Muscle

table 4.1

types of muscle

type 1

slow tonic movement

red in colour due to large amount of myoglobin

rich in mitochondria and oxidative enzymes

poor in phosphorylases

highly resistant to fatigue

type 2

Fast phasic movement

paler in colour due to smaller amount of myoglobin

rich in glycogen and phosphorylases

poor in mitochondria content

gets fatigued very easily

intermediate

simply type 2 muscle fibers but with good amount of resistance to fatiguedness

classifications of muscles

Spiral or twisted

Found in trapezius, pectoralis major, latissimus dorsi

Oblique Fasciculi(are oblique to the line of pull)

circumpennate(tibialis anterior

multipennate(deltoid)

bipennate(rectus femoris)

Unipennate(palmar interossei)

Triangular(temporalis)

parallel fasciculi(fascicule are parallel to the line of pull)

fusiform (biceps brachii)

strap-like with tendinous intersections(rectus abdominis)

strap-like(sternohyoid)

Quadrilateral(thyrohyoid)

Muscles that extend over 2 or more joints are called diarthic or polyarthric muscles

nerve supply of skeletal muscle

Motor fibers(60%)

large myelinated alpha efferents which supply extrafusal muscle fibers

small myelinated alpha efferents which supply intrafusal muscle

fine non-myelinated autonomic efferents supply smooth

Sensory fibers(40%)

myelinated fibers distributed to muscle spindles for proprioception , also to tendons

Muscle spindles are spindle shaped sensory end organs of the muscle

Motor point is the site where motor nerves enters the muscle

motor unit is defined as a single alpha motor neuron together with the muscle supplied by it

Hybrid muscle are supplied by 2 different motor nerves with different root values

nerve supply of smooth muscles

Single unit type seen in intestine impulse reaches one muscle , is transmitted to other cells by mechanical pull through the fused cell membrane

Multi-unit type seen in the muscles of the ductus deferens each muscle cell receives a seperate nerve fibers(rich in nerve supply)

nerve supply of cardiac muscle is sympathetic and parasympathetic nerve fibers

Movement of muscle

isotonic(length of muscle decrease)

isometric(length may remain remain unchanged)

may increase acc to functional demanda

classifications of muscle groups acc to their functions

prime movers(bring desired movement)(when they help opposite action by active controlled lengthening against gravity it is known as action of paradox

Antagonists (oppose prime movers)(active controlled relaxations so that desired movement is smooth and precise(thus they cooperate them rather than oppose which is due to reciprocal innervation of the opposite muscle groups)(spinal cord through reflex arc)

fixators are the group of muscles which stabilizes the proximal joints of a limb so movement may occur at distil joint muscle on shoulder fix it for better movement of digits

synergids (when th eprime movers cross more than one joint the undesired actions at the proximal joints are prevented by certain muscles known as synergids)(during fist making wrist is kept fixed)

character of muscles

excitability, contractability, conductivity, excitability