hormonal communication Flashcards
1
Q
What are endocrine glands?
A
Group of specialised cells which
secrete hormones
• Hormones are secreted directly
into the bloodstream
2
Q
List the major endocrine
glands in the body
A
- Pituitary gland
- Thyroid gland
- Adrenal gland
- Pineal gland
- Thymus
- Pancreas
- Testes
- Ovaries
3
Q
What does the pituitary gland
produce?
A
• Growth hormone, which controls growth of bones and muscles • Anti-diuretic hormone, which increases reabsorption of water in the kidneys • Gonadotrophins, which control development of ovaries and testes
4
Q
What is the purpose of the
pituitary gland?
A
It makes several hormones which in turn control the release of other hormones • The close proximity of the pituitary gland to the hypothalamus ensures that the nervous and hormonal responses the body are closely linked and coordinated
5
Q
What does the thyroid gland
produce?
A
Thyroxine which controls rate of
metabolism and rate that glucose is
used up in respiration, and promotes
growth
6
Q
What does the adrenal gland
produce?
A
Adrenaline which increases heart
and breathing rate and raises blood
sugar level
7
Q
What does the pineal gland
produce?
A
Melatonin which affects reproductive
development and daily cycles
8
Q
What does the thymus
produce?
A
Thymosin which promotes
production and maturation of white
blood cells
9
Q
What does the pancreas
produce?
A
• Insulin which converts excess glucose into glycogen in the liver • Glucagon which converts glycogen back into glucose in the live
10
Q
What do the testes produce?
A
Testosterone which controls sperm
production and secondary sexual
characteristics
11
Q
What do the ovaries produce?
A
Oestrogen which controls ovulation and secondary sexual characteristics • Progesterone which prepares the uterus lining for receiving an embryo
12
Q
What do exocrine glands do?
A
• e.g. those in the digestive system
• Secrete chemicals through ducts
into organs or to the surface of the
body
13
Q
Why are hormones referred to
as chemical messengers?
A
They carry information from one part of the body to another • Steroids, proteins, glycoproteins, polypeptides, amines, or tyrosine derivatives
14
Q
When are hormones secreted?
A
Hormones are secreted directly into the blood when a gland is stimulated • Can occur as a result of a change in concentration of a particular substance • Can also occur as the result of another hormone or a nerve impulse
15
Q
What happens after hormones
have been secreted?
A
They are transported in the blood plasma all over the body • The hormones diffuse out of the blood and bind to specific receptors for that hormone, found on the membranes or in the cytoplasm of cells in the target organs • Once bound to their receptors, the hormones stimulate the target cells to produce a response
16
Q
Describe steroid hormones
A
• Lipid-soluble • Pass through the lipid component of the cell membrane and bind to steroid hormone receptors to form a hormone-receptor complex • Receptors may be present in the cytoplasm or the nucleus • The hormone-receptor complex formed acts as a transcription factor which in turn facilitates or inhibits the transcription of a specific gene • Oestrogen is an example of a hormone which works in this way
17
Q
Describe non-steroid
hormones
A
• Hydrophilic so cannot pass directly though the cell membrane • Bind to specific receptors on the cell surface membrane of the target cell • This triggers a cascade reaction mediated by chemicals called second messengers • Adrenaline is an example of a hormone which works in this way
18
Q
Summarise the main
differences between the
actions of the normal and
nervous systems:
A
19
Q
What are the adrenal glands?
A
• 2 small glands that measure approximately 3cm in height and 5cm in length • Located on top of each kidney and are made up of two distinct parts surrounded by a capsule
20
Q
Describe the parts of the
adrenal glands
A
• The adrenal cortex: The outer region of the glands. This produces hormones that are vital to life, e.g. cortisol and aldosterone • The adrenal medulla: The inner region of the glands. This produces non-essential hormones, e.g. adrenaline which helps the body react to stress
21
Q
What are the 3 main types of
hormone produced by the
adrenal cortex?
