Motivation and emotion/Book/2016/Norepinephrine and emotion

Overview
Neurotransmitters play an important part in our complex brain biology. Chemicals released in the brain such as serotonin, dopamine and norepinephrine all help with certain functions in which our body requires. The analysis of the brain structure in the second millennia, and then the start of cellular and molecular analysis in the 20th century all have been on a basic level, in which science has only started to understand and explain neuroanatomy. In the 21st century scientific advancements have looked into the link between neural communication and emotions. This book chapter consequently explores what the neurotransmitter norepinephrine is along with emotions and the relationship between the two.

Definitions
This section will highlight some key defintions relevant to the chapter.

Neurotransmitters
A neurotransmitter is a chemical messenger that allows neurons to communicate (Melasch et al., 2016). For instance, they relay information to tell your heart to beat, your lungs to breathe and allow your body to regulate chemicals. Neurotransmitters are released at the end of a nerve fiber via the arrival of a nerve impulse, they then cross the synapse, this effects the next nerve fiber (Harmer, Hill, Taylor, Cowen, & Goodwin, 2003) (See Figure 1)



Norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin is in the family of catecholamines (working as both a neurotransmitter and hormone) which tracts in the central nervous system (Salgado, Treviño, & Atzori, 2016). It is also a neurohormone stored in the chromaffin granules of the adrenal medulla and is released in response to sympathetic stimulation in the sympathetic nervous system (SNS) (Pascucci, Ventura, Latagliata, Cabib, & Puglisi-Allegra, 2007).

In the brain, norepinephrine is produced in closely packed brain cell neurons or nuclei that are small yet have powerful effects on other brain areas. The most important of these nuclei is the locus coeruleus, located in the pons (Levenson, 2014). In the sympathetic nervous system, norepinephrine is used as a neurotransmitter by sympathetic ganglia located near the spinal cord, and it is released directly into the bloodstream by the adrenal glands. Norepinephrine acts on target cells by binding to and activating noradrenergic receptors located on the cell surface (Lovatt, 2011). Norepinephrine's main roles include assisting in the brain processes responsible for fast memory, quick reaction time, mental energy, alertness and attention, goal seeking and sexual behaviour (Gu, Wang, Wang, & Huang, 2016).



Some symptoms associated with normal and excess levels of Norepinephrine

 * Increased heart rate
 * Sympathetic nervous system stimulation
 * Vasoconstriction
 * Smooth muscle relaxation
 * Liver glucose release
 * Increased blood pressure
 * Dilation of air passages in the lungs and narrowing of blood vessels in non-essential organs
 * Anxiety
 * Hostility
 * Excessive vigilance

Emotions
In everyday speech, emotion is termed as the conscious experience described by intense mental activity. In psychology, emotion is termed as the complex state of feelings both physical and psychological. Emotion is influenced by physiological arousal, expressive behaviours, and conscious experience (Lee, 2011; Ramirez & Cabanac, 2003). The reflective emphasis on the “feeling” aspect of emotions had a prominent role in the development of theories of emotion. Darwin argued as early as 1872 that both observable expressions of emotions as well as underlying brain processes are not unique to humans (Koob, 2015).

It is important to understand the neuroscience behind emotion and the cognitive function of emotion. We interpret our immediate emotional experience in the context of our past experiences, which provides the framework that allows us to label our feelings. (Lee, 2011). Six emotions were proposed based on extensive cross-cultural work on facial expressions these are:
 * 1) happiness
 * 2) surprise
 * 3) fear
 * 4) sadness
 * 5) anger
 * 6) disgust combined with contempt (Ekman & Friesen, 1986)



Neurotransmitters and Emotions
The neural circuits involved in emotions are modulated by numerous chemical neurotransmitters. A balance of neurotransmitters is necessary for normal emotional states and arousal (Gerra et al., 1998). Neurotransmitter levels can be high, low or unevenly balanced. With excessively low levels moods may be flat, with emotion ranging from sadness and numbness. When levels are high, mood levels are erratic and unpredictable (Dremencov, el Mansari, & Blier, 2009). Aspects of personality can be affected by three major neurotransmitters dopamine, serotonin and norepinephrine. Neurotransmitter balance is influenced by nutrition, environmental, genetic and external emotional stimulus. Locus coeruleus cell bodies contain norepinephrine and innervate all areas of cortex, cerebellum and spinal cord (Flik, Folgering, Cremers, Westerink, & Dremencov, 2015; Lovatt, 2011).



Norepinephrine and emotions
Emotion boosts our ability to form vivid memories,{{g]] norepinephrine released during emotional arousal, plays a central part in providing a molecular mechanism for how emotion enhances learning and memory (Hu et al., 2007). Norepinephrine alters emotions and is critical in enhancing emotional content. (Harrison, Morgan, & Critchley, 2010; Pringle, McCabe, Cowen, & Harmer, 2013; Segal, Stark, Kattan, Stark, & Yassa, 2012) Emotionally poignant experiences release adrenaline and encourages the release of norepinephrine (Nicholson, Bryant, & Felmingham, 2014). Norepinephrine is also released when emotions are artificaly induced by manually stimulating the brain (Panksepp & Watt, 2011).

Conclusion
In conclusion, norepinephrine which arises from the locus coeruleus is released, the amount of the neurotransmitter released will dictate emotions ranging from the normal levels of emotion to the critical levels which then affects emotions to become unpredictable, such as depression. Norepinephrine also plays a major part in relation to adrenaline which helps when dealing with flight or flight.

Quiz
{Norepinephrine (NE) projections arise from the locus coeruleus and reach all cortical areas. + True - False
 * type=""}

{Arousal is one of the functions of Norepinephrine? + True - False
 * type=""}

{The locus coeruleus is located in the hippocampus - True + False
 * type=""}

{There are 7 different types of emotions - True + False
 * type=""}

{Emotional current experience can be interpreted by past experience + True - False
 * type=""}