Notes

Hypothalamus:
Almond sized region of the brain, located anterior and inferior to thalamus. Forms the floor and lower walls of third ventricle. Anatomically related to pituitary gland. Important for homeostasis and hormones.
Composed of several pairs of nuclei, divided into regions; preoptic, supraoptic, tuberal, and mamillary.
Hypothalamus regulates homeostasis by coordinating the ANS, endocrine system, and limbic system.
Functions of hypothalamus: blood pressure/electrolyte response, reproductive behaviours, sleep-wake cycle, energy metabolism, body temperature, and defensive behavior.
Inputs to hypothalamus: most complex circuitry
- prefrontal cortex (executive functioning) supplies sensory info sends input via thalamus
- cingulate cortex (emotion processing) supplies info on emotional state sends input via thalamus
- hypothalamus has intrinsic sensory neurons (projections within hypothalamus) that responds to physiological stimuli
- hippocampus and amygdala supply emotional info
- reticular formation and nucleus of solitary tract provide info about arousal and visceral info
- retina supplies info that contributes to circadian rhythm regulation
Hypothalamus receives input from internal environment that signal changes in blood levels of circulating substance e.g. glucose. It also receives input from external environment about light, temp, and external threats.
Hormone production and release are controlled by negative feed back. Once hormone reaches a certain level in the blood a signal is released that stops it. Maintains hormone conc. within a narrow range. The hypothalamic-pituitary-adrenal axis describes the interaction between the hypothalamus pituitary, and adrenal glands --> regulates stress response.
Outputs from hypothalamus:
- neural connections are bidirectional
- receives inputs but also sends outputs to prefrontal cortex, septal area, hippocampus, amygdala, periaqueductal grey, brain stem
- neurons within hypothalamus make direct and indirect connections with sympathetic and parasympathetic preganglionic neurons to regulate autonomic output
- connections via pituitary gland release hormones into peripheral blood stream
Stress response:
- ANS provides most immediate to stess through its sympathetic and parasympathetic system, which provide rapid alterations in physiological states. Sympatho-adrenal axis can rapidly increase heart rate and blood pressure within seconds. Response is short lived because of reflexive parasympathetic activation
- HPA elevates circulating glucocorticoids with peak plasma levels occurring in tens of minutes. Takes longer to trigger.

Hypothalamus and Pituitary Gland:
Pituitary us pea sized structure attached to base of brain - body's main endocrine gland. Posterior pituitary: secretes hormones oxytocin and vasopressin
Anterior pituitary: secretions hormones that influence growth, sexual development, skin color, thyroid and adrenocortical function
- hypothalamus is connected by a bridge of nerve axons call the hypothalamic-hyposeal tract. 0 - - Magnocellular neurosecretory cells in hypothalamus release 2 hormones in posterior pituitary where they are stored and released in the blood via capillary plexus. MNCs in paraventricular nucleus release vasopressin (ADH), MNCs in supraoptic nucleus of the hypothalamus release oxytocin.
- both hormones synthesized as pre-hormones in cell bodies and then processed into 9 amino acid peptides.
- transported to pituitary by neurophysin. 2 for vasopressin and 1 for oxytocin.
- stored in secretory granules with carrier protein. Herring bodies are accumulation of granules
Vasopressin:
- principally acts on the kidneys and blood vessels to regulate osmotic balance, BP, sodium homeostasis, and kidney functioning
- primary function is to regulate ECF volume by acting on V2 receptors in the renal tubules to increase water permeability and decreased urine formation. Results in increased blood volume, cardiac output, and arterial pressure.
- causes vasoconstriction on smooth muscle via V1 receptors
- alcohol inhibits ADH
Oxytocin:
- acts on mammillary glands and uterine smooth muscle to control stimulation of milk let down and contraction during birth
- positive feedback loop
Hypothalamus connected to the anterior pituitary via the hypophyseal portal system. Neurosecretory cells in the hypothalamus secrete hypothalmatic releasing or inhibiting hormones.