Hormones Flashcards
What are the differences between a synpse and endocrine release?
Synpatic:
- Targeting achieved by specific ‘wiring’
- Fastest transmission speed, to minimise response delays
- Good for brief responses
- Across synapses
- Neurotransmitters
Endocrine:
- Released into the blood
Target by presence of specific receptors on target cells
- Relatively slow, but long lasting action (moving through bloodstream as opposed to moving down axons)
- Good for widespread and sustained responses
- Hormones
- Through the bloodstream
What are endocrine glands?
Cells that secrete horomes which are carried into the bloodsteam and act upon target cells
What are the major endocrine glands?
Hypothalamus, Pituitary, thyroid, adrenal, pineal, pancreas, parathyroid
What is Paracrine communication?
Paracrines transmission through extracellular fluid
- Limited to local area, target cells must have appropriate receptors
What is Autocrine communication?
Autocrine transmission through extracellular fluid
- limited to the cell that secretes the chemical signal
What is endocrine communication?
Hormone Transmission through the bloodstream
- Target cells mainly in other distant tissues and organs and must have appropriate receptors
What are water soluble hormones?
They are mostly peptides (75%) which are small chains of amino acids
- Some catecholamines
- Adrenaline and noradrenaline
Storage: Made and stored until required (released by exocytosis)
Transport: Travel dissolved in the blood Fast process (milliseconds to mins)
What are lipid soluble hormones?
Steroids (thyroid including both T3 and T4)
- Cortisol
Storage: Ateroids are made from cholesterol as required (not stored)
Thyroid hormones are made in thyroid cells and stored until required (This storage is unusual for lipid-soluble hormones)
Transport: Travel in the blood bound to a carrier protein Slow process (hours to days)
What is the cellular response to receptor activation for water soluble hormones (peptides and catecholamines)
- Water-soluble hormone binds to cell surface receptor
- Hormone binding allows activation of associated G-protein
- G-protein activates/inhibits adenylyl cyclase, or increases intracellular Ca2+
- Second messenger production/reduction e.g. cyclic AMP (cAMP) or Ca2+
- Downstream proteins/pathways are activated or deactivated
Cellular response to activation of receptors with lipid soluble hormones (steroid and thyroid)
Sits on carrier protein and is transported around the blood
- Lipid-soluble hormone dissociates from carrier protein
- Hormone diffuses across cell membrane
- Hormone binds to Intracellular receptor (in cytoplasm or in the nucleus)
- Hormone receptor complex acts as a specific transcription factor
- Target gene is activated (causes a change in the way this gene is expressed)
- New protein is generated by translation of mRNA
- New protein mediates cell specific response (slow process)
What does amount of hormone in the blood depend on?
Rate of hormone secretion
Rate of removal from blood
What is the pancreas?
A exocrine and endocrine gland in which pancreatic islet beta cells secrete insulin and pancreatic alpha cells secrete glucagon
What are the two states of the body in the day (to do wilth glucose)
Fed and fasting state
Fed state:
- cellular uptake of nutrients & anabolic metabolism (synthesis of glycogen, protein and fat)
Fasting state:
- mobilisation of nutrients & catabolic metabolism (breakdown of glycogen, protein and fat)
- Get the stored glucose out of our cells so we can use it while we are not taking food in
How is blood glucose regulated?
Insulin (beta) and glucagon (alpha) maintain blood glucose conc between 70-110mg dL-1 (reference range)
What is the insulin secretion pathway?
Increase in blood glucose is detected by beta cells
- This causes a release of insulin
- Insulin travels through blood to target cells
- Cells need to right receptor
Insulin is a peptide hormones (water soluble) moves freely throughout the bloodstream
What does insulin secretion result in?
Liver cells:
- Glucose uptake increases and this is synthesised into glycogen and fat synthesis
Muscle and adipose cells:
- Glucose up take is increased and there is fat synthesis as well as glycogen and protein synthesis
What us the glucagon secretion pathway?
Decrease in blood glucose is detected by alpha cells which them secrete glucagon (peptide hormone)
What does the glucagon secretion result in?
Liver cells:
- -> increased breakdown of glycogen as well as increase in glucose synthesis
- -> Ketone synthesis increases
What are some other hormones then glucagon that can increase blood glucose levels?
Growth hormone, adrenaline, cortisol
What are problems with hormone receptors and levels caused by?
- Autoimmunity: destruction of receptors (or artificial stimulation of receptors)
- Genetic mutation: mutations can cause gain or loss of function
- Tumors: excess tissue usually leads to excess hormone release, but can sometimes prevent release (alpha and beta cells)
What is type 1 diabetes?
It is hyposecretion of insulin, can be caused by destruction of pancreatic beta cells by the immune system
Outcomes:
- Excess glucose in urine
- Polydipsia
- heart problems
- Disrupted blood flow
Treatment
- Insulin injections
What is type 2 diabetes?
It is hyposensitive receptor to insulin “insulin resistance”
- Insulin is produced by receptors don’t respond to it
Outcome:
Same as type 1
Treatment:
- Changes in diet and exersise
- Various medication
What is the pituitary gland?
Located at the base of the brain and is attached to the hypothalamus
- The hypothalamus controls the pituitary hormones
- Anterior and posterior lobe
What is the posterior lobe of the pituitary and how does it release hormones?
Connected to the hypothalamus by neurons
- Secretes hormones into blood
- An increase or decrease in frequency of action potentials leads to corresponding change in hormone release
- Hormones are made in the hypothalamus and stored at axon endings
What are the posterior pituitary hormones?
Antidiuretic hormone
- Stimulates the kidneys to reabsorb water (the kidneys conserve water when the body dehydrates
Oxytocin
- Stimulates the contraction of uterine muscles during childbirth (positive feedback system)
- Stimulates milk release in breastfeeding (milk ejection reflex)
What is the anterior pituitary and how does it release hormones?
