A&P Endocrine System: Hypothalamus & Pituitary Gland
When is GH at peak secretion?
During: Sleep Exercise Fasting
What disease occurs when there are ↓ GH levels?
Dwarfism
Make a list all the endocrine hormones involved w FSH & LH, starting from the hypothalamus & ending w the hormone released from the target organ. Include their functions.
Hypothalamus releases Gonadotropin-releasing hormone (GnRH) Pituitary Gland releases 2 hormones: Follicle stimulating hormone FSH - stims ovarian follicle development in females - in combo w LH it stims estrogen - ovaries secrete inhibin & estrogens - sperm cell production in the testes - testes secrete inhibin Lutenizing hormones (LH) - Stims ovulation & estrogen/progesterone production; maintains pregnancy in female gonads - Stims androgen production including testosterone in male gonads
Make a list all the endocrine hormones involved w GH, starting from the hypothalamus & ending w the hormone released from the target organ.
Hypothalamus: Growth hormone-releasing hormone (GH-RH) Growth hormone-inhibiting hormone (GH-IH) A. Pituitary: Releases growth hormone (GH) Target: Cell metabolism Increase protein synthesis & fat breakdown Stimulate bone & muscle growth
What is releasing hormone? How is it secreted?
secreted into the hypophyseal portal from the hypothalmus, interact w the endocrine cells of the anterior pituitary to cause the release of one or more hormones from the anterior pituitary.
Define the hypophyseal portal system
the network of vessels that carry blood from capillaries in the hypothalamus to capillaries in the anterior lobe of the pituitary gland
Any hormone secreted by the hypothalamus is named a ...
(name)-releasing hormone
What is the function of LH?
- Stims ovulation & estrogen/progesterone production; maintains pregnancy in female gonads - Stims androgen production including testosterone
What is the function of FSH?
- stims ovarian follicle development in females (in combo w LH it stims estrogen) - sperm cell production in the testes
What are the 3 ways the hypothalamus regulates the endocrine system?
1. Secretes regulatory hormones to control anterior pituitary 2. Neurons produce hormones (Antidiuretic Hormone (ADH / Vasopressin) & Oxytocin); both are stored & released by the posterior pituitary 3. Controls sympathetic nervous system to release adrenaline from adrenal medulla
Identify the 3 mechanisms by which the hypothalamus integrates neural & endocrine function.
1. secretion of ADH (antidiuretic hormone) & OXT (oxytocin) 2. secretion of regulatory hormones that control activity of the A. lobe of the pituitary gland 3. neural (sympathetic) control over the endocrine cells of the adrenal medullae
What are the hormones of the posterior pituitary?
ADH (vasopressin) and OXT
Identify 9 pituitary hormones and their target tissues.
ANTERIOR PITUITARY LOBE 1. Thyroid stimulating hormone (TSH) - targets thyroid gland 2. Adrenocorticotropic hormone (ACTH) -targets adrenal cortex 3. Follicle-stimulating hormone (FH) - targets testes/ovaries 4. Luteinizing hormone (LH) - targets testes/ovaries 5. Growth hormone (GH) - targets liver cells (synthesize somatomedins in response) 6. Prolactin (PRL) - targets mammary glands in F 7. Melanocyte-stimulating hormone - targets melanocytes in skin POSTERIOR PITUITARY LOBE 8. Oxytocin (OXT) - targets uterus & mammary glands 9. Antidiuretic hormone (ADH) - targets kidneys
What is the size of the pituitary gland? Where is it located?
About the size of a pea Located in sella turcicia (depression in sphenoid bone)
List the hypothalamic releasing hormones.
Corticotropin-releasing hormone (CRH) Thyrotropin-releasing hormone (TRH) Growth hormone-releasing hormone (GH-RH) Prolactin-releasing hormone (PRH) Gonadotropin-releasing hormone (GnRH).
What are some examples of negative feedback in the endocrine system?
GH: Target organ (liver) releases somatomedins Somatomedins inhibit GH-RH & stimulates GH-IH PRL
What disease occurs when there are ↑ GH levels?
Gigantism (childhood/prepubescence) Acromegaly (post puberty)
Make a list all the endocrine hormones involved w PRL, starting from the hypothalamus & ending w the hormone released from the target organ.
