Hormone structure and action

Question 1

Multiple forms of chemical communication

Answer 1

1. autocrine communication - chemical released by cells affects its own activity
2. Neurocrine (synaptic communicaton) - chemical released by neuron diffuses across synaptic cleft and effects postsynaptic membrane
3. paracrine communication - chemical released into extracellular environment and affects nearby target cells
4. endocrine (hormone) communication - chemical released into bloodstream and selectively affects distant organs
5. pheromone communication - chemical released into external environment and affects conspecifics
6. allomone communication - chemical released into external environment and affects heterospecifics

Question 2

what are hormones

Answer 2

1. bioregulators of the endocrine system
2. secreted by specialised cells directly into the blood
3. selectively act on target cells
4. chemical messengers produced in endocrine cells
5. 3 main types - protein hormones, amine hormones, steroid hormones

Question 3

protein hormones

Answer 3

1. chain of amino acids - peptide hormones have a short chain
2. e.g. oxytocin - social bonding
   insulin and glucagon - metabolism
   growth hormones
   lutenising hormone - reproduction

Question 4

amine hormones

Answer 4

1. modified single amino acid
2. smaller and simpler than protein hormones
3. e.g. adrenalines, thyroid hormones - metbaolism
   melatonin

Question 5

action of protein and amine hormones

Answer 5

1. bind to receptor specific to hormone type on outside of cells
2. receptor shape alters
3. secondary messengers
4. altered cell function and biological effects
5. sensitivity can be altered by increasing or decreasing numbers of receptors on cell
6. stored in vesicles and secreted on demand

Question 6

steroid hormones

Answer 6

1. derived from cholesterol
2. made from four interconnected carbon rings
3. soluble in lipids
4. e.g. oestrogen, androgens
   glucocorticoids - stress hormones

Question 7

action of steroid hormones

Answer 7

1. steroid hormones diffuse passively into cells
2. bind to specific steroid receptor inside the cell
3. act slowly
4. steroid receptor complex binds to DNA, altering production of proteins
5. sensitivity can be altered by presence or absence of cofactors necessary for cells to respond
6. can’t be stored, must be synthesised on demand

Question 8

where are hormones produced in the body

Answer 8

1. endocrine glands/ organs
2. follicular cells secrete hormones into the lumen
3. hormone transported into thin-walled capillary and flows into bloodstream
4. ductless - no ducts leading to blood stream

Question 9

what controls hormone production

Answer 9

1. hormone production needs to be constantly managed
2. feedback loops play a key role
3. usually involves negative feedback - high levels of hormone inhibit production of hormone - maintains homeostasis
4. sometimes involves positive feedback
5. key pathways - autocrine feedback, target cell feedback, brain regulation, brain and pituitary regulation

Question 10

pituitary gland

Answer 10

1. consists of two parts - anterior and posterior
2. anterior - synthesis and secretion of hormones
3. posterior - stores and secretes only

Question 11

how do hormones act within the body

Answer 11

1. short term effects - e.g. oxytocin, hypothalamus stimulates oxytocin neuron, posterior pituitary releases oxytocin, mammary glands contact and release milk, receptors in nipple sense sucking, positive feedback loop, nerve impulses stimulate hypothalamus again, when baby is satisfied it stops sucking, so stimulation and oxytocin production stops
2. long term effects - e.g. growth hormone, regulation of bone growth, hypothalamus releases somatocrinin, anterioir pituitary releases growth hormone, some long term effects can be reversed