Nervous Tissue: Flash Cards

Neurons & Nervous System Structure

Neural Communication & Action Potentials

Synapses & Neurotransmitters

Sensory Systems & Receptors

• 1st, 2nd, 3rd order neuronsThe functional cells of the nervous system that transmit signals.: Sensory neurons relaying signals to the brain.
  • 1st order: From sensory receptorsProteins located on the surface or inside cells that bind specific molecules (e.g., neurotransmitter to the CNSComposed of the brain and spinal cord; integrates and processes information. .
  • 2nd order: From spinal cordThe central nervous system structure that relays signals between the brain and body./brainstem to the thalamusThe brain’s relay center, sending sensory information to the cerebral cortex..
  • 3rd order: From thalamus to the cerebral cortexThe outermost layer of the brain, responsible for higher-order thinking and processing..

A

• Absolute refractory period: The period during which a neuron cannot fire another action potentialA rapid, temporary electrical charge that travels along neurons, allowing signal transmission., no matter the stimulus.
• Acetylcholine (ACh): Neurotransmitter involved in muscle contraction, autonomic functions, and cognition.
• Action potential: Rapid electrical impulse traveling along a neuron’s membrane.
• Adrenergic synapses: Synapses using norepinephrineA neurotransmitter involved in attention, arousal, and the fight-or-flight response. as a neurotransmitterChemicals that transmit signals across synapses..
• All-or-nothing principle: Action potentials either occur fully or not at all.
• Anaxonic neurons: Neurons without a distinct axon, functioning in CNS communication.
• Anterograde transport: Movement of materials from the somaThe central part of a neuron containing the nucleus and organelles. to the axon terminalThe endpoint of an axon where neurotransmitters are stored and released into a synapse..
• Astrocytes: Star-shaped CNS glial cellsThe basic structural and functional units of life. maintaining the blood-brain barrierA selective barrier that prevents harmful substances from entering the brain. and neurotransmitter regulation.
• Axolemma: The axon’s plasma membraneThe outer boundary of a cell that controls what enters and exits..
• Axon (nerve fiber): Long neuron projection transmitting electrical impulses.
• Axon collaterals: Axon branches allowing multiple target communication.
• Axon hillock: Cone-shaped region where action potentials initiate.
• Axon terminal: End of an axon where neurotransmittersChemicals released by neurons to transmit signals across a synapse. release.
• Axonal transport: Movement of organellestructures within a cell that perform specialized functions. and neurotransmitters within an axon.

B-C

• Bipolar neuron: One axon, one dendrite; found in sensory organs.
• Bulbous corpuscles (Ruffini endings): Slow-adapting mechanoreceptorsReceptors that respond to mechanical stimuli such as touch or pressure. detecting pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange. and stretch.
• CatecholaminesNeurotransmitters derived from tyrosine: dopamine, norepinephrine, and epinephrine.: Neurotransmitters including dopamineA catecholamine neurotransmitter involved in motor control, motivation, and reward., norepinephrine, and epinephrineadrenaline): Fight-or-flight hormone from the adrenal medulla..
• Cell body (soma): Contains neuron nucleusThe control center of the cell that contains DNA and directs cellular activities. and organelles.
• Cell-adhesion moleculesGroups of atoms bonded together. (CAMs): Proteins aiding cellular adhesionThe tendency of water molecules to stick to other substances., crucial in neural developmentThe process of growth and differentiation..
• Chemical synapses: Synapses using neurotransmitters for signal transmission.
• ChemoreceptorsSensory receptors that detect chemical stimuli, such as odors or blood pH.: Receptors detecting chemical stimuliChanges in the environment that are detected by sensory receptors. (e.g., taste, smell).
• Cholinergic synapses: Synapses using acetylcholinealso know as ACh A neurotransmitter that stimulates muscle contraction..
• CNS (Central Nervous System): Brain and spinal cord.

• Conductivity: Neuron’s ability to transmit electrical signals.
• Continuous conductionThe transmission of nerve impulses along neurons.: Signal transmission in unmyelinated axons.
• Current: Flow of charged particles, essential for nerve function.

D-E

• Deep somatic pain: Pain from muscles, joints, and bones.
• Dendrites: Extensions receiving signals from other neurons.
• Depolarization: Neuron’s membrane potential becoming less negative, leading to action potential.
• Diffusion: Passive movementA fundamental property of life involving motion of the body or its parts. of molecules, including neurotransmitter release.
• Dopamine: Neurotransmitter regulating movement, motivation, and pleasure.
• Dynein: Motor protein facilitating retrograde transportMovement from the axon terminal back toward the neuron’s cell body (via dynein)..

• Electrical potential: Voltage difference across a neuron’s membrane.
• Electrical synapses: Synapses with direct ion flow via gap junctions.
• Encapsulated endings: Sensory receptors enclosed in connective tissue.
• End bulbs (Krause’s corpuscles): Sensory receptors detecting cold and touch.
• Endoneurium: Connective tissue surrounding individual nerve fibers.
• Ependymal cells: CNS glial cells producing cerebrospinal fluid(CSF) – A fluid that cushions and nourishes the brain and spinal cord..
• Epinephrine (adrenaline): Hormone and neurotransmitter in fight-or-flight response.
• Epineurium: Outermost connective tissue surrounding a nerve.
• Excitability: Neuron’s ability to respond to stimuli and fire action potentials.
• Excitatory local potential: Small depolarizationThe loss of electrical charge across a membrane, triggering an action potential. increasing action potential likelihood.
• Excitatory post synaptic potential (EPSP): Depolarizing potential increasing neuron firing probability.
• Exteroceptors: Receptors detecting external stimuli (e.g., touch, temperature).

