the hypothalamus and pituitary gland

latrogenic

(physician-caused) hypercortisolism: occurs secondary to cortisol for some other condition. One of the most common

thyroid stimulating hormone (TSH)

) induces the thyroid to secrete thyroxine and triiodothyronine

the anterior pituitary secretes

6 characteristic peptide hormones

ACTH processing

ACTH is synthesized in the anterior pituitary from the larger POMC (pro-opiomelanocortin) protein Proteolysis of POMC yields several bioactive peptides, including beta endorphin, an endogenous opioid that binds to receptors that block pain reception ACTH cleaves and alpha MSH breaks off, which influences melanin synthesis, suppresses immunse response, and lowers food intake While we focused on role of ACTH, some of the other products make other hormones. These other hormones have other roles that enhance the flight or fight response.

adrenal insufficiency is associated with

Adrenal insufficiency is associated with decreased ability to maintain blood pressure (due to loss of aldosterone) and blood sugar. It may be fatal if left untreated.

hypercortisolism and organic metabolism

All of the effects of elevated cortisol levels upon organic metabolism serve to mobilize energy stores. Hypercorticalism can have manifestation of diabetes because high glucose levels. Good to mobilize this energy in fight or flight. Stimulation of protein catabolism in bone, lymph, muscle, and elsewhere Stimulation of liver uptake of amino acids and their conversion to glucose (gluconeogenesis) Maintenance of plasma glucose levels Stimulation of triglyceride catabolism in adipose tissue, with release of glycerol and fatty acids into the blood

CRH

CRH stimulates ACTH. In the adrenal cortex, cortisol is secreted

possible causes of hypercortisolism

Chronic stress and most commonly when medications is used incorrectly to suppress the immunoresponse like to bee sting. Doctors give relatively high dose through Zpacks. Need to gently taper the amount of synthetic cortisol you're receiving. But if you have prolonged treatment of high doses of cortisol these things result.

chronic stress

Chronic stress may not be life threatening but rather an individual that is constantly berating you—not instanteous response but rather longer term chronic stress Long term stress can come at you in an enormously different stimuli. ACTH is going to be regulated by production from hypothalamic neurons—hypothalamus can get inputs from many of these different stimuli and inappropriately activate ACTH production too much

increased cortisol and vascular contraction

Cortisol increases the ability of vascular smooth muscle to contract in response to norepinephrine. Vascular contraction can result in higher blood pressure because you have more vasoconstriction. Makes sense at time so that you can utilize the muscles. Brocial dilation also occurs which can improve breathing—good for allergic reactions.

cortisol effects on non-stress conditions hypoglycemia

Cortisol is an effector hormone—high production of low levels of when you're awake to produce desired important effects that don't involve stress. The most important metabolic effect of cortisol is protection against hypoglycemia (low blood sugar). When blood glucose levels drop, the pancreas secretes glucagon to promote gluconeogenesis and glycogen breakdown In the absence of cortisol, glucagon is unable to respond adequately to a hypoglycemic challenge Cortisol has a permissive effect on glucagon and catecholamine activity aka need cortisol to help glucagon make conversion of glycogen to glucose. Cortisol is essential for life—animals whose adrenal glands have been removed die if exposed to any significant environmental stress

cortisol

Cortisol is an example of a steroid hormone Secreted from the adrenal cortex, often referred to as the body's stress hormone as cortisol plays a direct role in the mediation of long term (chronic) stress Lipid soluble, receptors are predominantly found intracellularly, Once bound the receptor complex can move into the nucleus and regulate gene transcription

cortisol pathologies

Cortisol pathologies can result from too much or too little hormone. Usually not a problem with receiving cells but rather with producing cells aka how much is actually being produced The most common HPA pathologies result from hormone deficiency (for example, hypocortisolism) and hormone excess (for example. Hypercortiolism, also called Cushing's syndrome). Abnormal tissue responsiveness is an uncommon cause of adrenal steroid disorders

cortisol and immune system

Cortisol suppresses the immune system through multiple pathways Cortisol prevents cytokine release and antibody production by white blood cells Cortisol inhibits the inflammatory response by decreasing leukocyte mobility and migration Consequently, cortisol had been used as an anti-inflammatory drug for treating a variety of conditions that range from bee stings and pollen allergies to the prevention of rejection of transplanted organs

cushing's syndrome

Cushing's syndrome is the result of chronically elevated plasma cortisol concentration. It is associated with hypertension, high blood sugar, redistribution of body fat, obesity, and muscle/bone weakness. If untreated it can also lead to immunosuppression

