Wk 9: Intro to endocrine

Question 1

What is a paracrine?

Answer 1

Secreted into extracellular fluid + effect nearby target cells

Question 2

What is an autocrine?

Answer 2

Cell signal released into extracellular fluid binds to same cell

Question 3

Give an example of a single hormone exerting effects on diff. tissues

Answer 3

Estradiol (ovaries)

• Ovarian follicle: maturation
• Uterus: stim growth + maintain cyclic changes in uterine mucosa
• Mammary gland: ductal growth
• Hypothalamic-pituitary system: regulate secretion gonadotropins + prolactins
• Bone: skeletal integrity
• Metabolic process: adipose tissue distribution

Question 4

Outline the mechanism of action of protein + polypeptide hormone receptors

Answer 4

• Bind to surface receptors
• Transduction
• Enzyme activation
• Open channels
• Second messenger systems
• Synthesis

Question 5

Outline the mechanism of action of steroid hormone receptors

Answer 5

• Most hydrophobic steroids bound to plasma protein carriers, only unbound diffuse into target cell
• Receptors in cytoplasm or nucleus
• Receptor hormone complex binds to DNA + activates or represses one/more genes
• Activated genes create new mRNA that moves back to cytoplasm
• Translation produces new proteins for cell processes
• Some steroid hormones bind to membrane receptor that use 2nd messenger system to create rapid cellular responses

Question 6

What regulates hormones?

Answer 6

Hypothalamus - coordinating center of brain for endocrine, behavioural + ANS

Question 7

Give an example of a positive feedback

Answer 7

Breastfeeding:

• Child cries when hungry, hypothalamus stimulated
• Hypo sends impulses to posterior pituitary
• Posterior pit releases oxytocin
• Oxy stimulates milk ejection from breasts
• When child suckles nipples, stimulates nerves in breasts sending impulses to hypo
• Suckling = muscles of breast contract leading to milk ejaculation