LEC-1 Muscle PNS Review Flashcards
What are the three types of muscle?
- Skeletal muscle
- Cardiac muscle
- Smooth muscle
What are the characteristics of skeletal muscle?
- Long
- Unbranched
- Multinucleated (peripherally located)
- Striated
- Voluntary
What are the characteristics of cardiac muscle?
- Branched
- Intercalated disks
- Central nucleus
- Striated Involuntary (heart)
What are the characteristics of smooth muscle?
- Spindle shaped
- One central nucleus
- Not striated
- Involuntary (vessels and gut)
What is bursa?
Fluid-filled sacs located in high friction zones such as the shoulder
What are the two types of muscle fibers?
- Red
- White
Describe red fibers.
- Type 1
- Rich blood supply
- Contain mitochondria and myoglobin
- Slow twitch
- Oxidative
- Sustained contraction (not easily fatigued)
Describe white fibers.
- Type 2b
- Poor blood supply
- No mitochondria or myoglobin
- Fast twitch
- Glycolytic (anaerobic glycolysis)
- Easily fatigued
Describe intermediate fibers.
- Fast twitch
- Oxidative
- Glycolytic (anaerobic glycolysis)
- Less myoglobin
What is a muscle triad?
- Located at A-I junction
- 2 Terminal cisternas+ 1 Transverse tubule
The “canister” of a muscle cell is considered to be the ___________.
Myofiber
The “straws” inside the canister (myofiber) of a muscle cell are called ____________.
Myofibrils
The “toothpicks” inside the the straws (myofibrils) of a muscle cell are called ____________.
Myofilaments
The transverse tubule is a continuation of the ______________.
Sarcolemma
What are the possible diagnostic tests used to diagnose myofibrillar myopathies?
- Electromyography (EMG)
- Nerve Conduction Study
- Muscle Histology
- Light microscopy
- Electron microscopy
What type of microscopy will expose hyaline inclusions (fibrillar material) within fibers, granulous material, and small vacuoles that result from autophagocytosis of cellular debris?
Light
What type of microscopy will reveal myofibril degeneration at Z-discs within muscle fibers?
Electron
Label the following diagram:
Label the following diagram:
What does the sarcoplasmic reticulum store?
Calcium
What happens to the A band during contraction?
It remains the same
What happens to the distance between the Z lines during contraction?
It shortens
What intermediate filament serves to keep myofibrils in register at Z line?
Desmin
What links the α-actinin/desmin complex to plasma membrane dystroglycans?
Dystrophin
What are gap junctions?
Specialized channels used in smooth muscle to ensure coordinated contraction. These channels allow electrical impulses to pass more quickly to adjacent cells through a shared perforation in cell membrane.
What are gap junctions in cardiac muscles called?
Intercalated discs
What is a motor unit?
A motor unit is a nerve and the myofibers it innervates.
What epithelial layer of a peripheral nerve is affected in Guillan-Barre Syndrome?
Endoneurium
What epithelial layer of a peripheral nerve must be sutured in surgery?
Perineurium
What are the three layers of connective tissue covering skeletal muscle fibers?
- Epimysium (outermost layer)
- Perimysium (intermediate layer; found between each fascicle)
- Endomysium (innermost layer; found between each myofiber)
What is the defect in Lambert-Eaton Syndrome?
Voltage-gated Calcium channels on pre-synaptic cell
What is the defect in Myasthenia Gravis and what is the result?
Antibodies towars ACh receptors on the post-synaptic cell Results in loss of junctional folds
What happens to intrafusal fibers when an extrafusal fiber contracts?
It loses tension and compensates by shortening
(Schwann cells/Oligodendrocytes) are located in the PNS.
Schwann cells
(Schwann cells/Oligodendrocytes) are located in the CNS.
Oligodendrocytes
(Schwann cells/Oligodendrocytes) provide myelin for up to 50 axons at once.
Oligodendrocytes
(Schwann cells/Oligodendrocytes) provide myelin for only a single axon at a time.
Schwann cells
Guillain Barre syndrome may indicate pathology involving (schwann cells/oligodendrocytes).
Schwann cells
An acoustic neuroma may indicate pathology involving (schwann cells/oligodendrocytes).
Schwann cells
- Acoustic neuromas are also called schwannomas
Multiple sclerosis may indicate pathology involving (schwann cells/oligodendrocytes).
Oligodendrocytes
(Merkel’s discs/Meissner’s corpuscles) adapt quickly, are found in hairy skin, and are used to detect shapes and edges.
Merkel’s discs
(Merkel’s discs/Meissner’s corpuscles) adapt slowly, are found in glabrous skin, and are used to detect light touch.
Meissner’s corpuscles
In a (neuropathy/myopathy), innervation is intact and weakness is proximal and symmetrical. May result from atrophy caused by aging, malnutrition, or immobilization.
Myopathy
In a (neuropathy/myopathy), innervation is lost and weakness is distal and asymmetrical. May result from atrophy caused by motor neuron degeneration.
Neuropathy
What is the afferent and efferent limb of the muscle spindle organ (deep tendon reflex)?
- Afferent: Ia and II fibers
- Efferent: Gamma motor neurons
What are Pacinian Corpuscles sensitive to?
Vibration Pressure
