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67 Cards in this Set
- Front
- Back
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Electrical excitability
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The ability of the muscle to respond to certain stimuli(or irratibility), by producing signals called action potentials
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Contractility
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The ability of a muscle to contract forcefully when stimulated by an action potential
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Extensibility
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The ability of a muscle to be extended (or stretched) without any damage
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Elasticity
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The ability of the muscle to return to it’s original length and shape after extension or contraction
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Body movement
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Requires coordinated functioning of the muscles, bone and joints
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Storing substances within the body
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Substances are able to be stored within an organ due to the contraction of sphincters that stop substances from leaving the organ
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Moving substances within the body
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Cardiac muscles pump blood through blood vessels. Smooth muscle tissue controls the movement of substances through many organs eg digestive, reproductive and urinary systems. Contraction of skeletal muscle also helps transport blood and lymph in the vessels that transport them
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Stabilising body positions
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Skeletal muscle contractions stabilise joints and maintain body posture and position. Postural muscles are important for maintaining body position while we are awake
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Heat production
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The contraction of muscle produces heat(thermogenesis)This is why we shiver. Heat is vital in maintaining body temperature
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Types of Muscular Tissue
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Skeletal Muscle-Striated/voluntary, Cardiac Muscle-Striated/Involuntary, Smooth Muscle-Nonstriated/Involuntary
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Function of Muscular Tissue
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Producing Body Movements, Stabilizing Body Positions, storing substances within the body, Moving Substances within the Body, Producing Heat
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Skeletal Muscle Tissue
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-Attached to Bones and moving parts of the skeleton-Striated/Voluntary. Each muscle is an individual organ(as it contains more than one type of tissue), and consists of hundreds to thousands of muscle cells(called muscle fibres). In addition to muscle fibres each skeletal muscle contains connective tissue that surrounds each fibre, and the whole muscle, and also blood and nerve tissue.
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Superficial fascia
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Fascia (refers to sheets or broad bands)-fibrous connective tissue that lay deep to the skin, supports and surround muscles and other body organs. It seperates the skin from underlying muscles, and is a combination or areolar connective tissue and adipose tissue. Acts as a pathway for nerves, blood and lymphatic vessels, that are entering and leaving the muscles
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Deep fascia
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Made of dense irregular connective tissue that holds adjacent muscles with similar functions together. It allowsmuscles to move freely, carries nerves, blood and lymphatic vessels, and fills the spaces between muscles
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Cardiac Muscle Tissue
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Found only in the heart, Striated/Involuntary
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Smooth Muscle Tissue
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-Located in the walls of hollow internal structures such as blood vessels, airways, the stomach, and the intestines.-Nonstriated/Involuntary
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Connective Tissue Components
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Epimysium,Perimysium,Endomysium. (These 3 form tendons and attach to bones)
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Muscle Fibers
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Each skeletal muscle is a seperate organ composed of hundreds to thousands of cells, which are called Muscle Fibers
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Epimysium
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The entire muscle is wrapped in Epimysium(outermost layer), made of dense irregular connective tissue
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Perimysium
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Surrounds bundles of 10-100 or more muscle fibers called fascicles(middle layer)Also made of dense irregular connective tissue.
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Fascicles
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A small bundle of muscle fibers, responsible for the muscle’s appearance of ‘grain’ in meat
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Endomysium
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Endomysium wraps each individual muscle fiber, the deepest layer of connective tissue. Contains a thin sheath of areolar connective tissue, and separates individual muscle fibres form each other
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Tendons
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Are cords of dense regular connective tissues that attach muscles to the periosteum of the bones
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Aponeurosis
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Is the name of a tendon that extends as a flat, broad layer, rather than cord like structure of a regular tendon.
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Muscle fibres
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The cells that make up muscle tissue are known as muscle fibres due to their elongated appearance. It has a cell membrane, organelles and other cellular components.
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Sarcolemma
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Each muscle fiber is covered by a plasma membrane called a sarcolemma, tiny tubes extend from the sarcolemma and tunnel into the centre of the cell, these are called t-tubules
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Transverse Tubules(T tubules)
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tunnel in from the surface toward the center of each muscle fiber.
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Sarcoplasm
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The muscle fibers cytoplasm, contains a large amount of glucose(can be broken down to release energy), and a red protein called myoglobin(that holds oxygen in the muscle fibre), which is only found in muscle cells
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Mitochondria in muscles
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AS muscles have high requirements for energy, muscle fibres contain large amounts of mitochondria, which are found in rows along the fibre
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Nuclei in muscles
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Due to their length muscle fibres cantain many nuclei, compared to most cells which have one nucleus
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Sarcoplasmic Reticulum
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a network of fluid-filled, membrane-enclosed tubules that store calcium ions required for muscle contraction, they wrap around each mybrofil, arranged so that it touches the t-tubules.
