Chapter 7

hormones secreted by anterior pituitary

- Prolactin - Luteinizing hormone (LH) - Thyrotropin (TSH) - Adrenocorticotropic hormone (ACTH) - Follicle stimulating hormone (FSH) - Growth hormone (GH)

Hyposecretion from damage to the pituitary will cause:

- increased CRH secretion from hypothalamus - decreased ACTH secretion from anterior pituitary - decreased cortisol secretion from adrenal cortex

Hyposecretion from atrophy of the adrenal cortex will cause:

- increased CRH secretion from hypothalamus - increased ACTH secretion from anterior pituitary - decreased cortisol secretion from adrenal cortex

Hormones and their target tissues

1) Growth Hormone (GH): muscles and bones 2) Thyrotropin (TSH): thyroid gland 3) Adrenocorticotropin (ACTH): adrenal gland 4) Luteinizing hormone (LH) and Follicle-stimulating hormone (FSH): ovary or testis 5) Prolactin (PRL): mammary gland

Thyroid hormone production and release

1) Iodine is concentrated by the thyroid gland 2) Iodine is combined with the amino acid tyrosine 3) Thyroxine and triiodothyronine are produced 4) Metabolism is regulated

stimulation of the anterior pituitary

1) Release of gonadotropin-releasing hormone (GnRH)from hypothalamic neurons 2) Gonadotropin-releasing hormone (GnRH) travels through portal system circulation 3) Stimulation of endocrine cells in anterior pituitary 4) Release of follicle-stimulating hormone (FSH) 5) Follicle-stimulating hormone (FSH) enters into general, systemic circulation 6) Follicle-stimulating hormone (FSH) binds to ovary, promoting follicular growth/development and release of estrogen

Hypothalamus

A brain region that contains several collections of neuronal cell bodies that provide a connection between the nervous system and the endocrine system

Anterior pituitary

A true endocrine gland of epithelial origin, sometimes called the adenohypophysis - stimulated by trophic hormones released by the hypothalamus - composed of endocrine tissue

Posterior pituitary

An extension of the neural tissue of the brain, sometimes referred to as the neurohypophysis - composed of neural tissue

Leptin is a hormone secreted by adipocytes. It decreases hunger and feeding behaviors. Leptin release is relative to the size of adipose cells: The greater the adipocyte size, the more leptin they release. Leptin then acts at the hypothalamus to cause the release of αMSH, an appetite suppressant. In this reflex pathway, what is the response?

Appetite suppression

A blood sample is found to have low levels of GHRH and very high levels of GH and IGFs. Where would the pathology be located in this example?

The anterior pituitary

What loss of function would occur if you were to sever the connection between the hypothalamus and the anterior pituitary?

The anterior pituitary would not release hormones in response to trophic hormone stimulation

TRH levels in a person with Graves' disease

The levels of TRH should be low because thyroid hormone is on a negative feedback loop

Mrs. Johnson goes to visit her doctor because of some health issues that she has been having. One of the tests revealed that she had no circulating concentrations of vasopressin. Further analysis of her hypothalamus and posterior pituitary were performed to see what might be causing this problem. What might explain Mrs. Johnson's condition?

The neuronal cell bodies in the hypothalamus are damaged

Infundibulum

The stalk that connects the pituitary gland to the brain - located between the pituitary gland and the hypothalamus

best solution for a drug to cure cure Graves' disease:

a drug that breaks down the antibodies produced

If TRH levels increase...

both TSH and thyroid hormone levels will increase

neurohormone

classification of the type of chemical released by the posterior pituitary that are produced in the neuronal cell bodies found in the hypothalamus - oxytocin (OXT) - vasopressin (ADH)

Which two organs of the body release hormones that lead to the release of thyroid hormone?

hypothalamus and anterior pituitary

Insulin-like growth factors (IGFs)

intermediary hormones stimulated by growth hormones (GH) - required for the growth effect of GH on bone and skin

ventral hypothalamic neuron function

neurohormones, known as releasing (RH) and inhibiting (IH) hormones, control the release/secretion of anterior pituitary hormones such as adrenocorticotropic hormone (ACTH) and thyroid stimulating hormone (TSH)

neuroendocrine ("letdown") reflex

regulates the hormone oxytocin - suckling of the infant (or stretching of the uterus) increases release of oxytocin, which causes the milk let-down effect (or increased uterine contractions)

Hypothalamus stimulation due to exercise

results in the release of most hypothalamic neurohormones which will cause increases in metabolism, energy availability, and blood volume

A new hormone is discovered. Analysis suggests that it is synthesized on demand and has a long half-life in the bloodstream. It seems to activate gene transcription in its target cells, though no cell surface receptors can be identified. Which type of hormone is this most likely to be?

steroid hormone

Basic steps of complex endocrine pathways

stimulus -> hypothalamus -> trophic hormone -> anterior pituitary -> trophic hormone -> endocrine gland -> hormone -> target tissue -> response - short-loop negative feedback from second trophic hormone to hypothalamus - long-loop negative feedback from hormone to anterior pituitary and hypothalamus

Where is antidiuretic hormone (ADH), also known as vasopressin, synthesized?

synthesized mainly in the supraoptic nucleus of the hypothalamus - stored in the posterior pituitary in axon terminals

Down Regulation

target cells lose receptors in response to high hormone levels - Example: Patients with hyperinsulinemia may have a decreased number of insulin receptors on their cell membranes

negative feedback

the most important regulatory factor controlling the circulating levels of thyroid hormone - If levels are high, negative feedback will decrease thyroid-stimulating hormone (TSH), thus decreasing the thyroid hormones

Prolactin (PRL)

the only anterior pituitary hormone that has a nonendocrine cell as its target - stimulates milk production - target tissue: mammary gland

adrenocorticotropic hormone (ACTH)

tropic hormone that stimulates the adrenal gland to produce cortisol - Stress and ACTH are the main stimuli for cortisol production