5.1.4 (a-b); 5.1.5 (j)

Question 1

Define endocrine gland (name the main ones)

; exocrine gland

Answer 1

Endocrine Gland: A group of specialised cells (gland) which is ductless that produces hormones and secretes them directly into the bloodstream

Exocrine Gland: Secrete molecules through ducts to reach parts of the body

Question 2

What are hormones?

Answer 2

• Cell-signalling molecule transported in the blood
• Released from endocrine glands directly into blood stream
• Target cells: Cells on target tissue with receptors specific to a hormone on the membrane

Question 3

What are the types of hormone and outline their mechanisms?

Answer 3

• Steroid Hormones – lipid-soluble
  
  • Passes through lipid component of cell membrane and binds to steroid-hormone receptors
  • Forms a hormone-receptor complex – acts as a transcription factor to inhibit or facilitate the transcription of a gene
• Non-steroid Hormones – hydrophilic (can’t pass through cell membrane)
  
  • Binds to receptors on cell surface
  • Triggers cascade reaction

Question 4

What is the fight or flight response?

How do the hormonal and neuronal systems coordinate responses?

Answer 4

• A response to a dangerous environmental stimulus for survival
• Threat detected by autonomic nervous system
  
  • Hypothalamus tells sympathetic nervous system and adrenal-cortical system
  • SNS – uses to neuronal pathways to initiate reactions in body
  • Adrenal-Cortical System – secretes hormones into the blood stream
  • Combination of the hormonal and neuronal responses is fight or flight
• SNS sends impulses to glands and smooth muscle and stimulates adrenal medulla to release adrenaline and noradrenaline
  
  • Hypothalamus stimulates pituitary gland to release ACTH, which travels to the adrenal cortex to stimulate the release of hormones to deal with a threat

Question 5

What are 1^st and 2^nd messengers?

Answer 5

• First messenger is the hormone – carries signal from endocrine gland to cells of target tissue
• Second messenger is the molecule in the cells of the target tissue transmitting the signal from the membrane-bound receptor into the cytoplasm

Question 6

Describe the action of adrenaline in cell signalling

Answer 6

Adrenaline is a hormone (hydrophilic – non-steroidal), it cannot pass through cell membranes, it binds to receptors on hepatocytes to trigger glycogenolysis

1. Adrenaline is the 1^st messenger that binds to an adrenergic receptor (adrenaline specific receptor) forming an adrenaline-receptor complex
2. This activates a G-protein which in turn activates the enzyme adenylyl cyclase.
3. Adenylyl cyclase converts ATP to cAMP (the 2^nd messenger)
4. cAMP activates enzymes called protein kinases that phosphorylate and activate other enzymes

Question 7

What is the structure of an adrenal gland?

Answer 7

Located on top of the kidney

Made up of:

1. Adrenal Cortex – outer region
   
   • (produces essential hormones, e.g. cortisol, aldosterone)
2. Adrenal Medulla – inner region
   
   • (produces non-essential hormones, e.g. adrenaline)

Question 8

What controls the release of hormones in the adrenal cortex?

What hormones are released by the adrenal cortex?

Answer 8

Release of hormones controlled by hormones released from the pituitary gland

Main hormones produced:

• Glucocorticoids – release controlled by hypothalamus
  
  • E.g. cortisol, regulates metabolism of fats, proteins and carbohydrates
  • Also regulates blood pressure & cardiovascular function related to stress
  • E.g. corticosterone – works with cortisol to regulation immune response and suppress inflammatory responses
• Mineralocorticoids – release controlled by signals from the kidney
  
  • E.g. aldosterone – regulates blood pressure by maintaining salt and water balance in blood
• Androgens
  
  • Small amounts of male and female sex hormones
  • Important in post-menopausal women as their hormone levels decrease as they get older

Question 9

What controls the release of hormones in the adrenal medulla?

What hormones are released by the adrenal medulla?

Answer 9

Released when the sympathetic nervous system is stimulated (body is stressed)

• Adrenaline
  
  • Increases heart rate, sends blood quickly to muscles and brains
  • Causes rapid increase in glucose levels
• Noradrenaline
  
  • Works w/ adrenaline in response to stress – increases heart rate; widens pupils; widens air passages; narrows blood vessels in non-essential organs (increasing blood pressure)