Module 13

Question 1

Define endocrine gland

Answer 1

A group of specialized cells that synthesize, store, and release hormones into the bloodstream to circulate to specific target cells with receptors for the hormone, which will either stimulate or inhibit activity of the cell

Question 2

Define hormone

Answer 2

A chemical released by an endocrine gland that, when bound to a receptor, can stimulate or inhibit the activity of a cell

Question 3

List the major organs in the endocrine system

Answer 3

Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
Adrenal glands
Pancreas
Gonads (ovaries or testes)

Question 4

List the functions of the endocrine system

Answer 4

Maintenance of the internal environment
Adaptation to stress
Control of growth and metabolism
Control of reproduction

Question 5

Identify 3 chemical subtypes of hormones

Answer 5

Derived from Tyrosine (amino acid)
Derived from proteins
Steroid hormones

Question 6

Describe how hormones with different chemical makeups are carried in the blood

Answer 6

Protein hormones - hydrophilic, circulate freely in the blood, but cannot diffuse through cell membrane

Steroid and thyroid (tyrosine) hormones - hydrophobic, require a protein carrier to circulate in the blood, but diffuse freely through the cell membrane

Question 7

Describe the basic features of hormones

Answer 7

Secreted into the blood in pulses by specific stimuli, in amounts that vary with strength of stimulus

Once secreted, are present in very small concentrations in the blood

Exert their effects by binding to receptors and regulating pre-existing reactions

Question 8

Define a hormone receptor

Answer 8

A unique structure in or on a cell that interacts with a hormone in a particular way

Can be located on the membrane, in the cytoplasm, or in the nucleus

Question 9

Describe receptors for hydrophilic hormones

Answer 9

Found on the cell membrane

When hormones attach, initiates a sequence of chemical reactions that will eventually alter activity in the cell

Three ways for the receptor to affect the cell: second messenger, tyrosine kinase, G-proteins

Question 10

Describe how the second messenger system works

Answer 10

Hormone binds to receptor, causes G-protein on inside of membrane to produce a second messenger (first messenger is the hormone), normally cAMP, released into cytoplasm, rapidly alters proteins already in the cell, altered proteins trigger sequence of reactions to alter cell activity

Question 11

Describe how tyrosine kinase works

Answer 11

Hormone/receptor complex activates tyrosine kinase on the inside surface of the membrane, and tyrosine kinase alters existing proteins that will then alter cell activity

Question 12

Describe how G-proteins work

Answer 12

When hormone attaches to receptor, G-protein activates within the cell, can open adjacent ion channels

Question 13

Describe how hormones are removed from blood

Answer 13

Same mechanism as other substances, metabolic destruction in the blood or by tissues (mainly liver and kidney), excretion by liver into bile, or excretion by kidneys into urine

Question 14

Describe how hormone secretion is controlled

Answer 14

Negative feedback

Question 15

Describe the location and general structure of the hypothalamus

Answer 15

Located at the base of the brain, above the pituitary gland and below the thalamus

Composed of many regions made of groups of nerve cell bodies (nuclei), several nuclei control the release of hormones from the pituitary gland

Question 16

List the functions of the hypothalamus (what its hormones contribute to)

Answer 16

Homeostatic mechanisms (body temp, water balance, energy production), regulates some behavioural drives of thirst, hunger, and sexual behaviour

Performs these functions by receiving large amounts of info from the body, including metabolic, hormonal, temp, and neural info

Question 17

List the hormones the hypothalamus releases

Answer 17

Prolactin Releasing Hormone (PRH)
Prolactin Inhibiting Hormone (PIH)
Thyrotropin Releasing Hormone (TRH)
Corticotropin Releasing Hormone (CRH)
Growth Hormone Releasing Hormone (GHRH)
Growth Hormone Inhibiting Hormone (GHIH)
Gonadotropin Releasing Hormone (GnRH)

Question 18

Describe the structure of the pituitary gland

Answer 18

Two regions, anterior and posterior

Anterior is made of endocrine tissue

Posterior is made of neural tissue

Question 19

Describe the function of the pituitary gland

Answer 19

Anterior receives hormones from the hypothalamic-hypophyseal portal system (releasing or inhibiting hormones to either stimulate or release pituitary hormones)

Posterior receives hormones from the hypothalamic-hypophyseal tract (neurohormones)

