Endocrine System Flashcards
What is a hormone?
Molecules that are released by endocrine glands directly onto the blood, act as messengers, carrying a signal from the endocrine gland to a specific target organ or tissue
How does endocrine system transport its signals?
Blood circulation system is used, transports materials all over the body
What is an endocrine gland?
A gland that secretes hormones directly into the blood, gave no ducts
What is an exocrine gland?
A gland that secretes molecules into a duct that carries the molecules to where they are used
How does is a hormone signal targeted?
Cells receive hormone signal must possess specific complimentary receptor on plasma membrane, hormone binds to receptor hormone only affects these cells, target cells
What is a target cell?
Those that poses a specific receptor on their cell surface membrane. Shape is complimentary to shape if hormone molecule
What are the two types of hormones?
Protein and peptide hormones and derivatives of amino acids
Steroid hormones
How do different types of hormone behave?
Proteins are not soluble so cannot enter cell, steroids however can pass into cell and have direct effect on DNA in the nucleus
What is adrenaline?
An amino acid derivative, causes fight or flight response, unable to enter cell,
How can adrenaline hormone have an effect on a cell?
Adrenaline receptor on outside of cell is associated with enzyme in the inner surface of the cell surface membrane, adenyl cyclase. When adrenaline binds to receptor as the first messenger, this activates enzyme adenyl cyclase, which converts ATP to cyclic AMP (cAMP), which is the second messenger inside the cell, that can then cause effect inside the cell by activating enzyme action
What is the first messenger?
The hormone that transmits a signal around the body
What is the second messenger?
cAMP which transmits a second signal inside the cell
Where are the adrenal gland found?
Found lying to the anterior or the kidneys m, one on each side, each gland can be divided into medulla and cortex region
Where are glands on the endocrine system found?
Pituitary gland in the brain Thymus Thyroid gland Adrenal glands Pancreas Ovaries
Where is the adrenal medulla found and what are its functions?
Found in the centre of the gland, manufacture and release adrenaline in response to stress such as pain or shock
What are the effects of adrenaline?
Relax smooth muscle in bronchioles, and increased breathing rate to ensure blood is fully oxygenated
Increase heart rate and stroke volume, increases cardiac output, faster and increased delivery
Constricting blood flow to digestive system, leaves more oxygen/glucose for muscle action
Raise blood pressure
Dilation of pupils
Conversion of glycogen to glucose
Body hairs erect
What is the role of the adrenal vortex?
Uses cholesterol to produce certain steroid hormones m, such as mineralocorticods that help control concentrations of sodium and potassium in the blood
Glucocorticoids that help contribute metabolism of carbohydrates and proteins in the liver
Why must target cells have a specific receptor?
Specific receptor for protein to bind, enables hormone to activate process inside the cell, complimentary so hormone only effects target cells
What is the pancreas?
Small organ below stomach? Has both endocrine and exocrine functions as it secretes both enzymes into pancreatic duct and hormones into the blood
What is the exocrine function of the pancreas?
Cells manufacture and release digestive enzymes into the ting tubules that surround the cells, tubules join to make the is pancreatic duct which carries fluid containing the enzymes into the first part of the small intestine
What enzymes are found in the pancreatic juice?
Amylase, a carbohydrase
Trypsinogen, an inactive protease
Lipase
Sodium hydrogencarbonate which make it alkaline to neutralise contents in small intestine from acid environment of the stomach
What is the endocrine function of the pancreas?
Islets of Langerhans contain alpha cells which manufacture hormone glucagon and beta cells which manufacture hormone insulin. Well supplied with blood capillaries and hormones are secretes directly into the blood
What are the Janet’s of Langerhans?
Small patches of tissue in the pancreas that have endocrine function
What is insulin?
Hormone released by beta cells that cause blood glucose level to fall
What is glucagon?
Hormone that causes blood glucose levels to rise
How is blood glucose concentration controlled?
Carefully regulated by cells in the islets of Langerhans. Normal concentration is 90mg 100cm
If concentration rises or falls away from the acceptable concentrations then the a and B cells detect it and release a hormone
What happens if blood glucose rises too high?
Detected by B cells, secrete insulin into the blood, target the hepatocytes, muscle cells brain etc, which possesses complementary receptor for insulin. cAMP is activated in cells with has number of effects:
More glucose channels
More glucose enters cell
Glucose converted to glycogen
Glucose converted to fats
Glucose used in respiration. Increased entry of glucose reduces blood glucose concentration
What is glycogenesis?
Formation of glycogen from glucose
What happens if blood glucose concentration falls too low?
Detected by a cells, secretes hormone glucagon into blood, targets hepatocytes with complimentary receptor, causes effects:
Conversion of glycogen to glucose
Use if more fatty acids in respiration
Production of glucose by conversion from amino acids and fats
What is glycogenolysis?
Conversion of glycogen to glucose
What is gluconeogenesis?
Production of glucose from amino acids and fats
Why do hepatocytes have specialised receptors for both insulin and glucagon?
Hepatocytes contain a store if glycogen, when excess of glucose absorb glucose and make more glycogen, when low glucose, glycogen broken down and released into the blood
Why is it important to regulate insulin levels?
Insulin reduces blood glucose concentration, if too high, insulin release is important, if concentration drops too low it is important that secretion stops
How is secretion of insulin controlled?
