Untitled Flashcards Set

*Up-regulation - ↑ in # of receptors in

deficient hormone

- more sensitive to hormone

3. Mechanisms of interaction of hormone w/target cell

* Peptide & protein hormones, not lipid soluble - so...?

3 Interaction w/plasma membrane receptors

1. First messenger - Hormone

* binds to receptor site on membrane

2. Second messenger produced - Cyclic AMP

*ATP is converted to cyclic AMP by adenylate cyclase

*reaction is stimulated by binding of hormone w/ receptor on membrane (outer)

*note G protein – slowly deactivate

*cAMP ultimately degraded by phosphodiesterase

Note: Ca++ ions may be 2nd messengers

*enters cells when hormone binds

*bind to calmodulin – activates protein kinases...

3. cAMP activates a protein kinase enzyme to phosphorylate a protein

* Response by cell:

*enzyme regulation (↑ or ↓ enzyme production)

*secretion

*protein synthesis

*membrane permeability

*only a little hormone is necessary (chain reaction)

4 Interaction w/ intracellular receptors

1. Receptor sites usually w/in nucleus

2. Binding occurs.

3. Receptor-hormone complex alters DNA expression (turns on or off)

4. mRNA is produced & released to cause protein synthesis

5 Interaction between hormones

1. Permissive effect –prior exposure of another

hormone is required

*↑ in # of receptors?

Ex: estrogen before progesterone in menstrual cycle

2. Synergistic effect – two or more hormones act together

Ex: prolactin (milk production) w/ estrogen

3. Antagonistic effect – opposing actions

Ex: insulin & glucagon from pancreas

6 Site of hormonal action

7 Circulating hormones – affect target areas distant from site of production by glands

* carried by bloodstream

8 Local (Tissue) hormones –affect immediate area of production

*may be produced by all cells

*Eicosanoids - Prostaglandins (PG's)

*lipids

*influences formation of cAMP

*involved in inflammatory response (histamine)

*NO

9 Control of hormonal secretions

* determined by body's needs

10 Negative feedback control systems

*result is opposite the stimulus

* i.e., ↑ hormone will cause a ↓ in production

a. Control by direct stimulation from nervous system

Ex: NE & epinephrine release from adrenal medulla

ADH release from posterior pituitary

b. No nervous stimulation; blood chemical levels stimulate release of hormone

Ex: ↑ glucose blood level; ↑ insulin release

c. Regulating hormones from hypothalamus

1. Releasing hormones - ↑ secretions by gland

2. Inhibiting hormones - ↓ secretions by gland

11 Positive feedback control

*result intensifies stimulus

* Ex: oxytocin (OT) from posterior pituitary...

12 Endocrine glands

13 Pituitary gland – Hypophysis “Master gland”

14 Size 1 – 1.5 cm (.5”) diameter

15 Location

*attached by infundibulum to hypothalamus

16 General structure

*two lobes separated avascular zone → pars intermedia

1. Adenohypophysis

*anterior lobe

*glandular portion

*75% total gland weight

*no direct nerve connection to brain... blood vessels connect

2. Neurohypophysis

*posterior lobe

*stores hormones produced in the hypothalamus

*neural connection to hypothalamus

17 General physiology

1. Adenohypophysis

*receive regulating hormones from hypothalamus

Via Hypophyseal Portal System:

superior hypophyseal arteries

primary plexus (capillaries) regulating hormones

(hypothalamus)

hypophyseal portal veins

secondary plexus (capillaries) hormones

(anterior pituitary)

anterior hypophyseal veins

a. Cell types

*somatotrophs, thyrotrophs, gonadotrophs, lactotrophs, corticotrophs,

b. Hormones

1. Human growth hormone (hGH)

*also known as: somatotropin or somatotropic hormone

* Tropic hormone – stimulates other glands

a. Functions of hGH – stimulate production of insulinlike growth factors (IGF's) by

tissue cells, which...

