Ex Phys Exam 1

Homeostasis

Maintenance of a relatively constant, normal internal environment

Steady state

A physiological variable remains constant, but not necessarily at its resting value

Steady state example

Body temperature increases and eventually plateaus

Biological control system

Interconnected components that maintain a desired physiological variable

Biological control system sequence

Stimulus → Sensor → Control center → Effector → Response

Sensor

A receptor that detects changes in a physiological variable

Control center

A structure that receives and processes information from receptors

Effector

An organ or body part that responds to signals from the control center

Negative feedback

A response that reduces or opposes the original stimulus

Gain

A measure of how effectively a control system corrects a disturbance

Larger gain indication

A greater ability to correct disturbances and maintain homeostasis

Intracrine

A chemical messenger acts inside the cell that produces it

Juxtacrine

Signaling occurs between adjacent cells through direct contact

Autocrine

A cell releases a chemical messenger that acts on itself

Paracrine

A cell releases signals that act on nearby cells

Endocrine

Hormones are released into the blood to act on distant tissues

Adaptation

A gradual, long-term adjustment to changes in the environment

Acclimation

Physiological adjustments resulting from repeated environmental stress

Hormesis

A beneficial adaptation caused by exposure to low or moderate levels of stress

Stress proteins

Proteins produced in response to cellular stress

Heat shock proteins

Stress proteins that protect cells and help maintain cellular homeostasis

How exercise causes hormesis

Exercise produces temporary cellular stress that stimulates beneficial adaptations

Bioenergetics

The study of energy transfer and ATP production in living organisms

Metabolism

The sum of all chemical reactions occurring in cells

Anabolic reaction

Reactions that synthesize molecules

Catabolic reaction

Reactions that break down molecules

Endergonic reaction

Chemical reactions that require energy

Exergonic reaction

Chemical reactions that release energy

Coupled reaction

Energy-releasing reactions linked to energy-requiring reactions

Activation energy

The energy required to initiate a chemical reaction

Enzyme function

Lower activation energy and accelerate chemical reactions.

ATP breakdown

ATP → ADP + Pi + Energy

ATP production

ATP is the primary energy source for cellular work.

ATPase

An enzyme that breaks down ATP into ADP and inorganic phosphate

Phosphocreatine (PC)

A compound stored in skeletal muscle that helps regenerate ATP

ATP

Adenosine triphosphate

ADP

Adenosine diphosphate

ATP-PC system

An energy pathway that uses stored ATP and PC for rapid ATP production

ATP-PC system usage

At the beginning of exercise and during short, high-intensity activity

ATP-PC

Rapid ATP production using stored ATP and phosphocreatine (1 ATP)

Stored in muscle

1 ATP (anaerobic)

Stored in blood

1 ATP (anaerobic)

Anaerobic glycolysis

Breaks down glucose without requiring oxygen

Aerobic metabolism

Uses oxygen to produce ATP through mitochondrial pathways

Glycolysis

The breakdown of glucose into pyruvate or lactate, does not require oxygen (4 ATP)

Glycolysis location

Cytoplasm

Glycogen

The stored form of carbohydrate

Glycogenolysis

Breakdown of glycogen into glucose units

Lactate

A three-carbon molecule that can be produced during glucose metabolism

Rate-limiting enzyme of glycolysis

Phosphofructokinase (PFK)

PFK activator

Increased ADP and inorganic phosphate

PFK inhibitor

High ATP concentrations

Aerobic energy production

Glycolysis → Acetyl-CoA → Krebs cycle → Electron transport chain

Acetyl-CoA

A two-carbon molecule that enters the Krebs cycle, needs oxygen

Krebs cycle location

Mitochondrial matrix

Krebs cycle function

Oxidize acetyl-CoA and transfer energy to electron carriers (1 ATP)

Electron transport chain (ETC)

A series of mitochondrial electron carriers involved in oxidative phosphorylation (32 ATP)

Oxidative phosphorylation (OP)

ATP production driven by electron transport and the proton gradient

Oxidation

loss of electrons

Reduction

gain of electrons

NAD⁺

An electron carrier that transfers energy to the electron transport chain

FAD

An electron carrier involved in aerobic metabolism

Beta-oxidation

The breakdown of fatty acids into acetyl-CoA

Approximate resting oxygen consumption

3.5 mL/kg/min or 0.25 L/min for a typical 70-kg adult

ATP at rest

Aerobic metabolism

Approximate resting blood lactate concentration

Less than 1.0 mmol/L

Rest-to-exercise transition

When exercise begins, ATP demand increases immediately, but aerobic ATP production takes time to increase

Rest-to-exercise progression

ATP-PC → Glycolysis → Aerobic metabolism

ATP-PC and anaerobic glycolysis

energy systems initially supplying ATP during exercise

Time for oxygen uptake to reach steady state

Approximately 1–4 minutes during moderate exercise

Oxygen deficit

The difference between oxygen required and oxygen actually consumed at exercise onset

Why oxygen deficit occurs

Aerobic ATP production takes time to match the increased energy demand

Excess post-exercise oxygen consumption (EPOC)

Elevated oxygen consumption during recovery following exercise

Oxygen debt

An older term describing elevated oxygen consumption after exercise

EPOC following high-intensity exercise

Greater due to greater PC depletion, elevated body temperature, and increased recovery demands.

Rapid component of EPOC

Rapid PC resynthesis and restoration of oxygen stores occurs

VO₂max

The maximum rate at which the body can consume oxygen during maximal exercise

Cardiorespiratory fitness

What VO₂max measures

Graded exercise test

A test in which exercise workload increases progressively

VO₂ plateau

Oxygen consumption stops increasing despite an increase in workload

Lactate threshold

The exercise intensity at which blood lactate begins rising systematically above baseline

Anaerobic threshold

An older, related term associated with a rapid increase in blood lactate

Why blood lactate increases during intense exercise

Lactate production increases relative to lactate clearance

Lactate shuttle

Lactate moves between cells and tissues to be used as fuel or converted into glucose

Cori cycle

Lactate travels to the liver and is converted back into glucose

Primary fuels used during exercise

Carbohydrates and fats

Fats during exercise

A greater proportion used more during low-intensity exercise

Carbohydrates

A greater proportion used more during high-intensity exercise

Prolonged moderate exercise fuel

Fat utilization generally increases as carbohydrate availability decreases

Lipolysis

Breakdown of stored triglycerides into fatty acids and glycerol

Lipase

An enzyme that breaks down triglycerides

Free fatty acids

Fatty acids that can circulate in blood and be used for aerobic ATP production

Gluconeogenesis

Production of glucose from non-carbohydrate precursors

Respiratory Exchange Ratio (RER)

The ratio of carbon dioxide produced to oxygen consumed

RER formula

RER = VCO₂ / VO₂

RER of approximately 0.70

Indicates predominantly fat metabolism

RER of approximately 1.00

Indicates predominantly carbohydrate metabolism

RER of approximately 0.85

Indicates a mixture of carbohydrate and fat metabolism

RER as exercise intensity increases

carbohydrate utilization rises.