Muscle Physiology Notes | EduRev

Created by: Stuti Nagpal

: Muscle Physiology Notes | EduRev

 Page 1


1
Muscle Physiology
Lecture Outline
• Muscle Function
• Muscle Characteristics
• Muscle Tissue Types
• Skeletal Muscle
– General Functions of Skeletal Muscle
– Functional Anatomy
– Physiology
– Skeletal Muscle Types
– Energetics
– Adaptive Responses
• Cardiac Muscle Physiology
• Smooth Muscle Physiology
Muscle Function
• Movement
– Depends on type of muscle tissue
– Depends on location of muscle tissue
• Thermogenesis
•Protection
• Posture Maintenance
• Joint Stabilization
Muscle Tissue Characteristics
All muscle tissues share basic characteristics
1.Excitability
2.Contractility
3.Elasticity
4.Extensibility
Page 2


1
Muscle Physiology
Lecture Outline
• Muscle Function
• Muscle Characteristics
• Muscle Tissue Types
• Skeletal Muscle
– General Functions of Skeletal Muscle
– Functional Anatomy
– Physiology
– Skeletal Muscle Types
– Energetics
– Adaptive Responses
• Cardiac Muscle Physiology
• Smooth Muscle Physiology
Muscle Function
• Movement
– Depends on type of muscle tissue
– Depends on location of muscle tissue
• Thermogenesis
•Protection
• Posture Maintenance
• Joint Stabilization
Muscle Tissue Characteristics
All muscle tissues share basic characteristics
1.Excitability
2.Contractility
3.Elasticity
4.Extensibility
2
Muscle Tissue Types
Skeletal
Cardiac
Smooth
Muscle Comparison Chart
Skeletal
Cardiac
Smooth
Cylindrical
Cylindrical 
& branched
Fusiform
Yes
Yes
No
Multi-
nucleate & 
peripheral
Uninucleate
& central
Uninucleate
& central
Voluntary
Involuntary
Involuntary
none
Intercalated 
discs
May be 
single-unit 
or multi-unit
Muscle 
Tissue Cell Shape Striae Nucleus Control
Special 
structures
Skeletal Muscle
General Functions - Voluntary
• Movement
– Only have contractility in one direction
• Requires multiple muscles 
to create movements from 
the simple
– flexion and extension
• To the complex
– Circumduction
• Stabilizing Movements & Joints
– The result of synergistic muscles
Skeletal Muscle
General Functions
•Protection
– of underlying structures
• abdominal viscera
– Stronger muscles = 
greater protection, 
increased joint stability
Page 3


1
Muscle Physiology
Lecture Outline
• Muscle Function
• Muscle Characteristics
• Muscle Tissue Types
• Skeletal Muscle
– General Functions of Skeletal Muscle
– Functional Anatomy
– Physiology
– Skeletal Muscle Types
– Energetics
– Adaptive Responses
• Cardiac Muscle Physiology
• Smooth Muscle Physiology
Muscle Function
• Movement
– Depends on type of muscle tissue
– Depends on location of muscle tissue
• Thermogenesis
•Protection
• Posture Maintenance
• Joint Stabilization
Muscle Tissue Characteristics
All muscle tissues share basic characteristics
1.Excitability
2.Contractility
3.Elasticity
4.Extensibility
2
Muscle Tissue Types
Skeletal
Cardiac
Smooth
Muscle Comparison Chart
Skeletal
Cardiac
Smooth
Cylindrical
Cylindrical 
& branched
Fusiform
Yes
Yes
No
Multi-
nucleate & 
peripheral
Uninucleate
& central
Uninucleate
& central
Voluntary
Involuntary
Involuntary
none
Intercalated 
discs
May be 
single-unit 
or multi-unit
Muscle 
Tissue Cell Shape Striae Nucleus Control
Special 
structures
Skeletal Muscle
General Functions - Voluntary
• Movement
– Only have contractility in one direction
• Requires multiple muscles 
to create movements from 
the simple
– flexion and extension
• To the complex
– Circumduction
• Stabilizing Movements & Joints
– The result of synergistic muscles
Skeletal Muscle
General Functions
•Protection
– of underlying structures
• abdominal viscera
– Stronger muscles = 
greater protection, 
increased joint stability
3
Skeletal Muscle
General Functions - Involuntary
• Shivering Thermogenesis (shivering reflex)
– asynchronous & involuntary 
– Initiated by hypothalamic nuclei 
in the primary motor center for 
shivering (posterior nuclei)
• Normally inhibited by the heat center 
in the hypothalamus (preoptic nuclei)
when body temp is in range (96.8-99.5)
– Receives cold signals from skin 
and spinal cord
-
-
Skeletal 
Muscle
preoptic 
nucleus
posterior
nucleus
Damage to the posterior 
nuclei would cause?
Skeletal Muscle
General Functions - Involuntary
• Maintenance of Posture
– Involves stretch reflexes
• Static reflexes
– Long term sustained contractile events
• Phasic reflexes
– Dynamic and short term corrective responses
• Regulated by gamma neurons which adjust 
tension in the muscle spindles
Skeletal Muscle
Functional Anatomy
Skeletal Muscle
Functional Anatomy
Page 4


