hormonii 1 Flashcards
what are hormones important for
to understand basic biological functions of the brain and the body
we can better understand psychological states and behaviour
what is the endocrine system
a chemical communication system of the body
includes glands and hormones
what are glands
structures which secrete or produce specific chemical substances
glands are the target for signals that tend to come from the brain
what are hormones
chemical messengers released in response to these signals
hormones are the ways in which certain parts of the body communicate
hormones are released through the blood stream
glands release hormones in the capillary and hormones travel towards a target
what are the functions of the endocrine system
- maintenance of the internal environment in the body - homeostasis
- regulation of growth and development
- control, maintenance and instigation of sexual reproduction
what is the neuroendocrine system
hypothalamus and pituitary gland - located in the brain
what is hormonal signalling
a complex way to refer to the way hormones are produced and target the destination cells or glands
- There is a change in the body or environment which is picked up by hypothalamus - master mind of the endocrine system
- Hypothalamus works in close collaboration with the pituitary gland by releasing a set of hormones that induce or trigger a number of responses in the pituitary gland
- Pituitary gland triggers additional hormones and those hormones either target a tissue or another gland and 4. those would exert a particular action
what is the hypothalamus
deep inside the brain
made up of a number of subparts which take the name of nuclei
nuclei are critical for different functions in the hypothalamus
nuclei allow the hypothalamus to be specialised in a variety of functions
what does the hypothalamus aim
to maintain homeostasis - internal balance
our body needs to have certain balance in order to operate optimally
hypothalamus operates to promote the releasing or stop the releasing of hormones so that certain basic functions like temperature are maintained at optimal level
what is the pituitary gland
small structure
controls a number of other glands and organs
connected to the hypothalamus to form the neuroendocrine system
divided into anterior and posterior lobe
hard to reach in case of injury
what are the properties of hormones
hormones are produced and released in secreting cells
hormones have an effect at a site different from where they are made - target cells
hormones travel through the bloodstream
they fit precisely onto a target cell’s receptors so they are specific for a particular cell
= specific hormones for specific receptors
what is the classification of hormones
- chemical criteria
- steroid hormones
- peptide hormones - functional criteria
GENERAL
- activating effects
- organisational effects
SPECIFIC
- homeostatic hormones
- glucocorticoids hormones
- gonadal (sex) hormones
what are steroid hormones (chemical classification)
steroid hormones are hormones that are fat soluble - they can cross the cell membrane
this means hormones are capable on acting on the target cells DNA
what is the journey of the steroid hormones
they cross the cell membrane
in cytoplasm they find steroid receptor
hormone will bind onto steroid receptor
then enters nucleus of the cell
here it will bind to mRNA and act on the cell DNA
What are peptide hormones
hormones which are not fat soluble so can’t cross the cell membrane
peptide hormones bind on a receptor on brown structures which sit on the cell membrane and it will not be able to enter cell
so they do not act directly on cell’s DNA
what are the 2 GENERAL functions of hormones
Activating effect or
Organisational effects
What are activating effects
activating effect is a reversible change in terms of the properties of the cell
it happens when the hormone is sitting on the receptor of a cell
the effect would last for a short amount of time
what are organisational effects
permanent or semi-permanent change in the structure of the nervous system
happens during a particular point in life - sensitive period in early development
hormones aka steroid hormones enter the cell’s nucleus and affect gene expression
steroid hormone can reach all the way into the nucleus and bind onto the mRNA and act on DNA
what are the 3 types of SPECIFIC functions
- Homeostatic hormones
- Glucocorticoids hormones
- Gonadal (sex) hormones
what are homeostatic hormones
hormones that aim to maintain a metabolic balance - homeostasis
and they regulate a number of physiological systems
homeostatic hormones exert an activating effect so action is only temporary
what is keeping the balance important
certain critical parameters need to be at a constant level so that the rest of the organs can function normally
e.g.
if we are asleep we are not able to control temperature so those functions need to look after themselves
there are a no. of physiological conditions that need to be maintained in a balanced way so we can operate normally
any imbalance will have devastating effect on the organs
what is an example of homeostatic hormones
insulin
makes sure glucose is maintained at optimal level
produced by pancreas
- the action of insulin promotes glucose intake by being released in the bloodstream and unblocking cells so they can take up glucose
why is the action of insulin important
cells use glucose for their energy requirements and cells can obtain glucose from blood
who uses insulin
muscles cells use glucose but they can also use other substances for fuel like protein and fat
HOWEVER
neurones can only use glucose
if glucose is low, priority is given to neurones
neurones cannot store glucose so they depend on the availability of glucose in the bloodstream
HENCE
we need to have a system in place that is able to maintain glucose at an optimal level
how does insulin work
when insulin is in proximity with cell, insulin receptors bind with insulin molecule
glucose channel opens up and glucose enters cells and is used as energy supply
SO
insulin enters bloodstream from pancreas
insulin binds to receptor
insulin on receptor opens glucose channel
glucose leaves bloodstream and enters cell through glucose channel
what is the step by step process of insulin
Physiological changes happen.
