anatomy and physiology of muscular system

1. MUSCULAR SYSTEM
BY
SONI KUMARI SHAH

2. Muscular System
System of human body that provides motor power for all movements of
body parts.
It consists of large number of muscles (about 639) and composed of
special tissue known as muscular tissue.
The muscles have the ability to contract actively to provide force for
movements of the body parts.

3. Functions Of Muscular System
It helps in the movements of body parts.
It stabilizes skeleton and give a proper posture.
It helps in heat production.
The cardiac muscle provides main force for circulation of blood
throughout the body.
The smooth muscles helps the digestive system in digestion of food.

4. Muscle
Muscle is a type of tissue composed of contractile cells or fibers.
The study of muscles is known as myology.
The contraction of muscles cause the movement of organs or parts of
the body.

5. Properties Of Muscles
Contractibility
Excitability
Elasticity
Extensibility

6. Types Of Muscular Tissue
1. Skeletal muscle
2. Smooth muscle
3. Cardiac muscle

7. Skeletal Muscle
These are Present mainly in limbs and in relation to body wall.
They have Close relation with bony skeleton hence called skeletal muscle.
They Show prominent transverse striation, so also called striated muscle.
These are Voluntary in nature.
They are Supplied by somatic motor nerves.

8. Smooth Muscle
These are Present in relation to viscera, Typically in walls of hollow visceras.
They are Non-striated muscle.
They are Involuntary in nature.
These are Supplied by autonomic nerves.

9. Cardiac Muscle
Cardiac muscle is Present exclusively in heart.
They Show transverse striation.
They are Involuntary in nature.
It has inherent rhythmic contractility.
They are Supplied by autonomic nerves.

10. Which muscle type is considered voluntary?
A. Cardiac
B. Smooth
C. Skeletal
D. Epimysium
Smooth muscle cells may be described by which of the following?
A. striated, voluntary, multinucleate
B. not striated, voluntary, multinucleate
C. striated, involuntary, uninucleate
D. not striated, involuntary, uninucleate
Which one of the following is NOT a characteristic of skeletal muscle?
A. excitability
B. autonomic innervation
C. contractility
D. extensibility

11. Organization Of Skeletal Muscle
A skeletal muscle may sometimes contain
hundreds of thousands of muscle fibers as well as
blood vessels and nerves.
The entire muscle is covered in a connective
tissue sheath called the epimysium.
Within the muscle, the cells are collected into
separate bundles called fascicles, and each
fascicle is covered in its own connective tissue
sheath called the perimysium.
Within the fascicles, the individual muscle cells
are each wrapped in a fine connective tissue layer
called the endomysium.

12. Organization Of Skeletal Muscle
Each of these connective tissue layers runs the
length of the muscle.
They bind the fibers into a highly organized
structure, and blend together at each end of the
muscle to form the tendon, which secures the
muscle to bone.
Often the tendon is rope-like, but sometimes it
forms a broad sheet called an aponeurosis, e.g.
the occipitofrontalis muscle.
The fleshy part of the muscle is called the belly.

13. Structure Of Skeletal Muscle Cells (Fibers )
Under the microscope, skeletal muscle cells are seen to be
roughly cylindrical in shape, lying parallel to one another,
with a distinctive banded appearance consisting of
alternate dark and light stripes.
Individual fibers may be very long, up to 35 cm in the
longest muscles.
Each cell has several nuclei, found just under the cell
membrane (the sarcolemma).
The cytoplasm of muscle cells, also called sarcoplasm.

14. Structure Of Skeletal Muscle Cells (Fibers )
There are also many mitochondria, essential for producing adenosine
triphosphate (ATP) from glucose and oxygen to power the contractile
mechanism.
Also present is a specialized oxygen-binding substance called myoglobin,
which stores oxygen within the muscle.
In addition, there are extensive intracellular stores of calcium.

15. Structure Of Skeletal Muscle Cells (Fibers )
There are two types of contractile myofilament within the muscle fiber,
called thick and thin, arranged in repeating units called sarcomeres.
The thick filaments, which are made of the protein myosin, correspond
to the dark bands(A band) seen under the microscope.
The thin filaments are made of the protein actin. Where only these are
present, the bands are lighter(I band) in appearance.
Each sarcomere is bounded at each end by a dense stripe, the Z disc, to
which the actin fibers are attached, and lying in the middle of the
sarcomere are the myosin filaments, overlapping with the actin.

