2. Skeletal Muscle
The skeletal muscle is associated with the
bones, thus forming skeletal muscle system in
body.
Features of skeletal muscle
STRIATED MUSCLE
MULTI NUCLEATED
VOLUANTRY MUSCLE
REGENERATION
LOCATION
4. EXCITABILITY
• The excitability of skeletal muscle
refers to its ability to respond to
stimuli and generate action potentials.
5. CONDUCTIVITY
The conduction of action potential occurs in the same way as in an unmyelinated
Fibre.
The action potential propagates along the sarcolemma.
Action potential spread in both direction from the point of stimulation.
EXTENSIBILITY
• Skeletal muscle extensibility
refers to the ability of a
muscle to stretch or lengthen
without damage.
6. Elasticity
The elasticity of skeletal muscle refers to its ability to return
to its original length and shape after it has been stretched
or contracted.
When a skeletal muscle is stretched, the myofibrils within
the muscle fibers are pulled apart, which increases the
length of the muscle. The elastic properties of the muscle
fibers and connective tissue within the muscle allow it to
resist this stretch, and when the stretching force is released,
the muscle returns to its original length.
7. CONTRACTILITY
Skeletal muscle is capable of
generating force and shortening in a
process called muscle contraction.
This process is enabled by the sliding
of actin and myosin filaments within
the muscle fibers,explained by the
sliding filament theory
11. SMOOTHMUSCLE
GENERAL FEATURES
Involuntary muscle
Unstriated muscle/ Plain muscle
It is small and spindle shaped
Contain Few mitochondria
Poorly developed sarcoplasmic reticulum
T Tubules are absent instead of this Caveolae is present
Thin filament lack Troponin
Two types: 1). Single unit smooth muscle
2). Multi unit smooth muscle
12. SINGLE UNIT/VISCERAL
SMOOTH MUSCLE
Syncytial nature
Most common site: wall of
hollow viscera
Active tension produced upon
stretch
Rhythmic contraction and
relaxation
MULTI UNIT SMOOTH
MUSCLE
Non-syncytial nature
Most common site : iris, ciliary
body muscle of eye
No response upon stretch
Irregular tetanic contraction
13. VISCERAL SMOOTH MUSCLE
ELECTRICAL PROPERTIES :
1) Instability of Membrane Potential :-
Membrane potential has no true “resting” value, being relatively low when
tissue is active and higher when it is inhibited.
2) Initiation of Spontaneous Activity :-
It begins with Ca ion influx (mainly) and due to Na ion influx.
14. MECHANICAL PROPERTIES
Tone : It shows continuous irregular contractions that are
independent of its nerve supply. This maintained state of
partial contractions is called Tone.
LATCH BRIDGE MECHANISM : Maximum force of
contraction is often greater than that of skeletal muscle due
to prolonged period of attachment of myosin cross bridge to
actin filament, called latch bridge mechanism.
15. Nerve Supply to Smooth muscle :
It receives dual nerve supply from two divisions of ANS i.e. Adrenergic nerve and
Cholinergic nerve
Excitatory Junctional Potential :
In smooth muscle in which adrenergic discharge is excitatory, stimulation of
adrenergic nerve produces discrete partial depolarization called EJP.
Denervation Hypersensitivity :
It is sharp increase of sensitivity of postsynaptic membrane to chemical
transmitter after denervation.
Cause :- Up- Regulation
16. Effect of Various agents on the membrane
potential of intestinal smooth muscle:
1. Effect of Catecholamines: Epinephrine & Nor Epinephrine act via both α & β adrenergic receptors
a. Via α, increase Ca2+ efflux
b. Via β, stimulates cAMP
a & b cause:
• Increase in membrane potential
• Decrease in spike frequency
2. Effect of Acetyl Choline: Increase in Na+ & Ca2+ influx
This causes decrease in membrane potential and increase in spike frequency.
3. Effect of Ions:
i. Ca2+: Increase in ECF- Increases spontaneous muscle contraction
ii. Barium: Direct stimulant
iii. Sodium: No effect
19. Excitability
• Excitability is defined as Ability of cardiac muscle to give response to a stimulus.
Action Potential:
• Action potential in a single cardiac muscle fibre occurs in
following phases-
1.PHASE 0: RAPID DEPOLARIZATION
REPOLARISATION OCCUR IN THREE PHASES
2.PHASE 1
3.PHASE 2
4.PHASE 3
5.PHASE 4: POLARISED STATE
20. Autorhythmicity
• Property of electrically active
cells that show rhythmic
activity without any external
stimulation.
• The property of the
autorhythmicity present in
all the tissue of the heart.
21. Conductivity
• Human heart has a specialized conductive system through which the impulse
from SA Node transmitted to all other part of the heart.
• Conductive system in human heart: Conductive system of human heart is
formed by modified cardiac muscle fibre.
• These fibres are the specialized cells which conduct impulse from SA Node
to Ventricle.
• The conductive system of human heart comprises:
1. AV Node
2. Bundle of His
3. Right & Left bundle branch
4. Purkinje Fibres
22.
23. Contractility
• Contractility is the ability of tissue to shorten in length after receiving a stimulus.
• Various factor affecting contractile property of cardiac muscle:-
1. All or None Law
2. Staircase phenomenon
3. Refractory period
All or None Law: According to this law, when a
stimulus applied whatever may be the strength,
the whole cardiac muscle gives maximum
response or does not give any response at all.
24. • Staircase Phenomenon: When continuous stimulus of same strength is given to resting
muscle of heart, it will show contractions and these contractions will gradually increase
and after some time they will remain same.
25. Refractory period:
Refractory period is the period in which the muscle does not show any response to a stimulus.
It is of two types:
1. Absolute Refractory Period
2. Relative Refractory Period
