Arousal is a
physiologicalPhysiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
and
psychologicalPsychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...
state of being awake or reactive to stimuli. It involves the activation of the
reticular activating systemThe reticular activating system is an area of the brain responsible for regulating arousal and sleep-wake transitions.- History and Etymology :...
in the
brain stemIn vertebrate anatomy the brainstem is the posterior part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves...
, the
autonomic nervous systemThe autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...
and the
endocrine systemIn physiology, the endocrine system is a system of glands, each of which secretes a type of hormone directly into the bloodstream to regulate the body. The endocrine system is in contrast to the exocrine system, which secretes its chemicals using ducts. It derives from the Greek words "endo"...
, leading to increased heart rate and blood pressure and a condition of sensory alertness, mobility and readiness to respond.
There are many different neural systems involved in what is collectively known as the arousal system. Four major systems originating in the brainstem, with connections extending throughout the cortex, are based on the brain's neurotransmitters,
acetylcholineThe chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...
,
norepinephrineNorepinephrine is the US name for noradrenaline , a catecholamine with multiple roles including as a hormone and a neurotransmitter...
,
dopamineDopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...
, and
serotoninSerotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...
. When these systems are in action, the receiving neural areas become sensitive and responsive to incoming signals.
Importance
Arousal is important in regulating
consciousnessConsciousness is a term that refers to the relationship between the mind and the world with which it interacts. It has been defined as: subjectivity, awareness, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive control system of the mind...
, attention, and information processing. It is crucial for
motivatingMotivation is the driving force by which humans achieve their goals. Motivation is said to be intrinsic or extrinsic. The term is generally used for humans but it can also be used to describe the causes for animal behavior as well. This article refers to human motivation...
certain behaviours, such as mobility, the pursuit of nutrition, the
fight-or-flight responseThe fight-or-flight response was first described by Walter Bradford Cannon....
and sexual activity (see
Masters and Johnson'sThe Masters and Johnson research team, composed of William H. Masters and Virginia E. Johnson, pioneered research into the nature of human sexual response and the diagnosis and treatment of sexual disorders and dysfunctions from 1957 until the 1990s....
human sexual response cycleThe human sexual response cycle is a four-stage model of physiological responses during sexual stimulation. These phases, in order of their occurrence, are the excitement phase, plateau phase, orgasmic phase, and resolution phase. The term was coined by William H. Masters and Virginia E...
, where it is known as the
arousal phase). It is also very important in
emotionEmotion is a complex psychophysiological experience of an individual's state of mind as interacting with biochemical and environmental influences. In humans, emotion fundamentally involves "physiological arousal, expressive behaviors, and conscious experience." Emotion is associated with mood,...
, and has been included as a part of many influential theories such as the James-Lange theory of emotion. According to
Hans EysenckHans Jürgen Eysenck was a German-British psychologist who spent most of his career in Britain, best remembered for his work on intelligence and personality, though he worked in a wide range of areas...
, differences in baseline arousal level lead people to be either extraverts or introverts. Later research suggest it is most likely that extroverts and introverts have different
arousability. Their baseline arousal level is the same, but the response to stimulation is different.
The
Yerkes-Dodson LawThe Yerkes–Dodson law is a claimed empirical relationship between arousal and performance, originally developed by psychologists Robert M. Yerkes and John Dillingham Dodson in 1908. The "law" asserts that performance increases with physiological or mental arousal, but only up to a point. When...
states that there is a relationship between arousal and task performance, essentially arguing that there is an optimal level of arousal for performance, and too little or too much arousal can adversely affect task performance. One interpretation of the Yerkes-Dodson Law is the Easterbrook Cue-Utilisation hypothesis. Easterbrook states that an increase of arousal leads to a decrease in number of cues that can be utilised.
In
positive psychologyPositive psychology is a recent branch of psychology whose purpose was summed up in 1998 by Martin Seligman and Mihaly Csikszentmihalyi: "We believe that a psychology of positive human functioning will arise, which achieves a scientific understanding and effective interventions to build thriving in...
, arousal is described as a response to a difficult challenge for which the subject has moderate skills.
Abnormally increased behavioral arousal
This is a state caused by withdrawal from
alcoholIn chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
or barbiturates, acute
encephalitisEncephalitis is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include headache, fever, confusion, drowsiness, and fatigue...
, head trauma resulting in
comaIn medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...
, partial seizures in
epilepsyEpilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
, metabolic disorders of
electrolyteIn chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
imbalance, Intra-cranial space- occupying lesions, Alzheimer's disease, rabies, hemispheric lesions in stroke and multiple sclerosis.
Anatomically this is a disorder of the
limbic systemThe limbic system is a set of brain structures including the hippocampus, amygdala, anterior thalamic nuclei, septum, limbic cortex and fornix, which seemingly support a variety of functions including emotion, behavior, long term memory, and olfaction. The term "limbic" comes from the Latin...
,
hypothalamusThe Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...
, temporal lobes,
amygdalaThe ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...
and frontal lobes. It is not to be confused with
maniaMania, the presence of which is a criterion for certain psychiatric diagnoses, is a state of abnormally elevated or irritable mood, arousal, and/ or energy levels. In a sense, it is the opposite of depression...
.