A nude hiker in dry air can maintain core temperature at ambient:
A. 20°F to 80°F
B. 35°F to 105°F
C. 45°F to 115°F
D. 55°F to 130°F

D. 55°F to 130°F

During exposure to cold wind, which temperature changes most?
A. Core temperature mostly
B. Skin temperature mostly
C. Brain temperature mostly
D. Muscle temperature mostly

B. Skin temperature mostly

Heat production is primarily a by-product of:
A. Conduction
B. Radiation
C. Metabolism
D. Evaporation

C. Metabolism

Total heat loss rate depends mainly on:
A. Sweat rate and shivering
B. Core→skin conduction, skin transfer
C. Skin melanin and hair density
D. Lung ventilation and urine flow

B. Core→skin conduction, skin transfer

Subcutaneous fat reduces heat loss mainly by acting as:
A. Heat radiator
B. Active heater
C. Sweat reservoir
D. Heat insulator

D. Heat insulator

Fat is an effective insulator because it conducts heat:
A. One third as readily
B. Twice as readily
C. Equal to muscle
D. Ten times less

A. One third as readily

In fingers and ears, arterial blood can enter venous plexus via:
A. Capillary loops
B. Lymphatic shunts
C. Arteriovenous anastomoses
D. Venules with valves

C. Arteriovenous anastomoses

Skin serves as a controlled “radiator” mainly through:
A. Melanin production changes
B. Sweat duct remodeling
C. Muscle thermogenesis shifts
D. Blood flow to skin

D. Blood flow to skin

Heat delivery to skin by blood is controlled chiefly by:
A. Arteriolar and AV constriction
B. Venous valve contraction
C. Capillary basement thickening
D. Lymphatic drainage increase

A. Arteriolar and AV constriction

At room temperature, ~60% of heat loss occurs via:
A. Conduction to chair
B. Conduction to air
C. Radiation
D. Evaporation

C. Radiation

Normally, direct conduction to solid objects accounts for about:
A. 3%
B. 10%
C. 25%
D. 60%

A. 3%

Under normal conditions, conduction to air accounts for about:
A. 3%
B. 60%
C. 5%
D. 15%

D. 15%

Even without sweating, insensible water loss is about:
A. 100–200 mL/day
B. 300–400 mL/day
C. 600–700 mL/day
D. 1200–1400 mL/day

C. 600–700 mL/day

Heat exposure triggers sweating via stimulation of the:
A. Posterior hypothalamus
B. Ventromedial hypothalamus
C. Mammillary bodies
D. Anterior preoptic hypothalamus

D. Anterior preoptic hypothalamus

Sweating commands travel from hypothalamus mainly through:
A. Parasympathetic cranial outflow
B. Sympathetic outflow to skin
C. Somatic motor neurons only
D. Sensory afferent fibers

B. Sympathetic outflow to skin

Sweat glands are innervated by sympathetic fibers that are:
A. Adrenergic only
B. Dopaminergic
C. Cholinergic
D. Peptidergic

C. Cholinergic

The neurotransmitter released at sweat glands is:
A. Acetylcholine
B. Norepinephrine
C. Dopamine
D. Epinephrine

A. Acetylcholine

A sweat gland’s secretory portion is best described as:
A. Straight superficial tube
B. Flat epidermal sac
C. Branched acinar gland
D. Deep subdermal coiled tubule

D. Deep subdermal coiled tubule

Sweat reaches skin surface through the:
A. Secretory coil
B. Venous plexus
C. Duct through dermis/epidermis
D. Arteriovenous anastomosis

C. Duct through dermis/epidermis

Heat loss from core to skin is limited most by:
A. Core-to-skin conduction rate
B. Glucose oxidation rate
C. Pulmonary diffusion rate
D. Renal filtration rate

A. Core-to-skin conduction rate

Heat transfer from skin to surroundings occurs by all EXCEPT:
A. Radiation
B. Conduction
C. Metabolism
D. Evaporation

C. Metabolism

A patient with strong cutaneous vasoconstriction will have:
A. Increased core→skin heat conduction
B. Increased insensible evaporation
C. Increased radiant reflection
D. Reduced heat delivery to skin

D. Reduced heat delivery to skin

With slight sweat stimulation, Na⁺ and Cl⁻ are:
A. Secreted rapidly
B. Excreted unchanged
C. Reabsorbed in duct
D. Concentrated in duct

