Endocrine system

What is the endocrine system

• hormones

  • released in 1 part of the body

  • regulates cell activity

• slower responses

• effects last longer

• broader influence

• stimulate + inhibit other reactions

What are exocrine glands and 3 examples

• ducted

  • salivary glands

  • sweat glands

  • mucus glands

What are endocrine glands and 3 examples

• ductless

  • secrete hormones into interstitial fluid or blood

  • pituitary gland

  • thyroid gland

  • adrenal gland

What is the function of paracrine hormones

act on neighbouring cells

What is the function of autocrine hormones

act on same cells

What does FSH do

• stimulates oocyte development

  • from anterior pituitary to ovaries

What does gastrin do

• stimulate parietal cells to produce HCL

  • produced by gastric G-cell

What does testosterone do

• increases spermatogenesis

  • from leydig cells in testis

What are lipid-soluble hormones and 3 examples

• use transport proteins

  • steroid hormones (testosterone)

  • thyroid hormones (thyroxine)

  • nitric oxide (NO)

What are water-soluble hormones

• circulate in free form

  • amines (epinephrine)

  • peptides (insulin)

  • eicosanoid (prostaglandins)

How do lipid-soluble hormones bind to receptors inside target cells`

• transported around body by transport proteins

• fat-soluble hormone cross cell membrane

• binds to intracellular receptor

• alters gene expression of a particular protein

• protein produces effect

What happens when water-soluble hormones bind to receptors on the plasma membrane

• activates seconds messenger system

• amplification of original small signal

What 3 ways is hormone secretion controlled

• regulated by negative feedback

  • signals from nervous system

  • chemical changes in blood

  • other hormones

What is the permissive effect

• a second hormone strengthens the effect of the first

  • thyroxine strengthens adrenalines effect

  • increases number of adrenaline receptors

What is the synergistic effect

• 2 hormones acting together for greater effect

• oestrogen and LH both needed for oocytes production

What is the antagonistic effects

• 2 hormones with an opposite effect

  • insulin promotes glycogen formation

  • glucagon stimulates glycogen breakdown

How long is the ovarian & menstrual cycle

24-35 days

What are the 2 phases of the ovarian cycle and what do they result in

• follicular phases

• luteal phase

• result in maturation & production of secondary oocyte at ovulation

What 3 hormones regulate the ovarian cycle

• regulated by changing levels in:

  • oestrogen

  • inhibin

  • progesterone

What are the 3 phases of the menstrual cycle

• menstrual

• proliferative

• secretory

What is the function of the menstrual cycle

• prepares the uterus for implantation of a fertilised ovum

• no fertilisation = menstruation

  • caused by hormone change

What hormones are involved in the ovarian cycle

• controlled by gonadotropic releasing hormone (GnRH)

  • stimulates the release of FSH and LH

  • from gonadotrophs in the anterior pituitary gland

How does GnRH control both FSH & LH

• high GnRH frequency = LH secreted

• Low GnRH frequency = FSH increase

How does oestrogen affect GnRH and LH

• GnRH pulse frequency increases

  • LH released

How does progesterone affect GnRH and FSH

• GnRH pulse frequency decreases

  • FSH released

How does Inhibin affect FSH, oestrogen and progesterone

• inhibits FSH release

• stops oestrogen getting too high & overtaking progesterone