Muscular System Overview Worksheet

Muscular System Worksheet 3 types of muscle tissue: -skeletal -cardiac -smooth skeletal tissue -Cylindrical cells Striated -Multiple, peripheral nuclei -Voluntary -Attached to skeleton cardiac muscle -Branching cells -Striated -One or two central nuclei -Involuntary -Heart smooth muscle -spindle-shaped cells -non-striated -single, central nucleus -involuntary -located in the walls of hollow organs Muscles that move bones are called ____________________ because they are under conscious control; all other muscle tissue is called ____________________because it cannot be consciously controlled. voluntary; involuntary The connective tissue around each muscle fiber is the ____________________; the layer around each fascicle is the ____________________, and the layer around the whole muscle is the ____________________. endomysium; perimysium; epimysium endomysium -wispy layer of areolar connective tissue that encloses each muscle fiber -insulates perimysium a sheath of connective tissue that groups muscle fibers into bundles (anywhere between 10 and 100 or more) or fascicles epimysium the fibrous tissue envelope that surrounds skeletal muscle. covers the entire muscle and protects muscles from friction against other muscles and bones. fascia (dense connective tissue sheet) - supports and surrounds muscles and other organs -unites muscles with similar functions -allows free movement of muscles -carries nerves and vessels -fills spaces between muscles A ____________________connects muscle to bone. All types of muscle tissue produce movement; skeletal muscle also maintains ____________________ and stabilizes ____________________. tendon; posture; joints tendons cordlike bundles of collagen fibers Aponeuroses sheetlike arrangement of collagen fibers functions of skeletal muscle -Produces voluntary movement -Stabilizes joints -Maintains posture -Generates body heat Examples of voluntary movement Locomotion; manipulation; assists in breathing, eating, speech, support of organs; with nervous system, generates reflexes; provides facial expressions sarcolemma -The plasma membrane of muscle fiber (muscle cells). -acts as a barrier between the extracellular and intracellular compartments, defining the individual muscle fiber from its surroundings. 1/4 Inside are contractile organelles with alternating A and I bands called ______________ that make the cell look striated. The contractile units of these organelles are called ____________________. sarcomere; myofibrils The thread-like proteins that cause contraction are the thick, or ______________ myofilaments and the thin, or ____________ myofilaments. myosin; actin The ____________________ reticulum is specialized to store and release ____________________ ions to trigger contraction. sarcoplasmic; calcium One neuron and all the skeletal muscle cells it stimulates make up one __________ __________. motor unit The point of communication between the motor neuron and the muscle fiber is called the __________ ________ __________. Neuromuscular Junction (NMJ) The gap between the nerve ending and the muscle cell is the ____________________ ____________________. synaptic cleft When the nerve impulse reaches the nerve ending, the chemical (neurotransmitter) ____________________ is released. Acetylcholine (ACh) This chemical binds to receptors on the ___________ end plate and opens channels for __________ ions that flow ______________ (into/out of) the muscle fiber. motor; calcium; into As a result, __________________ions are released from the (SR) __________________ _________________. sodium; sarcoplasmic reticulum After calcium ions are released within the muscle fiber, they attach to _____________________ (troponin/tropomyosin) and _______________________ moves off of binding sites on actin. troponin; tropomyosin Once these binding sites are exposed, myosin heads attach forming ________________________. Then the myosin heads then ______________ (pull/push) the thin filaments (actin) towards the ____________ of the sarcomere. cross-bridges & pivot; pulls; center Then ATPase hydrolyzes (breaks down) ATP, causing the myosin head to _______________ from the actin. And the cycle repeats over and over. breaks This causes the ___-bands and ____-bands to shorten while the ____-bands stay the same length. I; H; A As all sarcomeres shorten in the myofibril, the muscle shortens resulting in _______________________. contraction Skeletal muscle relaxation requires ________________ to disconnect myosin head from binding sites on actin. ATP (energy) Muscle fiber individual muscle cells myofibril long contractile organelles (i.e. they lengthen or shorten) -inside sarcoplasm, extends entire length of muscle fiber -arrangement of filaments gives striated appearance. sarcomere basic functional unit of contraction