1. Muscles, Muscles, Muscles
                                  
                                  
                                  
                                  
9/12/2018

2. Muscular System Functions
Body movement
Maintenance of posture
Respiration
Production of body heat
Communication
Constriction of organs and vessels
Heart beat

3. The human body
9/12/2018

4. About how many muscles do you think the human body has?
Answer = 650
9/12/2018

5. Types of Muscle Contractions
Isometric: No change in length but tension increases
Postural muscles of body
Isotonic: Change in length but tension constant
Concentric: Overcomes opposing resistance and muscle shortens
Eccentric: Tension maintained but muscle lengthens
Muscle tone: Constant tension by muscles for long periods of time

6. Three potential actions during muscle contraction:
Biceps muscle shortens
during contraction
shortening
isometric
Most likely to cause
muscle injury
lengthening
Biceps muscle lengthens
during contraction

7. Muscle Tissue Types Skeletal Smooth Cardiac Attached to bones
Nuclei multiple and peripherally located
Striated, Voluntary and involuntary (reflexes)
Smooth
Walls of hollow organs, blood vessels, eye, glands, skin
Single nucleus centrally located
Not striated, involuntary, gap junctions in visceral smooth
Cardiac
Heart
Striations, involuntary, intercalated disks

8. Muscle Teamwork Agonist (prime mover):
- the muscle or group of muscles producing a desired effect
Antagonist:
- the muscle or group of muscles opposing the action
Synergist:
- the muscles surrounding the joint being moved
Fixators:
- the muscle or group of muscles that steady joints closer to the body axis so that the desired action can occur

9. Skeletal Muscle
An organ consisting of skeletal muscle tissue, nervous tissue, blood, and connective tissues
Fascia separates one muscle fiber from the next and holds it in place. These can be continuous with tendons, and intertwines to periosteum to connect it to a bone
Fascia can also form aponeuroses which are broad sheets of connective tissues connecting to other muscles

10. Refresher Course in Muscle Physiology
Structural hierarchy of skeletal muscle
4/11/2003
Muscle
A little less than half of the body’s
mass is composed of skeletal
muscle, with most muscles linked
to bones by tendons through which
the forces and movements
developed during contractions
are transmitted to the skeleton.
Muscle fibers
Muscle fiber
Myofibril
Sarcomere
Modified from McMahon, Muscles, Reflexes and Locomotion
Princeton University Press, 1984.
EB2003--Susan Brooks

11. Components of skeletal muscle
d) myofibril c) muscle fibre b) muscle fibre bundle a) Muscle belly
Sport Books Publisher

12. Organization I:

13. Organization II:

14. Organization III:

15. Muscle Fibres Cylinder-shaped cells that make up skeletal muscle
Each fibre is made up of a number of myofilaments
Diameter of fibre ( mm)
Length of fibre (appr. 15 cm)
Surrounded by a connective tissue sheath called Sarcolemma
Many fibres are enclosed by connective tissue sheath Perimycium to form bundle of fibres
Each fibre contains contractile machinery and cell organelles
Activated through impulses via motor end plate
Group of fibres activated via same nerve: motor unit
Each fibre has capillaries that supply nutrients and eliminate waste
Sport Books Publisher

16. More Skeletal Muscle
Epimysium: layer of connective tissue surrounding muscle
Perimyseum: extend in from epimysium and separate muscle into compartments.
Fascicles: separated muscle fibers
Endomysium: thin membrane housing the fascicles

17. Parts of a Muscle

18. Muscle fibre:

19. Internal organization:

20. Organization of myofilaments II:

21. Muscles contract when the nervous systems causes muscle filaments to move.
Muscle fibers are cells of the muscular system.
muscle
muscle fiber

22. Myofibrils are long strands of protein in the muscle fiber.

23. Each myofibril is divided into sarcomeres.
Sarcomeres contain filaments that cause contraction.
myofibril
muscle fiber
muscle
sarcomere

