Sleep and Sex: Basic Needs - Assignment Example

Lecture 5: Sleep and Sex – Basic Needs Some of the most basic needs of the human body are sleep and sex. Sleep is a in which the brain and the body have a chance to recuperate and restore themselves, while sex is necessary for the propagation of one’s specific genetic material and of the species in general. Thus, it is important to look into the mechanisms by which these basic needs are satisfied by the human organism. A Physiological and Behavioral Description of Sleep Sleep involves a change in physical behaviour as well as the person’s state of consciousness. When a person falls asleep, they go through a number of stages of sleep that follow each other in a specific order. Each stage is characterized by the behavior of the person and the EEG activity observed in brain functioning. When the person is awake, the brain exhibits alpha and beta activities. Alpha activity is resting activity characterized by 8-12 Hz and beta activity involves alert wakefulness characterized by 13-30 Hz. Initially, the person enters stage one of sleep, they exhibit alpha and theta activity (3.5-7.5 Hz). At this point the person drifts between sleep and wakefulness till they enter the second stage when they are fully asleep. At the second stage, the brain exhibits sleep spindles and K complexes. Sleep spindles are observed through all sleep cycles, and are bursts of activity that seem to be intended to keep a person asleep, while K complexes tend to lead into the third stage where delta activity is observed. Delta activity is very low level brain activity (less than 3.5 Hz) and makes up for 20-50% of stage 3 sleep which slowly blends into stage four sleep where delta activity is observed as making up over 50% of the sleep time. Stage 3 and 4 seem to be more important as compared to stage 1 and 2; particularly as sleep deprived persons are more likely to make up these states. About 90 minutes into entering sleep, an individual experiences REM sleep which is characterized by beta and theta brain activity. REM sleep is also when people dream and can be associated with muscle paralysis and genital activity. These cycles seem to repeat themselves at 90 minute intervals, and there are suggestions that people experience similar cycles even when awake. People woken during REM sleep are alert, while those woken during non REM sleep are usually groggy. Disorders of Sleep Sleep related disorders can cause significant distress to the person since they interfere with getting adequate and restful sleep. The most well known of sleep disorders is insomnia; characterized by an inability to sleep. A diagnosis of insomnia needs to be made with reference to the sleep needs of the patient. In essence, insomnia is a symptom of an underlying problem – either physical or psychological. The most effective treatment of the condition, thus, is to address the underlying problem. Although some patients ask to be provided with medication that can help them sleep, they are likely to develop a tolerance for the drug, and thus will require larger doses. Insomnia is closely related to sleep apnea – a condition in which the person cannot sleep and breathe at the same time. Thus, every time the individual falls asleep, they experience lack of air and return to waking state. Sleep apnea usually has a physical cause, and can be corrected with devices that help support the relevant muscles and keep the air passage clear. Narcolepsy is another sleep disorder, and is often called a sleep attack. An individual experiencing a narcoleptic attack may feel a sudden and overwhelming need to sleep and will fall asleep for 2-5 minutes. People who experience a narcoleptic episode often wake refreshed. A similar condition is called cataplexy, in which an individual experience the muscle paralysis associated with REM sleep while being fully awake. Sleep paralysis refers to an event when such muscle paralysis occurs just before or after the person experiences normal sleep. If the person also experiences dreams during this time, it is called hypnagogic hallucinations. Most of these conditions are associated with disruptions in normal brain activity and a neurotransmitter called hypocretin has been implicated. Medicines can successfully help with these conditions. REM sleep behavior disorder is the opposite of these conditions, where muscle paralysis does not occur during REM sleep. Thus, the person acts out their dreams. This condition is also treatable, and responds successfully to medication. Why do we sleep? Sleep seems important to all higher organisms. It was previously believe that sleep was time for the body to rest and recuperate, yet, there seems to be little evidence to suggest that sleep differs from any other kind of wakeful rest for the body. On the other hand, sleep seems to be very essential for the mind to function consistently. Sleep deprivation has very little effect of exercise of other bodily functioning. On the other hand, it has significant effect of brain functioning. Sleep deprived individuals seem to have trouble with cognitive tasks, with memory and concentration and are even known to experience hallucinations. Conversely, periods of physical exercise do not cause deeper sleep, but periods of mental exercise are associated with more and deeper sleep. Deep slow-wave sleep (stage 3 and 4) seem to be the most important for cerebral recuperation. Areas that are most active during a waking period show the most delta waves during sleep, demonstrating that periods of high activity for any part of the brain cause the need for rest for that particular part. The delta waves seem to reduce the brain’s metabolism and thus, allow it to rest. On the other hand, REM sleep seems to help in improved learning and memory. The similarity between activation of the brain during REM sleep and learning periods during a wakeful period leads to the assumption that REM sleep allows an individual to rehearse events mentally or explore new ideas. This has not yet been conclusively proven, but it is believed that an improved understanding of dreams and REM sleep in general will help in understanding this mechanism. Physiological Mechanisms of Sleep and Waking There seems to be evidence that sleep inducing agents are produced in the brain during periods of wakefulness, and vice-versa. Adenosine is released in the brain when glycogen reserves are used, and this may cause the need to sleep (so that glycogen may be replenished). A number of brain areas are associated with the state of consciousness – the acetylcholinergic area, the pons, the basal forebrain, the noradrenergic system, the serotonergic system, the histaminergic neurons and the lateral hypothalamus are all implicated in producing a need to sleep when required and a state of alert wakefulness at other times. Given the number of neurotransmitters