hypothalamus Flashcards
controls the autonomic nervous system and the endocrine system and thus indirectly controls body homeostasis
hypothalamus
lies below the thalamus and forms the floor and the inferior part of the lateral walls of the third ventricle
hypothalamus
Caudally, the hypothalamus merges into the ___ of the midbrain
tegmentum
The lateral boundary of the hypothalamus is formed by the ___
internal capsule
hypothalamus is seen to be related to the following structures, from anterior to posterior:
One tree makes dew VIP
- the optic chiasma
- tuber cinereum and the infundibulum
- mammillary bodies
- dorsomedial nucleus
- ventromedial nucleus
- infundibular (arcuate) nucleus
- posterior nucleus
In the lateral zone, the following hypothalamic nuclei can be recognized, from anterior to posterior:
- preoptic nucleus
- suprachiasmatic nucleus
- supraoptic nucleus
- lateral nucleus
- tuberomammillary nucleus
- lateral tuberal nuclei
General somatic sensation and gustatory and visceral sensations reach the hypothalamus through collateral branches of the lemniscal afferent fibers and the tractus solitarius and through the reticular formation
Somatic and visceral afferents
leave the optic chiasma and pass to the suprachiasmatic nucleus
Visual afferents
travels through the medial forebrain bundle
Olfaction
have not been identified, but since auditory stimuli can influence the activities of the hypothalamus, they must exist.
Auditory afferents
arise from the frontal lobe of the cerebral cortex and pass directly to the hypothalamus
Corticohypothalamic fibers
pass from the hippocampus through the fornix to the mammillary body. Many neurophysiologists regard the hypothalamus as the main output pathway of the limbic system
Hippocampohypothalamic fibers
pass from the amygdaloid complex to the hypothalamus through the stria terminalis and by a route that passes inferior to the lentiform nucleus
Amygdalohypothalamic fibers
arise from the dorsomedial and midline thalamic nuclei.
Thalamohypothalamic fibers
arise from the midbrain
Tegmental fibers
- influence the peripheral neurons of the autonomic nervous system
- The hypothalamus is connected to the parasympathetic nuclei of the oculomotor, facial, glossopharyngeal, and vagus nerves in the brainstem.
Descending fibers to the brainstem and spinal cord
- arises in the mammillary body and terminates in the anterior nucleus of the thalamus
- pathway is relayed to the cingulate gyrus
mammillothalamic tract
arises from the mammillary body and terminates in the cells of the reticular formation in the tegmentum of the midbrain
mammillotegmental tract
Multiple pathways to the ___
limbic system
The hypothalamus is connected to the hypophysis cerebri (pituitary gland) by two pathways:
- nerve fibers that travel from the supraoptic and paraventricular nuclei to the posterior lobe of the hypophysis and
- long and short portal blood vessels that connect sinusoids in the median eminence and infundibulum with capillary plexuses in the anterior lobe of the hypophysis
- synthesized in the nerve cells of the supraoptic and para- ventricular nuclei
- passed along the axons together with carrier proteins called neurophysins and are released at the axon terminals
vasopressin and oxytocin
- antidiuretic hormone
- produced mainly in the nerve cells of the supraoptic nucleus
- cause vasoconstriction
- has an important antidiuretic function, causing an increased absorption of water in the distal convoluted tubules and collecting tubules of the kidney
vasopressin
- produced mainly in the paraventricular nucleus
- stimulates the contraction of the smooth muscle of the uterus and causes contraction of the myoepithelial cells that surround the alveoli and ducts of the breast
oxytocin
- stimulates labor contractions of the uterus
- when the baby suckles at the breast, a nervous reflex from the nipple stimulates the hypothalamus to produce more of the hormone.
oxytocin
The releasing hormones stimulate the production and release of
adrenocorticotropic hormone (ACTH)
- follicle-stimulating hormone (FSH)
- luteinizing hormone (LH)
- thyrotropic hormone or thyroid-stimulating hormone (TSH)
- and growth hormone (GH)
the release of inhibiting hormones inhibits the release of the
melanocyte-stimulating hormone (MSH) and luteotropic hormone (LTH)
The hypothalamus has a controlling influence on the ___ and appears to integrate the autonomic and neuroendocrine systems, thus preserving body homeostasis
autonomic nervous system
- Electrical stimulation of the anterior hypothalamic area and the preoptic area influence ___
- lowering of the blood pressure, slowing of the heart rate, contraction of the bladder, increased motility of the gastrointestinal tract, increased acidity of the gastric juice, salivation, and pupillary constriction
parasympathetic responses
- Stimulation of the posterior and lateral nuclei causes ___
- elevation of blood pressure, acceleration of the heart rate, cessation of peristalsis in the gastrointestinal tract, pupillary dilation, and hyperglycemia
sympathetic responses
- The nerve cells of the hypothalamic nuclei, by producing the releasing factors or release-inhibiting factors
- control the hormone production of the anterior lobe of the hypophysis
endorcrine control
- of the hypothalamus controls those mechanisms that dissipate heat loss
- dilatation of skin blood vessels and sweating, which lower the body temperature.
anterior portion
Stimulation of the ___ of the hypothalamus results in vasoconstriction of the skin blood vessels and inhibition of sweating; there also may be shivering, in which the skeletal muscles produce heat
posterior portion
- Stimulation of the ___ of the hypothalamus initiates the feeling of hunger and results in an increase in food intake
- hunger center
- Bilateral destruction of this center results in anorexia, with the consequent loss in body weight
lateral region
- satiety center
- Stimulation of the ___ of the hypothalamus inhibits eating and reduces food intake
- Bilateral destruction of the satiety center produces an uncontrolled voracious appetite, causing extreme obesity
medial region