Midterm 1: Endocrine System

Question 1

Functions of Endocrine System

Answer 1

• regulate development, growth, and metabolism
• maintain blood composition and volume
• control digestive and reproductive activities.

Question 2

Glands of the Endocrine System

Answer 2

Adrenal Cortex and Medulla
Thymus 
Thyroid
Parathyroid
Pineal
Pituitary

Question 3

Organs/Tissues that contain Endocrine Cells

Answer 3

• Adipose
• Digestive System (stomach, small intestine, liver, pancreas)
• Gonads
• Heart
• Hypothalamus
• Kidney
• Skin

Question 4

Differences between endocrine, paracrine, and autocrine receptors

Answer 4

Endocrine receptors has to do with hormones traveling to a distant part of the body. Paracrine is associated with local transmission of hormones. Autocrine receptors are associated with the same cell that secretes the hormone.

Question 5

Circulating Hormones & examples

Answer 5

Hormones that travel a longer distance and bind to endocrine receptors. Ex. biogenic amines, peptides/proteins, and steroids

Question 6

Local hormones & Examples

Answer 6

Hormones that bind with paracrine receptors and are short lived. Ex. Eicosanoids (prostaglandins, thromboxanes, leukotrienes) that are derived from arachidonic acid.

Question 7

What are the 3 classes of circulating hormones?

Answer 7

• Biogenic amines
• peptides/proteins
• steroids

Question 8

Characteristic of Biogenic amines & examples.

Answer 8

Water soluble (except thyroid hormone) and derived from the amino acid tyrosine.

Ex.

• Norepinephrine, epinephrine (catecholamines)
• Thyroid hormones

Question 9

Characteristics of peptide/protein hormones & examples

Answer 9

All water soluble and derived from amino acid chains.

Ex. 
ADH/Vasopressin
Atrial natriuretic peptide (ANP)
Erythropoietin (EPO)
Growth hormone
Insulin/glucagon
Parathyroid hormone (PTH)

Question 10

Characteristics of steroids & examples

Answer 10

All lipid soluble and formed from cholesterol.

Ex.

• Sex hormones (testosterone, estrogen, progesterone)
• Cortisol
• Aldosterone
• Calcitrol

Question 11

True or False:

All hormones that are soluble in blood are free hormones.

Answer 11

False. There are a few water-soluble hormones that are protein bound.

Question 12

Free vs. Bound hormones

Answer 12

Free hormones are soluble in blood.
Water-soluble hormones (first messenger) bind to plasma membrane receptor, triggering a series of events (i.e., activation of G-proteins, second messengers) across the cell membrane that will ultimately stimulate the target cell

Bound hormones are lipid-soluble and bound to proteins. Since they are lipid soluble, they can pass through pass through the cell membrane and interact with intracellular receptors.

Question 13

General description and location of thyroid gland

Answer 13

• Butterfly-shaped bi-lobed gland located in the anterior neck, lower cervical
• Right and left lobes connected midsagittal by the isthmus
• Positioned behind the sternohyoid and sternothyroid muscles (both are infrahyoids)
• Wraps around cricoid cartilage & superior tracheal rings
• Parathyroid glands located on posterior surface

Question 14

Vasculature of thyroid

Answer 14

1) Superior thyroid -receives blood from the external carotid a. (first branch of the external carotid) and supplies superior-anterior portion of gland.
2) Inferior thyroid- receives blood from thyrocervical trunk (a branch of subclavian) and supplies remainder of gland
3) Superior and middle thyroid- drain into the internal jugular
4) Inferior thyroid- forms a plexus and has anastomoses with the superior and middle thyroid; typically drains into the (left) brachiocephalic v.

Question 15

Autonomic innervation of the thyroid

Answer 15

• Sympathetic innervation via cervical ganglia

- Parasympathetic innervation via branches of the vagus n. (CN X)

Question 16

Describe the glands of the thyroid.

Answer 16

Contain 20-30 million spherical follicles that have a cavity in the middle lined with simple cuboidal epithelium cells called follicular cells. The cavity is made up of the thyroglobulin (glycoprotein) and oxidized iodide that are secreted from the follicular cells.

Question 17

Throid-stimulating hormone (TSH)

Answer 17

Secreted from the anterior pituitary. Stimulates secretion of T3 (most active form of thyroid hormone) and T4 (highest plasma concentration of the two)

Question 18

Why is thyroglobulin important in the thyroid gland?

Answer 18

Thyroglobulin (specifically its tyrosine residues) and iodine are initial building blocks for the synthesis of T3 (triiodothyronine) and T4 (thyroxine)

Question 19

Parafollicular cells (C cells)

Answer 19

Responsible for the synthesis and secretion of the peptide hormone calcitonin in response to an elevated blood calcium concentration. Larger than follicular cells and have a lighter staining nucleus.

