Endocrine L1: Introduction of Endocrine System Flashcards
What are the 2 control systems that are needed to maintain homeostasis?
- milliseconds – minutes = nervous system
- minutes – hours – days – years – entire lifetime = endocrine system
How does the nervous system connect to the rest of the system?
Fast response: milliseconds – minutes
Use nerves to connect to all the systems (need to be specific)
How does the endocrine system connect to the rest of the system?
minutes – hours – days – years – entire lifetime
Uses blood to connect all the systems
What is the neuroendocrine system?
Endocrine and nervous system work together
What are 6 functions of the endocrine system?
- regulate metabolism, water and electrolyte balance
- allow body to cope with stress
- regulate growth
- control reproduction
- regulate circulation and red blood cell production
- control digestion & absorption of food
What are the 2 blood-borne chemical messengers?
- Hormones
- Neurohormones
Hormones and neurohormones are _______ chemical messengers.
blood-borne
What does blood-borne mean?
Spread around through blood
What is the difference between the hormones and the neurohormones?
- Hormone- produced by a endocrine cell
- Neurohormone- produced by a nerve cells
What is a hormone produced by?
produced by a endocrine cell
What is a neurohormone produced by?
Produced by a nerve cell
What makes hormones work?
Target cells which have receptors respond to the hormones
What are 3 examples of hormones?
- Estrogen- for males and female
- Helps with bone mineral density
- Adrenaline
- Neurohormone and a neurotransmitter
- Important for controlling stress and CV
- Testosterone
- Steroid hormone (usually all reproduction hormones)
- Made from cholesterol (fat)
- Produced in the testes
- Target organ - testes
- Main role- sperm production
- How is it regulated? (which organ)- brain (centrally)
What type of hormone is testosterone?
Steroid hormone
What is testosterone made of?
Cholesterol (fat)
Where is testosterone produce by?
Testes
What is the target organ of testosterone?
Testes
What is the main role of testosterone?
Sperm production
How is testosterone regulated?
Brain (centrally)
What is the endocrine system?
all hormone-secreting tissues; including, in the brain, the hypothalamus, pituitary & pineal gland, and in the periphery the thyroid, parathyroid & adrenal glands, gonads, pancreas, kidneys, liver, thymus, and also parts of the intestines, the heart and skin.
What is the function of pituitary gland?
3rd eye
- Produce melatonin
What are the 3 classes of hormones (have different characteristics = different function)?
- Peptides
- Amines
- Steroids
What are the chemical classification of hormones?
What are peptides hormones?
- chains of amino acids,
- Hydrophilic (ie water soluble).
- Stored prior to release.
eg ADH, growth hormone.
What does hydrophilic mean?
Likes water = able to be dissolved
Not like fat = can’t dissolve
What are amines hormones?
- derived from the amino acid ‘tyrosine’.
- All are stored.
- Hydrophilic - catecholamines (adrenaline, noradrenaline & dopamine);
- Lipophilic (ie fat soluble): thyroid hormones.
What are the 2 types of amines hormones?
- Hydrophilic
- Lipohilic
How does tyrosine get into the body?
derived from the amino acid ‘tyrosine’. All are stored. Hydrophilic - catecholamines (adrenaline, noradrenaline & dopamine); or Lipophilic (ie fat soluble): thyroid hormones.
What are steroid hormones?
- derived from cholesterol where appropriate enzymes for conversion are present
- Lipophilic.
- Not stored
- released by diffusion.
eg cortisol, testosterone, oestrogens.
What are 4 characteristics of hydrophilic hormones?
- Most transported in blood dissolved in plasma (some also carried on binding proteins).
- Can’t pass through cell membrane, therefore binds to specific receptors on surface of target cell.
- Must work on the outside of the cell
- Elicit response either by changing cell permeability (few) or by activating ‘second-messenger’ system to alter activity of intracellular proteins (most).
- Vulnerable to metabolic inactivation so short-term effects
What are 2 types of hydrophilic hormones?
