Nervous System I & Chapter 10: Nervous System Topics (Sections 10.1–10.6)

Vocabulary flashcards covering the key concepts from Chapter 10: Nervous System topics (10.1–10.6) including neurons, neuroglia, membrane potentials, synapses, and impulse processing.

Nervous system functions

Collects sensory input, processes and interprets information (integration), and produces motor output to respond to stimuli.

Three general functions of the nervous system

Sensation (sense changes), integration (process and interpret), and motor output (initiates responses).

Nervous tissue cell types

Two major cell types: neurons (nerve cells) and neuroglia (glial support cells).

Neuroglia

Support, protect, and nourish neurons; include CNS and PNS glial cells with various roles.

CNS organs

Brain and spinal cord.

PNS components

Nerves and ganglia (and associated receptors); connects CNS to the rest of the body.

Nerve vs neuron

A nerve is a bundle of axons outside the CNS; a neuron is a single signaling cell.

Sensory receptors location

Located in the PNS; they detect stimuli and transmit signals to the CNS.

Function of a sensory receptor

Detect a stimulus and convert it into a neural signal (transduction) sent to the CNS.

Somatic nervous system

Subdivision of the PNS that controls voluntary activities and skeletal muscles.

Autonomic nervous system

Subdivision of the PNS that controls involuntary activities (viscera, smooth/cardiac muscle, glands).

Receptive surface of a neuron

Dendrites and the cell body (soma) provide most receptive areas for signals.

Unique features of neurons

Excitability and conductivity; high metabolic rate; longevity; typically amitotic; specialized processes (dendrites, axons, synapses).

Axons and dendrites count

Neurons usually have one axon and many dendrites.

Cellular parts of a neuron

Cell body (soma), dendrites, axon, axon terminals, nucleus, Nissl bodies, axon hillock, synapses, myelin sheath (in many).

Axon branches

Collateral branches.

Synaptic knobs location and function

Located at axon terminals; release neurotransmitters into the synapse to communicate with other cells.

What is myelin and its macromolecule composition

Myelin is a fatty insulating sheath around many axons; primarily composed of lipids (phospholipids, cholesterol) with proteins.

Neurolemma

The neurilemma (outer layer of Schwann cells) around a peripheral axon; not present around CNS axons.

Nodes of Ranvier

Gaps in the myelin sheath along a myelinated axon where voltage-gated channels are concentrated.

Myelinated vs unmyelinated appearance

Myelinated fibers have a myelin sheath and appear white and insulated; unmyelinated fibers lack a myelin sheath and conduct signals more slowly.

Effect of degraded myelin

Slowed or blocked nerve conduction; impaired signal transmission (e.g., multiple sclerosis–like effects).

Myelin producers in brain, spinal cord, and nerves

CNS myelin: oligodendrocytes; PNS myelin: Schwann cells; brain/spinal cord: oligodendrocytes; nerves: Schwann cells.

Demyelinating disorder involving the immune system

Multiple sclerosis (MS); autoimmune attack on CNS myelin with scar tissue formation.

Structural neuron types and locations

Multipolar (most CNS and motor neurons), bipolar (special senses, e.g., retina, olfactory, cochlear), unipolar/pseudounipolar (sensory neurons in PNS).

Sensory, motor, and interneurons comparison

Sensory (afferent): carry impulses to CNS; Motor (efferent): carry impulses from CNS to muscles/glands; Interneurons: reside within CNS and integrate signals.

Efferent vs afferent neurons

Efferent: motor neurons (CNS to effectors); Afferent: sensory neurons (receptors to CNS).

Clues to identify neuron type if not told

Cell body location and axon/dendrite arrangement; unipolar (often sensory in PNS) vs multipolar (often motor or interneurons in CNS).

PNS vs CNS neuron classifications

PNS: many unipolar (sensory) and multipolar (motor) neurons; CNS: mostly multipolar interneurons.

Unipolar neurons

Sensory/afferent neurons that have a single process from the cell body (pseudo-unipolar), located mainly in the PNS.

Clustered neuron cell bodies names in PNS vs CNS

PNS: ganglia; CNS: nuclei.

Functions of astrocytes

Support neurons; form blood–brain barrier; provide nutrients; regulate ion balance; repair and maintenance.

