How do hormone responses occur so rapidly? When people are frightened/surprised, they can almost immediately feel a rush of adrenaline and heart rates rise, faces flush, etc. How do hormones reach appropriate organs so quickly? Why isn’t there more of a delay for the hormones to travel?
In: Biology
As said before, blood travels at roughly 3mph. That sounds really slow, until you realize it’s about 4.4 feet (140cm)/sec. Nerve transmissions are a couple of orders magnitude faster (60-100m/sec, depending on nerve type).
So, also as said before, brain receives and processes the stimulus very quickly (signals can go 10cm, or one side of the brain to another, in 0.1sec or less.
Parasympathetic blocks at this point (norepinephrine released in the brain), so sympathetic runs without restraint (fight or flight kicks in). One or two tenths of a second later, the impulses hit the adrenals, which release adrenaline into the bloodstream. It then travels less than a foot, in less than a couple tenths of a second, to receptors in the heart and lungs (heart rate, heart force, artery compression, breath rate, and breath volume all increase). This is why your startle response usually goes “oh sh^t .. OH SH^T”.
It takes a couple seconds longer to get to the skin (sweat, and either hot or cold skin depending on core body needs – more blood or dump heat).
Hey! So hormones dont actually work very quickly at all. In fact they move quite slow! Hormones get created in response to certain internal or external stimuli and then shipped through the body via the blood stream. As they move through your body they interact with different areas and cause wide spread responses. Think of them as slow, whole body action grenades. The high speed action molecule you are thinking of is a neurotransmitter.
Neurotransmitters are small molecules that are directly targeted at specifics areas to create instant responses. A good example is seratonin dumps in your brain when something goes happens to you! Cells in your brain will dump large amounts of seratonin or dopamine into the areas between cells ( the synaptic cleft ) and these molecules will bounce around like pinballs dinging receptors that then cause other cells to do the same. These kind of interactions happen really quickly in a target area and tend to have short term effects on your body.
So if your body needs a fast fight or flight type response like being excited by a kiss, it will use neuro transmitters to communicate across cells. If it wants a slow and steady change to the body like increasing muscle it will use an hormone like testosterone that it can ship throughout the body via the blood stream.
Tldr: Hormones are slow, and illicit whole body reactions, neurotransmitters are quick targeted reactions between cells.
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