Physiology 2130 Lecture Notes - Lecture 10: Supraoptic Nucleus, Paraventricular Nucleus Of Hypothalamus, Posterior Pituitary
5 May 2018
School
Department
Course
Professor
Hypothalamus and Homeostasis –Dr. Ciriello
▪ Hypothalamus and Limbic System
o Neurons controlling the internal environment are concentrated in a region of
the brain called the hypothalamus
o The hypothalamus is greatly influenced by and
operated in conjunction with higher control systems
located in the brain called collectively the limbic
system
o The hypothalamus is strategically located to
influence the antinomic nervous system, the pituitary
gland and the endocrine system
o It is located at the base of the brain, beneath the
thalamus and just above the pituitary gland
▪ Functions of the Hypothalamus
o Control of the Autonomic Nervous System
o Neuroendocrine Control
▪ Posterior pituitary gland
▪ Catecholamine release from adrenal medulla
o Reproduction
▪ Behaviour and pituitary function
o Water Balance and Exchange
o Sodium Balance and Exchange
o Body Energy Balance and Exchange
▪ Nutrient intake and metabolism
o Drive and Emotions
▪ Feeding, attack
o Circadian Rhythms
▪ Sleep, day/night menstrual cycle
o Body Temperature Regulation
▪ Areas of the Hypothalamus
o Supraoptic nucleus
▪ Water Balance
o Suprachiasmatic nucleus
▪ Biological clock
o Arcuate Nucleus
▪ Satiety/Feeding
o Paraventricular Nucleus
▪ Water Balance/ Stress/ Feeding
o Lateral Hypothalamus
▪ Feeding
o Preoptic/ Anterior hypothalamic region
▪ Blood Pressure Regulation (PSNS)/ Body Temperature Regulation
o Posterior hypothalamus
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▪ Blood Pressure Regulation (SNS)/ Body Temperature Regulation
o Basomedial hypothalamus
▪ Anterior Pituitary Releasing Factors
▪ Association of the hypothalamus with the limbic system
o information that is processed in the brain will also influence
the hypothalamus
o The hypothalamus is considered the master controller of the
autonomic nervous system
▪ Effects of Activation of the Posterior and Anterior Hypothalamic
Neurons
Posterior Hypothalamic Neurons
Anterior Hypothalamic Neurons
Increased Blood Pressure (SNS)
Decreased Blood Pressure (PSNS)
Increased Heart Rate
Decreased Heart Rate
Decreased Gastrointestinal Motility
Increased Gastrointestinal Motility
Increased Pupil Size
Decreased Pupil Size
▪ Pituitary Gland Control
o The hypothalamus produces several different hormone-releasing factors which
activate the anterior pituitary gland to release hormones into the circulation
o Releasing hormones secreted by the Basomedial hypothalamus reach the
anterior pituitary gland via a the hypophyseal portal system
▪ Supraoptic and Paraventricular nucleus- control of the posterior pituitary
o These two nuclei make up the posterior pituitary
o Supraoptic nucleus- Controls Water Balance
▪ Releases ADH (vasopressin)
▪ Contains neurons that produce ADH that extend to the posterior
pituitary where it is stored and released into the circulation
▪ Also produces oxytocin -involved in contractions, milk release and the
feeling of bonding with child
o Paraventricular nucleus -Controls Water Balance, Stress and Feeding
▪ Also contains neurons that produce ADH and oxytocin
▪ Neural-Humoral Reflex
o Neural component- sensory stimuli
▪ Ex. Baby sucking on nipple
o Humoral- bodily fluids
▪ Ex. Breast milk
o Sensory information from mechanoreceptors goes to
the hypothalamus
o Oxytocin produced in neurons posterior pituitary
released to blood breast receives signal and
allows for milk to be released
o Oxytocin acts on positive feedback
▪ The presence of oxytocin will turn on the neurons to produce more
oxytocin
o Pathway is sexually dimorphic – not always on
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▪ Only formed when the hormonal conditions are
met
▪ Female brain is more plastic (can be modified)
• Can make/break the connections
▪ Hypothalamic Body Water Regulation
o The lateral hypothalamus contributes to the initiation of
drinking behaviour
o Water reabsorption by the kidneys is influenced by the
release of the posterior pituitary hormone vasopressin
(ADH)
▪ Control of Vasopressin Release
o Decreased blood pressure decreased activity from
baroreceptors send signal to hypothalamus
o High osmolarity signal detected by hypothalamic osmoreceptors signal to
hypothalamus
o Low blood volume decreased signal from atrial stretch receptors signal to
hypothalamus
o Hypothalamus makes vasopressin that travels to the posterior pituitary gland
o Vasopressin is released into bloodstream
o Increased water reabsorption in kidneys
▪ Stimuli that elicit thirst and release of vasopressin
o Increased osmolarity / salt concentration
o Decreased ECF (blood) volume
o Decreased blood pressure
▪ Body Mass Index (BMI)
o A crude population measure of obesity – kg/m3 (weight/height)
▪ Obese
o Having abnormal or excessive fat accumulation that presents a risk to an
idividual’s health
o BMI >30
▪ Energy Balance
o Energy balance = energy intake – energy expenditure
o If High Energy intake - Low Energy Expended = Increase in Weight
o If Low Energy intake – High Energy Expended = Decrease in Weight
▪ Factors Contributing to Food Intake
o We eat to maintain energy balance
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Document Summary
Baby sucking on nipple: humoral- bodily fluids, ex. Breast milk: sensory information from mechanoreceptors goes to the hypothalamus, oxytocin produced in neurons posterior pituitary. Increased water reabsorption in kidneys: stimuli that elicit thirst and release of vasopressin. If high energy intake - low energy expended = increase in weight. Msh which bind to the mc4-r receptor in the paraventricular nucleus: this causes increased energy expenditure and inhibits food intake, leptin will inhibit agrp neurons which produce npy. Increased blood pressure means the blood has to keep pumping hard- heart problems. If there is heat, anterior hypothalamus tells the posterior hypothalamus not to turn on. If there is no signal from the anterior hypothalamus (you are cold) the posterior hypothalamus will cause the body to warm up: causes vasoconstriction so less blood flow to extremities- heat is conserved. Increased blood pressure (increased sns: fever good for us.