1
Muscle Physiology
Lecture Outline
• Muscle Function
• Muscle Characteristics
• Muscle Tissue Types
• Skeletal Muscle
– General Functions of Skeletal Muscle
– Functional Anatomy
– Physiology
– Skeletal Muscle Types
– Energetics
– Adaptive Responses
• Cardiac Muscle Physiology
• Smooth Muscle Physiology
Muscle Function
• Movement
– Depends on type of muscle tissue
– Depends on location of muscle tissue
• Thermogenesis
•Protection
• Posture Maintenance
• Joint Stabilization
Muscle Tissue Characteristics
All muscle tissues share basic characteristics
1.Excitability
2.Contractility
3.Elasticity
4.Extensibility
2
Muscle Tissue Types
Skeletal
Cardiac
Smooth
Muscle Comparison Chart
Skeletal
Cardiac
Smooth
Cylindrical
Cylindrical 
& branched
Fusiform
Yes
Yes
No
Multi-
nucleate & 
peripheral
Uninucleate
& central
Uninucleate
& central
Voluntary
Involuntary
Involuntary
none
Intercalated 
discs
May be 
single-unit 
or multi-unit
Muscle 
Tissue Cell Shape Striae Nucleus Control
Special 
structures
Skeletal Muscle
General Functions - Voluntary
• Movement
– Only have contractility in one direction
• Requires multiple muscles 
to create movements from 
the simple
– flexion and extension
• To the complex
– Circumduction
• Stabilizing Movements & Joints
– The result of synergistic muscles
Skeletal Muscle
General Functions
•Protection
– of underlying structures
• abdominal viscera
– Stronger muscles = 
greater protection, 
increased joint stability
3
Skeletal Muscle
General Functions - Involuntary
• Shivering Thermogenesis (shivering reflex)
– asynchronous & involuntary 
– Initiated by hypothalamic nuclei 
in the primary motor center for 
shivering (posterior nuclei)
• Normally inhibited by the heat center 
in the hypothalamus (preoptic nuclei)
when body temp is in range (96.8-99.5)
– Receives cold signals from skin 
and spinal cord
-
-
Skeletal 
Muscle
preoptic 
nucleus
posterior
nucleus
Damage to the posterior 
nuclei would cause?
Skeletal Muscle
General Functions - Involuntary
• Maintenance of Posture
– Involves stretch reflexes
• Static reflexes
– Long term sustained contractile events
• Phasic reflexes
– Dynamic and short term corrective responses
• Regulated by gamma neurons which adjust 
tension in the muscle spindles
Skeletal Muscle
Functional Anatomy
Skeletal Muscle
Functional Anatomy
4
Skeletal Muscle
Functional Anatomy
Skeletal Muscle
Functional Anatomy
• The smallest functional unit of skeletal 
muscle is the sarcomere
Skeletal Muscle
Functional Anatomy
• Sarcomere is composed of various 
microfilaments and supporting structures
• Titin
– largest known elastomeric protein
– Connects myosin to z-disc
– thought to be critical in the development of 
sarcomeres
Skeletal Muscle
Functional Anatomy
• Myosin molecule 
consists of tail, hinge 
and heads
– Heads contain active 
sites for
•Actin
•ATP
• M-line consists of 
myomesin and skelemin
proteins
– stabilize the myosin 
filaments
– theorized to aid in 
transmission of force 
from sarcomere to 
cytoskeletal intermediate 
filaments
Page 5