DA

DA inhibits Prolactin production In breasts, this results in the development of milk products (in the male may facilitate reproductionive function)

symptoms of hypercorticolism

Excess gluconeogenesis causes hyperglycemia, which mimics diabetes. Good to mobilize this energy in fight or flight but not in day to day life. Muscle protein breakdown and lipolysis cause tissue wasting—a characteristic feature of individuals with hypercortisolism is thin arms and legs Paradoxically, excess cortisol deposits extra fat in the trunk and face, perhaps in part due to increased appetite and food intake Striations result from protein breakdown in the skin, Converting porteins in skin back to sugar Increased appetite because of hypercortisol—binge eat because they feel stressed. But will have thin arms and legs

growth hormone is an exception

GH is exception because it does directly target tissues as well as stimulating other endocrine organs

GHRH

GHRH stimulates Growth Hormone. Somatostatin inhibits Growth Hormone. Growth hormone action on liver and other cells: secrete IGF-1. GH action on many organs and tissues: protein synthesis, carbohydrates and lipid metabolism

GnRH

GnRH stimulates FSH and LH. In the gonads, this results in germ cell development (female=ovum and male=sperm). It also causes the secretion of hormones (females=estradiol and progesterone male=tertosterone). These hormones then act on germ cells of the gonads

hormonal feedback control

Hormonal Feedback control of the hypothalamus and anterior pituitary gland Each of the hormonal sequences initiated by a hypophysiotropic hormone feature negative feedback exerted upon the hypothalamopituitary system by one or more of the hormones in its sequence includes both long and short feedback loops This is why nature has evolved this complex pathway—gives fine tuning to these hormones that have very important physiological effects on the body—growth and devo, fight or flight, etc.

action of anterior pituitary hormones in general

In general, hormones produced by anterior pituitary do not have direct effects on target tissue of eventual action—instead, these travel to other endocrine structure organs to potentially cause the secretion of other signals that will then cause the eventual downstream effect

summary of results of increased plasma cortisol levels

In response to stress, the usual physiological functions of cortisol are enhanced as cortisol concentrations in the plasma increase. Thus, gluconeogenesis, lipolysis, and inhibition of insulin actions increase. This results in increased blood concentrations of energy sources (glucose, fatty acids) required to cope with stressful conditions High cortisol concentrations also inhibit "nonessential" processes such as reproduction, during stressful situations and inhibit immune function

oxytocin

In women, oxytocin is involved in two reflexes. These two functions are similar. Men do not produce much oxytocin In response to stimulation of the nipples during nursing, sensory information is sent to the brain resulting in activation of the paraventricular nuclei. The released oxytocin stimulates ejection of milk from the mammary glands During labor, stretch receptors in the certix send signals back to the brain and hypothalamus which releases oxytocin. Oxytocin then stimulates the contraction of uterine smooth muscle cells until birth. This is an example of a positive feedback loop. posterior pituitary hormone

increased cortisol and nonessential functions

Inhibition of nonessential functions (ex- reproduction and growth)

increased cortisol and immune response

May serve as a mechanism to protect against excessive inflammation

hypothalamic-hypophyseal portals system

Neurohormones from the hypothalamus reach the anterior pituitary through a specialized circulatory region called the hypothalamic-hypophyseal portal system How this works: 1. Neurons synthesizing trophic hormones release them into the capillaries of the portal system 2. Portal vessels carry the trophic hormones directly to the anterior pituitary 3. Endocrine cells release their hormones into the second set of cappilaries for distribution to the rest of the body This system is essential for them to get to the anterior pituitary. Enter the blood ystem and travel through the portal system to the anterior pituitary where the diffuse and receptors in anterior pituitary are activated and hormone production begins Why do we want these releasing into the capillaries instead of just into the blood directly? The endocrine cells in the anterior pituitary summate all of the signals they are receiving both from the brain and other hormones being produced by different target cells—fine control

neurohormones

Neurohormones: hormones produced by specialized nerve cells and are secreted into circulation. In the example in the picture, the neurohormones are synthesized by two clusters of neuronal cell bodies in the hypothalamus

neurons produce...

Neurons in the brain do mostly make neurotransmitters but neurosecretory neurons (produced by specialized nerve cells) make hormones that are secreted directly into the blood stream

neurosecretory cells

Neurosecretory cells—secrete hormones directly into the vascular system. Not secretory cells in posterior pituitary, they are up in the hypothalamus

nucleus

Nucleus: any cluster of nerve cell bodies in the central nervous system is called a nucleus The nuclei that create the hormone are actually in the nuclei of the hypothalamus itself. These nuclei send projections directly intot he vasculature of the posterior pituitary

plasma levels of different hormones..

