produce movement maintain posture stabilize joints generate heat move substances within the body Muscle Function

Excitability- respond to a stimulus Contractility- ability to shorten forcibly when adequately stimulated Extensibility- the ability to be stretched Elasticity- the ability of a muscle fiber to resume its resting length after being stretched Functional Characteristics

Skeletal Muscle Striated Multinucleate Voluntary

Cardiac Muscle Striated Uninucleate Involuntary Branching Intercalated discs

Smooth Muscle Unstriated Uninucleate Involuntary Hollow walled organs and blood vessels

Skeletal Muscle Connective tissue sheaths of skeletal muscle: Epimysium: dense regular connective tissue surrounding entire muscleEpimysium: dense regular connective tissue surrounding entire muscle Perimysium: fibrous connective tissue surrounding fascicles (groups of muscle fibers)Perimysium: fibrous connective tissue surrounding fascicles (groups of muscle fibers) Endomysium: fine areolar connective tissue surrounding each muscle fiberEndomysium: fine areolar connective tissue surrounding each muscle fiber

Figure 9.1 Bone Perimysium Endomysium (between individual muscle fibers) Muscle fiber Fascicle (wrapped by perimysium) Epimysium Tendon Epimysium Muscle fiber in middle of a fascicle Blood vessel Perimysium Endomysium Fascicle (a) (b)

Gross Anatomy Skeletal Muscle

Muscle Anatomy myofibril sarcomere muscle fiber (cell)

Muscle Cell Sarcoplasmic reticulum

Sarcomere

Myofibril

Myosin (Thick) Filament

Actin (Thin) Filament

Cross Bridges

Sliding Filament Hypothesis

No Calcium Ion Calcium Ion Present tropomyosin troponin myosin binding sites actin

Actin & Myosin Interaction

Biology 100 Human Biology Motor Unit spinal cord motor neurons muscle bundle muscle fibers neuromuscular junctions

Neuromuscular junctions branching axon to motor unit muscle fibers

Axon (motor neuron) sarcolemma myofibrils sarcomere sarcoplasm Sarcoplasmic Reticulum Neuromuscular junction

T tubules sarcoplasmic reticulum

Stimulation of Skeletal Muscle

Figure 9.9 Na + Open Na + Channel Closed Na + Channel Closed K + Channel Open K + Channel Action potential Axon terminal Synaptic cleft ACh Sarcoplasm of muscle fiber K+K+ 2 Generation and propagation of the action potential (AP) 3 Repolarization 1 Local depolarization: generation of the end plate potential on the sarcolemma K+K+ K+K+ Na + K+K+ W a v e o f d e p o l a r i z a t i o n

Figure 9.9, step 1 Na + Open Na + Channel Closed K + Channel K+K+ Na + K+K+ Action potential Axon terminal Synaptic cleft ACh Sarcoplasm of muscle fiber K+K+ 1 Local depolarization: generation of the end plate potential on the sarcolemma 1 W a v e o f d e p o l a r i z a t i o n

Figure 9.9, step 2 Na + Open Na + Channel Closed K + Channel K+K+ Na + K+K+ Action potential Axon terminal Synaptic cleft ACh Sarcoplasm of muscle fiber K+K+ Generation and propagation of the action potential (AP) 1 Local depolarization: generation of the end plate potential on the sarcolemma 2 1 W a v e o f d e p o l a r i z a t i o n

Figure 9.9, step 3 Na + Closed Na + Channel Open K + Channel K+K+ Repolarization 3

Figure 9.9 Na + Open Na + Channel Closed K + Channel Action potential Axon terminal Synaptic cleft ACh Sarcoplasm of muscle fiber K+K+ 2 Generation and propagation of the action potential (AP) 3 Repolarization 1 Local depolarization: generation of the end plate potential on the sarcolemma K+K+ K+K+ Na + K+K+ W a v e o f d e p o l a r i z a t i o n Closed Na + Channel Open K + Channel

Figure 9.10 Na + channels close, K + channels open K + channels close Repolarization due to K + exit Threshold Na + channels open Depolarization due to Na+ entry

Stimulation of Skeletal Muscle

Relaxation of Skeletal Muscle

Stimulation of Skeletal Muscle

Muscle Twitch

Contraction Response single twitches wave summation tetanus action potentials in motor neuron

Isotonic and Isometric Contractions Isotonic contraction Contraction with a change in length The muscle shortens and movement occurs. Isometric contraction Contraction without any change in length The muscle does not shorten and there is no movement produced even though the muscle contracts.

Isotonic and Isometric Contractions Isotonic Isometric

ATP is Generated by: 1.creatine phosphate ADP + creatine phosphate  creatine + ATP 2. lactic acid fermentation From stored glycogen via anaerobic glycolysis; glucose  pyruvic acid (no O 2 )  lactic acid O2O2 3. aerobic respiration Glucose  pyruvate  acetyl CoA  Krebs  CO 2 + H 2 O + ATP Energy for muscle contraction: ATP is the only energy source ATP  (ATPase + H 2 O)  ADP + Pi

Slow-Twitch Versus Fast-Twitch Muscle Fibers

Muscle Fiber Types Fast glycolitic Slow oxidative Fast oxidative-glycolytic Ratio- red:white (all 3 types in body)

white muscle fibers low myoglobin anaerobic glycolysis few mitochondria fast twitch fibers high glycogen stores short bursts fatigues easily Fast glycolitic:

Slow oxidative: red muscle aerobic high myoglobin low glycogen stores lots mitochondria slow long distance

Fast glycolitic-oxidative: red  pink aerobic fast high myoglobin intermediate amt. of mitochondria intermediate glycogen intermediate fatigue resistance

Red vs White Muscle long distance blue fin tuna- mostly red meat quick bursts- yellow tail- more white meat

Sprinter- anaerobic respiration Long distance Runner- aerobic respiration

Smooth Muscle Fibers Mainly aerobic Arranged in opposing sheets

Smooth Muscle Fibers peristalsis

Cardiac Tissue More mitochondria Longer refractory period Mainly aerobic respiration Can use multiple fuel molecules

Disuse- atrophy Muscles must be physically active if they are to remain healthy Cast Cast- muscle strength can decrease at a rate of 5%/ day; can use e- stimulus Avoid muscle injuries: warm up muscles- walk fast 5 minutes then stretch- avoids pulls and tares Effects of Exercise

Steroids Anabolic steroids similar to testosterone large doses required for good effect Side effects: overall - kidney and heart damage, aggressiveness females - sterility, facial hair, breast & uterine atrophy males - baldness, atrophy of testis

cramp- sustained spasm or tetanic contraction; may be due to low blood sugar levels, electrolyte depletion, dehydration strain- muscle pull spasm- tics Muscle Injuries hernia- protrusion of organ through body cavity wall  may be due to heavy wts.

Inquiry 1.What is stored in SER? 2.Which protein blocks the heads of myosin? 3.When a neuron synapses with a muscle it is called The neuron going to a muscle is called ____. 5.A muscle that shortens or lengthens is called ____. 6.Which ion floods into the sarcolemma after stimulation by a neuron? 7.Which neurotransmitter binds to the sarcolemma? 8.Which type of muscles undergo aerobic respiration? 9.Which type of fuel is stored in muscle tissues? 10.Which pigment is stored in muscles that has a high affinity for oxygen? 11.Which muscle tissue has intercalated discs? 12.What is depolarization?