Ch.18 Endocrine System

Human Physiology

___ is a long-distance chemical mediator that is secreted by an endocrine gland into the blood, which transports it to its target cell.

hormone

___ is the chemical messenger released from axon terminals of a neuron in response to an action potential that influences another neuron or an effector with which the neuron is anatomically linked.

neurotransmitter

The endocrine system consists of the ___. They are not connected anatomically. These glands secrete hormones into the blood. A hormone travels in the blood, signaling distant target cells. (p.661-664)

ductless glands

___ neurons release neurohormones. They are also distributed by the blood to target cells.

neurosecretory

Target cells are specific for each hormone or neurohormone. It is specific, as these cells have receptors that uniquely bind to a specific ___.

chemical messenger

The endocrine system mainly controls activities that require ___ duration

longer

The endocrine system regulates organic ___ and water/electrolyte balance. It also induces adaptive changes to deal with stress. It promotes smooth, sequential growth and development

metabolism

Some hormones control reproduction while another one regulates red blood cell production. Some hormones regulate ___ and digestive functions.

circulatory

A ___ hormone is a hormone that regulates the secretions of another endocrine gland

tropic

Tropic hormones are secreted by the ___ gland.

anterior pituitary

One endocrine gland can produce ___ hormones. A single hormone can be produced by more than one endocrine gland

multiple

A single hormone can have ___ one type of target cell and, therefore, ___ one effect. A single target cell can be influenced by more than one hormone

more than

The same chemical messenger can be a hormone or neurotransmitter (e.g., ___)

norepinephrine

Some organs have exclusively endocrine functions. Other organs (e.g., ___) have endocrine functions and nonendocrine functions

testis

___ are small simple molecules that make up the thousands of proteins

amino acids

___ are hormones that consist of a chain of specific amino acids of varying length

peptides

Peptides and ___ proteins are hormones (p.118-128)

some

___ are hormones derived from the amino acid tyrosine and are secreted by the adrenal medulla. They are stored until secreted

amines

Proteins/peptides and amines are ___ (water-soluble) hormones

hydrophilic

___ hormones are hormones produced by the thyroid gland. They are an iodinated tyrosine derivative

thyroid

___ hormones are hormones produced by the adrenal cortex and reproductive endocrine glands (gonads). They are neutral lipids derived from cholesterol.

steroid

Thyroid and steroid hormones are ___ (lipid-soluble) hormones. Most ___ hormones are steroids, meaning most derive from cholesterol (precursor).

lipophilic

The mechanisms of hormone synthesis, ___, and secretion vary according to the class of hormone

storage

___ are special ribosomal RNA-protein complexes that synthesize proteins under the direction of nuclear DNA

ribosomes

Peptide hormones have precursors called ___. They are made on ribosomes of the ER. In the Golgi complex they are converted to prohormones and, finally, active hormones. The Golgi complex concentrates these hormones into secretory vesicles. These hormones are released from endocrine cells by exocytosis

preprohormones

Cholesterol is the common precursor for all steroid hormones. A series of enzymatic steps modify this molecule into a different hormone in a specific endocrine cell. Only the ___ is stored. The lipid-soluble hormone is not stored

precursor (cholesterol)

Types of actions: Autocrine (Act on the signal cell (self-stimulating)), ___ (Act locally), Endocrine (Act systemically)

paracrine

___ hormones travel by dissolving in the plasma. They bind to receptors on the surface of target cells. A few ___ hormones alter the permeability of the target cell’s membrane.

hydrophilic

Most ___ hormones are bound reversibly to plasma proteins. These hormones are released by these proteins when they actively signal target cells. ___ hormones pass through target cell membranes and bind to receptors inside the target cell.

lipophilic

Hormones generally produce their effect by altering intracellular ___.

proteins

Mechanisms of hormone control: Primary messenger system → Affects DNA directly, ___ hormone mechanism; Secondary messenger system → Amino acid based hormones, Uses G proteins and 1 or more regulatory proteins to mediate target cell response

steroid

A hydrophilic hormone (protein) usually activates ___ messenger systems

secondary

The hydrophilic hormone binds to the target cell surface. This activates an intermediate G protein. This activates ___ which converts intracellular ATP to cyclic AMP. Cyclic AMP triggers steps that alter the activity of a protein which is often an enzyme. This produces a physiological response in the target cell

adenyl cyclase

A lipophilic (steroid) hormone stimulates a gene, promoting ___ synthesis.

protein

The lipophilic hormone passes through the target cell membrane. It binds with a receptor that binds to ___. This turns on a gene. This gene makes RNA which makes a specific protein at the ribosome. This hormone changes the physiological response in the target cell.

