UNC-Chapel Hill EXSS 276 - EXAM 4 STUDY GUIDE (15 pages)

EXAM 4 STUDY GUIDE Chapter 10 Muscle Tissue Skeletal Muscle Muscle Facts 40 50 of body weight is muscle muscle gain is 2 times faster than muscle loss smallest muscles are in ear holding it ear drum together largest muscle gluteus maximus keeps us upright strongest muscles glutes massester tongue muscles can only pull no pushing it contracts shortens born with all muscle fibres you will ever have skeletal muscle contractions are voluntary except when cold somatic skeletal voluntary heart muscle never gets tired 3billion beats in lifetime Somatic Motor Neuron Includes both sensory to CNS and motor neuron to skeletal muscle Neurons that stimulate skeletal muscle fibers Produce both reflexive and voluntary movements ACh Only one pathway Effect of motor neuron is always excitation Communication between motor neuron and a muscle fiber occurs at synapse If motor neurons cease to stimulate a muscle paralyzed limp muscle that has no muscle tone Types of Muscles Skeletal muscle tissue Striated Multinucleated Voluntary Because it can be made to contract or relax by conscious control Cardiac Striated Uninucleated Involuntary Heart wall pumps blood to all parts of body Natural pacemaker that initiates each contraction authorhythmicity Smooth Nonstriated Uninucleated Involuntary Located in the walls of hollow internal structures Blood vessels airways and most organs in abdominopelvic cavity Function motion Muscle Function 1 Produce body movements 2 Stabilizing body positions 3 Storing and moving substances within the body a Sphincters smooth muscle help prevent the outflow of the contents of a hollow organ ex temporary storage of food in the stomach or urine in the urinary bladder b Cardiac muscle contractions of the heart pump blood through blood vessels of the body c Smooth muscle contractions also move food and substances i Bile and enzymes through the GI tract push gametes sperm and oocytes through the passageways of the reproductive system and propel urine through the urinary system 4 Generating heat a Thermogenesis producing heat b Heat used to maintain normal body temperature c Involuntary contractions of skeletal muscles shivering can increase rate of heat production Properties of Muscular tissue o Electrical excitability Ability to respond to certain stimuli by producing electrical signals action potential impulses Two stimuli triggers Electrical stimuli autorhythmic hearts pacemaker Chemical stimuli neurotransmitter released by neurons hormones distributed by the blood and local pH changes o Contractility Ability of muscular tissue to contract forcefully when stimulated by an action potential Produce force by attempting to change shape Shortening vs lengthening o Extensibility Ability of muscular tissue to stretch within limits without being damaged Smooth muscle has greatest amount of stretching o Elasticity Ability of muscular tissue to return to its original length and shape after contraction or extension Skeletal Muscle Hierarchy Skeletal muscle muscle belly fascicles Tendon and bone Fascicles o Bundles of muscle fiber wrapped in perimysium Fascicles muscle fibre cell Capillaries and nerves Within muscle fibre myofibrils Contain sarcomere thick and thin filaments Sarcolemma plasma membrane of muscle cell Sarcoplasm the cytoplasm of a muscle fiber Sarcomere o Basic functional units of a myofibril o Made up by z disc o Actin attaches to sarcomere o M line is anchor for myosin Muscle Proteins o Contractile Proteins Myosin Actin o Regulatory Proteins o Structural Proteins Thick Filament o Myosin is the main component Functions as a motor protein in all 3 types of muscle tissue Binds to actin o Thick filament apart of A band A band overlap o Myosin molecule consist of a tail and two myosin heads o Tails meet at M line Thin Filament o Anchored to Z discs o Actin is main component each molecule is a myosin binding site where a myosin head can attach binds to myosin o Thin filament apart of I band I band no overlap o consist of regulatory proteins troponin protein that moves tropomyosin away from actin so it can bind to myosin has bind site for Ca2 ions tropomyosin when skeletal muscle is relaxed it covers myosinbinding sites on actin molecules thereby preventing myosin from binding to actin Contraction Cycle driven by ATP o ATP hydrolysis myosin reoriented Myosin heads hydrolize ATP and become reoriented and energized o Attachment of myosin to actin to form cross bridges Myosin binds to actin o Power stroke Myosin cross bridges rotate toward center of sarcomere o Detachment of myosin from actin relaxation As myosin heads bind to ATP cross bridges detach from actin Sliding Filament o Actin and myosin sliding past each other o Thin filaments move toward the M line of each sarcomere Rigor Mortis o Muscles locked in contraction o Begins 3 4 hours after death Lasts about 24 hours o Ca2 ions leak out of the SR into the sarcoplasm and allow myosin heads to bind to actin ATP synthesis ceases shortly after breathing stops Cross bridges cannot detach from actin Neuromuscular Junction NMJ o the synapse between a somatic neuron and a skeletal muscle fiber o muscle action potential arise here o voltage gated channels open ACh neurotransmitter is released and goes across the synaptic cleft small gap Ach binds to Ach receptor on the motor end plate muscle fiber part of NMJ Receptor opens channel Targets are ligand gated channels opens and Na goes into muscle excitatory period Flow of Na in makes inside more positively charged triggers action potential Causes sarcoplasmic reticulum to release its stored Ca2 into the sarcoplasm muscle fiber contraction ACh lasts briefly bc it is broken down rapidly by acetylcholinesterase AChE Breaks into acetyl and choline products cannot activate the ACh receptor o Synaptic end bulbs the neural part of the NMJ AP Transmission o Motor neuron innervates surface fibers May innervate lots of muscle fibers o Firing in unison allows AP to get deeper into fibre Transverse Tubules o Tiny invaginations of the sarcolemma Tunnel in from the surface toward the center of the fiber o Allow AP to travel and excite all parts of the muscle fiber at the same time To get action potential to fibers inside the muscle Muscle fiber contracts simultaneously o Activates sarcoplasmic reticulum stores and releases Ca Initiates contraction cycle Excitation Contraction Coupling o From the start of action potential all the way down to muscle fiber o The steps that connect excitation a muscle