KIN 321 Exam 2

What is vascular smooth muscle designed to do

What is vascular smooth muscle designed to do

regulate blood flow to active tissue maintain systemic blood pressure

What are the two primary sources of fluid loss?

urine Sweat

High intensity exercise produces enough heat to raise body temperature _____ every ______ minutes. within 20 minutes it is life threatening and 40 minutes fatal

1 degree celsius 4-5

A majority of the produced heat is transferred where via what

core, venous blood

Greater than what % BW lost from dehydration is considered extremely dangerous?

7%+

When the ambient temperature is higher than the skin, what are some unique sources of heat gain

Radiation convection conduction (If the skin was hotter than environment these would contribute to heat loss)

Core temperature is about _____ degrees celsius

37

Slight Dehydration can

significantly decrease VO2max and overall aerobic performance

Is thirst a reliable sign of fluid need

NO IT IS NOT

Dehydration is defined as

percentage loss of body weight

Signs of acclimatization

decreased HR ncreased Sweat rate

When should heat acclimatization occur

1-2 months precomp

most adaptations occur within

1-2 weeks

What ambvient temperatures will be ideal for acclimatization

38.5

Heat will move down a gradient via

radiation conduction convection

Allcimatizstion to exercise in the heat will

increase plasma volume

Sweat becomes ____ with acclimatization

diluted to preserve elecgtrolytes

You start sweating earlier or later when acclimatized

earlier

What are the two competing demands on the CVsystem during exercise

o2 and nutrient delivery

heat delivery to the periphrey for cooling

Sweat is largely derived from

PLASMA

What happens to venous return during exercise in the heat

increased HR to maintain cardiac output

What happens to plasma volume during exercise in the heat

decreases--> high blood pressure and sweat loss

As exercise intensity increases past 60W

heat production surpasses heat lost

The hypothalamus acts as the

thermostat Heatloss--> vasodilation Heat conservation--> vasoconstriction +shivering

With exercise what is the gold standard

rectal

Which method is relied on more heavily as ambient temperature increases

evaporation

What is counterproductive sweating

water loss without cooling in hot, humid environment

Evaporation is heavily influenced by

relative humidity (dryer the air the easier the sweat)

What is the major mechanism of heat loss

the EVAPORATION of sweat off the skin (NOT WIPING IT OFF)

Radiation accounts for ______ loss of heat in a neutral environment at rest

60%

What improves the effectiveness of convection

movement of water or air across skin

When the ambient temperature is higher than skin temperature how is heat lost

solely evaporation

When the ambient temperature is less than skin temperature

Heat is lost through evaporation, radiation, conduction and convection

What is heat exhaustion characterized by

rapid/weak pulse hypotension (fluid loss and vasodilation to skin and muscle) faintness profuse sweating

How is heat exhaustion treated?

Fluid replacement and cool environment

What is heat syncope?

loss of consciousness with cessation of exercise in the heat (independent or secondary to heat exhaustion)

What is heat stroke?

failure of the hypothalamic temp regulation--> decreased sweat rate-->massive heat storage

What is the mortality rate of heat stroke? Why is it so high?

20%+ Heart failure and cerebral edema

What is exercise associated hyponatremia?

The dilution of plasma Na+ below 135mmol/L

what are some symptoms of EAH

altered CNS function--> weakness, dizziness, lethargy, vomiting, headache, seizure

Is EAH more prevalent in competitive athletes vs recreational?

recreational

What is the largest predisposing factor of EAH

substantial weight gain from fluids

How is sweat rate calculated?

[BW chane + (Fluid intake-excretion)]/time as a fraction of an hour

What is the general recommendation for pre exercise hydration?

6mL H2O/kg BW every 2-3 hours in the days leading up to the event

Pre event hydration guidelines

16-24 fluid ounces 2 hours before 12 ounces 15 min before

Intraworkout hydration guidelines

8-12 ounces every 15 min during practice or event lasting longer than 1 hour (can be 6-8% CHO solution w some electrolytes)

What should be the target hydration after exercise

consume 1.5L for every Kg weight lost

Vascular smooth muscle vs skeletal muscle fibers

Smaller not striated contract more slowly capable of maintaining vascular tone with little energy

What are the three factors that control vascular smooth muscle

Local Humoral Neural

Why is there always slight vasoconstriction?