DNA

Compared to neural activity, the action of either class of hormone is usually slow and prolonged. Hormone actions are greatly amplified at the target cell. Activation of one receptor can activate many proteins

one

Secondary messenger system (for proteins can not penetrate the plasma membrane): Cyclic AMP (mediates neurotransmitters) → Hormone (first messenger) binds to receptor → Receptor binds G-protein → G-protein binds GTP, releasing GDP (has GTPase) → Activated G-protein moves along membrane binds to Adenalyte cyclase, hydrolyzes it’s bound GTP to GDP. → cAMP generated from ATP (secondary messenger) → Cyclic AMP (cAMP) diffuses throughout cell, triggering protein kinases (enzymes). (watch video since i think it would be better visually demonstrated)

messenger

Secondary messenger system example: Epinephrine (adrenaline) on fat cell-break down ___ and fat. Phosphodiesterase (intercellular enzyme) degrades cAMP

glycogen

Draw secondary messenger system diagram (slides)

Draw secondary messenger system diagram (slides)

Missing slides 4-5 because they require reading p.118-128 to understand. Moving on for the sake of brevity

brevity

___: Increase in the number of receptors in response to high levels of circulating hormone (p.664-

up-regulation

___: Loss of the number of receptors due to prolonged exposure to high hormone levels (target desensitized)

down-regulation

The concentration of a hormone in the blood is subject to control. It varies according to ___ need

homeostatic

The availability of a hormone to its receptor depends on the hormone’s rate of secretion, its rate of metabolic activation, the extent of its binding to plasma proteins (if it is lipophilic), and its removal from the blood (Removal can be by metabolic inactivation or ___).

urinary excretion

___ maintains the plasma concentration of a hormone at a needed level. When a hormone’s concentration falls below a certain set point, the gland increases the secretion of the hormone. When the hormone’s level is above the set point, secretion decreases.

negative feedback

___ respond to specific stimuli and produce a sudden increase in hormone secretion. They have neural and hormonal components. Neural input to a gland regulates the gland’s secretion

neuroendocrine reflexes

Draw negative feedback control graphic (s & p.664)

Draw negative feedback control graphic (s & p.664)

The secretion rate of many hormones varies by a ___ (responding to day and night cycle) or circadian rhythm (internal clock regardless of perceived time or environment)

diurnal

Draw Diurnal rhythm graph (s & p.665)

Draw Diurnal rhythm graph (s & p.665)

Endocrine ___ result from the hyposecretion or hypersecretion of a hormone.

disorders

___ occurs when an endocrine gland is secreting too little of its hormone because of abnormality within that gland

primary hyposecretion

___ takes place when an endocrine gland is normal but is secreting too little hormone because of a deficiency of its tropic hormone

secondary hyposecretion

Factors producing hyposecretion include heredity, dietary deficiency, immunologic factors, and disease processes. Replacement therapy of a hormone can often successfully treat the conditions from hyposecretion.

heredity

___ occurs when an endocrine gland is secreting too little of its hormone because of abnormality within that gland. Such as tumors that ignore the normal regulatory input and continuously secrete excess hormones

primary hypersecretion

__ takes place when an endocrine gland is normal but is secreting too much of a hormone because of immunological factors, such as excessive stimulation of the thyroid gland by an abnormal antibody that mimics the actions of TSH (the thyroid tropic hormone). Also drugs.

secondary hypersecretion

Endocrine dysfunction can also arise from the unresponsiveness of target cells to a hormone.

target cells

The responsiveness of a target cell can vary by regulating the number of hormone-specific receptors. Permissiveness, synergism, and antagonism.

responsiveness

By ___ one hormone must be present in sufficient amounts for the full effect of another hormone to occur.

permissiveness

By ___ several hormones complement each other and combine effects.

synergism

By ___ causes the decrease in another hormone’s receptors and therefore diminishes the effectiveness of the other hormone

antagonism

The ___ gland is a tiny structure in the center of the brain.  It secretes the hormone melatonin and helps keep the body’s inherent circadian rhythms in synchrony with the light-dark cycle.

pineal

The ___ is the master biological clock that serves as the pacemaker for the body’s circadian (daily) rhythms. It secretes clock proteins. Cyclic changes in their concentration changes the neural output from the SCN. This can produce cyclic changes in effector organs through the day.

suprachiasmatic nucleus (SCN)

The SCN works in conjunction with the pineal gland and its hormonal product ___ to synchronize the various circadian rhythms with the 24-hour day-night cycle. Daily changes in light intensity is the major environmental cue used to adjust the SCN master clock

melatonin

Melatonin has other functions not related to circadian timekeeping. It accomplishes natural sleep without hypnosis. It inhibits hormones that stimulate reproductive activity. It is also an effective ___.

antioxidant

The ___ gland (also hypophysis) is a small endocrine gland at the base of the brain. It has two anatomically and functionally distinct lobes, the posterior ___ and the anterior ___. These lobes only share a location, they are distinct in tissue, function, and effectors. (p.670-677)

pituitary

The ___ pituitary is composed of nervous tissue and this is termed the neurohypophysis.