16. Structure Of Skeletal Muscle Cells (Fibers )
H zone: it is a zone in central portion of sarcomere where there is no
overlapping of I and A band.
M band: it is the central portion of H zone or central non overlapping zone.
The distance between two z disc is called sarcomere.

17. By what name is the plasma membrane of a muscle cell known?
A. sarcoplasm
B. sarcomere
C. sarcoplasmic reticulum
D. Sarcolemma
All of the following structures are part of a muscle cell except one. Which one?
A. sarcoma
B. sarcolemma
C. sarcoplasm
D. sarcoplasmic reticulum
Which protein(s) are found in thin myofilaments?
A. actin
B. actin and tropomyosin
C. actin, tropomyosin, and troponin
D. actin, myosin, tropomyosin and troponin

18. What structures attach a muscle to a bone?
A. a tendon
B. a fasciculus
C. a sarcomere
D. an internal intercostal
What is the cytoplasm of a skeletal muscle cell called?
A. sarcolemma
B. sarcomere
C. sarcoplasm
D. Fasciculus
What does the term “origin” refer to in the musculoskeletal system?
A. The point of attachment of a muscle to the “moveable” bone.
B. The line that separates the shaft from the end of a long bone.
C. The point of attachment of a muscle to the “stationary” bone.
D. The end of a long bone.

19. Muscle Attachment
Most skeletal muscles are attached to bones, either directly or indirectly.
In a direct attachment, the epimysium of the muscle fuses to the
periosteum, the fibrous membrane covering the bone.
In an indirect attachment (most common), the epimysium extends past
the muscle as a tendon, or aponeurosis, and attaches to the bone.

20. Contraction
During contraction, one of the bones to which the muscle is attached stays
relatively stationary while the other is pulled in toward the stationary one.
Origin and Insertion
The point where the muscle attaches to the stationary or less movable
bone is called the origin.
The point where it attaches to the more movable bone is called the
insertion.
The origin usually lies on the proximal end of the bone. The insertion site is
on the distal end.

21. How The Body Moves
Various parts of the musculoskeletal system work with the nervous system to
produce voluntary movements.
Muscles contract when stimulated by impulses from the nervous system.
During contraction, the muscle shortens, pulling on the bones to which it’s
attached.
Force is applied to the tendon; then one bone is pulled toward, moved away
from, or rotated around a second bone, depending on the type of muscle
that has contracted.
Most movement involves groups of muscles rather than one muscle.

22. Muscle Growth
Muscle develops when existing muscle fibers hypertrophy.
Muscle strength and size differ among individuals because of such
factors as exercise, nutrition, gender, age, and genetic constitution.
Changes in nutrition or exercise affect muscle strength and size in an
individual.

23. Muscle Movements
Skeletal muscle can permit several types of movement.
A muscle’s functional name comes from the type of movement it permits.
For example, a flexor muscle permits bending (flexion); an adductor
muscle permits movement toward a body axis (adduction); and a
circumductor muscle allows a circular movement (circumduction).

24. Action Of Skeletal Muscle
When individual muscle cells in a muscle shorten, they pull on the
connective tissue framework running through the whole muscle, and the
muscle develops a degree of tension (tone).
Muscle Tone
When a muscle fiber contracts, it obeys the all-or-none law, i.e. the whole
fiber either contracts completely or not at all.
Muscle tone is a sustained, partial muscle contraction that allows posture
to be maintained without fatiguing the muscles involved. For instance,
keeping the head upright requires constant activity of the muscles of the
neck and shoulders.

25. Muscle Fatigue
To work at sustained levels, muscles need an adequate supply of oxygen and
fuel such as glucose.
Fatigue occurs when a muscle works at a level that exceeds these supplies.
The muscle response decreases with fatigue. An adequate oxygen supply is
needed to fully release all the energy stored within these fuel molecules;
without it, the body uses anaerobic metabolic pathways that are less
efficient and lead to lactic acid production.
Fatigue (and muscle pain) resulting from inadequate oxygen supply, as in
strenuous exercise, occurs when lactic acid accumulates in working muscles.
Fatigue may also occur because energy stores are exhausted, or due to
physical injury to muscle, which may occur after prolonged episodes of
strenuous activity, e.g. marathon running.

26. Muscle Recovery
After exercise, muscle needs a period of time to recover, to replenish
its ATP and glycogen stores and to repair any damaged fibers.
For some time following exercise, depending on the degree of exertion,
the oxygen debt remains (an extended period of increased oxygen
demand), as the body converts lactic acid to pyruvic acid and replaces
its energy stores.

