The brain as a steering center

Hi, my name is Julia Jarosławska and today we are going to learn more facts about the brain as a steering center of our body. Over billions of years, we evolved from single cells organism lacking a nervous system to the complex multicellular organisms we see today. The spongy folded organ enclosed in a skull called brain seems to be the greatest achievement in the human evolution. It defines who we are, what we do, and how we think. It’s us. The brain has many different parts that work together. The biggest part of the brain, accounting for over 80 percent of total brain mass is forebrain. It contains cerebrum and several subcortical structures, including the thalamus and hypothalamus.

The cerebrum consists primarily of grey matter and

is divided into 2 hemispheres: right hemisphere controls and processes signals from the left side of the body, whereas left hemisphere does the same thing for the right side of the body. Not all functions of the hemispheres are shared. In general, the left hemisphere controls speech, understanding, and writing. The right hemisphere controls imagination, spatial ability, musical, and artistic skills. Interestingly, the left hemisphere is dominant in hand use and language in about 90% of people. The cerebrum is the major part of the brain with numerous functions in the body, it is responsible for higher cognition, emotions, personality, vision, speech, hearing, voluntary actions and much more. Beneath the cerebrum is the cerebellum. Its mayor role is the coordination of body movement and posture.

Though small, brainstem, is another and extremely important part of the brain. It governs many basic functions, often operated on an automatic basis, like heart rate, breathing or digestion. Blood vessels that vascularized the brain possess

unique feature: the brain-blood barrier. As it was mentioned before it selectively allows or restricts passage of certain substances between the blood and the brain and protects the brain from circulating harmful viruses, bacteria and toxins. Interestingly, it becomes more permeable during inflammation, allowing certain drugs, phagocytes, as well as pathogens, to move across. Moreover, there are specialized structures in a brain, called circumventricular organs that do not have blood-brain barrier (BBB). These permeable organs enable rapid detection of circulating substances from the bloodstream as well as speeding up secretion of brain-derived signals into the systemic blood. There is the two-way communication between the brain and the endocrine system to regulate the physiological processes of the human body.

Reproduction, metabolism, eating and drinking behavior, blood pressure, osmolality, stress, aggression, and birth, are some of the bodily functions that are triggered or controlled or both by the neuroendocrine systems. Interaction among glands, hormones, and parts of the brain is mediated on the level of specific

axes, for example: The hypothalamus–pituitary–gonadal axis, in other words HPG axis, controls development, aging, and reproduction by regulating the uterine and ovarian cycles in animals. Gonadotropin-releasing hormone (GnRH) is secreted from the hypothalamus. The anterior portion of the pituitary gland produces luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and the gonads produce estrogen and testosterone. The hypothalamus–pituitary–adrenal axis, HPA axis, is in charge of reactions to stress and regulates many body processes, including digestion, the immune system, mood and emotions, sexuality, and energy storage and expenditure. Corticotrophin Releasing Hormone (CRH) released from hypothalamus is a signal to anterior pituitary to release Adrenocorticotropic Hormone (ACTH), and in turn adrenal cortex produce cortisol. The hypothalamus-pituitary-thyroid axis, HPT axis, is responsible for the regulation of metabolism.

Hypothalamus release thyrotropin-releasing hormone (TRH) and the TRH stimulates the anterior pituitary to produce thyroid-stimulating hormone (TSH). The thyroid-stimulating hormone, in turn, stimulates the thyroid to produce thyroid hormone. The gut-brain axis drives signals between the Gastrointestinal (GI) system and the brain. Brain can influence gut motility, secretion of gut hormones and microbial balance. On the other hand, gut bacteria produce various chemicals, for example neurotransmitters or short chain fatty acids that may affect brain function and modulate mood and behavior. The brain is the master control center for all functions in the body, it is continually processing information so you can think, move, eat, sleep, live a fruitful and creative life.

The brain is an extremely active organ and as you will see in the next lectures and organ with high demands. Thus, to keep your grey matter healthy and productive, eat nutrients dense food and try to keep active, both your body and mind.