Physiology Exam 2

Criteria for VO2 max achievement

-oxygen consumption stops rising

-age predicted max HR is reached

-Respiratory Exchange Ratio (VCO2/VO2) is greater than 1.15

-Blood lactate is greater than 8mmol/L

Genetic influence on VO2 max

-20-30% is hereditary

-if you are less fit to start, that means you can increase your VO2 max more (min 20%)

Gender influence on VO2 max

-Males have 15-30% higher VO2 max than Females

Age influence on VO2 max

Sedentary- decreases by 10% per decade (post age 30)

Athletes- decreases by 5% per decade (post age 30)

Metabolic Adaptations to Aerobic Exercise Training

-lower % of VO2 max at same speed

-better O2 delivery from CV

-increase in capillary number meaning more O2 transport

-increased glycolysis capacity and stored glycogen

-less accumulation of lactic acid

-size and number of mitochondria increase

-fat storage in muscle and fat utilization

Lactate Threshold

-the exercise intensity at which blood lactate accumulates faster than it can be removed

-requires high sustainable exercise intensity (competition level)

-corresponds to hyperventilation

-usually occurs at 50-65% VO2 max in untrained people

-indicates an increased reliance on carbohydrate utilization via glycolysis

Respiratory Exchange Ratio

-ratio of CO2 produced to O2 consumed

(pure CHO RER=1.0

pure fat RER=0.70

at rest, RER=0.80)

Heart Rate and Training

Resting HR and Submax HR decrease with training but Max HR only changes with age

With training

submax VO2 stays the same, max VO2 increase, submax lactate decreases, and muscle glycogen utilization is decreased

Function of Ventilatory System

move air in and out of the lungs to facilitate gas exchange (O2 to blood and CO2 out)

The Lung

-capacity of 4 to 6 liters based on height

-contain more than 300 alveoli

Conducting Zone (anatomic dead space)

-air transport, warming, humidification, filtration

Respiratory Zone

location of gas exchange

Alveoli

-largest blood supply of any organ

-million of short, thin walled capillaries lying next to alveoli which permit diffusion of O2/CO2

Ventilation

air enters trachea, air down to bronchi, bronchi branch into bronchioles, and the air is conducted into the alveoli

Inspiration

-diaphragm contracts and lowers

-volume of thoracic cage increases

-thoracic pressure becomes 5mmHg less than atmospheric pressure

-air enters lung

Expiration

-diaphragm relaxes and rises

-volume of thoracic cage decreases

-thoracic pressure becomes greater than atmospheric pressure

-air exits lung

Tidal Volume

normal inspiration and expiration

Inspiratory Reserve Volume

inspiration above tidal volume

Expiratory reserve volume

expiration above tidal volume

Forced Vital Capacity

tidal volume+inspiratory reserve volume+expiratory reserve volume

Residual Lung Volume

air remaining in lungs after Expiratory Reserve Volume

Total Lung Capacity

tidal volume+inspiratory reserve volume+expiratory reserve volume+residual volume

Lung Volume

-determined by height/weight and genetics (small=3-4L, large=6-7L)

-training and exercise capacity are not related to lung volume

Alveolar Ventilation

-influenced by a slow deep breaths

Two factors that influence gas exchange in the Lungs

1. Pressure Gradient-O2 diffuses into blood from alveoli and CO2 into alveoli from blood (High to Low)

2. Solubility-ability to dissolve in solution (CO2 is 25x’s more soluble than O2)

Right Shift of oxyhemoglobin dissociation

-caused by increased temperature, low pH, increased CO2, and higher 2, 3 DPG levels

-hemoglobin needs less O2, leading to lower O2 saturation, and increased O2 release to working muscles (greater oxygen availability)

2, 3 DPG

-a compound produced in RBC during glycolysis

-binds loosely to Hb to decrease the affinity of binding of O2 to Hb

-promotes the release of O2 to tissues

-reduces the effects of CVD and altitude exposure

Blood Doping and Erythropoetin (EPO)

-adding RBC’s to circulation prior to exercise, enhancing the blood’s capacity to transport oxygen to the muscles (higher performance for longer)

-basically taking blood out of the body and storing it until it needs to be reinfused for competition

-fully illegal and can be at risk for bloodborne diseases and infection

Hemoglobin

carries oxygen from lungs to body tissues and removes carbon dioxide to bring back to the lungs for exhalation

