Finals: Thermoregulation Flashcards
(25 cards)
Principal Source of Heat in the Body
By-product of metabolism
Determined by metabolic rate
Factors Influencing Heat Production
Basal metabolic rate
Muscle activity
Thyroxine effect
Effects of epinephrine, norepinephrine, and sympathetic stimulation
Chemical activity in cells
Digestion, absorption, and storage of food
Heat generated mainly in liver, brain, heart, and skeletal muscles
Transferred to skin for loss to surroundings
Transfer of Heat from Deep Organs to Skin
Methods of Heat Loss
Radiation
Conduction
Convection
Evaporation
Sweating Mechanism:
Deep subdermal coiled portion secretes primary secretion
Duct portion modifies fluid composition
Reabsorption of ions and water regulated by sweating rate
Secretion Mechanism
Supplied by blood from skin capillaries
High skin flow efficiently conducts heat from body core to skin
Continuous Venous Plexus
Role of Hypothalamus in Thermoregulation:
Body temperature after prolonged exposure to different environmental temperatures
Maintained within normal range despite external variations
Generally between 97°F and 100°F
Critical Body Core Temperature:
Sweating Mechanism:
Anterior hypothalamus initiates sweating
Sympathetic nerve fibers innervate sweat glands
Can also be stimulated by circulating epinephrine or norepinephrine
Stimulation
Sweating Mechanism
Stimulation & Secretion mechanisim
Factors Influencing Heat Loss
Rate of heat conduction from body core to skin
Rate of heat transfer from skin to surroundings
Degree of vasoconstriction affects heat transfer
Response to changes in body core and environmental temperatures
Controlled by Sympathetic Nervous System
Role of Hypothalamus in Thermoregulation:
Response to prolonged exposure to heat
Increase in sweating capacity
Decrease in sodium chloride concentration in sweat
Regulated by aldosterone secretion
Acclimatization of Sweating Mechanism:
Increase firing rate with temperature decrease
Also found in anterior hypothalamic-preoptic area
Cold-Sensitive Neurons:
Mechanism to dissipate heat in animals lacking sweat glands
Initiated by hypothalamus in response to overheating
Panting controlled by pneumotaxic respiratory center in the pons
Heat Loss by Panting:
Increase firing rate with temperature rise
Located in anterior hypothalamic-preoptic area
Heat-Sensitive Neurons:
More cold receptors than warmth receptors
Detect cool and cold temperatures primarily
Mediated by transient receptor potential family of cation channels
Cold and Warmth Receptors in the Skin:
Role of Hypothalamus in Thermoregulation:
Represents the ideal body temperature
Regulated by the hypothalamus
Normal range: 97°F to 100°F
Set Point for Temperature Control:
Located in spinal cord, abdominal viscera, and around great veins
Detect mainly cold temperatures
Prevent hypothermia by responding to core temperature changes
Deep Body Temperature Receptors:
Deep Body Temperature Receptors:
Vasodilation of skin blood vessels
Sweating to increase evaporative heat loss
Inhibition of excess heat production mechanisms
Temperature Decreasing Mechanism:
Deep Body Temperature Receptors:
Skin vasoconstriction
Piloerection
Increase in thermogenesis through shivering and sympathetic excitation
Temperature-Increasing Mechanisms:
