Nervous System Test Prep

Vocabulary flashcards covering neuron anatomy, action potentials, neuroglia, nervous system divisions, reflex arcs, brain anatomy, and cerebral landmarks for Nervous System test preparation.

Neuron Anatomy

The fundamental structural and functional unit of the nervous system, typically consisting of dendrites to receive impulses, a cell body (soma) containing the nucleus, an axon to conduct action potentials, a myelin sheath with Schwann cells, and axon terminals.

Dendrite

A branching, threadlike extension of a neuron that receives incoming nerve impulses from other cells and conducts them toward the cell body.

Axon

A long, slender projection of a nerve cell that conducts electrical impulses away from the cell body toward axon terminals.

Myelin Sheath

An insulating lipid layer wrapped around the axon that dramatically increases the speed of nerve impulse propagation.

Action Potential

A rapid, temporary change in the electrical membrane potential of an excitable cell across its membrane that propagates signals along an axon.

Action Potential Stages

The sequence of electrical voltage phases across the membrane: resting membrane potential at $-70\,mV$ (1), threshold at $-55\,mV$ (2), depolarization rising to $+30\,mV$ (3), repolarization (4), and hyperpolarization (5).

Resting Membrane Potential

The stable electrical voltage across the plasma membrane of a resting neuron, typically measured at approximately $-70\,mV$.

Threshold Potential

The critical membrane voltage (approximately $-55\,mV$) that must be reached to open voltage-gated sodium channels and trigger an all-or-none action potential.

Depolarization

The phase of an action potential characterized by a massive influx of sodium ions ($Na^+$), driving the membrane potential from negative toward positive values (up to $+30\,mV$).

Repolarization

The falling phase of an action potential where voltage-gated potassium channels open, allowing potassium ions ($K^+$) to flow out and restore a negative membrane potential.

Hyperpolarization

The brief dip in membrane potential where the cell becomes more negative than the resting potential (undershoot below $-70\,mV$) due to delayed closing of potassium channels.

Saltatory Conduction

The rapid mode of nerve impulse conduction occurring in myelinated axons, where the action potential jumps from one node of Ranvier to the next, unlike the slower continuous conduction in unmyelinated axons.

Synaptic Cleft

The tiny extracellular gap between a presynaptic axon terminal and a postsynaptic membrane across which chemical neurotransmitters diffuse.

Neurotransmitters

Endogenous chemical messengers (such as acetylcholine) stored in synaptic vesicles within the axon terminal and released into the synaptic cleft to transmit signals.

Satellite Cells

Glial cells located in the Peripheral Nervous System (PNS) that surround and support neuron cell bodies within ganglia.

Schwann Cells

Glial cells of the Peripheral Nervous System (PNS) responsible for forming the insulating myelin sheath around peripheral axons.

Oligodendrocytes

Glial cells located in the Central Nervous System (CNS) that produce and wrap myelin sheaths around multiple central nerve axons.

Microglia

Specialized immune glial cells of the Central Nervous System (CNS) that act as phagocytes to clear cellular debris, waste, and pathogens.

Astrocytes

Star-shaped neuroglial cells of the Central Nervous System (CNS) that provide structural support, regulate the extracellular chemical environment, and maintain the blood-brain barrier.

Ependymal Cells

Epithelial-like glial cells of the Central Nervous System (CNS) that line the ventricles of the brain and the central canal of the spinal cord, assisting in the production and circulation of cerebrospinal fluid.

Three General Functions of the Nervous System

Sensory input (monitoring internal and external environments), Integration (processing and interpreting sensory data), and Motor output (activating effector organs such as muscles and glands).

Central Nervous System (CNS)

The major division of the nervous system consisting of the brain and spinal cord, serving as the master control and integration center.

Peripheral Nervous System (PNS)

The division of the nervous system outside the CNS, composed of cranial and spinal nerves that connect the CNS to limbs, skin, and organs.

Somatic Nervous System

The voluntary motor division of the PNS that conveys impulses from the CNS to skeletal muscles.

Autonomic Nervous System

The involuntary motor division of the PNS that regulates smooth muscle, cardiac muscle, and glands.

Sympathetic Nervous System

The autonomic division that prepares the body for action, driving the "fight-or-flight" response by increasing heart rate and energy mobilization.

