The Endocrine System

Question 1

• Classification of hormones by chemical structure

Answer 1

• peptide hormone
  
  • varying sizes
  • derived from polypeptides
  • binds receptor → signal transduction → secondary messenger
    - possibility of amplification; increase signal intesity by producing alot of second messengers (i.e cAMP, IP3, Ca++)
    - Type of receptor determines the subsequent signaling cascade.
    - short-lived effect without constant stimulation.
• Steriod hormone
  - organs( gonads/ adrenal cortex) → hormone( cholesterol derivatives)→ intracellular or intranuclear receptor → receptor binds DNA → alter gene expression
  - long-lived effect
  - inactive while carried in blood by albumin or globulin
• Amino acid-derivative hormone

    - includes epinephrine, norepinephrine, triiodothyoxine, and thyroxine
    - epinephrine and norepineprhine(catecholamines) bind extracellulary GPCR
    - Thyroxine bind intracellullary

Question 2

Classification of hormones by target tissue

Answer 2

• direct hormones
  - Hormone → taget tissue → effects.
  - (i.e insulin → target tissue)
• tropic hormones
  - Hormone → endrocrine gland hormone → target tissue → effect
  - (i.e Thyroid Stimulating Hormone → Thyroid gland → thyroid hormone → target tissue )
  - typically originate from brain and anterior pituitary.

Question 3

• Hypothalamus

Answer 3

• Produces somatostatin → ↓GH secretion
  
  • bridge b/w nervous and endocrine system
  • regulates pituitary through paracrine signaling
  • regulated by negative feedback

Question 4

interactions of Hypothalamus with the Anterior Pituitary

Answer 4

• utilizes hypophyseal portal system (blood vessel system)
  - hypophysis: alternative term for pituitary
  - hypothalamus tropic hormone → anterior pituitary → stimulate hormone release
  - GnRH → FSH and LH
  - GHRH → GH
  - TRH → TSH
  - CRF → ACTH → cortisol ⤼ hypothalamus / anterior pituitary
  - hypothalamus hormone → anterior pituitary → inhibiting hormone release
  - PIF → no prolactin

Question 5

Interactions of Hypothalamus with the Posterior Pituitary

Answer 5

• hypophyseal portal system
  - release oxytocin ( uterine contractions, lactation )and antidiuretic (water reabsorption)
  - stimulated by increased plamsa osmolarity

Question 6

• Anterior pituitary

Answer 6

• Tropic hormones
  - 4 types (FSH, LH, ACTH,TSH)
  - FSH and LH → gonads and testes
  - ACTH → adrenal cortex
  - TSH → thyroid
• Direct hormones
  - 3 types (prolactin, endorphins, GH)
  - dopamine from hypothalamus → anterior pituitary → ↓ Prolactin secretion → ↓ milk production
  - endorphins → no pain
  - GH → bone and muscle growth, and raise blood sugar
  - excess amount → gigantism (children) or acromegaly (adults)
  - deficient amount → dwarfism

Question 7

Posterior Pituitary

Answer 7

• Uses a neuron to communicate with hypothalamus
  
  • Low blood → ADH → Renal water permeability → increased BP and volume
  • Uterine child birth / breast suckling →oxytocin → muscle contractions →positive feedback pathway

Question 8

• Thyroid

Answer 8

• Controlled by TSH
  
  • Two functions:
    
    • Setting metabolic rate
    • Calcium homeostasis

Question 9

• Triiodothyroine (T3) and Thyroxine (T4)

Answer 9

• Produced by follicular cells
  - Product of iodination of tyrosine
  - resets metabolic rate
  - Controls energy sources
  - Controls energy production efficiency
  - Increased amounts → increased respiration → increased protein and FA turnover
  - Negative feedback pathway
  - low iodine→ low T3 & T4 → Hypothyroidism → lethargy, weight gain, decreased respiration etc (cretinism in children seen as mental retardation and short stature)
  - Tumor → High plasma T3 &T4 → hyperthyroidism → high energy, increased body temp, heat intolerance

Question 10

• Calcitonin

Answer 10

• Produced by parafollicular cells (C-cells)
  - Decreases circulating calcium
  - kidney secretion
  - Gut absorption
  - Bone storage

Question 11

• Parathyroid Glands

Answer 11

• Produces PTH (parathyroid hormone)
  