Plasma levels of different hormones can help give clues to what is wrong

Addison's disease

Primary adrenal insufficiency, also known as Addison's disease, results from the autoimmune destruction of the adrenal cortex Addison's disease results in the hyposeretion of all adrenal steroid hormones including aldosterone, resulting in an imbalance in Na, K, and water in the blood possibly leading to hypotension (low blood pressure) A characteristic of Addison's disease is the elevation of serum ACTH levels due to the loss of negative feedback by cortisol

milk ejection reflex

Prolactin is an anterior pituitary hormone involved in milk production Oxytocin is a posterior pituitary hormone involved in control of milk ejection via smooth muscle contraction. There are mechanoreceptors in the nipple that help modulate this. this there are things in the body that require the input of both posterior and anterior hormones

release of growth hormone is under the control of...

Release of growth hormone is under dual control of stimulatory GHRH and inhibitory SS. Release of other anterior pituitary may also be dependent upon exposure to relative amounts of hypothalamic hormones

signs of hypercortisolism

Signs of hypercortisolism: hyperglycemic. This would be viewed as diabetic also but with normal production of insulin. High blood pressure potentially because they are more sensitive to changes in catecholamines. Weak immune response because immunosuppressant.

sequence of hypophysiotropic hormones

Stimulus Hypothalamus increase in hormone 1 secretion Increase in hormone 1 plasma concentration (in hypothalamo0pituitary portal vessels) Increase in hormone 2 secretion in the anterior pituitary Increase in hormone 2 plasma concentration Increase in hormone 3 secretion in the third endocrine gland Increase in hormone 3 plasma concentration Target cells of hormone 3 respond to hormone 3 Example resulting in growth

TRH

TRH stimulates TSH. In thyroid this causes the secretion of thyroxine and triiodothyronine

the effects of increased plasma cortisol...

The effects of increased plasma cortisol concentration are part of an adaptive response to a stressful event but are maladaptive in response to chronic stress.

growth hormone pathway

The hypothalamus is stimulated in produces GHRH. The GH cells in anterior pituitary are produced. The liver then produces IGFs (insulin like growth factor). This targets bone and soft tissue to begin growth

the hypothalamus

The hypothalamus is the most important control area for homeostatic regulation of the internal environment Together the hypothalamus and pituitary gland function to regulate virtually every body system. The hypothalamus lies under the thalamus on the underside of the brain. Behaviors having to do with the preservation of the individual (for example eating and drinking) and preservation of the species (reproduction) At the base of the cerebral hemispheres Considered to be a master control center of the endocrine system

paraventricular

The paraventricular nuclei extend axons to the posterior pituitary and synthesize the neurohormone oxytocin

cortisol and blood pressure

The permissive action on reactivity to catecholamines by cortisol also affects blood pressure. Cortisol has permissive action on the reactivity to catecholamines by smooth muscle cells that surround arterioles. As a result basal levels of cortisol help to maintain normal blood pressure. Cells can now respond more effectively to stimulation by catecholamines because of cortisol. Includes norepinephrine and epinephrine

sensitivity of target cells to...

The physiological functions of cortisol are to maintain the responsiveness of target cells to epinephrine and norepinephrine to provide a check on the immune system and to participate in energy homeostasis

infundibulum

The pituitary gland is connected to the hypothalamus by the infundibulum or pituitary stalk, containing axons from neurons in the hypothalamus and small blood vessels. The axons run to the posterior pituitary gland.

The supraoptic nuclei

The supraoptic nuclei extend axons down the infundibulum to the posterior pituitary and synthesize the neurohormone vasopressin. This is located above where the optic tract enters the brain

stress

The term stress as used in biology has been defined as any change in the environment that changes or threatens to change an existing optimal state. This differs from our traditional way of thinking about stress Most, if not all, of these stresses activate processes at the molecular, cellular, or systemic level that tend to restore the previous state that is they are homeostatic reactions This is simultaneously a good thing and a bad thing Stress refers to an environmental change that must be adapted to if health and life are to be maintained Need to activate stress response to get away from life threatening predator

posterior pituitary hormones

The two posterior pituitary neurohormones are composed of nine amino acids each oxytocin and vasopressin

naming the hypophysiotropic hormones

There are distinct endocrine cells in the anterior pituitary that are producing these different hormones- not just one type of cell doing it all Seceral hypophysiotropic hormones are named for the anterior pituitary gland hormone whose secretion they control For example. Corticotropin-releasing hormone (CRH) and growth hormone releasing hormone (GHRH) stimulate the release of corticotropin (ACTH) and growth hormone (GH)

