KIN 421 Test 1

What kind of science is exphys?

An applied science
Chem, biochem and physics of the human body in response to acute or chronic exercise

Define homeostasis

maintenance of the internal environment of the body

Does homeostasis mean that the environment remains absolutely constant?

NO
It represents a dynamic consistency around a "set" point

Are steady state and homeostasis synonymous?

No, a steady state may be reached during times of great stress but that does not mean it is part of maintaining homeostasis.
Ex: Heart rate during exercise increases in a stepwise fashion (steady state) but it is not maintained at the normal resting value (homeostasis)

What is a biological control system?

a series of interconnected components that serve to maintain a physical or chemical variable of the body at or near a constant value

What are the three components of a biological control system?

Receptor
Integrating center
Effector

What is a receptor in a biological control system? provide a example

This component must be capable of detecting a change in the variable. It responds and sends a message to the integrating center. Example: Aortic/Carotid sinus sensing a increase in blood pressure

What is a integrating center in the context of a biological control system? Example?

A integrating center assesses the nature and magnitude of the stimulus and sends an appropriate output message to the effector.
EX: The aortic sinus senses a increase in blood pressure and sends a signal to the cardiovascular control center in the medulla. The medulla will then send an output message

What is an effector in the context of a biological control system? Example?

An effector corrects the disturbance by responding in a manner that changes the internal environment back to normal. EX: Cardiovascular control center sends a message to the heart blood vessels kidneys etc to moderate blood pressure if too high or low.

Define positive feedback and give an example

The final response perpetuates more of the initial stimulus
EX: exercise in the heat--> body temp rises--> cutaneous blood flow increases--> blood gets heated more as it goes to the skin--> loss of water is increased--> dehydration---> body temperature increases even more

Define negative feedback and give an example

The final response is in opposition of the initial stimulus
EX: High BP--> carotid/aortic sinus senses and sends message to medullary CV control center--> a message is sent to inhibit the cardioacceleratory center, stimulate the cardioinhibitory, stimulate the medial depressor area (vasodilate)---> results in a decrease in BP

What is blood pressure a function of?

BP= Cardiac output * Peripheral resistance

What factor has a very potent effect on peripheral resistance?

Vessel radius (Rp varies inversely to the 4th power of vessel radius)

What factors influence Rp?

Vessel radius
Sheer length
Viscosity of blood (inc RBCs, EPO)
Vessel stiffness
Vasomotor tone

What are the 3 layers of a blood vessel?

Tunica intima (innermost endothelial tissues one cell thick)
Tunica media (smooth muscle/elastic tissue)
Tunica adventitia/externa (outermost)

What are the resistance vessels?

arteries and arterioles

What are capacitance vessels?

veins and venules

What is the effect of a increase in vasomotor tone on capacitance vessels?

Vasoconstrictive--> the capacitance vessel size decreases--> This would increase venous return

If the size of the capacitance vessels is increased, what would the effect be on venous return?

The venous return decreases (bad)

What receptor is responsible for detecting increases/decreases in blood pressure?

Baroreceptors
The aortic and carotid sinus
A sinus is a cavity or channel in which these pressure sensing nerve endings lay

What activates a baroreceptor?

vessel wall deformation, modifications in vessel wall stretch, and changing pressure

Provide a detailed explanation of the homeostatic regulation of HIGH blood pressure.

A stretch in the vessel wall is sensed by the aortic sinus or RT internal carotid sinus (RECEPTOR)
A signal is sent from the sinus node of herring to the glossopharyngeal nerve to the medullary cardiovascular center
Stimulate cardioinhibitory area
Inhibit cardio acceleratory area
Stimulate the medial depressor area
Inhibit the lateral pressor area.

What nerve conducts the signal from the RT internal carotid sinus to the medullary CV center? What about the aortic?

Glossopharyngeal
Vagus

What are the components of the cardiovascular center (ventrolateral medulla) AKA servomechanisms

Cardio acceleratory area (positive chronotropic)
Cardioinhibitory area (negative chronotropic)
Lateral Pressor area (vasoconstrict)
Medial depressor area (vasodilate)

What happens during fainting or hemorrhaging?

The baroreceptors are unloaded

What occurs when the baroreceptors detect too low of a BP? (describe the servomechanisms)

Stimulation of the cardioacceleratory center and the lateral pressor area (vasoconstriction)
Inhibition of the cardioinhibitory center and medial depressor area (vasodilation)

Is negative feedback characteristic of a stable or unstable environment?