Question 20

Describe the functions of posterior pituitary hormones

Answer 20

ADH regulates water reabsorption in the kidney

Oxytocin regulates milk release from the breasts and causes contraction of the uterus during labour

Question 21

List the anterior pituitary hormones and associated hypothalamus hormones

Answer 21

Thyroid stimulating hormone (TSH) in response to TRH stimulates thyroid to secrete thyroid hormones, also causes growth of the thyroid (hyperplasia)

Adrenocorticotropic hormone (ACTH) in response to CRH, stimulates adrenal glands to secrete cortisol

Growth hormone (GH) in response to GHRH or GHIH/somatostatin, GHRH is stronger

Luteinizing hormone (LH) and follicle stimulating hormone (FSH) in response to GnRH, acts on testes and ovaries

Prolactin (PRL) in response to PRH and PIH, PIH is stronger, stimulates breast milk production

Question 22

Describe three ways the pituitary gland is regulated by negative feedback

Answer 22

Hypothalamus secretes H1, causes release of anterior pituitary H2, H2 can feed back to hypothalamus to decrease release of H1 (short loop feedback)

H2 can circulate to an endocrine gland to cause release of an H3, which can feed back to hypothalamus and pituitary to decrease release of H1 and H2 (long loop)

H3 can affect one or more target tissues, whose response can feed back to decrease release of H1 (ultra long loop)

Question 23

Describe regulation of prolactin

Answer 23

Released from AP when PIH levels decrease, suckling causes decrease in PIH to cause secretion of prolactin, when suckling stops PIH levels increase, prolactin levels decrease (short loop)

Question 24

Describe regulation of TSH

Answer 24

TRH (H) causes release of TSH (AP), stimulates thyroid gland to secrete T3 and T4, both feed back to H to decrease TRH release and AP to decrease TSH release (long loop)

Question 25

Describe regulation of GH

Answer 25

GHRH (H) stimulates release of GH (AP) and GHIH (H) decreases it, GH feeds back to H to decrease GHRH release (short loop)

Question 26

Describe regulation of ACTH

Answer 26

CRH (H) released into portal system, causes release of ACTH (AP), which stimulates adrenal glands to secrete cortisol, aldosterone and androgens, cortisol feeds back to both H and AP to decrease CRH and ACTH release (long loop)

Question 27

Describe regulation of FSH and LH

Answer 27

GnRH (H) stimulates release of LH and FSH (AP), travel to gonads (testes or ovaries) to stimulate release of sex hormones, sex hormones feed back to H and AP to inhibit GnRH and LH/FSH (long loop)

Question 28

Describe position of thyroid and general structure

Answer 28

Thyroid gland lies below larynx, consists of two lobes that almost completely surround trachea Made of follicles (functional units of the gland), consisting of central region of colloid surrounded by epithelial cells, between follicles are parafollicular or C cells

Question 29

Describe functions of the thyroid

Answer 29

First organ identified as a gland, produces T3 and T4, both contain iodine, responsible for regulating BMR Made of tyrosine (hydrophobic, requires protein carrier but diffuse through cell membrane) Follicular cells of thyroid produce the protein hormone calcitonin which causes decrease in Ca++ levels in the blood

Question 30

Describe the production of T3 and T4

Answer 30

Produced inside follicles, combine iodine and tyrosine with a glycoprotein thyroglobulin Epithelial cells absorb tyrosine, combine it with thyroglobulin (produced in the cells), absorb iodine from the diet, tyrosine-thyroglobulin complex secretes into colloid, 1-2 molecules of iodine attach to each If 4 attach, T4, if 3 attach, T3

Question 31

Describe secretion of T3 and T4

Answer 31

TSH from AP binds to receptor on membrane of epithelial cell, stimulates multiple reactions: Traps and takes up iodine Stimulates endocytosis of T3 and T4-thyroglobulin complex Enzymatic removal of thyroglobulin from T3 and T4 Stimulates secretion of T3 and T4 into blood

Question 32

Describe regulation of T3 and T4 secretion

Answer 32

T3 and T4 feed back to H and AP to inhibit TRH and TSH (long loop)

Question 33

Describe the circulation of T3 and T4

Answer 33

90% of released thyroid hormones are T4, 10% is T3, both tyrosine based and hydrophobic Even though mostly T4 secreted, much is converted to T3, which is more biologically active than T4

