Nursing Preparation Study Guide

Nursing Preparation Study Guide The epithalamus forms part of the roof of the diencephalon superior to the third ventricle. The anterior portion of the epithalamus contains an extensive area of choroid plexus. The pineal gland is located in the posterior area of the epithalamus; this endocrine structure secretes the hormone melatonin. Melatonin regulates the day-night cycle and controls the internal sleep-wake signals. It also controls reproductive functions. The majority of the neural tissue in the diencephalon is located in the left thalamus and right thalamus (which form the lateral walls), and the hypothalamus (which makes up the floor). Ascending sensory information from the spinal cord and cranial nerves synapses in a nucleus in the left or right thalamus before reaching the cerebral cortex and conscious awareness. The hypothalamus houses centers that involve emotions and visceral processes that affect the cerebrum and regions of the brainstem. It also controls many autonomic functions and is the link between the endocrine and nervous systems. On each side of the diencephalon, the thalamus is the final relay point for ascending sensory information, which is projected to the primary sensory cortex. It filters information and only passes on small amounts of arriving sensory information. The thalamus also coordinates the activities of the basal nuclei and the cerebral cortex by relaying information betweenthem. The Hypothalamus The hypothalamus extends from the optic chiasm to the posteriormargins of the mammillarybodies. These mammillary bodies process sensory information, including olfactorysensations. They also contain motor nuclei that control reflex movements associated with eating, such as chewing, licking, and swallowing. A narrow stalk called the infundibulum extends inferiorly and connects the floor of the hypothalamus to the pituitary gland. The hypothalamus contains vital integrative and control centers, in addition to those associated with the limbic system. Hypothalamic centers may be stimulated by sensory information from the spinal cord, brainstem, and cerebrum; changes in the composition of interstitial fluid and the CSF; or chemical stimuli in the circulating blood that move across permeable capillaries to enter the hypothalamus (where there is no blood-brain barrier). The hypothalamus performs several functions: 1. The Subconscious Control of Skeletal Muscle Contractions: The hypothalamus directs somatic motor patterns associated with rage, pleasure, pain, and sexual arousal by stimulating centers in other portions of the brain. For example, the changes in a person’s facial expression that accompany rage and the basic movements associated with sexual activity are controlled by hypothalamic centers. 2. The Control of Autonomic Function: The hypothalamus controls, coordinates, and adjusts the activities of autonomic centers in the pons and medulla oblongata that regulate respiration, heart rate, blood pressure, and digestive functions.

©2018

Achieve Test Prep

Page 106

of 173