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106921970 reviewer muscular

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MUSCULAR SYSTEM
FUNCTIONS:
1. Movement of the body contraction of Skeletal
muscles
2. Maintenance of posture Skeletal muscles
3. Respiration muscles of the Thorax
4. Production of body heat by-product of
Skeletal muscle contraction
5. Communication Skeletal muscles
6. Constriction of Organs & Vessels Smooth
muscles
- Help propel & mix food & water in the
digestive tract, propel secretions from
organs, regulate blood flow through vessels
7. Contraction of the Heart Cardiac muscles
CHARACTERISTICS OF SKELETAL MUSCLE
Skeletal muscle striated muscle
with associated Connective tissue constitutes
40% of body weight
Striations of Muscle fibers transverse bands
- Alternating I & A bands of Sarcomeres
4 Major functional characteristic:
- Contractility muscles shorten forcefully
during contraction
1. Lengthen passively by either gravity or
the contraction of an opposing muscle
- Excitability response to stimulus (usually
from nerves that we consciously control)
- Extensibility can be stretched to their
normal resting length & beyond to a limited
degree, after contraction
- Elasticity recoil to original resting length
after being stretched
Skeletal Muscle Structure
Connective Tissue coverings of Muscle
Epimysium muscular fascia
- Connective tissue sheath surrounding
Skeletal muscle
Muscle fasciculi numerous visible bundles that
composed Muscle
Perimysium Loose connective tissue that
surrounds Muscle fascicule
Muscle fiber several Muscle cells composing
muscle fasciculus
Endomysium Loose connective tissue that
surrounds Muscle fiber
Muscle Fiber Structure
Muscle fiber single cylindrical fiber
- Several Nuclei on its periphery
- 30cm long & 0.15mm in diameter largest
human muscle fiber
Sarcolemma cell membrane of Muscle fiber
- Where the multiple Nuclei of the muscle
fiber are located, deeply
Transverse tubules tubelike invanginations
along the surface of the Sarcolemma
- Occur at regular intervals along the Muscle
fiber & extend inward into it
Sarcoplasmic reticulum highly-organized
Smooth endoplasmic reticulum
- Connector of T tubules & Sarcolemma
- High concentration of Ca
+2
major role in
muscle contraction
Sarcoplasm the Cytoplasm in each Muscle
fiber
Myofibrils inside the Cytoplasm
- Threadlike structures that extend from one
end of the Muscle fiber to the other
- With 2 Major kinds of Protein Fibers Actin
& Myosin myofilaments
Sarcomeres arrangement of Actin & Myosin
myofilaments
- Repeating units along the myofibril
Actin & Myosin Myofilaments
Actin myofilaments thin filaments
- 3 components Actin, Troponin,
Actin resemble two minute strands of pearls
twisted together
- Attachment site for Myosin myofilaments
Troponin molecules- attached at specific
intervals along the Actin myofilaments
- Have binding sites for Ca
+2

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Tropomyosin filaments located along the
groove bet. the twisted strands of Actin
subunits
- Block the Myosin myofilament binding sites
on the Actin myofilaments in an
Unstimulated muscle no Ca
+2
present
- Bind to Troponin, Tropomyosin filaments
expose the attachment sites on the Actin
myofilaments with Ca
+2
Myosin myofilaments thick myofilaments
Myosin heads part of the Myosin that
resemble golf club heads
- 3 important properties
1. Can bind to attachment sites on the
Actin myofilaments
2. Can bend & straighten during
contraction
3. Can break down ATP, releasing energy
Sarcomeres basic structural & functional unit of
Skeletal muscle
- Smallest portion capable of contracting
- Extends from one Z disk to another Z disk
Z disk network of Protein fibers forming an
attachment site for Actin myofilaments
Myofibril in banded appearance bec. of the
arrangement of Actin & Myosin in Sarcomeres
(Light) I band consists of Actin myofilaments
- Spans each Z disk
- Ends at the Myosin myofilaments
A band darker, central region in each
Sarcomere
- Extends the length of Myosin myofilaments
- Actin & Myosin overlap at some distance at
both ends of the A band
H zone second light zone
- Consists of Myosin myofilaments
M line dark- staining band
- Where Myosin myofilaments are anchored
in the center
Close association of Sarcomeres, T tubules,
Sarcoplasmic reticulum enables Nerve
stimulus to initiate contraction of the Muscle
fiber
Excitability of Muscle Fibers
Polarized cell membrane negatively charged
greater on the inside compared to the outside
Resting cell membrane potential charge
difference
- Occurs bec. of uneven distribution of ions
across the cell membrane
- Equilibrium in which the tendency of K
+
to
diffuse out of the cell is opposed by the
negative charges inside the cell
- Develops for 3 reasons:
1. Concentration of K
+
inside the cell
membrane is higher than outside
2. Concentration of Na
+
outside the cell
membrane is higher than inside
3. Cell membrane is more permeable to K
+
than it is to Na
+
K
+
its leak channels are found mostly in
excitable cells, K
+
leak out faster than Na
+
- Positively-charged so movement from
inside to outside the cell (to diffuse
concentration gradient) causes the inside of
the cell to become even more negatively
charged
- Diffuse down their concentration gradient
only until the charge difference across the
cell membrane is great enough to prevent
any additional diffusion of K
+
out of the cell
Negatively-charged molecules “trapped”
inside the cell ex. Proteins
Sodium-Potassium pump maintains uneven
distribution of Na
+
& K
+
- Transports K
+
from outside to inside the cell
- Transports Na
+
from inside to outside the
cell
Stimulation of Muscle fiber or Nerve cell
causes Na
+
channels to open quickly & the
membrane to become very permeable to Na
+
- Concentration is greater outside the cell
- Charge inside the cell is negative
- Depolarization - inside of cell become more
positive than outside
Near the end of Depolarization Na
+
channels
close & additional K
+
channels open
- Tendency for Na
+
to enter the cell decreases
& K
+
to leave the cell increases cause the

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MUSCULAR SYSTEM FUNCTIONS: 1. Movement of the body – contraction of Skeletal muscles 2. Maintenance of posture – Skeletal muscles 3. Respiration – muscles of the Thorax 4. Production of body heat – by-product of Skeletal muscle contraction 5. Communication – Skeletal muscles 6. Constriction of Organs & Vessels – Smooth muscles - Help propel & mix food & water in the digestive tract, propel secretions from organs, regulate blood flow through vessels 7. Contraction of the Heart – Cardiac muscles CHARACTERISTICS OF SKELETAL MUSCLE • • • Muscle Fiber Structure • • • Skeletal muscle – striated muscle • • • with associated Connective tissue– constitutes 40% of body weight Striations of Muscle fibers – transverse bands - Alternating I & A bands of Sarcomeres 4 Major functional characteristic: - Contractility – muscles shorten forcefully during contraction 1. Lengthen passively by either gravity or the contraction of an opposing muscle - Excitability – response to stimulus (usually from nerves that we consciously control) - Extensibility – can be stretched to their normal resting length & beyond to a limited degree, after contraction - Elasticity – recoil to original resting length after being stretched Skeletal Muscle Structure Connective Tissue coverings of Muscle • • Epimysium – muscular fascia - Connective tissue sheath surrounding Skeletal muscle Muscle fasciculi – numerous visible bundles that composed Muscle Perim ...
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