Lecture 2 endocrine control by the hypothalamus and pituitary Flashcards
hypothalamus
Located in the diencephalon of the brain, below the thalamus, and above the brainstem. Is what is connecting the brain to the endocrine system through the pituitary gland.
describe the location and anatomical relationship of the anterior pituitary
Is located in the Sella turcica of the sphenoid bone, and is just below the hypothalamus, is not directly a part of the hypothalamus. Is larger than the posterior.
- Secretes growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, prolactin, and follicle-stimulating hormone.
describe the location and anatomical relationship of the posterior pituitary
Is located in the Sella turcica of the sphenoid bone, and is beneath the anterior pituitary, but is completely connected to the hypothalamus by the hypothalamic-hypophyseal portal system
- Primarily releases oxytocin, and antidiuretic hormone (ADH)
describe the location and anatomical relationship of the hypothalamic-hypophyseal portal system
A specialized network of blood vessels that connects the hypothalamus to the anterior pituitary which is located within the infundibulum.
- The portal system allows for effective and efficient communication between the hypothalamus and the anterior pituitary. The neurons axon in the hypothalamus passes through this to send things to the posterior pituitary.
thyrotropin releasing hormone (TRH)
Thyrotropin releasing hormone (TRH) – is produced by the hypothalamus which stimulates the anterior pituitary to release thyroid stimulating hormone (TSH)
- TSH – travels to the thyroid gland to trigger production or regulation of hormones in the body, important in metabolism.
- Goes to the thyroid gland to trigger hormone production
Gonadotropin releasing hormone (GnRH)
Gonadotropin releasing hormone (GnRH) – this hormone goes from the hypothalamus into the anterior pituitary to cause the release of follicle stimulating hormone (FSH) which triggers growth of ovarian follicles and secretion of estrogen, stimulates sperm production, and luteinizing hormone (LH) which triggers ovulation and release of estrogen and progesterone, and simulates testosterone production in the testes.
growth hormone (GH)
Growth hormone-releasing hormone (GHRH) and Growth hormone-inhibiting hormone (GHIH) – one of them inhibits and the other stimulates the release of the growth hormone from the anterior pituitary gland. The inhibiting and releasing comes from the hypothalamus.
- Leads to the growth hormone being released and stimulating growth, reproduction and regeneration, metabolic functioning, and linear growth in children.
corticotropin releasing hormone (CRH)
Corticotropin-releasing hormone (CRH) – CRH is secreted by the hypothalamus and sent to the anterior pituitary where it stimulates the release of Adrenocorticotropic hormone (ACTH)
- ACTH stimulates the adrenal cortex to produce and release cortisol (stress hormone), helps regulate metabolism, immune function, and inflammation.
prolactin releasing hormone (PRH)
Prolactin releasing hormone (PRH) and Prolactin inhibiting hormone (PIH) – these start in the hypothalamus and one inhibits while the other stimulates the release of prolactin from the anterior pituitary
- Prolactin – goes to the mammary glands to produce and ejaculate milk
Name the two hormones produced by the hypothalamus that are stored in the posterior pituitary, and the hormones primary targets and effects.
oxytocin
antidiuretic hormone
oxytocin
Starts in the hypothalamus and is then taken to the posterior pituitary, which carries it through the blood to the uterus. The target is the uterus, and it causes uterine contractions.
antidiuretic hormone
Starts in the hypothalamus and moves to the posterior pituitary, which carries it through the blood to the kidney. The target is the kidney where it then decreases urine output.
Describe the major hypothalamic neurohormones (regulatory hormones) and their role in the release of anterior pituitary hormones. What are they?
- thyrotropin releasing hormone (TRH) - TSH (thyroid stimulating hormone)
- gonadotropin releasing hormone (GnRH) - FSH and LH (follicle stimulating hormone, luteinizing hormone)
- corticotropin releasing hormone (CRH) - stimulates ACTH (Adrenocorticotropic hormone)
- prolactin releasing hormone (PRH) - stimulates prolactin
Explain the role of the hypothalamus in the release of hormones from the posterior pituitary.
