Muscle and its Physiology for Ist Bpharm Sem-I

1. HUMAN ANATOMY AND PHYSIOLOGY NOTES
RAMDAS BHAT
KARAVALI COLLEGE OF PHARMACY 1
CHAPTER NO:5
Skeletal muscle and its
Physiology
Prepared by,
RAMDAS BHAT
Asst. Professor
Karavali college of Pharmacy
Mangalore
7795772463
Ramdas21@gmail.com

2. HUMAN ANATOMY AND PHYSIOLOGY NOTES
RAMDAS BHAT
KARAVALI COLLEGE OF PHARMACY 2
• Human body contains over 400 skeletal muscles
• 40-50% of total body weight
• Functions of skeletal muscle
• Force production for locomotion and breathing
• Force production for postural support
• Heat production during cold stress
STRUCTURE OF SKELETAL MUSCLE AND ITS CONNECTIVE TISSUE COVERING:
1. Epimysium
• Surrounds entire muscle
2. Perimysium
• Surrounds bundles of muscle fibers (Fascicles)
3. Endomysium
• Surrounds individual muscle fibers
SKELETAL MUSCLE

3. HUMAN ANATOMY AND PHYSIOLOGY NOTES
RAMDAS BHAT
KARAVALI COLLEGE OF PHARMACY 3
Skeletal Muscle Fibers
• Each muscle fiber is a single, long, cylindrical muscle cell.
• Sarcolemma-cell membrane
• Sarcoplasm-cytoplasm with many mitochondria and nuclei; has myofibrils. Myofibrils are
separated into compartments called sarcomeres that contain thick filaments and thin
filaments.
• Thick filaments of myofibrils are made up of the protein myosin.
• Thin filaments of myofibrils are made up of the protein actin.
• The organization of these filaments produces striations.
• A sarcomere extends from Z line to Z line.
• I bands also called as light bands made up of actin anchored to Z lines
• A bands also called as dark bands made up of overlapping thick and thin filaments.
• In the center of A bands is an H zone, consisting of myosin filaments only.
• Beneath the sarcolemma of a muscle fiber lies the sarcoplasmic reticulum (endoplasmic
reticulum), which is associated with transverse (T)tubules (membrane channels) activate
the muscle contraction mechanism and Longitudinal(L) tubules that has bag like structure
at the ends stores Calcium that are bound to Calsequestrin and are released when T
tubules carries the impulses deep into the muscle fibres.
• 2 L tubules and 1 T tubules in a sarcomere is called as TRIAD.

4. HUMAN ANATOMY AND PHYSIOLOGY NOTES
RAMDAS BHAT
KARAVALI COLLEGE OF PHARMACY 4

5. HUMAN ANATOMY AND PHYSIOLOGY NOTES
RAMDAS BHAT
KARAVALI COLLEGE OF PHARMACY 5
SARCOTUBULAR SYSTEM:
• There are 2 types of Sacrcotubular system tubules
a) Transverse tubular system
b) Longitudinal tubular system
PHYSIOLOGY OF MUSCLE CONTRACTION:

