Chapter 40

osteoclasts

- ... are large, multinucleated cells that resorb (break down) bone. -move about, secreting hydrogen ions that dissolve the crystals and enzymes that digest the collagen. - ... and osteoblasts are synergistic; together they shape bones. -adult human skeleton is completely replaced every 10 years

muscle contraction

-A muscle contracts when actin and myosin filaments move past one another. The length of each filament remains the same. 1) Muscle fiber in relaxed state. Note that I band and H zone are relatively wide. 2) Muscle fiber contracting. Actin and myosin filaments move past one another, increasing amount of overlap between actin and myosin filaments. Note that I band and H zone decrease in length. Filaments themselves do not become shorter. 3) Contracted muscle fiber. Actin filaments overlap, eliminating H zone. I bands also disappear as Z lines are pulled close to myosin filaments.

lactic acid

-Accumulation of the waste product ... also contributes to muscle fatigue. -Well-conditioned athletes develop the ability to tolerate the high levels of ... generated during high-performance activity. -The period of rapid breathing that generally follows strenuous exercise pays back the oxygen debt by consuming ....

depolarization

-Acetylcholine binds with receptors on each muscle fiber, causing ..., a change in the distribution of electric charge across its sarcolemma. -can generate an ACTION POTENTIAL, an electrical signal that travels along the membrane of the muscle fiber (or neuron).

simple twitch

-An important factor affecting the tension of contracting muscle fibers is the frequency of stimulation. -In response to a single, brief electrical stimulus, skeletal muscle contracts with a single, quick contraction called a ...

antagonistically

-Because muscles can only contract, they can only pull; they cannot push. Muscles act ... to one another, which means that the movement produced by one can be reversed by another. -example: contraction of the biceps muscle flexes (bends) your arm, whereas contraction of the triceps muscle extends it -The muscle that contracts to produce a particular action is known as the agonist. -The muscle that produces the opposite movement is the antagonist. -When the agonist is contracting, the antagonist is relaxed. -movements are accomplished by groups of muscles working together, so several agonists and several antagonists may take part in any action. -muscles that are agonists in one movement may serve as antagonists in another.

dermis

-Beneath the epidermis lies the ... a dense, fibrous connective tissue made up mainly of collagen fibers. -Collagen imparts strength and flexibility to the skin. -also contains blood vessels that nourish the skin and sensory receptors for touch, pain, and temperature. -Hair follicles and, in most mammals, sweat glands are embedded in the ... -In birds and mammals, the ... rests on a layer of SUBCUTANEOUS TISSUE.

oxygen debt

-During a burst of strenuous exercise, the circulatory system cannot deliver enough oxygen to keep up with the demand of the rapidly metabolizing muscle fibers. The result is an ... -muscle fibers break down fuel molecules anaerobically (without oxygen) for short periods -Lactic acid fermentation is a method of generating ATP anaerobically, but not in great quantity -ATP depletion results in weaker contractions and muscle fatigue.

pacemaker

-Each heartbeat is initiated by a ... mass of specialized cardiac muscle. -A conduction system transmits the signal throughout the cardiac muscle -The cardiac fibers within the atria contract as a functional unit, and the cardiac fibers within the ventricles also function as a functional unit. -heart beats in a regular rhythm independent of a nerve supply. However, the heart rate is regulated, according to the needs of the body, by neurons in the cardiac centers in the medulla of the brain

muscle fiber

-Each striated .... is a long, cylindrical cell with many nuclei -The plasma membrane, known as the SARCOLEMMA in a ..., has multiple inward extensions that form a set of T TUBULES (transverse tubules) -The cytoplasm of a ... is called sarcoplasm, and the endoplasmic reticulum is called the SARCOPLASMIC RETICULUM. -MYOFIBRILS are threadlike structures that run length- wise through the ....

cuticle

-Invertebrate epithelium may secrete a ... -In many invertebrates the outer epithelium is specialized to secrete protective or supportive layers of nonliving material. -In insects and many other animals, the secreted material forms an outer covering called a ... -Some animals, including corals and mollusks, secrete a shell made mainly of calcium carbonate. -many species the epithelium contains cells that secrete lubricants or adhesives. Such cells may release odorous secretions used for communication or for marking trails. -other species secretory cells produce toxins used for offense or defense. -earthworm epithelium secretes lubricating mucus that promotes efficient diffusion of gases across the body wall and reduces friction during movement through the soil. -Epithelial cells may be modified as sensory cells that are selectively sensitive to light, chemical stimuli, or mechanical stimuli, such as contact with an object, or pressure.

exoskeleton

-Mollusks and arthropods have nonliving ... -In most animals the skeleton is a lifeless shell, or ... deposited atop the outer epithelial covering. -In mollusks the ... is a calcium carbonate shell secreted by the mantle, a thin sheet of epithelial tissue that extends from the body wall. provides protection, a retreat used in emergencies -... of arthropods serve not only to protect but also to transmit forces. they are comparable to the skeletons of vertebrates. -arthropod ... is a nonliving cuticle that contains the polysaccharide CHITIN. -consists of large, thick, inflexible plates that completely cover the body. plates are separated from one another by thin, flexible joints arranged segmentally -Enough joints are present to make the arthropod's body as flexible as those of many vertebrates -A disadvantage of the rigid arthropod ... is that to accommodate growth an arthropod must shed its ... and replace it with a new, larger one. -this process, called MOLTING, or ECDYSIS, is char- acteristic of the ECDYSOZOA, a major branch of invertebrates. During ecdysis, the animal is weak and vulnerable to predators.

