His: Skeletal Muscle and Nerve Tissue Flashcards
Myofibers are separated by _________.
Endomysium
Fascicles are separated by __________.
Perimysium
Entire muscle is covered by ____________.
Epimysium
Group of muscles are called ______.
Fascicles
- ______ is located in the periphery of a skeletal upscale cell. 2. ______ is occupied by myofibrils.
- Nucleus 2. Cytoplasm
Myofibrils are composed of _____ and _____ filaments.
Thin and thick filaments
Basic structural unit of the myofibrils
Sarcomere
Calcium storage site and sleeves around each myofibrils
Sarcolemma and SR
Invaginations of the sarcolemma
Transverse tubules (T-tubules)
Dilated ends of SR that release Ca2+ and trigger muscle contraction
Terminal cisternae
Anchor site for actin (thin) microfilaments
Z-line
Contains actin thin filaments
I-band
Anchor site for thick myosin filaments
M-line
Contains only thick myosin filaments
H-zone
Overlap of thick and thin filaments plus H-zone
A-band
When a muscle cell contracts, the ____ filaments slide past the ___ filaments toward the center of the sarcomere. The ____ are brought closer together.
- Thin filaments 2. Thick filaments 3. Z-lines
- ___ provides the driving force for movement. 2. ____ drives the movement of myosin heads along actin filaments.
- Myosin II heads 2. ATP
Contains a long alpha-helical coiled-coil tail that enables several molecules to assemble into large bipolar aggregate or filament
Myosin II
- runs in the grooved formed by F-actin strands - binds to troponin complex - extends for the length of 7 actin monomers - consists of 2 nearly identical alpha-helical polypeptides twisted around each other
Tropomyosin
Complex of 3 proteins: - troponin T - troponin I - troponin C
Troponin
Binds the troponin complex to tropomyosin
Troponin T
Inhibits the binding of myosin to actin (relative to the troponin complex)
Troponin I
Binds Ca2+ in the troponin complex
Troponin C
- slow ATPase - red (high myoglobin) - slow, less powerful contraction - contract for long periods without fatigue
Type I fibers (slow oxidative)
- largest and most prevalent type of skeletal muscle fiber - intermediate ATPase - provides power - primarily aerobic - intermediate fatigue
Type IIa fibers (oxidative glycolysis)
- fast ATPase produces fast contractions - largely anaerobic - rapid fatigue - lower myoglobin content
Type IIb fibers (fast glycolytic)
Types of nerve tissue
- Neuron 2. Neuroglia (neuron supporting cells)
Two major parts of the neuron
- cell body - cell processes (dendrites and axons)
Functional cells of nervous tissue
Neurons
Functions of neurons
Receive, process, transmit electrical signals
Stain that is taken up by abundant rough ER which reflects need to make lots of neurotransmitters and protein to maintain this large cell
Nissl substance
(Nerve Cell) processes the electrical information
Cell body
(Nerve Cell) carry electrical signals toward the nerve cell body
Dendrites
(Nerve Cell) carries electrical signals away from the nerve cell body
Axon (only 1 per cell)
(Nerve Cell) where electrical signals are transferred from the axon terminal of the nerve to an effector cell
Synapse
Multipolar neuron
- many dendrites - one axon
Bipolar neuron
- one dendrite - one axon
Unipolar neuron
- one cell process from which branches a single axon and single dendrite
What surrounds neurons in the PNS?
- satellite cells - Schwann cells
What forms myelin in the (1) CNS and (2) PNS?
- Oligodendrocytes - wrap cell process around axon 2. Schwann cell - wraps itself around the axon
Nodes of Ranvier
Transmission signal jumps from node to node which is why conduction is faster with myelination
____ surround axons.
Endoneurium
____ surrounds clusters of axons forming fascicles.
Perineurium
_____ surrounds several nerve fascicles.
Epineurium
Parts of the chemical synapse
- Presynaptic knob 2. Synaptic cleft 3. Presynaptic membrane 4. Post-synaptic membrane
Synaptic vesicles in the presynaptic knob contain (1) ______ which is released into the (2) ________ by (3) ________. Neurotransmitters bind to receptors on the (4) ________. This binding (5) ____________.
- Neurotransmitter 2. Synaptic cleft 3. Exocytosis 4. Post-synaptic membrane 5. Stimulates the post-synaptic cell
Ends of nerve fibers store and release chemical messengers at NMJ
Axon terminals
Space between axon terminal and muscle cell plasma membrane
Synaptic cleft
Every ____ muscle cell receives an axon terminal.
Skeletal
Steps of muscle contraction
- Nerve impulse stimulates release of Acetylcholine (example) into the synaptic cleft. 2. ACH stimulates changes in the sarcolemma that excite the muscle fiber. This stimulus is carried down the T-tubules to initiate fiber contraction. 3. Enzymes in the synaptic cleft break down ACH and limit its action to single muscle twitch.
Function of muscle spindle receptors
Monitor changes in length, rate of change, and tension of muscle
Specialized fibers inside the muscle spindle
Intramural fibers
Types of intrafusal fibers
- Nuclear bag fibers 2. Nuclear chain fibers
- wrapped at the center by type Is nerve fibers - detect change in length and degree of tension
Nuclear bag fibers
- wrapped at their ends by type II nerve fibers - detect static muscle length
Nuclear chain fibers
Muscle fibers outside the spindle
Extrafusal fibers (alpha motor fibers)
a. epimysium
b. perimysium
c. endomysium
d. muscle fiber in middle of fascicle
a. muscle fiber in middle of a fascicle
b. endomysium
c. perimysium
d. epimysium
skeletal muscle
muscle fiber
a. sarcomere
b. z-line
c. h-zone
d. a-band
e. i-band
a. soma
b. nuclei of neuroglia
c. Nissl substance
d. nucleus of neuron
e. nucleolus
f. axon
g. neuron
h. dendrites
dorsal root ganglion
dorsal root ganglion
peripheral nerve structures
motor end plate
muscle spindle and tendon receptors
