Physiology Lab Exam 7

What is the main function of the digestive system?

To break food into small molecules the body can use to make ATP.

What is the gastrointestinal tract?

Mouth, pharynx, esophagus, stomach, small intestine, and large intestine.

What are the accessory digestive organs?

Teeth, tongue, salivary glands, pancreas, liver, and gallbladder.

What are enzymes?

Biological catalysts that increase reaction rates by lowering activation energy.

What is enzyme specificity?

Enzymes act on specific substrates.

What happens when enzyme temperature rises above its optimal range?

Reaction rate decreases because the enzyme's tertiary structure changes.

How does pH affect enzyme activity?

Each enzyme has an optimal pH range. Activity decreases outside that range.

What does amylase digest?

Starch into maltose and short-chain glucose molecules.

Where is amylase secreted from?

Salivary glands and pancreas.

What is the optimal pH of amylase?

Approximately 6.7 to 7.0.

What does pepsin digest?

Proteins into shorter polypeptides.

Where is pepsin produced?

Chief cells secrete pepsinogen, which is converted into pepsin.

What conditions support pepsin activity?

An acidic environment, with an optimal pH of approximately 1.6 to 2.4.

What does trypsin digest?

Proteins and polypeptides during digestion in the small intestine.

What does lipase digest?

Triglycerides into fatty acids and monoglycerides.

Where is lipase secreted from?

The pancreas.

What is the optimal pH of lipase?

Approximately 8.0.

Where does protein digestion begin?

In the stomach with pepsin and hydrochloric acid.

Where is protein digestion completed?

In the duodenum and jejunum with pancreatic and brush-border enzymes.

What are the final products of protein digestion?

Amino acids, some dipeptides, and tripeptides.

What are the final products of carbohydrate digestion?

Monosaccharides, including glucose, fructose, and galactose.

What are the final products of lipid digestion?

Fatty acids and monoglycerides.

What is the role of the liver in lipid digestion?

It produces bile.

What is the role of the gallbladder?

It stores bile.

What is the role of the pancreas in digestion?

It secretes digestive enzymes, including amylase, lipase, and trypsin, into the small intestine.

What is peristalsis?

Wave-like muscular contractions that move food through the digestive tract.

What is segmentation?

Muscular contractions that mix digestive contents in the intestine.

What is the role of bile in lipid digestion?

It emulsifies large fat droplets into smaller droplets, increasing surface area for enzyme action.

What are micelles?

Structures that carry fatty acids and monoglycerides to intestinal epithelial cells.

What are chylomicrons?

Particles formed in intestinal epithelial cells to transport absorbed lipids.

What is the purpose of the Lugol's test?

To test for starch.

What is the purpose of the Benedict's test?

To test for reducing sugars.

What is metabolism?

All chemical reactions in the body.

What is anabolism?

Building larger molecules from smaller molecules, requiring energy.

What is catabolism?

Breaking larger molecules into smaller molecules, releasing energy.

What is the absorptive state?

The period when nutrients from a meal are being absorbed and processed.

What happens to glucose during the absorptive state?

It can be used to produce ATP or stored as glycogen or converted into other molecules.

What is the role of insulin?

It helps lower blood glucose and promotes glucose uptake and storage.

What triggers insulin secretion?

An increase in blood glucose.

What happens inside a pancreatic beta cell when glucose increases?

ATP production increases, potassium channels close, the cell depolarizes, calcium channels open, and insulin is secreted.

What is GLUT4?

A glucose transporter moved to the cell membrane in response to insulin signaling.

What happens when insulin binds to its receptor?

It activates an intracellular signaling pathway that moves GLUT4 transporters to the membrane.

What is the role of glucagon?

It raises blood glucose by stimulating glycogen breakdown in liver cells.

What happens during glucagon signaling?

Glucagon activates a pathway involving a G protein, adenylyl cyclase, cAMP, and protein kinase A.

How does the body respond when blood glucose is high?

Insulin is released, promoting glucose uptake and storage.

How does the body respond when blood glucose is low?

Glucagon promotes glycogen breakdown and glucose release by the liver.

What is Type 1 diabetes mellitus?

A condition involving insufficient insulin production.

What is Type 2 diabetes mellitus?

A condition involving insulin resistance and potentially insufficient insulin production.

What is a glucose tolerance test used for?

To examine changes in blood glucose after glucose consumption.

Which fuel sources are compared?

Glucose, fatty acids, ketone bodies, and lactic acid.

Which fuel does the brain primarily use?

Glucose, with ketone bodies also listed as a fuel source.

Which fuel source is especially important for resting skeletal muscle?

Fatty acids.

What does a tendon do?

Attaches muscle to bone.

What is a fascicle?

A bundle of muscle fibers.

What are the three connective tissue coverings of skeletal muscle?

Epimysium, perimysium, and endomysium.

What are characteristics of skeletal muscle cells?

They are multinucleated, striated, and surrounded by the sarcolemma.

What are the contractile proteins?

Actin and myosin.

What are the regulatory proteins?

Troponin and tropomyosin.

What is a sarcomere?

The region between two Z discs.

What is the neuromuscular junction?

The synapse between a somatic motor neuron and a skeletal muscle fiber.

What are the three main components of the neuromuscular junction?

Somatic motor neuron, synaptic cleft, and motor end plate.

What is the sliding filament theory?

Muscle contracts as thin and thick filaments slide past one another, shortening sarcomeres.

What happens to the A band during contraction?

Its length remains unchanged.

What happens to the I band during contraction?

It shortens.

What happens to the H zone during contraction?

It shortens or disappears.

What causes myosin to bind to actin?

Calcium binds to troponin C, causing a conformational change that moves tropomyosin away from binding sites.

What happens when ATP binds to myosin?

Myosin detaches from actin.

What happens when ATP is hydrolyzed by myosin?

The myosin head returns to its original orientation.

What causes the power stroke?

Release of inorganic phosphate causes a conformational change in myosin, pulling the thin filament.

What is the role of the sarcoplasmic reticulum?

It stores calcium at rest and releases it when the muscle fiber is stimulated.

Where is most calcium stored in the sarcoplasmic reticulum?

In the terminal cisternae.

What happens to calcium after contraction?

It is actively pumped back into the sarcoplasmic reticulum.

What neurotransmitter is released at the neuromuscular junction?

Acetylcholine.

What happens after acetylcholine is released?

End plate potentials are produced, leading to action potentials in the muscle fiber.

What triggers calcium release from the sarcoplasmic reticulum?

A muscle action potential causes voltage-sensitive channels in the transverse tubules to trigger calcium release.

When is muscle tension greatest according to the length-tension relationship?

When sarcomeres are at their normal resting length.

What happens when sarcomeres are stretched too far?

Muscle tension decreases because fewer actin and myosin interactions occur.

What happens when sarcomeres are too shortened?

Muscle tension decreases.

What are the characteristics of slow oxidative (Type I) fibers?

Small diameter, high fatigue resistance, many capillaries, high myoglobin, high oxidative capacity, and slow twitch rate.

What are the characteristics of fast oxidative-glycolytic (Type IIA) fibers?

Intermediate diameter and fatigue resistance, high oxidative capacity, high glycolytic ability, and faster twitch rate.

What are the characteristics of fast glycolytic (Type IIX) fibers?

Large diameter, high glycogen, few capillaries, low fatigue resistance, low oxidative capacity, high glycolytic ability, and fastest twitch rate.

What is a zymogen?

An inactive enzyme precursor. Pepsinogen is an example.