sliding filament model

-Muscle contraction occurs when the muscle fibers, and thus the sarcomeres, shorten. -This explanation of muscle contraction, known as the ... was developed in the 1950s by two British biologists, Hugh Huxley and Andrew Huxley. not related, independent, came to same conclusion -we now understand that the muscle shortens as the actin and myosin filaments use a ratcheting mechanism to move past one another, increasing their overlap. think of an extension ladder. -overall ladder length changes as the ends get closer or farther apart, but the length of each ladder section stays the same. -The I band and H zone decrease in length, but neither the actin nor myosin filaments themselves shorten.

creatine phosphate

-Muscle fibers have a backup energy storage compound, ..., that can be stockpiled. -energy stored in ... is transferred to ATP as needed, but during vigorous exercise the supply of ... is quickly depleted. -Muscle cells must replenish their supplies of these energy-rich compounds.

sarcomeres

-Myosin and actin filaments are organized into repeating units called ..., the basic units of muscle contraction. -Hundreds of .... connected end to end make up a myofibril. -are joined at their ends by a thin band of interweaving filaments called the Z line. -Each ... consists of overlapping myosin and actin filaments. -The filaments overlap lengthwise in the muscle fibers, producing the pattern of transverse bands or striations characteristic of striated muscle

heads

-One end of each myosin molecule is folded into two globular structures called ... -The rounded ... of the myosin molecules extend away from the body of the myosin filament. -Each myosin molecule also has a long tail that joins other myosin tails to form the body of the thick filament. -ATP is bound to the myosin when the muscle fiber is at rest (not contracting). -Myosin is an adenosine triphosphatase (ATPase), an enzyme that splits ATP to form ADP and inorganic phosphate (P). -Myosin converts the chemical energy of ATP into the mechanical energy of sliding filaments.

factors

-Several ... influence the strength of muscle contraction -contraction of a whole muscle depends on the number of muscle fibers contracting, the tension developed by each fiber, frequency of stimulation, condition of the muscle (e.g., whether or not it is fatigued), and the load on the muscle. -As more muscle fibers contract, the tension in the muscle increases.

ligaments

-The joint capsule is typically reinforced by ... bands of fibrous connective tissue that connect bones and limit movement at the joint.

epidermis

-The outer layer of skin, the .... is a waterproof protective barrier. -consists of several strata, or sublayers. -In humans exposure to ultraviolet (UV) radiation—the short, invisible rays from the sun—causes the ... to thicken and stimulates pigment cells in the skin to produce melanin at an increased rate.

vertebral column

-The vertebrate spine, or ... -supports the body and bears its weight. -In humans it consists of 24 vertebrae and 2 bones composed of fused VERTEBRAE: the SACRUM and COCCYX -the .... consists of the cervical (neck) region, with 7 vertebrae the thoracic (chest) region, with 12 vertebrae the lumbar (back) region, with 5 vertebrae the sacral (pelvic) region, with 5 fused vertebrae and the coccygeal region, also composed of fused vertebrae

summation and tetanus

-When a muscle fiber is allowed to completely relax and is then stimulated a second time, the second twitch is the same magnitude as the first twitch. -When a muscle fiber is stimulated a second time before it has completely relaxed, the second twitch is added on to the first twitch. The result is summation. -A volley of rapid stimuli does not allow the muscle fiber to relax between stimuli. The result is a sustained contraction called tetanus. blank and blank (2 diff. words)

summation

-When a second stimulus is received before the first contraction is complete, the two twitches may add together, a process called ... -Typically, skeletal muscle receives a series of separate stimuli timed very closely together. -... results in a smooth, sustained contraction called TETANUS. -identity and number of our muscle fibers that are tetanically contracting help determine whether we can play the piano, draw a picture, rock a baby, drive a car, or run a mile. -When you lift a heavy object, you place a load on the mus- cles affected. As the weight of the load increases, the muscles contract more strongly (within limits)

motor unit

-a motor neuron is functionally connected with an average of about 150 muscle fibers -However, some motor units have fewer than a dozen ..., and others have several hundred. -Each junction of a ... with a muscle fiber is called a NEUROMUSCULAR JUNCTION -Messages from the brain or spinal cord activate .... -The more ... recruited, the stronger the contractions.

