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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