A
• Glucocorticoids (release of these hormones is controlled by the hypothalamus) • Mineralocorticoids • Androgens
22
Q
Describe glucocorticoids
A
Cortisol: • Helps regulate metabolism by controlling how the body converts fats, proteins and carbohydrates into energy • Helps regulate blood pressure and cardiovascular function in response to stress Corticosterone: • Works with cortisol to regulate immune response and suppress inflammatory reactions
23
Q
Describe mineralocorticoids
A
Aldosterone: • Helps control blood pressure by maintaining balance between salt and water concentration in the blood and body fluids • Its release is mediated by signals triggered by the kidney
24
Q
Describe androgens
A
• Small amounts of male and female sex hormones are released • Their impact is relatively small compared with the larger amount of hormones e.f. oestrogen and testosterone released by the ovaries or testes after puberty • Still important, especially in women after menopause
25
Describe the hormones
secreted by the adrenal
medulla
```
Adrenaline:
• Increases the heart rate sending
blood quickly to the muscles and
brain
• Rapidly raises blood glucose
concentration by converting
glycogen to glucose in the liver
Noradrenaline:
• Works with adrenaline in response
to stress, producing effects e.g.
increased heart rate, widening of
pupils, widening of air passages in
the lungs, and the narrowing of
blood vessels in the non-essential
organs (resulting in higher blood
pressure)
```
26
What is the ‘fight or flight’
| response?
```
An instinct that all mammals
possess. When a potentially
dangerous situation is detected, the
body automatically triggers a series
of physical responses intended to
help mammals survive by preparing
the body to with fight, or flight.
```
27
What happens during the fight
| or flight response?
```
1. Threat is detected by autonomic
nervous system
2. Hypothalamus communicates
with the sympathetic nervous
system and the adrenal-cortical
system
3. Sympathetic nervous system
uses neuronal pathways, whilst
adrenal-cortical system uses
hormones in the blood stream
4. Combined effects of these 2
systems results in the fight or
flight response
```
28
What does the sympathetic
| nervous system do?
```
• Sends out impulses to glands and
smooth muscle
• Tells the adrenal medulla to release
adrenaline and noradrenaline into
the blood stream
• These ‘stress hormones’ cause
several changes in the body,
including an increased heart rate
```
29
What does the anterior
| pituitary gland do?
```
• Releases corticosteroid releasing
factor (CRF)
• Pituitary gland to secrete
adrenocorticotropic hormone
(ACTH)
• This travels in the bloodstream to
the adrenal cortex where it
activates the release of many
hormones that prepare the body to
deal with a threat
```
30
```
What are the purposes of these
‘fight or flight’ physiological
responses?
1. Heart rate increases
2. Pupils dilate
3. Arterioles in skin constrict
4. Blood glucose level increases
5. Smooth muscle of airways
relaxes
6. Non-essential systems (e.g.
digestion) shut down
7. Difficult focusing on small tasks
```
```
1. To pump more oxygenated blood
around the body
2. To take in as much light as
possible for better vision
3. More blood to major muscle
groups, brain, heart, and
muscles of ventilation
4. Increase respiration to provide
energy for muscle contraction
5. To allow more oxygen into the
lungs
6. To focus resources on
emergency functions
7. Brain solely focused only on
where threat is coming from
```
31
What is the effect of adrenaline
on the liver during the ‘fight or
flight’ response?
```
• Triggers the liver cells to undergo
glycogenolysis so that glucose is
released into the bloodstream
• Allows respiration to increase so
more energy is available for
muscle contraction
```
32
Why can’t adrenaline pass
| through cell membranes?
```
• Hydrophilic so cannot pass
through cell membranes
• Instead, binds with receptors on
the surface of a level cell
membrane and triggers a chain
reaction inside the cell
```
33
What types of glands are found
| in the pancreas?
```
Exocrine glands
• Produces enzymes and releases
them via a duct into the duodenum
• Most of the pancreases is made of
exocrine glandular tissue
• The enzymes and juice are
secreted into ducts which
eventually lead to the pancreatic
duct, and then are released into
the duodenum
• Important types of enzymes
produced: amylases, proteases,
and lipases
Endocrine glands
• Produces hormones and releases
them into the blood
• Insulin and glucagon are
produced, which play an essential
role in controlling blood glucose
concentration
• Found in small regions of
endocrine tissue within the
exocrine tissue, called ‘Islets of
Langerhans’
• Alpha cells produce and secrete
glucagon
• Beta cells produce and secrete
insuli
```
34
How is blood glucose
| concentration increased?