smooth and cardiac muscle

-also contract by sliding filament mechanism -involuntary and autorhythmic (in some cases) autorhythmic: can contract w/o nervous system input -smooth muscle capable of sustained contractions. ex: constant contraction of smooth muscle lining blood vessels. Actin and myosin filaments not organized into myofibrils or sarcomeres. Not striated. -cardiac muscle alternately contracts and relaxes heart. Each heartbeat initiated by pacemaker autorhythmic cardiac muscle fibers

vertebrate skeletal divisions

-appendicular skeleton moves body -pectoral girdles include clavicle and scapula. Loosely attached to vertebral column by muscles -pelvic girdle included two hip bones. fused to vertebral column -limbs

Osteoblasts

-are bone- building cells. Bones are modeled during growth and remodeled continuously throughout life in response to physical stress and other changing demands. adult human skeleton is completely replaced every 10 years -They secrete the protein collagen, which forms the strong fibers of bone. -compound hydroxyapatite, composed mainly of calcium phosphate, is present in the interstitial fluid (tissue fluid). automatically crystallizes around the collagen fibers to form the hard matrix of bone. -As the matrix forms around the osteoblasts, they become isolated within the lacunae. The trapped osteoblasts are then called OSTEOCYTES.

joints

-are junctions b/n bones -Some joints don't allow much or any movement -sutures b/n skull bones -joints b/n vertebrae and pubic bones -most joints allow movement. enclosed by joint capsule made of connective and epithelial tissues. -epithelium secretes synovial fluid to reduce friction and absorb shock. stabilized by ligaments

joints

-are junctions between bones -or articulations, are junctions between two or more bones. -facilitate flexibility and movement. -at the ... the outer surface of each bone consists of ARTICULAR CARTILAGE. -a way to classify ... is according to the degree of movement they allow -immovable, slightly moveable , and freely movable -With time and use, ... wear down

Myofibrils

-are threadlike structures that run length- wise through the muscle fiber. -They consist of even smaller structures called FILAMENTS. -There are two types of filaments: myosin and actin filaments. -MYOSIN FILAMENTS are thick, consisting mainly of the protein myosin -The thin ACTIN FILAMENTS consist mostly of the protein actin; they also contain the proteins TROPOMYOSIN and TROPONIN, which regulate the actin filament's interaction with myosin filaments.

vertebrate bone structure

-bone layers. covered by periosteum -adds new layers to bone -where tendons and ligaments attach -beneath periosteum is hard, dense compact bone -thin strands of spongy bone fill interior. One marrow fills spaces between spongy bone. red one marrow produces new blood cells -metaphysis: cartilage disc that lengthens bone in children. becomes epiphyseal line (bone) in adults

skeletal system disorders

-bones: osteoporosis-osteoclasts outspace osteoblasts and bone become fragile. estrogen stimulates osteoclast activity -joints: arthritis-articular cartilage wears down and joints become inflamed. rheumatoid arthritis: synovial membrane becomes inflamed. synovial fluid accumulates, causing pain and progressive deformity. autoimmune disorder.

Fast-oxidative fibers

-contract rapidly and have an intermediate rate of fatigue. -Like slow-oxidative fibers, they are rich in mitochondria and obtain most of their ATP from aerobic respiration. -They also have a high myoglobin content and a red color. Contraction speed: Fast Rate of fatigue: intermediate Major pathway for ATP synthesis: aerobic respiration Mitochondria: many Intensity of contraction: intermediate Myoglobin content: high Color of fiber: red

Cardiac muscle

-contracts and relaxes in alternating rhythm, propelling blood with each contraction. -not under voluntary control -Sustained contraction of ... would be disastrous -... fibers are electrically coupled by junctions called INTERCALATED DISCS. -Gap junctions within the intercalated discs allow action potentials to spread rapidly from one cardiac fiber to another.

skeletal muscle organization

-each skeletal muscle composed of many bundles of muscle fibers each muscle fiber composed of many bundles of myofibrils myofibrils made of contractile units called sarcomeres sarcomeres lined up end to end along length of myofibril made of overlapping mystic and actin filaments

vertebrate integumentary system

-epidermis: outer layer of stratified squamous epithelium. New cells continually produced in deepest layer. Fill with keratin as pushed to surface and they eventually die and are sloughed off. Pigment cells produce Melanin which absorbs UV -dermis: dense connective tissue. contains blood vessels, sensory receptors, hair follicles + sebaceous glands (mammals only), and sweat glands (mammals only) -in birds and mammals, subcutaneous layer below dermis primarily adipose tissue -melanocytes transfer melanin to epidermal cells -UV radiation stimulates increased melanin production

