part 4 nervous tissue

Gasotransmitters:

nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S). They are made on demand and can influence signaling and other cell functions.

Endocannabinoids:

lipid-based messengers that act on cannabinoid receptors; they are made on demand and are involved in processes such as learning, memory, appetite, and nausea regulation

Reuptake:

the neurotransmitter is taken back into the axon terminal or nearby cells.

Enzymatic breakdown:

an enzyme deactivates the neurotransmitter (for example, AChE breaks down ACh).

Diffusion:

the neurotransmitter moves away from the synaptic cleft.

Serial processing

: information follows one pathway in sequence. A spinal reflex is a classic example.

Parallel processing:

information travels along multiple pathways at the same time, allowing one input to produce several kinds of processing or responses.

Neural circuits

are patterns of connections between neurons in a neuronal pool.

Diverging circuit:

one neuron sends signals to many neurons; spreads information or amplifies a signal.

Converging circuit:

many neurons send input to one neuron; combines information from different sources.

Reverberating circuit:

output feeds back into earlier parts of the circuit; can produce repeated or ongoing activity.

Parallel after-discharge circuit

: input travels along several pathways of different lengths that reconverge; outputs arrive at different times and can prolong the response.

CNS vs PNS:

CNS = brain and spinal cord; PNS = nerves and ganglia outside CNS.

Dendrite vs axon:

Dendrites receive input toward cell body; axon carries output away from cell body.

Tract vs nerve:

Tract is a bundle of axons in CNS; nerve is a bundle of axons in PNS.

Nucleus vs ganglion:

Nucleus is a cluster of cell bodies in CNS; ganglion is a cluster in PNS.

Oligodendrocyte vs Schwann cell:

Oligodendrocyte makes CNS myelin; Schwann cell makes PNS myelin and supports repair.

Graded potential vs action potential:

Graded potentials vary in size and fade; action potentials are all-or-none and do not fade along the axon.

Depolarization vs hyperpolarization:

Depolarization makes the inside less negative; hyperpolarization makes it more negative.

EPSP vs IPSP:

EPSP increases the chance of firing; IPSP decreases the chance of firing.

Absolute vs relative refractory period:

Absolute: no second AP possible; relative: possible only with a stronger stimulus.

Anterograde vs retrograde transport:

Anterograde moves away from cell body; retrograde moves toward it.