Hormonal Communication Flashcards
What are the types of hormone?
Protein and peptide hormones
Steroid hormones
Example of protein hormones?
Adrenaline, insulin, glucagon
Example of steroid hormones?
Oestrogen and testosterone
Which hormone can enter the cell?
Steroid hormones
Why can’t protein hormones enter the cell?
Proteins are not soluble in the phospholipid membrane
What is the endocrine system?
A communication system using hormones as signalling molecules
Where are hormones released from?
Endocrine glands
Describe endocrine glands?
Ductless
Consist of group of cells that manufacture and release the hormone directly into the blood in capillaries running through the gland
Examples of endocrine glands?
Pituitary gland Thyroid gland Thymus Adrenal gland Pancreas Ovaries and testes
Example of exocrine gland?
Saliva gland
How are hormones transported?
Via the bloodstream
All over the body
What are target cells?
The cells that revive the endocrine signal
What are non-steroid hormones also know as?
First messengers
What do the first messengers do?
Signalling molecules outside the cell
Bind to the cell surface membrane
Initiate the release of the second messenger within the cell
What is usually activated when the non-steroid hormone binds to the cell?
The G protein
What does the G- protein do?
Activate an effector molecule- usually adenyl cyclase
What is the role of the effector molecule?
Usually an enzyme
Converts an inactive molecule into the active second messenger
What is the role of adenyl cyclase?
Converts ATP to cyclic AMP (cAMP)
What may the second messenger do?
Act directly on another protein such as an ion channel
Or it may initiate a cascade of enzyme- controlled reactions that alter the activity of the cell
Where are the adrenal glands found?
Anterior to the kidneys
What is the structure of the adrenal glands?
Each gland is divided into the outer adrenal cortex and the inner adrenal medulla
What are the layers in the adrenal cortex?
Zona glomerulosa
Zone fasciculata
Zonal reticularis
What is the zona glomerulosa?
Outermost layer
Secretes mineralocorticoids such as aldosterone
What is the zona fasciculata?
Middle layer
Secretes glucocorticois such as cortisol
What is the zona reticularis?
Innermost layer
Secretes precursor molecules- used to make sex hormones
What does the adrenal medulla secrete?
Adrenaline and noradrenaline
What is the very outer layer of the adrenal gland?
Capsule
What type of hormones are those released from the adrenal glands?
Steroid hormones
Summary of the action of steroid hormones from the adrenal cortex?
Hormone passes through the cell membrane and binds with a specific receptor in the cytoplasm.
What happens in the cell once the steroid hormone has bind to the receptor?
The receptor- steroid hormone complex enters the nucleus and binds to a receptor on the chromosome. This stimulates the production of mRNA for protein synthesis.
What is the role of mineralocorticoids (aldosterone) ?
Helps to control blood sodium and potassium concentrations. There also help to maintain blood pressure.
How does aldosterone carry out its function?
It acts on the cells of the distal convoluted tubule and collecting ducts.
Role of glucocorticoids (cortisol) ?
Helps to control the metabolism of carbohydrates, fats and proteins in the liver.
When is cortisol released?
As a response to stress or a result of low blood glucose concentration.
How does cortisol carry out its function?
By stimulating the production of glucose from stored compounds in the liver
Where else can cortisol be real eased from?
The zona reticularis, only if the correct enzymes are present
Where are the precursor androgens taken up? What is their function?
Ovaries and testes and converted to sex hormones.
Regulate the production of gametes.
Describe adrenaline?
Polar molecule
From the amino acid tyrosine
Cannot enter cells through the plasma membrane
What is the effect of adrenaline not entering the cell?
As many cells have adrenaline receptors the effects of adrenaline are wide spread
What is the main role of adrenaline?
To prepare the body for activity
What are the effects of adrenaline?
Increases heart rate and stroke volume Dilates pupils Relaxes smooth muscle in bronchioles Increases mental awareness Inhibits gut action Causes hairs to stand erect Converts glycogen to glucose
What is unusual about the pancreas?
It has both endocrine and exocrine functions.
What are the two secretions from the pancreas?
Pancreatic juices containing digestive enzymes
Hormones secretes from Islet of langerhans
What is an acinus?
A group of exocrine cells in the pancreas surrounded by tubules
What do the tubules from the acini form?
