Bio 161 Midterm Exam 4 2025

(pre week 10) Muscle fiber - -an individual muscle cell Fascicle - -group of muscle cells within the belly of a muscle Sarcolemma - -plasma membrane of a skeletal muscle cells Sarcoplasm - -cytoplasm of skeletal muscle cell Sarcomere - -Contractile unit of muscle cell that makes a myofibril Sarcoplasmic reticulum - -modified endoplasmic reticulum that regulates calcium in the cell T (transverse) tubules - -tubes continuous with the sarcolemma that convey electrical current to the interior of the cell Myofibril - -the major protein component of a muscle cell, made up of myofilaments Myoglobin - -oxygen-binding protein in a muscle cell Multi-nucleate - -containing many nuclei Epimysium - -fibrous connective tissue that is continuous with the tendon What type of muscle cell is striated? Skeletal, cardiac, smooth - -skeletal, cardiac Skeletal muscle cells tend to contain short, branched cells. True or false - -false, skeletal muscles contain very long and cylindrical (lecture 14 muscular structure) Excitable - -respond to chemicals released from motor neurons Conductive - -ability to propagate electrical signals over membrane Contractile - -ability to shorten and generate force Extensible - -ability to be stretched without damaging the tissue Elastic - -ability to return to original shape after being stretched BIO 161 BIO 161 BIO 161 What characteristics. Do neurons and muscle cells share? - -excitability- response to chemicals release from motor neurons Skeletal muscle - -voluntary, striated, multinucleate, attached to bone/fascia (connective tissue) Cardiac muscle - -Involuntary muscle tissue found only in the heart, striated, mononuclear, autorhytmic (cells can self regulate contraction) Smooth muscle - -Involuntary muscle found inside many internal organs of the body, non-striated, mononuclear, hair follicles, walls of hollow organs Tendon connection - -muscle to bone, collagen fibers of epimysium form strong fibrous tendon (dense regular C.T) merges into periosteum (outer bone) most common connection, biceps brachii, calf muscles Aponeurosis connection - -some muscles do not insert directly into bone, insert to broad sheet of C.T similar to tendon but broad and flat, ex. Abdominal muscles Fascicle - -group of muscle cells (fibers) Muscle cell (fiber) - -filled with long bundles of proteins (myofibrils) Myofibrils - -2 types of proteins (my-filaments actin and myosin) Myofilaments - -The contractile proteins, actin and myosin, of muscle cells, organized into sarcomeres What does connective tissue do for muscle cells? - -protects, reduces friction, space for fluid Epimysium - -covers the entire skeletal muscle, continuous with tendon, reduces friction Perimysium - -Connective tissue surrounding a fascicle Endomysium - -Surrounds individual muscle fibers, areolar tissue provides space for ECF and ion needed to excite muscle cells Parallel muscle shape - -Spindle-shaped, fibers run parallel, most skeletal muscles, rectus abdominal Fusiform muscle shape - -biceps brachii, all muscle belly fibers parallel each other Circular muscle shape - -Muscle fibers are arranged in a circular manner, oribuclaris oculi BIO 161 BIO 161 Pennate Muscle Shape - -Muscles have a feather-like appearance. Can be unipennate, bipennate, or multipennate, allows high force, fascicles attach slant position, deltoid Convergent Muscle Shape - -ex. Pectoralis major, origin wider than insertion, force Sarcolemma - -muscle cell membrane Sarcoplasm - -cytoplasm of a muscle cell, inside includes myofibrils (long bundles of proteins), myoglobin- stores oxygen for us, glycogen- polymer of starch Transverse tubules (T-tubules) - -sarcolemma has tube like structures that penetrate interior of the cell Which of the following structures is the largest? My-filament, myofibril, muscle cell, fascicle - -fascicle Sarcoplasmic reticulum (SR) - -smooth ER that forms a network around each myofibril Terminal cisternae - -sacs of the SR, closely associate with T-Tubules, storage area for calcium ions Myosin protein - -thick filaments, single myosin shaped like gold club (head mobile extend and flex) consists of 100's of myosin proteins bind and hydrolyzes ATP, release of energy allows head to change shape and force Actin protein - -thin filaments polymer of actin, w troponin and tropomyosin accessory proteins, each actin monomer has an active site that can bind to head of myosin protein Sarcomere - -Contractile unit of muscle, myosin and actin, organization of proteins Tropomyosin - -blocks active sites on actin in relaxed muscles Troponin - -binds to and regulates tropomyosin, with calcium troponin moves tropomyosin off actin sites What proteins is not part of thin filament? - -myosin A band - -dark area; extends length of the thick filaments, overlap with thin filament H band - -thick filaments only, lighter in color I Band - -thin filaments only, light Z disc - -edge of sarcomeres M line - -middle of sarcomere BIO 161 BIO 161 Sliding filament theory - -theory that actin filaments slide toward each other during muscle contraction, while the myosin filaments are still, uses ATP hydrolysis, H-Band decreases, I band decreases, contraction of many sarcomeres= whole muscle contraction What region of a sarcomere lacks myosin? - -I Band Which of the following regions will not change size during a contraction? - -A band- complete length of thick, thick slides along thin (pre week 11) The neuromuscular junction (or synapse) involves which of the following two cell types? - -neuron: skeletal muscle Which of the following neurotransmitters is released at the neuromuscular junction? - acetylcholine What type of channels does acetylcholine bind to in the post-synaptic (muscle cell) membrane? - -chemically (ligand gated), Ach pr