(1) Hypothalamus and Pituitary

The hypothalamus and pituitary is the —- center of the endocrine system

main control center

hypothalamus

part of the CNS. almond-sized region at the base of the brain that regulates body temperature, hunger, and hormone release. Connected to the pituitary by the infundibulum

The pituitary is connected to the hypothalamus by the —-

infundibulum

Pituitary gland

small, pea-sized gland located at the base of your brain below the hypothalamus. It sits in its own little chamber under the brain known as the sella turcica. The pituitary gland is divided into two main sections

Posterior vs anterior pituitary

posterior is composed of nervous tissue and anterior is composed of epithelial cells.

Describe the tissue composition of hypothalamus, posterior pituitary and anterior pituitary

hypothalamus is composed of CNS tissue, posterior pituitary is composed of nervous tissue (not CNS) and anterior is composed of epithelial cells

What part of the skull does the pituitary sit in?

sella turcica (or pituitary fossa)

Endocrine signaling pathway

signaling molecules travel throughout the body

Paracrine signaling pathway

signaling molecules act on neighbouring or nearby cells

Autocrine signaling pathway

signaling molecules act on the cell that secretes it (acts on itself). Seen mainly in negative feedback.

Neuroendocrine signaling pathway

endocrine (signaling molecules that travel throughout the body) hormone produced in the central nervous system

Protein and peptide hormones

examples include growth hormone and ACTH. Synthesized as a preprohormone. Stored in secretory vesicles; Rise in intracellular Ca2+ is required for exocytosis

Amines (hormone type)

derived from tyrosine. Unlike protein hormones, amines are not synthesized as a preprohormone and not stored long term. They are made as needed. Examples include catecholamines and thyroid hormones.

Steroids(hormone type)

derived from cholesterol. Synthesized in cytoplasm and mitochondria; also not stored. Examples include cortisol and testosterone

Show the pathway of how protein/peptide hormones are produced, processed then secreted

note that calcium is key to secretion and parallels in increase to cAMP

peptide/protein receptors mostly bind to what type of receptor?

G-protein coupled receptors

Hormones exert their effects through binding to various types of —-

receptors

Gq

type of G-alpha subunit that activates phospholipase C-beta

T/f, when the GPCR is actuated, G-beta/gamma may transduce the signal

true, both it and G-alpha can transduce signals

G proteins are classified based on their —

G-alpha subunits

Gs

type of G-alpha subunit. stimulatory, activates adenylyl cyclase when active. Increases cAMP production and Ca2+ in cell

Gi

type of G-alpha subunit. inhibitory, inhibits adenylyl cyclase when active. Decreases cAMP production and Ca2+ in cell

Gq

type of G-alpha subunit. causes rise in intracellular calcium via release of calcium from intracellular stores (golgi/ER). Activates PKC which can turn on action of proteins/enzymes

How are insulin receptors different from other receptors?

there are intrinsic tyrosine kinases that start a lot of phosphorylation events

All steroid hormones are produced from —

cholesterol

Steroid hormones are released via —-

passive diffusion

Steroid hormones are located where?

intracellular (nuclear receptors that are transcription factors

How are steroid hormones transported in blood

by being bound to a protein

Show the endocrine axis-driven negative feedback loop

hypothalamus secreted releasing hormone that acts on the pituitary which then releases a tropic hormone to act on a peripheral endocrine gland which releases a hormone. This hormone acts on target organs as well as inhibit the hypothalamus and pituitary

Show the physiological response driven negative feedback loop using blood glucose as an example

as blood glucose lowers, glucagon is released to raise it and when more glucose is in the blood stream, glucagon release from the pancreas is inhibited

Short loop negative feedback is from — to —-

pituitary to hypothalamus

Long loop negative feedback is from —- to —-

peripheral endocrine gland and back to pituitary or hypothalamus( or both)

Median eminence

the middle of the pituitary stalks where neurosecretary cells of the hypothalamus end and releasing hormones are secreted. These hormones are picked up by the Hypothalamohypophyseal portal system

Hypothalamohypophyseal portal system

a network of blood vessels that directly connects the hypothalamus to the anterior pituitary gland. This is how releasing hormones from neurosecretory cells of the hypothalamus is released into the anterior pituitary (starting at the median eminence).

Lactotropes

cell type in the anterior pituitary. Release prolactin.

Thyroid tropes

cell type in the anterior pituitary. Release thyroid stimulating hormone.

Gonadotropes

cell type in the anterior pituitary. Release Luteinizing hormone and follicle stimulating hormone.

Corticotropes

cell type in the anterior pituitary. Release ACTH which act on adrenal glands

Somatotropes

cell type in the anterior pituitary. Release Growth hormone which affects both linear growth and blood glucose

Hypothalamic Releasing hormones

produced by neural cells in the hypothalamus. Act on cells in the anterior pituitary and are secreted in pulses. Stimulates synthesis and release of target anterior pituitary hormones.

What is the 1 anterior pituitary hormone that is always suppressed? How is it suppressed?

prolactin. suppressed by dopamine release by hypothalamus. Prevents everyone from lactating all the time.

Circadian rhythm

24-hour cycles that are part of the body’s internal clock, running in the background to carry out essential functions and processes. physical, mental, and behavioral changes that follow a 24-hour cycle. These natural processes respond primarily to light and dark

Suprachiasmatic nucleus

main part of the hypothalamus that control circadian rhythm

Melatonin

hormone from the pineal gland that helps prepare the body for sleep. Only works when the body is getting ready for sleep (ie when its getting darker)

Tertiary endocrine disease

disorder is caused by the hypothalamus. (over or underproduction of the releasing hormone.

Secondary endocrine disease

disorder is caused by the pituitary gland.

Primary endocrine disease

disorder within a peripheral endocrine gland.

What hormones does the posterior pituitary synthesize?

none, it's mainly a holding point for hormones released directly by the hypothalamus

Hypothalamohypophyseal track

a nerve bundle connecting the hypothalamus to the posterior pituitary gland, carrying oxytocin and antidiuretic hormone (ADH) for storage and release

2 hormones released through the posterior pituitary

ADH/vasopressin and oxytocin

Why is pulsatility of hypothalamic releasing hormones important?

it helps with receptor turnover in the anterior pituitary