IC 1: Endocrine system Flashcards
What is the difference between the endocrine system and nervous system?
Endocrine system: Slow acting hormone messengers; Nervous system: fast acting electrochemical impulses delivered by neurons
Endocrine system: Regulation activities that require duration rather than speed to maintain homeostasis; Nervous system: regulates activity of muscles and glands, short term
What is the definition of hormones?
They are substances released by endocrine glands and transported throughout the blood stream to target tissues where they act to regulate specific functions. They provide long distance signaling
Endocrine glands are large and have ducts. True or false
False. Endocrine glands are very small and ductless.
What is the issue with estrogen disrupters?
They mimic the activity of estrogen in body cells, which increases the incidence of breast tumours in females and leads to falling sperm count, cryptorchidism (undescended testis) in males. There is also gender bending in animals (e.g. male fish having both male and female reproductive parts)
What are 2 ways hormones can be classified?
- Based on endocrine gland that releases that hormone
2. Based on chemical nature of hormones
Name the hormones that are released by the gonads and their chemical nature (type of molecule).
Testis: Testosterone, estradiol, inhibin, MIH
Ovary: Estradiol, progesterone, inhibin
They are all steroids except inhibin being a protein and peptide
What hormones are hydrophilic and what are hydrophobic?
All proteins and peptide hormones are hydrophilic, all steroid hormones are hydrophobic, T3, T4 and melatonin are hydrophobic amines and catecholamines, epinephrine and norepinephrine are hydrophilic amines.
Why do the hydrophilic or hydrophobic nature of hormones matter?
Hydrophilic hormones can be dissolved and transported free in blood while hydrophobic hormones will be bound to plasma proteins, affecting it’s physiologic effect
What is the difference between cell membrane receptors and intracellular receptors? Name the types of hormones that bind to the respective receptors.
Cell membrane receptors: Bind to cell surface receptor on target cell. Protein hormones, catecholamines (hydrophilic)
Intracellular receptors: Cross the plasma membrane and act on receptors inside the target cell. Steroid hormones, thyroid hormones (hydrophobic)
What are the possible effects of hormone binding to the receptor?
- Alters channel permeability by acting on pre-existing channel-forming proteins
- Acts through second-messenger system to alter activity of pre-existing proteins
- Activates specific genes to cause formation of new proteins
Why do hormone imbalances occur and how do we measure hormone levels in the body?
They occur as a result of excess or deficiency/decreased secretion of hormones or excess or deficiency/decreased target-cell responsiveness. We can measure hormone levels in the body by blood, urine, saliva and other biological samples like tissue.
How is the secretion of hormones regulated in the hypothalamic-pituitary axis?
It is regulated by negative feedback there is a feedback loop when too much of a hormone is released.
Where is the thyroid gland located?
It is located in the neck, on the anterior surface of trachea, immediately below the larynx.
How many lobes do the thyroid gland contain?
2 lobes and they are connected by isthmus
What are the basic ingredients required for thyroid hormone synthesis?
Tyrosine which is an amino acid synthesised by the body and iodine that is obtained by dietary intake. Dietary iodine is reduced to iodide to be absorbed in the small intestine