C. Reabsorbed in duct

At low sweating rates, urea/lactate/K⁺ are:
A. Very dilute
B. Rapidly reabsorbed
C. Essentially absent
D. Highly concentrated

D. Highly concentrated

Core temperature regulation relies mainly on:
A. Hormonal set points
B. Hypothalamic feedback control
C. Skin-only reflexes
D. Liver metabolic sensors

B. Hypothalamic feedback control

The main “heat center” region is:
A. Anterior hypothalamic-preoptic area
B. Posterior hypothalamic area
C. Cerebellar vermis
D. Medullary respiratory center

A. Anterior hypothalamic-preoptic area

In the preoptic area, cold-sensitive neurons are:
A. Equal to heat neurons
B. Twice as many
C. About one third as many
D. Nearly absent

C. About one third as many

Heat-sensitive neuron firing with +10°C increases:
A. 10- to 20-fold
B. 2- to 10-fold
C. 0.5- to 2-fold
D. No significant change

B. 2- to 10-fold

The preoptic area can function as a:
A. Pain integration center
B. Respiratory rhythm generator
C. Plasma osmometer center
D. Thermostatic control center

D. Thermostatic control center

TRP thermal sensors are a family of:
A. Cation channels
B. Chloride channels
C. Sodium pumps
D. G-protein receptors

A. Cation channels

TRP thermal channels are found mainly in:
A. Hepatocytes and pancreas
B. Somatosensory neurons, epidermal cells
C. Renal tubules only
D. Myocardial Purkinje cells

B. Somatosensory neurons, epidermal cells

Whole-body skin chilling immediately increases:
A. Sweating rate
B. Skin vasodilation
C. Shivering heat production
D. Heat loss by radiation

C. Shivering heat production

If sweating is occurring, chilling will:
A. Intensify sweating
B. Replace sweating with panting
C. Increase duct secretion
D. Inhibit sweating

D. Inhibit sweating

Chilling reduces heat loss primarily by:
A. Increasing skin permeability
B. Promoting skin vasoconstriction
C. Activating sweat gland ducts
D. Increasing evaporative cooling

B. Promoting skin vasoconstriction

Deep temperature receptors are found mainly in:
A. Spinal cord
B. Cerebral cortex
C. Cerebellum
D. Retina

A. Spinal cord

Deep temperature receptors also exist in/around:
A. Lungs only
B. Lower limb veins
C. Cerebral ventricles
D. Great veins upper abdomen/thorax

D. Great veins upper abdomen/thorax

Preoptic temperature signals are transmitted to the:
A. Cerebellar cortex
B. Basal ganglia
C. Posterior hypothalamus
D. Pineal gland

C. Posterior hypothalamus

First major heat-loss response to overheating is:
A. Skin vasodilation
B. Piloerection
C. Shivering
D. Thyroxine release

A. Skin vasodilation

Skin vasodilation during overheating occurs via:
A. Increased adrenal epinephrine
B. Increased posterior sympathetic drive
C. Increased vagal efferents
D. Inhibition of posterior sympathetic centers

D. Inhibition of posterior sympathetic centers

The second major heat-loss mechanism is:
A. Piloerection
B. Shivering
C. Sweating
D. Thyroxine release

C. Sweating

The third major heat-loss response is decreased:
A. Skin blood flow
B. Heat production
C. Radiation to air
D. Venous return

B. Heat production

Decreased heat production occurs by inhibiting:
A. Shivering and chemical thermogenesis
B. Sweat duct reabsorption
C. TRP channel opening
D. Na⁺/K⁺ ATPase activity

A. Shivering and chemical thermogenesis

When the body is too cold, the first response is:
A. Sweating
B. Skin vasodilation
C. Skin vasoconstriction
D. Decreased sympathetic outflow

C. Skin vasoconstriction

Cold-induced vasoconstriction is caused by:
A. Inhibited posterior sympathetic centers
B. Stimulated posterior sympathetic centers
C. Increased parasympathetic tone
D. TRP channel blockade

B. Stimulated posterior sympathetic centers

Piloerection refers to:
A. Sweating onset
B. Shivering bursts
C. Vasomotor waves
D. Hairs standing on end

