1. Muscular System
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2. Muscle types

3. Skeletal Muscle Organ of the muscular system
Covered by connective tissue called fascia
Separated into epi-, peri-, and endomysium (figure 10.1)

4. Skeletal Muscle Fibers (cells)
Thin, elongated cylinder with rounded ends
Cell membrane called sarcolemma
Many nuclei and mitochondria

5. Anatomy of a muscle
“Bundles”
Muscle
Fascicles
Fibers (cells)
Myofibrils
Myofilaments

6. Movement Functions sphincter Storing and moving substances
Stabilizing joints
Functions
sphincter
Storing and
moving substances
Stabilizing posture
Thermogenesis

7. Excitability
Extensibility
Properties
Elasticity
Contractility

8. Myofibrils play fundamental role in contraction
Myosin– thick (A bands with H zone)
Actin– thin (I bands with Z lines)

9. Z Line to Z Line called Sarcomere

11. Connected to motor neuron at neuromuscular junction
Stimulated by neurotransmitters
Entire unit called motor unit
One neuron, many muscle cells

12. Must be stimulated by the neurotransmitter acetylcholine (from motor neuron)

13. Skeletal Muscle Contraction
Sliding filament theory (figure 10.11) cross bridges formed between actin and myosin filaments when Ca2+ present
Using energy from ATP cross-bridges bend then break then form another bridge further down the actin filament
animation

14. Detailed animation

15. Muscle impulse creates increased permeability to calcium ions
Reversed when nerve impulses cease and muscle relaxes (acetylcholine broken down)

16. Steps of muscle contraction
Electric signal sent from brain down
motor neuron to neuromuscular junction
2. Neurotransmitter signal sent from neuron
received by sarcolemma of muscle cell
3. Calcium ion movement into muscle cell
4. Myosin forms cross bridges with actin
5. ATP allows cross bridges to bend,
brake, and reform (power stroke)
6. Filaments continue to slide past each
other until actin overlaps (sarcomere
shortens)

17. Enzyme ATPase catalyzes breakdown of ATP– regenerated by creatine phosphate

18. Oxygen needed to effectively contract
When muscles strenuously exercised anaerobic respiration occurs and muscles develop oxygen debt
Lactic acid produces
May lead to muscle fatigue or inability to contract

19. Heat released as only 25% of energy used

20. Muscle Responses
Threshold stimulus- minimal stimuli needed to cause contraction
All-or-none response
Can be recorded on myogram (figure 10.15)

21. Series of stimuli causes summation (sustained contraction)
All fibers in motor unit stimulated at the same time
Entire muscle contracts as motor units recruit others
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22. Skeletal Muscle Actions
(main movements)
Origin- immovable end
Insertion- movable end
Pulled toward origin with contraction
Muscles can have more than one of either
Ex. Biceps brachii
Belly

23. Muscles almost always function in groups
Prime mover- provides most movement (contracts)
Synergist- assists prime mover
Antagonist- relaxes (opposite movement)

27. Muscle Names Often describe them Size- pectoralis major Shape- deltoid
Location sternocleidomastoid
Action- extensor digitorum
Number of attachments triceps brachii
Direction of fibers external obliques

28. Size terms
Major
Vastus
Maximus
Medius

29. Location
Frontalis
Temporalis
Tibialis anterior
Biceps femoris

30. Action
Adductor
Extensor digitorum
Adductor
Extensor digitorum

31. Number of attachments Biceps brachii Also give location Biceps femoris
Triceps brachii
Also give location

32. Direction of fibers
External oblique
Rectus abdominus

33. Arrangement of fascicles
table 11.1

35. Parallel muscle
Sternocleidomastoid

36. Parallel muscle
Sartorius

37. Fusiform
Biceps Brachii
                        
                        

38. Fusiform
Tensor Fasciae Lata

39. Fusiform
Semitendinosus

40. Triangular (convergent) muscle
Pectoralis Major

41. Bipennate muscle
Rectus Femoris

42. Unipennate
Extensor Digitorum Longus

43. Multipennate
Deltoids

44. Circular Muscles
Orbicularis oculi
Orbicularis oris

45. link