Ch 19 Pt 1cd Flashcards
A motor neuron pool is 1 motor neuronal excitability CNS and many muscle fibres ?
False
-many motor neurons/ units
A motor unit innervates a variety of fibre types?
False
-a motor unit only innervates the same fiber type as it
Small motor units are typically involved in complex movements?
True
Alpha motor neurons are Afferent neurons?
False
-would be efferent because they send signals to the muscle, not away from it
At rest Inside the Muscle Fibers (cell): (3)
More Na+ on outside of cell
More K+ inside the cell
Controlled b y membrane permeability
Thus, fiber cell more negatively charged on the inside
RMP
Resting membrane potential
-around -70mV
Depolarization of a cell
Membrane potential becomes more positive
-70 closer to 0 or above
Repolarization
Membrane potential becomes more negative (back towards RMP)
Hyperpolarization
Membrane potential becomes more negative than resting membrane potential (-70)
Signals
Electrical currents created by movements of ions
Types of Signals: Endpoint Potential
Depolarization of hyperpolarization of membrane potential
Types of signals: Action Potential
Substantial (high) depolarization of membrane potential becomes
EPSP
Excitatory input from one neuron to another
Depolarizations of postsynaptic membrane
-facilitates (may lead to) AP
IPSP
Inhibitory input from one neuron to another
Hyperpolarizations of postsynaptic membrane
-inhibits AP (doesn’t happen)
Action Potentials can be generated by: (2)
Temporal Summation: one or few neurons can deliver REPETITIVE subthreshold stimulus over a short period of time -SAME NEURONS
Spatial Summation: a bunch of EPSPs can be delivered from DIFFERENT pre synaptic terminals
AP
Action Potential: substantial depolarization (subthreshold level) that will result in muscle contraction
EPP
End Point Potential: depolarization or hyperpolarization that does NOT result in muscle contraction
Initiation the AP
Impulse travels down axon terminal
Calcium channels open, calcium diffuses into axon
Causes fusion of synpatic vesicles -carnations ACh with membrane of axon
Vesicles release ACh into synpatic cleft
ACh binds on receptors on muscle membrane, excites membrane, changes permeability
Channels open to allow Na in and K out
Initial opening of sodium and potassium due to:
Binding of acetylcholine with muscle membrane
Open of adjacent channels on the muscle due to:
Spread of electrical charge (voltage gated)
Muscle Fiber Stimulation/ Excitation
- Impulse (AP)- moves down axon of motor neurons
- Ca channels open and calcium moves into terminal
- ACh primes for release
- ACh transverse the synapse and binds to ACh receptors on postsynaptic terminal
- Changes permeability of membrane (influx/ efluxx of Na and K)
- Depolarization generates EPP, if at threshold an AP
- AP depolarization wave spreads throughout the T-Tubule network into muscle fiber
Ending Excitation
AP- prepares muscle fiber for contraction by travelling down T-Tubule
ACh hydrolysis -broken down by cholinesterase to depolarize postsynaptic membrane
Axon resynthesizes acetic acid to form ACh to process can repeat
