What are the two main factors that affect hormone concentration in the blood?

The rate of hormone secretion into the blood and the rate of removal of the hormone from the blood.

How are water-soluble hormones transported in the blood?

They are dissolved in plasma and transported to target tissues where they diffuse out of capillaries.

What are the two principal mechanisms of bone growth stimulated by GH?

Growth in length at the epiphyseal cartilages and deposition of new bone on older bone surfaces.

What is another name for Growth Hormone (GH)?

Somatotropic hormone or somatotropin.

What happens to the epiphyseal cartilage by late adolescence?

It is progressively used up, leading to bony fusion and cessation of further lengthening of long bones.

What is the molecular weight of Growth Hormone?

22,005.

What is the formula for calculating metabolic clearance rate?

Metabolic clearance rate = Rate of disappearance of hormone from the plasma / Concentration of hormone.

What types of cells does GH specifically promote growth in?

Bone growth cells and early muscle cells.

What determines the specific action of cAMP in target cells?

The nature of the intracellular machinery and enzymes present in the cells.

What is the role of cAMP in hormone action?

cAMP acts as a second messenger to mediate intracellular effects of hormones.

How do lipid-soluble hormones interact with cells?

They cross the cell membrane and bind with protein receptors inside the cell.

What determines whether a target cell responds to a hormone?

The presence of specific receptors for the hormone on the target cell.

What initiates a powerful cascading activating force for the entire cell?

Hormone binding to cell surface receptors.

What are the typical concentrations of hormones in the blood?

From 1 picogram to a few micrograms per milliliter.

What happens when a hormone binds to an inhibitory G protein?

Adenylyl cyclase is inhibited, reducing cAMP formation.

How are the secretion rates of various hormones typically measured?

In micrograms or milligrams per day.

How are hormones cleared from the plasma?

Through metabolic destruction by tissues, binding with tissues, excretion by the liver into bile, and excretion by the kidneys into urine.

How many receptors can a cell have for a specific hormone?

Between 2000 to 100,000 receptors.

What happens to hormones that are bound to plasma proteins?

They are biologically inactive until they dissociate from plasma proteins and are cleared from the blood at much slower rates.

What can excessive amounts of Growth Hormone (GH) lead to in terms of fat metabolism?

It can cause significant fat mobilization from adipose tissue, leading to ketosis and fatty liver.

How does GH affect carbohydrate metabolism?

GH decreases glucose uptake in tissues, increases glucose production by the liver, and increases insulin secretion, leading to insulin resistance.

What is the term used to describe the effects of GH on glucose metabolism?

Diabetogenic.

What is the typical onset time for some hormones to develop full action?

A few seconds to minutes.

What are the three subunits of trimeric G proteins?

α, β, and γ subunits.

What is the function of the activated hormone-receptor complex?

It binds to a specific regulatory sequence of DNA to activate or repress gene transcription.

What happens when a ligand binds to the extracellular part of a receptor?

A conformational change occurs, activating G proteins and inducing intracellular signals.

What happens when a hormone binds to a specific receptor protein in the cytoplasm?

It then diffuses or is transported into the nucleus to activate transcription of specific genes.

What happens when a hormone binds to its receptor?

It usually initiates a cascade of reactions in the cell.

What is the role of mRNA in hormone action?

mRNA promotes the translation process at the ribosomes to form new proteins.

What is the role of the hypothalamic-hypophysial portal blood vessels?

They transport blood from the hypothalamus to the anterior pituitary gland.

What is the median eminence?

The functional link between the hypothalamus and the anterior pituitary gland.

How long may it take for hormones like thyroxine or growth hormone to show full effects?

Months.

What is the metabolic clearance rate?

The rate at which a hormone is removed from the blood, expressed in milliliters of plasma cleared of the hormone per minute.

What are the two other important second messengers besides cAMP?

Calcium ions and products of membrane phospholipid breakdown.

How does GH influence the thickness of bones throughout life?

GH strongly stimulates osteoblasts, allowing bones to become thicker as long as deposition exceeds resorption.

What is the role of Gs protein in the adenylyl cyclase-cAMP system?

It stimulates the adenylyl cyclase to convert ATP into cAMP.

