Endocrine System

Question 1

What are the differences between endocrine and exocrine glands?

Answer 1

Exocrine - Body surface (gets put out into body surface)

Endocrine - Secrete’s hormones directly into blood vessel, into blood stream (hormones travel the blood to get to target)

Question 2

What are the body’s endocrine glands?

Answer 2

PRIMARY:
Thyroid
Parathyroid
Anterior & Posterior pituitary gland (Master endocrine gland)
Adrenal Glands
Pancreas (dual)

SECONDARY:
Ovaries & Testies
Hypothalamus
Heart
Liver
Kidneys
Blood Vessels
Adipose Tissue
Pineal
Stomach and Small Intestine

Question 3

Major classes of hormones

Answer 3

Amine Hormones: come from amino acids (small)
Thyroid hormones: Thyroxine, Triiodothyronine
Catecholamines: Norepinephrine, Epinephrine

Peptide Hormones: amino acid chains
ACTH (adrenocorticotropic hormone)
HGH (Human growth hormone)

Steroid Hormones: Made from cholesterol
Cortisol (stress)

Question 4

How are peptide and protein hormones synthesized?

Answer 4

Preprohormone -> Prohormone -> Hormone

Question 5

How are steroid hormones synthesized

Answer 5

Receive signal to make hormone -> Activates Proteins -> Takes cholesterol -> converts to Final Steroid hormone -> directly diffuses into blood stream (slips through membrane)

CAN NOT BE STORED

Question 6

Examples of steroid hormones
(not as important, know how it all can be connected)

Answer 6

Cholesterol ->
Androgens (Masculine associated effects):
With Aromatase -> estrogens

Corticosterone & Cortisol: stress hormones

Aldosterone: Sodium regulation
Progesterone

Question 7

Why and how are hormones removed from circulation?

Answer 7

To prevent oversignaling (like removing neurotransmitters)

Excretion by urine
Inactivated by metabolism
Activated by metabolism, binds to target cells -> More metabolism inactivates, excretion

Question 8

How do different types of hormones have their effect on a target cell?

Answer 8

Nonsteroid hormone: second messenger

Steroid hormone: Changes gene transcription

Question 9

Target specificity

Answer 9

Target cell: has the receptor for the hormone

Non-target cell: do not have the receptor

Question 10

Target Sensitivity

Answer 10

Upregulation: Increase target sensitivity by putting more receptors

Downregulation: Decrease target sensitivity by decreasing # of receptors

Question 11

Permissive Action

Answer 11

The impact one hormone has on another

Example: Thyroid hormone has permissive effect on epinephrine, allowing a large amount of fatty acids to be released in adipose cell.

How? Increase B adrenergic receptors.
Effect: Thyroid hormone -> Increase B adrenergic receptors -> Makes cell more sensitive to epinephrine

Question 12

How do ions control hormone release?

Answer 12

Example: Increase in glucose causes increase in insulin.

so decrease in glucose decreases insulin

Question 13

How do neurons control hormone secretion?

Answer 13

Central Nervous System:

Directly stimulates endocrine gland

Neuron releases hormone (tropic hormone) causes stimulation of gland

Neurohormone released directly by neuron (Neuron releases the hormone)

Question 14

How do tropic hormones control hormone secretion?

Answer 14

Tropic hormone - Influences release of another hormone

Question 15

Endocrine Disorders

Answer 15

2 basic categories of symptoms, caused by 3 different causes each

Too Much Hormone vs Too Little Hormone

Primary Hypersecretion, Primary Hyposecretion, Secondary Hypersecretion, Secondary Hyposecretion, Hyper Responsiveness, Hypo Responsiveness

LEARN HORMONE, TROPIC HORMONE, AND RECEPTORS INCREASING OR DECREASING

Question 16

Hypothalamus & Posterior Pituitary relation

Answer 16

Hypothalamus (neural circuit) - involved in homeostasis.

Infundibulum (connecting spot) takes neurons and blood vessels from the brain to the pituitary

POSTERIOR PITUITARY : Neural tissue & blood vessels
Everything that happens from posterior pituitary is originating in the hypothalamus

Question 17

Functions of Posterior Pituitary Hormones

Answer 17

Oxytocin: Uterine muscles, mammary glands -> Reproductive Chapter

ADH (Antidiaretic hormone/Vasopressin) -> Blood pressure regulation -> Renal Chapter

Question 18

Hypothalamus & Anterior Pituitary

Answer 18

Infundibulum -> Median Eminence -> Dumps neurohormones (tropic hormones) into Hypothalamo-hypophyseal portal vessels -> Tropic hormones cause change in hormone secretion -> Release hormones into blood stream

Question 19

Anterior Pituitary Gland Hormones

Answer 19

Endorphins - Decrease pain perception
Prolactin - Prepare for lactation
Growth Hormone - Growth and Development
FSH and LH (Gonadotropins) - Produce sperm & ova
ACTH (adrenocorticotropic hormone) - Stress response
TSH (Thyroid stimulating hormone) - Increase thyroid hormone

Question 20

Hormones and what they cause

Answer 20

CRH -> ACTH
TRH -> TSH
GHRH -> GH
GnRH -> LH and FSH
SST -> Inhibits GH
Dopamine -> Inhibits Prolactin
Prolactin -> Inhibits FSH and LH, and GnRH

Question 21

How is Hormone release by hypothalamus and anterior pituitary gland controlled?

