Exam 3 Flashcards by Brianna Tuttle

Efficiency of human body to perform physical work

≈15-30% (slightly higher @ rest ≈34%)

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Remaining 70-85% of expended energy converted to…?

heat

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Typical resting core temp.

≈ 37 degrees C (98.6 degrees F)

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Humans either retain or dissipate heat based upon…?

how close core temp. is to your typical resting level

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The neuro-endrocrine organ responsible for maintaining core temp. as close to 37 C as possible

Hypothalamus

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Temp. regulation centers collectively function as a bi-directional thermostat & are situated on:

hyperthermia: anterior aspect of hypothalamus
hypothermia: posterior aspect of hypothalamus

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Other functions of hypothalamus:

water balance

sugar & fat catabolism

satiety (hunger) center

controls other endocrine glands

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When the core temp. ___________ is interrupted, the temp. center w/in hypothalamus activates several mechanisms which attempt to return the core temp. to normal

homeostasis

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Core temp. too low, it’s increased by…?

heat conservation

2. increased heat production

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Heat conservation initiated via:

decreased sweat rate

- decreased blood flow to extremities & to skin’s surface (DERMAL VASOCONSTRICTION)

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Heat production initiated via:

SHIVERING
(SNS increases catabolic rate 2-4 times resting level)
hypothalamus may trigger THYROID GLAND TO RELEASE THYROXIN which increases catabolic rate
hypothalamus may trigger ADRENAL MEDULLA TO RELEASE CATECHOLAMINES (EPINEPHRINE & NOREPINEPHRINE) which also increase catabolic rate

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When core temp is too high, it’s decreased by…?

Heat dissipation

2. Decreased heat production (possible in resting state)

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Heat dissipation initiated via 2 precursors:

Increased sweat rate

- Increased blood flow to extremities & skin surface (DERMAL VASODILATION)

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After one or both precursors have been initiated, one or more of the following processes may contribute to the dissipation of excess heat via:

Conduction
Convection
Radiation
Evaporation

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After dermal vasodilation: CONDUCTION

Transfer of heat energy via DIRECT SURFACE CONTACT from hotter to cooler surface

-absorption vs. dissipation

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Temperature gradient

transfer of heat energy from hotter to cooler surface temperature

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After dermal vasodilation:

CONVECTION

subsequent to transfer of heat to a gas or liquid, the heated substance rises (temperature gradient) — gas Vs. liquid - absorption Vs. dissipation

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After dermal vasodilation: RADIATION

transfer of heat via electromagnetic waves

(temperature gradient required) - absorption Vs. dissipation

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After increased sweat rate:

EVAPORATION

each gram of vaporized water dissipates ~ .58 kcal of heat energy
called the energy of vaporization OR heat of vaporization

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Do dermal vasodilation & perspiration dissipate heat?

Dermal vasodilation & perspiration do NOT dissipate heat, but one or both are necessary precursors to heat loss.

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Consider these for temperature regulation:

artificial environments (clothes, rooms)
effects of ethyl alcohol

hot vs. cold considerations

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Effects of ethyl alcohol:

dermal vasodilation
diuretic
depressant

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Decreased heat production initiated via:

-Decreased metabolic rate: slowing down or ceasing some physiological functions

(obviously, a person would have to stop exercising in this case)

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Do anatomic &/or physiological differences between males and females make a difference in the responses to hot/humid ambient conditions?

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Yes; but they are not understood

Who has more sweat glands; males or females?

Females; Regardless, females sweat less than males (generally speaking) likely as a result of gender differences in selected hormone levels

Who has more body fat; males or females?

Females typically have ~ 10% more body fat: - much distributed in the subcutaneous region - fat serves as an insulator - greater amounts of subcutaneous fat result in less angular surface area, so less surface area/unit of body mass exists

Who has lower VO2 max; males or females?

- females frequently have lower VO2 max when expressed in absolute or relative terms - the lower the VO2 max , the lower the efficiency of heat-dissipation mechanisms

Males/females typically respond to elevated core temps. w/ greater dermal vasodilation?

Females

Generally speaking about dissipating heat, which gender relies mainly on EVAPORATION, CONDUCTION, RADIATION, & CONVECTION?

- MEN RELY ON EVAPORATION more than females do | - FEMALES RELY ON CONDUCTION, CONVECTION, & RADIATION more than males do

Well-conditioned individuals will be at least partially heat acclimated & so will sweat sooner in response to high core temps. as well as sweat more at any point in time: T or F?

True

Do conditioning levels contribute to a person's ability to respond to heat stress?

yes

Dermal vasodilation proportionally lowers the quantity of blood available to ____ ____ during ___? The elevated sweat rate in males reduces overall blood volume resulting in a similar net effect unless fluids are restored in a timely manner.

SKELETAL MUSCLES during EXERCISE

Males tend to have an advantage in ___, ___ ambient conditions

hot, dry

Females tend to have an advantage in ___, ___ ambient conditions

warm, humid

Dehydration/hypohydration is a condition in which...?

body fluids have been excessively lost via sweating, respiration, blood loss, &/or urinary/GI excretion

Dehydration results in an increase in plasma ___ & ___ concentrations due to a substantial loss of plasma water.

protein & electrolyte

A decrease in total blood vol. results in a decreased ___ ___?

stroke volume (SV)

In order to maintain cardiac output (Q) during submaximal exercise, heart rate (HR) must be ___ when compared to a euhydrated state?

increased

Dehydration also results in a ___ maximal cardiac output?

decreased Q= HR x SV

1. The potential for heat dissipation via conduction, convection, and radiation is reduced by a decrease in total blood volume which results in decreased ___ ___ ___? 2. Which also results in an ___ core temp?

1. Peripheral blood flow | 2. elevated

What percentage of a decrease in body weight via dehydration will reduce physical work capacity & local muscular endurance?

Is strength affected by dehydration?

not really, except extreme cases

1 lb of body weight from fluid losses = ? (how much water)

a pint

Is thirst a good indicator of fluid needs during exercise?

Heat acclimatization is characterized by individuals

- sweating at lower core temps. - sweating more at all elevated core temps. - hypotonic sweat

Heat acclimated people will:

- store less heat during the initial phases of exercise | - will reach a lower thermal steady state

Less dermal blood flow and the availability of more cardiac output for active tissues is caused by ____ ___ ___ ___ ____?

cooler core and skin temps.

If cooler core and skin temps are due to sweat loss, blood volume decreases which means ____ ____ _____.

less cardiac output

What is albumin?

blood borne protein most abundant protein found in blood

During heat acclimatization, degradation of _____ is reduced & production by the liver is at least maintained.

albumin

This results in an ______ in the amount of albumin that is circulating.

increase

Albumin binds with fluid. Each gram of albumin binds with how much blood plasma?

13 ml

Albumin binds with ___ ___ ___s and various hormones.

free fatty acids (FFA)

A fully heat acclimated person will have retained about ____% more plasma than the non-acclimated person because of _____ albumin levels.

20% increased - B/c a greater fluid reserve exists for sweating and the maintenance of SV and Q

This blood adaptation is normally completed within ___ weeks.

A well-trained individual may be about ___% heat acclimated even when conditioning occurs in a cool environment.

about 50% adaptation takes about 1 week

Training activities typically result in ___ core temps, and in turn, will partially acclimate the person to high thermal conditions.

elevated

Performing activities that mainly involve the ___ system will be compromised when ambient conditions are hot/humid, especially if noticeable heat acclimatization is lacking.

CR system

Exam 3 Flashcards

(58 cards)