```
• Diet - eating carbohydrate and
sugar rich foods; they will be
broken down in the digestive
system to release glucose
• Glycogenolysis - glycogen stored
in the liver and muscle cells is
broken down into glucose
• Gluconeogenesis - the
production of glucose from noncarbohydrate sources, e.g. the
liver is able to make glucose from
glycerol and amino acids
```
35
How is blood glucose
| concentration decreased?
```
• Respiration - the higher the level
of physical activity, the higher the
demand for glucose, and the
greater the decrease in blood
glucose concentration
• Glycogenesis - when blood
glucose concentration is too high,
excess glucose taken in through
the diet is converted into glycogen
and stored in the liver
```
36
What happens if blood
| concentration is too low?
```
The alpha cells of the islets of
Langerhans detect this and respond
by secreting glucagon into the
bloodstream
• Only liver cells and fat cells have
glucagon receptors
```
37
How does glucagon raise
| blood glucose concentration?
• Glycogenolysis
• Reducing the amount of glucose
reabsorbed by liver cells
• Increasing gluconeogenesis
38
What happens when blood
| glucose level is too high?
```
The beta cells of the islets of
Langerhans detect this, and secrete
insulin into the bloodstream
• Nearly all body cells (excluding red
blood cells) have insulin receptors
on their cell surface membrane
```
39
How does insulin decrease
| blood concentration?
```
• Increasing the rate of absorption
of glucose by cells
• Increasing the respiratory rate of
cells
• Increasing the rate of glycogenesis
• Increasing the rate of glucose to
fat conversion
• Inhibiting the release of glucagon
by the alpha cells in the islets of
Langerhans
Insulin is broken down by enzymes
in the cells of the liver. Therefore, for
it to maintain its effect, it has to
constantly be secreted
```
40
How is insulin secreted?
```
1. At normal blood glucose
concentration levels, potassium
channels in the plasma
membranes of beta cells are
open and potassium ions diffuse
out of the cell. The inside of the
cell is at a potential of -70mV
with respect to the outside of the
cell
2. When blood glucose
concentration rises, glucose
enters the cell by a glucose
transporter
3. The glucose is metabolised
inside the mitochondria, resulting
in the production of ATP
4. The ATP binds to the potassium
channels and causes them to
close. They are known as ATPsensitive potassium channels
5. As potassium ions can no longer
diffuse out of the cells, the
potential difference reduces to
around -30mV, and
depolarisation occurs
6. Depolarisation causes the
voltage-gated calcium ion canals
to open
7. Calcium ions enter the cell and
cause secretory vesicles to
release the insulin they contain
by exocytosis
```
41
What is diabetes?
A chronic disease in which the
patient is unable to metabolise
carbohydrates properly, in particular
glucose
42
What are the common
| symptoms of diabetes?
```
• High blood glucose concentration
• Glucose present in urine
• Excessive need to urinate
(polyuria)
• Excessive thirst (polydipsia)
• Constant hunger
• Weight loss
• Blurred vision
• Tiredness
```
43
Describe Type 1 diabetes
```
The ß cells in the islets of
Langerhans don’t produce insulin
Cause by an autoimmune response
where the body’s own immune
system attacks the ß cells
Normally begins in childhood
```
44
Describe Type 2 diabtes
```
Either the person’s ß cells don’t
produce enough insulin, or the
person’s body cells don't respond
properly to insulin
Often because the glycoprotein
insulin receptor on the cell
membrane doesn’t work properly
```
45
How is Type 1 diabetes
| treated?
Regular injections of insulin
46
How is Type 2 diabetes
| treated?
```
• Regulation of carbohydrate intake
through diet
• Increasing exercise
• Overweight people are
encouraged to lose weight
• Drugs that stimulate insulin
production or slow down the rate
of glucose absorption
• Insulin injections
```
47
What are the advantages of
using bacteria to produce
human insulin rather than
using animal insulin?
```
• Human insulin is less likely to
cause allergic reactions
• Insulin can be produced in higher
quantities
• Production is cheaper
• No problems with animal ethics
```
48
What would be the advantages
of using stem cells to treat
diabetes?
