Chapter 2: Homeostasis, Bioenergetics, and Skeletal Muscle Physiology

Flashcards covering vocabulary terms from the chapter on Homeostasis, Bioenergetics, and Skeletal Muscle Physiology.

Homeostasis

The cornerstone of physiology; a paradigm for how living systems respond to stresses by holding something the same and preventing change.

Claude Bernard

French physiologist who noted that conditions inside an animal's body were not a simple reflection of the conditions outside, and that living things set up an internal environment more hospitable to their cells.

Walter Cannon

American physiologist who contrived the term “homeostasis” to describe the compensatory processes by which the body functioned to limit variations in the internal environment.

Homeostasis

Compensatory processes by which the body functioned to limit variations in the internal environment.

Homeostatically Regulated Parameters

Body parameters which are actively regulated to maintain a relatively constant internal environment, such as body temperature, blood pressure, blood glucose concentration, and blood gas concentrations.

Set Point

The average value around which a regulated parameter fluctuates; this value isn't fixed and can change depending on ambient conditions or physiological demands.

Sensor

The part of the body that can sense or detect the regulated variable.

Integrator

The part of the body that can interpret information coming from the sensor and send messages out to the effector; this is the brain.

Effector

The part of the body that can affect or change the regulated variable.

Set Point

The conceptual parameter representing the desired value that one wants to maintain.

Threshold

The point at which the integrator sends a message to the effector to make a change.

Error Signal

The deviation between the actual value of a variable and the set point value; this is the negative feedback in the loop.

Stressor

Any condition or process that has the potential to push a controlled variable beyond the acceptable range of values.

Dr. Donald Jackson

Professor Emeritus at Brown University who studied homeostatic processes in animals and discussed the continuum of homeostasis that varies with the animal’s circumstances.

Homeostasis

A dynamic process whereby the value (set point) of a parameter is actively defended against changes.

Steady-State

Means that a parameter is constant over some period of time; this parameter may or may not be homeostatically regulated.

Bioenergetics

How animals use the energy in foods to power the activities of living, in particular, exercise.

Joule (J)

The SI unit for energy.

ATP (Adenosine Triphosphate)

The molecule that serves as the only energy “currency” in the body, used for all energy-requiring processes.

ATP Synthesis

The process by which cells synthesize ATP.

ATP

A molecule with three basic parts: adenine, ribose, and a trio of phosphate groups.

Adenine

One part of the ATP molecule: a molecule made up of carbon, hydrogen and nitrogen atoms.

Ribose

One part of the ATP molecule: A sugar molecule.

Triphosphate

One part of the ATP molecule: A trio of phosphate groups.

ADP (Adenosine Diphosphate)

ATP with only two phosphate groups.

AMP (Adenosine Monophosphate)

ATP with only one phosphate group.

Macronutrients

Fundamental energy sources, including carbohydrate, fat, and protein.

Carbohydrates

Made of carbon, hydrogen, and oxygen atoms; sugars are examples of this.

Monosaccharide

The simplest sugar.

Disaccharide

A sugar consisting of two monosaccharides bonded together.

Polysaccharide

A carbohydrate whose molecules consist of a number of sugar molecules bonded together (3 or more).

Starch

Plants store carbohydrates as this polysaccharide.

Glycogen

Animals store carbohydrates as this polysaccharide.

Fat

Made of carbon and hydrogen atoms; comes in the form of triglycerides and fatty acids.

Fatty Acids

Long chains of carbon and hydrogen.

Triglyceride

The storage form of fat for both plants and animals; linkage of three fatty acids to a single glycerol molecule.

Protein

Different from carbohydrates and fat in that in addition to carbon, hydrogen, and oxygen, it also contains nitrogen.

De-amination

The removal of nitrogen from protein so it can be used as energy.

Creatine Phosphate

Fastest way a muscle cell can produce ATP, by breaking down this molecule.