What role does insulin play in relation to GH and amino acids?

Insulin enhances the transport of some amino acids into cells, similar to its effect on glucose transport.

What happens after cAMP is formed inside the cell?

It activates a cascade of enzymes leading to the cell's response to the hormone.

How do inhibitory G proteins (Gi) and stimulatory G proteins (Gs) affect intracellular enzymes?

They can either increase or decrease the activity of intracellular enzymes depending on the hormone receptor coupling.

What is the half-life of angiotensin II in circulation?

Less than a minute.

What effect do thyroid hormones have on gene transcription?

They cause increased transcription by specific genes in the nucleus.

What is necessary for GH to promote growth effectively?

Adequate insulin activity and availability of carbohydrates.

What percentage of steroid or thyroid hormones in the plasma exists free in solution?

Usually less than 10%.

What hormones control the secretion of anterior pituitary hormones?

Hypothalamic releasing and inhibitory hormones.

Where are receptors for some hormones located?

On the target cell membrane, in the cytoplasm, or in the nucleus.

Which hormone causes the release of TSH?

Thyrotropin-releasing hormone (TRH).

What is the inactive state of G proteins characterized by?

The α subunit binds guanosine diphosphate (GDP).

What is the function of corticotropin-releasing hormone (CRH)?

It causes the release of ACTH.

What occurs when GDP is exchanged for GTP in G proteins?

The α subunit dissociates from the trimeric complex and associates with other intracellular signaling proteins.

What is the role of growth hormone inhibitory hormone (GHIH)?

It inhibits the release of growth hormone (GH).

How does GH enhance protein deposition in tissues?

By enhancing amino acid transport, RNA translation, and decreasing protein catabolism.

What second messenger products are generated by the breakdown of phosphatidylinositol biphosphate (PIP2)?

Inositol triphosphate (IP3) and diacylglycerol (DAG).

What determines the response of different tissues to a hormone?

The specificity of the receptors and the expression of genes that the receptor regulates.

What is the role of the leptin receptor?

It regulates appetite and energy balance by activating intracellular signaling pathways.

What does DAG activate in the cell?

Protein kinase C, leading to phosphorylation of proteins.

From what embryonic structure does the anterior pituitary originate?

Rathke’s pouch, an invagination of the pharyngeal epithelium.

What happens to protein breakdown under the influence of GH?

GH decreases the breakdown of cell protein.

What other intracellular pathways are activated by JAK2 phosphorylation?

Mitogen-activated protein kinases (MAPK) and phosphatidylinositol 3-kinase (PI3K).

What does adrenocorticotropic hormone control?

The secretion of adrenocortical hormones that affect metabolism of glucose, proteins, and fats.

What is the function of antidiuretic hormone (vasopressin)?

It controls the rate of water excretion into the urine.

What controls the secretion of the anterior pituitary?

Hypothalamic releasing and inhibitory hormones.

What mechanism prevents overactivity of hormone systems?

Negative feedback.

How long does it typically take for the full action of steroid hormones like aldosterone to occur?

At least 45 minutes, potentially up to several hours or days.

What does gonadotropin-releasing hormone (GnRH) stimulate?

The release of LH and FSH.

What distinguishes enzyme-linked hormone receptors from G protein-coupled receptors?

Enzyme-linked receptors pass through the membrane only once and have their catalytic site on the inside.

What is the typical half-life range for adrenal steroids in circulation?

Between 20 and 100 minutes.

How does GH affect fat utilization for energy?

It causes the release of fatty acids from adipose tissue and enhances their conversion to acetyl-CoA for energy.

What can cause up-regulation of hormone receptors?

Increased hormone concentration and binding with target cell receptors.

How does calcium entry into cells initiate a second messenger system?

By binding to calmodulin, which then initiates multiple effects inside the cell.

What hormones are secreted by the anterior pituitary?

Six major peptide hormones that control metabolic functions.

What is the role of growth hormone?

It promotes growth by affecting protein formation, cell multiplication, and differentiation.

What hormone promotes mammary gland development and milk production?

Prolactin.

What role does oxytocin play during childbirth?

It helps in the delivery of the baby at the end of gestation.

What happens to pituitary hormone secretion when the gland is removed from the hypothalamus?

