bio242 summer studying lecture 10a/b/c/d/e

What are hormones?

organic compounds

• steroid/steroid-like hormones

• nonsteroid hormones

What are steroids?

lipids containing complex rings of carbon and hydrogen atoms

• all steroid hormones produced from cholesterol

What are examples of steroid hormones?

testosterone, estrogen, cortisol, aldosterone

what are nonsteroid hormones?

1. amines

2. proteins

3. peptides

4. glycoproteins

What are amines?

derived from tyrosine (epinephrine, norepinephrine, thyroxine)

What are proteins?

composed of long chains of amino acids (growth hormones)

What are peptides?

short chains of amino acids (ADH, oxytocin)

What are glycoproteins?

carbohydrates joined to proteins (TSH)

What are the actions of hormones?

alters metabolic processes

1. alters enzyme activity

2. change rate of membrane transport of a substance

3. deliver messagees. by binding to receptors in/on target cell

What is upregulation?

increase in number of receptors on target cell, in response to a decrease in hormone level

What is downregulation?

decrease in number of receptors on targett cell due to increase in hormone level

What are the properties of steroid/thyroid hormones?

1. poor water solubility

2. transported through blood bound to plasma proteins

3. steroid hormones diffuse through lipid bilayer

4. causes transcription of particular genes in DNA

5. protein synthesis leads to action of hormone

What is the proceess of steroid hormone action?

1. lipid-soluble steroid hormones reaches target cell and crosses membrane

2. hormone combines w/ a protein receptor (usually in nucleus)

3. hormone-receptor complex activates transcription to synthesize specific mRNA molecules

4. mRNA molecules leave nucleus and enter cytoplasm

5. translation of mRNA molecules leads to synthesis of encoded proteins associated with hormone’s action

What are the properties of nonsteroid hormones?

cannot penetrate lipid bilayer of cell membranes

1. binds to receptors on target cell membranes

2. hormone considered “first messenger”

3. chemical that induces changes leading to hormone’s effect is considered second messenger

What is cAMP?

common second messenger

What is signal transduction?

1. nonsteroid hormone reaches a target cell

2. nonsteroid hormones diffuse through binds to receptor molecules on cell membranes

3. hormone binding activates G protein that bind and activate molecules of adenylate cyclase

4. adenylate cyclase catalyzes conversion of ATP into cAMP

5. cAMP activates existing proteins, causing a series of reactions leading to cellular changes associated with hormone’s actions

What is the roe of steroids in clinical application?

used to increase muscular strength

harmful effects include:

• decreasing natural testosterone productoin

• stunting growth

• breast development inn males

• male sexual characteristics in females

• damage to kidneys

• increase in LDL cholesterol

What is the role of HGH (human growth hormone) in clinical application?

used to enlarge muscles

• used instead of/along with steroids

What is erythropoietin?

used to increase the number of RBC and oxygen delivery to muscles

• used to treat certain forms of anemia, but can be used to improve athletic performance→ lead to heart attack and deathh

What are prostaglandins?

paracrine substances

1. very potent in small amounts

2. synthesized just before release (not stored in cells)

3. rapidly inactivated after use

4. regulate cellular response to hormones

5. can activate/inhibit adenylate cyclase→ controls cAMP production→ controle cell response to hormones

What are examples of effects of prostaglandins?

1. can contract/relax smooth muscle

2. stimulate/inhibit secrection

3. regulate blood pressure

4. control H2O an Na+ conc. in kidneys→ promotes inflammation

What mechanism is hormonal secretion usually regulated by?

negative feedback mechanisms

Where are hormones usuaslly broken down?

liver

how does negative feedback work in relation to hormones?

1. rising level of hormone leads to a decerease in hormone secretion

2. as hormone is used up, inhibition stops

3. secretion begins again

What are 3 methods of negative feedback control for hormones?

hypothalamus, nervous system, changes in composition of internal environment

What is hypothalamus control?

1. controls releae of anterior pituitary hormones

2. pituitary hormones secrete hormones that control activity of other glands (tropic)

What is nervous system control?

nervous system directly stimulates some glands to secrete hormones (via nerve impulses)

What is internal environment control?

changes in concentration of a specific substance in blood can stimulate/inhibit secretion of certain hormones

what is positive feedback in relation to hormone control?

control mechanism in which rising level of hormone leads to increase in secretion

• used in small number of cases of hormone control (mainly reproductive system)

What are the properties of the pituitary gland?