Fast-glycolytic fibers

-generate a great deal of power and carry out rapid movements but can sustain that activity for only a short time. -are important in activities such as sprinting and weight lifting. -contract rapidly, have few mitochondria, and obtain most of their energy from glycolysis. -When their glycogen supply is depleted, they fatigue rapidly. -These fibers have a low myoglobin content and are white. sometimes referred as white fibers -People who are sedentary have more ... than do physically fit individuals -With physical training, these fibers change to fast-oxidative fibers. Contraction speed: fast Rate of fatigue: fast Major pathway for ATP synthesis: glycolysis Mitochondria: few Intensity of contraction: high Myoglobin content: low Color of fiber: white

invertebrate skeletal systems

-hydrostatic skeletonL fluid filled body compartments change shape/move when muscles contract against fluid a disadvantage is slow, crude movements -exoskeleton: nonliving 'shell' over outer epithelium disadvantage: may need to be molted. protein and chitin. -echinoderms have living endoskeleton covered by skin Use hydrostatic skeleton for movement

vertebrate epithelial coverings

-integumentary system includes skin and structures derived from skin Functions- protection: fish and reptile scales gas exchange: amphibians insulation: bird feathers, mammal fur -mammal structures derived from skin claws/nails, hair/fur, sweat, oil, and mammary glands, and sensory receptors

invertebrate epithelial coverings

-invertebrate outer epithelium may: secret nonliving covering for protection (exoskeleton, cuticle, or shell) secrete substances for adhesion, lubrication, defense or communication function in detecting stimuli

rib cage

-is a bony "basket" formed by the sternum (breast- bone), thoracic vertebrae, and, in mammals, 12 pairs of ribs. -protects the internal organs of the chest, including the heart and lungs. -also supports the chest wall, preventing it from collapsing as the diaphragm contracts with each breath. -each pair of ribs is attached dorsally to a separate vertebra -Of your 12 pairs of ribs: the first 7 are attached ventrally to the sternum the next 3 are attached indirectly by cartilage and the bottom 2, the "floating ribs," have no attachments to the sternum.

melanin

-is an important protective screen against the sun because it absorbs some of the harmful UV rays. -increase in melanin causes the skin to darken -suntan is actually a sign that the skin has been exposed to too much UV radiation. -When the .... cannot absorb all the UV rays, the skin becomes inflamed, or sunburned. -Dark-skinned people have more melanin, so they suffer less sunburn, wrinkling, and skin cancer than lighter- skinned people. However, they still require protection from UV rays.

Skeletal muscle

-is the most abundant tissue in the vertebrate body -Its elongated cells, called MUSCLE FIBERS, are organized in bundles wrapped by connective tissue. biceps in your arm, for example, consists of thousands of individual muscle fibers and their connective tissue coverings

vertebrate endoskeleton

-made of bone and/or cartilage -attached to muscles and covered by connective and epithelial tissues -two divisions: axial skeleton supports and protects central axis of body 1) skull protects brain and forms facial structure 2) vertebral column supports body and bears weight. Vertebrate + sacrum + coccyx 3) Rib cage supports chest wall and protects heart and lungs Sternum + thoracic vertebrate + ribs

invertebrate muscle tissue

-most invertebrates have muscle tissue organized into layers or bands -may have smooth (pectoral retractor muscle) and/or skeletal muscle (elevator muscles pull wings down)

sarcomeres

-motor neurons carry information form CNS to muscle fibers motor unit: single motor neuron connected to approx. 150 muscle fibers At neuromuscular junction, motor neuron releases acetylcholine (ACh) 1) ACh generates action potential in muscle fiber 2) releases stored Ca2+ 3) Ca2+ binds to sarcomere, which allows myosin filaments to pull (ATP) actin filaments towards center of sarcomere 4) sarcomere shortens -muscle fibers relax when ACh no longer released

muscle contraction process

-muscle contracts when muscle fibers shorten, which pulls tendon attached to bone sliding filament mechanism: when sarcomeres shorten-> myofibrils shorten-> muscle fibers shorten-> muscle contracts sarcomeres shorten when myosin attaches to and pulls actin filaments towards middle of sarcomere -muscles are adapted for contracting; during contraction, energy from ATP is used to move muscle filaments so that the muscle shortens. Body parts move when muscles pull on them.

Smooth muscle

-not under voluntary control -is not attached to bones but instead forms tubes that squeeze like the muscle tissue in the body wall of the earthworm. -contracts in response to simple stretching, and its contraction tends to be sustained. -well adapted to performing such tasks as regulating blood pressure by sustained contraction of the walls of the arterioles. -although it contracts slowly it shortens much more than striated muscle does; it squeezes impressively. -is not striated because its actin and myosin filaments are not organized into myofibrils or into sarcomeres. -The fibers of ... tissue function as a unit because they are connected by GAP JUNCTIONS, which permit electrical signals to pass rapidly from fiber to fiber. -although ... is similar to skeletal muscle contraction (occurring by a sliding filament mechanism), the cross bridges in smooth muscle remain in the attached state longer. -less ATP is required to maintain a high level of force in ... than in skeletal muscle.

radius

-one of the two bones of the forearm, is a typical long bone -Its numerous muscle attachments are arranged in such a way that the bone rotates about its long axis and operates as a lever, amplifying the motion generated by the muscles. -by themselves muscles cannot shorten enough to produce large movements of the body parts to which they are attached to. -is covered by a connective tissue membrane, the PERIOSTEUM,

bone cells

-osteocytes (mature bone cells) contained in lacunae (cavities). lacunae arranged in circles around central canals. canals contain nerves and blood vessels -osteoblasts and osteoclasts remodel bone throughout life -osteoblasts: one building cells. secrete collagen, extracellular calcium salts crystallize around collagen fibers -osteoclasts: bone resorbing cells

ATP

-powers muscle contraction -the immediate source of energy for muscle contraction is ... -Energy stored in ... molecules powers attachment of the myosin heads to the actin filaments, bending of the cross bridges, and release of the myosin heads. -Note that energy is needed not only for the pull exerted by the cross bridges, but also for their release from each active site.

sutures

-the ... between bones of the human skull are IMMOVABLE JOINTS. -in a ... bones are held together by a thin layer of dense fibrous connective tissue, which may be replaced by bone in the adult.