Secretion rates fall to very low levels (except for prolactin).

What are the metabolic effects of Growth Hormone?

Increased protein synthesis, mobilization of fatty acids, and decreased glucose utilization.

What metabolic hormones are formed in thyroid cells stimulated by cAMP?

Thyroxine and triiodothyronine.

What is the function of aldosterone in renal tubular cells?

It promotes sodium reabsorption and potassium secretion.

What is the function of prolactin inhibitory hormone (PIH)?

It inhibits prolactin secretion.

What is the effect of down-regulation of hormone receptors?

It decreases the target tissue’s responsiveness to the hormone.

What are the two distinct portions of the pituitary gland?

The anterior pituitary (adenohypophysis) and the posterior pituitary (neurohypophysis).

What family of kinases is associated with the leptin receptor?

The janus kinase (JAK) family, specifically JAK2.

What influences cyclical variations in hormone release?

Seasonal changes, stages of development, aging, diurnal cycles, and sleep.

How do G protein-linked hormone receptors function?

They regulate the activity of target proteins by coupling with G proteins.

What is the primary function of hormone-receptor complexes?

To alter the function of the receptor and initiate hormonal effects.

What hormone is secreted by somatotropes?

Human growth hormone (hGH).

How does the activation of adenylyl cyclase amplify the hormone's effect?

A small amount of activated adenylyl cyclase can activate many molecules of the next enzyme, creating a cascade effect.

What is the effect of GH on amino acid transport?

GH enhances the transport of most amino acids through cell membranes.

What role does IP3 play in the cell?

It mobilizes calcium ions from mitochondria and the endoplasmic reticulum.

How does growth hormone (GH) exert its effects?

Directly on almost all tissues of the body.

What is an example of positive feedback in hormone secretion?

The surge of luteinizing hormone (LH) due to estrogen before ovulation.

What is the role of ion channel-linked receptors?

They cause changes in the structure of the receptor, opening or closing channels for ions.

What is one specific function of calmodulin?

To activate myosin light chain kinase, causing smooth muscle contraction.

How do steroid hormones primarily act on target cells?

By increasing protein synthesis.

Which hormones control the growth of the ovaries and testes?

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

What are the five cell types found in the anterior pituitary gland?

Somatotropes, corticotropes, thyrotropes, gonadotropes, and lactotropes.

What types of signals does the hypothalamus receive?

Nervous signals from pain, emotions, olfactory stimuli, and concentrations of nutrients and hormones.

What happens after a stimulus causes the release of a hormone?

Conditions or products from the hormone's action tend to suppress further release.

What is the first step in a hormone's action?

To bind to specific hormone receptors.

What is the 'ketogenic' effect of excessive Growth Hormone?

It promotes fat utilization over carbohydrates and proteins.

What is the result of JAK2 activation in the leptin receptor signaling pathway?

Phosphorylation of signal transducer and activator of transcription (STAT) proteins, activating transcription of target genes.

When is growth hormone secretion markedly increased?

During the early period of sleep.

What role does the suprachiasmatic nucleus (SCN) play in hormone release?

It serves as a 'master clock' controlling rhythmic patterns of biological clocks.

How are posterior pituitary hormones synthesized?

By cell bodies in the hypothalamus.

What is the first step in the action of steroid hormones like aldosterone?

A) The hormone binds to DNA

B) The hormone diffuses across the cell membrane

C) The hormone is secreted into the bloodstream

D) The hormone is converted into mRNA

E) The hormone activates ribosomes

How many receptors can a target cell have for a specific hormone?

A) 10 to 100

B) 200 to 100,000

C) 1,000 to 10,000

D) 50 to 500

E) 500 to 5,000

Where are receptors for some hormones located in target cells?

A) Only in the nucleus

B) Only on the cell membrane

C) In the cytoplasm or nucleus, and on the cell membrane

D) Only in the cytoplasm

E) Only in the extracellular fluid

What is the typical onset time for hormones like thyroxine or growth hormone to develop full action?

A) A few seconds

B) A few minutes

C) A few hours

D) A few days

E) A few months

What is the typical concentration range of hormones in the blood?

