Finals: Thermoregulation

Question 1

Principal Source of Heat in the Body

Answer 1

By-product of metabolism
Determined by metabolic rate

Question 2

Factors Influencing Heat Production

Answer 2

Basal metabolic rate
Muscle activity
Thyroxine effect
Effects of epinephrine, norepinephrine, and sympathetic stimulation
Chemical activity in cells
Digestion, absorption, and storage of food

Question 2

Heat generated mainly in liver, brain, heart, and skeletal muscles
Transferred to skin for loss to surroundings

Answer 2

Transfer of Heat from Deep Organs to Skin

Question 2

Methods of Heat Loss

Answer 2

Radiation
Conduction
Convection
Evaporation

Question 2

Sweating Mechanism:
Deep subdermal coiled portion secretes primary secretion
Duct portion modifies fluid composition
Reabsorption of ions and water regulated by sweating rate

Answer 2

Secretion Mechanism

Question 3

Supplied by blood from skin capillaries
High skin flow efficiently conducts heat from body core to skin

Answer 3

Continuous Venous Plexus

Question 3

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

Answer 3

Critical Body Core Temperature:

Question 3

Sweating Mechanism:
Anterior hypothalamus initiates sweating
Sympathetic nerve fibers innervate sweat glands
Can also be stimulated by circulating epinephrine or norepinephrine

Answer 3

Stimulation

Question 3

Sweating Mechanism

Answer 3

Stimulation & Secretion mechanisim

Question 3

Factors Influencing Heat Loss

Answer 3

Rate of heat conduction from body core to skin
Rate of heat transfer from skin to surroundings

Question 4

Degree of vasoconstriction affects heat transfer
Response to changes in body core and environmental temperatures

Answer 4

Controlled by Sympathetic Nervous System

Question 4

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

Answer 4

Acclimatization of Sweating Mechanism:

Question 4

Increase firing rate with temperature decrease
Also found in anterior hypothalamic-preoptic area

Answer 4

Cold-Sensitive Neurons:

Question 4

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

Answer 4

Heat Loss by Panting:

Question 4

Increase firing rate with temperature rise
Located in anterior hypothalamic-preoptic area

Answer 4

Heat-Sensitive Neurons:

Question 5

More cold receptors than warmth receptors
Detect cool and cold temperatures primarily
Mediated by transient receptor potential family of cation channels

Answer 5

Cold and Warmth Receptors in the Skin:

Question 5

Role of Hypothalamus in Thermoregulation:
Represents the ideal body temperature
Regulated by the hypothalamus
Normal range: 97°F to 100°F

Answer 5

Set Point for Temperature Control:

Question 6

Located in spinal cord, abdominal viscera, and around great veins
Detect mainly cold temperatures
Prevent hypothermia by responding to core temperature changes

Answer 6

Deep Body Temperature Receptors:

Question 6

Deep Body Temperature Receptors:
Vasodilation of skin blood vessels
Sweating to increase evaporative heat loss
Inhibition of excess heat production mechanisms

Answer 6

Temperature Decreasing Mechanism:

Question 6

Deep Body Temperature Receptors:
Skin vasoconstriction
Piloerection
Increase in thermogenesis through shivering and sympathetic excitation

Answer 6

Temperature-Increasing Mechanisms: