Hormones

Question 1

What are hormones?

Answer 1

• type of chemical communication
• bioregulators of the endocrine system
• secreted by specialised cells directly into the bloodstream where it’s transported
• selectively act on target cells

Question 2

What are the different forms of chemical communication?

more distant effects the lower down on the list

Answer 2

• autocrine communication: chemical released by cell, affects its own activity
• neurocrine communication: chemical released by neuron diffuses across synpatic cleft, affects postsynaptic membrane
• paracrine communication: chemical released into extracellular environment, affects nearby target cells
• endocrine communication: chemical released into bloodstream, selectively affects distant organs
• pheromone communication: chemical released into external environment, affects conspecifics
• allomone communication: chemical released into external environments, affects heterospecifics

Question 3

How is endocrine signals transmitted?

Answer 3

• stimulus acts on the endocrine cell
• induces endocrine cell to release hormones into bloodstream
• travels around body and can contact target cells anywhere in the body so long as those particular targets have correct receptor type for hormone to respond to

Question 4

What are the 3 main types of hormones?

Answer 4

• protein hormones: chain of amino acids
• amine hormones: modified single amino acids, smaller and simpler than protein hormones
• steroid hormones: derived from cholesterol, made from 4 interconnected carbon rings, soluble in lipids

Question 5

What are the actions of protein and amine hormones?

Answer 5

• when protein hormones arrive at the receptor they combine to the receptor, when combining it changes the shape of that receptor
• induces the release of substances within the cell which alter the function of a cell and have multiple biological effects
• bind to specific receptors on outside of cells, act rapidly and have prolonged effects (sensitivity can be altered by increasing/decreasing numbers of receptors on cell)

Question 6

What are the actions of steroid hormones?

Answer 6

• act on specific receptors inside cells (acts slowly)
• diffuse passively into all types of cells
• long lasting effects via transcription of DNA
• sensitivity can be altered by presence/absence of co-factors necessary for cells to respond
• cannot be stored

Question 7

What are endocrine glands/organs?

Answer 7

• where hormones are produced
• contains: follicle, lumen, follicular cells, capillary
• follicular cells secrete hormones into the lumen which then passes it onto the bloodstream across the capillary
• hormone transported into thin-walled capillary and flows into bloodstream

Question 8

What controls hormone production?

Answer 8

• hormone production needs to be constantly managed
• feedback loops play a key role and usually involves negative feedback (high level of hormones inhibit production of hormone), sometimes involves positive feedback

Question 9

What are the key pathways of production?

Answer 9

• autocrine feedback: excessive amounts of hormone are fed back into endocrine cells to inhibit further release
• target cell feedback: endocrine cells producing particular hormone that effects biological response that inhibits further production of hormones
• brain regulation: neural/hormonal stimulation of endocrine cells to release hormone that effects target cells and biological response that feeds back to hypothalamus to inhibit stimulation
• brain and pituitary regulation: cascade of different hormonal effects, hypothalamus makes releasing hormone that acts on pituitary gland to stimulate release of tropic hormone that acts on endocrine cells to produce specific hormone for target cells creating biological response

Question 10

What is the pituitary gland?

Answer 10

• sits below the hypothalamus, connected by the infundibulum structure
• involved in production an regulation of many other important hormones
• 2 parts: anterior pituitary and posterior pituitary
• anterior pituitary synthesises and secretes hormones
• posterior pituitary stores and secretes only

Question 11

What is a short-term effect of hormones?

Answer 11

• oxytocin and the milk letdown reflex
• involves hypothalamus and the posterior pituitary
• receptors in nipple sense sucking and stimulated to send nerve impulses to stimulate hypothalamus which leads to release of oxytocin from posterior pituitary -oxytocin stimulates mammary glands that contract and release milk
• once satiated and stops sucking the stimulation and thus the oxytocin stops

Question 12

What is a long-term effect of hormones?

Answer 12

• growth hormone and regulation of bone growth
• involves hypothalamus and anterior pituitary
• somatocrinin (releasing hormone) is produced by hypothalamus, stimulates the anterior pituitary to release the growth hormone
• sleep stimulates further release of somatocrinin

Question 13

What are the contexts that hormones influence behaviour in?

Answer 13

• biological rhythms
• eating and drinking
• reproductive behaviour
• social behaviour

Question 14

What is the endocrine system?

Answer 14

• chemical substance
• conveyed in blood
• diffuse effect across body
• analogue signal
• slow response
• response persists over time
• no voluntary control

Question 15

What is the nervous system?

Answer 15

• action potential
• transmitted along nerve fibre
• targeted effect in specific cell/organ
• digital signal
• fast response
• responses generally short-lived
• some voluntary control

Question 16

What is the neuroendocrine system?

Answer 16

• fast initial response
• prolonged action if required
• enables regulation and control of homeostasis via CNS, ANS, SNS and PSNS
• ensures that the appropriate response is given to a stimulus