Question 20

What does calcitonin do? Where is it secreted from?

Answer 20

Calcitonin lowers blood calcium levels by inhibiting bone reabsorption.

Question 21

General description and location of the parathyroid gland

Answer 21

Small, paired (superior and inferior) ovoid-shaped structures on posterior surface of thyroid

Not regulated by pituitary unlike the thyroid.

Question 22

True or False:

The vasculature and the innervation of the thyroid and parathyroid are the same.

Answer 22

True

Question 23

Describe the cells/hormones of the parathyroid and explain the role they have.

Answer 23

Chief (principal) cells are the most numerous cell in parathyroid and they secrete parathyroid hormone. Parathyroid hormone acts as an antagonist of calcitonin. Parathyroid hormone increases plasma calcium levels in 3 different ways.

1) increasing calcium reabsorption from bone
2) Increased reabsorption of calcium from kidneys
3) calcitrol formation in kidneys by activating enzyme. This then secretes calcitriol secretion from the kidneys which increases absorption from the small intestine.

Oxyphil (eosinophil) cells are larger than chief cells and first appear at puberty and increase with age. function is uncertain.

Question 24

General description and location of Pituitary Gland

Answer 24

Bi-lobed gland (1cm diameter) suspended from the hypothalamus via the pituitary stalk (infundibulum).
Gland positioned within the sella turcica of the middle cranial fossa.
Carries out the functions of the hypothalamus that controls other glands and tissues in the body.

Anterior & inferior: Sphenoid sinus

Anterior only: Anterior intercavernous sinus

Posterior: Posterior intercavernous sinus; basilar artery/pons

Superior: Diaphragm sellae (dura mater deflection); optic chiasm

Lateral: Cavernous sinus

Question 25

6 primary anterior pituitary hormones

Answer 25

``` FSH LH Growth hormone TSH Prolactin ACTH ```

Question 26

Describe the anterior lobe of the pituitary gland and its interaction with the hypothalamus.

Answer 26

Largest lobe by volume (75%). Secretes prolactin, gonadotropins, growth hormone, thyroid stimulating hormone, and adrenocorticotropic hormone. The hypothalamus influences the anterior pituitary by secreting regulatory hormones that act on specific anterior pituitary receptors via hypothalamic-hypophyseal portal system. (not a neural influence)

Question 27

Prolactin

Answer 27

stimulates milk production from mammary glands. Can be stimulated by estrogen and other factors

Question 28

Dopamine effects on prolactin

Answer 28

Dopamine is prolactin's hypothalamic regulator. It inhibits secretion.

Question 29

2 types of gonadotropins and their function

Answer 29

1) Follicle-stimulating hormone (FSH)- drives oogenesis (female) and spermatogenesis (male) 2) Luteinizing hormone (LH): Synthesis of progesterone and androgens (testosterone) , androgens converted to estrogens (estrone and estradiol) by the aromatase enzyme

Question 30

True or False; | Growth Hormone is the only hormone that stimulates growth.

Answer 30

False. Insulin, thyroid hormones, sex hormones, and cortisol also stimulate growth.

Question 31

Describe how growth hormone works. When is secretion increased/ decreased?

Answer 31

GH and IGF-1 directly drives lipolysis in adipocytes where liberated glycerol can be converted to glucose in the liver for use as an energy source via gluconeogenesis and fatty acids can be utilized as an energy source in most tissues. GH secretion greatest during non-REM sleep (earlier in sleep cycle) and during intense exercise. GH secretion decreases with age and increases with increased nutrients in the plasma

Question 32

Describe what growth hormone stimulates.

Answer 32

GH stimulates liver hepatocytes to secrete insulin growth factor (IGF-1), the major driver of growth secondary to the effects of GH and stimulates the conversion of glycogen to glucose (glycogenolysis) and glycerol (directed from the adipocytes after lipolysis) to glucose via gluconeogenesis for use as an energy source

Question 33

Thyroid-Stimulating Hormone (TSH)

Answer 33

binds to external receptors of thyroid follicular cells that stimulates follicular synthesis and secretion of the thyroid hormones, T3 and T4

Question 34

Adrenocorticotrophic Hormone (ACTH)

Answer 34

acts as regulatory hormone for glucocorticoid secretion (i.e., corticosterone, cortisol) from adrenal medulla (zona fasciculata)

Question 35

Intermediate lobe & Proopiomelanocortin (POMC)

Answer 35

Intermediate lobe is considered part of the anterior pituitary but does not have much vascularization. POMC is released here generates several peptides via post-translational modification including the opioids endorphins and enkephalins as well as ACTH and melanocyte-stimulating hormone (MSH)

Question 36

Describe Pineal gland

Answer 36

Located in epithalamus immediately posterior to thalamus Secretes hormone melatonin which regulates the body clock (Circadian rhythm) Believed to regulate reproduction by regulating FSH and LH from the anterior pituitary

Question 37

What does FSH control?

Answer 37

FSH controls development of ova in females and sperm in males

Question 38

What does LH control?

Answer 38

LH stimulates ovulation in females and triggers the production of testosterone in males

Question 39

What does melatonin do? What do low levels in younger people cause?

Answer 39

Regulate sleep cycle. Low levels delay the onset of puberty

Question 40

General description and location of adrenal glands

Answer 40

Small, flattened endocrine glands located at the superior poles of each kidney and surrounded by a fibrous capsule. The outer adrenal cortex is under pituitary control and secretes steroid hormones. The inner adrenal medulla, under sympathetic control and is embryologically like the sympathetic NS.

Question 41

Vasculature of adrenal glands

Answer 41

Arteries: Superior, middle and inferior suprarenal Venous: Suprarenal

Question 42

Adrenal cortex sections

Answer 42