6. HUMAN ANATOMY AND PHYSIOLOGY NOTES
RAMDAS BHAT
KARAVALI COLLEGE OF PHARMACY 6
• Neuromuscular junction contains an Axonal terminal of a neuron that forms the synapse
with the Muscle end plate.
• Axonal terminal has various channels and pumps that helps in the influx and efflux of the
ions in and out of the Axons.
• The resting membrane potential for an axon is -70mv ie. The neuron is at rest and there
is no electrical transmission inside the neuron and has the potential towards negative
side.
• When the muscle requires to contract the resting membrane potential with negative
charge moves towards the positive side and there will be stimulation of the muscle end
plate thus causing the muscle to contract.
• The brain sends the stimulation to a neuron and the axon of that neuron causes the
release of Neurotransmitter Acetylcholine.
• The release of the Neurotransmitter happens when there is an opening of the Sodium
channel.
• Sodium ion has the positive charge makes the Neuronal potential towards slight positive
charge ie. Sodium channel being slow channel causes slow influx of the sodium ie 2 ions
and thus makes the potential to reach Threshold potential ie -55mv.
• In order to release the neurotransmitter and for neuron to get excited the threshold
should be reached.
• Once the threshold is reached there is the opening of Calcium channel. Calcium adds up
soo many positive charges into the neuron makes the potential to reach +40mv and this
is termed as Depolarization (Against the Polarized state)
• Due to the influx of the Calcium, Calcium now binds to the Neurotransmitter vesicles that
are present at the axonal terminal. Calcium thus causes the degranulation of the vesicles
thus releasing the Neurotransmitter at the synapse.
• Released neurotransmitter acetyl choline comes and bind to the Nicotinic receptor
present on the muscle end plate.
• The stimulation of the receptor causes the impulses from the sarcolemma to move into
the Sarcomere through the Transverse tubular system (TTS).
• Once the TTS carry the impulses deeper into the muscles the TTS will stimulate
Longitudinal tubular system (LTS), under stimulation LTS will release calcium from their
storage cisternae and released calcium will move towards the Sarcomere where they are
utilized for the process of Muscle contraction.
• Calcium binding site present on the Troponin takes up the Ca2+ released by the LTS and
this calcium binding acts as a driving force for the mechanism of Sliding.
• Actin now binds to the Actin binding site over the myosin molecules and ATP that are the
product of Glycolysis will now bind to the ATP binding site over the Myosin and this causes
the actin to slide over the myosin head.
• Myosin being at rest will not move where only the Actin will slide over them and thus
causes the sliding mechanism.
• Once the actin slides over the one head of the myosin, Actin will move to next myosin
head and thus causes the Contraction of the Muscle.
• Once the muscle wants to stop the contraction, Excess of the sodium will be moving out
of the Neuron and potassium ie. 3 ions will move out and there is a blocking of Calcium
channel leading to increased negative charges inside the axonal terminal leading to a state
called as Repolarization (back to polarized state).

7. HUMAN ANATOMY AND PHYSIOLOGY NOTES
RAMDAS BHAT
KARAVALI COLLEGE OF PHARMACY 7
• Further release of the Neurotransmitter will be blocked and excess of Acetyl choline will
that are present in the Synapse will hydrolysed by Acetylcholinesterase that are present
in the skeletal muscle.
• Acetylcholinesterase will now break down the Acetylcholine into acetic acid and choline.
• Acetylcholine now will not be available to bind to Nicotinic receptor thus preventing the
muscle contraction.
• TTS will not get stimulated nor the LTS releases the Calcium, Excess calcium present in the
Sarcomere will be reuptake back by the Cisternae and thus Muscle sliding is inhibited
causing the fibers to relax.
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8. HUMAN ANATOMY AND PHYSIOLOGY NOTES
RAMDAS BHAT
KARAVALI COLLEGE OF PHARMACY 8
MUSCLES OF THE BODY:
Diseases/Disorders of muscles:
MUSCULAR DYSTROPHY
• Muscular dystrophy is a disease characterized by progressive degeneration of muscle
fibers, without the involvement of nervous system.
• Mostly it has a hereditary origin.
• The muscles fail to regenerate, resulting in progressive weakness and confinement to a
wheelchair. Eventually, death occurs.
HYPERTONIA
Hypertonia or hypertonicity is a muscular disease characterized by increased muscle tone and
inability of the muscle to stretch.
HYPOTONIA
Hypotonia is the muscular disease characterized by decreased muscle tone. The tone of the
muscle is decreased or lost.
MYOTONIA

9. HUMAN ANATOMY AND PHYSIOLOGY NOTES
RAMDAS BHAT
KARAVALI COLLEGE OF PHARMACY 9
• Myotonia is a congenital disease characterized by continuous contraction of muscle and
slow relaxation even after the cessation of voluntary act.
• The main feature of this disease is the muscle stiffness, which is sometimes referred as
cramps. Muscle relaxation is delayed.
FIBRILLATION
Fibrillation means fine irregular contractions of individual muscle fibers.
MYASTHENIA GRAVIS
• Myasthenia gravis is an autoimmune disease of neuromuscular junction caused by
antibodies to cholinergic receptors.
• It is characterized by grave weakness of the muscle due to the inability of neuromuscular
junction to transmit impulses from nerve to the muscle.
• It is a serious and sometimes a fatal disease.
McARDLE DISEASE
• McArdle disease is a glycogen storage disease (accumulation of glycogen in muscles) due
to the mutation of genes involving the muscle glycogen phosphorylase, necessary for the
breakdown of glycogen in muscles.
• Muscular pain and stiffness are the common features of this disease
MITOCHONDRIAL MYOPATHY
Mitochondrial myopathy is an inherited disease due to the defects in the mitochondria (which
provide critical source of energy) of muscle fibers.
MYALGIA
Pain in the muscle or muscle group.
MUSCULAR ATROPHY
Wasting of the Muscle or loss of muscle tissue is termed as Muscular Atrophy.