The hypothalamus plays a critical role in the release of hormones from the posterior pituitary even though it does not directly produce the hormones that are released here. The hypothalamus synthesizes the hormones that are then transported to the posterior pituitary to be stored and later released.
Compare and contrast the locations of target cell receptors for steroid and peptide hormones.
Steroid – intracellular receptors (cytoplasm or nucleus)
- Generally, a slower reaction time
Peptide – plasma membrane receptors
- Generally a faster more immediate cellular response time
mechanism of action of plasma membrane hormone receptors
Plasma membrane hormone receptors
- G protein coupled receptors (GPCRs) – these receptors interact with the G proteins, which are signal transduction molecules that can transmit signals from the cell surface to the interior of the cell
- Enzyme linked receptors – these receptors have an intrinsic enzymatic activity that is activated upon hormone binding, which can lead to the activation of the signaling pathways
- Tyrosine kinase signaling – this pathway involves the activation of tyrosine kinases, which phosphorylate and activate downstream targets.
mechanism of action of intracellular hormone receptors
Steroid hormone receptors – these receptors bind to steroid hormones and are typically transcription factors that regulate a kind of gene expression
Nuclear receptor – has the receptors for thyroid hormones
where are the receptors embedded and what do they trigger
- Intracellular hormone receptors are embedded in the cytoplasm or nucleus while plasma membrane hormone receptors are embedded in the plasma membrane.
- Plasma – bind to extracellular hormones to trigger signal transduction pathways. Intracellular – bind to intracellular hormones to regulate gene expression directly or indirectly
Describe major hormones secreted by the anterior pituitary, their control pathways, and their primary target(s) and effects. - growth hormone
Growth hormone (GH, somatotropin)
- Stimulated by the growth hormone releasing hormone from the hypothalamus and is inhibited by somatostatin from the hypothalamus.
- Primary target is the liver, which will stimulate the liver to release insulin-like growth factor
Describe major hormones secreted by the anterior pituitary, their control pathways, and their primary target(s) and effects. - thyroid stimulating hormone
Thyroid stimulating hormone (TSH, thyrotropin)
- Stimulated by thyrotropin releasing hormone from the hypothalamus, and inhibited by the negative feedback given from thyroid hormones
- Primary target is the thyroid gland, it stimulates the thyroid gland to produce and release thyroid hormones which regulate metabolism
Describe major hormones secreted by the anterior pituitary, their control pathways, and their primary target(s) and effects. - adrenocorticotropic hormone
Adrenocorticotropic hormone (ACTH, corticotropin)
- Stimulated by the corticotropin releasing hormones from the hypothalamus, and is inhibited by negative feedback from cortisol. The primary target is the adrenal cortex.
Describe major hormones secreted by the anterior pituitary, their control pathways, and their primary target(s) and effects. - follicle stimulating hormone
Follicle stimulating hormone (FSH)
- Stimulated by gonadotropin-releasing hormone (GnRH) from the hypothalamus, and inhibited by the negative feedback from estrogen and testosterone. The primary target is the ovaries and the testes.
Describe major hormones secreted by the anterior pituitary, their control pathways, and their primary target(s) and effects. - luteinizing hormone
Luteinizing hormone (LH)
- Stimulated by gonadotropin-releasing hormone (GnRH) from the hypothalamus, and inhibited by the negative feedback from estrogen and progesterone or testosterone. The primary target is the ovaries and the testes.
Describe major hormones secreted by the anterior pituitary, their control pathways, and their primary target(s) and effects. - prolactin
Prolactin (PRL)
- Stimulated by prolactin releasing hormone (PRH) from the hypothalamus and inhibited by dopamine from the hypothalamus. The primary target is the mammary glands in women
