Hypothalamus between

Arousal is a state of vigilance regulated by subcortical parts of the nervous system, especially connections between the nuclei of the amygdala, the hypothalamus and the brain stem. These unconscious responses prepare the body for action. 

Figure 22.3 Possible links in the induction of circadian rhythm between daylight, the suprachiasmatic nucleus and melatonin release from the pineal gland. Some fibres in the optic nerve, projecting from the eye to the lateral geniculate nucleus (LGN) in the thalamus, innervate the suprachiasmatic nucleus (SCN) in the anterior hypothalamus, via the retinohypothalamic tract (RHT). Others project to the SCN from the LGN in the geniculohypothalamic tract (GHT). The release of melatonin into the circulation from the pineal gland (PG) is maximal at night and appears to be controlled partly by noradrenaline released from sympathetic nerves originating in the superior cervical ganglion (SCG). Melatonin receptors are found in the SCN, the removal of which dampens melatonin secretion...

The female menstrual cycle is divided into four functional phases follicular, ovulatory, luteal, and menstrual.6 The follicular phase starts the cycle, and ovulation generally occurs on day 14. The luteal phase then begins and continues until menstruation occurs.6 The menstrual cycle is regulated by a negative-feedback hormone loop between the hypothalamus, anterior pituitary gland, and ovaries6 (Fig. 45-1). 

Describe anatomical and functional relationships between the hypothalamus and the pituitary gland... 

The adenohypophysis does not have a direct anatomical connection with the hypothalamus therefore, regulation of hormone secretion by way of neuronal signals is not possible. Instead, these two structures are associated by a specialized circulatory system and the secretion of hormones from the adenohypophysis is regulated by hormonal signals from the hypothalamus (see Figure 10.2). Systemic arterial blood is directed first to the hypothalamus. The exchange of materials between the blood and the interstitial fluid of the hypothalamus takes place at the primary capillary plexus. The blood then flows to the adenohypophysis through the hypothalamic-hypophyseal portal veins. Portal veins are blood vessels that connect two capillary beds. The second capillary bed in this system is the secondary capillary plexus located in the adenohypophysis. 

Figure 2.4 Flip-flop switch model of wake and slow wave sleep active systems. Mutually inhibitory connections exist between GABAergic/Galaninergic slow wave sleep active neurons in the ventrolateral preoptic area (VLPO) of the anterior hypothalamus and aminergic neurons in the hypothalamus (histamine (HA) neurons in the tuberomammillary nucleus (TMN)) and brainstem (serotonin (5-HT) neurons in the dorsal raphe (DR) and noradrenaline (NA) neurons in the locus coeruleus (LC)). Orexinergic neurons in the perifornical hypothalamus (PFH) stabilize the waking state via excitation of the waking side of the flip-flop switch (aminergic neurons).

Guan, J. L., Uehara, K., Lu, S. et at (2002). Reciprocal synaptic relationships between orexin- and melanin-concentrating hormone-containing neurons in the rat lateral hypothalamus a novel circuit implicated in feeding regulation. Int. J. Obes. Relat. Metab. Disord. 26, 1523-32. 

Diencephalon The between brain connecting the midbrain and forebrain which comprises the thalamus and hypothalamus. 

Two tyrosine kinase-based mechanisms have been described the IR and the JAK/ STAT cascades. It should not be assumed that these are either/or mechanisms as there may be parallel transduction (cross-talk) between the two pathways. For example, leptin, an appetite suppressor described more fully in Chapter 9 is a cytokine-like peptide produced by adipose tissue, which signals in the hypothalamus of the brain via JAK2/STAT3, but also influences the IRS/PI3K pathway. 

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