D. Hairs standing on end

Piloerection is produced by contraction of:
A. Arrector pili muscles
B. Ciliary smooth muscle
C. Iris circular muscle
D. Sweat gland ducts

A. Arrector pili muscles

Increased thermogenesis in cold occurs via:
A. Sweating, vasodilation
B. Shivering inhibition, cooling
C. Shivering, SNS, thyroxine
D. Radiation, conduction

C. Shivering, SNS, thyroxine

The primary shivering motor center lies in:
A. Ventral anterior hypothalamus
B. Dorsomedial posterior hypothalamus
C. Lateral preoptic cortex
D. Dorsal medulla

B. Dorsomedial posterior hypothalamus

Rapid catecholamine-driven metabolic heat is called:
A. Shivering thermogenesis
B. Evaporative cooling
C. Chemical thermogenesis
D. Radiant heat loss

C. Chemical thermogenesis

Chemical thermogenesis magnitude is proportional to:
A. Brown fat amount
B. Skin thickness
C. Sweating rate
D. Core blood volume

A. Brown fat amount

Mitochondrial uncoupling protein is also called:
A. Tropomyosin
B. Calmodulin
C. Hemoglobin
D. Thermogenin

D. Thermogenin

Brown fat thermogenesis is triggered mainly by:
A. Parasympathetic acetylcholine
B. Sympathetic norepinephrine
C. Somatic motor firing
D. Cortisol release

B. Sympathetic norepinephrine

Cooling the anterior preoptic area increases:
A. Cortisol secretion
B. ADH release
C. TRH production
D. Insulin release

C. TRH production

Thyroxine increases chemical thermogenesis mainly by:
A. Raising cellular metabolism
B. Increasing skin sweating
C. Decreasing blood viscosity
D. Reducing mitochondrial number

A. Raising cellular metabolism

Temperature control “feedback gain” equals:
A. ΔCore/ΔEnv minus 1
B. ΔEnv/ΔCore minus 1
C. ΔEnv × ΔCore minus 1
D. ΔCore × ΔEnv minus 1

B. ΔEnv/ΔCore minus 1

Neck spinal transection above sympathetic outflow impairs:
A. GI motility control
B. Pupillary reflexes
C. Skin blood flow, sweating control
D. Renal autoregulation control

C. Skin blood flow, sweating control

Substances raising hypothalamic set point are:
A. Antipyretics
B. Kinins
C. Bradykinins
D. Pyrogens

D. Pyrogens

Pyrogens commonly arise from:
A. Bacteria and degenerating tissues
B. Normal muscle activity
C. Excess skin sweating
D. Low ambient humidity

A. Bacteria and degenerating tissues

Direct hypothalamic pyrogens immediately:
A. Lower set point
B. Raise set point
C. Stop sweating
D. Induce vasodilation

B. Raise set point

Bacterial products are phagocytized mainly by:
A. Neurons and astrocytes
B. Platelets and erythrocytes
C. Hepatocytes and myocytes
D. Leukocytes, macrophages, NK cells

D. Leukocytes, macrophages, NK cells

“Leukocyte pyrogen” is also called:
A. TNF-alpha
B. IL-6
C. IL-1
D. Histamine

C. IL-1

IL-1 causes fever primarily by inducing:
A. Leukotriene B4
B. Prostaglandin E2
C. Nitric oxide
D. Bradykinin

B. Prostaglandin E2

Blocking prostaglandin formation will:
A. Reduce or abolish fever
B. Increase fever duration
C. Prevent shivering only
D. Trigger sweating only

A. Reduce or abolish fever

Prolonged high temperature can result from:
A. Pituitary adenoma
B. Stroke in cerebellum
C. Hypothalamic compression by tumor
D. Spinal cord demyelination

C. Hypothalamic compression by tumor

Heatstroke symptoms are worsened by:
A. Respiratory alkalosis
B. Leukopenia
C. Metabolic alkalosis
D. Circulatory shock from sweating

D. Circulatory shock from sweating

Hyperpyrexia fatal pathology includes:
A. Pulmonary edema, parenchymal degeneration
B. Renal infarcts, parenchymal degeneration
C. Hemorrhages, parenchymal degeneration
D. Bone marrow hyperplasia