Stable

During inspiration there is a _______ chronotropic and ________ inotropic effect
this results in a ________ in HR and a ________ in SV

positive, psoitive, increase, increase

What does a carotid massage mimic?

A carotid massage mimics an increased pressure on the carotid sinus
This will serve to decrease the heart rate and increase vasodilation.

When would a carotid massage be used?

When someone is in sinus tachycardia (HR>100BPM)

Is PCO2 higher in our bodies or the surrounding air?

Our bodies

What is the most potent stimulus for respiration?

CO2

What does a RER of 1 indicate?

Carbs are main fuel source

What does a RER of .7 indicate?

Fats are main fuel source

What is minute ventilation?

The amount of air expired in 1 min
(air expired/breath)*(breaths/min)

What is Minute ventilation at rest? At exercise? What can be the expected increase (_________ fold increase) in Ve?

6L/min= (.5L/breath*12-15 breath/min)
120L/min= (2L air/breath *60 breath/min)

20 fold increase!!

Increase in metabolism from rest to peak exercise

20-25x

During exercise what occurs with respect to PCO2?

It increases

What detects the increase in CO2 during exercise?

Chemoreceptors

Where are the chemoreceptors located?

The bifurcation of the common carotid arteries (Carotid body) and in the aortic arch (Aortic body)

What are the Afferent nerves associated with the signaling of the chemoreceptors to the brain?

Carotid sinus nerve
Vagus nerve

What is the integrating center in the context of the homeostatic regulation of PCO2?

Medulla respiratory center

What are the receptors associated with the homeostatic regulation of PCO2?

Carotid body
Aortic body

During exercise what occurs in an attempt to reduce PCO2

Respiratory rate and tidal volume increase

Hypercapnea of exercise refers to the ______ in PCO2, what other metabolite increases?

increase, H+

H+ can cross the blood brain barrier (T/F)

False

CO2 can cross the blood brain barrier? (T/F)

True

The CO2 in the brain enhances_____ and the _______ is very sensitive to CO2

cerebral perfusion
cerebral vascular bed

What happens to animals with resected chemoreceptors?

Hypercapnea associated with a FALL in Ve (it should increase due to the overwhelming presence of CO2)

How is Ve increased once the signal is received at the medulla respiratory center?

A signal is sent to the phrenic nerve to stimulate the diaphragm to descend deeper and faster/more frequently.

When hypercapnia is accompanied by hypoxia, which is more serious?

The hypoxic environment

When hypercapnia is accompanied by hypoxia, will the stimulatory effects of CO2 on the carotid and aortic bodies still be present?

No, there will be no increase in Ve, TV or R and there will be a decrease in vasomotor tone (hypotension)

Give an example of when hypercapnia and hypoxia could occur AND be possibly beneficial

A swimmer hyperventilating before a race
They will have a decreased stimulus to breathe so they don't have to interrupt their stroke to take a breath.

When is hypercapnia associated with a decrease in ventilation? (HER QUESTIONS)

Hypoxia

Why would older people have blunted baroreceptor activity? What are the clinical implications of this on BP? (HER QUESTIONS)

Aging decreases vagal tone and increases vessel stiffness
Exercise to increase vagal tone and vessel elasticity

Where is blood pressure highest?(HER QUESTIONS)

The right arm because there are more bifurcations

Are baroreceptors more responsive to rising or falling temperatures? (HER QUESTIONS)

Rising

Are baroreceptors operant during exercise? (HER QUESTIONS)

Yes

How do baroreceptors work to allow completion of exercise while preventing too unstable an environment? (HER QUESTIONS)

Baroreceptors operate primarily on the peripheral resistance side by increasing Rp to non exercising tissues early in exercise to prevent a BP drop due to local vasodilation @ active tissues. During more intense exercise baroreceptors act to decrease Rp by vasodilating active issues

What is pulse pressure?

difference between systolic and diastolic pressure

What does a elevated pulse pressure indicate (SBP>140, DBP

reduced vascular compliance of the large arteries. This also means a less compliant left ventricle, myocardial wall stress, O2 demand and higher ventricular workload.

An increased mean arterial pressure indicates that

the heart has to work harder during systole to eject a given amount of blood.

What can high MAP lead to?

Isolated systolic hypertension

What is mean arterial pressure (MAP)?

average pressure in the arteries throughout the cardiac cycle

DBP + 1/3 pulse press

What does a reduced DBP indicate?

Increased aortic stiffness
Lower perfusion pressure
reduced myocardial oxygen consumption
Lower mocardial O2 can increase ones risk for Myocardial infarction and ischemia.

