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Chapter 15: Hypothalamus (Diencephalon (pineal gland, thalamus,…
Chapter 15: Hypothalamus
Diencephalon
pineal gland
thalamus
subthalamus
hypothalamus - very small, very important
Hypothalamus part of homeostasis
balanced functioning of physiological processes and maintenance of an organism's internal environment within a narrow range
temperature
blood volume
blood pressure
salinity
acidity
blood O2
blood glucose
accomplishes this by controlling
autonomic nervous system
projections to sympathetic and parasympathetic neurons
endocrine system
via anterior and posterior pituitary gland
motivated homeostatic behaviors (feeding, drinking, etc.)
via connections with forebrain, limbic system, brainstem, spinal cord
Organization of the hypothalamic nuclei
periventricular area
hypothalamic medial area
4 regions from rostral to caudal
preoptic area
anterior (supraoptic) region
middle (tuberal) region
posterior (mammillary) region
lateral hypothalamic area
Hypothalamic control of posterior pituitary
Magnocellular neurosecretory cells in supraoptic nucleus and paraventricular nucleus
projects to posterior pituitary and secretes 2 hormones into a capillary bed in the posterior pituitary
oxytocin
"love hormone"
rises during sexual behavior
promotes social bonding
uterine contractions (Pitocin given to induce labor), push baby out of uterus
milk letdown reflex
stimulates ejection of milk from mammary glands
sight/sound of baby can subconsciously cause mom to lactate
vasopressin (antidiuretic hormone, ADH) diuretic means to stimulate urine
regulates blood volume
regulates salt concentration
when body's water deprived, blood volume goes down, blood salt goes up
vasopressin release acts directly on kidneys and leads to water retention, reduced urine production
Hypothalamic control of anterior pituitary
parvocellular neurosecretory cells in the paraventricular nucleus
secrete releasing hormones into the hypothalamic-pituitary portal circulation.
releasing hormones travel in portal circulation to anterior pituitary
receptors for hypothalamic hormones cause anterior pituitary cells to release or stop releasing their hormones into blood
Stress response - leads to release of cortisol
Cortisol
releases glucose into bloodstream
increases blood pressure for increased physical activity like running or fighting
stimulates brain for more intense awareness
immune system activity is reduced to save energy for physical activity
HPA Axis
Hypothalamus
stress: physiological stress, anxiety
Parvocellular neurosecretory neurons
release CRH
Anterior pituitary triggers release of ACTH into general circulation
Stimulates release of cortisol from adrenal cortex
Cortisol inhibits CRH release
Hypothalamus also controls the Autonomic Nervous System
Visceral functions (salivating, sweating, genital stimulation) depends on sympathetic and parasympathetic divisions of ANS whose post ganglionic neurons lie outside CNS in autonomic ganglia
Sympathetic
"fight or flight"
activates physiological responses
increased heart rate
respiration
blood pressure
Parasympathetic
"rest and digest"
maintains heart rate and respiratory, metabolic, digestive functions under normal conditions