27. Factors Affecting Skeletal Muscle Performance
Skeletal muscle performs better when it is regularly exercised.
Training improves endurance and power.
Anaerobic training, such as weightlifting, increases muscle bulk because
it increases the size of individual fibers within the muscle (hypertrophy).

28. The Neuromuscular Junction
Junction between the terminal nerve
fibers and muscle fiber is called
neuromuscular junction.
The axons of motor neurons, carrying
impulses to skeletal muscle to produce
contraction, divide into a number of fine
filaments terminating in minute pads
called synaptic knobs.
The space between the synaptic knob and
the muscle cell is called the synaptic cleft.

29. The Neuromuscular Junction
Stimulation of the motor neuron
releases the neurotransmitter
acetylcholine (ACh), which diffuses
across the synaptic cleft and binds
to acetylcholine receptors on the
postsynaptic membrane on the
motor end plate (the area of the
muscle membrane directly across
the synaptic cleft).
Acetylcholine causes contraction of
the muscle cell.

30. Motor Units
Each muscle fiber is stimulated by only one synaptic knob, but since each
motor nerve has many synaptic knobs, it stimulates a number of muscle
fibers.
One nerve fiber and the muscle fibers it supplies constitute a motor unit.
The strength of the contraction depends on the number of motor units in
action at a particular time.

31. Mechanism Of Skeletal Muscle Contraction
The skeletal muscle cell contracts in response to stimulation from a nerve fiber, which
supplies the muscle cell usually about halfway along its length.
The name given to a synapse between a motor nerve and a skeletal muscle fiber is the
neuromuscular junction.
An action potential travels along a motor nerve to its ending on muscle fiber where the
nerve secretes a small amount of neurotransmitter substance acetylcholine.
The acetylcholine acts on the muscle fiber membrane to open multiple “acetylcholine
gated” channels which allows large quantity of sodium to diffuse to interior of muscle
fiber membrane. This initiates an action potential at the membrane.
When the action potential spreads from the nerve along the sarcolemma, it is
conducted deep into the muscle cell through a special network of channels that run
through the sarcoplasm, and releases calcium from the intracellular stores.

32. Mechanism Of Skeletal Muscle Contraction
Calcium triggers the binding of myosin to the actin filament next to it, forming so-called
cross-bridges.
ATP then provides the energy for the two filaments to slide over each other, pulling the Z
lines at each end of the sarcomere closer to one another, shortening the sarcomere. This
is called the sliding filament theory.
If enough fibers are stimulated to do this at the same time, the whole muscle will shorten
(contract).
The muscle relaxes when nerve stimulation stops. Calcium is pumped back into its
intracellular storage areas, which breaks the cross-bridges between the actin and myosin
filaments.
They then slide back into their starting positions, lengthening the sarcomeres and
returning the muscle to its original length.

33. Contraction Of Skeletal Muscle

34. Which of the events below is the FIRST to occur prior to a muscle cell contracting?
A. ATP binds to myosin.
B. ADP detaches from myosin.
C. the active site on actin is exposed.
D. Ca ++ is released from the sarcoplasmic reticulum.
What is the protein of thick myofilaments in a skeletal muscle cell?
A. tropomyosin
B. myosin
C. actin
D. Acetylcholine
The part of a skeletal muscle cell that is able to contract is called
A. sarcoplasm
B. sarcolemma
C. sarcomere
D. sarcoplasmic reticulum

35. Types Of Skeletal Muscle fibers:
From morphological, histochemical and functional point of view
• Red muscle fiber
• White muscle fiber

36. Red Muscle fibers
Rich in myoglobin and cytochrome, hence red in color
Narrow in diameter with less defined striation and nucleus are not always placed
at the periphery
Volume of sarcoplasm more than myofibrils.
Sarcoplasm contains more glycogen
Numerous mitochondria but sarcoplasmic reticulum less extensive
Slow and continuous contraction
Not easily fatigued
Rich blood supply
Predominate in postural muscles which have to remain contracted over long
period

37. White muscle fibers
Less myoglobin and cytochrome hence white in color
Broader in diameter with well defined striation and nucleus placed at periphery
Volume of myofibrils is more
Sarcoplasm contains less glycogen
Few mitochondria with extensive sarcoplasmic reticulum
Rapid contraction
Easily fatigued
Poor blood supply
Predominate in muscles responsible for sharp active movements

38. Smooth muscle
Spindle shaped cells
Central, oval elongated nucleus
Length highly variable
No transverse striation
Aggregated to form bundles
Delicate fibers holds the myocytes together

39. Contraction of smooth muscle
Need very little ATP for contraction
Actin and myosin form bundles that
are attached to both ends
When muscle contract these points are
drawn together
Elongated muscle cell converted to oval.

