Protection, Support, and Movement-Skin, Skeleton, and Muscle Notes

Transcription

1 I. Movement in animals A. Basics: 1. different modes of transportation (running, flying, swimming) have evolved with adaptations for animals to overcome difficulties associated with each type of locomotion a. ex: swimming i. must overcome resistance ii. therefore, fusiform body shape b. walking/running animal i. must support against gravity ii. must overcome inertia c. flying i. must overcome gravity to become airborne 2. at cellular level, all movement are based on contraction of muscle cells by microfilaments and microtubules B. Skeletons 1. functions: a. maintain shape; give structure and support b. protect soft body tissues c. provide firm attachment (leverage) against which muscles can work during movement d. humans-mineral mineral storehouse, production of blood cells 2. Types: a. hydrostatic skeleton i. fluid under pressure in closed body compartment ii. move by using muscles to change shape of fluid filled compartments iii. ex: e cnidarians, flatworms, nematodes, and annelids iv. no protection could could not support a large land animal b. exoskeleton i. hard encasement deposited on surface of an animal ii. mollusks CaCO 3 arthropods chitin chitin secreted by endodermis iii. exoskeleton must be shed (molted) as animal grows

2 c. endoskeleton i. hard supporting skeleton buried within soft tissue of an animal ii. ex: sponges inorganic materials or protein fibers iii. ex: chordates cartilage cartilage and/or bone skeletons divided into several areas a. support and act as levers when their muscles contract II. Muscle Movements Animal movement is based on contraction of muscles working against some kind of skeleton Muscles contract actively, only extend passively therefore, to move body part in opposite directions, the muscles must be attached in antagonistic pairs flexor and extensor A. Structure and Function of Vertebrate Skeletal Muscle 1. muscle bundle of long fibers running the length of the muscle; attached to and responsible for the movement of bones 2. muscle cells=muscle fibers 3. fibers are multinucleate one cell with many nuclei 4. inside each muscle fiber, you find many smaller myofibrils arranged longitudinally 2 kinds of myofilaments in each myofibril a. thin filaments i. two strands of actin and one strand of a regulatory protein arranged in a double helix ii. troponin and tropomyosin molecules cover special bonding sites along the length of molecule b. thick filaments i. bunches of filamentous protein, myosin found between thin filaments ii. thick heads 5. sarcolemma plasma membrane of muscle fiber a. invaginated by transverse (T) tubules that permeate through cell

3 6. sarcoplasm coplasm cytoplasm cytoplasm 7. sarcoplasmic reticulum a. specialized ER b. specialized for Ca + storage-necessary during muscle movement 8. arrangement of thin and thick filaments Put drawing of sarcomere below B. Molecular Mechanism of Muscle Contraction Put more detailed drawing of sarcomere below

4 1. theory of muscle contraction sliding filament model (1950s) a. muscles contract when filaments slide past each other b. happens because of the generation of an action potential (electrical impulse) 2. molecular process: motor neuron connected to muscle fiber receives a message for contraction of that fiber releases acetylcholine (neurotransmitter) across neuromuscular junction binds with receptors on the muscle fiber, causing a depolarization along its sarcolemma if depolarization is sufficient, an action potential will be generated travels to T tubules (neuron-like) which release IP 3 (inositol triphosphate) which diffuses into SR IP 3 causes SR to release stored Ca + Note: structure of actin filaments Therefore, no muscle movement

5 Ca + from SR binds to troponin an ATP molecule is bound to myosin head while muscle is at rest Ca+ bonded to troponin causes the protein to change shape exposes the myosin binding sites on actin filaments ATP ADP ADP + P i, which phosphorylates the myosin head activated myosin bonds to exposed sites on actin forming a cross bridge ADP + P i are released sliding action results: myosin pulls actin filaments closer together-bringing Z lines closer (this is muscle contraction) *muscle contraction will not continue without the presence of ATP* ATP binds to t myosin head, causing filaments to unbind if Ca + is still present, myosin head will bind to next binding site and continue contraction *ATP is necessary for release of myosin head from actin filament; without it, muscle remains contracted shown in rigor r mortis no more ATP to release myosin heads, therefore, no further movement After contraction, muscle fibers return back to their resting place 1. acetylcholine is inactivated by enzyme acetylcholinesterase 2. Ca + are pumped (using ATP) back into SR by active transport Even when not moving, muscles retain a state of partial contraction muscle tone 1. stimulated by nerve cells 2. muscle tone is unconscious 3. prepare for action 4. only way to completely relax a muscle is to cut motor neuron

6 C. Movements ents in other types of muscle: 1. Cardiac muscle a. heart b. striated appearance appearance caused by filaments c. highly branched d. can generate own action potentials (pacemakers) spreads spreads rapidly as electrical signals cross cells at gap junctions (spaces between cells) not neuron-generated signal 2. Smooth muscle a. lack striations b. less myosin c. does not have T tubule system or well developed SR d. therefore, contractions are relatively slow with a greater range of control e. appropriate for function D. Energy supply in muscles: 1. initially ATP molecules in cells used up very quickly 2. creatine phosphate a. used after ATP runs out b. stored in muscle cells c. can be converted to ATP as needed d. also runs r out quickly during vigorous exercise 3. glycogen stored in muscle cells a. stores glucose b. glycogen is degraded, releasing glucose c. broken down during respiration for energy d. can only happen in sufficient oxygen 4. strenuous exercise; circulatory system cannot deliver enough oxygen a. result oxygen debt b. muscle fibers respire anaerobically, producing lactic acid III. Skin A. Epidermis-outer layer 1. Several strata

7 a. stratum basale-deepest deepest,, next to t dermis b. stratum corneum-superficial superficial-sloughed sloughed off i. pigment cells produce melanin-gives skin color ii. keratin-protein that gives skin strength/flexibility; insoluble B. Dermis-beneath the epidermis 1. dense, fibrous connective tissue; collagen 2. sweat glands, hair follicles, blood vessels, sensory receptors (Pacinian corpuscle)-touch, pain, temperature, sebaceous glands-sebum, sebum, melanocytes, erector pili muscles (goosebumps) C. subcutaneous tissue 1. skin rests on this 2. composed of adipose tissue-insulation insulation