Physiology Week 2: Muscle Function and Structure

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What is the resting potential of a nerve fiber in millivolts?

-50mV

-55mV

-70mV (correct)

-60mV

What is the primary reason for the diffusion of potassium ions out of the cell?

The leak channels in the nerve cell membrane

The high concentration of potassium ions in the extracellular fluid

The operation of the membrane pump

The negative charge of the proteins inside the cell (correct)

During the depolarization state, what ions are allowed to flow into the cell?

Potassium ions only

Sodium ions only (correct)

Chloride ions only

Sodium and potassium ions

What is the main function of the voltage-gated potassium channels during the repolarization state?

To open slowly to allow potassium ions to flow out of the cell Signup and view all the answers

What is the term for the diffusion potential level across a membrane that exactly opposes the membrane becoming positively charged?

Nernst potential Signup and view all the answers

What is the primary reason for the hyperpolarization state?

The slow closure of potassium channels Signup and view all the answers

What is the absolute refractory period?

The time needed for sodium channels to revert from inactivated to resting Signup and view all the answers

What is the consequence of the differential permeability of the membrane to ions?

Ionic differences Signup and view all the answers

What is the primary reason for the high concentration of potassium ions in the cytosol?

The operation of the membrane pump Signup and view all the answers

What is the primary function of the Na-K Pump in nerve cells?

To transport 3 Na+ out and 2 K+ in Signup and view all the answers

What type of ion channels are opened during the local depolarization of the muscle fiber membrane?

Nicotinic receptors Signup and view all the answers

What is the primary function of acetylcholinesterase in the neuromuscular junction?

To remove acetylcholine from the synaptic cleft Signup and view all the answers

What is the term for the rapid removal of acetylcholine from the synaptic cleft?

Hydrolysis Signup and view all the answers

What is the term for the process by which an action potential in a motor neuron triggers muscle contraction?

Excitation-contraction coupling Signup and view all the answers

What is the primary cause of Myasthenia Gravis?

Abnormal reduction in acetylcholine receptors Signup and view all the answers

What is the primary function of the active zone in the presynaptic terminal?

To hold synaptic vesicles in place Signup and view all the answers

What type of channels are opened in the muscle fiber membrane during the local depolarization?

Ligand-gated ion channels Signup and view all the answers

What is the primary function of the SNARE proteins in the synaptic vesicles?

To hold synaptic vesicles in place Signup and view all the answers

Which of the following muscle properties is responsible for the ability to return to its original shape after being stretched?

Elasticity Signup and view all the answers

What is the function of the T-tubules in skeletal muscle fibers?

To allow plasma membrane of muscle fiber to carry depolarization of action potential to interior of the fiber Signup and view all the answers

What is the primary function of myoglobin in skeletal muscles?

To serve as a local oxygen reservoir that can temporarily provide oxygen Signup and view all the answers

What is the primary function of the RYR channel in the sarcoplasmic reticulum?

To release a pulse of Ca2+ into the cytosol Signup and view all the answers

What is the effect of Ca2+ binding to troponin?

It causes the tropomyosin to move away from the myosin-binding sites Signup and view all the answers

What is the term for the ability of a muscle to be stimulated by a motor nerve?

Excitability Signup and view all the answers

What is the type of muscle fiber that is rich in mitochondria and relies on oxidative metabolism?

Type 1 (Red Fibers) Signup and view all the answers

What is the significance of the transverse tubules (T-tubules) in muscle contraction?

They help to propagate action potentials to the interior of the cell Signup and view all the answers

What is the role of Na+ channels in the generation of an action potential?

They generate and propagate action potentials Signup and view all the answers

What is the term for the potential difference generated across a membrane when a charged solute (ion) diffuses down its concentration gradient?

Diffusion potential Signup and view all the answers

What is the role of the sarcoplasmic reticulum in skeletal muscle fibers?

To regulate calcium storage and release Signup and view all the answers

What is the result of the binding of ATP to the myosin head?

The myosin head becomes 'cocked' and ready to bind to the actin filament Signup and view all the answers

What is the function of the DHPR in the neuromuscular junction?

To sense membrane depolarization and open the RYR channel Signup and view all the answers

What is the term for the bundle or cluster of muscle fibers that are surrounded by perimysium?

Fascicle Signup and view all the answers

What is the effect of the myosin head bending towards the center of the sarcomeres?

It causes the actin filaments to slide towards the M-line Signup and view all the answers

What is the term for the thin membrane that encloses a skeletal muscle cell?

Sarcolemma Signup and view all the answers

What is the role of the voltage-gated K+ channels in the repolarization of the sarcolemma?

They help to restore the sarcolemma to its initial polarized state Signup and view all the answers

What is the result of the action potential propagating down the T-tubules?

The RYR channel opens briefly Signup and view all the answers

What is the primary function of the Ca 2+ active transport pump?

To remove Ca 2+ ions from the myofibrillar fluid after contraction Signup and view all the answers

What is the term for a single contraction and relaxation cycle produced by an action potential within a muscle fiber?

Twitch Signup and view all the answers

What is the primary source of energy for muscle contraction, accounting for 95% of energy used?

Oxidative Metabolism Signup and view all the answers

What is the term for the phenomenon where successive muscle contractions fuse together at a critical frequency, resulting in a smooth and continuous contraction?

Tetanus Signup and view all the answers

What is the term for the relationship between muscle length and contraction strength?

Length-tension relationship Signup and view all the answers

What is the primary role of creatine phosphokinase in muscle contraction?

To phosphorylate creatine to produce phosphocreatine Signup and view all the answers

What is the term for the decrease in muscle contraction strength that occurs when the muscle is shortened or stretched?