Muscles and Muscle Tissue

1. Muscles and Muscle Tissue

2. Review of movement types • Flexor • Extensor • Abduction • Adduction • Rotation

4. Muscles students need to know: Rotator Cuff Deltoid (delts) Pectorals (pecs)  Biceps External Obliques(waist) Quadriceps (quads) Tibialis Anterior(shins) Internal Obliques (waist) Adductors (inner thighs)

5. Trapezius (traps) Triceps Latissimus Dorsi (lats) Forearm Gluteus Medius (outer thigh) Gluteus Maximus (glutes) Gastonemius (calves) Soleus (calves)

6. Attachments • most muscles span joints and are attached to bones in at least two places • Insertion – • Origin – • Example: • biceps – origin scapula, insertion radius • rectus femoris – origin illium, insertion patella • Tendons – • Belly –

7. Muscle groups • Opposing muscles – • Synergists – • Muscle types • Skeletal • Location – • Appearance – • Microscopic structure – • Action -

8. Cardiac • Location – • Appearance – • Microscopic structure – • Action –

9. Smooth • Location – • Appearance – • Microscopic structure – • Action –

10. Microscopic anatomy of a skeletal muscle fiber • Muscle fiber – • Sarcolemma – • Myoglobin – • Myofibrils – • Striations – • Sarcomere -

12. Molecular composition of the myofilaments • Thick filaments – myosin • Heads from cross bridges • Thin filaments – actin • Tropomyosin: spiral about actin. They block actin’s active sites so that the myosin heads can’t bind. • Sarcoplasmic reticulum: elaborate smooth endoplasmic reticulum surrounding each myofibrin. They regulate intracellular calcium levels (stores and releases it).

13. Contraction of a skeletal muscle fiber • Muscle fiber – • Calcium – • This moves the tropomyosin – • Cross bridge attachment – • As myosin binds – • A new ATP molecule binds to myosin – • Hydrolysis at ATP to ADP and P provides the energy • Sliding of the thin filaments continues as long as the calcium signal and adequate ATP are present

15. Regulation of contraction • Structures involved • Motor neuron (nerve cell) – • Neuromuscular junction – • Motor unit – • Acetylcholine – • Ach receptors – found on muscle fiber • Motor end plate –

16. Sequence of events • Nerve impulse reaches neuromuscular junction • Voltage regulated calcium channels in neuron membrane open allowing Ca2+ into cell • Ach vesicles on end bulb release Ach • Ach binds to Ach receptors on motor end plate • Binding leads to depolarization of muscle fiber membrane (change in voltage)

17. F. Depolarization opens Na+ channels creating an action potential G. Action potential triggers the release of Ca++, nutrients, oxygen into the muscle tissue from sarcoplasmic reticulum H. Acetylcholinesterase is an enzyme (eraser enzyme) that destroys Ach preventing continued muscle fiber contraction I. Calcium is constantly pumped back into the sarcoplasmic reticulum. Once calcium is removed the muscle relaxes

18. ALL OR NOTHING *When a motor neuron fires - all the fibers in the motor unit will contract – ALL OR NOTHING PRINCIPLE

19. Since a large muscle is comprised of many motor units, these units (and all of their many involved muscle cells) take turns contracting and relaxing. Less stress – smoother contractions Less force – sustained contractions Less fatigue – less lactic acid build up

20. Forceful vs. Delicate Contractions Dictated by the: • number of motor units involved • the frequency of the nerve impulses • the duration of each nerve impulse

21. Types of Muscle Fibers • Fast twitch fibers – fast, powerful contractions – fatigue quickly (white) • Slow twitch fibers – slow, little power, fatigue resistant and has high endurance (red, dark) • Most muscles contain a mixture of both types. Some people have relatively more of one type than others.

22. Contraction of a skeletal muscle • Motor unit – • When motor neuron fires all the fibers it innervates respond by contracting (all or nothing principal) • The number of muscle fibers innervated by a motor neuron varies

23. Fine control muscles – • Large weight bearing muscles – • Stimulation of a single motor unit causes a weak contraction of the entire muscle. The more motor units recruited, the stronger the contraction.

24. Types of muscle contraction • Twitch contraction – a single muscle contraction (contract then relaxes) can be strong or weak depending on the number of motor units activated • Latent period – • Contraction – • Relaxation – • Recovery –

25. Graded muscle responses – most muscles do not operate as single twitch contractions, they are relatively smooth and vary in strength and duration • Frequency of stimulation • Stronger stimuli • Treppe – • Muscle fatigue – • Muscle tone – • Isotonic contraction – • Isometric contraction –

26. Muscle metabolism • Muscles require energy in the form of ATP to contract • ATP is generated in three ways: • Aerobic respiration – • Direct phosphorylation of ADP by creatine phosphate • Anaerobic glycolysis • As long as muscles can get enough oxygen it will use aerobic respiration. As demands get higher, phosphorylation and finally anaerobic glycolysis is used. Eventually muscle fatigue will set as a result of lactic acid build up.