Muscles (KT) Flashcards
The scientific study of muscles
Myology
How much total body mass does muscle account for?
45%- responsible for most of the work generated by the body
Functions of Muscles (5)
- Maintain posture and body position
- Movement
- Heat production
- Guard orifices
- Support visceral organs
Properties of Muscle Tissue (4)
- Excitability
- Contractility
- Extensibility
- Elasticity
The ability to receive and respond to electrical or chemical stimuli
Excitability
The ability to shorten forcibly when stimulated
Contractility
The ability to be stretched without damaging the tissue
Extendibility
The ability to return to original shape after being stretched
Elasticity
Muscle composition (5)
Muscles are organs… The consist of…
- Connective Tissue
- Arteries/Veins
- Nerves
- Lymphatics
- Contractile muscle cells
Skeletal Muscle Characteristics (7)
- Attaches to bone, skin, or fascia
- Striated with light and dark bands
- Voluntary control
- Long, thin, and multinucleate fibers
- Arranged into packages that attach to and cover the bony skeleton
- Contracts rapidly, but tire easily
- Exert great force
Fiber= 1 muscle cell
The main portion of a muscle
Belly/Gaster
Where is the belly of the muscle attached?
Belly is attached to tendons, and then tendons are attached to bones
- Dense irregular connective tissue that is around muscle
- Holds it in place and separates it from other muscles
Deep Fascia
- Loose connective tissue beneath skin
- Surrounds several muscles
Subcutaneous Fascia
How are skeletal muscles organized? (General)
- Many muscle fibers are bundled together into groups called fascicles
- 10-100 muscles fibers per fascicles
- Several fascicles make up a muscle
Skeletal muscle connective tissue that surrounds the whole muscle
Epimysium
Skeletal muscle connective tissue that surrounds the fascicles
Perimysium
Skeletal muscle connective tissue that separates individual muscle fibers (cells)
Endomysium
All connective tissue extends beyond the muscle belly to form the….
Tendon
Tendons that from thick flattened sheets are called…
Aponeuroses
Embryonic cells that fuse to form muscle fibers… (this is why they are long and multinucleate)
Myoblasts
Myoblasts that do not fuse become…
Myosatellite cells
What is the function of Myosatellite cells?
Assist in repair of damaged cells
Fiber cytoplasm
Sarcoplasm
Plasma membrane in a fiber
Sarcolemma
Extensions of the sarcolemma into the sacroplasm
Transverse (T) Tubule
Contractile organelles that…
- Extend the length of fiber
- Surrounded by the sarcoplasmic reticulum
Myofibrils
- Surround the myofibrils
- Similar to the ER
- Contain calcium ions
Sarcoplasmic Reticulum
What is the functional unit of a myofibril
Sarcomere
What are the 2 components of sarcomeres?
- Thick Filaments
2. Thin Filaments
What is the component of Thick Filaments?
-Myosin
What is the component of myosin?
- Twisted protein with globular heads
- 1.6 um long
- 500 per thick filament
What are the components of Thin Filaments? (2)
- Actin
2. Regulatory Proteins
Components of Actin… (2)
- Structural Proteins
2. Coiled “beads”
Components and function of Regulatory Proteins… (3)
- Allow/Prohibit attachment between actin and myosin
- Tropomyosin
- Troponin
Cause the striated appearance
Sarcomere bands
What are the 4 kinds of sarcomere bands?
- A Band
- I Band
- H Band
- Zone of Overlap
Type of band that includes the entire thick filament range
A Band
Type of band that includes only thin filaments
I Band
Type of band that includes only thick filaments
H Band
Type of band that includes both filaments
Zone of Overlap
These structures divide and flank the sarcomere
Sarcomere Lines
What are the 2 types of sarcomere lines?
