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Hypothalamus is a part of central nervous system. It acts as an interface between ______. One of its functions is to control ________.
- the brain and endocrine system
- pituitary gland
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Pituitary gland is composed of __________. It receives _________ from the hypothalamus and secretes _____ that circulate to the rest of the body.
- distinct neural and endocrine tissues
- both neuronal and endocrine signals
- hormones
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Three modes of hypothalamic control over the endocrine system
- neuroendocrine over anterior lobe of pituitary gland
- neuroendocrine via posterior lobe of pituitary gland
- direct neural control (sympathetic) over the endocrine cells of the adrenal medullae
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Hypothalamic neurons secrete both regulatory hormones that control the release of a second hormone from endocrine cells in the _______ and hormones directly into ____ in the ______.
- anterior pituitary gland
- the blood
- posterior pituitary gland
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The hypothalamus/pituitary serves as an interface for inputs from the brain and ______ to control body functions through endocrine regulation; affect almost every other organ system of the body.
hypothalamic regulatory centers
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Pituitary hormones directly regulate:
- Water Balance - kidney
- Metabolic Rate
- Lactation - mammary gland
- Milk Secretion - mammary gland
- Body Growth
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Behaving as a master gland, pituitary hormones control the secretion and growth of the following endocrine glands:
- Thyroid Gland
- Adrenal Glands
- Reproductive Glands
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Posterior pituitary, (________) is ______ in origin and contains __________ that release hormones into the ___.
- neurohypophysis
- neural
- axons that project directly from the hypothalamus to nerve terminals
- blood
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Anterior pituitary (_______) contains ____ cells regulated _________ signals from the _______ that are released in the _______.
- adenohypophysis
- endocrine
- indirectly by neuroendocrine
- hypothalamus
- median eminence
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The posterior pituitary, also know as the ________, is derived from _______.
- neurohypophysis
- neuroectoderm
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The anterior pituitary, also know as the ________, is derived from ______. Axons from _______ terminate in a ______ region, the median eminence, where they secrete regulatory (releasing and inhibiting) hormones into a local circulation that delivers ____ concentrations to the anterior pituitary.
- adenohypophysis
- oral ectoderm
- hypothalamus
- neurovascular
- high
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Posterior pituitary ‐ Hormones are transported within _____ from ______ and stored at _____ in _______. Release occurs in the ______ of the posterior pituitary.
- axons
- cell bodies in the hypothalamus
- nerve terminals
- posterior pituitary
- separate blood supply
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Anterior pituitary – Hormones from the ______ are secreted in ________ and pass through _____ to the anterior pituitary, where they regulate pituitary gland _______, which secrete secondary hormones that pass into the general circulation.
- hypothalamus
- median eminence
- the portal vein
- endocrine cells
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Hormones released from the posterior pituitary are referred to as _______, including:
- neurohormones
- Vasopressin (antidiuretic hormone, ADH)
- Oxytocin
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Vasopressin (also know as antidiuretic hormone, ADH) plays a key role in _______.
the regulation of body fluid volume by enhancing the retention of free water by the kidney
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Oxytocin's primary role is to _______. Also can _______.
- stimulate the ejection of milk from the lactating mammary gland
- stimulate contraction of the uterus
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feedback inhibition on vasopressin secretion
increased ECF osmolarity -> increased ADH secretion -> increased water retention -> dilution of ECF
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_____ relationship between plasma vasopressin (ADH) and plasma osmolality.
_____ relationship between vasopressin level and blood volume/pressure.
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Deficiency of vasopressin (ADH) causes ______.
diabetes insipidus
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As a consequence of disease or trauma, the neurons responsible for secreting vasopressin (ADH) can be damaged. Failure to secrete sufficient vasopressin to maintain normal plasma osmolality causes _______.
Urine volume can reach 1000 ml/hr
osmolalities as low as 50 mOsm/kg
frequent urination
drink large volumes of water (_____) to prevent collapse from volume depletion and hyperosmolality.
- excessive loss of water in urine
- polydipsia
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Treatment with _____ provides rapid relief for diabetes insipidus.
vasopressin
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______ stimulates oxytocin release through afferent sensory neuronal signals to the ______. Oxytocin is released into the circulation and causes ________.
- Suckling
- hypothalamus
- contraction of cells that line the breast ducts, resulting in milk ejection
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In pregnancy, oxytocin release is stimulated at ____ by _________, which elicit neuronal signals to the ________ to induce oxytocin release. Oxytocin acts to _______.
Oxytocin also enhances _______ of the uterus after parturition.
- term
- uterine contractions and distention of the cervix
- hypothalamus
- increase uterine contractility
- * positive feedback
- involution
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Hormones derived from hypothalamic neurons are secreted in the median eminence and delivered to the anterior pituitary through the _______. This yields _______ of the releasing and inhibitory hormones at the target pituitary cells.
- portal vein
- a high concentration
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Releasing Hormones act on ________ of specific pituitary endocrine cells to stimulate ______ and/or _______ of the pituitary hormones.
