Movement, Muscle, and Biomechanics

Flashcards covering movement types, muscle classification, hierarchies, and the biochemical mechanisms of contraction based on the lecture notes.

What are the three basic types of motion identified in biological systems?

Ameboid, Ciliary, and Muscular

What three activities characterize ameboid locomotion?

Changes in the shape of the cell, the flow of cytoplasm, and pseudopodal activity

On what interaction does the formation of pseudopodia in ameboid movement depend?

The interaction of myosin and actin filaments

How does the beating pattern of a flagellum differ from that of a cilium?

A flagellum beats with a symmetrical undulation, while a cilium beats asymmetrically with a fast stroke and slower recovery motion

How many flagella vs. cilia does a typical cell possess?

A flagellated cell usually has only one flagella, while a ciliated cell can have several thousand cilia

What is the overall efficiency of biological movements in converting chemical energy to mechanical energy?

About $25\%$, with the remaining $75\%$ of energy lost as heat

What are examples of external forces acting on an organism?

Gravity, aerodynamic drag, and the reactionary force of the media

What are examples of internal forces within an organism?

Forces created by muscle contraction and viscous and elastic resistance to material deformation

What is a hierarchical material in biological systems?

A material composed of subunits that form a larger structure, often with mechanical properties exceeding individual components

Which two proteins are involved in the biochemical mechanism for muscle contraction and serve to generate and transmit force?

Actin and myosin

How are muscles broadly classified based on microscopic observation?

Based on the presence or absence of striated bands

Which types of vertebrate muscles are classified as striated?

Skeletal muscles and cardiac muscles

Where is vertebrate smooth muscle typically found?

In the walls of arterioles, the stomach, and the intestines

What describes the structure of striated muscle fibers?

They are large, multinucleated cells formed from the fusion of several cells

In the sliding filament mechanism, what are the thick and thin filaments composed of?

Thick filaments consist of myosin and thin filaments consist of actin

How does the length of filaments change during muscle contraction?

Neither filament changes appreciably in length; they slide past one another to increase overlap

What are two unique functional properties of cardiac muscle?

Contraction spreads rapidly to the entire muscle mass and is immediately followed by a refractory relaxation period

What is the physical appearance and cellular structure of smooth muscle?

Elongated, spindle-shaped cells with a single nucleus that appear homogenous because filaments do not line up regularly

How are tendons defined in relation to muscle and bone?

An extension of the muscle's connective tissue into the connective tissue periosteum surrounding the bone

How are the origin and insertion points of a skeletal muscle defined by convention?

The origin is the proximal end (fixed point) and the insertion is the distal end (moving point)

What biochemical event initiates the formation of cross-bridges between actin and myosin?

An action potential initiated on the membrane of a muscle fiber

What are the four major proteins involved in muscle contraction?

Myosin, actin, tropomyosin, and troponin

What is the role of Calcium ions and ATP in muscle contraction?

Calcium ions trigger binding of actin and myosin, while ATP provides the necessary energy

What is the physical structure of a myosin molecule?

A thin rod with a tail and a globular head

What is meant by the polarity of thin filaments?

They have a barbed end and a pointed end

Where is tropomyosin located in the thin filament?

In the grooves of the actin molecule's double helix

What describes the myosin cycle during contraction?

A cyclic sequence where the head attaches to the thin filament, swivels to pull it past the thick filament, and then releases using $1$ ATP per cycle

How does Calcium ($Ca^{2+}$) enable the actin-myosin interaction?

It binds to troponin, causing a conformational change that moves tropomyosin out of the grooves where it normally blocks interaction

What is the sarcolemma?

The surface membrane of the muscle fiber where electric depolarization spreads during a nerve signal

What is the function of the sarcoplasmic reticulum (SR)?

It pumps out and stores $Ca^{2+}$ to keep concentrations low at rest and releases it to trigger contraction upon an action potential

What is an isotonic contraction?

A muscle contraction that initiates a shortening of the muscle fiber

What is an isometric contraction?

A contraction where tension develops but little to no shortening of the muscle takes place

What occurs during a negative work contraction?

A muscle increases in length as tension occurs

What are the characteristics of tonic (slow) muscle fibers?

They receive multiple nervous inputs, produce slow, sustained contractions, and use graded force based on fibril activation

How does the contraction of twitch (fast) muscles differ from tonic muscles?

They typically have a single nerve input and their action potential results in an all-or-none contraction

What specialized structures connect cardiac muscle cells end-to-end?

Intercalating discs

How does the source of Calcium ions differ between smooth and skeletal muscle?

In smooth muscle, Calcium ions diffuse into the cell from the extracellular matrix rather than being released from the sarcoplasmic reticulum

What are the three sources of ATP for muscle contraction?

Available ATP in the muscle, phosphate transfer from creatine phosphate, and aerobic/anaerobic synthesis

The amount of force a muscle generates is directly proportional to what?

The number of cross-bridges formed during contraction

What two factors determine the number of cross-bridges formed in a muscle?

The amount of overlap between thick and thin filaments and the cross-sectional area of the muscle