A) 1 milligram to 10 milligrams per milliliter

B) 1 picogram to a few micrograms per milliliter

C) 1 gram to 10 grams per milliliter

D) 1 nanogram to 1 microgram per milliliter

E) 1 microgram to 1 milligram per milliliter

What influences cyclical variations in hormone release?

A) Only seasonal changes

B) Only aging

C) Neural pathways and circadian rhythms

D) Only sleep patterns

E) Only physical activity

What happens after the hormone-receptor complex enters the nucleus?

A) It promotes protein degradation

B) It binds to specific points on DNA

C) It is transported back to the cytoplasm

D) It activates ribosomal RNA

E) It inhibits gene transcription

How long does it typically take for the full action of steroid hormones to occur?

A) Immediately

B) 15 minutes

C) 45 minutes to several hours

D) 24 hours

E) Several days

What type of receptors do most hormones use to exert their effects?

A) Ion channel-linked receptors

B) G protein-linked receptors

C) Enzyme-linked receptors

D) Only nuclear receptors

E) Only membrane receptors

What distinguishes the anterior pituitary from the posterior pituitary?

A) They secrete the same hormones

B) They originate from the same embryonic tissue

C) They have different physiological functions

D) They are connected to the hypothalamus in the same way

E) They are both composed of neural tissue

What is the role of cAMP in hormone action?

A) It inhibits all cellular functions

B) It increases the concentration of calcium ions

C) It can either increase or decrease phosphorylation of key proteins

D) It solely initiates muscle contraction

E) It has no effect on hormone action

What happens when a hormone binds to a receptor coupled with an inhibitory G protein?

A) It increases cAMP formation

B) It activates protein kinase C

C) It inhibits adenylyl cyclase

D) It causes muscle contraction

E) It decreases calcium ion concentration

What happens when a ligand binds to the extracellular part of a G protein-coupled receptor?

A) It activates the receptor without any changes

B) It causes a conformational change that activates G proteins

C) It directly opens ion channels

D) It inactivates the receptor

E) It binds to DNA directly

What is the role of GDP in the inactive state of trimeric G proteins?

A) It activates the G proteins

B) It binds to the β subunit

C) It binds to the α subunit

D) It is exchanged for ATP

E) It is not involved in G protein function

What is the primary function of Growth Hormone (GH)?

A) To decrease cell size

B) To promote growth of almost all tissues capable of growing

C) To inhibit mitosis

D) To increase glucose utilization

E) To decrease protein synthesis

What is down-regulation of hormone receptors?

A) Increase in receptor numbers

B) Decrease in receptor numbers or sensitivity

C) Activation of all receptors

D) Permanent destruction of receptors

E) Increase in hormone production

What mechanism primarily controls hormone secretion to prevent overactivity?

A) Positive feedback

B) Negative feedback

C) Direct stimulation

D) Hormonal amplification

E) Neural control

Which enzyme is activated by the binding of a hormone to its receptor that leads to the formation of cAMP?

A) Phospholipase

B) Adenylyl cyclase

C) Protein kinase

D) Guanylate cyclase

E) Calcium ATPase

How does Growth Hormone (GH) affect carbohydrate metabolism?

A) Increases glucose uptake in tissues

B) Decreases insulin secretion

C) Increases glucose production by the liver

D) Decreases blood glucose concentration

E) Enhances glucose utilization in skeletal muscle

What is the function of the hormone-receptor complex once formed inside the cell?

A) It degrades cAMP

B) It binds to the cell membrane

C) It activates or represses transcription of specific genes

D) It produces more hormones

E) It transports ions across the membrane

Which of the following is NOT a second messenger mentioned in the text?

A) cAMP

B) Calcium ions

C) Cyclic guanosine monophosphate (cGMP)

D) Protein kinase

E) Products of membrane phospholipid breakdown

What distinguishes enzyme-linked hormone receptors from G protein-coupled receptors?

A) They are always inactive

B) They pass through the membrane multiple times

C) They pass through the membrane only once

D) They do not bind hormones

E) They are only found in the cytoplasm

What is the function of the leptin receptor when activated?

A) It directly activates ion channels

B) It phosphorylates JAK2 molecules

C) It binds to DNA directly

D) It inhibits protein synthesis

E) It does not have any physiological effects

What is the role of prolactin inhibitory hormone (PIH)?