40. Distribution of smooth muscle
Walls of hollow visceras:
Stomach, intestine, urinary bladder, uterus
Walls of tubes:
Arteries, veins, bronchi, ureter, vas deferens, uterine tube,
tube of several glands
Muscle that constrict and dilate pupil
Skin- arrector pilli
Upper eyelid- muller’s muscle
Skin of scrotum- dartos muscle
Orbit- orbitalis

41. Cardiac muscle
Microscopic structure
Centrally placed nucleus
Transverse striation
Perinuclear halo
Intercalated disc
Branched fibers
Blood vessels seen

42. Similarities between skeletal and cardiac muscle
Made up of elongated fibers with numerous myofibrils
Myofibrils show transverse striation
A, I, H and Z band are made in the striation
Made up of actin and myosin filaments.

43. Differences Between Skeletal, Cardiac And Smooth Muscles
characteristics Skeletal muscle Cardiac muscle Smooth muscle
Muscle fiber Long, cylindrical and
unbranched
Long, cylindrical and
branched
Spindle shaped and
unbranched
Control Voluntary Involuntary Involuntary
Location Muscles of skeleton, tongue,
esophagus, diaphragm
Heart Vessels, organs and viscera
Striations Present(well defined) Present(ill defined) Absent
Nuclei Multiple, flat, at periphery Single, oval, in center Single, elongated, in center
Intercalated Disc Absent Present Absent
Regeneration (after injury) Seen(limited) Not seen Seen
Nerve supply Somatic nerve Autonomic nerve Autonomic nerve
Blood supply Rich Rich Poor
Energy demand High and at a time High and constantly Less and constantly
Contraction Rapid Rhythmic Slow sustained
Fatigue Fatigues easily Never fatigues Fatigues slowly

44. What characteristic of a smooth muscle cell distinguishes it from cardiac and from
skeletal muscle?
A. being branched
B. being under involuntary control
C. lack of striations
D. being uninucleate
Which feature is shared by cardiac muscle cells and skeletal muscle cells?
A. striations
B. intercalated discs
C. branching
D. involuntary nature
Smooth muscle is different from skeletal muscle because smooth muscle
A. is found in the walls of arteries
B. can be voluntarily contracted
C. has many nuclei in a cell
D. has intercalated discs between cells

45. Muscles Of Face And Neck
Face:
Occipitofrontalis
Levator Palpabrae Superioris
Orbicularis Oculi
Buccinator
Orbicularis Oris
Masseter
Temporalis
Pterygoid
Neck:
Sternocleidomastoid
Trapezius

46. Muscles Of Back
Trapezius
Teres Major
Psoas
Latissimus Dorsi
Quadratus Lumborum
Sacrospinalis

47. Muscles Of Abdominal Wall
Rectus Abdominis
External Oblique
Internal Oblique
Transversus Abdominis
Quadratus Lumborum
Psoas

48. Muscles Of Mastication
Temporalis
Masseter
Lateral Pterygoid
Medial Pterygoid

49. Muscles Of Facial Expression
Smiling And Laughing: Zygomaticus Major
Sadness: Levator Labi Superioris, Levator Anguli Oris
Grief: Depressor Anguli Oris
Anger: Dilator Naris And Depressor Septi
Frowning: Corrugator Supercilli And Procerus
Horror, Terror And Fright: Platysma

50. Muscles Of Facial Expression
Surprise: Frontalis
Doubt: Mentalis
Grinning: Risorius
Contempt: Zygomaticus Minor
Closing The Mouth: Orbicularis Oris
Whistling: Buccinators And Orbicularis Oris

52. The muscles involved in mastication include which of the following?
A. sternocleidomastoid, scalene
B. sartorius, gracilis, soleus
C. temporalis, masseter, pterygoid
D. orbicularis oculi, mentalis
Which of the following muscles is a common intra-muscular injection site?
A. deltoid
B. gluteus maximus
C. vastus medialis
D. latissimus dorsi