Nervous Tissue and Nervous System Basics

Comprehensive vocabulary flashcards covering nervous system organization, glial cell types, neuron structure and classification, membrane potentials, synaptic transmission, and neurotransmitters according to the lecture notes.

Sensory Input

The function of the nervous system to detect changes in the environment.

Integration

The function of evaluating information within the nervous system.

Motor Output

The response initiated by the nervous system, often to achieve homeostasis.

Central Nervous System (CNS)

The integration and control center consisting of the brain and spinal cord.

Peripheral Nervous System (PNS)

The part of the nervous system that relays signals to and from the CNS via cranial and spinal nerves.

Afferent Division

The incoming or sensory pathway of the PNS.

Somatic Sensory Fibers

Sensory fibers that transmit impulses from the skin, muscles, and joints.

Visceral Sensory Fibers

Sensory fibers that transmit impulses from visceral organs.

Efferent Division

The motor division of the PNS that initiates and transmits information from the CNS to effectors.

Somatic Nervous System (SNS)

The voluntary part of the motor division that controls skeletal muscle.

Autonomic Nervous System (ANS)

The involuntary motor control of smooth muscle, cardiac muscle, and glands; includes the sympathetic and parasympathetic divisions.

Glia (Neuroglia)

Support cells of the nervous system that are able to divide; also known as 'glue'.

Astrocytes

The largest and most numerous central glia that attach neurons to capillaries, normalize $K^+$ levels, and form the blood-brain barrier.

Microglia

Small central glia that migrate in damaged tissue to phagocytize microorganisms and debris, and 'prune' unnecessary processes.

Ependymal Cells

Epithelial-like cells that line fluid-filled cavities; some are ciliated and move fluid.

Oligodendrocytes

Central glia that hold nerve fibers together and produce the myelin sheath to increase impulse speed.

Schwann Cells (Neurolemmocytes)

Peripheral glia that wrap around nerve fibers to form myelin sheaths in the PNS.

Satellite Cells

Specialized Schwann cells that surround cell bodies in ganglia to insulate them and regulate nutrient/waste exchange.

Chromatophilic Substance

The combination of endoplasmic reticulum and ribosomes found within a neuron's cell body.

Nuclei

Clusters of neuron cell bodies located within the CNS.

Ganglia

Clusters of neuron cell bodies located within the PNS.

Dendrites

Branch-like extensions of a neuron that receive stimuli and conduct signals toward the soma.

Axon Hillock

The region of the neuron cell body where the axon originates.

Tracts

Bundles of axons located within the CNS.

Nerves

Bundles of axons located within the PNS.

Antegrade Movement

Axonal transport moving away from the cell body.

Retrograde Movement

Axonal transport moving toward the cell body.

Multipolar Neurons

Neurons with one axon and several dendrites; most common in the CNS and found in motor neurons.

Bipolar Neurons

Neurons with one axon and one highly branched dendrite; found in special senses and interneurons.

Unipolar (Pseudounipolar) Neurons

Neurons with a single process branching off the body that divides into a central and peripheral process; typical of somatic sensory neurons.

Anaxonic Neurons

Neurons with only dendrites that produce graded potentials but no action potentials.

Interneuron

A neuron within a reflex arc that connects afferent neurons to efferent neurons.

Resting Membrane Potential (RMP)

The electrical charge difference across the plasma membrane at rest, typically around $-70\,mV$ intracellularly.

Depolarization

A shift in membrane potential toward a less negative value, often caused by $Na^+$ entering the cell.

Hyperpolarization

A shift in membrane potential that makes it more negative than the RMP, such as when $K^+$ exits the cell.

Graded Potentials

Local shifts in RMP where the magnitude of deviation is proportional to the stimulus and conduction is decremental.

Action Potential

An 'all-or-none' nerve impulse triggered when local depolarization reaches the threshold potential.

Threshold Potential

The membrane potential level, typically $-55\,mV$, required to open voltage-gated $Na^+$ channels and trigger an action potential.

Absolute Refractory Period

The time following stimulation during which the neuron is completely unresponsive to further stimuli.

Relative Refractory Period

The period during RMP restoration when the neuron can only respond to very strong stimuli.

Saltatory Conduction

Conduction in myelinated fibers where depolarization 'jumps' from one neurofibril node to another.

Synaptic Cleft

The gap between the presynaptic neuron and the postsynaptic cell in a chemical synapse.

Excitatory Postsynaptic Potential (EPSP)

A postsynaptic potential that results in depolarization, typically by opening chemically gated cation channels.

Inhibitory Postsynaptic Potential (IPSP)

A postsynaptic potential that results in hyperpolarization, typically by opening chemically gated $K^+$ and/or $Cl^-$ channels.

Spatial Summation

The summation of multiple local potentials from different presynaptic neurons at the axon hillock.

Temporal Summation

The summation of local potentials occurring in rapid succession from a single presynaptic neuron.

Neuromodulation

The process by which chemicals alter the strength of a synaptic connection without direct EPSPs or IPSPs.

Indirect Mechanism (2nd Messenger Model)

Neurotransmitter action where binding to G protein-coupled receptors initiates a chemical chain reaction to open or close channels.

Acetylcholine (ACh)

A neurotransmitter that stimulates skeletal muscle contraction and is broken down by acetylcholinesterase.

Dopamine

A biogenic amine, mostly inhibitory, involved in emotions, moods, and motor control; linked to Parkinson's disease.

Serotonin

A monoamine found in the CNS that is mostly inhibitory and affects mood, emotions, and sleep.

Gama-aminobutyric acid (GABA)

The primary inhibitory amino acid neurotransmitter in the brain.

Substance P

A peptide neurotransmitter in the CNS and PNS that transmits pain signals.

Endorphins

Peptide neurotransmitters in the CNS and PNS that provide analgesia.

Converging Circuit

A neural network where multiple presynaptic neurons synapse with a single postsynaptic neuron, such as in breathing rate control.

Diverging Circuit

A neural network where a single presynaptic neuron synapses with multiple postsynaptic neurons, such as in skeletal muscle contraction.

Reverberating Circuit

An oscillating neural network where successive neurons feedback to prior neurons to produce rhythmic activity like sleep.

Neuroplasticity

The ability of the nervous system to change through the formation of new synapses or the removal of old ones.

Myasthenia Gravis

An autoimmune synaptic disorder where antibodies bind to ACh receptors at neuromuscular junctions.