- Z line
2. M Line
This type of sarcomere line…
- Is at the end of the sarcomere
- Made of actinin protein
- Anchors thin filaments
Z Line
This type of sarcomere line…
- Is in the middle of the sarcomere
- Stabilizes thick filaments
M Line
Structural Protein that…
- Anchors a thick filament to a Z line
- Accounts for elasticity and extensibility
Titin
Structural Protein that…
-Holds the F actin together on
thin filaments
Nebulin
Structural Protein that…
-Makes up the Z line
Actinin
The process of the actin sliding over the myosin
Sliding Filament Theory
What happens during the Sliding filament theory? (5 steps)
- Zone of overlap enlarges
- H band shrinks
- I band shrinks
- A band remains the same
- The Z line moves closer to the A band
The 6 components of the neuromuscular junction
- Motor Unit
- Neuromuscular Junction
- Synaptic Terminal
- Motor end plate
- Synaptic cleft
- Neurotransmitters
Part of the neuromuscular junction that…
-Neuron + all the muscle cells stimulated by the neuron
Motor Unit
Part of the neuromuscular junction that…
-Point of contact between the neuron and the muscle
Neuromuscular Junction
Part of the neuromuscular junction that…
-End of the axon that contacts motor end plate
Synaptic Terminal
Part of the neuromuscular junction that…
-Point on the muscle fiber that contacts synaptic terminal
Motor End Plate
Part of the neuromuscular junction that…
-Gap between the neuron and the muscle
Synaptic Cleft
Part of the neuromuscular junction that…
- Chemical released into the synaptic cleft
- In this case it is acetylcholine
Neurotransmitter
Events of Muscle Contraction (9)
- Ach stored in the synaptic vesicles
- Impulse reaches end of the neuron–> Ach is released
- Ach crosses the gap and binds to the receptors
- Impulse travels through motor end plate down the T- tubules to the sarcoplasmic reticulum
- Ca+2 ions fiffuse out of the sarcoplasmic reticulum into the sarcoplasm
- Ca+2 exposes the active site
- Myosin then binds to active site
- ATP is used and contraction occurs
- Contraction continues as long as Ca+2 concentration is high
Events of Muscle Relaxation (5)
- Ach decomposed by acetylcholinesterase (AChe)
- Ca ions transported back to SR
- Actin and myosin links broken
- Cross bridges move back
- Active site is blocked once again
This is determined by the frequency of stimulation and the number of neurons stimulated
Tension
Tension in which…
-All fibers in a motor unit fully contract if stimulated
All or None Law
Tension in which…
-Steady increase in tension by increasing the number of contracting motor neurons
Recruitment
Tension in which…
- Muscle never begins to relax
- Continuous fused contraction
Tetanus
- Motor untis contract randomly
- Tension but no movement
Muscle Tone
Muscle tone can… (3)
- Stabilizes joints
- Holds objects in place
- Maintains posture
- Constant, exhaustive stimulation increases the number of organelles/proteins in a fiber
- Increases the overall enlargement of the muscle
Hypertrophy
Hypertrophy increases the number of… (4)
- Mitochondria
- Glycolytic enzyme reserves
- Myofibrils
- Filaments within myofibrils
During hypertrophy, muscle cells (do/do not) reproduce
DO NOT
The lack of constant motor neuron stimulation reduces organelles ad proteins
Atrophy
Atrophy can be due to… (4)
- Age
- Hormones
- Lack of use
- Nerve damage
* Is reversible as long as the fiber isn’t dead
Attachment site that doesn’t move
Origin
Attachment site that moves
Insertion
Tension=
Force
Fascicle arrangement varies based on…
Position of the muscle
- Fascicles parallel to long axis
- Unidirectional force
Parallel Muscles
Example of parallel muscles
Biceps brachii
- Fan shaped muscles
