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Homeostasis
Temperature and Fluid Regulation
| Question | Answer | . |
|---|---|---|
| Homeostasis | The set of processes that maintain the internal environment of an organism within physiological parameters necessary for health and survivals | . |
| Thermoregulation | Terminology - Warm-blooded vs. coldblooded - Poikilotherm vs. homeotherms - Endotherms vs. ectotherms Endothermy is costly, requires more energy and regulatory mechanisms. | |
| Why need thermoregulation | - Most mammals and birds @ 37 deg C - Temperature dependent reactions - Thermoregulation yields increased aerobic capacity | (blank) |
| Mechanisms for Thermoregulation | • Internal regulatory mechanisms - positive feedback -negative feedback | Responses to cold:increased thyroid, metabolism, shivering, constriction of vessels Responses to hot: respiration, perspiration, dilation of vessels |
| Mechanisms for Thermoregulation | Motivated behavior. Categories of behavioral thermoregulation 1) Changing exposure of body surface 2) Changing external insulation 3) Selecting a different surrounding that is less thermally stressful | . |
| Mechanisms for Thermoregulation (3) | • Special adaptations: ear size (small-cold climates, large-hot climates) •physical adaptations: size, shape, carotid rete in dogs - Cool blood from nasal veins surrounds and cools arterial blood, hibernation, topir (squirrels) | |
| Thermoregulatory Circuitry | *Afferents: skin surface, body core, HT *Neural Regions: Spinal cord, brain stem, hypothalamus *Effectors: behavioral- shivering, heat seeking/avoiding behaviors. autonomic-constriction/dilation, sweating, respiration, brown fat stimulation, TH secreti | . |
| Neuroanatomy of Temperature Regulation | 1) Temp sensitive neurons in POA and LH 2) LH lesions abolish behavioral regulation 3) POA lesions abolish autonomic regulation Thermostats: Hypothalamus, Brain Stem, Spinal Cord (broader set zones) *Temperature more tightly regulated by the hypotha | . |
| Volumetric Thirst | -Loss of extracellular fluid -No change in osmolality -Baroreceptors -Responses -Renin, angiotensin, vasopressin -ANS | Circuitry: • Osmoreceptors in hypothalamus • Baroreceptors (mechanoreceptors)in blood vessels and heart • Hormonal regulation at kidneys, hypothalamus, liver, and pituitary |
| Osmometric Thirst | -Loss of intracellular fluid -Due to change in osmolality -Osmoreceptors (maybe) -Responses: thirst, Adrenals: aldosterone | Circuitry • OVLT • Lateral Hypothalamus (magnocellular neurosecretory cells) • Neurosecretory cells secrete vasopressin into blood triggering osmometric thirst. |
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Created by:
brown55
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