Invertebrate muscle

-the contractile cells of the hydrostatic skeleton of Hydra and other cnidarians. -In most other animal groups, muscle is a specialized tissue organized into definite layers, or straplike bands -Some invertebrate phyla have skeletal and smooth muscle. -Bivalve mollusks, such as clams, have two sets of muscles for opening and closing the shell. their smooth muscle, which is capable of slow, sustained contraction at low energy cost, keeps the two shells tightly closed for long periods, even weeks at a time. -Striated muscle, which contracts rapidly, is used to swim and to shut the shell quickly when the mollusk is threatened. -Arthropod muscles are striated, even in the walls of the digestive tract. -Insect flight muscles contract more rapidly than any other known muscle, up to 1000 contractions per second. insect flight muscles in action have the highest known metabolic rate of any muscle tissue. -insect flight muscles contain more mitochondria than any other known variety of muscle. Their mitochondria have more cristae (folds of their inner membranes) and can consume oxygen twice as fast as mammalian mitochondria. -insect muscle are also elaborately infiltrated with TRACHEAE, tiny air-filled tubes that carry oxygen directly to each muscle fiber. -insects warm up b4 they fly b/c an increase in body temp increases the rate of ATP synthesis

osteoporosis

-the most common progressive and degenerative bone disease, bone is broken down more rapidly than it is rebuilt. -women: the decrease in estrogen after menopause accelerates bone resorption. -... patients lose so much bone mass that their bones become fragile and fracture easily.

Motor neurons

-transmit messages from the brain or spinal cord to muscle fibers. -When a ... transmits a message, it releases the neurotransmitter ACETYLCHOLINE into the SYNAPTIC CLEFT, a small space between the motor neuron and each muscle fiber.

vertebrate muscle tissue

-vertebrates have skeletal, cardiac, and smooth muscle tissue -skeletal muscle is most abundant vertebrate tissue. produces movement by pulling on tendons attached to bone works antagonistically: movement produced by one skeletal muscle reversed by another Ex: biceps contracts to flex arm, triceps contracts to extend arm when biceps contracted, triceps relaxed and vice versa -muscle fibers only contract, so muscles can only pull, they can't push

cross bridge

-when ATP is split, the ADP and Pi initially remain attached to the myosin head. -The myosin head (with ADP and Pi still bound to it) is in an energized state; it is "cocked." -The myosin head binds to an exposed active site on the actin filament, forming a ... linking the myosin and actin filaments. -inorganic phosphate is then released, which triggers a conformational change in the myosin head. -The myosin head bends about 45 degrees, in a flexing motion. This movement, the POWER STROKE, pulls the actin filament closer to the center of the sarcomere. During the power stroke, the ADP is released. -new ATP must bind to the myosin head before the myosin can detach from the actin. -If sufficient calcium ions are present, the cycle begins anew. -Energized once again, myosin heads contact a second set of active sites on the actin filament. This next set is farther down the filament, closer to the end of the sarcomere. -This series of stepping motions pulls the actin filaments toward the center of the sarcomere.

Slow oxidative fibers

1 of 3 types of skeletal muscle fibers have been identified in vertebrates -are well adapted for endurance activities such as swimming and running long distances. -These fibers also help maintain posture. -They contract slowly and fatigue slowly. -require a steady supply of oxygen. -They derive most of their energy from aerobic respiration and are rich in mitochondria and capillaries. -are rich in MYOGLOBIN, a red pigment similar to hemoglobin, which stores oxygen in red blood cells. -because of myoglobin .... are red and are sometimes called red fibers. Contraction speed: slow Rate of fatigue: slow Major pathway for ATP synthesis: aerobic respiration Mitochondria: many Intensity of contraction: low Myoglobin content: high Color of fiber: red

muscle contraction sequence

1) Acetylcholine (released by motor neuron) combines with receptors on muscle fiber, causing depolarization and an action potential. 2) Action potential spreads through T tubules, stimulating Ca2+ release from sarcoplasmic reticulum. 3) Ca2+ bind to troponin, causing change in shape. Troponin pushes tropomyosin away, exposing active sites on actin filament. 4) ATP (attached to myosin) is split; energy released "cocks" the myosin head. Myosin heads bind to exposed active sites, forming cross bridges. 5) Pi released from myosin heads; triggers power stroke. 6) Cross bridges bend; actin filaments are pulled toward center of sarcomere. This movement is the power stroke. ADP is released. 7) Actin-myosin complex binds ATP, and myosin detaches from actin. If Ca2+ is available, cycle repeats. 3) Ca2+ bind to troponin, causing change in shape. Troponin pushes tropomyosin away, exposing active sites on actin filament. -The energy of ATP powers muscle contraction. During the power stroke, myosin heads move actin filaments toward the center of the sarcomere, which shortens the muscle.

