(FLASHCARDS) Lesson 12: How do animals move?

Hydrostatic skeleton

Fluid filled cavity surrounded by muscles. The muscles exert force against the fluid to facilitate movement. (Earthworms)

Exoskeleton

External, rigid skeleton composed of chitin. Provides attachment and serves as the site of muscle attachment. Growth, however, is restricted. (arthropods such as crustaceans)

Endoskeleton

Composed of rigid internal elements the provide structural support and muscle attachment points. Primarily composed of bone and cartilage or calcite

Cartilage

A specialized connective tissue designed to withstand compression and tension; it is tough yet flexible and found in many joints

Chondroblasts

Cartilage consists of ____________ which secret extracellular matrix and becomes trapped within lacunae, maturing into chondrocytes.

Glycoproteins and collagen fibers

Cartilage matrix is composed of…

avascular

Cartilage is ___________, meaning it lacks blood vessels and because of this, it heals slowly.

Bone

A specialized connective tissue that is strong but inflexible.

collagen fibers and polysaccharides

Bone consists of organic components such as __________ and ___________ for flexibility.

inorganic hydroxyapatite

Bone consists of ______________________ for hardness.

Osteoblasts

____________ secrete an enzyme that promotes hydroxyapatite formation, giving bone its rigidity.

osteocytes

Some osteoblasts become trapped in the matrix, transforming into ______________, which reside in lacunae and connect via tiny canals called canaliculi for intercellular communication.

Intramembranous ossification

Process by which flat bones like the skull develop

Endochondral ossification

Process by which long bones like the vertebrate, ribs, and limbs develop

epiphyses

Growth occurs at the ______________ (widened ends of bones) in growth plates made of cartilage.

bone lengthening

Young cartilage cells undergo mitosis, thicken, age, and die, contributing to ________________.

calcification

Young cartilage cells undergo mitosis, thicken, age, and die, contributing to bone lengthening.

Simultaneously, _______________ occurs from the shaft side, replacing cartilage with bone.

late adolescence

Growth in length stops in _______________, but width growth continues throughout life.

Osteoblasts

Involved in bone formation

mechanical stress and hormones

Bone remodeling is stimulated by ____________and_______________.

produce more bone matrix

Increased mechanical stress (e.g., weightlifting) signals osteoblasts to __________________________, strengthening the bone.

bone deposition

Osteoporosis occurs when bone resorption outpaces _______________, leading to fragile bones. Treatments include a high-calcium diet, vitamin D, and weight-bearing exercise to stimulate bone growth.

contract

Muscles ____________ to generate movement at joints

Origin

The fixed attachment point of a muscle.

Insertion

Movable attachment point

Antagonistic muscles

One muscle produces a movement that is reversed by another (e.g., quadriceps extend the leg while hamstrings flex it).

Ball-and-socket

Joints that allow a wide range of motion (hip, shoulder)

hinge joints

Joints that permit movement in one direction (knee, elbow)

Gliding joints

Joint that allows sliding motions (vertebrae, wrist)

Combination joints

allow rotation and side to side movement (jaw)

long multinucleated muscle fibers

Skeletal muscle consists of bundles of _________________________.

thick (myosin) and thin (actin) filaments

Each muscle fiber contains myofibrils, composed of

sarcomere

The structural unit of contraction is the ___________, spanning from Z-line to Z-line.

A bands

_________ (dark regions) contain stacked thick filaments.

I bands

___________ (light regions) contain only thin filaments.

H zone

________ (within A band) has only thick filaments

slide past each other

During contraction: Actin and myosin filaments ________________, shortening the sarcomere

Myosin heads

____________ bind to actin, forming cross-bridges.

Power stroke

Myosin pulls actin toward the sarcomere’s center

tropomyosin

At rest, ___________ blocks actin-binding sites

troponin

Calcium ions (Ca²⁺) bind to ___________, shifting tropomyosin to expose actin-binding sites.

sarcoplasmic reticulum

Ca²⁺ is released from the __________________ when stimulated by a motor neuron at the neuromuscular junction.

Slow-twitch fibers

• Rely on aerobic respiration.

• High capillary density, mitochondria, and myoglobin (appear dark).

• Fatigue-resistant, ideal for endurance activities (e.g., marathon running).

Fast twitch fibers

• Generate rapid power, fatigue quickly.

• Some respire anaerobically, relying on glycogen stores.

• Fewer capillaries, mitochondria, and myoglobin (appear white).

• Suited for short bursts of activity (e.g., sprinting).

Osteoclasts

dissolves bone by releasing Ca++ (immune cells derivatives)

lacunae

These are small spaces connected by canaliculi containing osteocytes in the Haversian system