Home | Login | Join | Mission Center

| CENTER | 4TH MISSION | HISTORY | CH GROWTH | THEOLOGY | MINISTRY | SHARING | Q & A | PASTORS | VIDEO/AUDIO | FREE BOARD

Join Lost PSW
ID
PW
Keep ID








Hypothalamus (Biological Clock/Inner Clock)
Paul Jang  2008-03-04 13:44:05, hit : 4,136
Download : Hypothalamus_(2007).doc (12.3 KB)

Hypothalamus (2007).



REFERENCES 1. (Study on the Biological Clock/Inner Clock)


The Thalamus

The egg-shaped thalamus (thal'ah-mus) makes up 80% of the diencephalon and forms me superoraleral walls of the third ventricle. The right and left thalamus are
joined by a small midline commissure, the intermediate mass. Thalamus is a Greek word meaning "inner room," which well describes this deep brain region.

The thalamus contains about a dozen major nuclei, each of which sends axons to
the cerebral cortex(Figure 12.14). Some thalamic nuclei act as relay stations for the
sensory information ascending to thepriniary sensory areas of the cortex. Afferent
impulses ^?m all the conscious senses converge on the thalamus and synapse in at
least one of its nuclei. For example, the ventral posterior lateral nucleus, receives
general somatic sensory information. The lateral and medial geniculate nuclei
(je-nik'u-lat; ("Knee shaped") receive visual and auditory information, respectively.

Sensory imputs are not me only type if of information relayed through the
thalamus. Every part of the brain that communicated with the cerebral cortex must relay its signals through a nucleus of the thalamus. The thalamus can therefore
thought of as the "gateway" to the cerebral cortex.

The thalamus not only relays information to the cortex but also actively processes
the information as it passes through. The thalamic nuclei organize, amplify, or "tone
down" the signals headed for the cerebral cortex. There are many other relay nuclei
in the brain, all of which process and "edit: information before sending it along.

The division of labor among the different thalamic nuclei is remarkable. Each
nucleus receives imput from its own specific region of the CNS and in turn projects
information to its own specific region of the cerebral cortex.


The Hypothalamus

The hypothalamus(hi"po-thal'ah-mus; "below the thalamus) is the inferior division of the (diencephalon(Figures 12, 13, 12.15, and 12.16). It forms the inferolateral walls of the third ventricle. On the underside of me brain, it lies between the optic chiasma(point of crossover of clanial nerves II, the optic nerves) and the posterior border of the mammillary bodies. The mammillary bodies are rounded bumps that
bulge from the hypothalamic floor (mammillary = "little breast"). The pituitary gland also projects inferiorly from the hypothalamus. This gland cecretes many hormones.
The hypothalamus, like the thalamus, contains about a dozen nuclei of gray matter(Figure 12>15). Functionally, the hypothalamus is the main visceral control center of the body-regulating many activities of the visceral organs. Its functions include the following:

1. Control of the autonomic nervous system.

As you will recall, the autonomic nervous system is me system of peripheral motoe neurons that regulates contraction of smooth and cardiac muscle and the secretion of glands (p. 297). The hypothalamus exerts control over the autonomic neurons. In doing so, it regulates heart rate and blood pressure, movement of the digestive tube, the secretion of sweat glands, and salivary glands and many other visceral activities.

2. Center for emotional response.

The hypothalamus lies at the center of emotional part of the brain, the limbic system. Regions involved in pleasure, rage, sex drive, and fear have been located in the hypothalamus.

3. Regulation of body temperature.

The body's thermostat is in the hypothalamus. Some hypothalamic neurons sense blood temperature, then initiate the body's cooling or heating mechanisms as needed(sweating , shivering).

4. Hunger and thirst centers.

By sensing the concentrations of nutrients and salts in the blood, certain hypothalamic neurones mediate feelings of hunger and thirst.

5. Sleep-wake cycles.

Acting with other brain regions, the hypothalamus helps regulate the complex phenomenon of sleep. The hypothalamus is responsible for the (timing of the sleep cycle. The nuclei involved seem to be the supra chiasmatic (soo"prah-ki-az-mat'ik) nucleus above the optic chiasma and the pre-optic nucleus anterior to that(Figure 12.15). The supra-chiasmatic nucleus is tile body's biological clock, regulating many daily rhythm (circaldian rhythms). It receives information on daylight-darkness cycles from the eye through me. optic nerve, men send signals to the. preoptic nucleus. In response to such signals, the pre-optic nucleus induces sleep.

6. Control of the endocrine system.

The hypothalamus controls the secretion of hormones by the pituitary gland, which in mm regulates many functions of the visceral organs (Chapter 24).

Through experiments that stimulate or remove parts of the hypothalamus, it has
become possible to localize each of the above functions to a general regions of me
hypothalamus. These regions are called functional centers. For the most part, the
functional center can be only roughly matched with specific structural nuclei.

Try to predict some if the functional disorders that result from injuring the
hypothalamus. Hypothalamic lesions cause a number of disorders in visceral functions and in emotions. These can include severe weight 'loss or obesity, sleep disturbance,
dehydration, and a broad range of emotional disorders.


Technical Terms

◉ Corticotropin releasing hormone (CRH) a factor secreted by the hypothalamus that stimulates the pituitary to release adrenocorticotropic hormone.

◉ Adrenocorticotropic. acting on or stimulating the adrenal cortex

◉ ACTH. [adrenocorticotropic hormone] (1947) : a protein hormone of the anterior lobe of the pituitary gland that stimulates the adrenal cortex-called also adrenocorticotropic hormone.





..



 

Copyright ¨Ï 2008 Fourth World Mission Center. All rights reserved.
Phone : (714) 842-1918, (424) 293-8818, E-mail : revpauljang@hotmail.com
Address : 16000 Villa Yorba Lane #131, Huntington Beach, CA 92647, U.S.A
Mission Center Homepages : www.mission4.org / www.usmission4.org / www.mission4.info