LOCOMOTION AND MOVEMENT

Primary cellular mechanism driving protoplasmic streaming in Amoeba

Flow of cytoplasm mediated by pseudopodia and cytoskeletal microfilaments.

Dual physiological functions performed by cilia in Paramecium

Locomotion through the aquatic medium and propulsion of food particles through the cytopharynx.

Dual functions served by tentacles in Hydra

Capturing prey and facilitating locomotion.

Fundamental rule governing the relationship between movement and locomotion

All locomotions are movements, but all movements are not locomotions.

Specialized human blood cells capable of amoeboid movement

Macrophages and leucocytes.

Cytoskeletal elements directly involved in driving amoeboid movement

Microfilaments composed of actin.

Two anatomical locations in the human body lined by ciliated epithelium that perform ciliary movement

Respiratory tract (trachea) for clearing inhaled dust particles, and the female reproductive tract (fallopian tubes) for passage of ova.

Three biological systems exhibiting flagellar movement

Swimming of spermatozoa, maintenance of water currents in sponge canal systems, and locomotion in Protists like Euglena.

Three organ systems whose coordinated activity is indispensable for locomotion

Muscular, skeletal, and neural systems.

Embryonic germ layer of origin for muscular tissue

Mesoderm.

Percentage of total body weight contributed by muscular tissue in an adult human

$40\text{--}50\%$.

Total number of muscles in an adult human and their distribution

$639$ muscles in total, comprising $317$ paired muscles and $5$ unpaired muscles.

Four cardinal physiological properties of muscle tissue

Excitability, contractility, extensibility, and elasticity.

Functional property shared by both muscle cells and nerve cells

Excitability.

Mechanism responsible for muscular enlargement during life

Hypertrophy (increase in muscle fibre size), as hyperplasia (increase in cell number) is absent post-embryonic development.

Histological, structural, and regulatory properties of skeletal muscle fibres

Striated, voluntary, cylindrical, unbranched, and multinucleated (syncytium) with peripheral nuclei.

Histological, structural, and regulatory properties of visceral (smooth) muscle fibres

Non-striated, involuntary, spindle-shaped (fusiform), unbranched, and uninucleated with a central nucleus.

Histological, structural, and regulatory properties of cardiac muscle fibres

Striated, involuntary, cylindrical, branched, uninucleated with a central nucleus, and fatigue-resistant.

Specialized cell junctions in cardiac tissue that enable synchronized contraction

Intercalated discs equipped with gap junctions.

Relative contraction speed ranking among the three muscle types

Cardiac is fastest, skeletal is fast, and visceral (smooth) is slowest.

Vascular supply comparison among skeletal, smooth, and cardiac muscles

Cardiac has abundant blood vessels, skeletal has rich blood vessels, and smooth has less blood vessels.

Common collagenous connective tissue layer holding multiple muscle bundles or fascicles together

Fascia.

Connective tissue sheath enclosing an entire individual muscle organ

Epimysium.

Connective tissue sheath surrounding an individual muscle fascicle

Perimysium.

Delicate connective tissue sheath investing a single muscle fibre

Endomysium.

Plasma membrane lining an individual muscle fibre

Sarcolemma.

Cytoplasm of a muscle fibre and its primary storage molecules

Sarcoplasm, containing glycogen granules and myoglobin.

Organelle serving as the primary intracellular reservoir for calcium ions in muscle fibres

Sarcoplasmic reticulum.

Parallel protein filaments arranged longitudinally within muscle sarcoplasm

Myofilaments or myofibrils.

Protein constituting the dark, anisotropic band in myofibrils

Myosin (forming the A-band).

Protein constituting the light, isotropic band in myofibrils

Actin (forming the I-band).

Optical property of the light band under polarized light

Mono-refractive (isotropic).

Elastic fibrous membrane that bisects each I-band and anchors thin filaments

$Z$-line (Krause membrane).

Thin fibrous membrane running through the middle of the A-band that holds thick filaments together

$M$-line.

Central zone of thick filaments not overlapped by thin filaments in a resting state

$H$-zone (Hensen zone).