C. Hemorrhages, parenchymal degeneration

Artificial cooling is used during:
A. Bronchoscopy procedures
B. Heart surgery to stop heart
C. Colonoscopy procedures
D. Cataract surgery cases

B. Heart surgery to stop heart

“Nonshivering thermogenesis” equals:
A. Shivering thermogenesis
B. Radiant heat loss
C. Chemical thermogenesis
D. Behavioral heat seeking

C. Chemical thermogenesis

Sympathetic stimulation raises metabolism mainly via:
A. Norepinephrine and epinephrine
B. Acetylcholine and histamine
C. Dopamine and serotonin
D. GABA and glycine

A. Norepinephrine and epinephrine

Brown fat heat production rises because UCP:
A. Raises ATP synthesis
B. Uncouples oxidative phosphorylation
C. Blocks glycolysis enzymes
D. Stops electron transport chain

B. Uncouples oxidative phosphorylation

Infant brown fat is found mainly in:
A. Abdominal mesentery
B. Popliteal fossa
C. Facial subcutaneous tissue
D. Interscapular space

D. Interscapular space

Cooling preoptic area increases TRH, leading to:
A. Increased thyroxine release
B. Decreased thyroxine release
C. Increased insulin release
D. Decreased cortisol release

A. Increased thyroxine release

Thyroxine increases thermogenesis by:
A. Increasing sweat salt loss
B. Reducing skin blood flow
C. Increasing cellular metabolic rate
D. Blocking shivering motor output

C. Increasing cellular metabolic rate

Poor thermoregulation after neck transection occurs because:
A. Skin blood flow increases
B. Hypothalamus loses sweat control
C. Adrenal medulla stops secreting
D. Skin temperature equals core

B. Hypothalamus loses sweat control

A classic bacterial pyrogen example is:
A. Myosin fragments
B. Collagen peptides
C. Lipopolysaccharide endotoxin
D. Serum albumin

C. Lipopolysaccharide endotoxin

Aspirin reduces fever mainly by:
A. Blocking TRH secretion
B. Inhibiting prostaglandin synthesis
C. Increasing brown fat amount
D. Activating shivering center

B. Inhibiting prostaglandin synthesis

Hypothalamic compression causing hyperthermia is due to:
A. Brain tumor pressure
B. Viral myocarditis
C. Renal tubular necrosis
D. Peripheral neuropathy

A. Brain tumor pressure

Sudden set point increases can be triggered by:
A. Hypoglycemia only
B. Hypercalcemia only
C. Dehydration, pyrogens, tissue damage
D. Hyperventilation only

C. Dehydration, pyrogens, tissue damage

Hyperpyrexia damages tissues especially in the:
A. Skin
B. Brain
C. Spleen
D. Thyroid

B. Brain

Slight sweat stimulation causes low NaCl because duct:
A. Stops secreting precursor fluid
B. Actively secretes chloride outward
C. Increases sweat gland diameter
D. Near-complete NaCl reabsorption

D. Near-complete NaCl reabsorption

At low sweating rates, urea/lactate/K become concentrated because:
A. Water reabsorbed, solutes retained
B. Solutes reabsorbed, water lost
C. Duct secretes extra potassium
D. Precursor fluid lacks electrolytes

A. Water reabsorbed, solutes retained

Deep temperature receptors are also found in:
A. Retina and optic nerve
B. Cerebellar cortex
C. Abdominal viscera
D. Distal skin only

C. Abdominal viscera

Preoptic temperature signals are relayed into the:
A. Anterior pituitary gland
B. Posterior hypothalamus
C. Basal ganglia circuits
D. Medullary pyramids

B. Posterior hypothalamus

Shivering center is normally inhibited by:
A. Cold skin receptors
B. Posterior hypothalamic centers
C. Spinal cord thermoreceptors
D. Anterior preoptic heat center

D. Anterior preoptic heat center

Chemical thermogenesis increases metabolism via:
A. Sympathetic stimulation or catecholamines
B. Parasympathetic cholinergic firing
C. Cortical motor pathway discharge
D. Local sweat gland activation

A. Sympathetic stimulation or catecholamines

Poor thermoregulation after neck transection occurs because hypothalamus can’t control:
A. Renal filtration and urine output
B. GI secretion and absorption
C. Pupillary light reflexes
D. Skin blood flow and sweating

D. Skin blood flow and sweating