human limb

Each .... consists of 30 bones and terminates in five digits, the fingers and toes. -more specialized appendages of other tetrapods may be characterized by four digits (as in the pig) -three (the rhinoceros) -two (the camel) -or one (the horse)

birds

Entire muscles may be specialized for quick or slow responses. -In chickens, the white breast muscles are efficient for quick responses, perhaps because a short flight is an escape mechanism for chickens. -However, they walk about on the ground all day; the dark (red) meat of the leg and thigh is muscle specialized for more sustained activity. -Birds that fly have red breast muscles specialized to support sustained activity.

sebum

Oil glands secrete ..., a mixture of fats and waxes that inhibits the growth of harmful bacteria.

Bands in striated muscle

are designated by the letters A, H, and I. -The I band consists of parts of actin filaments of two adjacent sarcomeres. -The A band is the wide, dark region that includes overlapping myosin and actin filaments. -Within the A band is a narrow, light area, the H zone, made up exclusively of myosin filaments; the actin filaments do not extend into this region. -system of proteins holds each stack of myosin filaments together. These proteins are visible as a thin line, the M line, that extends down the center of the H zone within the A band.

keratin

as epidermal cells move towards the body surface epidermal cells manufacture ... -an elaborately coiled protein that gives the skin considerable mechanical strength and flexibility. -is insoluble and serves as a diffusion barrier for the body surface.

slightly movable joints

found between vertebrae, are made of cartilage. These joints help absorb shock.

muscular system

generates the mechanical forces and motion necessary for locomotion and for manipulation of objects. -Muscle also powers many physiological actions necessary to maintain homeostasis. -animals have digestive systems that push food along with peristaltic contractions and hearts that pump internal circulating fluids. -animals also have blood vessels that maintain their pressure with gentle squeezing.

integumentary system

includes the skin and structures that develop from it. -In many fishes, in some reptiles, and in the ant-eating pangolin skin has developed into a set of scales formidable enough to be considered armor. -Even human skin has considerable strength. -The thin, moist skin of many amphibians is adapted for gas exchange as well as for defense. -Derivatives of skin differ considerably among vertebrates. Fishes have bony or toothlike scales. Amphibians have naked skin covered with mucus. . Reptiles have epidermal scales. mammals have hair, and birds have feathers that provide even more effective insulation than fur. -fur and feathers are insulating structures that help maintain body temperature by trapping heat in the body. -skin and its derivatives are often brilliantly colored, helps in communication, in courtship rituals and in territorial displays. -in mammals structures derived from skin include claws (modified as fingernails and toenails in primates), hair, sweat glands, oil (sebaceous) glands, and several types of sensory receptors that give mammals the ability to feel touch, pressure, temperature, and pain. skin of mammals also contains mammary glands, specialized in females for secretion of milk.

skull

the bony framework of the head, consists of the cranial and facial bones. -the human ..., 8 cranial bones enclose the brain, and 14 bones make up the facial portion of the ... -cranial bones that are single in the adult human result from fusion of 2 or more bones that are separate in the fetus or newborn.

stratum basale

the epidermis deepest layer is the ... -Pigment cells in ... and in the dermis below produce MELANIN, a pigment that contributes to the color of the skin. - .... epithelial cells continuously divide and are pushed outward as other cells are produced below them. Epidermal cells mature as they move toward the skin surface.

stratum corneum

the epidermis most superficial layer is the -As epidermal cells move through ..., they die. When they reach the outer surface of the skin, they wear off and must be continuously replaced.

Rigor mortis

the temporary but very marked muscle stiffening that occurs after death, results from ATP depletion. -When death occurs, cellular respiration ceases, and ATP is used up. -However, at the time of death, many muscle fibers are in the process of contraction, and cross bridges have formed. -Because ATP is essential for release of the myosin heads, cross bridges remain intact. -... does not persist indefinitely because the entire contractile apparatus of the muscles eventually decomposes, restoring pliability. -is temperature dependent, so given the prevailing tempera- ture, a medical examiner can estimate the time of death of a cadaver from its degree of ....

periosteum

to which muscle tendons and ligaments attach. -can produce new layers of bone, thus increasing the bone's diameter

UV radiation

damages DNA, causing mutations that lead to malignant transformation of cells -Skin cancer is the most common type of cancer in humans, and most cases of skin cancer are caused by excessive, chronic exposure to UV radiation. -MALIGNANT MELANOMA, the most lethal type of skin cancer, is increasing faster than any other type of cancer. -understanding of the Ras/ERK cell signaling pathway has led to research aimed at developing targeted drugs for treating melanoma. this pathway is the main signal- ing cascade for cell division and differentiation.

