AnaPhy (Lecture): Chapter 11 - Muscle Tissue and Chapter 12 - The Muscular System

Comprehensive practice flashcards covering muscle tissue histology, sarcomere structure, excitation-contraction coupling, energy metabolism, muscle mechanics, and muscular anatomy from Dr. Madriaga's AnaPhy lectures.

What are the five primary functions of muscle tissue?

Movement (body and internal materials), posture maintenance, stabilization of joints, protection of internal organs, and temperature regulation.

What are the four primary characteristics of muscle tissue?

Excitability (responding to changes in electrical potentials), extensibility (ability to stretch), elasticity (ability to stretch and recoil to original shape), and contractility (ability to pull on an attachment site and shorten).

How do the three types of muscle tissue differ in cell shape, striations, and nucleus count?

Skeletal muscle consists of long, cylindrical, multinucleated, striated cells. Cardiac muscle consists of shorter, branching, striated cells with one or two nuclei. Smooth muscle consists of non-striated, spindle-shaped cells (football-like) with a single nucleus.

What are the three connective tissue coverings of skeletal muscle and what structures do they surround?

Epimysium surrounds the entire muscle; perimysium surrounds fascicles (bundles of muscle cells); endomysium surrounds individual muscle cells.

What is the meaning of the Greek prefix 'sarco-' commonly found in muscle cell terminology?

Flesh.

What are the functions of the sarcoplasmic reticulum (SR) and T-tubules in a skeletal muscle cell?

The sarcoplasmic reticulum is an endoplasmic reticulum that stores calcium ions. Transverse tubules (T-tubules) are extensions of the sarcolemma that conduct electrical action potentials deep into the cell.

What is a sarcomere and how is its boundary defined?

A sarcomere is the contractile unit of skeletal muscle composed of myofilaments; it spans from one Z disc to the next Z disc.

What proteins compose the thick and thin filaments of a sarcomere?

Thick filaments are composed of myosin. Thin filaments are composed of actin along with the regulatory proteins troponin and tropomyosin.

What do the A band, I band, H zone, and M line represent in a sarcomere?

The A band spans the full length of the thick filaments; the I band contains only thin filaments; the H zone contains only thick filaments; the M line is the horizontal line in the center of the sarcomere.

What neurotransmitter is released at the neuromuscular junction (NMJ) to stimulate skeletal muscle contraction?

Acetylcholine (ACh).

What are the values of the resting membrane potential and the depolarized potential during an action potential in a skeletal muscle fiber?

The resting membrane potential is $-90\,\text{mV}$, and it reaches $+30\,\text{mV}$ upon depolarization when sodium ions ($\text{Na}^+$) enter the cell.

According to the sliding filament model, how do calcium ions initiate cross-bridge formation?

Calcium released from the sarcoplasmic reticulum binds to troponin, causing a conformational change that moves tropomyosin away from the myosin-binding sites on actin, allowing myosin heads to bind.

What occurs to the bands and zones of the sarcomere during muscle contraction?

The length of the myofilaments remains unchanged, but overlap increases, causing the I band and H zone to narrow or disappear while Z discs move closer together.

Why does rigor mortis occur after death in skeletal muscle?

A lack of ATP prevents the detachment of myosin heads from actin filaments, causing cross-bridges to remain locked in place.

What enzyme is responsible for breaking down acetylcholine in the synaptic cleft during muscle relaxation?

Acetylcholinesterase.

How long does creatine phosphate supply energy for muscle contraction, and how does it regenerate ATP?

It supplies energy for approximately $15\,\text{seconds}$ by directly donating its phosphate group to ADP.

What is the duration and end-product pathway of glycolysis during muscle activity in the absence of oxygen?

Glycolysis powers muscle activity for approximately $1\,\text{minute}$; without oxygen, pyruvate is converted into lactic acid (which is subsequently broken down by the liver).

How much ATP is generated by aerobic cellular respiration per pyruvate molecule breakdown in muscle mitochondria?

Approximately $36\,\text{ATP}$.

What are the key physiological characteristics of Slow Oxidative (SO) muscle fibers?

They contract slowly, generate the weakest contractile strength, rely on aerobic respiration, appear red due to rich myoglobin content, and are slow to fatigue (ideal for maintaining posture and joint stability).

