Thermoregulation Flashcards
What is the difference between Core and Peripheral temperature?
Core temperature, i.e. the temperature of the vital organs, is maintained within a narrow range: 36.3 – 37.3 °C
Peripheral temperature is the temperature of the body as recorded on the skin surface
There is a temperature gradient between the core and periphery
What are the characteristics of cutaneous blood flow?
Low metabolic demand
Highly variable blood flow
<1→150mL/100g/min
Regulates core body temperature
What is glaborous skin?
Glabrous skin
Non-hairy skin: nose, lips, ears, fingertips, hand palms, feet soles
Arteriovenous anastomosis
Innervated by sympathetic noradrenergic vasoconstrictor fibres
What is non-glaborous skin?
Non-glabrous skin
Hairy skin
Lack arteriovenous anastomosis
Innervated by both sympathetic noradrenergic vasoconstrictor fibres & sympathetic cholinergic vasodilator fibres
How does ANS activity alter blood flow?
Sympathetic vasoconstrictor nerves to the skin are tonically active
An increase in blood flow in glabrous skin is entirely achieved passively through the release of vasoconstrictor tone
An increase in blood flow in non-glabrous skin is primarily achieved by active vasodilation
How does skin temperature indicate changes in blood flow?
When the body is warm skin blood flow increases to dissipate heat and thus control core body temperature.
Skin radiates heat depending on the level of blood flow.
Thus changes in skin temperature indicate changes in blood flow.
How do perform the sympathetic release test?
Remove all surplus clothing
If your subject’s skin temperature is >25°C at start find another subject
4 sets of control/resting measurements
- Wrap patient tightly top to toe – do not wrap the chair
- Cover head but not forehead or face
- Leave left hand exposed for measurements
- Keep heating until
- Sympathetic release occurs i.e. the middle finger temperature rises and then plateaus (3 similar consecutive readings)
- Or core body temperature is >37.8 °C
- Or sweating is present on forehead for a few minutes
- Or the subject becomes distressed
After release take off blankets and foot warmers and cool subject for 3 measurements
What conditions are related to skin thermoregulation?
Peripheral artery disease- Plaques (atherosclerosis) restrict blood flow to skin, toes and fingers prone to gangrene
Raynaud’s phenomenon- Over-activity of sympathetic nerves or adrenoceptors
– decreased blood flow to skin
– painful/blanched extremities in cold weather
Outline the neuronal control mechanism in glaborous skin
Thermoregulatory inputs > Afferent inputs (Internal/ Skin temp) > CNS ( preoptic-anterior hypothalamus and spinal cord) > Efferent controls ( Noradrenergic vasoconstrictor/vasodilator nerves/ cholinergic submotor nerves) > Cutaneous arterioles and arteriovenous anastomoses/ sweat glands
Outlin the neuronal control mechanism in non- glaborous skin
Non- glabrous skin
Thermoregulatory inputs > Afferent inputs (Internal/skin temp) > CNS (preoptic-anterior hypothalamus and spinal cord) > Efferent controls (Noradrenergic vasoconstrictor nerves/ Cholinergic submotor nerves) > Cutaneous arterioles and arteriovenous anastomoses/ sweat glands
Normal regulation of body temperature
Thermoreceptors in the skin detect an increase in temperature/ blood temperature monitored by central thermoreceptors in the hypothalamus/ thermoreceptors in skin detect a fall in temperature
-Blood temperature increases/ blood temperature decreases
-Hypothalamus
- Heat loss responses
- vasodilation of surface blood capillaries to increase heat loss by radiation
-increased sweating
- erector pili muscles relax- hairs lie flat
- decreased metabolic rate
> Heat conservation responses
- vasoconstriction of surface blood capillaries to reduce heat loss by radiation
- reduced sweating
- erector pili muscles contract- hairs pulled upright
- shivering
- increased metabolic rate