structure of the anterior pituitary gland and influenced by

This is a true endocrine gland unlike the posterior pituitary gland--- this is because there are endocrine cells in the gland itself Several hypothalamic nuclei send axons whose terminals end in the median eminence The hypothalamic hormones that regulate anterior pituitary gland functions are called hypophysiotropic horomes and hypothalamic inhibiting/releasing hormones Note that non-hypothalamic hormones also influence the anterior pituitary gland (including some involved in feedback inhibition). This is an example of hormones influencing the production of other hormones Cardiovascular system is why there are non-hypothalamic hormones influencing. Blood from the rest of the body has hormones being produced by the rest of the body and can also influence. Critical because involved in some feedback inhibition mechanisms to prevent overproduction

the pituitary gland

This is actually two glands with different embryological origins that fused during development The pituitary gland sits in a protected pocket of bone, connected to the base of the brain just under the hypothalamus by a thin stalk. The anterior pituitary gland is a true endocrine gland of epithelial origin The posterior pituitary gland is not a gland but rather an extension of the neural components of hypothalamus. Really an extensive of the brain.

posterior pituitary

This is an extension of the brain that secretes neurohormes made in the hypothalamus

inhibiting hypophysiotropic hormones

Two of the hypophysiotropic hormones inhibit, release of anterior pituitary hormones, including somatostatin (SS) and dopamine Negative hormones= inhibitory

vasopressin

Vasopressin (also called antidiuretic hormone ADH) acts on the kidneys to regulate water balance in the body. Vasopressin is more equivalently produced in males and females. posterior pituitary hormone

vasopressin and oxytocin storage

Vassopressin and oxytocin are stored and released by the posterior pituitary gland. They can be stored in the distal tip of the posterior pituitary because they are small peptides rather than steroids so they will not just diffuse out Steps of production: 1. Neurohormone is made and packaged in cell body of neuron 2. Vesicles are transported down long extensions of the neurons called axons 3. Vesicles containing neurohormone are sotred in the axon terminal where they wait for a release signal. Not a presynaptic axon tip because doesn't synapse onto another neuron 4. When a signal (in the form of an action potential) passes down the neuron, the neurohormones are released into the interstitial space where they then can easily diffuse into the blood

beta endorphin

an endogenous opioid that binds to receptors that block pain reception

FLAT PiG

anterior pituitary production hormone mnenomic FLAT only has tropic hormones which are hormones that stimulate other endocrine glands PiG stimulates another part of the body directly. "Direct Actin hormones" Exception is growth hormone because it does both. This is what athletes use to get big

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

are gonadatropic hormones that stimulate the gonads

secondary hypercorticolism

caused by a pituitary tumor that autonomously secretes ACTH. The tumor does not respond to negative feedback. Can make ACTh under no feedback control

primary hypercortisolism

caused by adrenal tumor that autonomously secretes cortisol—these tumors are not under the control of pituitary ACTH. Production of cortisol within any of its normal controls.

alpha MSH

cleaved during ACTH synthesis which influences melanin synthesis, suppresses immunse response, and lowers food intake

prolactin

controls milk production in the breast

sphenoid bone

located around the pituitary gland

hypothalamic pituitary adernal pathway

pathway for cortisol secretion The control pathway for cortisol secretion is known as the hypothalamic-pituitary-adrenal (HPA) pathway The HPA pathway beings with hypothalamic corticotropin-releasing hormone (CRH) being secreted into the hypothalamic-hypophseal portal system CRH stimulates the release of adrenocorticotropic hormone (ACTH or corticotrophin) from the anterior pituitary. CRH is also mediated by the circadian rhytm (regulates the sleep wake cycle). This is because you need cortisol when you wak up because it affects your metabolism when you're awake). CRH is also modulated by other stressors. ACTH acts on the adrenal cortex to promote synthesis and release of cortisol. Cortisol then acts as a negative feedback signal, inhibiting ACTH and CRH. Cortisol doesn't have a strong preference for inhibiting ACTH vs. CRH

short feedback loop

pituitary hormones feed back to decrease hormone secretion by the hypothalamus

common causes of hypercortisolism

primary, secondary, and latrogenic

andrencorticotropic hormone (ACTH)

stimulates the adrenal cortex to secrete cortisol

growth hormone (GH)

stimulates the liver to secrete the growth promoting hormone, insulin-like growth factors

long feedback loop

the last hormone in a pathway feeds back to suppress the secretion of hormones by the hypothalamus and the anterior pituitary gland

surgical access to pituitary gland

up your nose