Lies at the base of brain→ sella turcica of sphenoid

1. controlled by brain, attached to hypothalamus by pituitary stalk (infundibiulum)

2. contains two lobes→ adenohypophysis, neurohypophysis

3. pars intermedia develops in fetus

What controls hormone secretion in the pituitary gland?

hypothalamus

What does the pars intermedia produce?

produce melanocyte-stimulating hormone (MSH)→ starts melaninn production

What are the properties of anterior lobe regulation?

Hypothalamic releasing hormones (release-inhibiting hormones) are transported to anterior lobe through the Hypophyseal Portal Veins

• stimulate cells of anterior lobe to release hormones

• each releasing hormones acts on specific group of cells in anterior pituitary→ can stimulate/inhibit pituitary secretions

What are the properties of the posterior lobe regulation?

Nerve impulses from the hypothalamus travel to posterior lobe through the infundibulum

• stimulate nerve endings in posterior lobe to release hormones

What is a 3-step pathway for hypothalamic control of peripheral effectors?

1. releasing/release-inhibiting hormone from hypothalamus acts on specific hormone-secreting cells in the anterior pituitary gland

2. anterior pituitary hormone acts on cells in a peripheral endocrine gland→ stimulates secretion

3. peripheral endocrine gland secretes hormone, exerting effects on target cells

What are the negative feedback controls for 3-step pathways?

1. final hormone in pathway inhibits secretion of both the releasing hormone and anterior pituitary hormone

2. anterior pituitary hormone inhibits secretion of releasing hormone

What are the properties of the anterior pituitary hormones?

consists of glandular epithelial tissue

• anterior pituitary hormoen produced in anterior lobe

• each anterior lobe hormone is released in response to a releasnig hormone from hypothalamus; some are inhibited from the hypothalamus

What are the 5 major anterior pituitary hormones?

1. growth hormnoe (GH)

2. prolactin (PRL)

3. Thyroid-Stimulating Hormone (TSH)

4. Adrenocorticotropic hormone (ACTH)

5. Follicle-Stimulating hormone (FSH)

6. Lueinizing hormone (LH)

What are the properties of Growth Hormone (Somatotropin)?

Stimulates cells to enlarge and divide rapidly

• increases amino acid uptake and protein synthesis

• decreases rate of carbohydrate usage

• increases rate of fat usage

What are the properties of prolactin?

promotes milk production in females, uncertain function in males

What are the properties of Thyroid-Stimulating Hormone (TSH)?

Stimulatets secretion of thyroid hormones (T3 and T4) from thyroid gland

What are the properties of the adrenocorticotropic Hormone (ACTH)?

Stimulates secretiton of cortisol and other glucocorticoids from adrenal cortex

What are the properties of Follicle-Stimulating Hormone (FSH)?

Causes growth and development of ovarian follicles in females, sperm production in males

What are the properties of luteinizing hormone (LH)?

Causes ovulation in females, ssex hormone production in both genders

What is the pathway for thyroid hormone secretion?

1. TRH is secreted by hypothalamus

2. TRH causes anterior pituitary to secrete TSH

3. TSH travels to thyroid gland, causes it to secrete thyroid hormones

4. thyroid hormones exert effects on target cells

5. thyroid hormones also exert negative feedback on secretion of TRH and TSH

How is TSH controlled in a TSH-Pathway?

1. controlled to some extent by level of TRH

2. controlled by negative feedback of thyroid hormones (final hormones in pathway)

What is hypopituitary dwarfism?

caused by deficiency of human growth hormone (HGH) during childdhood

• short stature, but body proportions and mental development are normal

• HGH treatment must start before bones completely ossify

What is gigantism?

Caused by oversecretion of GH during childhood

• height may exceed 8 feet, may have other metabolic problems

• often caused by pituitary tumor

What is acromegaly?

Caused by oversecretion of GH during adulthood, after epiphyseal ossification

• no increase in height, but bones thicken

• enlargement of tongue, nose, hands, feet , jaw, heart

What are the properties of posterior pituitary hormones?

Consists of nerve fibers from hypothalamus and neuroglia, unlike glandular epithelium of anterior lobe

• 2 hormones produced in hypothalamus (stored and released by posterior pituitary gland)

• transported to posterior pituitary gland via pituitary stalk (infundibulum)

What are the 2 hormones releaed by the posterior pituitary gland?

