Muscle

8- Compare and contrast smooth, cardiac, skeletal muscle with regards the following:

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7- Name the primary germ layer from which muscle tissue is formed

Mesoderm

1-State the major functions of the muscular system:

a- Motion b- movement of substances through the body c- stabilizing body position - regulating organ volume d- thermogenesis

Distinguish between origin, insertion, and action of a muscle

a- ORIGIN: attachment of a muscle tendon to a stationary bone or the end opposite the insertion b- INSERTION: attachment of a muscle tendon to a movable bone or the end opposite the origin b- ACTION: type of movement caused by the contraction of the muscle

22- Define twitch contraction and be able to label and explain the three phases on a myogram:

a- latent period b- contraction period c- relaxation period

26-Define and explain the importance of muscle tone

Is term applied to weak muscle contractions of a skeletal muscle at rest - keeps muscle firm but does not cause contractions i.e., muscle at back of neck keeps head upright ( unconsciously ) so that no effort needed to keep head from slumping down to chest

25-Define and explain the significance of motor unit recruitment

Is the process by which the number of active motor units increases - all are not functioning at the same time - while some contract, others relax - weakest units are recruited first; stronger ones added as need for force increases - delays fatigue and also produces smooth movements rather than jerky ones

5- Identify major muscles in the human body

Sternnocleidomastoid: orginates on sternum and clavicle and inserts on masstoid process of temporal bone g- action: principle action of the muscle 1- flexor ( decreases angle of joint ): flexor carpi-radialis 2- extensor ( incrases angle of joint ): extensor carpi-radialis 3- abductor ( moves bone away from midline ): abductor pollicus longus 4- adductor ( moves bone towards midline ): adductor longus 5- levator ( produces an upward movement ): levator scapuli 6- depressor ( produces a downward movement ): depressor labii inferioris 7- supinator ( turns palm upward or anteriorly ): supinator 8- pronator ( turns palm downward or posteriorly ): pronator teres 9- sphinctor ( decreases size of an opening ): external anal spnicter 10- tensor ( makes a body more rigid ): tensor fascia latae 11- rotator ( moves bone around a longitudinal axis ): rotators

14- Describe in detail the sliding filament mechanism which causes muscle contraction and include the following stages:

a- ATP hydrolysis: myosin head includes an ATP binding site and an enzyme that hydrolyzes ( breaks-down ) ATP to ADP, PO4, +e` -- energizes the myosin - all products remain attached b- attachment of myosin to actin to form cross bridges: the energized myosin head attaches to the actin and is now a crossbridge c- power stroke: crossbridge begins to generate force due to presence of e` and rotates towards the M line causing the thin filament to slide past the thick filament d- detachment of myosin from actin: occurs when crossbridge binds another molecule of ATP

3- Describe in detail the structure of actin and myosin molecules:

a- actin: a thin filament made of protein - composed of individual molecules twisted into a helix shape - on each molecule is a myosin binding site ( covered by a regulatory protein < tropomyosin > when relaxed ) -- b- myosin: contractile protein ( 200 molecules of which form a single thick filament ) - molecule shaped like two golf clubs twisted together - tail points towards M-line - head ( cross bridge ) extends towards filaments

4- Explain how muscles are named and give specific examples

a- direction: relative to midline 1- rectus: fibers run parallel to midline ( rectus abdominus ) 2- transverse: fibers run perpendicular to midline ( transversus abdominus ) 3- oblique: fibers run diagonally to midline ( external oblique ) b- location: i.e., structure near which muscle is found 1- frontalis: muscle near frontal bone 2- tibialis anterior: muscle near tibia c- size: relative size of muscle 1- maximus ( largest ): gluteus maximus 2- minimus ( smallest ): gluteus minimus 3- longus ( longest ): adductor longus 4- brevis ( shortest ): peroneus brevis d- number of tendons of origin 1- biceps ( two ): biceps brachii 2- triceps ( three ): triceps brachii 3- quadriceps ( four ): quadriceps femoris e- shape 1- deltoid ( triangular ): deltoid 2- trapezius ( trapezoidal ): trapezius 3- serratus ( saw toothed ): serratus anterior 4- rhomboidus ( diamond ): rhomboidus major

6- Explain the following properties (characteristics) of muscle tissue :

a- excitability: responds to certain stimuli b- contractility: ability to shorten and thicken c- extensibility: stretch without damage d- elasticity: ability to return to the original shape after ' c & d ' conductivity: conduct action potential along the plasma membrane

9- Distinguish among the following tissue components associated with muscle tissue:

a- fascia: large connective tissue sheets that wrap around groups of muscles b- epimysium: connective tissue covering the entire muscle perimysium: connective tissue covering the fascicle endomysium: connective tissue covering the individual fiber c- tendon: connective tissue attaching muscle to bone aponeurosis: sheet-like tendon attaching muscle to muscle or to bone tendon sheath:tubes of fibrous connective tissue enclosing certain tendons ( i.e., wrist and ankle )

27-Explain the difference between isometric and isotonic muscle contractions

a- isometric contraction: tension generated not enough to exceed the resistance of the object, and the muscle does not shorten - energy is expended b- isotonic: tension developed by muscle remains constant while the muscle changes its length - two types 1- concentric isotonic contraction: muscle shortens, pulls on a tendon attached to another bone, and angle between the bones decreases 2- eccentric isotonic contraction : lengthening of a muscle during contraction i.e., holding a heavy wait at arms length

21- Describe how a motor unit is constructed and explain the rol motor units play in determining the precision and power involved in muscle contraction:

a- motor unit: a single neuron with all of the muscle fibers it contacts ( axon has many axon termoinals - as many as 150 muscle fibers /neuron ) -- all of muscle fibers in one motor unit contract in unison b- precision: smaller number of fibers/motor unit - i.e., muscle of larynx has 23, muscles for eye movements have 1020 c- power: for larger muscles motor unit may have 2000-3000 muscle fibers / motor unit

3- Explain how coordination within the muscle groups occurs by describing the following:

a- prime mover ( agonist ): muscle directly responsible for producing the desired motion - biceps: flexing the arm i.e., 'making a muscle' b- antagonist: muscle that has an action opposite to the prime mover and yields to the movement of the prime mover - triceps c- synergist ( fixator ): muscle that assists the prime mover by reducing undesired action or unnecessary motion - i.e., pectoralis minor & trapezius help hold the scapula ( part of the pectoral girdle that serves as origin for muscles that help move the arm ) firmly against the back of the chest

12- Be able to identify and label the following parts of a skeletal muscle myofibril

a- sarcomere; the basic functional/contractual unit of a muscle cell/fiber b- I band: contains thin filaments - no thick ones c- A band: contains mostly thick filaments - some thin ones where they overlap the thick filaments d-Thin filaments ( actin ): one of the two contractile filaments - the filaments that slide towards the center of the sarcomere e-thick filaments ( myosin ): one of the two contractile filaments - f- Z-disc ( line ): separates one sarcomere from another

11- Explain how skeletal muscles are organized, including the following:

a- whole muscle: contains groups of individual muscle fibers in compartments called fascicles b- fascicle: a compartment containing many individual muscle (myo) fibers c- muscle fiber: an individual muscle cell d- myofibril: a compartment with a myofiber containing contractile elements e- thin and thick filaments: the contractile elements within a myofibril f- sarcomere: the contractile unit of a myofibril