liquid content in the air.
57
Q

The Circadian Rhythm

A
  • Changes the core temperature at rest by changing the thermoregulatory set point
  • Control metabolism, sleep & other bodily function
  • When temp is low, metabolic rate is at its lowest, gives body time to recover
58
Q

Thermoregulation in the Menstrual Cycle

A
  • The core temperature at rest is changed by changing the thermoregulatory set point
  • Core temp can go up by 0.5 degC at the end of follicle and beginning of luteal phase.
59
Q

How doe we measure temperature?

A
  1. Oral
  2. Auditory/Tympanic (Quite accurate, add 0.5-1 deg to get core temp)
  3. Oesophageal
  4. Rectal (Closest to core)
  5. Skin/Forehead
  6. Core-gut-oral thermistor (Capsule)
60
Q

What is the different between hyperthermia and fever?

A
  • Hyperthermia: Thermal set point does not change (i.e. the normal bodily response as a result of exercise etc.)
  • Fever: Thermal set point is altered
61
Q

Thermoregulation during exercise

A
  1. Increased metabolic activity:
    o Increased Core temp
    o Thermal receptors monitor skin temp
  2. Blood flow changes:
    o Increased skin blood flow (vasodilation)
    o Decreased central blood pressure (Because blood diverted to skin)
62
Q

What is cardiovascular drift?

A

CO = HR x SV

  • A change in cardiovascular responses after several minutes of exercise, but no changes in workload (especially in a warm environ)
  • e.g. Increase in Heart Rate as there is a decrease in SV and mean arterial pressure
63
Q

Mean skin temperature formula

A

T skin = 0.3(Tchest + Tarm) + 0.2(Tthigh + Tleg)

64
Q

Combined Mean Body Temperature formula

A

Tbody =(0.6 x Tcore) + (o.4 x Tskin)

65
Q

Hypothalamus vs skin contribution to blood vessel regulation

A

10:1

66
Q

How can sweat production be increased?

A
  1. Increase the number of sweat glands participating

2. Increased output from each

67
Q

Sweat Rates

A 
Sweat rate (L/hr) =  { [Pre-trial weight (kg) + fluid ingested (L)] – Post-trial weight (kg)} / 
finishing time(min))/(60)
68
Q

Gender differences in thermoregulation

A
  • Men:
    o Higher sweat rates
    o Higher muscle mass
  • Women:
    o Higher surface area to body mass
    o Run slower
69
Q

The Skin-thermal receptors

A
  • Cold & warm-sensitive nerve endings send signals via sympathetic nervous system to anterior hypothalamus
  • Relayed to posterior hypothalamus
  • Controls body temperature in cold
  • 10x more cold sensors than warm sensors in the skin
  • Cold sensors are closer to the surface of the skin

HUB2021S (1 decks)

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