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Myoglobin
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1) a reddish pigment, similar to hemoglobin in the blood 2) an oxygen-binding protein found only in muscle fibers
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Myofibrils
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cylindrical structures that extend along the entire length of the muscle fibers, the contractile components of the muscle, which line up and gives the muscle it’s striated appearance under a microscope
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2 types of myofibrils
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thin filaments & thick filaments. There are twon thin filaments for every thick filament, they lie along side each other and overlap. Each filament is very short, and doesn’t extend the entire length of the myofibril, instead they are arranged into shorter compartments called sarcomeres
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Filaments or myofilaments
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Composed of protein arranged in the myofibril in such a way that it gives it a striated appearance
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Myofibrils proteins
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Contractile protein-facilitate contraction, regulatory proteins-that determine when contraction can and cannot occur, Structural proteins-that hold the thick and thin filaments int he right position, and give the myofibril elasticity and extensibilty
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Sarcomere
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a contractile unit in a striated muscle fiber (cell) extending from one Z disc to the next Z disc. Lined up end to end and are the basic functional units of myofibrils
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Actin
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A contractile protein that is part of the thin filaments in muscle fibers. Looks like an olive, arranged in a line along a twisted regulatory protein. Each one has a myosin binding site on it’s surface, where myosin head attach during muscle contraction. As well as actin it also contains two kinds of regulatory proteins
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Myosin
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Found in the thick filaments, the proteins look like golf clubs. Each thick filament contains many myosin molecules that are arranged so that the myosin head sticks out in all directions
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Regulatory proteins of the thin filament
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Troponin and tropomyosin
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Tropomyosin
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Covers the binding site to stop the myosin heads from attaching when the muscle is not contracting
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Troponin
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Holds the tropomyosin in place
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Muscular Atrophy
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a wasting away of muscle
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Muscular Hypertrophy
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an increase of muscle fiber diameter owing to the production of more myofibrils, mitochondria, etc...
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Muscle Action Potential
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an electrical signal sent to a skeletal muscle so it can contract
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Motor Neuron
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The neuron that delivers a muscle action potential
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Motor Unit
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A single muscle neuron along with all the muscle fibers it stimulates
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Motor End Plate
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The region of the sarcolemma near the axon terminal
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Synaptic Cleft
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The space between the axon terminal and sarcolemma
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Neuromuscular Junction
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The synapse formed between the axon terminals of a motor neuron and the motor end plate of a muscle fiber
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A motor neuron excites a skeletal muscle in the following way.....
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1. Release of acetylcholine2. Activations of ACh receptors3. Generation of muscle action potential4. Breakdown of ACh
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Acetylcholinesterase
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enzyme that breaks down the neurotransmitter
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Contraction Cycle
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the repeating sequence of events that causes a filament to slide
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4 steps of the contraction cycle
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1. Splitting ATP 2. Forming Crossbridges 3. Power Strokes 4. Binding ATP and detaching
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Onset of contraction cycle
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Sacroplasmic reticulum releases calcium ions into the cytosol, where they bind to troponin. The troponin then moves the tropomyosin away from the myosin binding sites on actin. Once they are free the contraction process can begin
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Silding filament mechanism-Splitting atp(hydrolysis)step 1
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The myosin head has an ATP-binding site and an ATPase(enzyme which hydrolyzes atp to adp) and a phosphate group. This hydrolysis reaction reorients and energises the myosin head
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Sliding filament mechanism-forming crossbridges step 2
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The newly energised myosin head attaches to the myosin binding site on actin and released previous the hydrolysed phosphate group. This is called the crossbridge.
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Sliding filament mechanism-Power stroke step 3
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After crossbridges form, the power stroke occurs. During the powerstroke the site where adp is still bound opens. The crossbridge then rotates and releases the ADP. The force it generates as it rotates slids the thin filament towards the M line
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Sliding filament mechanism-Binding and detaching
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After the power stroke, the crossbridge stay firmly attached to actin until it binds another molecule of ATP. As the ATP binds to the ATP-binding site the myosin head detaches from the actin.
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Sliding filament mechanism
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During muscle contraction thick filaments grab onto thin filaments and pull itself across towards the centre of the sacromere, shortening the sarcomere, overlapping the filaments.
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Muscle Tone
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A sustained, partial contraction of portions of the skeletal or smooth muscle
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Flaccid
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A state of limpness in which muscle tone is lost
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Creatine Phosphate
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Energy rich molecule that is unique to muscle fibers
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Glycolysis
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a series of cytosolic reactions that produces 2 ATP's by breaking down a glucose molecule to pyruvic acid
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Anarobic Cellular Respiration
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The process that occurs when oxygen levels are low as a result of vigorous muscle activity, most of the pyruvic acid is converted to lactic acid
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Aerobic cellular respiration
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a series of oxygen requiring reactions that produce ATP in mitochondria
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Muscle Fatigue
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The inability of a muscle to contract forcefully after prolonged activity
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