16.6 Hypothalamus Flashcards
Also known as hypophysis; Connected to hypothalamus via infundibulum
Has 2 lobes: Anterior, posterior
Pituitary gland
Part of pituitary gland; Composed of nerve fibers and glia-like cells
Hormone storage bank
Releases neurohormones (oxytocin and ADH) secreted by hypothalamus
Smaller - stains lighter
Posterior pituitary
Part of pituitary gland; Composed of glandular tissue; Makes and releases hormones
Releasing and inhibiting hormones from hypothalamus regulate release
Larger - stains darker
Anterior pituitary
What maintains connection of posterior pituitary and hypothalamus; Connected by neurons
Hypothalamic-hypophyseal tract
Involved in water retention
Targets kidney tubules to reabsorb more water to inhibit or prevent urine formation
Inhibited by alcohol, diuretics
Hyper: Syndrome of inappropriate ADH; water retention, headache, disorientation
Hypo: Diabetes insipidus; High urine output/dehydration
Antidiuretic hormone (ADH)
Strong stimulant of uterine contractions
Hormonal trigger for milk ejection
Involved in ejaculation, sperm transport, sexual affection, and mother-infant bonding
Oxytocin
- Hypothalamic neurons synthesize OT and ADH
- OT and ADH transport down axons of h-h tract to the posterior pituitary
- OT and ADH are stored in axon terminals in posterior pituitary
- Associated hypothalamic neurons fire, action potentials arrive at terminal, OT and ADH released into blood
Release of OT and ADH
How anterior pituitary is connected to the hypothalamus via blood vessels
Hypophyseal portal system
Regulate secretion of other hormones; a.k.a tropins
Tropic hormones
Has direct action on metabolism and indirect effect on growth
Aka somatotropin (produced by somatotropic cells)
Hypothalamus hormones that regulate it: GHRH, GHIH
Growth hormone (GH)
Hypersecretion caused by anterior pituitary tumor
Children: Gigantism
Adults: overgrowth in hands and feet (Acromegaly)
*removal of tumor
Hyposecretion
Children: Pituitary dwarfism
Adults: No problems
*GH replacement therapy
Growth hormone (GH)
Stimulates development and secretory activity of the thyroid
Decrease in levels of TH stimulate release of TSH
Increase in TH provide negative feedback inhibition of TSH
Thyroid-stimulating hormone (TSH)
Overcomes negative feedback during pregnancy or exposure to cold, especially in infants
Leads to release of TSH and TH
Thyrotropin-releasing hormone (TRH)
Stimulates adrenal cortex to release corticosteroids
Triggered by corticotropin-releasing hormone (CRH)
Fever, hypoglycemia, stress alter release of CRH
Adrenocorticotropic hormone (ACTH)
FSH and LH
Secreted by gonadotropic cells of anterior pituitary
FSH: Stimulates production of gametes (egg/sperm)
LH: Promotes production of gonadal hormones (ovulation/testosterone)
Triggered by gonadotropin-releasing hormone (GnRH)
Gonadotropins
Stimulates milk production in females; role in males not understood
Regulated by prolactin-inhibiting hormone (PIH;dopamine)
Blood levels rise dramatically toward end of pregnancy to trigger milk production
Infant suckling stimulates PRL release to promote continued milk production
Prolactin (PRL)
Hypersecretion common
Hyposecretion: Interfere with breastfeeding
Prolactin (PRL)
Most frequent abnormality of anterior pituitary tumors
Symptoms: inappropriate lactation, lack of menses, infertility in females, impotence in males
Hyperprolactinemia
