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The part of the nervous system regulating organs, glands and related internal functions. It includes the sympathetic nervous system and parasympathetic nervous system. Its activity supports bodily regulation during emotion, exercise and many nonemotional states; no single recording is a direct readout of a private feeling.

A cognitive neuroscientist investigates how the nervous system supports cognition, including memory retention, attention and perception. Combining behavioral measurements with recordings or perturbations helps distinguish association from a causal contribution.

A computational neuroscientist develops or analyzes quantitative models of the nervous system. A model can connect a proposed mechanism to measurable neuron activity or animal behaviour, making its assumptions and predictions explicit.

Ejaculation moves semen through and out of the urethra. In male reproductive physiology, emission brings sperm and glandular fluids into the urethra, while expulsion uses coordinated muscular contractions to discharge them. Contributions from the autonomic nervous system and somatic nervous system couple secretion and transport with the activity of skeletal muscles.

The coordination involves the spinal cord, rather than being an isolated contraction of one reproductive organ. A rat experiment identified a population of spinal neurons whose loss disrupted ejaculation while leaving other components of mating behavior relatively preserved.^[ref] The result supports a spinal cord coordinating mechanism in that animal model; it does not by itself establish that every aspect of human ejaculation or sexual experience has the same organization of the nervous system.

An enhancer trap is a reporter gene arrangement used to reveal regulatory activity near its genomic insertion site. A weak promoter drives a measurable reporter; nearby enhancers can alter its expression in particular cells or developmental stages. The observed pattern therefore turns otherwise invisible gene regulation into a measurable output. It does not require the experimenter to begin with a visible mutant phenotype.^[ref]

In the original Drosophila study by C. J. O'Kane and W. J. Gehring, the reporter encoded beta-galactosidase. About 70% of 49 transformed lines showed spatially regulated expression in embryos, including patterns in the nervous system. The informative comparison is between insertion contexts: the reporter acts as a sensor of the regulatory environment rather than as a direct readout of one preselected native gene.^[ref]

For an illustrative interpretation, reporter activity in one tissue and not another suggests a difference in the regulatory inputs available there. It does not alone identify the responsible enhancer, prove its exact native target, or establish that every native expression feature has been reproduced. Those questions require additional evidence.

A physiologist whose investigations connected digestion, glandular secretion and nervous system control. Preparations separating entry of food from its arrival in the stomach allowed experiments on anticipatory gastric acid secretion, contributing to the study of classical conditioning.^[ref]

A physiologist associated with the experimental development of classical conditioning.^[ref]

Lyme disease is a tick-borne bacterial infection caused by members of the Borrelia burgdorferi species complex and transmitted by infected Ixodes ticks. Early illness can include fever, fatigue and an expanding rash called erythema migrans; later involvement can affect joints, the nervous system or the heart. The rash has varied appearances and need not form a textbook bullseye.^[ref]

The bacterial link emerged from a specific line of evidence. In 1982, Willy Burgdorfer and colleagues reported spirochaetes in ticks from an affected area, cultivation of the organisms, and reactions with antibodies from patients with Lyme disease. This connected a vector-associated organism to the human illness, rather than inferring a cause from an association with outdoor exposure alone.^[ref]

Michael S. Brainard is a researcher in neuroscience who studies how experience shapes sensorimotor learning. His work uses songbirds to connect measured behavior with the activity of the nervous system. Song offers a particularly useful task because a young bird first hears a tutor and then uses auditory feedback to refine its own performance.^[ref]

In a 2009 study with Samuel J. Sober, adult Bengalese finches heard electronically shifted pitch through custom headphones. The birds changed their own pitch in the opposite direction and returned toward baseline when normal auditory feedback resumed. Thus an apparently stable adult skill could be actively maintained by feedback control, rather than being an unchanging motor program.^[ref]

Monocular deprivation is an experimental reduction of normal patterned vision through one eye while the other remains available. It is used to investigate how sensory experience shapes a developing nervous system. In classic cat experiments, researchers closed the eyelids of one eye for a stated interval, then reopened it and compared what the animal could do through each eye.^[ref]

P. B. Dews and colleagues varied both the starting age and duration of deprivation, testing the cats when they were at least a year old. Closure during the first four to six weeks left a lasting reduction in visual acuity. Longer early closure could also impair visually guided paw placement and pattern discrimination. Deprivation beginning at four months or later produced no lasting deficit detectable by their behavioural tests. The comparison identifies a critical period of heightened susceptibility in this species and experimental setting; it does not mean that all forms of adult neuroplasticity disappear.^[ref]

An illuminating feature of the design is its separation of when experience is lost from how long it is lost. A weak response immediately after opening an eye would not alone demonstrate a lasting developmental change; delayed testing and comparison with the other eye make that inference stronger.