Hypothalamus: Prolactin-releasing hormone (PRH) Prolactin-inhibiting hormone (PIH) Pituitary: Prolactin (PRL) Target Organ: Mammary gland development Milk production Maintains progesterone levels after ovulation and during pregnancy (may cause decrease in male sex hormones & increase sensitivity to LH)
Make a list all the endocrine hormones involved w TSH, starting from the hypothalamus & ending w the hormone released from the target organ.
Hypothalamus: Thyrotropin Releasing Hormone (TRH) Goes to pituitary A. Pituitary: Releases thyroid stimulating hormone Target organ: Thyroid; releases thyroid hormones
Make a list all the endocrine hormones involved w ATCH, starting from the hypothalamus & ending w the hormone released from the target organ.
Hypothalamus: releasees cortiocotropin-releasing hormone (CRH) A. Pituitary releases Adrenocorticotropic Hormone (ATCH) Target organ adrenal cortex steroid hormone regulates glucose metabolism & inflammation
Make a list all the endocrine hormones involved w MSH, starting from the hypothalamus & ending w the hormone released from the target organ.
Hypothalamus: unknown Pituitary: Melanocyte stimulating hormone (MSH) Target Organ: Stimulates melanin production in melanocytes
Make a list all the endocrine hormones involved w ADH, starting from the hypothalamus & ending w the hormone released from the target organ.
Hypothalamus: neurons make hormone Pituitary: hormones stored & released Antidiuretic hormone (ADH) / Vasopressin - Maintain water balance by increasing water reabsorption in kidneys
Make a list all the endocrine hormones involved w OXT, starting from the hypothalamus & ending w the hormone released from the target organ.
Hypothalamus: neurons make hormone Pituitary: hormones stored & released Oxytocin OXT - Stims contractions of uterine smooth muscle & mammary cells - Associated w sexual activity for both sexes
What is the benefit of negative feedback in the endocrine system?
If inhibiting hormones from hypothalamus are stimulated, this allows for finer regulation
What feedback mechanism controls the secretion rates of the hypothalamus & pituitary gland? What does this feedback mechanism consist of?
Negative Feedback End product of pathways goes & turns off the signaling
What travels through the hypophyseal portal system?
Neurosecretions (releasing/inhibiting hormones) travel via the hypophyseal portal system through the infundibulum to the anterior pituitary
What are the hormones of the anterior pituitary?
TSH ACTH Gonadotropins (FSH & LH) GH PRL MSH
Name the 2 lobes of the pituitary gland. What is each made up of?
anterior (adenohypophysis) - glandular epithelium posterior (neurohypophysis) - neurofibers / neuroglia cells
What are osmoreceptors?
detect change in osmotic pressure of body fluids stimulate the neurosecretory neurons that release ADH
What happens when you have too little ADH?
diabetes insipidus (20-30 L urine produced) dehydration & disrupted muscle /nerve signaling
Define regulatory hormone.
hormone secreted by the hypothalamus that controls endocrine cells in the anterior lobe of the pituitary gland.
What is another name for the pituitary gland?
hypophysis
What brain structure provides the highest level of control by integrating the activities of the nervous system & endocrine system?
hypothalamus
What happens when you have too much ADH?
increase BP & constriction of vessels
What synthesizes and releases NTs?
neurons
What is inhibiting hormone?
prevents the synthesis and secretion of hormones from the anterior lobe
Name and describe the characteristics and functions of BVs that link the hypothalamus w the anterior lobe of the pituitary gland.
unusually permeable fenestrated capillary beds in each structure are cxted by portal vessels this arrangement ensures that hypothalamic regulatory hormones reach the "downstream" endocrine cells of the A. lobe directly before mixing w & being diluted by the general circulation
In a dehydrated person, how would the amount of ADH released by the posterior lobe of the pituitary change?
↑ ADH released in response to ↑ blood osmotic pressure resulting from a rise in solute concentration
The release of which pituitary hormone would lead to an increased level of somatomedins in the blood?
↑ GH levels
What effects would increased circulating levels of glucocorticoids have on the pituitary secretion of ACTH?
↑ed circulating levels of glucocorticoids inhibit the release of Corticotropin-releasing hormone (CRH) by the thalamus lack of CRH = ↓ ATCH secretion from the pituitary gland ATCH levels would ↓
