Phys 74 Flashcards

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

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

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

Which two processes primarily determine the body’s total rate of heat loss?

A. Sweating and skeletal muscle activity
B. Heat transfer to skin and environment
C. Skin pigmentation and hair density
D. Ventilation and urinary water loss

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

_____ is an effective insulator because it conducts heat _____ readily than other body tissues.

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

The skin functions as a controlled “radiator” by adjusting how much heat is transferred from the body core to the external environment. Which mechanism primarily regulates this heat transfer?

A. Changes in melanin production
B. Remodeling of sweat gland ducts
C. Changes in skeletal muscle thermogenesis
D. Changes in 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

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

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

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

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

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

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

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

Which description best characterizes the secretory portion of an eccrine sweat gland?

A. Straight tube in the epidermis
B. Flat sac beneath the epidermis
C. Branched acinar gland in the dermis
D. Coiled tubular gland deep in the dermis

After being produced by the secretory portion of an eccrine sweat gland, through which structure does sweat travel to reach the skin surface?

A. Secretory coil
B. Cutaneous venous plexus
C. Duct through the dermis and epidermis
D. Arteriovenous anastomosis

Before heat can be lost from the skin to the environment, it must first travel from the body core to the skin. Which factor most directly limits this transfer?

A. Rate of heat conduction to skin
B. Rate of glucose oxidation
C. Rate of pulmonary gas diffusion
D. Rate of renal filtration

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

A patient develops marked vasoconstriction of the cutaneous blood vessels in response to cold exposure. What effect does this have on heat transfer?

A. Increases heat transfer to the skin
B. Increases insensible water loss
C. Increases reflection of radiant heat
D. Reduces heat delivery to the skin

When sweat glands are only mildly stimulated, sweat moves slowly through the glandular duct. What happens to most of the sodium and chloride in the initial sweat secretion?

A. They are secreted more rapidly
B. They reach the surface unchanged
C. They are reabsorbed by the duct
D. They become concentrated in the duct

At a low sweating rate, water is reabsorbed poorly while sodium and chloride are reabsorbed efficiently from the sweat duct. What happens to substances such as urea, lactate, and potassium in the final sweat?

A. They become very dilute
B. They are rapidly reabsorbed
C. They are nearly eliminated
D. They become highly concentrated

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

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

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

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

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

Thermosensitive transient receptor potential (TRP) proteins detect changes in temperature by permitting positively charged ions to cross the cell membrane. What type of membrane protein are TRP receptors?

A. Cation channels
B. Chloride channels
C. Sodium-potassium pumps
D. G protein–coupled receptors

TRP receptors are temperature-sensitive cation channels that allow ions such as Na⁺ and Ca²⁺ to enter ______ neurons.

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

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

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

In addition to receptors in the skin, deep-body temperature receptors monitor the temperature of blood within which structures?

A. Pulmonary airways only
B. Veins of the lower limbs
C. Cerebral ventricles
D. Great veins of the thorax and upper abdomen

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

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

When body temperature rises above normal, the hypothalamus promotes cutaneous vasodilation to increase heat loss. Which neural mechanism produces this response?

A. Increased adrenal epinephrine release
B. Increased sympathetic vasoconstrictor activity
C. Increased parasympathetic activity to skin
D. Inhibition of sympathetic vasoconstrictor centers

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

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

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

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

Piloerection refers to:
A. Sweating onset
B. Shivering bursts
C. Vasomotor waves
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

When the body is exposed to cold, which combination of responses increases heat production?

A. Sweating and cutaneous vasodilation
B. Inhibition of shivering and metabolism
C. Shivering, sympathetic activation, and thyroxine
D. Radiation and conduction to the environment

The primary shivering motor center lies in the _____ _____ hypothalamus.

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

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

The mitochondrial uncoupling protein in brown adipose tissue allows energy from the proton gradient to be released as heat rather than used to produce ATP. What is this protein also called?

A. Tropomyosin
B. Calmodulin
C. Hemoglobin
D. Thermogenin

Brown fat thermogenesis is triggered mainly by:
A. Parasympathetic norepinephrine
B. Sympathetic norepinephrine
C. Sympathetic epinephrine
D. Parasympathetic epinephrine

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

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

A complete spinal cord transection in the cervical region interrupts descending sympathetic pathways from the hypothalamus. Which thermoregulatory functions are most directly impaired below the level of the lesion?

A. Gastrointestinal motility and secretion
B. Pupillary light reflexes
C. Cutaneous blood flow and sweating
D. Renal blood-flow autoregulation

Substance that produces fever when introduced or released into the blood
A. Antipyretics
B. Kinins
C. Bradykinins
D. Pyrogens

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

Pyrogens act on the hypothalamic thermoregulatory center during fever. What is their primary effect on body-temperature regulation?

A. Lower the temperature set point
B. Raise the temperature set point
C. Permanently suppress sweating
D. Directly produce skin vasodilation

Pyrogens increase hypothalamic _____ _____ activity, raising the temperature set point and causing the body to conserve and generate heat.

Which immune cells primarily phagocytose bacteria and bacterial products during an infection?

A. Neurons and astrocytes
B. Platelets and erythrocytes
C. Hepatocytes and myocytes
D. Neutrophils and macrophages

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

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

Blocking prostaglandin formation will _____ or _____ fever

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

Which complication can further worsen the neurologic and systemic effects of heatstroke?

A. Respiratory alkalosis
B. Decreased leukocyte count
C. Metabolic alkalosis
D. Hypovolemic shock from fluid loss

Which pathologic findings are commonly associated with fatal hyperpyrexia?

A. Pulmonary edema and fibrosis
B. Renal infarction and necrosis
C. Hemorrhage and parenchymal degeneration
D. Bone marrow hyperplasia

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

Which term describes heat production caused by increased cellular metabolism without involuntary skeletal muscle contractions?

A. Shivering thermogenesis
B. Radiant heat transfer
C. Chemical thermogenesis
D. Behavioral heat seeking

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

Brown adipose tissue generates heat through uncoupling protein 1 (UCP1), also called thermogenin. How does UCP1 increase heat production?

A. Increases mitochondrial ATP synthesis
B. Uncouples oxidative phosphorylation
C. Inhibits enzymes of glycolysis
D. Stops the electron transport chain

UCP1 allows protons to reenter the mitochondrial matrix without passing through ATP synthase. The proton gradient’s energy is therefore released as _____ instead of being used to produce _____.

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

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

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

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

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

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

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

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

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

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

A rescue worker wears clothing lined with a thin metallic layer to reduce radiant heat loss. Which metal provides this effect?

A. Copper
B. Silver
C. Aluminum
D. Gold

A bacterial infection suddenly raises the hypothalamic temperature set point. How long may the body require to reach the new set point?

A. Several seconds
B. Several minutes
C. Several hours
D. Several days

Heatstroke may occur at temperatures as low as:

A. 65–70°F
B. 75–80°F
C. 100–105°F
D. 85–90°F

At what dangerously low core temperature does the hypothalamus stop effectively activating heat-preserving responses?

A. 95°F
B. 85°F
C. 75°F
D. 65°F