The brain is the central information-processing organ of the body. It innervates the head through cranial nerves, and it communicates with the spinal cord, which innervates the body through spinal nerves. Nervous fibers transmitting signals from the brain are called efferent fibers. The fibers transmitting signals to the brain are called afferent fibers (or sensory fibers). Nerves can be afferent, efferent or mixed (i.e., containing both types of fibers).

The brain is the site of reason and intelligence, which include such components as cognition, perception, attention, memory and emotion. The brain is also responsible for control of posture and movements. It makes possible cognitive, motor and other forms of learning. The brain can perform a variety of functions automatically, without the need for conscious awareness, such as coordination of sensory systems (eg. sensory gating and multisensory integration), walking, and homeostatic body functions such as blood pressure, fluid balance, and body temperature.

The Cerebellum controls balance and movement. Without it, movements would not be coordinated.
Diagram showing the lobes of the human cerebral cortex and the cerebellum.
Diagram showing the lobes of the human cerebral cortex and the cerebellum.

Many functions are controlled by coordinated activity of the brain and spinal cord. Moreover, some behaviours such as simple reflexes and basic locomotion, can be executed under spinal cord control alone.

The brain undergoes transitions from wakefulness to sleep (and subtypes of these states). These state transitions are crucially important for proper brain functioning. (For example, it is believed that sleep is important for knowledge consolidation, as the neurons appear to organize the day's stimuli during deep sleep by randomly firing off the most recently used neuron pathways; additionally, without sleep, normal subjects are observed to develop symptoms resembling mental illness, even auditory hallucinations). Every brain state is associated with characteristic brain waves.

Neurons are electrically active brain cells that process information, whereas Glial cells perform supporting function. In addition to being electrically active, neurons constantly synthesize neurotransmitters. Neurons modify their properties (guided by gene expression) under the influence of their input signals. This plasticity underlies learning and adaptation. It is notable that some unused neuron pathways (constructions which have become physically isolated from other cells) may continue to exist long after the memory is absent from consciousness, possibly developing the subconscious.

The study of the brain is known as neuroscience, a field of biology aimed at understanding the functions of the brain at every level, from the molecular up to the psychological. There is also a branch of psychology that deals with the anatomy and physiology of the brain, known as biological psychology. This field of study focuses on each individual part of the brain and how it affects behavior.

Exercise benefits

Exercise benefits

Physical exercise is important for maintaining physical fitness and can contribute positively to maintaining a healthy weight; building and maintaining healthy bone density, muscle strength, and joint mobility; promoting physiological well-being; reducing surgical risks; and strengthening the immune system.

Frequent and regular aerobic exercise has been shown to help prevent or treat serious and life-threatening chronic conditions such as high blood pressure, obesity, heart disease, Type 2 diabetes, insomnia, and depression. Strength training appears to have continuous energy-burning effects that persist for about 24 hours after the training, though they do not offer the same cardiovascular benefits of aerobic exercises. Exercise can also increase energy and raise one's threshold for pain.[citation needed]

There is conflicting evidence as to whether vigorous exercise (more than 70% of VO2 Max) is more or less beneficial than moderate exercise (40 to 70% of VO2 Max). Some studies have shown that vigorous exercise executed by healthy individuals can effectively increase opioid peptides (aka endorphins, a naturally occurring opiate that in conjunction with other neurotransmitters is responsible for exercise induced euphoria and has been shown to be addictive), positively influence hormone production (i.e., increase testosterone and growth hormone), benefits that are not as fully realized with moderate exercise.

Exercise has been shown to improve cognitive functioning via improvement of hippocampus-dependent spatial learning, and enhancement of synaptic plasticity and neurogenesis. In addition, physical activity has been shown to be neuroprotective in many neurodegenerative and neuromuscular diseases. For instance, it reduces the risk of developing dementia. Physical activity is thought to have other beneficial effects related to cognition as it increases levels of nerve growth factors, which support the survival and growth of a number of neuronal cells.

Both aerobic and anaerobic exercise also work to increase the mechanical efficiency of the heart by increasing cardiac volume (aerobic exercise), or myocardial thickness (strength training, see Organ hypertrophy).

