Week 4. Endocrine Control

Question 1

What is the main COMPLEX that regulates hormone secretion? Where is it found

Answer 1

hypothalamic-pituitary axis found in the lower area of the brain

Question 2

What does the Hypothalamic-pituitary axis consist of?

Answer 2

• anterior and posterior pituitary gland
• hypothalamus

Question 3

What hormones are secreted in the posterior pituitary gland (PPG). What enables this secretion and where does it occur?

Answer 3

• oxytocin
• ADH: antidiuretic hormone
• these hormones are made in the neuron cells located in the hypothalamus
• hormones are transported from neuron cell bodies in the hypothalamus to axon terminals in PPG - through the infundibulum channel that connects the hypothalamus to PPG
• hormones are stored in axon terminals in PPG
• they are released into capillaries in PPG when hypothalamic neurons fire action potentials
• hormones are transported around the body via the circulatory system to target cells

Question 4

What is the role of the hormones secreted in the PPG?

Answer 4

Oxytocin:
- stimulates contractions in the uterus
- promotes milk ejection during lactation
- influences our social behaviour

ADH:
- maintains water levels in the body via osmoreceptors in the pituitary gland that monitor osmotic pressure of extracellular fluid
- reduces and maintains water levels in the kidneys
- determines how much water we secrete daily

• high pressure = not enough water –> results in water retention
• high pressure = activated neurons in hypothalamus = acts on axon terminals in the PPG to release ADH
• causes constriction of blood vessels

Question 5

What hormones are secreted in the anterior pituitary gland (APG). What enables their secretion

Answer 5

• there are 6 hormones secreted in the APG
  the main three focused on in the course are:
  
  • thyroid-stimulating hormone (TSH)
  • adrenocorticotrophic hormone (ACTH)
  • growth hormone (GH)

the others are associated with mammary glands and reproductive glands

Question 6

how are messages sent to the APG from the hypothalamus

Answer 6

• neuron axons from the hypothalamus are terminated within the infundibulum
• a network of blood vessels in the infundibulum connect to the axon terminals, allowing hormones to travel to the APG
• hormones bind to target endocrine cells in the APG to stimulate secretion or inhibition of certain hormones
• secreted hormones enter capillaries and travel to target cells in the body via the systemic circulatory system