``` Zona glomerulosa (outer) Zona Fasiculata Zona Reticularis (inner) ```

Question 43

Zona glomerulosa in adrenal cortex secretes ___________.

Answer 43

Mineralocorticoids (Aldosterone)

Question 44

Zona fasiculata in adrenal cortex secretes __________.

Answer 44

Glucocorticoids (Cortisol)

Question 45

Zona reticularis in adrenal cortex secretes ___________.

Answer 45

Androgens

Question 46

Adrenal Medulla composition

Answer 46

Comprised of specialized sympathetic neurons (that first pass through the adrenal cortex) called chromaffin cells; these cells secrete mainly epinephrine, but also secrete norepinephrine.

Question 47

What do chromatin cells secrete?

Answer 47

secrete mainly epinephrine but also secrete norepinephrine

Question 48

Where are glucocorticoids (cortisol) secreted and what are its functions?

Answer 48

Secreted in zona fasiculata of the adrenal cortex. It decreases events associated with the inflammatory response such as capillary permeability and production of prostaglandins. Suppression of the immune response. Increased water and sodium retention. Epinephrine/norepinephrine release from adrenal medulla. Cortisol, as a glucocorticoid, maintains enzymes needed for glucose production in the post-absorptive state (between meals) and, therefore, is essential in maintaining plasma glucose concentration (increased gluconeogenesis and lipolysis)

Question 49

Why is cortisol important for blood sugar levels?

Answer 49

Cortisol, as a glucocorticoid, maintains enzymes needed for glucose production in the post-absorptive state (between meals) and, therefore, is essential in maintaining plasma glucose concentration (increased gluconeogenesis and lipolysis)

Question 50

What is the posterior lobe called on pituitary gland? What does it contain? Describe the hormones secreted here.

Answer 50

Neurohypophysis. Contains the infundibular process and stem along with the medial eminence of the hypothalamus. Hormones secreted from this gland are mainly synthesized in the hypothalamus and stored in the posterior pituitary until their release on command. Release hormones vasopressin/ antidiuretic hormone (ADH) and oxytocin. Vasopressin/Antidiuretic hormone (ADH) controls blood osmolarity Hypothalamic diabetes insipidus secondary to insufficient ADH secretion Nephrogenic diabetes insipidus secondary to kidneys inability to respond to ADH. Oxytocin is involved in childbirth (uterine contractions) and milk ejection from the mammary glands by contraction of myoepithelial cells around alveoli.

Question 51

Arterial vasculature of the anterior pituitary.

Answer 51

Internal carotid artery → superior hypophyseal artery The superior hypophyseal artery supplies arterial blood to the capillary net around hypothalamus. This capillary net communicates with another capillary net around the anterior pituitary via a group of small veins to form the hypothalamic-hypophyseal portal system.

Question 52

Arterial vasculature of the posterior pituitary.

Answer 52

Internal carotid artery → superior hypophyseal artery → infundibular artery → inferior hypophyseal artery.

Question 53

Venous drainage of lobes in the pituitary

Answer 53

Same drainage for both lobes. | Anterior and posterior hypophyseal vv. → cavernous sinus

Question 54

Cellular histology of pituitary gland

Answer 54

The anterior pituitary contains chromophils, more specifically acidophils and basophils and each cell type synthesizes and secretes specific hormones. The posterior pituitary contain specialized glial cells called pituicytes as well as nerve fibers containing hormones stored in the nerve endings.