- Multidirectional force
- Versatility
- Generates least amount of force
Convergent Muscles
Example of Convergent Muscles
Pectoralis major
- Feather shaped muscle
- Fascicles oblique to long axis
- Tendon passes through the muscle
- Greatest force
Pennate Muscle
Example of pennate muscle
Deltoid
- Concentric fascicles around an opening
- Contraction decreases lumen diameter
Circular muscles
Example of circular muscles
Orbicularis oculi
-Rotation around one axis
Uniaxial
Uniaxial Movements
Rotation- atlantoaxial and pivot joints
Angular- knee and IP joints
Movement along 2 axes
Biaxial
Angular movement of biaxial articulations
Angular-
- flexion/extension
- Abduction/Adduction
Examples of biaxial Joints (4)
- Ellipsoidal Joint
- Radiocarpal
- Metacarpal Phalange
- Carpometacarpal (2-5)
Movement on all axes
Mutliaxial Movement
Multiaxial Movement
Angular-
- Flexion/Extension
- Abduction/Adduction
Rotation-
-Circumduction
Example of Multiaxial Movement
Ball and socket
- Main muscle causing directional force
- This can be any muscle of interest
Agonist
-Muscle that contracts to oppose agonist
Ex. Bicep brachii
Tricep brachii
Antagonist
-Muscle that assists/modifies movement
Ex. Brachialis and pronator teres
Synergist
-Muscle that stabilizes elements associated with agonist
Ex. Deltoid stabilizes glenohumeral joint
Fixator
This type of system modifies movement
Levers
Levers can change… (4)
- Magnitude of force
- Speed
- Direction
- Distance of limb movements
The 4 components of the Lever System…
- Lever (L)
- Effort (E)
- Fulcrum (F)
- Resistance (R)
Skeletal Element
Level
Applied force
Effort
Joint
Fulcrum
Body part or object moved
Resistance
3 types of levers
- First Class
- Second Class
- Third Class
Type of lever that…
-R opposite of E with central F
First Class
E, F, and R of neck extension
E- neck extensions
F- atlanto-occipital joint
R- Skull
Type of lever that…
- E is opposite of F to move R
- Example is plantar flexion
Second Class
E, F, and R of plantar flexion
E- calf
F- MP joint
R- Weight of body
Type of lever that…
- E is in between F and R
- Example is elbow flexion
Third Class
E, F, R of elbow flexion
E- biceps brachii
F- elbow joint
R- weight distal to joint
Types of Skeletal Muscle Fibers (3)
- Fast Fibers
- Slow Fibers
- Intermediate Fibers
Characteristics of Fast Fibers (7)
- Fast acting, high energy requirements
- Anaerobic
- Large diameter
- Densely packed myofibrils
- Large glycogen reserves
- Few mitochondria
- Rapid, powerful and brief contractions
Characteristics of Slow Fibers (5)
- More myoglobin, slower sustained contraction
- Aerobic
- Smaller diameter
- Longer to contract
- Contract for longer time
Characteristics of Intermediate Fibers
- Has attributes of both
- Similar to fast fibers
- Greater resistance to fatigue
- Exercise or lack of can change one muscle type to another
Smooth Muscle characteristics (7)
- Attached to hair follicles
- In walls of hollow organs and blood vessels
- Nonstriated
- Involuntary control
- Contractions are slow and sustained
- Spindle shaped
- Very elastic
Smooth muscles are stimulated by… (4)
- Nervous System
- Hormones
- Ions
- Stretching
Smooth muscle types (2)
- Single Unit
2. Multi Unit
-Many gap junctions
-Sheets of spindle shaped cell
-Contract together (syncytial contraction)
Ex. BV’s, digestive tract, resp. tract, and urinary tract
Single Unit
-Few/No gap junctions
-Separate fibers that contract independently
-Only contract when stimulated by motor nerve
Ex. walls of large BV’s, uterus, and iris of eye
Multi Unit
Characteristics of Cardiac Muscles
- striated in appearance
- involuntary control
- network of fibers with intercalated disks at the ends
- only found in heart