1.↑ rate of growth & maintain skeletal muscles

2.↑ protein synthesis by ↑ rate of a.a.'s entering cells

3.↓ protein breakdown

4.↑ fat catabolism

5.↓ glucose take up & use by cells

6.↑ blood glucose concentration

*diabetogenic effect - mimics diabetes mellitus

b. Control of hGH release

1. Regulating hormones from hypothalamus

a. GHRH – growth hormone releasing hormone

b. GHIH – growth hormone inhibiting hormone

2. Hypoglycemia – low blood sugar

*promotes GHRH release → stimulate hGH release

3. Hyperglycemia – high blood sugar

*promotes GHIH release

c. Pathology

1. Dwarfism (Pituitary dwarfism)

– hyposecretion of hGH

Treatment? – hGH during childhood while bones can still lengthen

2. Giantism – hypersecretion of hGH during

childhood

*long bones lengthen

Acromegaly – hypersecretion of hGH during

adulthood

*bones of face thicken

2. Thyroid - stimulating hormone (TSH) Thyrotropin

*stimulates thyroid gland (tropic hormone

*release controlled by thyrotropin releasing hormone (TRH) from hypothalamus;

*release of TRH controlled by metabolism, blood chemical levels

(negative feedback)

3. Adrenocorticotropic hormone (ACTH)

*stimulates adrenal cortex

*controlled by corticotropin releasing hormone (CRH)

*release of CRH influenced by stress, low blood glucose, trauma

4. Follicle stimulating hormone (FSH)

*stimulates ovaries to produce eggs & estrogen

*stimulates testes to produce sperm

*release controlled by gonadotropin releasing hormone (GnRH)

5. Luteinizing hormone (LH)

*stimulates ovulation & hormone production in ♀'s

*stimulates testosterone release in ♂'s

*prepares uterus for implantation

*release controlled by GnRH

6. Prolactin (PRL)

*stimulates milk production

*release controlled by PIH (dopamine) & PRH (during pregnancy)

7. Melanocyte stimulating hormone (MSH)

*↑ skin pigmentation; receptors in brain...

*release controlled by...CRH or PIH

2. Neurohypophysis

*posterior lobe of hypophysis

*no glandular material

a. Storage of hormones produced by hypothalamus

*neurosecretory cells – produce hormones

*hormones to posterior pituitary via hypothalamic –hypophyseal tract

*hormones transferred by neurophysins (protein carriers)

- takes approx. 10 hours

*Pituicytes

- cells in posterior pituitary that store hormones

b. Hormones

18 Oxytocin (OT) – Pitocin, commercially

a. Function – stimulates muscle contractions:

*in uterus during labor

*mammary glands during lactation

b. Control - Positive feedback!

*beg. of labor → contractions → afferent impulses to hypothalamus →

↑ contractions

*milk let-down reflex – latent pd. after baby begins suckling (30sec -1min)

2. Antidiuretic hormone (ADH)

a. Function

1. Conservation of body water by reabsorption of water from urine by kidneys

2. Vasopressin – constricts arterioles; ↑ blood pressure

b. Control

1. Osmoreceptors in hypothalamus

– detect changes in osmotic pressure caused by changes in salt & water

conc.

*Dehydration- ↑ salt; ↓ water (↑ osmotic pressure)

↑ADH; ↓ urine output

* Overhydration - ↓ salt; ↑ water (↓ osmotic pressure)

↓ ADH; ↑ urine output

2. Pain, stress. drugs affects hypothalamus

* ↑ ADH release

c. Pathology

*dysfunction of neurohypophysis

- diabetes insipidis

*hyposecretion of ADH.....note symptoms

*↑ urine ↑ dehydration ↑thirst;

*TRT? ADH

2. Thyroid

a. Structure of glands

19 Lobes

a. Two Lateral lobes on either side of trachea

b. Isthmus – connects 2 lobes

c. Pyramidal lobe – extends upward from isthmus

(may be absent)

20 Cells

a. Follicular cells

*surround thyroid follicles

*produce thyroid hormones

*amines Thyroxine (T4) in ↑ amounts

Triiodothyronine (T3) in ↑ strength

b. Parafollicular cells

*outside follicular cells, away from lumen

* produce calcitonin (CT)

