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Integument 2 (Thermoregulation (Thermogenesis (Shivering (Primary…
Integument 2
Thermoregulation
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- Cold - mediated by cold receptors in epidermis
- Warmth - Mediated by warm receptors in dermis
- Both act rapidly
- Perception strongest when skin temp rises or falls - important for thermoregulation
- V.cold and v.hot temp stimulated by pain receptors
Skin/core thermoreceptors :arrow_right: hypothalamus (set point) :arrow_right: responses to change temp :arrow_right: circulatory feedback
Fever - Caused by pyrogens, increase in body temp is when hypothalamic set point temp is shifted to a higher value than normal. Thermoregulatory centre inteprets normal temp as too low so induced thermogenesis
Skin temp varies considerably due to regulation of skin blood flow. Sympathetic NS regulates blood flow to skin. Decreased symp impulses (high ambient temp) :arrow_right: vasodilation. Increased (low ambient temp) :arrow_right: vasocstriction
- Symp NS contracts erector pili muscle
- Evaporation requires heat energy (sweating, panting, wetting body)
- Panting; rapid shallow breathing. Dog, cats, pigs & ruminants can pant. Most water from nasal turbinates.
Thermogenesis
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Non-shivering
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Increased activity of symp NS - Rapid short lived metabolic increase (calorigenic), oxidation of fatty acids in brown adipose tissue
Vitamin D
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Dietary sources: Fat, liver, blood in carnivores. Supplemented in commercial food
7-dehydrocholesterol (7-DHC) in the dermis :arrow_right: (With UV light) :arrow_right: Cholecalciferol/Vit D3
Deficiency: Rickets (poor bone development)
- Dark skin is risk factor, rare in animals but most common in camelids (thick hair coat and dark pigmentation) so need supplements
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Photosensitisation: Abnormal reaction to sunlight due to accumulation of photosensitive compounds beneath the skin
Can be due to:
- Hepatic photosensitivity
- Congenital problems with pigment metabolism
- Ingestion of poisonous plants
Sensory information
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Stimulation :arrow_right: Graded potential (transudction of stimulus to receptor potential) :arrow_right: Action potential :arrow_right: Interpretation of stimulus in CNS
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Brain localises and detects intensity by: Frequency of A.P.s (freq. coding), number of receptors (population coding), different receptors have different thresholds