Parasympathetic Nervous System

The autonomic division that conserves energy and promotes maintenance functions, facilitating the "rest-and-digest" response.

Reflex

A rapid, automatic, involuntary motor response to a specific sensory stimulus designed to protect the body from harm.

Reflex Arc

The neural pathway mediating a reflex action, composed sequentially of a sensory receptor/neuron, an integration center within the CNS, and a motor neuron targeting an effector.

General Sensory Nerve Impulse Pathway

The route taken by sensory input: from a peripheral sensory receptor through the PNS via afferent sensory fibers into the CNS (spinal cord and brain) for processing.

Midsagittal Brain Anatomy

A sagittal view of the brain showing major structures including the cerebellum (1), cerebrum (2, 3, 5), corpus callosum (4), diencephalon (6, 7), pons (8), and medulla oblongata (9).

Cerebellum

The structure at the base and posterior part of the brain responsible for coordination of voluntary motor movements, balance, and posture.

Brainstem

The stalk-like region connecting the cerebrum to the spinal cord, consisting of the midbrain, pons, and medulla oblongata, which governs vital autonomic functions.

Midbrain

The uppermost portion of the brainstem that coordinates visual and auditory reflex pathways as well as motor movements.

Pons

The bulging middle region of the brainstem that acts as a bridge connecting brain regions and assists in regulating respiration.

Medulla Oblongata

The lowermost segment of the brainstem continuous with the spinal cord, controlling critical autonomic centers including cardiac, vasomotor, and respiratory rates.

Cerebrum

The largest part of the brain, composed of right and left hemispheres, responsible for complex sensory integration, voluntary motor output, reasoning, memory, and consciousness.

Diencephalon

The central core region of the brain beneath the cerebral hemispheres, encompassing the thalamus, hypothalamus, and epithalamus.

Thalamus

A large paired sensory relay hub in the diencephalon that sorts and directs incoming sensory signals (except olfaction) to the appropriate cerebral cortical areas.

Hypothalamus

A region of the diencephalon situated below the thalamus that regulates autonomic activity, body temperature, hunger, thirst, and endocrine function via the pituitary gland.

Limbic System

A complex network of brain structures located in the cerebrum and diencephalon primarily involved in emotion, motivation, memory formation, and behavior.

Meninges

The three protective connective tissue membranes covering the brain and spinal cord, ordered from outermost to innermost: dura mater, arachnoid mater, and pia mater.

Frontal Lobe

The anterior lobe of the cerebrum involved in voluntary motor control, decision making, problem solving, personality, and expressive speech.

Parietal Lobe

The superior and middle cerebral lobe responsible for processing somatic sensory information including touch, temperature, pain, and spatial orientation.

Temporal Lobe

The lateral lobe of the cerebral cortex responsible for hearing, language interpretation, and aspects of memory.

Occipital Lobe

The posterior lobe of the cerebral hemisphere dedicated primarily to visual reception and visual processing.

Broca Area

A specialized region typically located in the frontal lobe of the dominant hemisphere responsible for planning and executing the motor movements of speech production.

Motor Cortex

The region located on the precentral gyrus of the frontal lobe that controls and executes voluntary muscle contractions throughout the body.

Sensory Cortex

The primary somatosensory cortex located on the postcentral gyrus of the parietal lobe that receives and interprets general tactile sensory inputs from the body.

Cerebral Landmarks and Cortical Regions

Lateral view of the brain showing cortical functional zones including the motor cortex (3), sensory cortex (5), central sulcus (4), lateral sulcus, and Broca's area (14/15).

Longitudinal Fissure

The deep groove running midsagittally along the superior brain surface that separates the left cerebral hemisphere from the right cerebral hemisphere.

Transverse Fissure

The deep horizontal groove that separates the occipital lobes of the cerebrum from the underlying cerebellum.

Central Sulcus

The groove on the lateral surface of the cerebral cortex separating the frontal lobe (precentral gyrus/motor cortex) from the parietal lobe (postcentral gyrus/sensory cortex).

Lateral Sulcus

The prominent deep fissure that demarcates and separates the temporal lobe inferiorly from the frontal and parietal lobes superiorly.