A2. The Human Brain
The human brain comes develops from the anterior part of the neural tube in an embryo. Most of the neural tube becomes the spinal cord, but the anterior end expands to from the brain in a process called cephalisation (formation of the head).
Discussion Video: Think of ten activities you do on a daily basis. Do they involve language, motor skills, emotions, memory, abstraction? What are the implications for brain involvement?
The structure of the brain
A good view to begin with: The brain becomes more advanced, and complex in capability as you move from the hind brain to the fore-brain. Also the lowerbrain and mid-brain deal with unconscious functions, while the upper brain deals with conscious functions.
The medulla oblongata deals with basic metabolic functions such as the rate of heat beat or breathing (medullary rhythmicity centre). The cerebral cortex, or outer layer of the cerebral hemispheres, allows you to philosophise about the meaning of life (frontal lobes).
Important parts of the brain:
The medulla oblongata - Controls homeostatic functions. contains the medullary rhythmicity centre which controls breathing rate and heart rate. When you exercise, and the hypothalamus detects the lowered pH caused by dissolved CO2 in the blood, it is the medulla oblongata which stimulates an increased heart and breathing rate (see topic 2.8 respiration). The medulla oblongata also deals with reflex digestive functions such as swallowing, or vomiting.
The cerebellum - coordinates balance, posture, muscular coordination. Learning to move your two hands to play the guitar, is possible due to the construction of new circuits in the cerebellum
Hypothalamus and pituitary gland – The endocrine system of glands is controlled by the hypothalamus and the endocrine glands. The hypothalamus monitors the internal environment of the body, and is therefore responsible for homeostatis or maintaining a constant internal environment (see topic 6.6). The hypothalamus also synthesises certain hormones, for the posterior lobe of the pituitary gland which cannot synthesise itś own hormones (eg. ADH) or anti-diuretic hormone)
The pituitary gland has two lobes, the posterior (secretes hormones made in the hypothalamus) and the anterior (synthesises and secretes itś own hormones, such as LH, FSH).
Note the location of the pineal gland (which controls the circadian rhythms through the secretion of melatonin) is evident in this diagram.
The cerebral hemispheres (collectively called the cerebrum) – Collect information from sense organs and other parts of the body, and integrate complex functions such as memory, conscious thought, communication. The most active part of the cerebral hemispheres is called the cerebral cortex and that is the outer layer (2-4mm thick). It is the folding of the cerebral cortext which creates the advanced brain capacity of the dolphin and human brains. The surface area of the cerebral cortex is more indicative of intelligence than brain mass.
The cerebral hemispheres are divided into four lobes, frontal, parietal, occipital (front to back), and temporal (located on the side.
Explore this link on the lobes.
The Nucleus accumbens is a pleasure centre for the brain. This is located in the frontal lobes, at the apex of the each lobe.
The Broca´s area is determines language acquisition. It is part of the frontal lobes.