Nervous System and Synaptic Transmission Flashcards

Vocabulary practice flashcards covering the organization of the central and peripheral nervous systems, cellular components, action potential mechanisms, nerve impulse conduction types, and synaptic transmission.

Homeostasis

The state of internal balance in the body maintained through the integrated functions of the nervous and endocrine systems.

Irritability

The capacity of an organism to capture various stimuli through sensory organs and generate a response.

Endocrine Regulation

A control mechanism where glands release hormones into the bloodstream, traveling long distances to produce slow and long-lasting responses.

Nervous Regulation

A control mechanism where neurons release neurotransmitters across the synaptic space over short distances, producing rapid and short-duration responses.

Central Nervous System (CNS)

The primary control division of the nervous system consisting of the encephalon (brain, cerebellum, diencephalon, and brainstem) and the spinal cord.

Spinal Cord

A nerve cord extending below the medulla oblongata that acts as the main communication pathway between the encephalon and the body, and participates in reflex responses.

Cerebrum

The largest structure of the encephalon that serves as the control center for voluntary movements, learning, memory, language, intelligence, and emotions.

Cerebellum

The second largest structure of the encephalon, located posteriorly beneath the cerebrum, which coordinates movements and maintains body posture balance.

Thalamus

A structure of the diencephalon that receives the majority of sensory nerve information from other CNS structures and distributes it to specific areas of the cerebrum.

Hypothalamus

A diencephalic structure regulating body temperature, hunger, thirst, sleep-wake cycles, gland secretions, and autonomic system control.

Brainstem

The neural structure composed of the midbrain, pons, and medulla oblongata that connects the encephalon to the spinal cord, controlling blood pressure, heart rate, respiration rate, swallowing, coughing, and hiccups.

Somatic Nervous System (SNS)

A division of the peripheral nervous system's effector branch that controls voluntary movements of skeletal muscles.

Autonomic Nervous System (ANS)

A division of the peripheral nervous system regulated by the hypothalamus that controls involuntary actions of cardiac muscle, smooth muscle, and glands.

Sympathetic Nervous System

A subdivision of the autonomic nervous system that prepares the body for action during alarm or threat by accelerating heart and breathing rates, dilating pupils, drying the mouth, and contracting sphincters.

Reflex Arc

The complete pathway of structures (receptor, afferent neuron, integration center, interneuron, efferent neuron, and effector) involved in producing a rapid, involuntary reflex response.

Effector

A muscle or gland structure in a reflex arc that executes a response following a stimulus.

Neurons

Highly differentiated, quiescent cells residing in the $G_0$ phase of the cell cycle that process and transmit electrical signals called nerve impulses.

Neuroglia (Glial Cells)

Non-impulse conducting cells that outnumber neurons and provide structural support, nutrition, and other maintenance functions within the nervous system.

Resting Membrane Potential

The polarized electrical potential across a non-conducting neuron's axon membrane, measured at $-70\,mV$.

Sodium-Potassium Pump (Na+/K+-ATPase)

An active transport membrane pump that expels $3\,\text{Na}^+$ ions and imports $2\,\text{K}^+$ ions using ATP to maintain resting potential.

Depolarization

The phase of an action potential caused by a stimulus opening voltage-gated $\text{Na}^+$ channels, leading to a rapid influx of $\text{Na}^+$ that turns the axon interior positive.

Repolarization

The phase of an action potential where voltage-gated $\text{Na}^+$ channels close and voltage-gated $\text{K}^+$ channels open, allowing $\text{K}^+$ to exit and restoring internal negativity.

Hyperpolarization

A phase in an action potential where voltage-gated $\text{K}^+$ channels remain open slightly longer than necessary, making the interior membrane potential more negative than $-70\,mV$.

Firing Threshold

The critical membrane potential level ($-55\,mV$) that must be reached or exceeded by a stimulus to generate an action potential.

Absolute Refractory Period

The timeframe during depolarization and most of repolarization when a neuron cannot generate a second action potential, regardless of stimulus strength.

Relative Refractory Period

The period near the end of repolarization and during hyperpolarization when a second action potential can be triggered only if the stimulus is stronger than normal.

All-or-None Law

The principle stating that if a stimulus reaches or exceeds the $-55\,mV$ threshold, a full action potential of constant amplitude and frequency is generated; otherwise, no action potential occurs.

Saltatory Conduction

The rapid and energy-efficient propagation of an impulse along myelinated axons, where the action potential jumps between Nodes of Ranvier.

Continuous Conduction

The slower and less energy-efficient propagation of an impulse along unmyelinated axons, sequentially depolarizing each adjacent membrane segment.

Chemical Synapse

A type of synapse where an arriving action potential opens voltage-gated $\text{Ca}^{2+}$ channels, driving $\text{Ca}^{2+}$ influx that triggers exocytosis of neurotransmitters into the synaptic cleft.

Electrical Synapse

A direct neural connection where electrical current flows bidirectionally between neurons through gap junction channels called connexons without neurotransmitter release.