Neurophysiological Basis of Movement - Mark Latash Flashcards
How does Latash define a complex system?
“a system whose properties cannot be derived from and should not be searched for in the properties of its elements”
What is the formula for the net (unbalanced) charge (Q) on a membrane?
The net charge equals its capacitance (C) multiplied by voltage (V) across the membrane.
Q = C * V
What are the three key ions (and their charges) in the electric phenomena in neurons? How are they usually concentrated inside and outside of the cell?
Potassium (K+), Sodium (Na+) and Chlorine (Cl-). Potassium usually has a high concentration within the cell and low concentration outside the cell, while sodium and chlorine are found in higher concentrations outside of the cell.
What is the feature of the action potential referred to as the law of “all-or-none?”
A stimulating current below the membrane (or stimulation) threshold will not create a significant chance in potential, while any current above the membrane threshold will generate the same action potential.
What is the difference between positive and negative feedback?
Positive feedback amplifies an effect or stimulus, while negative feedback works to restore the original state?
Why are the following two factors important for the propagation of an action potential:
- Inactivation of sodium channels within an area of the membrane just after an action potential.
- Different densities of sodium channels at different sections of a membrane.
A1: Inactivation keeps a potential from “backfiring” - the potential can only excite the membrane going ‘forward’.
A2: Some areas of the membrane are more readily excitable and likely to generate an action potential.
Name two important features of myelinated fibers?
- Increases the distance at which local currents from an action potential are able to reach the threshold of membrane depolarization.
- Sodium channels are concentrated in Ranvier nodes; the action potential in a sense “jumps” from one node to the next.
What are the five types of afferent or sensory axons?
Ia (A-alpha) - Muscle spindle, primary endings
Ib (A-alpha) - Golgi tendon organ
II (A-beta) - Muscle spindle, secondary endings
III (A-delta) - Muscle deep pressure endings
IV (C) - Nociceptors (pain)
What are the three types of efferent or motor axons?
A-alpha - Skeletal muscles
A-beta - Muscles and spindles
A-gamma - Muscle spindle
What is the difference between obligatory and nonobligatory synapses?
Obligatory synapses - an action potential on the presynaptic membrane always gives rises to an action potential on the postsynaptic membrane; common between neural cells and muscle cells
Non-obligatory synapses - a single action potential on a presynaptic membrane is typically unable to induce an action potential on a postsynaptic membrane; common with nervous system
What are the three major types of neurotransmitters? What are some examples?
Amino acids - gamma-aminobutyric acid (GABA), glutamic acid and leucine (excitatory neurotransmitters that depolarize postsynaptic membrane), glycine (inhibitory mediator found in spinal cord)
Biogenic amines - acetylcholine, serotonin, dopamine, and norepinephrine
Neuropeptides - endorphins and enkephalins
Explain the difference between temporal summation and spatial summation.
Temporal summation - when a subsequent action potential comes to the same synapse during the EPSP of a previous signal, its postsynaptic effects can superimpose on the previous signal and lead to a larger EPSP.
Spatial summation - if action potentials come simultaneously to multiple synapses, the depolarization of the postsynaptic membrane in synapses will be bigger than in response to only its own action potential.
Why is the “partial permeability” of biological membranes important?
‘Partial permeability’ allows the exchange of information with the environment while protecting the contents of the cell.
What are the three major groups of substances that can travel across the membrane?
- Solvents - The most common solvent is water; however, some substances are soluble in lipids, and this, in particular, allows them to pass through cell membranes more easily.
- Electrolytes - These are ions that have a non-zero electric charge.
- Non-electrolytes - These are molecules or fragments of molecules without a net electric charge. Many products of cellular metabolism are non-electrolytes.
How does concentration of particles changes as a result of convection? Diffusion? Under the action of an electrical field?
Convection, or bulk flow, is proportional to pressure difference. An example would be movement of water because of a difference in hydrostatic pressure.
Diffusion occurs due to the random motion of particles leading to a net movement from an area with a high concentration to an area with a lower concentration.
Electrolytes can move in response to an electric field; a current is a flow of charged particles that is proportional to the difference in potentials.