ADH and Oxytocin

What are the properties of antidiuretic hormone (ADH, vasopressin)?

Decrease urine production by reducing volume of H2O the kidneys excrete

• causes vasoconstrictino to increase blood pressure

What are the properties of oxytocin?

causes vasoconstriction to increase blood pressure

• causes muscle contraction on uterine wall during childbirth

• causes milk ejection during lactation

• no proven function in males, but may help w/ sperm movement or sexual response

What are the properties of the thyroid gland?

Consists of two lateral lobes (connected by isthmus)

• lies just below the larynx, anterior and lateal to the trachea

• can remove iodine from blood

• produces 3 hormones (T4, T3, Calcitonin)

What is T4?

Thyroxine, produced by follicular cells

What is T3?

Triiodothyronine, produced by follicular cells

What is calcitonin?

produced by extrafollicular cells

What are folllicles?

round secretory cells that make up the thyroid

• each follicle surrounded by single layer off follicular cells

• viscous colloid fills follicle cavities

• extrafollicular (C) cells lie outside follicles

What is hypothryoidism?

Cauaes lower metabolic rate, increased cold sensitivity, weight gain

What is congenital hypothyroidism in infants?

Results from abnormal thyroid structure/insufficient thyroid hormone

• problems w/ bone formation, growth, and intellectual abilities

What is congenital hypothyroidism in adults?

Fatigue, low metabolic rate, and weight gain

What is hyperthyroidism?

Causes high metabolic rate, restlessness, weight loss, overeating

• caused by noncancerous thyroid tumor, excess T4 medication, autoimmune disease

What are the properties of the parathyroid glands?

Located on posterior surface of thyroid gland

• 4 parathyroid glands

• secretes Parathyroid Hormone (PTH)

What are the properties of parathyroid hormone (PTH)?

Increases blood level of calcium, decreases phosphate

• sitmulates bone resorption

• indirecttly stimulates calcium absorption by stimulating a step in Vitamin D metabolism

• Acts on kidney to cause final step in production of active vitamin D

• acts on kidney to conserve calcium m and excrete phosphate in urine

What are the properties of the adrenal glands (suprarenal glands)?

Sit like a cap on each kidney

• numerous hormones secreted by adrenal glands

• maintins blood sodium levels and responding to stress

• includes certain sex hormones

• consists of outer cortex and inner medulla

What is the adrenal cortex?

Outer portion of gland

• secretes steroid hormones (aldostterone, cortisol, sex hormones)

What is the adrenal medulla?

Central portion of gland

• secretes amine hormones (80% epinephrine, 20% norepinephrine)

What are the layers of the adrenal glands (superficial to deep)?

1. capsule

2. adrenal cortex

3. adrenal medulla

What are the zones of the adrenal cortex (from superficial to deep)?

1. zone of glomerulosa

2. zone of fasciculata

3. zone of reticularis

What cells does the adrenal medulla consist of?

chromaffin cells

How are norepinephrine and epinephrine different?

Epinephrine does not have NH2→ instead, N+H+CH3

What is the precursor of norepinephrine?

dopamine

What is the precursor of epinephrine?

norepinephrine

What is the impact of epinephrine/norepinephrine on the heart?

heart rate increases, force of contractiton increases

What is the impact of epinephrine on blood vessels?

vasodilation→ crucial in skeletal muscle at onset of fight or flight

What is the impact of norepinephrine on blood vessels?

vasocontriction in skin and viscera→ shifts blood flow to other areas

What is the impact of epinephrine on systemic blood pressure?

some increase due to increased cardiac output

What is the impact of norepinephrine on systemic blood pressure?

some increaes due to increassed cardiac output and vasoconstriction

What is the impact of epinephrine on airways?

dilation

What is the impact of norepinephrine on airways?

some dilation

What is the impact of epinephrine on reticular formation of brainstem?

Activates

What are the properties of zona glomerulosa?

outer zone of adrenal cortex

• produces aldosterone and other mineralocorticoids

What are the properties of zona fasciulata?

middle zone of adrenal cortex

• produces cortisol and other glucocorticoids

What are the properties of the zona reticularis?

inner zone of adrenal cortex

• produces male sex hormones (androgens)