U2L5: Endocrine System

Question 1

Compare the Nervous System and Endocrine System

Answer 1

The nervous system communicates with electrical impulses and neurotransmitters, it reacts quickly to stimuli, stops quickly when stimulus stops, adapts relatively quickly to stimulation, and has specific effects on target organs.

The endocrine system communicates with hormones carried in blood, it
reacts more slowly to stimuli, may continue responding long after stimulus stops, and has very general effects on many organs in the body.

Question 2

What is Paracrine signalling?

Answer 2

cell-to-cell communication in which a cell releases a chemical messenger, causing changes in nearby cells.

Question 3

What is Endocrine signalling?

Answer 3

signals (hormones) produced in one part of the body travel through circulation to reach far-away targets.

Question 4

What is the endocrine system composed of?

Answer 4

The endocrine system comprises of all hormone secreting cells and glands in the body and is typically slower/has longer acting effects on the body.

Question 5

What are lipid (steroid) hormones?

Answer 5

They can diffuse directly into cells through lipid bilayer. Once in the cell, lipid hormones bind to receptor proteins which activates specific genes. Ex: estrogen, progesterone, testosterone, aldosterone.

Question 6

What are peptide (Water soluble) Hormones?

Answer 6

They cant diffuse through lipid bilayer. Attach to receptor protein on cell membrane and signals a cascade of events to activate certain enzymes or effector molecules. Ex: epinephrine, norepinephrine, Thyroid-stimulating hormone (TSH), human growth hormone (hGH).

Question 7

Whats an example of Human Growth Hormone (hGH)?

Answer 7

The world’s tallest man (2.36m or 7”7). He has excessive hGH secreted by pituitary gland during childhood.

Question 8

What is an example of Thyroid Gland & Feedback?

Answer 8

• The thyroid gland secretes triiodothyronine & thyroxine (T3 & T4) which helps the body metabolize fats, proteins, and carbohydrates
• Thyroxine (T4) is controlled via negative feedback. This is because the anterior pituitary releases TSH (thyroid stimulating hormone) which causes the thyroid gland to release thyroxine. As thyroxine levels in the blood increase, the hypothalamus & anterior pituitary notice this and they stop the production of TSH.

Question 9

Explain reproductive hormones for the male reproductive system

Answer 9

1) Hypothalamus releases GnRH (gonadotropin-releasing hormone)
2) This signals the pituitary gland in brain to release LH (luteinizing hormone) and FSH (follicle stimulating hormone)
3) LH stimulates the production of testosterone and testosterone stimulates the production of sperm
4) FSH stimulates production of molecules needed in spermatogenesis
POSITIVE FEEDBACK: FSH initiates spermatogenesis and LH signals the release of testosterone.
NEGITIVE FEEDBACK: When testosterone levels are too high, GnRH, LH, and FSH are inhibited.

Question 10

What is a Menstrual Cycle?

Answer 10

It is a monthly cycle of events in a sexually mature female which prepares the uterus for implantation of a fertilized egg.

Question 11

What is the Endometrium?

Answer 11

The tissue lining the uterus.

Question 12

What is a Follicle?

Answer 12

It is a structure in the ovary which contains an oocyte (immature egg/ovum).

Question 13

What is the Corpus Luteum?

Answer 13

It is a temporary endocrine structure found in the ovary which secretes progesterone and estrogen.

Question 14

What happens during day 1-5 of the Menstrual Cycle?

Answer 14

• very low levels of progesterone
• estrogen indicate body is not pregnant which triggers shedding of the endometrium (blood and tissue from uterus).

Question 15

What happens during day 6-14 of the Menstrual Cycle?

Answer 15

• FSH levels rise, follicle begins to develop
• As follicle develops, estrogen levels increase, causing increase in LH
• endometrium begins thicken, blood supply increases –> to prepare for fertilization

Question 16

What happens during day 14-15 of the Menstrual Cycle?

Answer 16

• follicle produces a mature egg which bursts from the ovary (ovulation)
• uterine lining continues to thicken after ovulation due to increase in progesterone and estrogen

Question 17

What happens during day 16-28 of the Menstrual Cycle?

Answer 17

• egg travels down the fallopian tube where it may be fertilized by sperm
• If fertilized: embryo secretes hCG (human chorionic gonadotropin) hormone to keep corpus luteum in ovary from breaking down and continues to secrete estrogen and progesterone to thicken and maintain uterine lining and prevent menstruation
• No fertilization: low progesterone levels cause lining to disintegrate and cycle begins at day 1

Question 18

Explain how Stress Eating occurs

Answer 18

• Cortisol and adrenaline hormones (epinephrine & norepinephrine) increase
• Hormones remove glycogen from liver and convert to glucose & convert fat to fatty acids to provide energy to body for “fight or flight” response
• When stress is gone, bodies replace stored glycogen from liver so we feel “hungry” for sweets