B cell membranes contain calcium ion channels and potassium ion channels
Potassium channels are open normally, diffuse out of cell making it more negative, pd is -70mV
When glucose concentration is high, glucose molecules diffuse into the cell
Glucose used in metabolism to produce ATP
Extra ATP causes potassium channels to close, can no longer diffuse out, alter potential difference, less negative
Change in potential difference cause voltage gated calcium ion channels to open
Calcium ion channels move in and cause vesicles contains to move to surface membrane and fuse to release insulin by exocytosis
What is diabetes mellitus?
A disease in blood glucose concentrations cannot be controlled effectively. Normally kept under control by negative feedback
What is hyperglycaemia?
State in which the blood glucose concentration is too high
What is hypoglycaemia?
State in which the blood glucose concentration is too low
What is type 1 diabetes?
Insulin dependent diabetes, starts in childhood, result of an autoimmune response, body’s immune system attached B cells and destroys them or as result of viral attack. No longer able to manufacture insulin, and so can it store excess glucose and glycogen
What is type 2 diabetes?
Non insulin dependent, insulin is still produces by responsiveness to insulin declines, as number of specific receptor declined and cells lose ability to report to insulin p
What are the causes of type 2 diabetes?
Obesity
Diet high in sugars
Asian or Afro Caribbean
Family history
What are the treatments for type 2 diabetes?
Careful monitoring and control of the diet to match intake and use. May eventually be supplemented with insulin injections
How can type 1 diabetes be treated?
Insulin injections, blood glucose concentration monitored carefully. Insulting dowse administered to ensure glucose concentration remains fairly stable
Where is insulin sourced?
Used to be from pancreas of animals, now produced by genetically engineered bacteria to manufacture human insulin
Ha re genetically engineered bacteria?
Those in which DNA has been altered, here gene coding for human insulin has been inserted into DNA of the bacteria
What are the advantages it using insulin from bacteria?
Exact copy if human insulin so more effective
Less chance of developing tolerance
Less risk of infection
Less chance of rejection
Cheaper to manufacture
More adaptable to demand
People less likely to have moral objections
What are stem cells?
Unspecialised cells that have the potential to develop into any type of cell
How can stem cells be used to treat diabetes? S
Stem cells not yet differentiated, can be induced to develop into variety of cell types. Precursor cells found in pancreas of mice, are capable of developing into a varied if cell types, if similar found in human pancreas could be used to produce new B cells for patients with diabetes
Why must insulin be injected rather than taken orally?
Hormone so is a protein, would be digested in stomach
Compare mechanism if insulin secretin with secretion of neurotransmitter at synapse
Stimulus: high glucose conc/arrival of action potential
Membrane:potassium channels close/sodium channels open
Ions:potassium cannot leave/sodium diffuses in
Membrane potential: becomes less negative with respect to outside
Calcium channel: open
Ions: diffuse in
Vesicles: move to membrane and fuse, contents released by exocytosis
What is the role of the heart?
Pumps blood around the circulatory system, blood supplies tissues with oxygen and nutrients,removes waste products so they don’t accumulate and inhibit cell metabolism. More oxygen required and faster waste removal on more active cells
What is cell metabolism?
Result of chemical reactions taking place in the cytoplasm
How does the heart adapt to supply more oxygen and glucose?
Increase in heart rates and stroke volume, increase in strength of contractions
How is the heart rate controlled?
Heart is myogenic, has own pace maker, SAN, imitates action potential that travels over atria walls to AVN and down to Purkyne fibres to the ventricles causing them to contract. Heart is supplied by nerves from medulla oblongata that connect to SAN, can affect frequency of contractions, can also respond to adrenaline
What is the medulla oblongata?
Found at the base of the brain, region of the brain that coordinates the invincibility functions of the body such as breathing rate and heart rate
What nerves connect the medulla oblongata and the SAN?
Vagus nerve, which reduces heart rate and accelerator nerve, which increased heart rate
What is the cardiovascular centre?
Specific region of medulla oblongata that receives sensory input about the levels of physical activity, blood c02 concentration and blood pressure, send nerve impulses to SAN to alter frequency of excitation waves
What are the factors affecting heart rate?
Movement of limbs detected by stretch rectors, send impulses to CVC to increase heat rate, more co2 produced, detected by chemoreceptors, stimulated increase in heart rate. When we stop exercising co2 levels fall, reduces activity of accelerator pathway, heart rate falls
Adrenaline secretes in response to stress, increases heart rate to prepare body for activity
Blood pressure monitored by stretch receptors in carotid sinus, if blood pressure too high, vagus nerve excited to reduce hr
How is carbon dioxide concentration monitored?
Changes in pH detected by chemoreceptors in the carotid arteries, aorta and brain, send impulses to CVC -which increases heart rate
What mechanisms control heart rate (short)
Stretch receptors in muscles
Low pH in blood
High blood pressure in carotid sinus
Adrenaline in blood
What is a pacemaker?
Region of tissue in the right atrium wall that can generate an impulse and initiates the contraction of the chambers
What is an artificial pacemaker?
Fitted if mechanism controlling heart rate fails, device that delivers electrical impulse vote the heat muscle
Why must heart rate be able to respond to increase in activity?
Active cells use more energy, so need more ATP, so respite more, need more oxygen and glucose. Heart reTe rises to increase cardiac output, more blood pumped per minute, to supply more to muscles and removed extra co2 and lactate produced
