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- also called volentary muscle
- under our volentary control
- moves body at joints
- Long tubes formed from fusion of multiple embrionic cells (syncytium)
- dozens or hundreds of nuclei, along outside of fused muscle cell
- Like skeletal muscle they are striated (tiger srtiped pattern)
- found only in the heart
- not under volentary control
- single cell, branched, connected at intercalated discs
- single nucleus along outside of baranched muscle cell
- not striated
- smooth appearance
- single cells, unbranched, spindle shaped
- not under volentary control
- single nucleus in center of cell
- located in arteries and the gut tube
The ________ of muscle cells is basically the same as the __________ of any other cell.
Like all cells, muscle cells have _____ _________made up of _______ ______ strung togethe like beads on a string to make loing rods.
thing filaments, globular actin
Muscle cell proteins
- Muscle cells use actin (same as microfilament protein in all cells)
- Aslo use myosin (protein that interacts with actin to cause contractions)
- Regulatory proteins control the interaction between actin and myosin
- Structural proteins keep myosin and actin in teh correct orientations
- -especially in striated muscle (skeletal and cardiac)
- -gives striated musle its charcteristic appearance
Transverse tubules (T tubules)
- help the electrical potentials (voltagechanges) rapidly penetrate into the center of the cell.
- used to carry this electrical change into the core of the myofibril
- There are dozes of myofibrils in a muscle cell
- a groupof highly organized myosin and actin molecules
- -also regulatory and structrual proteins
- a specialized form of smooth endoplasmic reticulum
- stores calcium ions and releases them when needed
- formed by 1 transverse tubule spur plus 2 sacs of sarcoplasmoc reticulum
- -T tubule brings electrical charge inside cell; SR releases calcium in response to electrical signal.
What is the organization of Myofibrils?
- The sarcomere is the contractile untit of skeletal and cardiac muscle
- Z disc: protiens hold actin filaments in place
- Z disc to Z disc = 1 sarcomere
By cutting a __________ in cross-sections in electron mycroscopy, we can see the relationship between the _________ filament of myosin (big dots) and the thin filaments of _____ (smaller dots). There are regoins where only actin filaments are found, regions where only ________ filiments are found, and regions where they _______.
sarcomere, thick, actin, myosin, overlap
- where the actin filaments are held togethera zigzag line which defines the border of sarcomeres
- When sacromere contracts, Z lines move closer together
- short for isotropic
- a region of just actin filaments wheich does not bend polarized light (so it is "same" "turning")
- actin thin filiaments only
- short for anisotropic
- part of a sarcomere that bends polarized light
- myosin and myonsin + actin
What is polarized light?
a special kind of light used before the inventionf the electron microscope to see things better
(German Hell = "bright") is where myosin thick filaments are found alone
Neuromuscular junciton (NMJ)
- the point of contact between the nervous syustem and the muscular system
- here, motor neuron releases acetuylcholine (ACh), a achemical neurotransmitter which causes muscle cell contraction
_________ , or nerve cells, are the thinking and information processing cellsof the __________ system.
Neurons work by __________ chemical substances onto other cells; these chemical substances, called _____________ because they transmit information from neurons, cause an ____________ change inthe cell that receives the _________.
releasing, neurotransmitters, electrical, message
- brain cells that control muscle tissue
- they recieve input from :
- -the brain through the spinal cord
- -a reflex pathway within the spinal cord
- They generate an electical impulse (action potential) which travels along a "cable" (axon) to its end (axon terminal)
- ex. neurotransmitter -acetylcholine (ACh): the cell recieving the message is a skeletal muscle cell.
True ore False: A single moter neuron brances several times and contacts muscle fibers.
One neuron can make contact with a varying number of muscle fibers, form three up to three thousand.
When a motor neuron recieves proper ________, it relases acetylchloline onto the ___________ of the muscle fiber. Their specialized receptors turn the chemical signal into an _______ _______. These receptors respond best to the drug _______ and so they are called _________ acetylcholine receptors.
stimulus, sarcolemma, electrical signal, nicotine, nicotine
The electrical signal from the nicotinic ACh receptor spreads over the entire surface of the ________ _______, penetrating into the __________ _________ (T tubules) where they meet the sarcoplasmic _________ (SR) at triads. This causes ______ release from its stores in the SR.
muscle fiber, transverse tubules, reticulum, calcium
The way that neurotransmitters are released from nerves
Alpha motor neuron (a motor neuron)
- The last neuron in the motor neuron chain
- has its cell body and dentrites (info recievers) inside the spinal cord.
- if a certain combination of events occures, the moter neuron fies and action potential
- Potential means "voltage"
- This is a voltage that changes over time and produces an event.
- A change in voltage that last for just a brief period of time and makes things happen.
n the _________ __________ , the action potential travels from the spinal cord to the muscle, using the ______ of the nerve cell to make the journey. When it gets to the end of the axon-- the ________ _________--the action potential triggers the release of __________ (ACh).
motor neuron, axon, axon terminal, acetulcholine
- stops tha action of ACh,
- breaks apart the ACh molecule at its ester linkage, into acetate and cholin.
- neitherof these substances can bind to receptors
- the muscle cell action potential ends and the peices of the ACh molecule are taken up into the presynaptic (motor neuron) axon terminal for recycling tonto ACh.
Futher indepth explanation of Neuromuscular Junction
- Motor neuron action potentioal arrives at eh neuromuscular junction
- 1. Impulose triggers release of acetylcholine
- 2. Acetylcholine diffuses across the space between nerve and muscle cell, triggering muscle cell action potential -this eventually causes calcium release from stores in muscle
- 3. Action potential travels along muscle surface
- -ACh removed by the enzyme acetylcholinesterase (AChE)