Quiz 10

Briefly describe the four mechanisms the body uses to transfer metabolic heat to the environment during the process of thermoregulation. pp. 284-287

-Conduction (K) direct contact (sitting on a chilly bench) -Convection (C) liquid or gas movement across a heated surface -Radiation (R) heat loss in the form of infrared rays -Evaporation (E) heat is converted from liquid to vapor

Briefly describe how to achieve heat acclimation. How long does this process usually take? pp. 299-301

9-14 days -well trained need fewer exposures -low to moderate exercise in the heat for 1 hour or more each day for 9 to 14 days. Cardiovascular changes generally occur first.

Briefly describe the three heat-related disorders, including their signs and symptoms and recommended treatments. pp. 295-297

-Heat craps: least serious: Severe, painful craping of large muscles brought on by Na losses, dehydration. Treatment= cooling and saline solutions -Heat Exhaustion: fatigue, dizziness, nausea, vomitting, fainting, weak, rapid pulse. Caused by the cardiovascular system's inability to meet the body's needs when it becomes dehydrated. Thermoregulatory mechanisms are functioning but overwhelmed. Treatment: rest in cooler environment, feet elevate, and NaCl solution -Heatstroke: life threatening, thermoregulatory mechanism has failed. Characterized by: core temp > 40 degrees C (104), confusion, disorientation, unconsciousness. If untreated results in coma and death. Treatment: must cool whole body (ice bath)

How does heat loss and hypothermia risk compare between air and water? p. 304

-Heat loss is 4 times faster in cold water versus cold air! -core temp will remain constant until water temp <32 C (89.6 F) -heat loss increases in moving water but will decrease with exercise

Besides water, what else does sweat contain? Why might this be a potential problem? pp. 292-293

-NA and K, CA, MG -loss of water and electrolytes triggers the release of aldosterone and antidiuretic hormone (ADH) -increasing sweat decreases time for reabsorption and sodium and chloride content of sweat can be considerably higher.

Briefly explain how cardiovascular function has to change during exercise in the heat. What is the main problem that occurs? What is cardiovascular drift? p. 291

-POAH will stimulate the SNS which stimulates the heart and cardiac output will increase -VC occurs in nonessential tissues and more blood is shunted to the skin -skin arterioles will vasodilator which increases C heat loss -because of decrease in SV, HR will increase further. main limit in the heat is the cardiovascular system overload -brain shuts down at 40 degrees celsius (104 degrees Fahrenheit)

What three physiological mechanisms are involved heat production by the body in cold environments? p. 301

-Peripheral vasoconsticution: constricts arterioles, reduces blood flow to the shell of the body and minimizes heat loss. -non-shivering thermogenesis: stimulation of metabolism by the SNS is increased. Increasing heat production -Shivering: rapid, inventory cycle of contractions that increase heat production.

Briefly describe the involvement of arterioles and sweat glands in thermoregulation during exercise in the heat. pp. 289-290

-Skin arterioles will either constrict or dilate (constrictions: minimize heat loss, Dilation: enhance heat loss) -eccrine sweat glands are stimulated sweating enhances evaporative heat loss. more responsive to changes in core temperature than skin temperature -skeletal muscle will be activated to generate additional heat (shivering) -endocrine glands (release of thyroxine from thyroid gland elevating metabolic rate) and catecholamines (epinephrine and norepinephrine)

Briefly explain the concept of windchill and the windchill temperature index.

-based on the cooling effect of wind - presented in a chart showing combinations of air temperature and wind speed. -windchill is not the temperature of the wind of the air (wind chill does NOT change air temperature). -as windchill increases, so does the risk of freezing

What sweating rates can occur during exercise in the heat? How can this affect body weight? pp. 293

-body can lose more than 1 L of sweat per hour per square meter of body surface. (2.5-3.2% body weight). lose a critical amount of body water in only few hours.

What are some precautions to prevent heat-related disorders? pp. 297-298

-competitions and practice should not be held outdoors when WBGT > 28 degrees C or (82.4 F) -Schedule practice early morning or evening -never restrict fluid intake (drink every 15-30 minutes) -minimize clothing (football uniforms, rubberized suits)

Briefly describe the three components that go into determining wet-bulb globe temperature (WBGT). pp. 294-295

-conduction -convection -radiation -evaporation -a measurement of thermal stress. -Dry--bulb T: actual air temperature -Wet-bulb T: reflects evaporative potential -Globe T: measures radiant heat load WBGT equation: .1 T db + .7 T wb + .2 Tg

How does relative humidity influence the ability of the body to regulate body temperature through evaporation? pp. 287-288

-increasing humidity, decreases evaporation. -prolonged evaporation can lead to dehydration

Define hypothermia. p. 302, 305

-low body core temperature -when rectal temperature decreases from normal 37 degrees C to 24 degrees C. temperature below 34.5 degrees C (94) the hypothalamus loses it's ability to regulate body temperature.

What behavioral adjustments are made to increase to prevent heat loss? p. 301

-putting on more clothing seeking shelter.

List the cardiovascular and sweating changes that occur with acclimation. pp. 299-301

-reduce physiological strain -core temperature increases less than before -heart rate increases less than before -start sweating earlier, more widespread sweating, and sweat is more dilute -9-14 days

From what fluid compartment of the body is sweat derived? Why might this be a potential problem? pp. 292-293

-sweat is produced by eccrine glands controlled by the POAH -plasma: -high rates of sweating for a prolonged time reduces blood volume, this limits the volume of blood returning to the heart, increasing heart rate and eventually decreasing cardiac output ,which in turn reduces performance potential.

What region of the brain is primarily responsible for regulating thermoregulation? What two types of sensory receptors send signals to this area of the brain? What division of the nervous system is most important for thermoregulation? pp. 288-290

-two receptors are: peripheral: skin and central: hypothalamus and other brain regions The preoptic-antrior hypothalamus (POAH) is the body's thermostat (receives input from sensory thermoreceptors, when our body deviates, the POAH activates thermoregulatory mechanisms to heat or cool the body

What is the most important mechanism for heat loss during exercise? p. 286

Evaporation

What adaptations take place in sweating and the composition of sweat with acclimation? pp. 293

decrease of NA are lost with sweating -more sodium is reabsorbed and the sweat is more dilute because the glands become more sensitive to aldosterone. Potassium, calcium, and magnesium and not reabsorbed by the sweat glands and similar in both sweat and plasma.