Not everyone benefits equally from exercise. There is tremendous variation in individual response to training: where most people will see a moderate increase in endurance from aerobic exercise, some individuals will as much as double their oxygen uptake, while others will never get any benefit at all from the exercise. Similarly, only a minority of people will show significant muscle growth after prolonged weight training, while a larger fraction experience improvements in strength. This genetic variation in improvement from training is one of the key physiological differences between elite athletes and the larger population. Studies have shown that exercising in middle age leads to better physical ability later in life.

Diet

Traditional diets

The traditional diets of populations around the world vary greatly. The diet of Inuit hunters in the Arctic is composed almost entirely of meat and fish, but most hunter-gatherers in other parts of the world obtain more food from gathering plants than from hunting animals. Pastoralists keep different animals according to where they live, varying from reindeer in the north to camels in hot arid areas, but they always have a diet rich in animal foods such as milk, meat, and blood. Peasant agriculturalists grow different staple crops according to local conditions, but usually have diets composed largely of plant foods with only small amounts of animal foods.

The traditional diets of populations have been followed for hundreds or thousands of years and, except in times of severe food shortage, are certainly compatible with the maintenance of health sufficient for the survival and growth of infants and children, and for successful reproduction. However, traditional diets are sometimes far from optimal and may be accompanied by serious nutritional disorders, from which the people may have suffered for many generations. For example, approximately one-fifth of the population of the world is at significant risk for developing iodine deficiency disorders; pellagra was formerly common in populations subsisting largely on maize due to deficiency in the vitamin niacin and the amino acid tryptophan; and high blood pressure and stroke are common in populations with a diet high in salt.

Diets for health

Diets for health

Within Western populations, the word ‘diet’ is commonly used to refer to patterns of food consumption which are followed for reasons of health or for ethical or religious reasons (vegetarian andvegan diets are discussed in separate entries). A good diet is of profound importance for the maintenance of good health; nutritional deficiencies severe enough to cause obvious diseases such as scurvy and pellagra are now very rare in Western societies, but diet is a major determinant of the risk for developing many of the commonest fatal diseases, including ischaemic heart disease, stroke, and cancers of the large bowel and stomach.

The commonest type of diet followed for health reasons is one intended to cause weight loss in the treatment of overweight, and the term dieting is often assumed to refer to a weight-reduction diet. Numerous types of weight-reducing diets have been marketed. Most will cause some initial weight loss, but this is difficult to maintain because obesity is associated with the typical Western lifestyle of low physical activity and constant availability of highly palatable, energy-dense foods.

After obesity, the most common reason for requiring dietary changes is a high blood cholesterol concentration and associated ischaemic heart disease. The blood cholesterol concentration is increased by diets high in saturated fat and cholesterol. Reducing the intake of these factors causes a reduction in blood cholesterol, but most individuals find it difficult to change their diet sufficiently to have more than a small effect. Other diets followed for health reasons include low salt diets for the reduction of raised blood pressure and gluten-free diets for individuals with coeliac disease.

Western diets

The diets of affluent Western populations changed very rapidly during the twentieth century. In comparison with the diets of peasant agriculturalists, Western diets are usually much higher in animal protein and fat and much lower in starch and dietary fibre, and ample food is available throughout the year. It is well known that Westernization of the diet is usually associated with increases in the rates of some diseases, such as ischaemic heart disease, large bowel cancer, and obesity, but it should also be appreciated that Westernization is generally accompanied by an increase in overall life expectancy and by decreases in the rates of some diet-related diseases such as stomach cancer, as well as decreases in the incidence of most infectious diseases.

what is the Vegetarianism

Vegetarianism is the practice of a diet that excludes all animal flesh, including poultry, game, fish, shellfish or crustacea, and slaughter by-products. The reasons for choosing vegetarianism may be related to morality, religion, culture, ethics, aesthetics, environment, society, economy, politics, taste, or health.

There are several variants of the diet, some of which also exclude eggs and or some products produced from animal labor such as dairy products and honey. Veganism, for example, excludes all animal products from diet. By some strict definitions, animal products are not used for attire either, whether or not the production of clothing or items has involved the actual death of an animal, dairy, eggs, honey, wool, silk, down feathers, etc. A generic term for both vegetarianism and veganism, as well as for similar diets, is Plant-based diets.

Vegetarian diets have been found to satisfy the nutritional needs for all stages of life, and large-scale studies have shown vegetarianism to increase longevity, improve health, and significantly lower risks of cancer and other diseases.