posterior

The ___ pituitary consists of glandular epithelial tissue and according is also called the adenohypophysis

anterior

The posterior lobe and the hypothalamus act as a unit to secrete vasopressin and ___. The axons of the hypothalamus pass from the brain into capillaries in the posterior lobe. The posterior lobe does not produce vasopressin and oxytocin. They are produced by hypothalamic neurons. They are stored in neuron terminals in the posterior lobe

oxytocin

___ (ADH) signals the kidneys to retain water. It also signals the smooth muscle in the walls of arterioles. Its main role is regulating water balance

vasopressin

The anterior pituitary (___) synthesizes and secretes six hormones. This includes the growth hormone (GH, somatotropic), thyroid-stimulating hormone (TSH, thyrotropin), adrenocorticotropic hormone (ACTH, noun form - adrenocorticotropin), follicle-stimulating hormone (FSH), Luteinizing hormone (LH), prolactin (PRL). Many are tropical.

adenohypophysis

The ___ hormone (TSH) stimulates the secretion and growth of the thyroid gland.

thyroid-stimulating

The ___ hormone (ACTH) stimulates the growth and secretion of hormones from the adrenal cortex.

adrenocorticotropic

The ___ hormone (FSH) stimulates growth and development of the ovarian follicles in females and sperm production in males.

follicle-stimulating

The ___ hormone (LH) stimulates ovulation and luteinization in females and stimulates testosterone secretion in the males.

luteinizing

___ enhances breast development in females

prolactin

Hypothalamic releasing and inhibiting hormones regulate ___ pituitary hormone secretion. (p.675)

anterior

___ stimulates the release of TSH.

TRH

___ stimulates the release of ACTH

CRH

___ stimulates the release of FSH and LH.

GnRH

___ stimulates the release of the growth hormone.

GHRH

___ inhibits the release of the growth hormone and TSH.

GHIH

___ stimulates the release of prolactin.

PRH

___ inhibits the release of prolactin.

PIH

A hypothalamic hormone controls the output of an anterior pituitary hormone. The ___ hormone regulates the secretion of the target endocrine gland’s hormone

tropic

Draw hierarchic chain of command and negative feedback in endocrine control diagram (s & p.675)

Draw hierarchic chain of command and negative feedback in endocrine control diagram (s & p.675)

The hypothalamic regulatory hormones reach the anterior pituitary by a vascular link. This is an unusual capillary to capillary connection, the ___. Blood is the system that carries hypothalamic signals to the anterior pituitary

hypothalamic-hypophyseal portal system

Regulation of the secretion of the ___ hormones depends on numerous inputs. Their complete regulation is not well understood

hypothalamic

Target gland hormones inhibit hypothalamic and anterior pituitary hormone secretion via negative feedback. For example, a rise in cortisol from the adrenal cortex can feed back and reduce ___ secretion (hypothalamus) and the sensitivity of the ACTH secreting cells (anterior pituitary) to ___. If cortisol falls in the blood, the direction of the other responses is reversed

CRH

Growth capacity is genetically determined. Adequate diet, freedom from chronic disease and stress, and normal levels of other growth-influencing hormones are other factors.

stress

The growth hormone does not play a role in fetal development. In children there is a postnatal growth spurt. The growth hormone may play a role in the later-occurring pubertal growth spurt. ___ also contribute at puberty

androgens

Draw normal growth curve

Draw normal growth curve

The growth hormone has ___ effects. It mobilizes fat stores as a major energy source while conserving glucose for glucose-dependent tissues. This metabolic action is unrelated to growth

metabolic

The growth hormone promotes growth by signaling an increase in the number of cells and size of cells in target organs. It stimulates the uptake of amino acids and ___ in target cells.

protein synthesis

The growth hormone stimulates the lengthening of bones at the ___. It stimulates osteoblast activity and the proliferation of epiphyseal cartilage. New bone tissue replaces cartilage in this region

epiphyseal plate

The growth hormone stimulates bone thickness by activating ___ under the periosteum.

osteoblasts

Draw anatomy and growth of long bones diagram (s & p.680)

Draw anatomy and growth of long bones diagram (s & p.680)

The growth hormone exerts its effects indirectly by stimulating ___. These substances are also called insulin-like growth factors. They mediate most of the growth-promoting effects of the hormone

somatomedins

The main source of these insulin-like growth factors is the liver. Their production depends on adequate nutrition. Their production is also related to age. The secretion of the growth hormone is regulated by ___ and GHIH.

GHRH

Many factors influence the secretion of the growth hormone. It increases one hour after a deep sleep. Exercise can increase the secretion of the growth hormone. An abundance of ___ increases its release

amino acids

A hyposecretion produces dwarfism in a child. In Laron dwarfism, tissues fail to respond to the growth hormone.

laron