1
Muscle Physiology
Lecture Outline
• Muscle Function
• Muscle Characteristics
• Muscle Tissue Types
• Skeletal Muscle
– General Functions of Skeletal Muscle
– Functional Anatomy
– Physiology
– Skeletal Muscle Types
– Energetics
– Adaptive Responses
• Cardiac Muscle Physiology
• Smooth Muscle Physiology
Muscle Function
• Movement
– Depends on type of muscle tissue
– Depends on location of muscle tissue
• Thermogenesis
•Protection
• Posture Maintenance
• Joint Stabilization
Muscle Tissue Characteristics
All muscle tissues share basic characteristics
1.Excitability
2.Contractility
3.Elasticity
4.Extensibility
2
Muscle Tissue Types
Skeletal
Cardiac
Smooth
Muscle Comparison Chart
Skeletal
Cardiac
Smooth
Cylindrical
Cylindrical 
& branched
Fusiform
Yes
Yes
No
Multi-
nucleate & 
peripheral
Uninucleate
& central
Uninucleate
& central
Voluntary
Involuntary
Involuntary
none
Intercalated 
discs
May be 
single-unit 
or multi-unit
Muscle 
Tissue Cell Shape Striae Nucleus Control
Special 
structures
Skeletal Muscle
General Functions - Voluntary
• Movement
– Only have contractility in one direction
• Requires multiple muscles 
to create movements from 
the simple
– flexion and extension
• To the complex
– Circumduction
• Stabilizing Movements & Joints
– The result of synergistic muscles
Skeletal Muscle
General Functions
•Protection
– of underlying structures
• abdominal viscera
– Stronger muscles = 
greater protection, 
increased joint stability
3
Skeletal Muscle
General Functions - Involuntary
• Shivering Thermogenesis (shivering reflex)
– asynchronous & involuntary 
– Initiated by hypothalamic nuclei 
in the primary motor center for 
shivering (posterior nuclei)
• Normally inhibited by the heat center 
in the hypothalamus (preoptic nuclei)
when body temp is in range (96.8-99.5)
– Receives cold signals from skin 
and spinal cord
-
-
Skeletal 
Muscle
preoptic 
nucleus
posterior
nucleus
Damage to the posterior 
nuclei would cause?
Skeletal Muscle
General Functions - Involuntary
• Maintenance of Posture
– Involves stretch reflexes
• Static reflexes
– Long term sustained contractile events
• Phasic reflexes
– Dynamic and short term corrective responses
• Regulated by gamma neurons which adjust 
tension in the muscle spindles
Skeletal Muscle
Functional Anatomy
Skeletal Muscle
Functional Anatomy
4
Skeletal Muscle
Functional Anatomy
Skeletal Muscle
Functional Anatomy
• The smallest functional unit of skeletal 
muscle is the sarcomere
Skeletal Muscle
Functional Anatomy
• Sarcomere is composed of various 
microfilaments and supporting structures
• Titin
– largest known elastomeric protein
– Connects myosin to z-disc
– thought to be critical in the development of 
sarcomeres
Skeletal Muscle
Functional Anatomy
• Myosin molecule 
consists of tail, hinge 
and heads
– Heads contain active 
sites for
•Actin
•ATP
• M-line consists of 
myomesin and skelemin
proteins
– stabilize the myosin 
filaments
– theorized to aid in 
transmission of force 
from sarcomere to 
cytoskeletal intermediate 
filaments
5
• Thin filaments are composed of
– g-actin molecules in 
a helical arrangement
• Contain myosin binding 
sites
– nebulin
• Filament that forms
internal support and
attachment for actin
– tropomyosin filaments
– troponin molecules 
attached to tropomyosin
• Has binding sites for Ca
2+
Skeletal Muscle
Functional Anatomy
Skeletal Muscle
Functional Anatomy
• The Z-disc
– Anchors the filaments and interacts with 
cytoskeletal framework
Skeletal Muscle
Functional Anatomy
• Transmission of force from the sarcomere 
to the tissue at large
– Sarcomeres linked by 
distrophin to sarcolemma, 
then via membrane 
proteins interacting with 
cytoskeletal framework
Muscular Dystrophy?
Skeletal Muscle
Physiology of Contraction
• How does all this functional anatomy 
work?
–1
st
– synaptic transmission at the  
neuromuscular junction
–2
nd
– excitation-contraction coupling
–3
rd
– contraction-relaxation cycle
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