Skeletal Muscle and Nerve Tissue Flashcards
Characteristics of Skeletal Muscle
Striated
Voluntary
Fatigable
Multinucleated (Peripheral)
Characteristics of Cardiac Muscle
Striated
Involuntary
Must NEVER Fatigue
Uninucleated (central)
Separated by Intercalated Discs
Characteristics of Smooth Muscle
Not Striated
Involuntary
Uninucleated (central)
Muscle Arrangement
Describe the arrangement of muscle
Muscle Cell (Myofiber/Myocyte/Muscle Fiber) made up of Myofibrils (Sarcomeres (contractile units of Actin and Myosin Myofilaments) linked together) surrounded by Endomysium
Fascicle is a group of Myofibers surrounded by Perimysium
Muscle is a group of Fascicles surrounded by Epimysium
Myosin (Thick Filaments)
Structure?
Held in place by what?
2 Heavy Chains w/ Globular Heads (Actin Binding Site with ATPase domains) & 2 Light Chains
Held in place by Titin proteins connected to Z-disk
Actin (Thin Filaments)
Structure?
What determines length of actin filament?
What wraps between actin strands?
What is Troponin?
F-actin monomers (globules) bound together forming double stranded chains
Nebulin
Tropomyosin (covers Myosin binding sites on actin filament)
Troponin sits on Tropomyosin strands
Sarcomere Components
M-Line
Z-Disk
H-Zone
A Band
I Band
Myosin attachment site in H-Zone
Separates sarcomeres; attachment site for Actin and Titin
Space on either side of M-Line where there is no Actin
Distance from end of one myosin head to the opposite Myosin head (overlap of Actin + Myosin and H-Zone)
Space on either side of Z-Disk where there is no Myosin (Only Actin)
Muscle Contraction
What steps must happen for contraction to occur?
Myosin must bind to Actin (Tropomyosin blocks Myosin binding sites)
Ca released from SR binds to Troponin causing conformational change of Tropomyosin (Myosin binding sites on Actin are now accessible)
Sliding Filament Mechanism
What is an overall process of the mechanism?
Timing of contractions?
Which segments change length?
- Thin Filaments (Actin) slide past Thick Filaments (Myosin)
- Z-Disks come closer together
- I Band & H-Zone Shorten
- All myofibrils in muscle contract at same time making entire muscle shorten
- Actin & Myosin DO NOT change in length, simply overlap each other
- A Band does not shorten
Type I Skeletal Muscle Fibers
Speed/Strength
Mitochondria
Myoglobin
Fatigability
Energy Production Method
Slow, less powerful contraction
Many mitochondria (Red)
Abundant myoglobin
Slow fatigability
Aerobic respiration
Type IIA Skeletal Muscle Fibers
Speed/Strength
Mitochondria
Myoglobin
Fatigability
Energy Production Method
Fast/Intermediate, powerful contraction
Many mitochondria (Red)
Many myoglobin
Intermediate fatigability
Aerobic respiration (less O2 delivery)
Type IIB Skeletal Muscle Fibers
Speed/Strength
Mitochondria
Myoglobin
Fatigability
Energy Production Method
Fast, powerful contraction
Few mitochondria
Few myoglobin
Rapid fatigability
Anaerobic respiration
Electrical Impulse Transmission
Sarcolemma
Transverse (T) Tubules
Sarcoplasm
Sarcoplasmic Reticulum (SR) & Terminal Cisternae
Triad
End Feet
- Sarcolemma: Membrane around each myofiber
- Transverse (T) Tubule: Membrane system penetrating myofiber sending electrical impulses from Sarcolemma into cell
- Sarcoplasm: Cytoplasm of myofiber
-
Sarcoplasmic Reticulum: Tubular system acting like smooth-ER
- Terminal Cisternae: Flattened sac of SR on either side of T-Tubule
- Triad: T-Tubule + 2 Terminal Cisternae (1 on either side)
- End Feet: Connect T-Tubules w/ SR to allow Ca release
Neuromuscular Junction (NMJ)
Skeletal muscle innervated by what neurons?
Relationship between # of nerves and myofibers
Peripheral a-motor neurons from anterior horn of spinal cord
1 nerve per myofiber
1+ myofiber per nerve
Neuromuscular Spindle Apparatus
What is the action
Extrafusal Muscle Fibers function
Intrafusal Muscle Fibers function
Type Ia Sensory Nerve Fibers function
a-Motor Nerve Fibers function
g-Motor Nerve Fibers function
Reflexive response to prevent overstretching of a muscle
EF: Contract the muscle
IF: Sense length and rate of change of muscle fibers
Afferent innervation of intrafusal fibers
efferent innervation of extrafusal muscle fibers (receive signal from Type Ia Fibers and cause EFs to shorten)
efferent innervation of intrafusal muscle fibers (receive signal from Type Ia fibers and cause IFs to shorten)
Neuron Terminology
Soma/Body
Nissle Substance
Dendrite
Axon Hillock
Axon
Synapse
Contains all organelles of neuron
Abundant rER within cytoplasm of Soma
Receives signals from other neurons
Connection between Soma and Axon (summates electrical signals received by all dendrites to transmit down axon)
Conveys electrical impulse to synapse
Transfers electrical impulse from neuron to target tissue
Nerve Arrangement
What is the organization of Nerves?
Axon (Endoneurium) –> Fascicle (Perineurium) –> Nerve (Epineurium)
Neuron Types
Multipolar
Bipolar
Pseudounipolar
Multiple dendrites and one axon
Single dendrite (multiple extensions) and one axon
One cell process with a single dendrite branch and axon branch
Myelination
Schwann Cell
Oligodendrocyte
Myelin Sheath
- Surrounds axon and creates myelin sheath in PNS
- Wrap around one part of one axon
- Surrounds axon and creates myelin sheath in CNS
- Wrap around a part of many axons
- Circumferential layers of myelin allowing fast signal conduction velocity