Question 34

Describe the effects of T3 and T4 on the body

Answer 34

Hydrophobic, diffuse through cell membrane, receptors in nucleus of almost all cells, alter transcription of genes for many proteins and enzymes enhancing metabolic activity of the cells T3 and T4 are responsible for regulating body's BMR, and responsible for proper development of the nervous system in the fetus, help maintain alertness, responsiveness, and emotional state

Question 35

Define basal metabolic rate (BMR)

Answer 35

The amount of O2 and energy the body is using at rest, or the least amount of energy a person will use

Question 36

Describe the results of an increase in thyroid hormones

Answer 36

``` Increased body temperature Increased cardiac output Increased ventilation Increased food intake Increased breakdown of energy stores (carbs, fats, proteins) ```

Question 37

Describe goiter

Answer 37

Disease resulting in enlargement of thyroid gland, caused by insufficient iodine in diet or too much TRH/TSH being produced Hypothalamic tumour can cause excess TRH or TSH secretion, causing uncontrollable thyroid growth Without iodine in blood, thyroid unable to produce T3 and T4, and in absence of these, no negative feedback, so TRH and TSH continue being secreted

Question 38

Describe causes of hypothyroidism

Answer 38

Before or after birth and during childhood, insufficient amounts of thyroid hormones result in cretinism (dwarfism and mental retardation), can be prevented with thyroid hormone treatments Can be caused by lack of thyroid gland, inability of gland to produce T3 or T4 due to genetic defect, or lack of iodine in diet

Question 39

Describe symptoms of hypothyroidism

Answer 39

``` Low BMR Sensitive to cold temperatures Weight gain due to decreased fat breakdown and increased fat storage Low blood pressure/weak pulse Slow reflexes, apathy, lethargy Depression Easily fatigued ```

Question 40

Describe hyperthyroidism and symptoms

Answer 40

Excess thyroid hormone secretion ``` High BMR Sensitive to warm temperatures Weight loss due to increased fat breakdown and decreased fat storage Rapid heart rate Hyperactive or "nervous" activity ```

Question 41

Describe calcitonin and its effect on the body

Answer 41

A protein hormone secreted by parafollicular/C cells, which make up 0.1% of thyroid gland Calcitonin helps regulate blood Ca++ levels, secreted when levels rise above normal Decreases activity of osteoclasts (responsible for enzymatically breaking down bone into Ca++ that is released into blood Calcitonin also stimulates secretion of Ca++ into urine Works with parathyroid hormone (PTH)

Question 42

Describe the parathyroid glands

Answer 42

Located on posterior side of thyroid, 4 of them, small, secrete PTH

Question 43

Describe parathyroid hormone and its effects

Answer 43

Secreted when blood calcium levels are low, acting antagonistically to calcitonin Increases number and activity of osteoclasts, releasing calcium into blood Decreases excretion of calcium in urine by reabsorbing it from filtrate Without PTH, kidney would continually excrete Ca++, depleting bones and extracellular fluid of Ca++

Question 44

Describe the location and structure of adrenal glands

Answer 44

One resting on top of each kidney, made of neural and glandular tissue Inner medulla is neural tissue under control of SYN Outer cortex is endocrine under control of PSYN Cortex has 3 layers: outer zona glomerulosa, middle zona fasciculata, inner zona reticularis, each secreting different hormone

Question 45

Describe the function of each adrenal gland region and the hormone it secretes

Answer 45

All cortex hormones are steroid hormones (hydrophobic) Outer zona glomerulosa secretes aldosterone (mineralocorticoid, regulates mineral and fluid volume by kidneys) Middle zona fasciculata secretes the glucocorticoid hormone cortisol (helps in glucose metabolism) Inner zona reticularis secretes small amounts of androgens (sex steroids) Medulla secretes epinephrine/adrenaline

Question 46

Describe the release and effects of epinephrine

Answer 46

Released from medulla when stimulated by SYN, increases heart rate and force of contraction, and increases blood flow to heart and skeletal muscle

Question 47

Describe the release and effects of aldosterone

Answer 47

Secreted in response to Ang II, low Na+ levels and high K+ levels in blood, and ACTH Stimulates reabsorption of Na+ in nephrons