- peptides
- catecholamines
Hydrophilic hormones are mostly transported in _____ dissolved in plasma (some also carried on binding proteins).
blood
Can hydrophilic hormones pass through cell membrane? How do they work?
No
Can’t pass through cell membrane, therefore binds to specific receptors on surface of target cell.
Must work on the outside of the cell
What are 2 ways the hydrophilic hormones elicit a response?
- changing cell permeability (few)
- by activating ‘second-messenger’ system to alter activity of intracellular proteins (most).
Hydrophilic hormones ____ are/aren’t vulnerable to metabolic inactivation so there are ____ (long/short) term effects.
are; short
How can changing cell permeability elicit a response in hydrophilic?
Eg. open channels (eg. insulin = makes cell more permeable to glucose)
How can activating second-messenger systems elicit a response in hydrophilic?
Starts cascade effect
- Even working from the outside
- Something happens on the inside
What are 5 characteristics of lipophilic hormones?
- Transported in blood mostly bound to plasma proteins. Small, unbound amount dissolved – only dissolved portion physiologically active.
- Free hormone (unbound) easily passes through cell membrane, binds to specific receptor within target cell (mostly in cell nucleus). Can work directly on DNA
- Elicit response by activating specific genes within target cell to cause formation of new intracellular proteins.
- Less vulnerable to metabolic inactivation so effects last longer Very safe = can last longer = longer half lifes
- Long term effects (eg. reproductive)
What does the process of activating specific genes within the nucleus look like?
ADD
What are the 3 summary points for hydrophilic hormones?
– Likes water – Can’t get through plasma membrane – Fast onset, short-acting
What are the 3 summary points for hydrophilic hormones?
– Hates water – Can diffuse across plasma membrane – Slower onset, longeracting
What are 5 ways that the regulation of hormones can occur?
• Secretion – stimulation, feedback (Back to organ that produces it), reflexes, rhythms (Some hormones are produced at different times of the day (Eg. Night/produced in darkness - melatonin)) • Transport – binding proteins, free/bound balance (Change amount of binding proteins = changes balance between free/bound) • Metabolism – activation/inactivation, differs for hydrophilic vs lipophilic due to accessibility • Excretion – unregulated (but can be affected by renal/urinary disease) • Target cell responsiveness – receptor expression, amplification, – combination with other hormones - ‘permissiveness, synergism and antagonism’
How does regulation of hormone activity effect how a pregnancy test work?
• Measure of hormone only produced by the placenta (beta ACG) Only produced during pregnancy
What are 2 control pathways for secretion (regulation of hormone activity)?
Central regulation • controlled by the brain • affected by negative-feedback loops, neuroendocrine reflexes, rhythms (eg diurnal) • Can be fast, slow or long term responses Direct regulation • endocrine cells respond directly to changes in extracellular fluid (especially plasma) levels of substances (eg glucose, calcium) • very rapid response to critical needs
What are 5 characteristics of central regulation of hormone activity for secretion?
• controlled by the brain • affected by negative-feedback loops, neuroendocrine reflexes, rhythms (eg diurnal) • Can be fast, slow or long term responses (Usually slower and long term)
What are 3 characteristics of direct regulation of hormone activity for secretion?
• endocrine cells respond directly to changes in extracellular fluid (especially plasma) levels of substances (eg glucose, calcium) • very rapid response to critical needs (eg. glucose, calcium, parathyroid) Must stay within normal range, otherwise could die
What are 2 central regulation features
Coordinated by the hypothalamus & pituitary gland Influenced by feedback ‘loops’ (+ or -)
What does central regulation- neuroendocrine reflexes look like?
Milk let down reflex (milk ejection reflex)
What does central regulation- rhythms look like?
(eg diurnal – cortisol, melatonin, etc)
What does cortisol do?
Stress hormone • More alert • Wakes you up in the morning
What does melatonin do?
Control sleep
Why do nightmares wake you up?