F – I

• Fast pain: Sharp, localized pain via myelinated fibers.

• Free nerve endings: Unencapsulated receptors detecting pain, temperature, and touch.
• G proteinA signaling protein activated by neurotransmitter receptors that triggers internal cellular response: Signal transduction molecule activated by neurotransmitters.
• GABA (Gamma-aminobutyric acidA substance that releases hydrogen ions (H⁺) in solution.): Major inhibitory neurotransmitter in the CNS.
• Ganglion: Cluster of neuron cell bodies in the PNS.
• General senses: Touch, pain, temperature, and proprioception.
• Hair receptors: Sensory receptors at hair folliclesStructures in the ovaries that contain developing oocytes. detecting movement.
• Hyperpolarization: Membrane potential becomes more negative, reducing excitabilityA neuron’s ability to respond to stimuli by generating an electrical signal..
• Inhibitory post synaptic potential (IPSP): Hyperpolarizing potential decreasing action potential likelihood.

• Interneurons: Neurons connecting sensory and motor pathways within the CNS.

K – N

• Kinesin: Motor protein aiding anterograde transportMovement of materials from the neuron’s cell body down the axon toward terminals (via kinesin)..
• Labeled line coding: Neural pathway specificity for distinct sensory inputs.

• Motor (efferent) division: Carries signals from CNS to effectors.
• Motor neurons: Neurons controlling muscles and glands.
• Multipolar neuron: Multiple dendritesBranch-like extensions from a neuron that receive signals from other neurons., one axon; common in CNS.
• Myelin sheath: Fatty layer around axons increasing conduction speed.
• Myelination: Formation of the myelin sheathA fatty covering around axons that increases conduction speed..
• Nervous system: Network coordinating body functions.
• Neural integration: Neurons processing information for response generation.
• Neurofibrils: Cytoskeletal elements maintaining neuron shape.
• Neuroglia: Supportive glial cells in the nervous systemThe organ system that controls body functions using electrical and chemical signals..
• Neurolemma: Outer layer of Schwann cellsPNS glial cells that form the myelin sheath around peripheral nerve fibers. in PNS.
• Neuromodulators: Substances altering neurotransmitter release.
• Neurons: Excitable cells transmitting nerve signals.
• Neuropeptides: Small protein-like neurotransmitters.
• Neurotransmitter degradation: Breakdown of neurotransmitters post-synaptic binding.
• Neurotransmitters: Chemical messengers transmitting signals between neurons.
• Nociceptors: Pain-detecting sensory receptors.
• Node of Ranvier: Gaps in the myelin sheath facilitating saltatory conductionThe rapid transmission of impulses in myelinated axons by jumping between nodes of Ranvier..
• Norepinephrine: Neurotransmitter in alertness and autonomic functions.

O – P

• Oligodendrocytes: CNS glial cells producing myelin.
• Parasympathetic division: Autonomic system branch promoting rest-and-digest activities.
• Perception: Brain’s interpretation of sensory input.
• Perineurium: Connective tissue surrounding nerve fasciclesBundles of nerve fibers within a nerve.
  or
  Bundles of nerve fibers within a muscle..
• Peripheral processes: Sensory neuron extensions toward receptors.
• Phasic receptors: Rapidly adapting receptors detecting stimulus changes.
• PNS (Peripheral Nervous System): Nerves outside CNS.
• Polarized: Resting neuron’s negative membrane potential.
• Postsynaptic delay: Time between neurotransmitter release and postsynaptic response.
• Presynaptic neuron: Neuron releasing neurotransmitter.

R – T

• Referred pain: Pain felt at a different location than its origin.
• Regeneration tube: Structure guiding axon regrowth.
• Relative refractory period: Period where a stronger stimulus is needed for action potential.
• Repolarization: Restoration of resting membrane potential.
• Saltatory conduction: Fast action potential transmission in myelinated axons.
• Schwann cells: PNS glial cells producing myelin.
• Synapse: Neuronal communication junction.
• Threshold: Minimum stimulus for action potential initiation.
• Tonic receptors: Sensory receptors that adapt slowly to stimuli and continue to generate nerve impulses as long as the stimulus is present (e.g., pain receptors, proprioceptorsSensory receptors that monitor the position and movement of the body.).

U – Z

Unencapsulated endings: Sensory nerve endings that lack a connective tissue covering, making them more sensitive to stimuli (e.g., free nerve endingsUnencapsulated receptors that detect pain, temperature, and crude touch., Merkel discs).

Unipolar neuron: A type of neuron with a single extension. This extension branches into a peripheral process for sensory input. It also forms a central process for signal transmission to the CNS. This type is common in sensory pathways.

Visceral motor division(Efferent Division) Part of the PNS that carries signals from the CNS to muscles and glands. (ANS): The part of the autonomic nervous systemThe part of the peripheral nervous system that controls involuntary functions such as heart rate, di (ANS) controlsVariables that remain constant to ensure a fair test. involuntary functions. It regulates smooth muscle, cardiac muscle, and glands. This includes the sympathetic and parasympathetic divisions.

Visceral pain: Pain that arises from internal organs (viscera) due to stretch, ischemia, or chemical irritation. This type of pain is often dull and difficult to localize.

• Visceral sensory: This is the part of the nervous system that transmits sensory information from internal organs to the CNS. It includes sensations like stretch, temperature, and pain in the viscera.