A) To stimulate growth hormone release

B) To inhibit prolactin secretion

C) To promote TSH release

D) To stimulate ACTH release

E) To inhibit cortisol production

What happens to hormones that are bound to plasma proteins in terms of their biological activity?

A) They are always active

B) They are biologically inactive until they dissociate

C) They are more potent

D) They are rapidly excreted

E) They are immediately available to target cells

What happens when a hormone binds to its receptor?

A) It has no effect on the cell

B) It initiates a cascade of reactions in the cell

C) It destroys the receptor

D) It causes the cell to die

E) It prevents other hormones from binding

What effect does GH have on protein synthesis?

A) Decreases protein synthesis

B) No effect on protein synthesis

C) Increases the rate of protein synthesis

D) Only affects fat metabolism

E) Inhibits amino acid transport

What is the primary function of growth hormone secreted by the anterior pituitary?

A) Regulates blood pressure

B) Promotes growth of the entire body

C) Stimulates thyroid hormone secretion

D) Controls metabolism of fats

E) Inhibits protein formation

What happens to the growth of bones after adulthood is reached?

A) Bones continue to lengthen indefinitely

B) Bones stop lengthening but soft tissues continue to grow

C) Bones shrink in size

D) Bones become more brittle

E) Bones grow faster than soft tissues

What is the role of cAMP in hormone action?

A) It directly binds to DNA

B) It serves as a second messenger

C) It is a type of hormone

D) It inhibits enzyme activity

E) It is produced only in the nucleus

What condition can result from excessive fat mobilization due to high levels of Growth Hormone (GH)?

A) Hyperglycemia

B) Ketosis

C) Hypoglycemia

D) Acidosis

E) Hypertension

What is one of the metabolic effects of GH?

A) Increased glucose utilization

B) Decreased protein synthesis

C) Increased mobilization of fatty acids

D) Decreased amino acid transport

E) Increased fat storage

How does GH affect amino acid transport?

A) Decreases amino acid transport

B) Has no effect on amino acid transport

C) Enhances transport of most amino acids through cell membranes

D) Only affects glucose transport

E) Inhibits amino acid uptake

What occurs when GTP replaces GDP in the G protein signaling pathway?

A) The α subunit remains bound to the β and γ subunits

B) The α subunit dissociates from the trimeric complex

C) The receptor becomes inactive

D) The hormone is permanently bound

E) The signaling pathway is terminated

What percentage of anterior pituitary cells are corticotropes that secrete ACTH?

A) 10% to 15%

B) 20%

C) 30% to 40%

D) 50%

E) 3% to 5%

What is one of the principal mechanisms by which Growth Hormone stimulates bone growth?

A) Decreasing protein deposition

B) Inhibiting osteoblast activity

C) Increasing reproduction of chondrocytic and osteogenic cells

D) Reducing blood supply to bones

E) Promoting fat deposition in bones

What is the metabolic clearance rate of a hormone?

A) The rate of hormone secretion into the blood

B) The rate of hormone production in the glands

C) The rate of removal of the hormone from the blood

D) The rate of hormone binding to receptors

E) The rate of hormone diffusion into tissues

What is the half-life of angiotensin II in circulation?

A) Less than a minute

B) 5 minutes

C) 30 minutes

D) 1 hour

E) 24 hours

How does GH affect fat metabolism?

A) Increases fat storage

B) Decreases fatty acid mobilization

C) Enhances fat utilization for energy

D) Inhibits fatty acid release

E) Has no effect on fat metabolism

What is an example of positive feedback in hormone secretion?

A) Insulin release after eating

B) Luteinizing hormone surge before ovulation

C) Cortisol release during stress

D) Thyroid hormone release during cold exposure

E) Growth hormone release during sleep

What hormone is primarily responsible for promoting mammary gland development and milk production?

A) Oxytocin

B) Luteinizing hormone

C) Prolactin

D) Follicle-stimulating hormone

E) Adrenocorticotropic hormone

What type of hormones typically bind to intracellular receptors?

A) Water-soluble hormones

B) Lipid-soluble hormones

C) Peptide hormones

D) Amino acid-derived hormones

E) Steroid hormones

What is the primary function of antidiuretic hormone (vasopressin)?

