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Transcript of The Brain
The Brain Stem
The Reticular Formation is a nerve network that travels through the brainstem and acts as a filter for stimulus coming from the outside world. It tells you whether or nor you should be awake, asleep, paying attention, etc. If the Reticular Formation is severed, the resulting condition is coma.
The medulla connects the higher levels of the brain to the spinal cord, and is responsible for several functions of the autonomic nervous system. These functions include the control of blood pressure, heart rate, and breathing. The medulla is located above the spinal cord and is also known as the medulla oblongata.
Located below the occipital lobes, this "mini brain" coordinates voluntary movement. In the absence or malfunction of the cerebellum, movement would be jerky. In addition, the cerebellum allows you to judge time and sounds/textures.
The thalamus is located on top of the brain stem and acts as a sensory switchboard for the brain. It directs messages to sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla. The thalamus receives all senses except for smell.
Lying below the thalamus, the hypothalamus directs several metabolic activities like eating, drinking, and body temperature. It also governs the endocrine system through control of the pituitary gland, and is the link to emotion and reward. If one considers themselves a morning or night person, the hypothalamus may be the cause as it controls biological rythyms.
The Amygdala is composed of two lima bean sized neural clusters that are linked to emotion. It regulates aggression and fear in addition to integrating hearing and sight into emotion. It is because of the Amygdala that one sees a rope as a snake and gets frightened.
The pituitary gland lies in a small pocket of bone called the sella turcica and is connected to the hypothalamus by the pituitary stalk. It is known as the master endocrine gland as it controls other endocrine glands in the body. The pituitary secretes hormones that control sexual development, promote bone/muscle growth,respond to stress, and fight disease.
The Hippocampus is vital to our memory system. However, memories here are not stored permanently. Rather, they are processed in this area and then sent to other locations in the cerebral cortex for permanent storage. Since memories must pass through the hippocampus to be encoded first, people with damage to their hippocampus cannot retain new information.
The frontal lobe is located at the top front part of the brain behind the eyes. The anterior of this lobe, called the prefrontal cortex, plays a critical role in directing thought processes, foreseeing consequences, pursuing goals, and maintaining emotional control. Phineas Gage's case exemplifies the importance of this area. When Gage's limbic system was separated from his frontal lobes, he lost emotional control and became impulsive. The frontal lobes are home to Broca's and Wernicke's areas, two areas vital to language processing. Even more, located near the back of the lobe is the motor cortex, which controls voluntary movement.
Located on the side of the brain, the temporal lobe interprets and processes sound sensed by the ears. This area also deals with speech perception(Left temporal lobe= speech, right temporal lobe=facial recognition). The auditory cortex is not lateralized, and so sound recieved by the left ear is processed in the auditory cortices of both hemispheres. Damage to the temporal lobe would affect language comprehension. The subject may be able to speak fluently but will lack syntax and grammer needed for proper communication.
Located on the top of the brain, the parietal lobes contain the sensory cortex(also known as the somato-sensory cortex). The sensory cortex is a thin strip that receives incoming touch sensations from the body and is organized in similar fashion to the motor cortex. The parietal lobes are also involved in spatial and visual perception.
The occipital lobes are located at the very back of the brain, farthest away from the eyes. The major function of this lobe, ironically, is to interpret messages from the eyes in the visual cortex. Impulses from the retinas are sent to the visual cortex located here for interpretation. Impulses from the right halves of the retinas are processed in the right occipital lobe, and those from the left halves of the retinas are processed in the left occipital lobe.
The right and left hemispheres are joined by a bundle of fibers called the corpus callosum. This bundle is responsible for the exchange of information and messages between the two sides of the brain and is composed of white matter. It is also the largest bundle of nerve fibers in the entire nervous system.