Glycolysis

Breaking down glucose or glycogen (stored glucose) to make ATP.

Pyruvic Acid

The three-carbon end product of glycolysis.

Lactate Dehydrogenase

An enzyme that catalyzes the conversion of pyruvic acid into lactic acid.

Gluconeogenesis

The process by which the liver can take up lactate and convert it back to glucose.

Aerobic Phosphorylation

The efficient production of ATP that requires oxygen, with the interaction of the Krebs or Citric Acid cycle and the electron transport chain.

Oxidation-Reduction Reactions

The loss and gain of electrons.

Acetyl-CoA

Aerobic generation of ATP from glucose first results in pyruvic acid, then this is removed and coenzyme A is added.

Electron Transport Chain

A series of molecules embedded in the inner mitochondrial membrane to which electrons are transferred, eventually waiting for oxygen.

Beta-oxidation

Process where fatty acids are chopped into two carbon units.

Skeletal Muscle

The muscles found in association with bones and joints.

Central Nervous System (CNS)

System including the brain and spinal cord.

Sensory/Afferent Nerves

These nerves take information TO the CNS.

Motor/Efferent Nerves

These nerves take information FROM the CNS.

Somatic Motor Nerves

Nerves that go to skeletal muscles that you can control by willful thought.

Autonomic Motor Nerves

Nerves that go to the muscles that you can’t control by thought – the cardiac and smooth muscles that function "automatically".

Neuron

A single nerve cell in a nerve.

Motor Unit

One motor neuron plus all of the muscle cells associated with its axon.

Neuromuscular Junction

The place where the motor neuron’s branch and the muscle cell almost meet.

Neuromuscular Cleft/Synapse

The small gap between the end of the axon and the muscle cell membrane.

Neurotransmitter

A substance that sends a message through the synapse to the muscle cell, allowing a neuron to initiate a contraction; an example of one is Acetylcholine.

Acetylcholine (ACH)

The neurotransmitter used by a somatic motor neuron.

Depolarization

Electrical shift inside the cell from negative to positive.

Sarcolemma

The muscle cell membrane.

T-Tubules

Multiple, deep, invaginations found inside the sarcolemma of muscle cells.

Triads

A structural element that holds sarcoplasmic reticulum on two sides and T-tubules.

Sarcoplasmic Reticulum

The smooth endoplasmic reticulum of muscle cells; the storage site of calcium in muscle

Actin and Myosin

The two most fundamental contractile proteins found inside muscle cells.

Actin

A small globular protein that joins end-to-end to form a filament molecule; two intertwine to form the thin filament.

Myosin

Formed from several hundred molecules of myosin and forming the thick filament.

Sarcomere

The functional unit of muscle; from one z-line to the next.

Tropomyosin and Troponin

Two other "leading role" proteins in very close physical association with actin.

Tropomyosin

A ribbon-like protein that runs the length of the actin and blocks the sites where myosin could bind to actin.

Troponin

A protein that can bind calcium.

Excitation-Contraction Coupling

The electrical changes inside the cell leading to force generation by the muscle cell.

Hypertrophy

When muscle cells gets bigger from use.

Atrophy

When muscle cells get smaller with lack of use.

Concentric Contraction

Terms for a muscle action, where the muscle shortens.

Isometric Contraction

Terms for a muscle action, where there is no change in length.

Eccentric Contraction

Terms for a muscle action, where the muscle lengthens.

Isotonic

Meaning that the force of the contraction remains constant.

Isokinetic

Meaning that the speed of rotation (e.g., rotation around the elbow or knee) remains constant.

Speed-Force Trade Off/Force-Velocity Curve

As the speed of contraction gets faster, the maximum force possible gets lower; as contraction becomes slower, the maximum force gets higher.

Length-Tension Curve

For any given cell, there is an optimal length for force production.

Sarcopenia

The term that was invented to describe “clinically” low levels of muscle.