Functional and structural unit of muscle contraction

Sarcomere, spanning the region between two successive $Z$-lines.

Band composition formula representing a single relaxed sarcomere

$\frac{1}{2}\text{ I-band} + 1\text{ A-band} + \frac{1}{2}\text{ I-band}$.

Structural composition of the thin (actin) filament

Two filamentous 'F'-actins helically wound together, along with two strands of tropomyosin and periodically spaced troponin complexes.

Monomeric building block of F-actin

Globular actin ('G'-actin), which polymerizes in the presence of $Mg^{2+}$.

Fibrous regulatory protein running close to F-actin throughout its length to mask myosin-binding sites at rest

Tropomyosin.

Three functional subunits composing the troponin complex

$TpT$ (binds tropomyosin), $TpI$ (inhibits actin-myosin interaction by masking active sites), and $TpC$ (binds calcium ions).

Monomeric protein subunit constituting thick myosin filaments

Meromyosin, with approximately $300$ monomers assembling into one thick filament.

Structural components constituting Heavy Meromyosin (HMM)

Globular head and short arm, which together project outward as the cross-arm.

Structural component constituting Light Meromyosin (LMM)

The straight fibrous tail portion of the meromyosin monomer.

Two specific binding sites located on the globular head of meromyosin

Actin-binding site and ATP-binding site.

Enzymatic catalytic capability located within the globular head of meromyosin

ATPase enzyme activity.

Biologists who formulated the Sliding Filament Theory

A. Huxley and H. Huxley.

Central premise of the Sliding Filament Theory

Contraction of a muscle fibre takes place by the sliding of thin filaments over thick filaments without shortening of individual filaments.

Components of a single physiological motor unit

A single motor neuron along with all the muscle fibres it innervates.

Junction between a somatic motor neuron axon terminal and the muscle sarcolemma

Neuromuscular junction or motor end-plate.

Neurotransmitter discharged into the synaptic cleft at the motor end-plate

Acetylcholine (ACh).

Membrane channel opened by acetylcholine binding on the sarcolemma

Ligand-gated sodium ($Na^+$) channels, inducing depolarization.

Tubular invaginations of the sarcolemma that conduct action potentials deep into the sarcoplasm

T-tubules (transverse tubules).

Immediate trigger for the unmasking of active sites on actin filaments

Binding of calcium ($Ca^{2+}$) to the $TpC$ subunit of troponin.

Molecular bond established when energized myosin binds to exposed actin sites

Actin-myosin cross-bridge.

Mechanical event wherein the myosin head tilts and pulls actin towards the centre of the A-band

Power stroke.

Dimensional change in the A-band during full muscle contraction

The $A$-band retains its original length and does not shorten.

Dimensional changes in the I-band and H-zone during muscle contraction

The $I$-band reduces in width and the $H$-zone shortens or completely disappears.

Movement of Z-lines during sarcomere shortening

Successive $Z$-lines are pulled inwards towards each other.

Molecular event responsible for detaching the myosin head from actin to break the cross-bridge

Binding of a new ATP molecule to the myosin head.

Products released from the myosin head during the execution of the power stroke

$\text{ADP}$ and inorganic phosphate ($\text{P}_i$).

Active transport mechanism essential for restoring the muscle fibre to its relaxed state

Active pumping of $Ca^{2+}$ from the sarcoplasm back into the sarcoplasmic reticulum cisternae via $Ca^{2+}$ ATPase pumps.

Enzymatic degradation terminating acetylcholine action at the motor end-plate

Cleavage into acetate and choline by acetylcholinesterase.

Immediate biochemical source of energy consumed during muscle contraction cycles

Adenosine triphosphate ($\text{ATP}$).

Number of ATP molecules hydrolyzed per individual cross-bridge interaction cycle

$1$ molecule of $\text{ATP}$.

Metabolic consequence of repeated muscle contraction leading to fatigue

Anaerobic breakdown of glycogen leading to the accumulation of lactic acid.

Chemical cause of post-mortem rigor mortis

Depletion of cellular $\text{ATP}$, preventing the detachment of myosin heads from actin and locking muscles in contracture.

