BPK 105 Study Guide - Midterm Guide: Axon Hillock, Reticular Formation, Resting Potential
27 Apr 2018
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Module 4 - Terminology
Terminology
1. central nervous system or CNS (Section 8.2): Brain and spinal cord.
2. peripheral nervous system or PNS (Section 8.2): Part of the nervous system not
surrounded by the skull or vertebral column; consists of nerves and ganglia.
3. neuron (Section 8.3): Nerve cell.
4. axon hillock (Section 8.3): The area where the axon leaves the neuron cell body is
called the axon hillock.
5. dendrites(Section 8.3): Short, treelike cell process of a neuron; receives stimuli.
6. axon(Section 8.3): Main process of a neuron; usually conducts action potentials
away from the neuron cell body.
7. blood brain or blood-brain (Section 8.3): blood-brain barrier - Cellular and matrix
barrier made up primarily of blood vessel endothelium, with some help from the
surrounding astrocytes; it allows some (usually small) substances to pass from the
circulation into the brain but does not allow other (larger) substances to pass.
8. resting membrane potential (Section 8.4): charge difference across the membrane
of a resting cell (i.e., a cell that has not been stimulated to produce an action
potential).
9. local current (Section 8.4): The channels responsible for the action potential are
voltage- gated Na+ and K+ channels. When the cell membrane is at rest, the
voltage-gated channels are closed (figure 8.8, step 1). When a stimulus is applied to
a muscle cell or nerve cell, following neurotransmitter activation of chemically gated
channels, Na+ channels open very briefly, and Na+ diffuses quickly into the cell
(figure 8.8, step 2). This movement of Na+, which is called a local current, causes
the inside of the cell membrane to become posi- tive, a change called
depolarization.
10. threshold (Section 8.4): a limit below which a stimulus causes no reaction. // If
depolarization is large enough, Na+ enters the cell so that the local potential reaches
a threshold value. Action potentials occur in an all-or-none fashion. That is, if
threshold is reached, an action potential occurs; if the threshold is not reached, no
action potential occurs.
11. saltatory (Section 8.4): In myelinated axons, an action potential at one node of
Ranvier causes a local current to flow through the surrounding extracellular fluid and
through the cytoplasm of the axon to the next node, stimulating an action potential at
that node of Ranvier. By this means, action potentials “jump” from one node of
Ranvier to the next along the length of the axon. This type of action potential
conduction is called saltatory (to leap) conduction (figure 8.11).
12. hyperpolarized (Section 8.4): To increase polarization of membranes of nerve or
muscle cells. // If K+ or Cl− channels open, the inside of the postsynaptic cell tends
to become more negative, or hyperpolarized (hı′per-p̄′l̆r-ı-zed), and an action
potential is inhibited from occurring.
Document Summary
When the cell membrane is at rest, the voltage-gated channels are closed (figure 8. 8, step 1). When a stimulus is applied to a muscle cell or nerve cell, following neurotransmitter activation of chemically gated channels, na+ channels open very briefly, and na+ diffuses quickly into the cell (figure 8. 8, step 2). This movement of na+, which is called a local current, causes the inside of the cell membrane to become posi- tive, a change called depolarization: threshold (section 8. 4) : a limit below which a stimulus causes no reaction. // if depolarization is large enough, na+ enters the cell so that the local potential reaches a threshold value. That is, if threshold is reached, an action potential occurs; if the threshold is not reached, no action potential occurs: saltatory (section 8. 4) : in myelinated axons, an action potential at one node of.
