5.1.4 Hormonal Communication Flashcards
what is another word for the hormonal system
endocrine system
what is the hormonal system made up of
glands (called endocrine glands) and hormones
what are endocrine glands
group of cells that are specialised to secrete hormones
- e.g. the pancrease secretes hormones
what are hormones
“chemical messengers”
- most are proteins and peptides, e.g. insulin
- can be steroids, e.g. progesterone
when are hormones secreted by glands
when the endocrine gland is stimulated
when can an endocrine gland be secreted
- by a change in concentration of a specific substance, e.g. another hormone
- or can also be stimulated by electrical impulses
how do hormones travel around the body
- diffuse directly into the blood
- then are taken around by the circulatory system
when do hormones leave the blood
- diffuse out of the blood all over the body
- but each hormone will only bind to specific receptors for that hormone, found on the membranes of some cells
- = target cells
what is target tissue
- tissue that contains target cells
- contains the specific receptors for the hormone to bind to
what happens when hormones attach to a receptor on a target cell
they trigger a response in these cells (the effectors)
what is the chain of events that occurs in the hormonal system, and give example of low blood concentration
STIMULUS [low blood conc.]
RECEPTORS [on the pancreas cells detect this low conc.]
HORMONES [pancreas releases hormone glucagon into the blood]
EFFECTORS [target cells in the liver detect glucagon and convert glycogen into glucose]
RESPONSE [glucose is released into the blood, and so the glucose conc. increases]
why are hormones referred to as first messengers
because they carry the chemical message the first part of the way
- endocrine gland → the receptors on the target cell
what do hormones do when they bind to a receptor, as a first messenger
- it activates an enzyme in the cell membrane
- this enzyme catalyses the production of a molecule inside the cell called a signalling molecule
- this molecule signals to other parts of the cell to change how the cell works
why are signalling molecules called second messengers
they carry the chemical message the second part of the way
- receptor → other parts of the cell
what do second messengers activate
a cascade (chain of events) inside the cell
what is an example of a second messenger
cAMP - cyclic AMP
how does cAMP work as a second messenger
- the hormone adrenaline is the first messenger
- it binds to specific receptors in the cell membranes of many cells, e.g. liver cells
- when adrenaline binds, it activates an enzyme in the membrane called adenylyl cyclase
- activated adenylyl cyclase catalyses the production of second messenger cyclic AMP from ATP
- the cAMP then activates a cascade (e.g. the cascade of enzyme reactions that make more glucose available to the cell by catalysing the breakdown of glycogen into glucose
how could you show in a diagram how cAMP is made
- on the cell membrane, you have the receptor
- outside the cell, adrenaline binds to the receptor
- this activates adenylyl cyclase
- this transfers ATP to cAMP
- which leads to a cascade of reactions inside the cell
where are the adrenal glands found
just above your kidneys
what are the two parts of your adrenal glands
- outer part called cortex
- inner part called the medulla
- both have different functions, and produce different responses
what does the adrenal cortex secrete
- steroid hormones
- such as cortisol (a glucocorticoid) and aldosterone (mineralocorticoids) when your stressed
- have both a short-term and long term response to stress, but also vital to life
- also small amount of androgens, male and female sex hormones
what are the effects of hormones released by the cortex in short and long term responses to stress
- stimulating the breakdown of proteins and fats into glucose, increasing the amount of energy available so the brain and muscles can respond to the situation (cortisol)
- increasing blood volume and pressure by increasing the uptake of sodium ions and water by the kidneys (aldosterone)
- suppressing the immune system
what type of hormones does your medulla secrete
- catecholamine hormones (modified amino acids)
- e.g. adrenaline and noradrenaline when you’re stressed
- make more energy available short-term
what are the effects of hormones released by your medulla as short-term responses to stress
- increasing heart rate and breathing rate
- causing cells to break down glycogen into glucose
- constricting some blood vessels so that blood is diverted to the brain and muscles