A) Stimulate milk production

B) Control water excretion into urine

C) Regulate thyroid function

D) Promote growth of the ovaries

E) Induce labor during childbirth

Which cell type in the anterior pituitary secretes human growth hormone (hGH)?

A) Corticotropes

B) Thyrotropes

C) Gonadotropes

D) Somatotropes

E) Lactotropes

What is a key characteristic of patients with acromegaly compared to those with type 2 diabetes?

A) They are usually overweight

B) They have excessive visceral fat

C) They are usually lean with little visceral fat

D) They have low insulin levels

E) They have high carbohydrate intake

What is the primary method of transport for water-soluble hormones in the blood?

A) Bound to plasma proteins

B) Dissolved in plasma

C) Attached to red blood cells

D) In the form of solid particles

E) As free gases

What happens to the epiphyseal cartilage by late adolescence?

A) It increases in thickness

B) It remains unchanged

C) It is progressively used up

D) It converts to muscle tissue

E) It becomes more elastic

Where are the neuronal cell bodies that give rise to the median eminence nerve endings located?

A) In the anterior pituitary gland

B) In the spinal cord

C) In the hypothalamus and basal brain

D) In the adrenal cortex

E) In the thyroid gland

Which hormones are classified as gonadotropic hormones?

A) Prolactin and oxytocin

B) Follicle-stimulating hormone and luteinizing hormone

C) Thyroid-stimulating hormone and adrenocorticotropic hormone

D) Growth hormone and prolactin

E) Antidiuretic hormone and oxytocin

What are the two second messenger products generated by the breakdown of phosphatidylinositol biphosphate (PIP2)?

A) cAMP and calcium

B) IP3 and DAG

C) ATP and ADP

D) Protein kinase A and C

E) Myosin and actin

What is the function of calmodulin in the calcium-calmodulin second messenger system?

A) It inhibits protein synthesis

B) It binds calcium and initiates multiple cellular effects

C) It decreases calcium ion concentration

D) It activates adenylyl cyclase

E) It transports hormones in the blood

How is secretion from the posterior pituitary gland primarily controlled?

A) By hormonal signals from the thyroid

B) By nerve signals from the hypothalamus

C) By blood flow from the heart

D) By feedback from the kidneys

E) By external environmental factors

What is the primary function of the hypothalamic-hypophysial portal blood vessels?

A) To transport oxygen to the anterior pituitary

B) To connect the hypothalamus and the anterior pituitary gland

C) To supply blood to the posterior pituitary

D) To drain blood from the anterior pituitary

E) To filter hormones from the bloodstream

What percentage of steroid or thyroid hormones typically exists free in solution in the plasma?

A) 50%

B) 25%

C) Less than 10%

D) 75%

E) 90%

Which method is NOT a way hormones are cleared from the plasma?

A) Metabolic destruction by tissues

B) Binding with tissues

C) Excretion by the liver into bile

D) Excretion by the lungs into air

E) Excretion by the kidneys into urine

How do steroid hormones primarily affect target cells?

A) By increasing calcium ion concentration

B) By causing protein synthesis

C) By inhibiting enzyme activity

D) By activating phospholipase C

E) By decreasing cell permeability

What is necessary for Growth Hormone (GH) to effectively promote growth?

A) High levels of fatty acids

B) Adequate insulin activity and carbohydrates

C) Low blood glucose levels

D) Increased protein intake

E) High levels of glucagon

Which hormone is responsible for stimulating the release of TSH from the anterior pituitary?

A) Corticotropin-releasing hormone (CRH)

B) Prolactin inhibitory hormone (PIH)

C) Thyrotropin-releasing hormone (TRH)

D) Gonadotropin-releasing hormone (GnRH)

E) Growth hormone inhibitory hormone (GHIH)

Which hormone is known to inhibit the release of growth hormone (GH)?

A) Gonadotropin-releasing hormone (GnRH)

B) Thyrotropin-releasing hormone (TRH)

C) Growth hormone inhibitory hormone (GHIH)

D) Corticotropin-releasing hormone (CRH)

E) Prolactin releasing hormone (PRH)