THALAMAUS
The gateway for nerve impulses to the cortex
23.jpg24.jpg






















The thalamus is a very vital part of the brain. The major role of the thalamus is to be a gateway for information to travel to the cortex. For example, visual information from the retina is not sent directly to the visual cortex. It first has to travel through the thalamus. Also, in order to relay information on sound and touch it must first pass through the thalamus. It is the major relay stations for most sensory impulses that reach the primary sensory areas of the cerebral cortex from the spinal cord and brain stem. The thalamus also contributes to motor functions by transmitting information from the cerebellum and basal ganglia to the primary motor area of the cerebral cortex. It also relays nerve impulses between different areas of the cerebrum and plays a role in the maintenance of consciousness. There are two major parts to the thalamus.
The first is the dorsal thalamus. This portion is comprised of 15 nuclei which contain relay cells that project to the cerebral cortex.
The second is the ventral thalamus. This portion, which consists of a reticular nucleus, sits against the dorsal thalamus. The reticular cells of the ventral thalamus project into the dorsal thalamus to inhibit relay cells. Interneurons of the thalamus can also inhibit relay cells from carrying out a synapse to the cerebral cortex.
The thalamus sends major sensory information to the cortex. In order to taste, see, touch, and hear synapses must travel through the thalamus to reach the cortex. The only sensation that is excluded from thalamus activity is smell.
The thalamus plays an important role in being asleep and being awake. Thalamic nuclei have strong connections with the cortex which creates circuits that are believed to be involved with consciousness. Because of this connection the thalamus plays a strong role in arousal, awareness and activity. If a person damages their thalamus they can end up in a permanent coma. A stroke can lead to thalamatic syndrome in which there is a strong burning or aching sensation in the area followed by vast mood swings. Bilateral ischemia (inadequate blood supply) can lead to mutism and other problems with the senses. Korsakoff’s syndrome, caused by severe alcohol abuse and malnutrition, stems from damage to the mamillary body of the thalamus. Fatal insomnia is a hereditary disease which damages the thalamus causing the victim to gradually lose the ability to sleep resulting in death.