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Functional Organization of the Muscular System, นางสาวอารียา ตุ่นกระโทก …
Functional Organization
of the Muscular System
Skeletal Muscle Cells
Structure:
Striated
Large, long, and cylindrical cell
Many periphery nuclei
Function:
Moves the body; is under
voluntary (conscious) control
Location:
Attached to bone or other connective
tissue
Structure of A Skeletal Muscle
Skeletal muscle tissue
Nervous tissue
Blood
Connective tissues
Organization of Skeletal Muscle Fibers
Thick and thin myofilaments
Myofibrils
Mitochondria
Sarcoplasmic reticulum
Triads
Neuromuscular junction
Presynaptic terminal:
Terminal axon synapses with
muscle fiber at sarcolemma
Synaptic cleft:
Area between axon terminal and
sarcolemma of muscle fiber
Postsynaptic membrane or
motor end-plate:
Membrane of muscle fiber Within
synapses
Motor Unit
: Each skeletal muscle fiber is innervated
by a single axon from a motor neuron.
As few as four fibers
As many as 1000’s of muscle fibers
Skeletal Muscle Composition
and Actions
Origin and Insertion
Origin :
The less moveable
attachment of a muscle
Insertion:
The more moveable
attachment of the
muscle
Organizational of
Muscle Fibers.
four basic patterns:
■ circular
■ parallel
■ convergent
■ pennate
Actions of Skeletal
Muscles
An Agonist:
Chiefly movement
An Antagonist :
Action opposed agonist
A Synergist:
Help agonist
Types of Skeletal Muscle fibers
Slow Fibers
▹Endurance
▪ Trunk & Lower limb muscles
▪ Maintaining posture,marathon
running
Intermediate Fibers
▹ Medium duration,
moderate movement
▪ Lower limb musces
▪ Walking , biking
Fast Fibers
▹ Short duration,
intense movement
▪ Extrinsic eye muscles
▪ Eye movements
Smooth Muscle Cells
Structure:
No striated
Tapered at each end
A single nucleus
Function:
Regulates the size of organs ; is
under involuntary (unconscious)
control
Location:
In hollow organs
Cardiac Muscle Cells
Structure:
Cylindrical and striated
Intercalated disks
Centrally located nucleus
Function:
Pumps the blood; is under
involuntary (unconscious) control
Location:
In the heart
Properties of Muscle
Excitability
Muscle cells are very responsive to
input from stimuli.
Contractility
Stimulation of muscle cells generates
tension within the cell.
Elasticity
A contracted muscle cell recoils to its
resting length when the applied tension is removed
Extensibility
A muscle cell must be capable of
extending in length in response to the
contraction of opposing muscle cells.
Muscular System Functions
Body movement
Maintenance of posture
Respiration
Production of body heat
Constriction of organs and vessels
Heart beat
T
ypes of Muscle Contraction
1. Isotonic contraction
: muscle contracts and changes length
1.1. Concentric – shortening contraction
1.2. Eccentric – lengthening contraction
Muscle tension is greater than the resistance.
The muscle shortens (concentric) or lengthens
(eccentric), and movement occurs.
2. Isometric contraction
: muscle contracts
but does not change length
Muscle tension is less than the resistance.
Although tension is generated.
Muscle does not shorten, and no movement occurs.
skeletal
Muscles Naming
Muscle Action
Adductor (adducts body part)
▸ Adductor longus (Al)
Flexor (flexes a joint)
▸ Flexor carpi radialis
Specific Body Regions
Anterior (toward the
front of the body)
▸ Tibialis anterior (Ta)
Around the cranium
▸ Epicranius (a)
Muscle attachments
Sternum and clavicle (cleido)
▸Sternocleidomastoid (a)
Zygomatic bone
▹ Zygomaticus major
Orientation of the
muscle fibers
Oblique (angled)
▹ External oblique (Eo)
Orbicularis (circular)
▹ Orbicularis oculi
Muscle shape
Rhomboid (rhomboidal)
▹ Rhomboid major (a)
Deltoid (triangular)
▹ Deltoid (b)
Muscle size
Major (larger of two muscles)
▹ Pectoralis major (Pm)
Minimus (smallest)
▹ Gluteus minimus
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