- plasma membrane receptors
- the exocytosis
- the synthesis
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Releasing hormones are released at the median eminence in _____.
waves
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Cellular mechanisms of action of hypothalamic releasing hormones on anterior pituitary cells
receptors
second messengers
actions
- almost all GPCR
- second messengers: Ca++, IP3, cAMP
- modulate transcription, post-translation modification, exocytosis
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Regulatory hormones, target pituitary cells and target hormones
Thyrotropin‐Releasing Hormone (TRH) -> Thyrotroph -> Thyrotropin (TSH) or ...-> Mammotroph -> Prolactin
Gonadotropin‐Releasing Hormone (GnRH) -> Gonadotroph -> Luteinizing Hormone (LH) and Follicle‐Stimulating Hormone (FSH)
Corticotropin‐Releasing Hormone (CRH) -> Corticotroph -> Adrenocorticotropic Hormone (ACTH, Corticotropin)
Growth Hormone‐Releasing Hormone (GHRH) -> Somatotroph -> Growth Hormone (GH, Somatotropin)
Growth Hormone‐Inhibiting Hormone (Somatostatin) -> Somatotroph -> Growth Hormone (GH, Somatotropin) or ... -> Thyrotroph -> Thyrotropin (TSH)
Prolactin‐Inhibiting Factor (PIF, Dopamine) -> Mammotroph -> Prolactin
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Action of the pituitary hormones
- Thyroid‐Stimulating Hormone (TSH): Thyroid hormone secretion and enlargement of thyroid gland
- Luteinizing Hormone (LH): Ovulation and luteinization (female); testosterone secretion (male)
- Adrenocorticotropic Hormone (ACTH): Hormone secretion and cell growth in adrenal cortex
- Growth Hormone (GH): Body growth; secretion of IGF‐I
- Prolactin: Milk secretion
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An important mechanism of regulation of pituitary hormone release is _________.
through negative feedback exerted by the peripheral hormones on both the pituitary and hypothalamus
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Growth hormone (GH) is a _____ hormone secreted by the _______ cells of the _____ pituitary.
GH has a key role in _______. GH also plays an important role in _______.
GH secretion from the anterior pituitary is regulated by _______ from the hypothalamus.
- polypeptide
- somatotroph
- anterior
- the stimulation of growth and development of children
- regulating metabolism, which continues in adults
- both positive (GH‐RH) and inhibitory (Somatostatin, GH‐IH) factors
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In addition to direct peripheral targets, GH also stimulates the secretion of ________, which exerts ______ feedback on GH secretion by ______.
- somatomedin (IGF, Insulin-like Growth Factor) from liver and other tissues
- negative
- inhibiting hypothalamic GHRH secretion and enhancing GH‐IH secretion, which inhibits the secretion of GH at pituitary level
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Growth hormone (GH) acts on peripheral tissues directly, but also acts through _____, which stimulate anabolic responses of bone, muscle and other organs to increase _____ and enhance _______.
- the release of secondary peptide hormones called Somatomedins (also know as insulin‐like growth factors, IGF‐1 and IGF‐2)
- protein synthesis
- cell proliferation and growth
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The direct effects of GH oppose some of the actions of insulin, since it ________ (thus GH is _______)
- inhibits glucose uptake and enhances lipolysis
- diabetogenic
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Metabolic and growth targets of GH and Somatomedin (IGF‐1).
- both induce protein synthesis and epiphysial growth
- GH: stims lipolysis and decreases insulin sensitivity
- IGF-1: induces insulin-like activity and has antilipolytic activity
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GH overall actions
- increase metabolism, linear growth, lean body mass, organ size and function
- decrease adiposity
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Role of Growth Hormone, Thyroid Hormones and Androgens/Estrogens in mediating human growth
- Thyroid hormones dominates during early childhood, results in very high rate of growth, then decreases continuously
- growth hormone peaks at 2-3, stays high till 16, then decreases
- sex hormone peaks during puberty, responsible to the 2nd growth peak
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Too much growth hormone (GH) during childhood can result in _____.
Too little GH can result in ______.
Mental development under both situations are ______.
- gigantism
- pituitary dwarfism
- normal
* body growth is in proportion
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Acromegaly is a syndrome caused by _______, usually from a ______. This causes a variety of changes, including ______, accumulation of excess soft tissue, thickening of skin and _______. Results in _________. Diabetes may also occur. Treatment is by _______.
- sustained hypersecretion of GH
- pituitary somatotroph tumor
- widening of bones
- hair growth
- coarser facial features, enlarged hands and feet and overdevelopment of muscles
- surgery or somatostatin analogs
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Prolactin (PRL) is a ______ hormone. It's major effects are ________.
- polypeptide
- to stimulate breast development and milk production in women
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Prolactin Levels increase during ______, and are further stimulated by ____. Prolactin secretion is also enhanced by ________.
- pregnancy
- nursing
- high estrogen levels acting directly on the mammotrophs of the anterior pituitary
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Hypothalamic regulation of PRL secretion is predominantly through _______.
Less important are _________.
There is also negative feedback on the hypothalamus by ________.
- dopamine (PIF), which is an inhibiting hormone
- the releasing hormones Thyrotropin Releasing Hormone (TRH) and Vasoactive Intestinal Peptide (VIP) * positive
- prolactin stimulation of dopamine release
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Pituitary Intermediate lobe secrets ________, which _________.
- Melanocyte‐stimulating hormone (MSH)
- Expand melanophores in fish, amphibians, and reptiles; stimulate melanin synthesis in melanocytes in humans.
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