To guarantee adequate blood pressure and flow

What is rate of blood flow determined by?

Blood pressure

What is total peripheral resistance

the resistance to flow in the circulation

What is TPR equal to

BP=Q * TPR

Increased TPR leads to

hypertension

When CO (Q) is constant (steady state, rest) blood flow (BP) is regulated by

changes in TPR via vasoconstriction or dilation

What is Poiseuilles equation (describes flow in a tube)

Flow= (Pressure of Blood leaving heart- Pressure at distant site)piR^4/8LV

What effect will increasing the radius of a blood vessel have on blood flow?

Vasodilation-->increase BF

What effect will increasing the pressure difference have on blood flow

increased BF

Length is

unchanged

What effect will being well hydrated have on blood flow?

being well hydrated leads to an increase in blood flow due to a lower viscosity

How do you accomplish a 10-15 fold increase in blood flow to active skeletal muscle during exercise?

Increase Cardiac Output Vasodilation of active muscles Maintain hydration status

What are some local vasodilatory metabolites?

Increased H+ (dec. pH) Inc. K+ Inc. Adenosine and Lactate Inc. PCO2

Blood flow varies to the ___ power of radius

4th power (small changes in radius lead to big changes in blood flow)

A _% reduction in radius will lead to a __% reduced flow

16/50

During active exercise where does blood flow get restricted to in order to give the active muscles blood

The gut gets reduced BF

What percentage of blood goes to muscles during exercise

80-85%

During exercise you vasoconstrict ______ and vasodilate at _______

gut, active muscle

Local control is only

vasodilatory

What provides the signal to link local metabolism to blood flow?

sympathetic innervation @ adrenal medulla

Blood flow increases exponentially with

increased rate of metabolism

Vasodilators

increased adenosine, lactate, hydrogen ion, potassium, PCO2 Decreased PO2

Endothelium likely potentiates local vasodilation via the release of

Nitric Oxide

What causes NO release

shear stress Response to CATS

What increases NO secretion

endurance training

Reactive hyperemia is an example of

local vasodilation

Reduced blood flow through the kidney leads to the secretion of what

renin

What is the function of renin

splits angiotensinogen from the liver to produce angiotensin I

What is the function of ACE (angiotensin converting enzymes)

from the lungs converts angiotensin I into Angiotensin II and III

What is angiotensin II

a potent vasoconstrictor

What hormone is secreted by the adrenal cortex in response to Angiotensin II

aldosterone---> increased water retention by the kidneys

Overall dehydration leads to

increased blood pressure (this same effect from the renin angiotensin system can result from huge loss of blood)

Humoral control of blood flow results in

both vasodilation and constriction

Neural control is almost exclusively

vasoconstrictor

Do sympathetic nerve fibers innervate capillaries

NO (they innervate all other blood vessels)

Neural control results in

large unrefined changes

Two medications that are vasodilators

ACE inhibitors ARB (angiotensin receptor blocker---> blocks AII receptor)

What parts of the body are most heavily innervated ? (blood vessel wise)

Kidney, gut, spleen

What parts of the body are least innervated ?( blood vessel wise)

muscle, heart and brain

Neural pushes blood flow to skeletal muscle generally, what pushes it to the active site

local control

Does neural control distinguish between active/inactive skeletal muscle

No it does not

Spinal cord injury may result in

lack of neural control so BP drops during exercise due to local vasodilation without compensatory vasoconstriction from neural

The left ventricle gets blood from

left coronary artery

The right ventricle gets blood from

right artery

Myocardial BF may increase ______ from rest to max exercise because of

3x bc of a 5-20% NO primarily, secondarily from humoral/neural

Diastolic BP should stay same or

decrease during exercise

Ultimate goal of neural regulation of heart is

to maintain arterial blood pressure

The ______ nervous system has primary neural control of the cardiac function

autonomic (heart is innervated by both sympathetic and parasympathetic)

Sympathetic vasoconstriction (low-level input from vasoconstrictor area) is partially responsible for

resting BP

Which division of the autonomic nervous system innervates the SA and AV node and atria (usually lowers the HR by inihibiting SA node)

Parasympathetic NS (dominant at rest)

Which division of the autonomic system innervates the SA AV and ventricular myocardium (increase HR and SV)

Sympathetic NS