Myelination forms layers of myelin around segments of an axon. Oligodendrocytes produce these sheaths in the central nervous system, while Schwann cells do so in the peripheral nervous system. Gaps, each called a node of Ranvier, allow action potentials to be regenerated between insulated segments, supporting saltatory conduction.

The arrangement affects when signals reach their targets, not just whether an axon is present. In mice, altered visual experience shortened segments wrapped in myelin along the optic nerve pathway and was associated with slower conduction along the optic nerve. The observations connected environmental input, myelin sheath geometry and a measured physiological consequence.^[ref] This experimental result does not imply that more myelin always produces a uniformly faster or better-performing nervous system; segment geometry and the timing required by a circuit matter.

The nervous system coordinates sensing, internal processing and responses through networks of neurons and supporting cells. Its organization connects rapid electrical signals with chemical communication. The central nervous system and peripheral nervous system describe major anatomical divisions.

Nervous tissue, also called neural tissue, is the organized tissue of the nervous system, containing neurons and glial cells. Neurons specialize in communication, including action potentials and signaling between cells. Glial cells maintain the local environment, form insulating myelin in particular locations, and perform other active functions. The brain, spinal cord and peripheral nerves contain different arrangements of these components; a drawing of one isolated neuron is not a complete picture of nervous tissue.^[ref]

A useful example is the median eminence, where hormone-releasing axon endings interact with tanycytes and blood-vessel endothelium. In a 2004 experiment, investigators compared female-rat tissue explants after 30 minutes with or without 500 micromolar arginine, a precursor for nitric oxide production. Electron microscopy showed identified gonadotropin-releasing hormone terminals close to the vascular boundary after treatment, with fewer intervening tanycyte processes than in controls.^[ref]

The observation makes tissue organization experimentally meaningful: changes in the position of a glial cell process can alter a neuron's access to a vascular interface. This specialized arrangement should not be mistaken for the structure of every synapse or every region of nervous tissue.

A neuroanatomist studies the structure and connections of the nervous system. Mapping a pathway establishes possible routes for communication; experiments are still needed to determine when and how those routes contribute to function.

Communication in which nervous system activity influences hormone release or neurosecretory products influence distant targets.

Neuroimaging measures structural or functional properties of the nervous system. Different methods record different physical signals, so anatomical images and activity-sensitive measurements support different inferences.

For example, electroencephalography records electrical potential differences, while many functional vascular measurements depend on neurovascular coupling. Spatial overlap in an image is not by itself proof that one location implements a complete psychological process.

A neurological deficit is loss or impairment of a function attributable to the nervous system, such as weakness, altered sensation or impaired language. Its distribution can constrain the location of a lesion, while its time course helps characterize the process.

For example, hemiplegia describes one-sided paralysis, whereas a sensory level describes a boundary in sensory findings. Neither observation alone identifies the complete underlying disease.

A neurological examination systematically assesses functions of the nervous system, including mental state, cranial nerves, strength, sensation, coordination and reflexes. Patterns across tasks can localize dysfunction more effectively than a single isolated score.

For example, apparent inability to perform a learned action can reflect elementary weakness, impaired comprehension or apraxia. Comparing the relevant component functions is essential to interpreting the failed action.

A neurological sign is an observed finding about the function of the nervous system, such as an altered reflex, asymmetrical movement or a sensory deficit. It differs from a symptom, which is an experience reported by the person. A neurological examination combines several observations because one finding can have several explanations. The pattern and its context help distinguish a possible mechanism or location of dysfunction. ^[ref]

A neurologist is a physician specializing in disorders of the nervous system. Clinical work combines the history and neurological examination with investigations to connect impaired functions to possible anatomical and physiological causes.

Neurology is the medical study of disorders affecting the nervous system. It connects changes in brain, spinal cord and peripheral nerve function to symptoms and examination findings, while using neuroscience to investigate the underlying mechanisms.

A neurological deficit is an observation to explain, rather than a diagnosis by itself. Comparing muscle strength, sensation, coordination and reflexes can help distinguish damage to different pathways even when two people report a similar difficulty.