These changes are picked up by the hypothalamus.
Change is translated into a message that is sent to medulla in brainstem.
Message will travel towards pancreas via the vagus nerve.
That induces pancreas to secrete insulin.
how are levels of glucose in the blood detected
there are chemoreceptors that can detect how much glucose is in the blood
what happens if there is too much glucose in the blood
Triggers the released of insulin
Cells take up the glucose
what happens if there is too little glucose
secretion of insulin is stopped and cells are unable to pick up glucose
There has to be residual glucose available in case neurones need it
what happens if there is fall in blood sugar levels
Hypoglycaemia
can cause fainting or coma
Neurones do not function properly as they depend on glucose
Symptoms resolve when the sugar level returns to normal
what happens when there is rise in blood sugar levels
Hyperglycaemia
deficiency in production of insulin or defective insulin receptors
type 1 and 2 diabetes
you have sugar but cells are not capable of using it
what is type 1 diabetes
little or no insulin produced
we have glucose in the stomach and enters the blood stream
pancreas should make insulin so glucose can be used by cells
instead there is little insulin made and sugar remains available in the blood stream and is not used up
what is type 2 diabetes
insulin receptors become defective.
body produces insulin but insulin molecules are not able to bind to receptors so less glucose is used by cells
what are glucocorticoids hormones
control stress and regulate metabolism
exert an activating effect so action is only temporary
what is stress
the body’s reaction to feeling threatened or under pressure.
stress is stimulus that challenges homeostasis of the body and triggers arousal in humans
what is the physiological response of stress
response to stress is the same irrespective of the stressor - exciting or frightening
how do we activate a stress response
when we face a stressful situation we mobilise our body resources so we can respond to stress and achieve a point where we rebalance the situation and restore homeostasis
what is fast acting system based on
Nervous system: sympathetic pathway
Hormonal system: adrenaline and noradrenaline
what is the slow acting system based on
Hormonal response: HPA (Hypothalamus pituitary gland adrenal cortex) axis - from adrenal cortex
how are fast actions implemented by the endocrine system - adrenal gland
adrenal gland - made of cortex and medulla
how can we activate a stress response using 2 systems
Fast acting
Slow acting
what is the fast acting system
when we make a split second decision about if something dangerous requires escaping it or facing it
we need certain level of energy resources which result from cell metabolism being stimulated to prepare for action
increase heart rate
decrease in digestive system
immune system is stimulated to use if we get injured
what are glucocorticoids
glucocorticoids hormones break down protein and fat metabolism
what is the slow acting stress response based on
the action of the endocrine system
hypothalamus sends trigger to anterior pituitary gland which sends a message to adrenal cortex which produces 2 types of hormones - glucocorticoids hormones and mineralocorticoids hormones
how is adrenaline triggered using the fast acting system
the trigger to produce adrenaline is coming from the hypothalamus which picks up a certain level of stress stimulus and sends the trigger to produce adrenaline vis spinal cord to adrenal medulla
what is the adrenal medulla
part of the autonomic nervous system
capable of secreting hormone adrenaline which activates sympathetic responses - increase in heart beat
what are mineralocorticoids
hormones that act on blood volume and pressure which tends to increase and they act on the balance of water which is reabsorbed by kidneys
what is the slow acting response as used by the HPA axis
HPA axis:
from hypothalamus to pituitary gland to adrenal cortex
glucocorticoids hormones like cortisol are produced
what is the action of glucocorticoids hormones
cortisol is a typical glucocorticoid hormone
glucocorticoids make sure glucose is released from fat and proteins by the liver
all systems that are not required to deal with stressor are turned off - reproductive functions are off
what happens if stress response is not shut down
if stress does not result in restoring homeostasis, results in chronic stress
continued production of glucocorticoids has a neurotoxic effect on the brain
what are the physical consequences of stress
Proteins are used up which results in muscle wasting and fatigue
Growth hormone is inhibited
Reproductive functions are inhibited
what are the cognitive consequences of stress
memory and learning
hippocampus deals with memory
the hippocampus contains high density of cortisol receptors - able to detect amount of cortisol in blood
constant high level of cortisol damages the hippocampus
hippocampus informs the hypothalamus when cortisol is too high and induces hypothalamus to induce pituitary gland to reduce amount of cortisol
too much cortisol can become toxic and neurones in hippocampus are unable to respond
then they are less able to inform hypothalamus that there is too much cortisol produced
