Muscular System Lecture 1 PDF

The Muscular System  What are we going to learn? Lecture List the 3 types of muscles and describe the Lab characteristics of each. Describe the microscopic anatomy of skeletal,...

The Muscular System  What are we going to learn? Lecture List the 3 types of muscles and describe the Lab characteristics of each. Describe the microscopic anatomy of skeletal, Microscopic smooth, and cardiac muscle cells. List the components of a neuromuscular junction and appearance of describe the function of each. different types of Describe the events that occur in muscle cells during muscle contraction and relaxation. muscle cells Describe the structure and function of tendons and aponeuroses Location on body and Describe the structure and function of bursae and tendon sheaths actions of important Define muscle origin and insertion using the gastrocnemius muscle and common calcanean tendon muscles (muscles of as examples. the head and neck, Differentiate between prime mover, antagonist, syngergist, and fixator muscles. abdomen, thoracic Describe cutaneous/twitch muscles – specifically the cutaneous trunci muscle. limb, pelvic limb, and Locate and know the function of the muscles of mastication. the muscles of Locate and know the function of the muscles of the respiration) abdominal wall and different ways surgeons enter the abdomen. Locate and know the function of the muscles of respiration. 4 characteristics of muscle cells Excitability Contractibility Extensibility Elasticity NOTE: they do not contract and/or elongate when signaled, they only contract when signaled, and relax when the signal is done 3 Types of muscle: skeletal, cardiac, smooth Commit to memory Table 8- 1  Types of muscle cells skeletal cardiac smooth Skeletal muscle functions Movement Posture Heat generation Skeletal muscle – the language Epimysium Perimysium Fascicles Muscle fibre (cell) Endomysium Organization of a skeletal muscle belly Skeletal Muscle fibres – the language muscle cell membrane = sarcolemma SER (sort of) = sarcoplasmic reticulum (blue) cytoplasm = sarcoplasm Transverse (T) tubules – extensions of sarcolemma, allow electrical signal to penetrate the muscle cell quickly mitochondrion = mitochondrion Myofibrils – contain the functional units Nuclei – lots – all just under sarcolemma – why?  Myofibrils – the language sarcomer e Z line actin (green) myosin (purple) Myofibrils – the language I band A band H band Z line thin filament thick filament sarcome re Coloured electron micrograph of a muscle fibre Why do they call them bands? Sarcomere shortening A Sarcomere Shortening B Sarcomere Shortening C - ATP to ADP Electron micrograph of contracted muscle fibre Closer look at actin and myosin Muscle Contraction 3D - YouTub Various videos for your How muscles contract enjoyment…. (6:40) More about m uscles to 5:30 only How muscles contract - Kha n Academy What starts the contraction? muscle receives a nerve impulse from a nerve motor unit = motor neuron and all the muscle fibres it signals fine motor control vs. gross control Motor end unit histology The Neuromuscular Junction End of nerve fibre (more about this in future module) meets muscle cell Signal comes down nerve causes release of neurotransmitter (communication chemical) acetylcholine (Ach) The Neuromuscular Junction Ach diffuses across the gap and attaches to receptors on sarcolemma Chain of events started in muscle cell Myasthenia gravis botulism What happens at the neuromuscular j atrophy unction (ignore step 2 for now) What starts the contraction? Signal received by muscle cell travels sarcolemma  T- tubules  SR SR releases stored Ca2+ Ca2+ diffuses into myofibrils  exposes binding sites on actin contraction as actin and myosin fibres move along one another ATP required to restock calcium ions into SR and reset heads on myosin Run out of ATP? Not enough calcium? Cow that calved ye sterday is down wit h" MIlk Fever" Hypocalcemia in a bitch Chemistry of muscle contraction ADP + P = ATP All-or-nothing Creatine principle phosphate Twitch contraction Glycogen 3 phases of Myoglobin contraction Aerobic metabolism Anaerobic metabolism Lactic acid Cardiac muscle Involuntary, striated heart only only one nucleus per cell (OK sometimes 2) smaller than skeletal muscle cells branched attached to each other at their ends – intercalated discs function as a unit – impulses spread as a wave Cardiac muscle cells contract without external signals groups of cells contract at rate of cell contracting with higher frequency more about the pacemaker in CVS rate can be adjusted by autonomic NS  Intercalated discs Intercellular junctions Desmosomes – anchor actin and stop cells from separating during contraction Gap junctions – action potential Smooth muscle non-striated involuntary sheets of muscle that line hollow organs (visceral smooth muscle) OR small groups of cells (iris of the eye, muscles that focus the lens, small airways, small blood vessels) Smooth Muscle Cells Spindle shaped A & M units Actin and myosin shorten to contract units criss-cross cell the cell One nucleus per Meet at dense cell bodies (like Z lines of skeletal muscles) Where do we find smooth muscle? How does food get churned up in the stomach? How does digesta travel along the intestine? How does urine exit the bladder? How do full term fetuses leave the uterus? Where do we find smooth muscle? How does the pupil dilate? How does the lens change shape to focus images? How do small airways in the lungs expand to let in more air?