Muscle Tissue and Organ Systems – Lecture Review

A comprehensive set of question-and-answer flashcards summarizing key facts about cardiac, smooth, and skeletal muscle tissue, their structure, function, and related anatomy.

Where is cardiac muscle tissue found?

Only in the heart; it forms the bulk of the heart wall.

What two characteristics describe cardiac muscle tissue’s appearance and control?

It is striated and involuntary.

What term describes cardiac muscle’s ability to generate its own electrical impulses?

Autorhythmicity.

How many nuclei does a typical cardiac muscle cell have, and where is it located?

One centrally located nucleus.

What specialized junctions connect neighboring cardiac muscle cells?

Intercalated discs.

Which two junction types are contained in intercalated discs?

Anchoring (desmosomal) junctions and gap junctions.

What is meant by a cardiac "syncytium"?

A group of interconnected cardiac cells that function mechanically and electrically as one unit.

Name the two functional categories of cardiac muscle cells.

Conducting cells and contractile myocytes.

Why does cardiac muscle contraction create a squeezing, wringing motion rather than a pushing action?

Because the continuous sheet of cardiac cells is wrapped around a hollow core like a folded flag during development.

Can cardiac muscle cells regenerate after injury?

No; they lose mitotic capability after about two years of life, so damage reduces contraction and alters conduction rhythm.

Which nervous system controls smooth muscle contraction?

The autonomic nervous system.

Why do smooth muscle cells appear non-striated under a light microscope?

Their myofibrils lack the regular banding pattern seen in skeletal and cardiac muscle.

Describe the metabolic and fatigue characteristics of smooth muscle.

Least metabolic, slow to contract, slow to fatigue, capable of long sustained contractions.

What is the shape of a smooth muscle cell, and where is its nucleus?

Fusiform (spindle-shaped) with one centrally located nucleus.

Which structures transmit tension inside a smooth muscle cell during contraction?

Intermediate filaments attached to dense bodies.

How does a smooth muscle cell look when it contracts?

The middle bulges and the cell appears crinkled.

Where is single-unit (visceral) smooth muscle primarily found?

In walls of hollow viscera such as stomach, intestines, uterus, bladder, and small blood vessels.

How do cells in single-unit smooth muscle communicate to contract together?

Through gap junctions.

Give two locations where multi-unit smooth muscle is found.

Iris of the eye and walls of large arteries or airways (bronchioles).

List three functional differences between smooth and striated muscle.

Smooth muscle contractions start more slowly, last longer, and smooth muscle can stretch and shorten to a greater degree; it also responds to hormones and autonomic nerves.

Name the four key properties of all muscle tissue.

Contractility, excitability, extensibility, and elasticity.

List at least four major functions of muscle tissue.

Motion, movement of substances (blood, food, urine, etc.), maintenance of posture, heat production, support of soft tissues, guarding entrances/exits.

When textbooks say "muscular system," which muscle type are they usually referring to?

The skeletal muscular system.

What two common prefixes indicate muscle tissue in scientific terms?

Myo- and sarco-.

Name six characteristic features used to name skeletal muscles.

Location, size, shape, action, number of origins, and direction of fibers.

Differentiate between a tendon of origin and a tendon of insertion.

Origin attaches to the least-moveable, most proximal bone (may be multiple); insertion attaches to the most-moveable, most distal bone (usually single).

Provide the correct order of skeletal muscle organization from largest to smallest.

Muscle → Fascicle → Muscle fiber → Myofibril → Myofilament → Muscle proteins.

Where are nuclei located in skeletal muscle fibers?

Multiple nuclei positioned at the periphery of the cell.

What is the plasma membrane of a muscle fiber called?

Sarcolemma.

Identify the two primary contractile proteins of myofilaments.

Actin (thin filament) and myosin (thick filament).

Which elastic protein anchors thick filaments to the Z disc?

Titin.

Define a sarcomere.

(smallest)Functional unit of muscle fiber short segment of myofilament(thick&thin), extending from one Z disc to Z disc, responsible for muscle contraction

Note: also includes A& I bands, M lines, H zone(contains a region of thick filaments

Which band of a sarcomere contains only thin filaments?

I band(light), made of Actin.

What is the H zone of a sarcomere?

The central region containing only thick filaments.

Name the structure that stabilizes thick filaments in the center of the sarcomere.

M line(thick), made of myofibril

Briefly describe the sliding-filament mechanism of contraction.

Thin and thick filaments slide past each other, shortening sarcomeres so Z discs move closer and I bands disappear.

What three connective-tissue layers surround and separate parts of a skeletal muscle?

Epimysium, perimysium, and endomysium.

What is an aponeurosis?

A broad, flat sheet-like tendon composed of dense regular connective tissue.

List the three components of a neuromuscular junction.

Axon terminal, synaptic cleft, and motor end plate.

Which sensory receptor detects changes in muscle length (passive stretch)?

Muscle spindle.

Which receptor monitors tension produced in a tendon during muscle contraction?

Golgi tendon organ.

Describe slow oxidative muscle fibers.

Red fibers that contract slowly, rely on aerobic metabolism, and resist fatigue; common in postural muscles.

Which skeletal muscle fiber type is white and fatigues quickly?

Fast glycolytic fibers.

Describe motor unit

• one motor neuron & all the muscle fibers it serves

  • Large (gross control)

  • Small (fine control)

Neuromuscular Junction

Site where neuron interfaces with sarcolemma of muscle fiber(consist of axon terminal, synaptic cleft, motor end plate)

Motor end plate =

the modified region of sarcolemma (plasma mbn) immediately under the motor axon terminal ACH is released, AP is initiated on muscle side of synapse, initiates muscle contraction

Rotator Cuff group incudes

(SITS) Supraspinatus, infraspinatus, teres minor, subscapularis

quadriceps group includes:

rectus femoris, vastus lateralis, vastus medialis, vastus intermedius

hamstrings group includes:

biceps femoris, semitendinosus, semimembranosus

Lever class is

a categorization of levers based on the position of the fulcrum, effort, and lever. There are three classes: first class, second class, and third class, each affecting mechanical advantage differently.

What’s a lever?

Rigid bar that moves on fixed point

allows movement of heavier loads or greater range of movement

What’s a fulcrum?

The fixed point around which a lever pivots, enabling movement and force application.

What does the effort part mean?

Achieves movement; resistant opposes movement

First class lever( EFR)

can favor speed/ range of movement (ROM) or strenth

Second class lever( FRE)

Favors strength

Third class lever(FER)

(mobility) allows greater speed& ROM (muscle shortens

Small # of long fibers =

Great ROM

Large # of short fibers=

Great Strength

Parallel=

Greatest degree of shortening

pennate=

greatest strength

Convergent=

Strenggth, variable ROM

Circular=

Close of an opening

Rigor mortis means

after death there is no ATP generation needed to detach cross bridges last 24 hours, then tissues start to degenerate

Regeneration means

skeletal muscle cells cant divide , there are satellite cells(dormant cells) which can divide & add new fibers mostly repair is by fibrosis, replacement of muscle tissue w/ fibrous scar tissue