Free Regulatory Behavior Essay Example

The nervous system is one of the most important systems of the human body whose major function is to control the internal constancy of the internal environment of the body through the process of homeostasis. The nervous system provides direct control of the muscles and glands by the somatic and autonomic motor systems. While the somatic system controls the muscles of respiration, the autonomic nervous system controls the smooth muscle, cardiac muscle, exocrine glands and adrenal medulla . The nervous system also provides appropriate outputs via the somatic motor system, which lead to behavioral responses, such as feeding, drinking and thermoregulatory behaviors. The coordination of muscles is possible with the help of the nervous system. It also regulates cognitive thinking by processing information collected from various sensory organs. The hypothalamus and the associated systems are important brain areas for the control of the homeostatic mechanisms and their behavioral components.
The hypothalamus plays a major role in the nervous system by processing the neural signals transmitted by the neurons at synapses. It exerts its influence in three major ways; through the endocrine system by its neurosecretory functions, through the autonomic nervous system over which it has control and through other parts of the nervous system, especially the limbic system by controlling motivation . The neurons play an equally important role in the human nervous system. Although no two neurons look alike, they have four basic parts, namely dendrites, soma, axon and axon terminals. The dendrites look like tree roots and receive messages from other neurons. The soma in addition to receiving messages from other neurons also sends nerve impulses down a thin fiber called axon. The axon terminals are the ends of the axon fibers where the axon comes in contact with the other neurons.
The regulatory behaviors of sleeping and waking are the most essential behaviors of the human body, which are entirely different to each other. It is only in the awake state that the humans respond appropriately to the external environment. The sleep-wake cycle is a circadian rhythm driven by the day-night cycle. The two states of sleep are slow-wave sleep and REM sleep . Within the sleeping state, two major stages are recognizable. In one phase, the muscles relax and yet major postural adjustments take place. In the other phase, most of the musculature is in a more relaxed state although the eyes make rapid movements, but arousal is more difficult to evoke when compared to the other phase. During the walking, the electrical activity of the brain possesses certain characteristics, such as fast activity and low voltage. Most of the individual neurons in the forebrain fire at relatively faster rates.
The nuclear groups and fiber connections of the brain stem reticular formation are of central importance in the initiation and regulation of sleeping and waking. With the transition to sleeping, the electrical activity becomes dominant by high-voltage and slow-wave activity. Moreover, the neurons in the forebrain decrease their firing rates. During the behavioral state of waking; there are two major components of motivational activity, namely, non-specific activation and motivational behavior . Non-specific action includes phenomena, such as arousal and drive, whereas motivational behavior directs the human activities towards particular goals, such as eating, drinking, mating and many others. During the REM sleep state, there is cortical arousal even though there is no motivational behavior. Also, the sleeping time influences mortality and morbidity. It facilitates the neuronal function of the brain and affects the mental performance of the humans.
Fear, anxiety and aggression play a vital role on the sleeping behavior. Mental, physical or emotional arousing activities taking place before the expected sleeping time lengthen the process of falling asleep. The primary changes in the sleep-wake cycle include the flattening of the current depth of sleep and wake, fragmented sleep, changes in the distributions of sleep phases, increased latency periods, shortening of the overall duration of sleep, increased duration of periods of high muscular tension, and changes in breathing rate, hormone secretion and peripheral circulation . The secondary reactions due to fear and anxiety include the impairment of physical and mental condition, experience of sleep, well-being, performance and concentration. Other effects are fatigue, restlessness, poor concentration, irritability and many others. Nightmares are also common complaints as a result of fear, anxiety and aggression. Individuals usually wake up abruptly from sleep with physical symptoms similar to panic attacks. They may have a fear of going to bed and eventually develop insomnia.
Sleep-related distress and sleep dissatisfaction cause difficulties falling asleep, difficulties staying asleep and early awakening. Fear and anxiety also cause reactivity and arousal during sleep. They fail to maintain a homeostatic balance between wakefulness and sleep. The sleep-promoting and wake-promoting neurons fail to protect and tailor the length and depth of sleep under stress and anxiety . Brief awakenings from sleep as a result of fear not only cause disruption to the sleep process, but also affect the underlying mechanisms of sleep control. In addition to affecting the health of the humans, sleep deprivation due to anxiety also hampers the social, occupational and other important areas of functioning, such as circadian rhythm. In severe cases, fear and anxiety also lead to the dysregulation of synaptic homeostasis.
Hormones are important in regulating the sleep behavior in human beings. Mutual interactions between the neurohormones and the circadian system affect the sleeping behavior of individuals. Hormonal release affects sleep and hence of functional significance to the maintenance and quality of sleep. The levels of hormones fluctuate across day and night, which not only attribute to the changes in sleep and wakefulness, but also other behaviors of the human body . Sleep either influences the hormonal secretion independent of the circadian timing or closely couples the light-dark cycle. Sleep has a strong effect on the levels of various hormones as it affects the circulating hormonal levels. On the other hand, the circadian rhythm influences the secretion of hormones, which in turn plays a major role in the sleep mechanism.
Melatonin, a hormone secreted in the pineal gland of the brain plays a major role in the regulation of the quality of sleep and the circadian rhythm. It is melatonin, which diminishes the sleep period on exposure to bright light. The nighttime rise in melatonin causes maximal fatigue, minimal degree of alertness, and affects the physical and mental performance of individuals . Leptin, the hormone which regulates the appetite regulation also influences the sleep. Another hormone called orexin, also known as hypocretin exhibit the physiological effects of sleep. Steroidal hormones serve as a signal linking metabolic status with endocrine control of sleep, arousal and reproductive processes. Growth hormone-releasing hormone also influences the sleeping mechanism. On the contrary, sleep deprivation affects the growth hormone, especially in the case of children.
The sleep and wake cycle also involves various other hormones, such as progesterone and prolactin. Thyrotropin-related hormones influence the sleep-supressive activity. Glutathione induces natural sleep by inhibiting excitory synaptic neurotransmission of glutamatergic neurons and serve as a neuronal detoxification factor. Other hormone, such as insulin, which regulates the water balance in the human body, undergoes consistent variations during sleep and wakefulness . People who have higher daytime body temperatures sleep longer than usual as the correlation between basal metabolic rate and sleep length is high. Extremely cold temperatures increase the awake time during sleep and alter the structure of sleep. Changes in weather also affect the sleeping behavior. Severe changes in the sleep/wake cycle cause dizziness, tinnitus, gastrointestinal problems, weight gain and increased intraocular pressure .
The impairment of the hypocretin hormone results in sleep disorders similar to narcolepsy. It exerts a transient increase in sleep shortly after feeding. It influences the inhibitory action on brain maturation through a suppression of active sleep. The impairment of pituitary hormones causes modulations to sleep and wakefulness. Lack of appetite affects the quality of sleep. Any impairment of the sleep/wake facilitating mechanism or the sleep/wake inducing mechanism or the sleep/wake maintenance mechanism affects the duration of the sleep . The impairment of the neurotransmitters affects the wakefulness circuits. Neuropsychological tests determine the type and extent of cognitive and mental impairment caused by the damage of the neurotransmitters. In some cases, the impairment of the sleep-related areas of the nervous system also leads to motor and memory impairment.

References

Brown, A. (2001). Nerve Cells and Nervous Systems: An Introduction to Neuroscience. Springer Science & Business Media.
Siegel, J. H. (2002). The Neural Control of Sleep and Waking. Springer Science & Business Media.