Hist: Skeletal muscle and nerve tissue Flashcards
Skeletal muscle
makes up the skeletal muscle system
striated and voluntary movement and posture
makes up 40 percent of the body mass
Cardiac muscle
Heart, striated and involuntary
pumps blood through the CV system
Smooth muscle
Non-striated and involuntary
visceral organ tone and movement, walls of hollow viscera, and blood vessels
does vasoconstriction and dilation
How does contraction occur?
thin (actin) microfilaments and thick (myosin) filaments organize into structures called myofibrilsin the cytopasm
when they slide past each other contraction occurs
what are the three layers of Connective tissue that organizes the myofibers into skeletal muscle?
Endomysium: separates myofibers
Perimysium: separates fascicles
Epimysium: Surrounds the entire muscle
Where is the nuclei located in a skeletal muscle cell
multinucleated cylinders
nuclei are located in the periphery of the cell and the cytoplasm is primarily occupied by myofibrils
What is the basic structural unit of a myofibril
sarcomere consisting of a thin actin and thick myosin
what are the sleeves around the myofibril and what are their purpose
Sacrolemma and sarcoplasmic reticulum: sereve as Ca2+ storage and sleeves around each myofibril
what are Transverse tubules
(t-tubules) and they are invaginations of the sacrolemma
help with transmission of action potentials and regulating cellular calcium levels
Terminal cisternae
dilated ends of the sarcoplasmic reticulum and they release the Calcium to trigger the muscle contraction
Structure of a sarcomere: Z line
Anchor site for actin (thin) filaments
Structure of a sarcomere: I band
Only contains actin filaments
Structure of a sarcomere: M-line
Anchor site for thick myosin filaments
Structure of a sarcomere: H-zone
contains only thick myosin filaments
Structure of a sarcomere: A-band
overlap of thick and thin filaments plus the H-zone
Sliding filament mechanism
during muscle contraction:
the thin filaments slide past the thick filaments toward the center of the sarcomere
this brings the Z lines close together
every myofibril in a muscle cell shortens at the same time and thus the entire muscle contracts
The thin and thick filaments do not change length they just change the degree they overlap
Tropomyosin
runs in the groove formed by F actin strands and it will bind to the troponin complex
Troponin 3 types
Troponin T: Binds the complex to tropomyosin
Troponin I: inhibits the binding of myosin to actin
Troponin C: binds calcium
Skeletal Muscle Fibers: Type I fibers
slow oxidative
contains slow ATPase, red due to high myoglobin
contractions slower and less powerful
contract for long periods of time without fatigue
Skeletal Muscle Fibers: Type IIa fibers
Oxidative-glycolytic
largest and most prevalent
intermediate ATPase and provides power
Primarily aerobic - intermediate fatigue
Skeletal Muscle Fibers: Type IIb fibers
Fast gycolytic Fast ATPase produces fast contractions largely anaerobic rapid fatigue lower myoglobin content
Neuroglia
Neuron supporting cells
much smaller than the neuron
Neuron
specialized for conduction of electrical impulses
cell body- process the electrical information
cell processes:
dendrites: carry electrical signal toward the nerve cell body
axon: 1 per cell and they carry the electrical signal away from the nerve cell
Nissl substance
cluster of staining in the neurons that show the abundant rough endoplasmic reticulum that takes up the stain
reflects the need to make lots of neurotransmitters and protein to maintain the neuron
3 classes of neurons
Multipolar: Many dendrites and one axon
Bipolar: one dendrite and one axon
Unipolar: one cell process from which branches a single axon and single dendrite
how do schwann cells and satellite cells interact with the neuron
Satelitte cells surround the cell body of the neuron
Schwann cells surround the nerve fiber by wrapping its self around multiple times, even unmylinated fibers but just not as many times
how does myelination help the transmission signal
creates nodes that allows for the signal to jump from node to node making the signal move much faster
what are the three connective tissues that surround a peripheral nerve
Endoneurium: CT between axons
Perineurium: CT surrounding clusters of axons forming fascicles
Epineurium: CT surrounding several nerve fascicles
What are the parts to the chemical synapse
Pre synaptic knob (axon terminal)
synaptic cleft
Pre synaptic membrane
Post synaptic membrane
Neuromuscular junction
Every skeletal muscle cell recieves an axon terminal where they release the neurotransmitters
the neurotransmitter causes changes in the sarcolemma that excite the muscle
this travels down the T Tubules that initicat the fiber contraction at the terminal cisterna (release of calcium)
Muscle spindle receptors:
monitor changes in length, rate of change, and tension of muscle
Intrafusal fibers: inside the muscle spindle
Extrafusal fibers: oustside the spindle, alpha motor fibers
Intrafusal fibers:
Nuclear bag fibers: wraps near center of cell and detect changes in length and degree of tension, Type Ia
Nuclear chain fibers: wraps end of cell and detects static muscle length Type II
Golgi tendon organs:
encapsulated receptors within myotendinous junctions that sense tension within the tendon