*↑Ca++ uptake in bone tissue (↓ blood Ca++ level)

hypocalcemia used to treat postmenopausal osteoporosis

(Miacalcin)

hypercalcemia release controlled by blood Ca levels

b. Manufacture & release of thyroid hormones

* I- into follicular cells from bloodstream

* I2 united with tyrosine to form thyroid hormone

* Thyroglobulin (TGB) & hormones form thyroid

colloid to store hormone

* Thyroxine-binding globulin (TBG protein) carries

hormones in blood

c. Function of thyroid hormones

1. Regulation of organic metabolism

*calorigenic effect - ↑ body temp. by ↑metabolism

2. Regulate tissue growth; esp. neural tissue

*w/hGH

3. Increase reactivity of nervous system

*↑ cardiovascular function (blood flow; HR)

*↑digestive function

*↑nervousness

d. Control of release of thyroid hormones

*↑ body need for energy (low hormone levels) → TRH → TSH

e. Pathology of thyroid gland

1. Hyposecretion of thyroid hormones

a. During infancy cretinism

*results in dwarfism & mental retardation

*TRT? Thyroid hormones

b. During adulthood myxedema

*slow metabolism; slow HR

*puffy facial features – edema

*TRT? Thyroid hormones

2. Hypersecretion of thyroid hormones

*results in high metabolic rate

*enlarged thyroid (goiter)

*TRT? antithyroid drugs

radioactive iodine

surgery

3. Parathyroid glands (4)

a. Location

*superior & inferior on posterior surface of each lateral lobe of thyroid gland

b. Structure

1. Chief cells (Principal cells)

*actively produce parathyroid hormone (PTH), or parathormone

2. Oxyphil cells

*reserve supply of hormones?

*uncertain function

c. Function of PTH

*↓ blood phosphate (HPO4-2) levels

*also ↑ HPO4-2 in urine

*↑ blood Ca++ and Mg++ levels

Note: antagonistic to calcitonin(w/reference to Ca++)

* ↑ formation of calcitriol in kidneys

* ↑ absorption of Ca++ , Mg++, & HPO4-2 from GI tract into blood

d. Control

*pituitary not involved!

*parafollicular cells affected by blood Ca++ levels

*negative feedback control

low blood Ca++ level → ↑ PTH ↑ blood Ca++

Note pathology -

21 Adrenals -- Suprarenals

a. Location

*superior to each kidney

b. Structure and physiology

1. Adrenal cortex – outer portion of gland

*80-90% of gland

*highly vascularized

a. Zona glomerulosa

* produces mineralocortacoids

*deal w/ homeostasis of mineral concentrations

* Aldosterone - primary hormone of zona glomerulosa

* causes:

*reabsorption of Na+ from urine

*elimination of K+ in urine

Note: Reabsorption of Na+ causes:

*elimination of H+ ions in urine; ↓ blood acidity

*retention of HCO3– ions

*retention of H2O due to ↑ osmotic pressure,

therefore...

*Control of aldosterone release?

Renin-angiotensin pathway

↓ blood pressure → renin released→ angiotensin I produced

aldosterone angiotensin I

↑b.p. ← ↑Na+ ← release ← to II (by ACE)

High K+ concentration → aldosterone released

K+ eliminated

b. Zona fasciculata

*middle section of adrenal cortex

* produces glucocorticoids

1. Three types:

a. Cortisol (Hydrocortisone)

*95% of activity

b. Corticosterone

c. Cortisone

2. Function of glucocorticoids ...energy

a. Combat stress

1. Provides ↑ glucose

*gluconeogenesis – conversion of a substance other than CHO for

energy

(in ↓ blood glucose situations)

*occurs in liver

2. Lipolysis – breakdown of adipose tissue to release fatty acids

3. ↑ protein catabolism to provide amino acids

4. ↑ vasoconstriction by ↑ sensitivity of blood vessels

b. ↓ Immune responses

*anti-inflammatory – balance to inflammation

*note: cortisone shots...