that are implicated, it is evident that sleep is important for normal functioning of different parts of the brain. Neurons of the VLPA, when activated, cause an inhibition of these systems. On the other hand, when these systems start to become active again, they inhibit the VLPA neurons. REM sleep is associated with the activation of acetylcholinergic neurons. These neurons cause cortical arousal via the thalamus and basal forebrain. Similar neurons in the lateral preoptic area and the subcoerulear nucleus are responsible for penile erection and muscle paralysis that is seen during REM sleep. There is a distinct link in the levels of activity of the different systems implicated in different periods of sleep; but the exact mechanism by which they activate and inhibit each other is unknown. Biological clocks Although the sleep wake cycle id the most understood of all the internal cycles, there are other corresponding cycles that regulate body temperature, secretion of hormones and other associates cycles. While most of these are roughly a day long, others may be shorter or longer. All these biological clocks are associated with the suprachiasmatic nuclei in the hypothalamus. Thus, any disruption in the working of the hypothalamus is likely to affect one of more of these biological clocks. Circadian rhythms are cycles that are approximately a day long. These rhythms seem to be approximately 25 hours long, but the presence of sunlight seems to reset them each day. The responsibility of running these clocks seems to belong to individual neurons that show synchronized firing patterns. Melatonin that is secreted by the pineal gland also seems to affect circadian rhythms. Sexual Development Humans, among other higher animals develop into one of two genders. The female is the child bearing sex and is equipped for carrying a child to term internally while the male is developed to provide sperm leading to procreation. The default structure of the human body is that of the female, possibly since a larger number of females are more beneficial for the promotion of the species. Yet there are distinct differences between the sexes that develop as a result of the activation of different hormones in males and females. A female carries the XX pairing of the sex chromosome, and is formed when the father supplies the sperm with the X chromosome. When the sperm carries the Y sex chromosome, it produces a XY pairing that produces a boy. The Sry gene on the Y chromosome is responsible for the successful development of masculinity in a male child. This gene is responsible for the development of the testes from the basic gonads in a male, which in turn produce hormones that determine the secondary sexual traits in men. The two main hormones produced by the testes are testosterone – which leads to development of the Wolffian system and thus leads to the development of secondary sex characteristics. The second is the anti-Mullerian hormone that suppresses the development of the female secondary sex characteristics. In the absence of these hormones, the body takes on female secondary sex characteristics regardless of the presence or absence of the second X / Y chromosome. As a child grows and reaches puberty, the hypothalamus begins secreting gonadotropin – releasing hormone which causes the pituitary gland to release follicle releasing hormone and luteinizing hormone; which in turn activates the gonads. In the case of males, testosterone and anti-Mullerian hormone are released, while in the case of females, estrogen and progesterone are released. These hormones then cause the development of the genitals and the secondary sex characteristics. Hormonal Control of Sexual Behavior  Different hormones control the sexual behavior of males and females. In females, the secretion of FSH by the pituitary gland leads to the maturation of ovarian follicles which in turn leads to the secretion of estradiol. When the estradiol reaches a particular level, it causes the pituitary gland to release LH, leading to ovulation. The follicle now produces estradiol and progesterone. Estradiol is responsible for the development and maintenance of the uterine lining. If there is no pregnancy, the follicle stops producing hormones and dies, leading to menstruation once the hormones are reduced in the body. This process is a norm in mammals, and female sexual attraction is not associated with the presence of hormones. On the other hand, male sexual behavior is associated with the presence of andrognising hormones. It is also theorized that homosexuality may be associated with exposure to sex hormones at the pre-natal stage. Pheromones are like a non conscious messaging system that uses scent as a messaging mechanism. Odorants are produced by the male and female bodies to demonstrate receptivity to sexual advances and to demonstrate sexual health. Although these are not consciously recognized, pheromones are associated with a variety of sexual behavior. Although the use of pheromones is well established in lower animals, there is inconclusive evidence about the use of pheromones in humans. It may be that multiple factors affect human choices to copulate; and thus, the role of pheromones is subverted. Neural Control of Sexual Behavior While hormones are an important determinant of sexual behavior, there are structures in the brain that influence sexual behavior and interest. Different parts of the brain are associated with the sexual behaviors of males and females. Male sexual behavior seems to be controlled by the stimulation of the medial preoptic area of the forebrain while the stimulation of the ventromedial nucleus in the hypothalamus controls female sexual behavior. If these areas are destroyed or damaged, the individual loses interest in copulation. These areas seem to be sensitive to the sex hormones of the relevant sex – testosterone in men and progesterone and estrogen in women. Receptors for these hormones exist, which, when activated, cause the desire to have sex and lead to behavioral choices that would lead to sexual activity. Parental Behavior For mammals like humans, the majority of parental burden falls of females, and thus, parental behavior is most obvious in them. The medial preoptic area of the forebrain is significantly implicated in parental behavior in females, followed by parts of the midbrain. These brain parts are connected, and this connection seems to cause maternal behavior, as its destruction causes maternal behavior to cease. Hormones like progesterone (during pregnancy) and prolactin (during lactation) causes the maintenance of maternal behavior. Paternal behavior, on the other hand, is relatively less observed in mammals, although changes in the MVA do influence behavior. Lesions to this area reduce paternal behavior, while injecting estradiol into it enhances care giving. Read More