Red, iron-containing, oxygen-storing pigment present in muscle sarcoplasm

Myoglobin.

Biochemical and physiological features of Red muscle fibres

High myoglobin, abundant mitochondria, dense capillary beds, low sarcoplasmic reticulum, smaller diameter, and aerobic sustained contractions resistant to fatigue.

Biochemical and physiological features of White muscle fibres

Low myoglobin, few mitochondria, sparse capillary beds, abundant sarcoplasmic reticulum, larger diameter, and fast anaerobic twitches that fatigue quickly.

Anatomical example of muscles rich in red fibres in humans

Extensor muscles of the back (postural muscles).

Anatomical example of muscles predominantly composed of white fibres in humans

Eyeball muscles.

Chemical difference distinguishing bone matrix from cartilage matrix

Bone matrix is hard and non-pliable due to calcium salts, whereas cartilage matrix is slightly pliable due to chondroitin salts.

Total bone count in a normal adult human skeleton versus a newborn

$206$ bones in an adult versus approximately $305\text{--}306$ bones in a newborn.

Scientific study of bone structure and skeletal system disorders

Osteology (or skeletology).

Scientific study of muscular structure, function, and pathology

Myology (or sarcology).

Total number of bones comprising the adult axial skeleton

$80$ bones.

Four skeletal regions constituting the axial skeleton

Skull, vertebral column, ribs, and sternum.

Total number of bones comprising the appendicular skeleton

$126$ bones.

Skeletal components constituting the appendicular skeleton

Bones of the limbs ($120$) and their supporting girdles ($6$).

Total number of bones in the human skull excluding the hyoid and ear ossicles

$22$ bones ($8$ cranial bones and $14$ facial bones).

Bone count and inventory of the human cranium (brain box)

$8$ bones: $1$ frontal, $2$ parietal, $2$ temporal, $1$ occipital, $1$ sphenoid, and $1$ ethmoid.

Saddle-shaped depression in the sphenoid bone that houses the pituitary gland

Sella turcica.

Large posterior aperture of the occipital bone through which the medulla oblongata continues as the spinal cord

Foramen magnum.

Two rounded cranial articular projections that articulate with the first cervical vertebra

Occipital condyles.

Vertebrate groups characterized by a dicondylic skull

Mammals and amphibians.

Vertebrate groups characterized by a monocondylic skull

Fishes, reptiles, and birds.

Bone count and inventory of the human facial skeleton

$14$ bones: $2$ nasal, $2$ maxillae, $2$ zygomatic, $2$ lacrimal, $2$ palatine, $2$ inferior nasal conchae, $1$ vomer, and $1$ mandible.

Largest, strongest, and only movable bone of the human face

Mandible.

Triangular unpaired facial bone forming the inferior and posterior part of the nasal septum

Vomer.

Anatomical characteristics and muscular attachment of the hyoid bone

Single U-shaped bone located at the base of the buccal cavity that does not articulate with any other bone and anchors the tongue.

Three middle ear ossicles arranged in sequence from outer to inner ear

Malleus, Incus, and Stapes.

Morphological shapes corresponding to the malleus, incus, and stapes

Hammer-shaped (malleus), anvil-shaped (incus), and stirrup-shaped (stapes).

Smallest bone present in the human body

Stapes.

Total number of ear ossicles in the human body

$6$ bones ($3$ in each middle ear cavity).

Total number of vertebrae in the human vertebral column during infancy versus adulthood

$33$ vertebrae in infants, reducing to $26$ functional bones in adults due to fusion.

Adult human vertebral formula

$\text{C}_7\text{T}_{12}\text{L}_5\text{S}_{(5)}\text{Co}_{(4)} = 26$ vertebrae.

First cervical vertebra (C1) and its primary articulating function

Atlas, which articulates with the occipital condyles to support the skull and facilitate nodding ('yes') movements.

Second cervical vertebra (C2) and its distinctive articulating process

Axis, possessing an odontoid process (peg) that forms a pivot joint with the atlas for head rotation ('no' movement).

Number of cervical vertebrae present in almost all mammals

$7$ cervical vertebrae.