3. Control of release of glucocorticoids

*Negative feedback system involving hypothalamus & pituitary

↓ Hormone level → ↑ CRH → ↑ ACTH → ↑ hormones

Note: Pathology

c. Zona reticularis

* produce gonadocorticoids - androgens

*androgens in ♀’s are converted to estrogen

*androgens in ♂’s are minimal compared to effects of testerone

2. Adrenal medulla

a. Structure

*chromaffin cells –surround blood-filled sinuses

*receives innervation from preganglionic fibers of sympathetic nervous system

*modified sympathetic autonomic ganglion

b. Function

*produce epinephrine (80%) & Norepinephrine

(adrenaline) (noradrenalin)

*hormones are sympathomimetric

*results mimic & intensify sympathetic effects

c. Control

stress → hypothalamus → preganglionic fibers

chromaffin cells → ↑ NE & epinephrine → ↑ fight or flight

4. Pancreas

22 Structure and physiology

1. Heterocrine gland – endocrine & exocrine

2. flattened; 4.5 to 6 “ long

3. posterior & inferior to stomach

4. head, body & tail regions

5. Pancreatic Islets (Islets of Langerhans)

*endocrine portion – 1% of organ

a. Alpha cells – 17% of islets

* secrete glucagon

*↑ blood glucose level thro' glycogenolysis & gluconeogenesis

*control of glucagon secretion?

*alpha cells detect ↓ blood sugar levels

(below normal...90mg/100ml)

*↓ blood glucose → ↑ glucagon

*note sympathetic innervation (exercise)

b. Beta cells – 70% of islet cells

* secrete insulin

*↓ blood glucose level by stimulating entry of glucose into skeletal muscles

via insulin receptors on cells

*control of insulin secretion?

*beta cells detect ↑ blood glucose levels and cause ↑ insulin release

*note parasympathetic innervation (vagus nerve)

Note: hGH & ACTH...?

c. Delta cells – 7 % of islet cells

* secrete GHIH (somatostatin)

*inhibits (controls) secretion of insulin & glucagon

*paracrine activity

d. F cells

*secrete pancreatic polypeptide

*concerned with digestive activity

23 Pathology of pancreas

1. Hyperglycemia - ↑ blood sugar → diabetes mellitus

a. Characteristics

1. Polyuria – excessive urination

2. Polydipsia – excessive thirst

3. Polyphagia – excessive eating

b. Types of diabetes

1. Type I Diabetes – juvenile onset; pre-20 years in age

- insulin - dependent

*insufficient insulin produced

*↓ in # of beta cells ... autoimmune?

Trt? insulin

2. Type II Diabetes – maturity onset; post 40 years in age

- non-insulin dependent

*90% of cases

*lack of insulin receptors on cells

Trt? diet, exercise

5. Pineal gland

*located in roof of third ventricle of brain

*secretion of melatonin

*produced from serotonin

* ↑ production during sleep

*seasonal affective disorder (SAD) due to ↑ production of melatonin during months

with ↓ light

E. Stress Response

*stressor – stimulus that elicits a stress response

*eustress – 'good stress', enables us to deal with extreme physical situations

*distress – 'bad stress', harmful as in illness

1. Fight-or-Flight response – short lived

*↑ hypothalamic stimulation of sympathetic division of ANS

*innervation of adrenal medulla

*↓ parasympathetic stimulation

*↑ glucose & oxygen to tissues...how?

*↑ rennin-angiotensin –aldosterone pathway

*↑ b.p.

2. Resistance reaction

*hormonal primarily; maintains response initiated by fight-or-flight

*hypothalamus releases:

CRH,TRH, & GHRH...result?

*ceases after stressors are removed; parasympathetic ↑

3. Exhaustion

*damage to body tissues may occur if hormone levels remain ↑ for too long a period

*prolonged exposure to stress may ↓ immune response, esp. due to ↑ cortisol levels