Fundamentals of Neuroscience: Final Lectures 20-24 Flashcards
Motor control: Red muscle fibers are large numbers of ________ and ________, slow to contract and can sustain contraction. Antigravity muscles of the leg and torso.
mitochondria and enzymes
White muscle fibers are ______ (fast or slow) fibers. They have fewer __________ and contract and fatigue _________. These are the arm muscles.
Fast fibers, have fewer mitochondria and contract and fatigue rapidly.
In regards to white muscle fibers, FR fibers are
White fibers with moderate strength and fast contractions.
In regards to white muscle fibers, FF muscle fibers are
The fastest, strongest white fibers, but rapidly fatiguing.
Each motor unit (the motor neuron and all the muscle fibers it innervates) contains muscle fibers of ___________. (multiple type/single type)
Only a single type.
A single action potential triggers variable contractions. (True/False)
True
Repeated trains of AP’s lead to different rates of fatigue. (True/False)
True
Varying the amount of activity of muscles can change muscle fibers. There are two terms for this; _______ and ________.
Hypertrophy and Atrophy.
Crossed-innervation is
When nerve input is switched, i.e; there is a switch in muscle phenotype, which can be induced simply by changing the activity in the motor neuron.
Muscle Fiber Structure: When are muscle fibers formed?
Early in fetal development via the fusion of muscle precursor cells.
Each muscle cell has more than one nucleus. (True/False)
True.
Muscle fibers are enclosed by an excitable cell membrane called the
sarcolemma.
Within the muscle fiber are a number of cylindrical structures called _________, which contract.
myofibrils
What are the steps of muscle excitation/contraction coupling?
- Alpha motor neurons release ACh
- ACh produces large EPSP in muscle fibers.
- EPSP evokes muscle action potential.
- Action potential triggers Ca2+ release.
- Fiber contracts.
- Ca2+ reuptake
- Fiber consequently relaxes.
Myofibrils are divided into segments or disks by _______ lines.
Z lines
What is a sarcomere?
Two Z lines and a myofibril
A series of bristles anchored to Z lines are called
Thin filaments
Thick filaments exist where?
Between and among thin filaments.
Where does muscle contraction occur?
Muscle contraction occurs when the thin filaments slide along the thick filaments, bringing adjacent Z lines towards one another.
Steps in Excitation-Contraction Coupling: Sliding-Filament Assay Model
Binding of Ca2+ causes myosin (thick filament protein) to bind to actin (thin filament protein)
The Myosin “heads” pivot, causing the filaments to slide.
ATP unlocks this interaction.
Repetition of process “walks” myosin heads along filament.
Death does not cause stiffening of the muscles. (True/False)
False. Death DOES cause stiffening of the muscles.
Deep within the skeleton muscles are specialized structures known as ______.
spindles
Spindles serve what purpose?
Sensory feedback from muscle spindles = Stretch receptor
The spindles and their associated Ia axons are specialized for the detection of changes in muscle length (stretch) and are examples of proprioceptors (“body sense”).
The stretch reflex is regarded as an ______________.
Antigravity feedback loop.