Intralobular ducts that combine to make up the pancreatic duct
Role of pancreatic duct?
Transports pancreatic juices containing enzymes to the small intestine
What enzymes are in the pancreatic juices?
Amylase
Trypsinogen
Lipase
What does the pancreatic juices also contain?
Sodium hydrogencarbonate- neutralises
What does the islet of Langerhans contain?
Alpha and beta cells
- endocrine function
What do the alpha cells secrete?
Glucagon
What do the beta cells secrete?
Insulin
What does the beta membrane contain?
Potassium and calcium ion channels
When is insulin released?
When blood glucose concentration is too high
Are the potassium ion channels on a beta cell normally open or closed?
Potassium channels are normally open to allow potassium ions to flow out
How is insulin released? Part 1
When glucose concentration increases glucose enters the beta cell. This glucose metabolised to ATP. ATP closes the P ion channels.
How is insulin released? Part 2
The accumulation of protein ions alters the potential difference across the beta membrane which causes Ca channels to open. Ca+ causes the vesicles of insulin the fuse with the membrane releasing the insulin by exocytosis
What is the normal blood glucose concentration?
Between 4-6
What is a person said to be if their blood glucose concentration drops below 4 mmol dm-3?
Hypoglycaemic
What is hypoglycaemia?
An inadequate delivery of glucose to the body tissues and brain
Symptoms of hypoglycaemia?
Mild- tiredness and irritability
Severe- impairment of brain function, confusion, seizures, unconsciousness and death
What is hyperglycaemia?
If blood glucose concentration is allowed to rise too high
When is glucagon released?
If blood concentration is too low
How many amino acids does insulin contain?
51
What enzyme is activated when when insulin binds to an insulin receptor?
Tyrosine kinase
What effects does insulin have on the cell?
Vesicles containing glucose transporter proteins fuse with membrane- more glucose enters cell
Glucose in the cell is converted to glycogen
More glucose is converted to fats and used in respiration
Where is a low blood glucose concentration detected?
Alpha cells in islet of langerhans
What are insulins target cells?
Liver, muscle and other body cells including those in the brain
How many amino acids does glucagon contain?
29
What are glucagons target cells?
Hepatocytes
What are the effects of glucagon?
Glycogen is converted into glucose
More fatty acids used in respiration
Amino acids and fats are converted into glucose
What is the process of glycogen into glucose?
Glycogenolysis
What is the process of converting glucose to glycogen?
Glycogenesis
What is the process of amino acids and fats converted into glucose?
Gluconeogenesis
How can the hormones insulin and glucagon be described?
Antagonistic
What is diabetes mellitus?
A condition in which the body is no longer able to produce sufficient insulin to control its blood glucose concentration
When are diabetic people at risk?
After a meal rich in carbohydrates and sugars
After exercise or fasting
How is type 1 diabetes also known?
Insulin dependent or juvenile onset
What is thought to be the cause of type 1 diabetes?
An autoimmune response
In which the body’s immune system attacks beta cells
Or
A viral attack
What can a person with type 1 diabetes no longer do?
Synthesise sufficient insulin
Store glucose as glycogen
What is type 2 diabetes also known as?
Non insulin dependent
What problem occurs with type 2 diabetes?
As people age their receptors become less responsive to the insulin hormone
What is the blood glucose concentration like in a person with type 2 diabetes?
Permanently raised
Danger of a high blood glucose concentration
Organ damage
What factors can bring an early onset of type 2 diabetes?
Obesity Lack of exercise High refined sugar diet Family history Being of Asian or Afro-Caribbean origin
How is type 1 diabetes normally treated?
Insulin injections
What are the alternatives to insulin injections?
Insulin pump therapy
Islet cell transplantation
Pancreas transplant
What is an insulin pump?
A small device which pumps insulin into the bloodstream through a needle permanently inserted under the skin
What is islet cell transplantation?
Healthy beta cells are implanted from a dead donor
What has new research into type 1 diabetes treatment found?
That stem cells could be used to grow new islets of langerhans
How is type 2 diabetes usually treated?
Life style changes- diet, exercise and weight loss
How can insulin be gained?
Extracted from the pancreas of animals
By genetic modification of Escherichia bacteria
What are the advantages of the genetic modification method?
Less chance of rejection from immune system
Lower risk of infection
It is cheaper to manufacture
More morally accepted