- Connected to the hypothalamus by blood vessels
- Hypothalamus signals the anterior pituitary to release hormones by hormonal stimulation, secreting stored releasing hormones (or inhibiting hormones)
- Short axons release particular hormones into capillaries
- Hormones are made in the anterior pituitary by specific cells
How does feedback regulation work in the anterior pituitary?
Hormones need to be regulated well as the outcome has effects on different cells in the body.
- Last hormone has the effects in the organ. This hormone also stops both hypothalamus and anterior from producing their hormones (releasing and pituitary hormones)
What are the indirect effects of growth hormone?
Promotes the growth of bones, muscles and other tissues by casing release of Somatomedin C, which promotes cell division
What are the direct effects of growth hormone?
Muscle:
- Stimulates protein synthesis and inhibits cellular uptake of glucose
Liver
- Stimulates glucose synthesis
Fat:
- Increases triglyceride breakdown in adipose tissue (releasing glucose)
What is the growth hormone pathway?
- Hypothalamus release growth hormone releasing hormone and causes the release of growth hormone in anterior pituitary gland
- This will travel in the bloodstream to the liver and release Somatomedin C which has particular effects
- Negative feedback to hypothalamus to cause growth hormone releasing hormone to stop releasing that signal
- Positively influence the growth hormone inhibiting hormone
- This will then negatively feedback on the anterior pituitary gland and stop growth hormone from being released via somatostatin neurons rather then directly
When are GH hormones the highest?
GH concentrations have peaks and troughs throughout the whole day
- Highest concentration during sleep time (peaks at night)
What are some growth hormone associated disorders?
Excess secretion of GH (gigantism)
- Causes thickening of various tissues
Deficiency
- Not enough secretion of GH (dwarfism)
What are the hormones that are important for normal human growth?
Insulin, thyroid hormone, sex hormones, growth hormone
What are the adrenal glands?
Characteristically triangular - Outer layer cortex is yellow - Medulla is red or grey (inner layer) Made up of two different types of tissue Location: Superior to kidney
What makes up the adrenal cortex and what does it secrete?
All layers secretes steroid hormones (made from cholesterol)
- The outer layer secretes: aldosterone (sodium homeostasis)
- Middle layer secretes: cortisol
- Inner layer secretes: androgens (minor reproductive role)
What does the adrenal medulla secrete?
Secretes mainly adrenaline and noreodrenaline
How does cortisol get to receptors?
It is produced as required (from cholesterol in the adrenal cortex)
- It is carried in blood bound to carrier protein
- At target cells cortisol binds to receptors in the cytoplasm and activates gene transcription to produce the responses
What are the sequence of events that leads to cortisol secretion?
Stimulus: Stress or non stress neural inputs e.g. low blood glucose
- Stimulus causes hypothalamus to secrete corticotropin releasing hormone (CRH). Goes into the capillary bed in the hypothalamus
- Moves down and binds to particular cells within the anterior pituitary and cause them to release ACTH (adrenocorticotropic hormone). Release from AP and into bloodstream
- Act on the adrenal cortex (outer part of adrenal gland) and cause it to release cortisol
This has metabolic effects as well as other effects
What affects does cortisol secretion have short term?
Muscle:
- Increased protein breakdown
- Decreases glucose uptake within muscles
Fat:
- Fat breakdown increase
- Decrease glucose uptake
Liver:
- Increase glucose synthesis in the liver
What are the long term effects of cortisol?
- Helps one to cope with stress
- Supresses the immune system
- Essential for maintaining normal blood pressure
- Promoting anti-inflammatory actions
- Increasing blood pressure
- Activation of CNS
- Increasing heart and blood vessel tone and contraction
What is the difference between pathways for cortisol with stress and non-stress stimulus?
If stimulus is non-stress there is a negative feedback (what is expected from a anterior pituitary hormone)
In a stressful response this negative feedback overridden and the release of hormones persists until the stress stimulus is gone
When in the day is cotisol secretion the highest?
The highest peaks upon waking
- Any disturbances of normal sleep patterns e.g. jet lag, changing work shifts will affect this pathway (causes issues with immune system)
What is Addison’s disease and what are the symptoms?
Lowered secretion of both cortisol and aldosterone
- Low cortisol concentration leads to increase in ACTH (releasing hormone) secretion
- ACTH is structurally similar to a hormone that is involved in stimulating melanin production
- Excess ACTH stimulates melanin synthesis (change in skin pigmentation)
Other symptoms:
- Low blood pressure
- Weakness
What is Cushing’s syndrome?
To musch cortisol Symptoms? - Fat accumulation - High blood pressure - Weakness
What does the adrenaline and nonoradrenaline secretion do?
Increase adrenaline and noradrenaline secretion from adrenal medulla supplements the actions of the sympathetic nervous system, particularly in times of stress
“Fight or flight” response
What is the adrenaline releasing pathway?
Stimulus: Stress
- Causes the hypothalamus to send AP’s down to preganglionic fibers to act on the adrenal medulla (acetylcholine binds to receptor)
- When the signal reaches the adrenal medulla, stored adrenaline is released
- Adrenaline goes on to travel to target cells through blood
Adrenaline sits and waits to be released, so when the signal passes through it can be released quickly
- It is a water soluble hormone
- Cell membrane receptor
- Causes activation of G protein which uses a second messanger system
- Fast response
What are adrenaline’s effects?
Skeletal muscle and liver:
- Increased breakdown of glycogen to glucose
Fat:
- Increased breakdown of fat
Some systems are activated for physical activity
System not crucial for short term survival are shut down
