Insulin & Blood Glucose Regulation, Thyroid Hormone Effects, and Skeletal Muscle Contraction

These flashcards cover key concepts related to insulin and blood glucose regulation, thyroid hormone effects on metabolism, and skeletal muscle contraction.

What organ produces insulin?

Pancreas

When is insulin released?

When blood glucose levels increase

What is the effect of insulin on body cells?

Causes cells (especially skeletal muscle & liver) to take in glucose

What happens to blood glucose after insulin release?

It decreases

What is normoglycemia?

Normal blood glucose level

How does a fish act when normoglycemic?

Regular, smooth swimming

What is hyperglycemia?

Abnormally high blood glucose

How does a fish act when hyperglycemic?

Fast, darting movements

What is hypoglycemia?

Abnormally low blood glucose

How does a fish act when hypoglycemic?

Slow, lethargic, droopy dorsal fin

What is insulin shock?

Hypoglycemia caused by excess insulin

What should a diabetic do if they feel dizzy, shaky, and tired after exercise?

Consume food or drink containing glucose

What regulates body temperature during cold conditions?

Increased metabolic rate and shivering

What is the primary effect of thyroid hormone?

Promotes heat-generating metabolic reactions

What does hypothyroidism cause?

Low body temperature and metabolism

What does PTU (propylthiouracil) do?

Blocks thyroid hormone production

What does a respirometer measure?

Oxygen consumption

Why is oxygen important for metabolism?

Used to produce ATP

What is soda lime used for in a respirometer?

Absorbs carbon dioxide so only oxygen consumption is measured

Why must you normalize oxygen data by weight?

To compare oxygen use accurately between animals of different sizes

What happens if thyroid hormone is blocked?

Body relies on shivering, increasing oxygen use for ATP

What triggers skeletal muscle contraction?

Electrical impulses stimulating motor nerves

What is the threshold stimulus?

The minimum stimulus required for contraction

What happens when you increase stimulus voltage?

Contraction force increases until maximal stimulus is reached

What is the maximal stimulus?

The voltage at which all muscle fibers contract and force can’t increase further

What is the role of the electrode?

Delivers the electrical stimulus to the muscle

What is the role of the transducer?

Measures the force of contraction

Why does 0.2 V produce 0 g of force?

It’s below the threshold stimulus

What does 1.6 V represent when all fibers are contracted?

The maximal stimulus

What ion enters the muscle cell through ACh receptors?

Sodium (Na⁺)

What structure is a T-tubule?

Infolding of the sarcolemma

What is stored in the SR terminal cisterns?

Calcium (Ca²⁺)

What triggers calcium release from the SR?

An action potential traveling down the T-tubule

What happens when calcium binds to troponin?

Tropomyosin moves, exposing myosin binding sites on actin

What is a crossbridge?

Myosin head bound to actin during contraction

What allows myosin to detach from actin?

Binding of a new ATP molecule

What happens if ATP runs out but calcium remains high?

Myosin can’t detach → muscle stays contracted (rigor)

What toxin blocks ACh release at the neuromuscular junction?

Botulinum neurotoxin

What event fails when ACh release is blocked?

Formation of an end-plate potential

What conditions are needed for continuous contraction?

High calcium and available ATP

What happens during the power stroke?

Myosin pulls actin toward the center of the sarcomere

What causes overall muscle shortening?

Shortening of sarcomeres

What system regulates glucose and metabolism (Labs 9–10)?

Endocrine system

What system performs contractions (Labs 11–12)?

Muscular system

What is the link between the two systems?

Hormones like insulin and thyroid hormone regulate the energy muscles need for contraction