24. Skeletal Muscle Fibers
Single cell
Responds to stimulus…contraction
Sarcolemma: its membrane
Sarcoplasm: its cytoplasm
Many nuclei and mitochondria
Sarcoplasm contains myofibrils: threadlike, parallel fibers containing actin and myosin

25. Each myofibril is divided into sarcomeres.
Sarcomeres contain filaments that cause contraction.
Actin filaments are pulled during contraction.
Myosin filaments pull actin during contraction.
CONTRACTION
RELAXATION
M line
myosin
Z line

26. Actin and myosin Patterns of these creates striations
I bands: light bands, actin connected to Z lines
A bands: thick myosin filaments overlapping actin filaments. This area encompasses the overlapping of thick/thin filaments and the central H Zone, plus the M Line
A Sarcomere goes from one Z line to the next

28. High microscope magnification of sarcomeres within a myofibril
Sport Books Publisher

29. Sarcomere
Sarcoplasmic reticulum: Like ER, but surrounding each myofibril, and running parallel to it
Transverse tubule: runs laterally across cell, reaches all the way across
Transverse tubules cross SR at cisternae: enlarged pockets on SR.
The SR and Transverse tubule initiate contractions

30. Excitation-Contraction Coupling
Mechanism where an action potential causes muscle fiber contraction
Involves
Sarcolemma
Transverse or T tubules
Terminal cisternae
Sarcoplasmic reticulum
Ca2+
Troponin

31. Motor Units A motor neuron and the muscle fibers it controls
A motor neuron causes all fibers that are linked to it to contract simultaneously

32. Neuromuscular Junction
Each skeletal muscle attached to a motor neuron
This connection is called a neuromuscular junction
The fiber membrane here is called the Motor End Plate, which is full of mitochondria, and the sarcolemma is very folded
The nerve end is loaded with vesicles containing neurotransmitters
These neurotransmitters (acetylcholine) cross the synapse and stimulate a muscle contraction

33. Neuron stimulates muscle at the neuromuscular junction.

34. Energy Sources for Contraction
ATP allows contractions to occur
Creatine Phosphate is the first store of energy to recharge ADP back to ATP
Creatine Phosphate stores are limited, and after it is exhausted, cell respiration supplies the ATP to get the job done.

35. Muscle Contractions: Once upon a time, there was a neurotransmitter released…
Sliding Filament Theory: The head of a myosin cross bridge attaches to an actin and bends slightly, pulling the actin filament with it. It then releases, straightens, and grabs another actin binding site further up. Repeat as necessary.
Myosin cross bridges contain ATPase which releases energy from ATP to fuel contraction
Acetylcholinesterase decomposes acetylcholine, which stops continuous contractions from one impulse

36. Neuron stimulates muscle at the neuromuscular junction.
Neurotransmitters cause calcium channels in the sarcomere to open.
regulatory protein
Calcium exposes binding sites.
Myosin binds to actin and pulls it.
As the sarcomere shortens, the muscle contracts.
myosin
actin
Z line

37. Cross-bridge formation:

38. Sarcomere Shortening

39. Slow and Fast Fibers Slow-twitch or high-oxidative
Contract more slowly, smaller in diameter, better blood supply, more mitochondria, more fatigue-resistant than fast-twitch
Fast-twitch or low-oxidative
Respond rapidly to nervous stimulation, contain myosin to break down ATP more rapidly, less blood supply, fewer and smaller mitochondria than slow-twitch
Distribution of fast-twitch and slow twitch
Most muscles have both but varies for each muscle
Effects of exercise
Hypertrophies: Increases in muscle size
Atrophies: Decreases in muscle size

40. Fatigue
Decreased capacity to work and reduced efficiency of performance
Types:
Psychological
Depends on emotional state of individual
Muscular
Results from ATP depletion
Synaptic
Occurs in neuromuscular junction due to lack of acetylcholine

41. Effects of Aging on Skeletal Muscle
Reduced muscle mass
Increased time for muscle to contract in response to nervous stimuli
Reduced stamina
Increased recovery time
Loss of muscle fibers
Decreased density of capillaries in muscle