chapter 7 muscular
TRANSCRIPT
• Body Movement• Maintenance of Posture• Respiration• Production of Body Heat• Communication• Constriction of Organs and Blood
Vessels• Heart Beat
Functions
• CONTRACTILITY: ability of skeletal muscle to shorten with force.
• EXCITABILITY: capacity of skeletal muscle to respond to a stimulus.
• EXTENSIBILITY: skeletal muscle can be stretched to their normal resting length and beyond to a limited degree.
• ELASTICITY: ability of skeletal muscle muscles to recoil to their original resting length after they have been stretched.
Functional Characteristics
Sarcomer
e
SarcoplasmicReticulum
Transverse Tubule
Capillaries
Nuclei
Bone
Tendon
Skeletal muscle
Epimysium(fascia)
Fasciculi
Endomysium
Muscle fiber
Mito
chondria
Myofibrils
Actin
Myosin
Sarcolema
Sarcomere – Basic structural and functional unit of skeletal muscle.– Each sarcomere extends from one Z-disk to
another Z-disk
Z-Disk – a network of protein fibers forming an attachment site for actin myofilaments
Sarcomere – Basic structural and functional unit of skeletal muscle.– Each sarcomere extends from one Z-disk to
another Z-disk
Z-Disk – a network of protein fibers forming an attachment site for actin myofilaments
• Troponin – attached at a specific interval along the actin and provide calcium binding sites on the actin myofilament
• Tropomyosin – located along the groove between the twisted strands of actin myofilament.
Actin
1st the Central Nervous System
gives the order for muscle contraction
The order (to contract) reaches the Muscle thru
the Neuro-Muscular Junction
• Charge Difference– Higher concentration of Potassium (K+)
inside the cell membrane.– Potassium is more permeable than other
ions• Action Potential – Rapid depolarization and
repolarization of the cell membrane
IN
- - - --
-KPotassium
OUT
+ + + + ++
NaSodium
Mem
bra
ne p
ote
nti
al
Cell Membrane
1.Action potential arriving at the presynaptic terminal causes synaptic vesicles to move and to bind with the cell membrane
2.Synaptic vesicles release acetylcholine (Ach) into the synaptic cleft by exocytosis
3.Acetylcholine diffuses across the synaptic cleft
4.Acetylcholine binds to Acetylcholine receptor sites on Na+ channels in postsynaptic (muscle) cell membrane
5.Combination of Acetylcholine with its receptor site opens Na+ channels and causes and increase in the permeability of the muscle cell membrane to Na+. The movement of Na+ into the cell can result to action potential
ACh binds to receptors in the sarcolema band
spreads in all direction
Sends electrical impulse to the t-
tubules
Releases Calcium
• Force of contraction:• Summation – Increase the force of the
contraction• Recruitment – Increase the number of muscle
fibers contracting
• Tetanus – Sustained contraction
• Rigor mortis – Muscles become rigid
– Types of muscle contraction– Isometric contraction – equal distance– Isotonic contraction – equal tension
– Concentric contraction– Eccentric contraction
–Muscle tone – Refers to the constant tension produced by the muscle over long periods of time
• Agonist – muscle that accomplishes a certain movement.
• Antagonist – muscle acting to oppose the agonist.
• Synergist – members of the same group acting to produce a movement
• Prime movers• Fixators