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(hī″pō-tĕn′sĭv) 1. Characterized by or causing low blood pressure. 2. An agent that lowers blood pressure.


(hī″pō-thal′ă-mŭs) [hypo- + thalamus] The inferior aspect of the diencephalon of the brain. It is the regulator of the essential homeostatic balance of body fluids, salt concentrations, temperature, and energy metabolism as well as the governor of reproductive cycles and certain emotional responses. The hypothalamus is a single structure, but it comprises two mirror-image walls of neural tissue on the left and the right sides of the ventral half of the third ventricle. In the embryo, these walls are at the front end of the neural tube; in the adult, the hypothalamus begins at the lamina terminalis (at the base of the frontal lobes) and just below the lamina terminalis; the optic chiasm lies in front of the hypothalamus. The base of the hypothalamus ends in a stalk (the infundibulum) from which hangs the pituitary gland (the hypohysis); farther caudally, two mammillary bodies bulge from the bottom of the hypothalamus. At the top of the hypothalamus, the lateral ventricles empty into the third ventricle via a left and a right interventricular foramen, and behind (caudal to) the foramina are the right and left thalami. The hypothalamus is the central controller of the preganglionic sympathetic and parasympathetic nervous systems; it is also the central regulator of the pituitary gland. The hypothalamus is a collecting zone for input from the cerebral cortex, the hippocampus, the amygdala, the retina, and the brainstem; it sends output to the cerebral cortex, the thalamus, the brainstem, and the pituitary gland. Besides the pituitary gland and the mammillary bodies, the hypothalamus contains many discrete CNS nuclei in its walls, and these nuclei are categorized according to their regional locations. The anterior region (which is subdivided into the preoptic and supraoptic areas) contains nuclei involved in the regulation of gonadal hormones, body fluid levels, body temperature, and circadian rhythm; the middle (infundibular or tuberal) region contains nuclei involved in regulating levels of adrenocortical, thyroid, growth, and gonadal hormones; and the posterior (mammillary) region is a central part of the midbrain-mammillary-thalamic-midbrain circuit of the limbic system. SEE: releasing hormone.


(hī-pŏth′ĕ-năr) [″ + thenar, palm] The fleshy prominence on the inner side of the palm next to the little finger. SYN: hypothenar eminence.

hypothenar hammer syndrome

Damage to the ulnar artery from sports or occupations in which a person uses the side of the hand as a pounding tool, resulting in recurrent blunt trauma to the hand. It occasionally causes Raynaud phenomenon or other forms of digital ischemia.


(hī″pō-thĕr′măl) [″ + therme, heat] 1. Tepid. 2. Subnormal temperature.


(hī″pō-thĕr′mē-ă) [hypo- + therm- + -ia] 1....

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