The Human Brain Research from www.AnatomyHQ.org
The Human Brain The Human brain is the most elaborate formation in the known universe. It is in control of a huge number of bodily functions; processing sensory information; regulating biochemical processes; coordinating movement and of course, providing us the ability of higher thought/perception. There are three primary areas of the human brain: • The rhombencephalon • The mesencephalon • The forebrain
Hindbrain The rhomencephalon includes the brain stem and cerebellum and controls a a great variety of processes. It is found in the cranial cavity. One essential mass of tissue that composes the hindbrain is the medulla oblongata. The medulla oblongata is connected to the spinal cord and is so vital to life that diseases effecting it are often fatal. An additional structure is the cerebellum. This section is sometimes called the “little brain”. It looks different to the rest of the brain. It has a surface of densely folded gray matter. It is mainly involved with movement.
Hindbrain The Pons measures approximately 2cm in length and lies next to the Mid-brain and the medulla. It is made up of nuclei that are involved with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.
Midbrain The Midbrain/Mesencephalon is above the Pons and below the cerebral cortex. The dorsal structure of the midbrain is called the tectum, it is involved in reflexes in relation to hearing and sight (e.g. the eye movement, pupil size, lens shape). The anterior region of the midbrain is called the tegmentum, it is in essence a complex network of neurones in charge of unconscious homeostatic and reflexive pathways.
Forebrain The Forebrain is above both the hindbrain and the midbrain as well as being the most anterior. It has essential roles in the following processes: Mastication Directs sensory impulses through the body Equilibrium Vision Eye movement Facial sensation Hearing Phonation Intelligence Memory Personality Respiration Salivation Swallowing Smell Taste
Forebrain The Forebrain is divided into two important structures: Telencephalon (cerebral cortex) The cerebral cortex is the folded outer structure of the brain, in humans it is between 2-4mm thick. It has the highest levels of non- insulated grey matter of any region of the brain. The cortex forms folded bulges (thus significantly increasing the part without increasing the volume) called gyri; so much so that more than 2/3 of the brain lie in these folds (known as sucli). The Frontal lobe is a division of the cortex and is the most anterior region of the lobes and is additionally superior to the temporal lobe. This portion of the brain is related with some of of the the most vital traits associated with personality (e.g ability to know future results of things), learning, impulse control, and prioritising actions. It is host to most of the brain’s dopamine receptors (these are the key feedback through which learning is developed).
Temporal lobes The temporal lobes are behind the frontal and parietal lobe and anterior to the occipital lobe. Studies suggest they are the crucial portion of the brain involved in declarative memory; damage to the temporal lobes can result in an inability to form memory after the event (anterograde amnesia). They contain the hippocampus (long-term memory) and are involved in hearing and higher visual perception (e.g. facial recognition).
Parietal lobe The parietal lobe is anterior of the occipital lobe, behind the frontal lobe and caudal of the temporal lobes. The border between the frontal lobe and the parietal lobe is marked by the central sulcus. The border between the occipital lobe and the parietal lobe is marked by the parieto-occipitosulcus and the border between the temporal lobe and the parietal lobe is marked by the lateral sulcus. The parietal lobe coordinates information from multiple senses in order to establish spatial orientation.
Occipital lbe The Occipital lobe is the most posterior of all the main lobes of the brain. Anatomically this portion contains most of the visual cortex (Brodmann area 17) and damage to the occipital lobes results in significant homonomous vision loss (i.e. the effect is the same in both eyes). The occipital lobes are where shape, colour, and like the temporal lobes, facial recognition take place. Projections from the occipital lobe to the superior temporal-parietal structure are fundamental for perceiving motion of objects.
Basal Ganglia The basal ganglia are a portion of the corpus striatum and are in essentially a set of interconnected nuclei within the brain. Nervous impulses from the cerebral cortex passes to the basal ganglia where it is processed and then relayed back via the thalamus. There are a plethora of connections and pathways within and although the basal ganglia have long been known to be involved in movement; it is known this is not there sole actions, though the exact process in relation to behaviour control have yet to be properly established. Evidence suggests that during learning, basal ganglia and medial temporal lobe memory systems are activated simultaneously and that in some learning situations competitive interference exists between these two systems. One theory suggests the basal ganglia decides which out of a number of possible actions the cortex may be planning, actually gets executed. Fitting this with idea that dopamine is used as a reward system for learning.