Hormones

IB Psychology: Hormones

Hormones are another class of chemicals that affect behaviour. Unlike neurotransmitters, hormones are not released by the terminal buttons of a neuron; instead, they are secreted by glands in the endocrine system. So epinephrine (adrenaline) is released by the adrenal gland into the bloodstream as a hormone whereas norepinephrine (noradrenaline) is released by neurons in the brain as a neurotransmitter. Hormones are...


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Comments 9

Ian Latham 6 November 2017 - 18:38

You comment that "epinephrine (adrenaline) is released by the adrenal gland into the bloodstream as a hormone whereas norepinephrine (noradrenaline) is released by neurons in the brain as a neurotransmitter" so can I double-check that in McG&C, the idea is that it was the hormone adrenaline that, released from the adrenals, 'reached' and interacted with the amygdala. We're about to cover this in class. Thanks!

John Crane 6 November 2017 - 19:01

Dear Ian - yes, that is my understanding of the study as well.

Ian Latham 6 November 2017 - 19:58

Good. Thanks. One student has written in the mocks (marking them right now) that cortisol diminishes levels of Ach in hippocampus. Do you remember any evidence of an explicit interaction?

John Crane 7 November 2017 - 05:21

Ian, there seems to be a threshold for cortisol in the hippocampus. At moderate levels, it actually assists in the transfer of memory; higher levels impede memory transfer. It is thought that it affects acetylcholine in an indirect manner. High levels of cortisol also appear to lead to hippocampal cell death. An atrophied hippocampus means fewer acetylcholine receptor sites.

Ian Latham 7 November 2017 - 07:56

Thanks: clear. Dendritic retraction & cell death & atrophied hippocampus means less Ach. Can I ask: is this the effect of the standard and healthy HPA cortisol response? Or is this an issue of chronic stress alone? And if so, how long does stress have to last to be considered chronic stress? The Biology teacher explains that cells can change very quickly and within the 4 day period: he suggests that 'damage' can be done very quickly. But I've always understood these 'extreme' effects as happening over a period of weeks or months, or years. Can we talk about chronic stress when referring to a period of 3 or 4 days, such as in the Newcomer experiment?

John Crane 7 November 2017 - 13:12

Ian - I think that there are two different phenomenon here. It can be a short term stress but at a high level - and this is what leads to apoptosis (cell death). It is the same effect as chronic stress. I am not sure where the line is for chronic stress - a good question. Have you read Sapolsky's new book "Behave?" Totally engrossing. If you are hungry for a deeper understanding of the biological underpinnings of behaviour, I think that it is really thought provoking and has explained a lot to me that I have never understood or had the energy to find out. For example, he explains the two types of acetylcholine receptor sites. Very interesting.

Melissa Rossiter 9 November 2017 - 22:36

Can we use Newcomer or is verbal declarative memory no longer a behaviour?

John Crane 10 November 2017 - 05:15

Melissa - a recent clarification is that memory is still considered a behaviour, so Newcomer is still relevant.

Melissa Rossiter 10 November 2017 - 05:26

Thanks so much John!


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