Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Hormones, homeostasis and reproduction

Topic 6
...
6

Biology SL

➢ Its target cells are in the hypothalamus of the brainstem
➢ People who are obese are known to have a greater level of leptin circulating in their
bloodstream
○

Their hypothalamus has become “desensitized”

Melatonin
➢ It’s produced by a very small gland in the brain called pineal gland
○

It helps regulate our 24-hour cycle of activity (circadian rhythm)

➢ We have very little melatonin during the day
...
From there it goes to veins and then to
hepatic portal vein which leads to the liver
○

The concentration of glucose in the hepatic portal vein varies

○

Blood levels fluctuate to a large extent too

➢ Hepatocytes are liver cells that process blood
○

Triggered into action by insulin and glucagon
■

The 2 hormones are antagonistic

Glucose rises
➢ In the pancreas there are cells known as β cells that produce the hormone insulin
➢ All cells are exposed to insulin, as it opens protein channels in their plasma
membrane so glucose can diffuse into them
2

Hormones, homeostasis and reproduction
○

Topic 6
...
6

○

Poor wound healing and possibly gangrene

○

Kidney failure

○

Nerve damage

Biology SL

Human reproduction
➢ Fertilization occurs when a haploid male gamete (sperm) meets a haploid female
gamete (egg)
○

Promotes variation

➢ Hormones play a key role in both the development of sexual dimorphism and the
regulation of sexual physiology

Male structure

Function

Testis

Sperm are produced here in small tubes

Epididymis

Where sperm become mature

Scrotum

Sacs that hold the testis

Vas deferens

A muscular tube that carries mature sperm

called seminiferous tubules

from the epididymis to the urethra during
an ejaculation

Seminal vesicles

Glands that produce seminal fluid

Prostate gland

Produces much of the seminal fluid

Penis

Organ that becomes erect due to blood

including carbohydrates for the sperm

engorgement to facilitate ejaculation
Urethra

The tube via which the semen leaves the
penis

4

Hormones, homeostasis and reproduction

Topic 6
...
6

■

Enlargement of larynx/deepening of voice

■

Increased muscle mass

■

Enlargement of penis

■

Growth of facial, underarm, chest and pubic hair

Biology SL

Menstrual cycle

➢ Menstrual cycle is a hormonal cycle that lasts on average 28 days, which times the
release of an ovum for possible fertilization and later implantation into the
endometrium
➢ The implantation will occur when the endometrium is rich with blood vessels
○

If there isn’t any, breakdown of the vessels lead to menstrual bleeding

➢ The hypothalamus is the regulatory center of the menstrual cycle
○

Produces the gonadotropin releasing hormone (GnRH) which targets the
pituitary gland

➢ The anterior pituitary gland produces and secretes the follicle stimulating hormone

(FSH) and luteinizing hormone (LH) both of which target the ovaries
➢ The ovaries start secreting oestrogen which targets the endometrium
○

It makes it highly vascular

➢ Oestrogen also acts on the pituitary gland making it to produce more FSH and LH

Positive feedback
➢ Another effect of FSH and LH is the production of structures within the ovaries
○

known as Graafian follicles
○

There are follicle cells and oocytes in the ovaries which are true
reproductive cells at stage of development

○

FSH and LH stimulate them and they take on the cellular arrangement
known as Graafian follicle

➢ By positive feedback, the concentrations of FSH and LH become very high which
cause ovulation
○

Oocyte and inner ring of the follicle leave

➢ The outer ring of the follicle cells remain within the ovary producing and secreting
progesterone
○

The cells start dividing forming the corpus luteum which is hormonally
active for 10-12 days after ovulation
■

It produces progesterone maintaining the thickened, highly vascular
endometrium

6

Hormones, homeostasis and reproduction

Topic 6

---