BIOL 1040 - Chapter 30

Movement

A distinguishing characteristic of animals. 

Involves changing position of body parts relative to one another. 

All require energy, & rely on the movement of cellular strands of protein against one another.

Locomotion

Active travel from place to place. 

Requires movement of body parts. 

Requires additional energy to overcome gravity & friction. 

Animals that “move” but don’t locomote: Sponges, anemones, tubeworms, muscles. 

Types of Locomotion 

Swimming

Walking

Running 

Hopping

Crawling  (& Burrowing)

Flying

Three Main Types of Skeletal Systems: 

Hydrostatic skeletons 

Exoskeletons 

Endoskeletons 

What do skeleton systems provide

Body support & shape. 

Movement by working with muscles. 

Protection of internal organs.

Hydrostatic Skeleton

A skeleton made up of fluid held under pressure in a closed body compartment;  the shape of the compartments controls the animal's form. 

Protect other body parts by cushioning them from shocks. 

Organisms having hydrostatic skeletons include Cnidarians (e.g. Hydra, jelly fish), the worms (e.g. Planarians, nematodes, earthworms). 

Plants have hydrostatic turgor pressure in combination with a rigid cell wall that together function as the hydrostatic skeletal system for the soft fleshy parts.

Exoskeletons

rigid “non-living” external skeletons (or shells) that are found in arthropods & Molluscs. They consist of .

Chitin and protein in Arthropods. Must be shed to permit growth.

Calcium carbonate in Molluscs. 

Endoskeletons

hard or leathery supporting elements situated among the soft tissues of an animal. They are made of 

Cartilage or cartilage and bone (vertebrates). 

Spicules (sponges) -- are variously made out of calcium carbonate, silica, while others are made of spongin.  Starfish endoskeletal plastes are made of calcium carbonate (for some support), but they also utilize a hydroskeleton for locomotion, the endoskeleton is mostly for support. 

Hard plates (echinoderms – sea urchins & starfish).The “shell” of a sea urchin (its “test”) appears to be an exoskeleton, but technically its an endoskeleton because it is covered with a thin layer of living fleshy tissue.

General Characteristics of vertebrae skeleton: 

Distinguishing features of vertebrates. 

Composed of bone & cartilage

Surrounded by soft tissues (protects skeleton). 

Grows with animal (does not limit growth). 

Has parts for protection of vital internal organs. 

Jointed & segmented to allow greater flexibility & mobility. 

Skeleton of a tree shrew is shown. 

Bones are composed mainly of hydroxyapatite (70%) and collagen (30%).

Main subdivisions of vertebrae skeletons

Axial Skeleton – the supporting axis – skull, vertebral column & rib cage. 

Appendicular skeleton – bones comprised of appendages & those that anchor them to the axial skeleton.

Fibrous connective tissue (periosteum)

is a membrane composed of dense, irregular, fibrous connective tissue that lines the outer surface of all bones except at the joints of long bones.  It protects bones from harm and serves as a site for muscle attachment. The periosteum is the primary source of precursor cells that develop into chondroblasts( cartilage cells) and osteoblasts ( bone cells) that are essential to the healing of broken bones. 

Red bone marrow

all bone marrow is red at birth, but red marrow gradually converts to yellow marrow as we become adults. After adulthood, only flat bones and ends of long bones (i.e. “spongy bone tissue”) contains red marrow. 

Yellow bone marrow

is yellow because it is enriched in & stores fat that can be used as a last resort as a source of food/energy during extreme starvation.  More importantly, it can convert back to red bone marrow in 1-2 days in cases of severe blood loss.  This occurs to help quickly replenish the supply of RBC’s that is urgently needed. 

Cartilage

 at the ends of bones – cushions joints; reduces friction of movements.

Four types of cells in bones

Osteogenic cells – stem cells that give rise to all other bone cells. 

Osteoblasts – bone-forming cells; remove calcium from blood & deposit Ca2+ salts into forming bone. 

Osteocytes – mature bone cells trapped or located in the lacunae of bone that maintain bone tissue; thought to be the “mechanosensor cells” that control the activities of osteoblasts & osteoclasts. 

Osteoclasts – bone-absorbing cells that break down bone & return calcium to blood. Broken bones are realigned and immobilized; bone cells build new bone, healing the break.

Three Types of Skeletal Joints: 

Fibrous Joints

Cartilagenous Joints

Synovial Joints

Fibrous Joints

tight immovable joints, where separate bones are held together by connective fibers (e.g. bones of skull and tooth & socket joints). 

Cartilagenous Joints

slightly movable joints between bones that are joined together by strips or disks of cartilage (e.g. in ribs, vertebrae & hip bones). 

Synovial Joints

freely movable joints that are enclosed in a fibrous capsule; bones are separated by a fluid-filled cavity and stabilized (held together) by ligaments.

Diffrent types of joints

Ball-and-socket joints – enable rotation in the arms and legs. 

Hinge joints – in the elbows and knees permit movement in a single plane.

Pivot joints – enable the rotation of the forearm at the elbow.

diseases and conditions that affect the skeletal system

Osteoporosis  

Rheumatoid Arthritis

Osteo Arthritis

Tendonitis & Bursitis

Tennis Elbow

Three Types of Muscle:

Cardiac – involuntary muscle of the heart.

Smooth – involuntary muscles of the internal organ systems (except the heart).

Skeletal – voluntary muscles attached to the skeletal system for movement & locomotion

How do muscles move bone (simple)

By contraction

Muscles & bones function like levers.

Simple… what happens when muscles contract

actin overlaps each other

The sequence of Steps in the Mechanism of Sliding Filaments

1. ATP binds to myosin head, resulting in the low energy (detached) configuration.

2. Myosin hydrolyzes ATP to ADP & Pi; both remain bound to myosin; energy released causes the myosin head to extend to the actin filament.

3. Myosin head latches onto its actin binding site forming a cross bridge between the two filaments.

4. ADP & Pi are released, and the myosin head reverts back to its low-energy configuration (i.e. the “power stroke”), causing the actin filament to move toward the center of the sarcomere.

5. The cross bridge remains attached until another ATP binds to the myosin head, thereby repeating the above process.

6. The sequence:  detach, extend, attach, pull, detach repeats many times; the combined action of hundreds of heads results in the contraction of the entire muscle

   

Motor Neurons:

Carry nerve impulses (action potentials) from the CNS to muscles.

Axons of each motor unit branches out to synapse with many muscle fibers (cells).

Synaptic terminals release acetyl-choline into the synaptic cleft.

Acetylcholine initiates a muscle contraction

Motor Unit

a single axon that branches to (or synapses with) approximately 2000 individual muscle fibers (cells).

How does Acetylcholine trigger the muscle process

triggers an action potential in the muscle cell plasma membrane.

The action potential travels in all directions along the surface of the muscle cell, and deep into the cell via T tubules.

Depolarization of T tubules triggers the release of Ca2+ ions from the endoplasmic reticulum (aka sarcoplasmic reticulum).

Ca2+ ions facilitate muscle contraction by binding to troponin. 

Troponin causes the regulatory protein tropomyosin to move away from the myosin-binding sites on actin.

Myosin heads cause actin filaments to “slide” relative to myosin filaments.

— Respiration Supplies Most of the Energy for Exercise

Aerobic

Aerobic Respiration

includes glycolysis, the TCA cycle & respiratory electron transport and chemiosmosis.

Glucose

from foods, and glycogen stored in liver & muscles.

Lactic acid fermentation

occurs when oxygen becomes limiting.