muscle contraction sequence

-Each time the myosin heads attach, move 45 degrees, detach, and then re-attach farther along the actin filament, the muscle shortens. -imagine the myosin heads engaging "hand over hand" with the actin filaments -when many sarcomeres contract simultaneously, they contract the muscle as a whole 1. A motor neuron releases acetylcholine, which binds with receptors on the muscle fiber; binding causes depolariza- tion and generation of an action potential. 2. The action potential spreads through T tubules, triggering Ca21 release from the sarcoplasmic reticulum. 3. Ca21 bind to troponin, causing troponin to change shape, which exposes the active sites on the actin filaments. 4. ATP (attached to myosin) is split, and the energized myo- sin head is cocked; it binds to the active site on the actin filament, forming a cross bridge. 5. The release of Pi from the myosin head triggers the power stroke. 6. During the power stroke, the myosin head pulls the actin filament toward the center of the sarcomere, shortening the muscle; ADP is released. 7. The myosin head binds a new ATP and detaches from actin. If the concentration of Ca21 is high enough, the cycle repeats from step 3. -ATP powers contraction through repeated cycles of cross bridge formation followed by myosin heads pulling actin filaments toward the center of the sarcomere -when impulses in the motor neuron cease, the enzyme acetylcholinesterase in the synaptic cleft inactivates acetylcholine. Muscle fibers return to their resting state. -Calcium ions are pumped back into the sarcoplasmic reticulum by active transport, a process that requires ATP. calcium removal is key for muscle relaxation. without Ca2+ tropomyosin once again covers active sites on the actin filaments. -actin filaments move back to their original position, and the muscle relaxes. This entire series of events happens in milliseconds.

muscle tone

-Even when you are not moving, your muscles are in a state of partial contraction known as ... -At any given moment, some muscle fibers are contracted, stimulated by messages from motor neurons. -... is an unconscious process that keeps muscles prepared for action. -When the motor nerve to a muscle is cut, the muscle becomes limp (completely relaxed, or flaccid) and eventually atrophies (decreases in size).

glycogen

-Fortunately, there is yet another backup energy storage com- pound. Muscle fibers store chemical energy in ... a large polysaccharide formed from hundreds of glucose molecules. -can be degraded, yielding glucose, which is then degraded in cellular respiration -When sufficient oxygen is available, enough energy is captured from glucose to produce needed quantities of ATP and creatine phosphate.

hydrostatic skeletons

-In ... body fluids transmit force -Many soft-bodied invertebrates have ... made of fluid-filled body compartments. -Ex: an elongated ballon full of water -Many invertebrates, including most cnidarians, flatworms, annelids, and roundworms, have ... that work something like a balloon filled with water. -Fluid in a closed compartment of the body is held under pressure. -When muscles in the compartment wall contract, they push against the tube of fluid. Because fluids cannot be compressed, the force is transmitted through the fluid, changing the shape and movement of the body -more complex ... of the annelid worm lets it move with increased flexibility. -segments divided by transverse partitions, or septa allows the hydrostatic skeleton of each segment to be largely independent. -examples of ... in invertebrates equipped with shells or endoskeletons and even in vertebrates with endoskeletons of cartilage or bone. -sea stars and sea urchins have an endoskeleton, but they move their tube feet by an ingenious adaptation of a .... -the human penis becomes erect and stiff because of the turgidity of pressurized blood in its internal spaces

antagonistic

-In Hydra and other cnidarians, cells of the two body layers can contract. contractile cells in the outer epidermal layer lie longitudinally, whereas the contractile cells of the inner layer (the gastrodermis) are arranged circularly around the central body axis. -The two groups of cells work in ... fashion: what one can do, the other can undo. -the inner (circular) layer contracts, the hydra thins, and its fluid contents force it to lengthen. when the epidermal (longitudinal) layer contracts, the hydra shortens -fluid in the gastrovascular cavity, force is transmitted so that the hydra thickens as well -hydra is a bag of fluid that acts as a hydrostatic skeleton. the gastrovascular cavity functions as a hydrostatic skeleton because its opening is small. -Hydrostatic skeletons permit only crude mass movements of the body or its appendages

action potential

-In a muscle fiber, an ... is a wave of depolarization that travels along the sarcolemma and into the system of T-tubule membranes. -Depolarization of the T tubules opens calcium channels in the sarcoplasmic reticulum, and stored calcium ions are released into the myofibrils. -Calcium ions bind to the protein troponin on the actin filaments, which changes the shape of the troponin. -This change results in the troponin pushing tropomyosin away from the active sites on the actin filament -These active sites, also called MYOSIN-BINDING SITES, are now exposed

hair follicle

-In humans and other mammals, oil glands empty via short ducts into ... -is the part of a hair below the skin surface, together with the surrounding epithelial tissue.

endoskeletons

-Internal skeletons are capable of growth -Echinoderms and chordates have internal skeletons, or ... -Composed of living tissue. grows along with the animal as a whole -This skeleton consists of plates or shafts of calcium-impregnated tissue (such as cartilage or bone). -echinoderm ... consists of spines and plates of calcium salts embedded in the body wall, beneath an epidermis that covers the body. forms what amounts to an internal shell that provides support and protection -Many echinoderm ... bear spines that project to the outer surface. -most familiar with the ... of vertebrates. This endoskeleton provides support and protection and transmits muscle forces. -class Chondrichthyes (sharks and rays) have skeletons of cartilage, but in most vertebrates the skeleton consists mainly of bone. -bones form systems of levers that transmit muscle forces -Bones store calcium and are important in maintaining homeostatic levels of calcium in the blood.