```
• Donor availability wouldn’t be an
issue
• Reduced likelihood of rejection
problems
• People no longer have to inject
themselves with insulin
```
49
Describe the action of
| adrenaline on liver cells
```
1. When adrenaline binds to its
receptor, the enzyme adenylyl
cyclase (also present int he cell
membrane) is activated
2. Adenylyl cyclase triggers the
conversion of ATP into cyclic
adenosine mono-phosphate
(cAMP) on the inner surface of
the cell membrane in the
cytoplasm
3. The increase in cAMP levels
activates specific enzymes
called protein kinases which
phosphorylate and activate other
enzymes that trigger the
conversion of glycogen into
glucos
```
50
Why is this model of hormone
action known as the second
messenger model?
```
• The hormone (adrenaline) is the
first messenger
• cAMP is the second messenger
• One hormone molecule can cause
many cAMP molecules to be
formed
• At each stage, number of
molecules involved increases, so
the process is said to have a
cascade effect
```
51
What are the functions of the
| pancreas?
```
• Exocrine gland - to produce
enzymes and release them via a
duct into the duodenum
• Endocrine gland - to produce
hormones and release them into
the blood
```
52
Describe the role of the
| pancreas as an exocrine gland
• Responsible for producing
digestive enzymes
• Produces pancreatic juice
53
Describe the enzymes
| produced by the pancreas
```
• Amylases - break down starch into
simple sugars
• Proteases - break down proteins
into amino acids
• Lipases - break down lipids into
fatty acids and glycerol
```
54
Describe the role of the
pancreas as an endocrine
gland
The islets of Langerhans are small
regions of endocrine tissue within
the major exocrine tissue
55
What are the cells found within
| the islets of Langerhans?
• ⍺ cells - produce and secrete
glucagon
• ß cells - produce and secrete
insulin
56
How is heart rate controlled?
Involuntary and controlled by the
autonomic nervous system.The
medulla oblongata in the brain is
responsible for controlling heart rate
57
How does the medulla
oblongata link to the sinoatrial
node (SAN)?
```
Two centres within the medulla
oblongata linked to SAN by motor
neurones:
• Cardioacceloratory centre:
increases heart rate by sending
imputes through sympathetic
nervous system. These impulses
are transmitted by the accelerator
nerve
• Cardioinhibitory centre: decreases
heart rate by sending impulses
through parasympathetic nervous
system. These impulses are
transmitted by the vagus nerve
```
58
How is a centre stimulated?
```
By information received by receptors
in the blood vessels. Two types that
provide information that affects
heart rate:
• Baroreceptors
• Chemoreceptors
```
59
Describe baroreceptors
```
• Pressure receptors
• Detect changes in blood pressure
• Present in aorta, vena cava and
carotid arteries
• e.g. if blood pressure is low, the
heart rate needs to increase to
prevent fainting
```
60
Describe chemoreceptors
```
• Chemical receptors
• Detect changes in the level of
particular chemicals in the blood
e.g. CO2
• Present in aorta, carotid artery and
the medulla
```
61
How do chemoreceptors
| work?
```
Sensitive to changes in the pH level
of the blood
• If CO2 level in the blood increases,
pH of the blood decreases
because carbonic acid is formed
when CO2 interacts with water in
the blood
1. If chemoreceptor detect a
decrease in blood pH, frequency
of imputes to SAN via
sympathetic nervous system
increases
2. SAN increases heart rate
3. Blood flows more quickly to the
lungs so CO2 can be exhaled
4. CO2 level returns to normal
• If CO2 level in blood decreases,
the pH of the blood rises
1. Reduction in the frequency of
nerve impulses being sent to the
medulla oblongata
2. Reduces frequency of impulses
being sent to SAN via the
sympathetic nervous system
3. Heart rate decreases back to
normal level
```
62
How do baroreceptors work?
```
They detect changes in pressure
If blood pressure is too high,
impulses are sent to the medulla
oblongata to decrease heart rate
back to normal
• Decreasing heart rate: impulses
sent along parasympathetic
neurones to the SAN
• Increasing heart rate: impulses
sent along sympathetic neurones
to SAN
```
63
How is heart rate influenced by
| hormones?
```
Adrenaline and noradrenaline are
released when the body is stressed
These affect the pacemaker of the
heart and increase the heart rate by
increasing the frequency of impulses
produced by the SAN
```