Myoglobin

-found in cardiac and skeletal muscle

-carries oxygen and helps oxygen transfer to mitochondria during exercise

Carbon Dioxide

the most important regulator of respiration

Non metabolic CO2

-causes an increase in carbon dioxide which is not produced by aerobic metabolism during high intensity exercise due to buffering blood lactate

-this increase in CO2 output causes a sharp rise in breathing rate to expel the excess

Ventilatory Threshold

-The point during increased exercise intensity where ventilation (breathing) rises exponentially relative to oxygen uptake (VO2)

-deflection of VT curve is increased ventilation, increased blood lactate, and increased CO2

-VT is less invasive than LT (blood based)

Valsalva Meaneuver (exhaling against a closed airway)

-increase in intrathoracic pressure initially

-then decrease in peripheral blood pressure

-decrease in stroke volume (amount of blood the left ventricle pushes out into the aorta per beat)

(decreased return of blood to the heart and brain)→dizziness or fainting

Function of CV system

-deliver O2 to active tissue

-oxygenate blood returned to the lungs

-transport heat from core to skin

-deliver nutrients to tissues

-transport hormones to tissues

Heart chambers

Right Atria- receiving station from body

Right Ventricle- sends blood to lungs

Left Atria- receiving station from lungs

Left Ventricle- sends blood to the body (most important)

Tricuspid Valve of the Heart

controls flow of blood between Right Atria and Right Ventricle

Mitral/ Bicuspid Valve of the Heart

controls flow of blood between Left Atria and Left Ventricle

Arterial System (vasoconstriction/dilation)

Aorta→Arteries→Arterioles→Capillaries

-transports oxygenated blood away from the heart through high pressure thick walled vessels

Venous System

Capillaries→Venules→Veins→Inferior and Superior Vena Cava

-returns deoxygenated blood to the heart using low pressured, thin walled vessels with valves to prevent backflow

Systolic Blood Pressure

pressure when the heart contracts (120mmHg)

Diastolic Blood Pressure

pressure when the heart relaxes (80mmHg)

Mean Arterial Pressure (MAP)

average force of blood against arterial walls during cardiac cycle

=DBP+[0.3(SBP-DBP)]

Cardiac Output

-total volume of blood pumped by the heart per minute (L/min)

CO=HR x SV

Hypertension

high blood pressure usually a result of high total peripheral resistance (stress, high cholesterol, vasoconstriction)

(SBP>140 and DBP>90)

Electrical Conduction in Heart

-heart has inherent/essential rhythm of 100bpm

-rhythm provided by SA node(pacemaker)→depolarize atria

-signal sent to AV node→AV bundle/Bundle of His→purkinje fibers→depolarize ventricle

Automaticity

the ability of specialized cardiac cells to spontaneously depolarize, reach a threshold potential, and generate an action potential without requiring an external neural influence (sympathetic/parasympathetic)

Syncytium

a network of cells that are interconnected so closely that they function as one single, synchronized unit. Meaning that when one cell is excited, the action potential spreads rapidly to all connected cells

Myocardial Infarction (heart attack)

occurs when a coronary artery is blocked typically by plaque rupture and blood clot, cutting off oxygen to the heart muscle and causing tissue death

(Left side MI’s are more severe than right because it affects LV)

During Exercise

TPR decreases, SBP increases, DBP remains the same, Stroke Volume increases, Arteriovenous oxygen difference increases, and cardiac output increases

Oxygen delivery to myocardium and skeletal muscle

increases during exercise due to vasodilation

The Fick Equation tells you that VO2 is influenced by

-the delivery of oxygenated blood to tissues

-the muscles’ ability to extract the oxygen

VO2=CO x a-vO2 difference

Arteriovenous Oxygen Difference (a-VO2)

the difference between oxygen in arterial blood and venous blood, which represents the oxygen extraction by tissues

Endurance Training influence

-decreases resting HR, increases stroke volume, and cardiac outputs stays the same at rest but will double at max exercise

Resting HR- increased parasympathetic

Stroke Volume-hypertrophy and increased venous return

Physiological Cardiac Hypertrophy

“athletes heart” or a health, reversible, and adaptive response to increased workload

Pathological Cardiac Hypertrophy

harmful response to chronic stress/hypertension, often leading to heart failure (thickened muscle with reduced chamber size)