During exercise SBP significantly_______

increases

During exercise DBP has_______

minor changes

For hypertensives BP goes up ________ as normotensives except that their SBP and DBP start________

the same

higher than normotensives

What can sometimes occur for hypertensives with respect to their DBP?

Increase due to the lost ability to vasodilate

DBP in hypertensives is significantly ________ compared to normotensives due to ________

higher, their inability to reduce Rp

Is the absolute increase in BP between hyper and normotensives the same?

Yes

What happens if BP is too high before exercise?

A 5-10 minute warm-up should be used. The BP will increase at first then go back down during the warm up. Good for hypertensives and it helps achieve a vasodilatory effect before exercise to avoid excessive pressure elevations.

How can a 5-10 minute warmup be beneficial in preventing excessive pressure elevations in hypertensives (and normotensives)?

It will produce a vasodilatory effect at active tissues which will help reduce BP.

After a bout of exercise how long does it take your BP to drop back down?

Normotensives 1-4 min
Hyper: 5 min

What sensory organ counteracts vasodilation in working muscles? How do they do this?

The Baroreceptors via vasoconstriction @ inactive tissues early in exercise to prevent a sharp BP decrease

During mild or early exercise, what is the primary role of the baroreceptor?

To cause vasoconstriction at inactive muscles so the vasodilation at active muscles does not cause a sharp decrease in BP

Do baroreceptors affect cardiac output during exercise?

No they do not
Q is more afected by mechanoreceptors (mechanical pressure, GTOs, muscle spindles etc). Baroreceptors primarily act on Rp during exercise.

During heavy or prolonged exercise what occurs with respect to the baroreceptors?

They buffer or inhibit increases in pressure. During this time muscle chemoreflexes are active which increase resistance. Baroreceptors operate to buffer the increases and cause active skeletal muscle to vasodilate preventing BP from skyrocketing.

Early in exercise baroreceptors work to _________ BP by ___________

prevent BP from plummeting by vasoconstricting inactive tissues

During heavy/prolonged exercise baroreceptors work to ___________ BP by _________

inhibit/buffer sharp increases in BP by vasodilating at active skeletal muscle tissue

When do muscle chemoreflexes become active?

when there is a mismatch between blood flow and metabolism/ increase in metabolites in tissue.

When a muscle chemoreflex is activated, what occurs?

a signal is sent to the CNS to increase Rp to non active tissues in an effort to raise BP (to clear metabolites from the tissue)

Muscle chemoreflexes are pressure _______ reflexes

raising

What is a muscle chemoreflex?

Thin unmyelinated type III afferents that respond to mechanical and some chemical stimuli as well as unmyelinated type IV afferents responding to the metabolic "milieu".

What composes the exercise pressor reflex (EPR)?

Unmyelinated Type III afferents (mech and chem)
Unmyelinated Type IV afferents (chem)

Humans have hearts that are too_______ relative to our muscle mass

small

Why do we say humans have hearts that are too small?

Because our skeletal muscle ability to vasodilate is greater than our hearts ability to supply it with blood

What happens during severe exercise?

When you cannot increase Q or Rp to inactive tissues
you increase Rp to active tissue to maintain cerebral perfusion pressure

What type of feedback system (+/-) occurs during severe exercise?

Positive
Active muscle becomes vasoconstricted
More metabolites accumulated
More blood pressure needed to clear it out
More metabolites accumulate etc

Where are the cardiopulmonary receptors located?

venatrial junction, inferior and posterior to L ventricle

The L atria is sensitive to changes in ___________. Deformation or stretch of cardiopulmonary receptors causes ______________ and _________

volume
bradycardia and vasodilation

When do the cardiopulmonary receptors become activated?

During recovery when the EPR is less operative
They function to bring Bp down.

The cardiopulmonary receptors are sensitive to ________

Blood volume

During exercise, the cardiopulmonary receptors would normally decrease _________ NS activity to decrease BP if it weren't for _________ overriding them and maintaining BP

sympathetic, EPR

How does the EPR primarily preserve BP?

increase peripheral resistance to non working tissues

Is the EPR still operating during recovery?

Yes just at a much lower level.

What is the effect of NO on sympathetic outflow?

Reduces

Where is NO produced?

Medullary neurons

During high intensity exercise _________ are increased and serve to ____________ neuronal sympathetic activity. Partially by blocking _____________.

ROS
Increase
NO neural outflow to the medulla

Excessive ROS may increase ___________ by _____________ sympathetic outflow and contributing to increased Rp during __________

Exercise induced hypertension (EIHt)
increasing
EIHt