Answer 21

Stimulus (stress) -> CRH -> hypothalamo-hypophyseal portal vessels -> ACTH -> throughout the body (general circulation) -> Cortisol (prevents hypersecretion) -> Targets cells for stress response

Question 22

What are the pathways controlling release of growth hormones

Answer 22

Stimulus -> Hypothalamus (GHRH secretion, and decrease in somatostatin) -> Hypothalamo-hypophyseal portal vessels -> Anterior pituitary (increase GH secretion) -> General circulation -> Liver and other cells (increase in insulin like growth factor) -> Increase growth -> Increase bone length and increase protein synthesis

Question 23

Feedback loop for growth hormone

Answer 23

Insulin like growth factor - 1: stimulates GHRH, stimulates SST
GHRH stimulates GH
SST inhibits GH
GH simulates Insulin like growth factor - 1

Question 24

Abnormal growth hormone secretion

Answer 24

DURING CHILDHOOD ADOLESCENCE
Too little GH - Pituitary Dwarfism
Too much GH - Pituitary Gigantism
DURING ADULTHOOD
Acromegaly - Too much GH causes face to thicken, bones in face and hands and feet grow.

Question 25

Other hormones affecting growth

Answer 25

Postnatal: Growth Hormone - Stimulates liver to secrete IGF - 1, stimulates protein synthesis
Prenatal: Insulin - Fetal growth, little bit of postnatal growth
Thyroid hormone - Increase GH receptors (permissive action)
Testosterone, Estrogen - Puberty growth, stimulates secretion of GH, causes a burst of growth, then a cessation of growth
Cortisol - Inhibits growth, stimulates protein catabolism (breaking down) allows us to regulate growth speed

Question 26

Location and structure of the thyroid gland

Answer 26

Follicular cells - thyroid hormone
Follicle Lumen - colloid, protein rich tyrosine
Thyroid follicle - made up of follicular cells and follicle lumen
Parafollicular cells - c cells - make calcitonin

Question 27

How are thyroid hormones synthesized?

Answer 27

1. Iodide is cotransported with Na+
2. Diffusion through the follicle cell into the lumen (colloid)
3. Iodide attaches to the ring in tyrosine (Thyroglobulin)
4. The iodinated ring is added to another ring. (T3, or T4)
5. Endocytosis of thyroglobulin containing T3 and T4 molecules
6. Lysosome added, releasing T3 and T4
7. T3 and T4 secretion (diffuses lipophylic)

T3 form is more active
T4 form is less active

Thyroid hormone cant be stored

Question 28

Thyroid Process how is it controlled

Answer 28

Hypothalamus -> Hypothalamo - hypophyseal portal vessels -> Anterior Pituitary (TSH secretion)-> general circulation -> Increase thyroid hormone secretion -> General circulation -> Target cells cell response

Question 29

What are the effects of Thyroid hormone

Answer 29

Increased metabolism
Increase IGF - 1 & protein synthesis
Increase dendrite and axon growth & synapse formation
Increased catecholamine effect
Increase in B adrenergic receptors (epinephrine)

Question 30

What are the symptoms of Hypothyroidism

Answer 30

Decreased Metabolic rate
Decreased catacholamine effects
Myxedema - build up of glycosaminoglycons in the interstitual fluid
Goiter - enlarged thyroid gland - Primary hyposecretion

Question 31

Hyperthyroidism

Answer 31

Increased metabolic rate
Increased appetite
Increased catecholamine effect
Decrease in free testosterone
Myxedema - prolonged hyperthyroidism
Goiter - overstimulating and overproducing

Question 32

What hormones do the medulla and cortex of the adrenal glands secrete?

Answer 32

Medulla -> Epinephrine and Norepinephrine
Cortex -> 3 layers, each produce different hormones
Aldosterone (blood Na control)
Cortisol & small amount of androgens
Androgens & small amount of cortisol

Question 33

What is the HPA axis and how does it help the body deal with stress?

Answer 33

HPA axis - Hypothalamic Pituitary Adrenal axis

Permissive effect on catecholamines
Inhibits inflammation and specific immunity
Permissive effect on growth hormone
Inhibits non essential functions

Question 34

How does negative feedback control activity of the HPA axis?

Answer 34

Hypothalamus (increase CRH secretion) -> Hypothalamo - hypophyseal portal vessels -> Anterior pituitary (increase ACTH secretion) -> general circulation -> Adrenal cortex (increase cortisol secretion) -> General circulation -> Response to increase cortisol.

Increase cortisol causes negative feedback for ACTH and CRH secretion.

Question 35

What are the symptoms of insufficient cortisol production

Answer 35

Less sensitive to epinephrine
Decrease Liver function
Weakness
Weight loss
Addisons disease (bronze pigmentation and changes in body hair)

Question 36

What are the symptoms of excess cortisol production

Answer 36

Decreases immune system
Decreased catecholamine permissive effect
Inhibition of nonessential functions
Increase energy mobilization and disregulation in fat storage
Increase androgens
Cushings disease (tumor)