Question 48

List the types of stress that increase cortisol production and secretion

Answer 48

``` Stress: Physical (extreme hot or cold) Physiological (pain, loss of blood, low blood sugar) Emotional (fear or anxiety) Social (personal conflicts) ```

Question 49

Describe how stress stimulates production and secretion of cortisol

Answer 49

Stress stimulates H to secrete CRH, causes AP to secrete ACTH, stimulates adrenal glands to produce cortisol

Question 50

Describe how cortisol has its effects on the cell

Answer 50

Hydrophobic, carried in blood attached to proteins, releases from proteins to diffuse through cell membrane and attach to receptors in the cytoplasm, then translocates into nucleus where it will alter cell activity

Question 51

Describe the rhythmic blood concentration of cortisol

Answer 51

Varies due to the body's circadian rhythm, low most of the day and evening, increases between 2-4am and peaks just before waking

Question 52

Describe how cortisol is involved in glucose metabolism

Answer 52

A glucocorticoid, protects against low blood glucose levels (hypoglycemia), is catabolic (causes breakdown of complex molecules to be used for energy) Will cause breakdown of metabolic substrates like carbs to glucose, proteins to amino acids, fat to fatty acids and glycerol

Question 53

Describe how cortisol effects different tissues

Answer 53

Liver: increases gluconeogenesis (producing glucose molecules from non-carbs like fats and amino acids) Skeletal muscle: decreases protein synthesis and glucose uptake, increases breakdown of proteins Adipose tissue: decreases fat synthesis, increases lipolysis (breakdown of fat except in abdomen and cheeks)

Question 54

Describe Cushing's Syndrome and its symptoms

Answer 54

Disease of the adrenal glands, causes excess secretion of cortisol ``` Wasting of muscles Thin skin Poor wound healing Fat deposits in cheeks and abdomen Depression ```

Question 55

Describe location and structure of the pancreas

Answer 55

Parallel and beneath the stomach Contains endocrine tissue (secretes hormones) and exocrine tissue (secretes chemicals) Endocrine portion consists of 1-2 million pancreatic islets, three kinds: alpha (25%) beta (60%) and delta (10%) Exocrine portion consists of pancreatic acinar cells and ducts

Question 56

Describe insulin and its function

Answer 56

Protein hormone secreted by beta cells Causes cells to rapidly take up, store, and use glucose, decreasing blood glucose levels Secreted when blood glucose levels increase, even small increases in blood glucose cause large amounts of insulin release All cells respond, but liver, muscle and adipose tissue respond best

Question 57

Describe glucagon and its function

Answer 57

Works in opposition to insulin Protein hormone secreted by alpha cells Increases blood glucose concentrations, secreted when blood glucose levels decreases and when amino acid levels in the blood rise Stimulates liver where it causes glycogenolysis (breakdown of glycogen) and gluconeogenesis (formation of new glucose) Secreted during long, exhaustive exercise, up to 4-5x normal amount

Question 58

Describe somatostatin and its function

Answer 58

Somatostatin is also GHIH Protein hormone secreted by delta cells Secreted when blood glucose levels rise, when amino acid levels in the blood increase, and when there is an increase in blood born fats (all related to food ingestion) Primary function is to reduce secretion of both insulin and glucagon

Question 59

Describe blood glucose regulation

Answer 59

Normal: 80-90mg/mL blood Hour after meal, can rise to 120-140mg/mL blood, but once all carbs absorbed, levels return to normal with help of insulin During starvation, glucagon stimulates gluconeogenesis to maintain 80-90mg/mL blood

Question 60

Define diabetes mellitus

Answer 60

A disease involving either the inability of the pancreas to produce insulin or the inability of the target cells to react to insulin in the blood

Question 61

Briefly describe type I diabetes

Answer 61

Insulin-dependent diabetes Involves damage of beta cells leading to lack of insulin production Occurs around 14 (juveniles) Immune system attacks and destroys beta cells Without insulin produced, blood glucose levels can reach 300-1200mg/mL blood Body must rely on fats and amino acids as fuel instead of glucose

Question 62

Briefly describe type II diabetes

Answer 62

Most common, 80-90% of cases Onset often after 40 (adult) Insulin has little effect on body cells, as if resistant to insulin Causes insulin to flood system, depleting beta cells, causing decreased insulin release in later stages of the disease Most patients are obese and can be controlled through diet

Question 63

List symptoms of diabetes

Answer 63

``` Type I diabetes: Increased glucose in urine Increased dehydration Damage to blood vessels Severe metabolic acidosis Depletion of protein stores ``` Type II diabetes: (later stages) Increased glucose in urine Increased dehydration Damage to blood vessels