  • Antagonistic to calcitonin
    
    • (PTH → increase blood calcium → negative feedback)
  • PTH → bone phosphate resorption and ↓kidney reabsorption → urine secretion.
  • PTH → vitamin D activation → ↑gut Calcium and phosphate absorption

Question 12

• Adrenal Cortex Secretes 3 classes of corticosteroids:

Answer 12

• glucocorticoids
  - Mineralocorticoids
  - Cortical sex hormones

Question 13

glucocorticoids

Answer 13

Types:
-Cortisol (steroid stress hormone)
-Cortisone
CRF → ACTH → glucocorticoids → ↑Blood sugar and ↓inflammation

glucose levels (↑gluconeogenesis)

Question 14

Mineralocorticoids

Answer 14

Type:

     - aldosterone  - Maintains salt and water homeostasis  - ↓ BP → Renin from baroreceptors  → angiotensinogen → angiotensin I → angiotensin II → adrenal cortex → Aldosterone secreted  → Nephron salt reabsorption → water reabsorption  → ↑BP and pressure
        - Aldosterone secreted → K+  and H+ excretion

Question 15

Cortical sex hormones

Answer 15

Types:

    - Androgens 
    - Estrogen  - Largely affects women when in excess

Question 16

Adrenal Medulla

Answer 16

• Derivative of nervous system (sympathetic like fight-or-flight responses)
  
  • Hormone types
    
    • epinephrine (catecholmanine) → increase glycogenolysis, metabolism, vascular dilations → increase blood glucose
    • Norepinephrine (catecholamines)
  • Stimulated by cortisol to secrete epinephrine.

Question 17

Pancreas

Answer 17

• Exocrine functions: digestive enzymes
  
  • Endocrine functions: through islets of langerhan
• Glucagon from alpha cells
  - During fasting
  - Low blood sugar or presence of gaskin and cholecystokinin → glucagon secreted → protein, fat , glycogen breakdown
• Insulin from beta cells
  - During fed state
  - High blood sugar → insulin secreted → glucose intake, stimulate anabolic processes
  - Hypoglycemia when overused
  - Hyperglycemia when underused or not excreted ( diabetes) → polyuria (excess urination) and polydipsia (increased thirst)
  - Diabetes types
  - Type I
  - beta cells destroyed → no insulin secretion → no glucose intake
  - Synthetic insulin needed
  - Type II
  - Insensitive receptors → ↓glucose intake
  - Pills and/ or synthetic insulin needed.
• Somatostatin from delta cells
  - Inhibitor of insulin and glucagon
  - High glucose and amino acid conc. → somatostatin secreted → ↓GH secretion and inhibit insulin and glucagon

Question 18

endocrine signals from pancreas

Answer 18

• Glucagon from alpha cells
  - Insulin from beta cells
  somatostatin from delta cells

Question 19

• Gonads

Answer 19

• LH and FSH → Testes → Testosterone → sexual differentiation and secondary sex characteristics maintainance
  
  • LH and FSH → Ovaries → estrogen and progesterone → reproductive system and secondary sex characteristic development

Question 20

Pineal gland

Answer 20

• synthesizes and secretes melatonin
  
  • Melatonin influences circadian rhythm
  • Influenced by light

Question 21

examples of peptide hormones

Answer 21

InsulIN
OxytocIN
ProlactIN
VasopressIN
SomatostatIN
*NOTE: they ending is 'IN' but there are exceptions such as ACTH and Glucagon.****

Question 22

Hormones derived from cholesterol

Answer 22

Aldosterone
Estrogen
Progesterone.
Testosterone

Question 23

ADH

Answer 23

increases permeability of renal collecting duct
increases reabsorption of water
increases blood volume

Question 24

Renin

Answer 24

Released by Juxtaglomerulus apparatus
in times of 
     decrease BP, 
     sympathetic system activation, 
     decreased sodium at Macula densa located in distal convoluted tubule.

Question 25

Aldosterone

Answer 25

Released by adrenal cortex

Triggered release by Angiotensin 2 (during low BP) and Increase in potassium concentration.

Used to:
increase blood pressure
decrease blood potassium levels at the renal duct by utilizing sodium potassium pump to exchange potassium for sodium so then there’ll be increased sodium in blood.and thereby water through osmosis.