Ch.11 Part 1 & 2

Support and brace neurons, regulate exchanges between capillaries and neurons, guide neuron migration, control chemical environment, respond to nerve impulses, and participate in information processing.

They monitor neurons, migrate toward injured neurons, and can transform to phagocytize microorganisms and neuronal debris.

They line brain and spinal cord cavities, may be ciliated to circulate cerebrospinal fluid (CSF), and form a permeable barrier between CSF and CNS tissue fluid.

They have processes that wrap CNS nerve fibers, forming insulating myelin sheaths around thicker axons.

Satellite cells: surround neuron cell bodies, similar to astrocytes.
Schwann cells: form myelin sheaths around peripheral nerve fibers and aid in nerve regeneration.

Extreme longevity, amitotic (do not divide), high metabolic rate requiring continuous oxygen and glucose, and have a cell body with one or more processes.

Also called soma or perikaryon; biosynthetic center synthesizing proteins and chemicals; contains nucleus, rough ER (Nissl bodies), and is the receptive region for input.

Short, branched processes that receive signals and convey incoming messages toward the cell body as graded potentials.

Each neuron has one axon starting at the axon hillock; it generates and transmits nerve impulses to axon terminals, which release neurotransmitters.

A whitish, protein-lipid substance that protects and electrically insulates axons and increases the speed of nerve impulse transmission.

By Schwann cells wrapping around axons in a jelly-roll fashion; one Schwann cell forms one segment of myelin sheath.

Gaps between adjacent Schwann cells where axon collaterals can emerge; sites where action potentials are generated in myelinated fibers.

Multipolar: many dendrites, one axon (most common).
Bipolar: one dendrite, one axon (rare).
Unipolar: single T-shaped process (sensory neurons).

Sensory neurons: transmit impulses toward CNS.
Motor neurons: carry impulses from CNS to effectors.
Interneurons: connect sensory and motor neurons within CNS.

Approximately −70 mV; the inside of the membrane is negatively charged relative to the outside, maintained by ionic concentration differences and membrane permeability.

Potassium (K+), due to its higher permeability and concentration gradient across the membrane.

Maintains concentration gradients by pumping 3 Na+ out and 2 K+ in, stabilizing resting membrane potential.

Short-lived, localized changes in membrane potential triggered by opening of gated ion channels; can be depolarizations or hyperpolarizations.

Brief, long-distance electrical signals in axons involving rapid depolarization and repolarization; do not decay over distance.

1. Resting state: all gated channels closed.
2. Depolarization: Na+ channels open, Na+ influx.
3. Repolarization: Na+ channels inactivate, K+ channels open.
4. Hyperpolarization: K+ channels remain open briefly.

An action potential either occurs fully when threshold is reached or does not occur at all.

Axon diameter (larger is faster) and degree of myelination (myelinated fibers conduct faster via saltatory conduction).

Action potential propagation in myelinated axons where the signal jumps from one myelin sheath gap to the next, increasing speed.