What are the key physiological characteristics of Fast Glycolytic (FG) muscle fibers?

They contract rapidly, produce the strongest contractions, rely primarily on glycolysis, store abundant glycogen, and fatigue quickly (adapted for rapid, powerful movements).

How do concentric and eccentric isotonic contractions differ from isometric contractions?

In concentric isotonic contraction, the muscle shortens while moving a load; in eccentric isotonic contraction, the muscle lengthens while moving a load; in isometric contraction, muscle tension increases without moving a load or changing length.

What are the three phases displayed on a myogram of a muscle twitch?

The latent period, contraction phase, and relaxation phase.

What is a motor unit?

A motor neuron and all the specific skeletal muscle fibers of a single type that it innervates and controls simultaneously.

What two specialized cell junctions are located within the intercalated discs of cardiac muscle?

Desmosomes (which firmly hold adjacent cells together mechanically) and gap junctions (which allow action potentials to spread rapidly between cells).

How does excitation and cross-bridge activation occur in smooth muscle without troponin?

Calcium from the sarcoplasmic reticulum and extracellular fluid binds to calmodulin, which activates myosin kinase; active myosin heads then bind actin filaments anchored to dense bodies, creating a corkscrew contraction.

What are varicosities in smooth muscle tissue?

Bulbous swellings along autonomic motor neurons that store and release neurotransmitters across smooth muscle cells.

In skeletal muscle attachments, how are the origin and insertion differentiated?

The origin is the attachment point that remains stationary/does not move during contraction, whereas the insertion is the attachment point that moves.

What roles do agonists, antagonists, synergists, and fixators play in muscle actions?

An agonist (prime mover) is primarily responsible for an action; an antagonist opposes that movement; a synergist aids the prime mover; a fixator stabilizes a bone or attachment point.

What are the three main types of pennate fascicle arrangements?

Unipennate (fascicles on one side of the tendon), bipennate (fascicles on both sides of the tendon), and multipennate (fascicles branching to resemble multiple feathers arranged together).

What are the etymological meanings of the components in the name 'Biceps brachii'?

'Bi' is Latin for two; 'ceps' is derived from Latin for head; 'brachii' refers to the brachium (arm) region.

What cranial nerve innervates the major muscles of facial expression, such as the orbicularis oculi, orbicularis oris, and buccinator?

Cranial nerve VII (facial nerve).

Which cranial nerves provide motor innervation to the six extraocular muscles?

Cranial nerve III innervates the medial rectus, superior rectus, inferior rectus, and inferior oblique; cranial nerve IV innervates the superior oblique; cranial nerve VI innervates the lateral rectus.

Which cranial nerves supply the extrinsic muscles of the tongue (genioglossus, styloglossus, hyoglossus, and palatoglossus)?

Genioglossus, styloglossus, and hyoglossus are innervated by the hypoglossal nerve (cranial nerve XII); palatoglossus is innervated by cranial nerve X (vagus nerve).

What three columns of muscles constitute the Erector Spinae group?

Iliocostalis, longissimus, and spinalis.

What are the four muscles of the anterior abdominal wall from superficial to deep?

Rectus abdominis, external abdominal oblique, internal abdominal oblique, and transversus abdominis.

What nerve provides motor innervation to the diaphragm, and what causes hiccups?

The phrenic nerve; hiccups are caused by sudden spasmodic contractions of the diaphragm.

Which four muscles form the rotator cuff at the shoulder joint?

Subscapularis, supraspinatus, infraspinatus, and teres minor.

Which muscles are responsible for flexion and extension of the forearm at the elbow?

Flexion is produced by the biceps brachii, brachialis, and brachioradialis. Extension is produced by the triceps brachii and anconeus.

What are the four muscles comprising the quadriceps femoris group, and what is their collective insertion?

Rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius; they insert onto the tibia via the quadriceps tendon.

Which three muscles compose the hamstring group in the posterior thigh compartment?

Biceps femoris, semitendinosus, and semimembranosus.

Which superficial posterior leg muscles insert onto the calcaneus via the calcaneal tendon?

Gastrocnemius and soleus (as well as plantaris).