within myofibrils (made of proteins) -Myofibrils extend the length of the muscle fiber -Thick and thin myofilaments in myofibril do not extend entire length of muscle fiber myofilaments the term for the chains of (primarily) actin and myosin that pack a muscle fiber. These are the force generating structures. myosin -molecule shaped like two twisted golf clubs with tail and heads -converts chemical energy in ATP into mechanical energy of motion (grabs ATP, rips it in half, takes the energy from the bond and uses it!) 2/4 Actin -thin myofilament component -has myosin-binding site for myosin head -this site is covered, and only calcium can makeit uncover. -basically just sits n waits for myosin to bind on to it Motor Neuron -Neurons that stimulate skeletal muscle fibers to contract. -each motor neuron has a threadlike axon that extends from the brain or spinal cord to a group of skeletal muscle fibers. Motor Unit a motor neuron together with the muscle fibers on which it acts. action potential -the brief (about one-thousandth of a second) reversal of electric polarization of the membrane of a nerve cell (neuron) or muscle cell. -produces the nerve impulse, and in the muscle cell it produces the contraction required for all movement. Neuromuscular joint point of communication between the motor neuron and the muscle fiber Synaptic cleft gap between the nerve ending and the muscle cell Acetylcholine (Ach) the neurotransmitter released at the NMJ Sarcoplasmic Reticulum smooth ER, stores calcium -fluid-filled, membranous organelle similar to smooth ER of non-muscle cells -wraps around each myofibril (looks like a web) -dilated end sacs are terminal cisterns, associated with either side of a T-tuble to form a triad -stores and releases calcium ions (Ca2+) that trigger muscle contraction (i.e. when calcium is needed for contractions, it lets it out) synapse a region where communication occurs between aneuron and another cell such as a skeletal muscle fiber. Atrophy muscles get smaller hypertrophy enlargement of existing muscle fibers hyperplasia increase in number of muscle fibers from satellite cells (happens a lot as a kid) fibrosis replacement of damanged skeletal muscle fibers with fibrous scar tissue instead of satellite cells. adhesions = example of fibrosis Transverse Tubules (T-Tubles) -many invaginated, tunnel-like extensions of sarcolemma -open to cell's exterior thus filled with interstitial fluid -muscle action potentials travel along the sarcolemma and thru the T-Tubules and quickly spread throughout the muscle fiber. z disc or z line dense protein material that separates one sarcomere from next in myofibril prime mover Muscle primarily responsible for an action. origin less movable attachment insertion more movable attachment action What the muscle "does" -Moves insertion toward origin -The "movement" produced Flexion decreases angle between bones Extension increases angle between bones Rotation movement around an axis Abduction moves appendage away from midline 3/4 Adduction moves appendage toward midline Circumduction moves appendage in a circle around joint Antagonist Muscle(s) that resist prime mover, or move opposite to it Synergist Muscle(s) that assist(s) prime mover Fixator Stabilize origin of prime mover or hold the bone still so all tension is used to move insertion Muscle attachments Origin and/or insertion (e.g. sternocleidomastoid) Muscle action Adductor magnus Direction of muscle fibers Rectus abdominis Location of muscle Temporalis Size of muscle Gluteus maximus Number of origins/heads Biceps brachii Shape of muscle Deltoid Graded response a response that varies directly with the strength of the stimulus. all-or-none-law -At threshold, a fiber will contract to its maximum extent -No "partial" contractions of individual fibers -Increasing stimulus strength has no additional effect Red Slow Fibers (Slow Oxidative) -Fewer myofibrils, -weaker -Requires oxygen to make ATP -Lots of myoglobin, mitochondria, capillaries -Contracts slowly; fatigues slowly -Recruited first Endurance white fast fibers -Most myofibrils, strongest & widest in diam. -Makes ATP without oxygen -Low myoglobin, fewer mitochondria & capillaries -High glycogen stores -Contracts rapidly, fatigues rapidly -Short-term powerful movements -Recruited last -May hypertrophy in response to training intermediate fibers -Intermediate diameter/number of myofibrils -Lots of myoglobin, mitochondria, capillaries -Can make some ATP without oxygen -Contracts rapidly, moderately resistant to fatigue -The second fiber type recruited -Walking, jogging, biking over short to moderate distances Exercise does not increase the number of skeletal muscle cells true Skeletal muscles have at least two attachments -One attachment is relatively immobile -The other attachment is more mobile 4/4