HORMONAL COMMUNICATION Flashcards
What is a hormone
Chemical messenger:
- secreted from endocrine gland directly into bloodstream
- occurs due to changes in concentration of a substance
- travel in blood plasma, carry signal from endocrine gland to specific target
- bind to specific target cells
What are endocrine glands
Group of cells, secrete hormones directly into blood capillaries (no ducts)
E.g. pancreas, adrenal glands
What are exocrine glands
Secretes molecules (not hormones) into ducts E.g. saliva, bile, digestive, enzymes
What are examples of non-steroid hormones
POLAR
E.g. adrenaline, insulin, ADH
First messengers
Explain what is meant by first messenger
Non-Steroid hormones
Bind to receptor on cell surface membrane, releases second messenger inside the cell
Often act via G protein in the membrane
Explain what is meant by a second messenger
Stimulate a change in the activity of the cell
In many cases, enzyme adenylyl cyclase is an effector molecule that converts ATP into cyclic AMP
May activate enzyme controlled reactions
Examples of steroid hormones
NON POLAR
E.g. oestrogen, testosterone
What are steroid hormones
Hydrophobic- can dissolve in hydrophobic region of phospholipid (simple diffusion)
Explain a steroid hormone
Passes directly through cell surface membrane and binds with specific receptor in the cytoplasm
This complex enters nucleus of the cell and acts as transcription factor on DNA
Either promotes or inhibits transcription of gene
Where are the adrenal glands located
Just above kidneys
Divided into outer adrenal cortex and inner adrenal medulla
How many layers are in the adrenal cortex
3
All secreting steroid hormones
What hormone does the first layer of the adrenal cortex secrete and what is its function
Mineralocorticoids
E.g. aldosterone
Controls levels of Na+ and K+ in the blood
Increases absorption of Na+ and decrease for K+
Maintains blood pressure
What hormone does the second layer of the adrenal cortex secrete and what is its function
Glucocoticoids
E.g. cortisol
Released in response to stress or low blood glucose levels
Regulates immune response
What hormone does the third layer of the adrenal cortex secrete and what is its function
Androgens
E.g. precursors for sex hormones
What does the adrenal medulla secrete
Non steroid hormones
What hormones are secreted by the adrenal medulla
Adrenaline and noradrenaline (fight or flight)
Function of adrenaline
Increases heart rate, increase blood glucose (glycogen broken dow. in liver)
Function of noradrenaline
Works with adrenaline in response to stress, producing effects of an increased heart rate, increases blood pressure
When are hormones in the medulla secreted
When the sympathetic nervous system is stimulated
In response to stress
What is the exocrine function of the pancreas
Location- acinus (cells found in groups surrounding. tubules)
Details- pancreatic juice released from cells and secreted into tubules at centre of group. Join to form interlobular ducts which join to from pancreatic ducts, joins to duodenum
Endocrine function of the pancreas
Location- Islets of Langerhan- group of cells in pancreas
Details- alpha cells produce glucagon, beta cells produce insulin
Hormones secreted directly into blood stream
What is diabetes
Where someone is unable to metabolise carbohydrates properly, particularly glucose
Symptoms of diabetes
Extreme fatigue
Blurry vision
Weight loss
Explain hypoglycaemia
Mild- tiredness and irritability
Severe- impairment of brain function and confusion, could lead to seizures, unconsciousness
Decreased blood glucose concentration
Details of type 1 diabetes
Unable to produce insulin (B-cells on isle of Langerhan dent produce insulin)
Cannot be prevented or cures, treatment available
Can arise as result of an autoimmune disease
Details of type 2 diabetes
Cannot effectively use insulin and control blood sugar levels
Either because:
1. B-cells don’t produce enough insulin
2. Cells don’t respond properly to insulin
Therefore cells lose responsiveness to insulin so cannot take up enough glucose, leaving it in bloodstream
Result of obesity and decreased physical activity
Treatment for type 1
Regular injections of insulin
Regularly test blood glucose levels
Increased insulin= increased glucose absorbed by cells
Treatment for type 2
Match carbohydrate level to exercise level
Over weight people encouraged to lose weight
Drugs- stimulate insulin production
What is hyperglycaemia
Permanent high glucose concentrations can lead to organ damage
Advantages go using GM bacteria to produce insulin
Human insulin produced in pure form |(|decreased chance of causing allergic reaction)
Insulin produced in higher quantities
Production costs are cheaper
Potential use of stem cells in diabetes treatment
Totipotent stem cells have potential to grow into any type of body cells Stem cells would be taken from embryos (potential human life) // embryos used would have been destroyed as 'spare' embryos from infertility treatment ]=
Benefits of stem cells treatment
Small no. of embryos used for lots of Px
Px don’t need to inject insulin
Decreased chance of rejection from transplant
Regulation of insulin levels (beta cells)
- K+ channels on plasma men open, K+ diffuses (facilitated) out, giving resting mem potential of -70mV
- glucose enters cell through glucose transporter proteins when levels are high
- glucose phosphorylated by enzyme glucokinase. Metabolised by ATP
- K+ channels close when ATP levels are too high
- K+ cannot diffuse out= mem potential= -30mV
- V-gated Ca2+ channels open in response to mem potential change, Ca2+ enter cell
- Ca2+ cause vesicles containing insulin move and fuse with mem, release insulin
EXOCYTOSIS
Similarities between release of insulin from beta cells and transmission of nerve impulse
V-gated calcium channels
Vesicles
-70mV resting potential
Exocytosis
Differences between release of insulin from beta cells and transmission of nerve impulse
Different enzymes
Insulin released into bloodstream =, acetylcholinesterase into synapse
Response to high glucose levels
Beta cells
Insulin secreted
Targets all cells
Increases glucose transporter proteins on mem
Glycogensis- glucose converted to glycogen in liver
Glucose converted into fats
Glucose for respiration
Response to low blood glucose levels
Alpha cells
Glucagon sevcreted
Targets liver and fat cells
Glycogenolysis- glycogen-> glucose in liver + released into bloodstream
Gluconeogenesis- amino acids + glycerol converted into glucose in the liver
Fatty acids used in respiration
What are insulin and glucagon
Antagonistic- have opposite effects on glucose concentrations
Inhibit effects of opposing hormone