4.1) 1. Membrane permeability to certain ions-via ion channels

2. Electric field across membrane

3. Active transport via sodium-potassium pump

4. Concentration gradients

4.8) (a) Absolute Refractory Period: no action potential can be elicited during this period, no matter how strong the excitatory stimulus.

(b) Relative Refractory period: accurs after the absolute refractory period; a large supra threshold stimulus will elicit an action potential.

(c) compound nerve action potential: measured from a periferal nerve (not a single axon), represents the summation of many action potentials originating from axons making up the the periferal nerve. A single periferal nerve can contain hunderds of thousands of individual neurons.

(d) synapse: connection between two neurons that enables them to communicate. The synapse can be either chemical, wherein the post-synaptic membrane is polarized or depolarized when the pre-synaptic membrane releases neurotransmitters or electrical synpase, where the two neurons physically touch each other and the mediating agent is direct electrical current.

(e) neuro-myo junction: connection between the neuron and the muscle fiber.

(f) motor unit: smallest muscle structure that can be activated via a volitional effort.

(g) reflex arc: sense organ (sense receptors such as touch, pressure, temperature, or light), sensory nerve (transmits receptor data to spinal chord or brain), CNS (central nervous system, decides whether or not to send a motor response to sensory data0, motor nerve (carries data from CNS to peripheral skeletal muscle (the effector organ).

4.26) A spectral analyzer should consist of a bank of bandpass filters capable of extracting the standard frequency bands in the EEG:

alpha: 8 - 13 Hz

beta: 14 - 30 Hz

theta: 4 - 7 Hz

delta: < 3.5 Hz

The output if each bandpass filter should then be fed to a processor that computes average power, thereby giving the average power in each frequency band. The average power is sometimes expressed as a percentage of total power and when the data comes from a montage of electrodes on the scalp, a display of percent alpha, beta, theta, or delta can be generated, sometimes called a Brain Electrical Activity Map (BEAM). Block diagram:

4.27) Volume conductor theory makes it possible to localize the source within the cortex of the brain of certain scalp-measured evoked potentials. By measuring the evoked scalp field, obtained by averaging together numerous responses to repetitive stimuli, one can infer the equivalent dipole source for that particular scalp field by solving the so-called inverse problem. This is useful for mapping the electrical activity of specific portions of the cortex during the presentation of sensory stimuli.

5.10)

5.19)