Exam 4 Review:  Chapter 12:  Diencephalon

nucleus (gray matter) - A group of specialized nerve cells or a localized mass of gray matter in the brain or spinal cord.

basal nuclei - A series of four to six paired (right and left) subcortical nuclei occupying space within the interior of the boundary area between frontal and temporal lobes of the cerebral hemispheres which receive input from cortical motor and somatosensory areas and provide output to the thalamus and midbrain; these connections (along with output from the cerebellum) are essential for execution of normal smooth coordinated voluntary movements.

epithalamus - A thin mass of nervous tissue (gray and white matter) located in the dorsal posterior subdivision of the diencephalon, and forming the roof of the third ventricle, and including the pineal gland; its gray matter is involved in emotional and visceral responses to odors and its white fibers form a link between the limbic system and other parts of the brain.

thalamus - A pair of large ovoid masses of gray matter situated in the posterior part of the diencephalon on either side of the third ventricle which process sensory impulses (except olfaction) by gating out irrelevant sensory information while directing relevant information to the cerebral cortex and it is also important in motor control; it is divided into two major part: dorsal and ventral, each of which contains many nuclei.

hypothalamus - The part of the brain which lies below the thalamus, forming the major portion of the ventral region of the diencephalon and which functions to regulate bodily temperature, water balance, carbohydrate and fat metabolism among other metabolic processes, and autonomic activities and also contributes to the regulation of internal homeostasis by neurosecretory functions which control the activity of the pituitary gland.

intermediate mass = massa intermedia - An apparently functionless mass of gray matter in the midline of the third ventricle that is found in many but not all human brains and is formed when the surfaces of the thalami protruding inward from opposite sides of the third ventricle make contact and fuse.

mammillary region - A small portion of the inferior surface of the hypothalamus containing nuclei associated with memory.

feeding center - Collections of neurons in the hypothalamus which evaluate and respond to changes in the blood levels of various nutritional metabolites, e.g., blood glucose, by issuing commands to brain stem centers that initiate behaviors leading to ingestion of foods; aka hunger center.

satiety center - The ventromedial region of the hypothalamus which is activated by hyperglycemia and by stretching sensations from the stomach to act to inhibit the feeding center of the hypothalamus, thus inhibiting food intake.

thirst center - The region of the hypothalamus which is close to the site of production of ADH; this center receives input from osmoreceptors, possibly the same ones responsible for control of ADH release; the threshold for thirst is a plasma osmolarity of about 295 mOsm/L and is rapid in onset; this center also receives input from baroreceptors when blood volume decreases and this center is responsive to angiotensin II.

pineal gland - A small organ situated in the diencephalon beneath the back part of the corpus callosum in the roof of the third ventricle of the brain which secretes the hormone melatonin; in the human it appears to play a role in sleep-wake cycles and may contribute to the regulation of the onset of puberty.

melatonin  - The hormone, a derivative of the amino acid tryptophan, produced by the pineal gland; in humans rising levels induce sleep; it also inhibits the stimulation of gonadotropin (LH) activity before puberty.

infundibulum - The stalk connecting the hypothalamus to the pituitary gland and the route for the vessels of the hypothalamic-hypophysial portal system.

pituitary gland = hypophysis - A small oval endocrine gland attached to the base of the brain by the infundibulum and housed in the sella tursica fossa of the sphenoid bone; it is regulated by the hypothalamus; it consists of an anterior and a posterior lobe, the secretions of which control many of the other endocrine glands and influence growth, metabolism, and maturation; anterior lobe hormones include growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, prolactin, luteinizing hormone, follicle-stimulating hormone and melanocyte-stimulating hormone and posterior lobe hormones include antidiuretic hormone = vasopressin and oxytocin.  nickname - the master gland.

List

6.  Six aspects of internal homeostasis coordinated by the hypothalamus.

          1.  body temperature                     5.  biological rhythms and drives

          2.  food intake/hunger                    6.  regulates output of pituitary gland = hypophysis
          3.  water and electrolyte balance   

          4.  thirst