Department of Physiology, Faculty of Medicine, Masaryk University1
A role of the sympathetic nervous system
in thermoregulation
Physiology II seminar (aVLFY0422s)
Tibor Stračina
Physiology II seminar (aVLFY0422s)2
The presentation is copyrighted work created by employees of
Masaryk University. Any unauthorised reproduction or distribution
of the presentation or individual slides is against the law.
Physiology II seminar (aVLFY0422s)3
Homeotherms vs. poikilotherms
0
10
20
30
40
50
10 20 30 40
Bodytepmerature[°C]
Ambient temperature [°C]
poikilotherm
homeotherm
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Peripheral
Thermoreceptors
Central
Thermoreceptors
HYPOTHALAMUS
(POA)
Thermoregulatory
Centre
Skin
Arterioles
Skeletal
Muscle
Sweat
Glands
Skin Temperature
Deep Brain
Temperature
BodyCoreTemperature
Pilo-
erection
BAT
Ambient
Temperature
Behaviour
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Sympathetic pathways to thermo effectors
̶ Skin circulation (vasomotor activity)
̶ Sweat glands (sweating)
̶ Brown adipose tissue (non-shivering thermogenesis)
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Skin circulation – apical vs. non-apical skin
Apical skin
̶ a-v anastomoses
̶ Vasoconstriction: SNS (NA: α1R)
̶ Vasodilatation: passive
Non-apical skin
̶ Vasoconstriction: SNS (NA: α1R)
̶ Vasodilatation: SNS (Ach-?)
Adopted from:
https://studentconsult.inkling.com/read/
boron-medical-physiology-3e/
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Regulation of sweat secretion
̶ Eccrine sweat glands
̶ Sweating reflex
̶ Efferent p. = sudomotor nn.
̶ sympathetic cholinergic fibers (Ach)
Adopted from:
https://studentconsult.inkling.com/read/
boron-medical-physiology-3e/
Physiology II seminar (aVLFY0422s)8
Activation of brown adipose tissue
̶ SNS – NA: β3R
̶ UCP1
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Adipose tissue:
brown, white
and beige
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Adopted from: doi.org/10.1016/B978-
0-444-63912-7.00016-3
Physiology II lecture (aVLFY0422p)11
Cold-induced thermoregulatory mechanisms
̶ Decrease of heat loss
̶ Behaviour: Decrease of body surface, taking warm clothes
̶ Vasoconstriction in the skin. Horripilation
̶ Inhibition of sweating
̶ Increase of heat production
̶ Skeletal muscles: Intentional movements (behaviour). Shivering
̶ Non-shivering thermogenesis (brown adipose tissue, NA, β3R, UCP1)
̶ Hunger (increase of food intake)
Physiology II lecture (aVLFY0422p)12
Warm-induced thermoregulatory mechanisms
̶ Increase of heat loss/output
̶ Skin vasodilatation
̶ Increase of sweating (evaporation)
̶ Increase of ventilation
̶ Decrease of heat production/intake
̶ Behaviour: Moving out of the sun, taking light clothes. Inactiveness
(decrease of intentional movements), apathy
̶ Loss of appetite
Physiology II seminar (aVLFY0422s)13
̶ Arm pit
̶ Oral cavity (sublingual)
̶ Rectum
̶ External auditory tube
̶ Skin over temporal artery
Adopted from: K.S. Saladin, Anatomy & Physiology—The
Unity of Form and Function, 8th ed. (McGraw-Hill, 2018)
Body temperature measurement
Where and how?
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Rectal vs. skin temperature
Ambient temperature [°C]
Bodytemperature[°C]
23 25 3127 29 33
31
35
33
37
Thermoneutral
zone
Skin temperature
Rectal temperature
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EXPERIMENT 1:
Local cold exposure affects skin temperature
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Result 1
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Result 2
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Cold-induced skin vasoconstriction
Adopted from: doi.org/10.1113/EP087718
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Cold-induced vasoconstriction vs. hypoxia:
Hunting reaction (Lewis, 1930)
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Heat exchange
during exercise
̶ Conduction
̶ Convection
̶ Radiation
̶ Evaporation
Adopted from:
https://studentconsult.inkling.com/read/
boron-medical-physiology-3e/
Physiology II seminar (aVLFY0422s)21
EXPERIMENT 2:
„Central“ vs. „peripheral“ skin temperature
during exercise
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Standardised workload
̶ Ergometry
̶ Exactly: W/kg
̶ Comparatively: MET – metabolic equivalent
̶ Actual metabolic rate / resting metabolic rate in sitting position
̶ 1 MET = consumption of 3.5 ml O2/kg.min
̶ sleeping ≈ 0,9 MET; slow walking ≈ 3-4 MET; fast runnig, sprint ≈ 16 MET
̶ (+) simplicity; (-) inaccuracy
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Indexes of fitness
̶ W170 [W/kg]
̶ VO2 max [mL O2 / (min x kg)]
̶ Aerobic / anaerobic threshold
̶ Fatigue
̶ Failure
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Result 1
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Result 2
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Heat exchange
during exercise
Adopted from:
https://studentconsult.inkling.com/read/
boron-medical-physiology-3e/
Physiology II seminar (aVLFY0422s)27
Skin temperature before, during and after
exercise
̶ Infrared thermography
Adopted from:
doi:10.1088/1742-6596/655/1/012062
Physiology II seminar (aVLFY0422s)28
The presentation is copyrighted work created by employees of
Masaryk University. Any unauthorised reproduction or distribution
of the presentation or individual slides is against the law.