actin/ myosin

Animals with very simple body plans do not have muscle tissue, but all eukaryotic cells do contain the contractile protein ... -The major component of microfilaments ... is important in many cell processes, including amoeboid movement and attachment of cells to surfaces. -In most cells ... is is functionally associated with the contractile protein ... -... and ... are most highly organized in muscle fibers

spongy bone

Interior to the thin shell of compact bone is a filling of ... that provides mechanical strength. -consists of a network of thin strands of bone. -Its spaces are filled with bone marrow.

skeletal system

In addition to having an epithelial covering, many animals are protected by a .... that forms the framework of the body. -also functions in locomotion -transmit mechanical forces generated by muscle contraction and -transform them into the variety of motions that animals make. -Most invertebrates have HYDROSTATIC SKELETONS or EXOSKELETONS. echinoderms are an exception. These invertebrates have an endoskeleton consisting of calcium carbonate plates and spines. -Vertebrates have ENDOSKELETONS of cartilage or bone.

metaphysis

In children a disc of cartilage, the ... lies between the epiphyses and the diaphysis -are growth centers that disappear at maturity, becoming vague epiphyseal lines

humans

In humans most muscles have a mixture of different types of fibers. -The proportions of the types of fibers vary among individuals and from muscle to muscle in the same person. -Aerobic exercise, such as jogging or bicycling, increases endurance. -AEROBIC TRAINING: increases capillary density, the number of mitochondria, and the myoglobin content of muscle fibers. -STRENGTH TRAINING: for example, weight lifting— specific muscles are repeatedly contracted under heavy loads. -This action increases the number of filaments in the muscle fibers, which increases the size of the muscle.

bone marrow

Long bones have a central cavity that contains ... -Yellow marrow consists mainly of a fatty connective tissue -red marrow in certain bones produces blood cells

freely movable joints

Most joints are ... -Each is enclosed by a joint capsule of connective tissue and lined with a membrane that secretes a lubricant called SYNOVIAL FLUID. -This viscous fluid reduces friction during movement and absorbs shock.

tendons

Skeletal muscles produce movements by pulling on ..., tough cords of connective tissue that anchor muscles to bone. -... then pull on bones -Skeletal muscles, or their ... pass across a joint and are attached to the bones on each side of the joint. -When the muscle contracts, it pulls one bone toward or away from the bone with which it articulates.

diaphysis/epiphysis

The main shaft of a long bone is its ... and each expanded end is an ... 2 different words

osteoarthritis

a group of common joint disorders, cartilage repair does not keep up with degeneration, and the articular cartilage wears out. -Inflammation of the joint capsule may occur, and bone outgrowths, or spurs, may develop

compact bone

The radius has a thin outer shell of ... which is very dense and hard. -lies primarily near the surfaces of a bone, where it provides great strength. -consists of interlocking spindle- shaped units called OSTEONS. -Within an osteon, OSTEOCYTES (bone cells) lie in small cavities called LACUNAE -The lacunae are arranged in concentric circles around central HAVERSIAN CANALS. Blood vessels that nourish the bone tissue pass through the Haversian canals. -Osteocytes are connected by threadlike extensions of their cytoplasm that extend through narrow channels (called canaliculi)

vertebrate skeleton

The two main divisions of the ... are the axial and appendicular skeleton

subcutaneous tissue

This tissue consists mainly of adipose tissue that insulates the body from outside temperature extremes

myoglobin

a red pigment similar to hemoglobin, which stores oxygen in red blood cells -enhances rapid diffusion of oxygen from blood into muscles during strenuous muscle exertion

rheumatoid arthritis

an autoimmune disease, the synovial membrane thickens and becomes inflamed. -Synovial fluid accumulates, causing pressure, pain, stiffness, and progressive deformity, leading to loss of function.

pectoral gridle

consists of 2 collarbones, or clavicles, and 2 shoulder blades, or scapulas. -consists of a pair of large bones, each composed of 3 fused hip bones. -pelvic girdle is securely fused to the vertebral column, the ... is loosely and flexibly attached to it by muscles.

appendicular skeleton

consists of the bones of the limbs (arms and legs) plus the bones making up the girdles that connect the limbs to the axial skeleton, the pectoral (shoulder) girdle, and most of the pelvic (hip) girdle.

Epithelial tissue

covers all external and internal surfaces of the animal body. -structure and functions of the external ... covering are adapted to the animal's environment and lifestyle. -in both invertebrates and vertebrates, ... coverings protect the body. -may also be specialized for secretion, gas exchange, or temperature regulation and typically contain receptors that receive sensory signals from the environment.

axial skeleton

located along the central axis of the body, consists of the skull, vertebral column, ribs, and sternum (breastbone).