Introduction to Hormones – 7.1

Hi. My name's doctor Matt Ivory.

I'm one of the lecturers in the School of Pharmacy and Pharmacy of university.

And in this series of talks,

we're gonna look at the hormone system and the ways in which

that's used to coordinate responses in the body.

We'll look at some specific examples like adrenaline and thyroxine,

and we'll look at the process and the hormones involved in

the female menstrual cycle.

So in this first talk, we will have a look at hormones,

what they are, and how they are used within the body.

So we've discussed in the previous talk about the nervous

system about the importance

of organisms to be able to respond to stimuli in their environment.

Whether it's moving towards food,

whether it's escaping predation,

or any one of the other potential responses that an

organism might need to undertake.

So the way that the cells in a multicellular organism

coordinate with one another is through the nervous system.

So neurons send impulses

to different parts of the body and also through the use of hormones.

So the two systems are used in slightly different ways to

allow communication between cells in different and distant

parts of the body.

So, hormones are substances that are released by the glands

of the endocrine system. So these are endocrine glands.

And hormonal control tends to be used slightly differently

than nervous controls.

So nervous signals tend to be quite quick,

so nervous impulses move rapidly down neurons,

but they only tend to cause a shorter effect,

and they only tend to be over a small area.

So it might be that you move your hands to catch a ball and

then the signal is finished and your hands stop moving.

Omono control tends to produce more extended responses to

stimuli, so the signal lasts for much longer.

And it tends to be over a larger area,

so hormones are released across the entire body and so it can

affect multiple tissues, unlike in your own,

which will just stimulate one affected tissue.

And so because they have this long lasting and broad ranging effect,

hormone control tends to be used for maintenance of bodily

edition, so keeping things within acceptable levels,

and that's called homeostasis.

And we'll talk more about that in a future set of talks.

So as we've said, the hormones are released from endocrine

glands and they're released into the liquid part of the

blood. So that's the plasma of blood.

And that allows them to be transported in the circulatory

system all over the body.

So they won't be received. They won't have an effect.

On all of the cells of the body.

They'll have particular target organs,

and the cells within those organs will have receptors

specific for those hormones.

So you release the hormone all over the body,

but it's only certain cells that will be affected by it.

So because the substances have to be released,

and pumped all over the body.

It is a slower response. So unlike a nerve impulse turning

on a gland or causing a muscle to contract,

It's much slower for that signal to be received by the target organ.

But then, those hormones can circulate for quite some time,

and allow that extended duration of the signal to occur.

And you also have the advantage as well that it's going to

permeate all of the different tissues of the body.

And so you can signal multiple organs to have an effect with a single hormone.

So there are numerous different endocrine glands,

and each of them will release one or more different hormones,

and the hormones themselves will have one or more purposes.

So lots of different things can be achieved using hormonal control.

So if you look at three of the endocrine glands in particular,

The pituitary gland is found at the base of the brain,

and that's responsible for releasing a number of different hormones.

Quite a few of these hormones that get released from the

pituitary gland trigger the release of other hormones from

other glands. So sometimes it's known as the master gland.

So an example of a hormone released from the pituitary

gland is ADHD,

and that's used in osmo regulation.

Talk more about that in the lecture where we look at kidneys.

The thyroid gland is found in the neck and this releases thyroxine.

And thoraxin affects our rate of metabolism

and cardiac output as well,

and we'll talk more about that in the next talk.

And the adrenal glands are found above the kidneys,

so there's one above each kidney, and they produce

adrenaline, which is involved in the fight or flight

response. And again,

we'll look at that in a bit more detail in the next talk.

So, the pancreas

is found in your abdomen. And it produces insulin and glucagon.

And these are really important in regulating the level of

glucose in the blood.

And there's more about this in the homeostasis lecture.

So, the ovaries are one of the female sex organs,

part of the female reproductive system.

And they are found in the pelvic region,

and they release hormones like estrogen

that are involved in puberty and the menstrual cycle. And again,

This is one that we will cover in more detail in a later talk.

And testes are the male equivalent, so male sex organs,

and they release hormones.

So they're found in the external scrotum,

and they produce testosterone,

which controls both puberty and bone development.

So both estrogen and testosterone have endocrine

glands as target organs,

so as well as being released from a gland themselves.

They affect glands to stimulate them to release hormones.

So they both cause the release of growth hormone,

and that's the reason that in puberty when you have more of

these hormones, either estrogen or testosterone released,

then you have a much higher release of growth hormone,

so that's why more growth occurs during puberty than the

times before or after it.