Neuroglia and their CNS vs PNS locations

CNS glia: astrocytes, oligodendrocytes, microglia, ependymal cells; PNS glia: Schwann cells and satellite cells; they support and protect neurons.

Why PNS axons regenerate but CNS axons do not

PNS has Schwann cells guiding regeneration and a permissive environment; CNS is inhibited by factors from oligodendrocytes and glial scarring and lacks a supportive neurilemma.

Resting membrane potential vs action potential

Resting: baseline polarized state (inside negative). Action potential: rapid, all-or-none depolarization and repolarization traveling along the axon.

All-or-none principle

An action potential either occurs at full amplitude or not at all; its size is independent of stimulus strength once threshold is reached.

Polarized, depolarized, hyperpolarized states

Polarized: resting state with a negative inside; depolarized: membrane potential becomes less negative; hyperpolarized: more negative than resting potential.

What causes depolarization

Opening of voltage-gated Na+ channels and Na+ influx into the neuron.

When do voltage-gated Na+ gates open

At threshold (approximately -55 mV) during the initiation of an action potential.

Events after reaching threshold (sequence)

Na+ channels open → rapid depolarization → Na+ channels inactivate; K+ channels open → repolarization → sometimes hyperpolarization; Na+/K+ pump restores resting state.

What is an impulse

An action potential that propagates along a neuron, transmitting information.

How stronger impulses are generated

Higher frequency of action potentials or recruitment of more neurons (frequency coding) rather than larger amplitude.

Relative refractory period

A period after the absolute refractory period when a stronger-than-normal stimulus can trigger a new action potential (only if stimulus is strong enough).

Absolute refractory period

A period when no stimulus can trigger another action potential because Na+ channels are inactivated.

Saltatory conduction

Rapid nerve impulse conduction along a myelinated axon, where the impulse jumps between nodes of Ranvier, increasing speed.

Which neurons carry impulses fastest vs slowest

Fastest: myelinated, large-diameter neurons (A fibers); slowest: unmyelinated, small-diameter (C fibers).

Synapse

The space (synaptic cleft) between two neurons where communication occurs via neurotransmitters.

Vesicles within neurons

Membrane-bound sacs in the terminals that store neurotransmitters awaiting release.

Release of neurotransmitter

Calcium influx triggers vesicle fusion with the presynaptic membrane and exocytosis of neurotransmitter.

Impulse transmission between neurons

Neurotransmitter release into the synaptic cleft, binding to postsynaptic receptors, and generation of postsynaptic potentials.

EPSP and IPSP

EPSP: excitatory postsynaptic potential (depolarizing); IPSP: inhibitory postsynaptic potential (hyperpolarizing).

When an action potential fires with EPSP/IPSP

When the summed postsynaptic potentials reach threshold and depolarize the membrane to fire an action potential.

Total input a CNS neuron can receive

Hundreds to thousands of synaptic inputs from other neurons.

Neurotransmitter that controls skeletal muscle contraction

Acetylcholine (ACh) at the neuromuscular junction.

Reuptake of a neurotransmitter

Reabsorption of neurotransmitter by the presynaptic neuron, terminating the signal.

Monoamines/biogenic amines examples

Dopamine, norepinephrine (noradrenaline), epinephrine (adrenaline), serotonin, histamine.

Neurotransmitter involved in feelings of well-being

Dopamine (also serotonin contributes to mood regulation).

MAOIs and their effect

Monoamine oxidase inhibitors prevent breakdown of monoamines, increasing their levels and prolonging signaling.

Why opiates relieve pain

Opiates mimic endogenous opioids by binding to opioid receptors, inhibiting pain pathways.

Neuronal pools

Groups of interconnected neurons in the CNS that process specific kinds of information; may contain divergent or convergent circuits.

Subthreshold stimulus

A stimulus that is too weak to reach threshold and generate an action potential.

Convergence

Many neurons synapsing onto a single neuron, allowing integration of diverse inputs.

Divergence

One neuron sending signals to many neurons, distributing information to multiple pathways and amplifying the overall response.

Convergent vs divergent pattern

Convergent: many inputs to a single output; Divergent: one input to many outputs.