Stress hormone (cortisol) produces –> wake up
Why is it ideal to sleep in a dark room? Why should you not turn the lights on when you go to the bathroom during the night?
• Melatonin is produced at night in the darkness Melatonin controls sleep and helps you sleep better
What occurs in direct regulation? What is an example?
Cells respond directly to changes in extracellular fluid levels
What are 3 characteristics of transport in regulation or hormone activity?
(for lipophilic hormones) Availability of binding proteins, some specific for particular hormone, some (eg albumin) are non-specific. Carrier-bound hormone in equilibrium with free hormone Binding proteins are synthesised in liver, deficiency (eg from liver disease) alters balance between bound and free hormone in plasma Eg. sclerosis of the liver = some disruption in hormones (eg. testosterone in males –> heighted response as less binding proteins)
What are 3 characteristics of metabolism in regulation or hormone activity?
A few hormones activated when metabolised by enzyme (eg thyroid hormone), metabolised form may have much greater activity than original. Inactivation (mostly in liver) usually unregulated, but may be affected by liver disease. Metabolism takes place at a higher rate for hydrophilic hormones (peptides & catecholamines) than lipophilic (bound) hormones as they are accessible to blood & tissue enzymes.
Why are hydrophilic hormones more vulnerable?
More vulnerable as they are floating around in the blood –> can be broken down more easily
What is a characteristic of excretion in in regulation or hormone activity?
usually unregulated, urinary excretion (so urinary levels are a good way to measure hormones), but may be affected by kidney or urinary disease.
What are 3 characteristics of targeting cell responsiveness when regulating hormone activity?
Amplification of hormones effects via second messenger cascade • Variations in receptor expression on target cell - a cell must have functional receptors specific for the hormone to be able to respond. – Number and type of cell receptors can vary by downregulation or up-regulation • Permissiveness, Synergism & Antagonism – Presence or absence of one hormone can influence effects of another through receptor regulation, activation or inactivation
How does amplification work in the regulation of hormone acivity?
There are tiny amounts of hormone in blood Thus, the chance of the target cell getting some hormone is very low When it does –> wants to respond –> amplifies the signal even though hormones in low plasma concentrations (pg/ml), effects amplified within cell
What is permissiveness?
• Need hormone A for hormone B to work • Dependent Usually through upregulation
What is synergism?
• When hormone A is present, hormone B will work better (more effective) Eg. estrogen and progesterone
What is antagonism?
• The presence of hormone A means that hormone B doesn’t work Eg. insulin and glucagon
What are the 3 classes of hormones? SUMMARY
peptides, amines, steroids
What are 2 types of hydrophilic hormones?
peptides & catecholamines
What are 5 summary characteristics of hydrophilic hormones?
Hydrophilic (peptides & catecholamines): dissolve in blood, can’t pass through membranes (act on surface receptors), stored, fast acting, fast breakdown
What are 2 types of lipophilic hormones?
TH steroids
What are 4 summary characteristics of lipophilic hormones?
dissolve in fat, can diffuse through membranes (act within cell), hard to store, longer to act, slow to breakdown
Why do lipophilic hormones take longer to act?
because they are hard to store (dissolves easily) need to make them when need them
What are 4 ways to regulate hormone activity?
secretion, transport, metabolism, responsiveness of target cells
What are the 2 most important structures for controlling endocrinology?
- Hypothalamus
- Pituitary gland
What is the role of the hypothalamus?
Coo-ordinates and integrates information from the internal and external environment and translates it into a signal that can be used
Where is the hypothalamus?
In the base part (primitive) of the brain
What is the hypothalamus?
- Large clumps of cells = nuclei
- Different clumps do different functions
What are the 2 sections of the pituitary gland?
- Anterior
- Posterior
What is the anterior pituitary gland?
- Arises from the roof of mouth
- Not nervous/brain tissue
What is the posterior pituitary gland?
Part of the brain (formed in the embryo) = nerve endings of nerve cells that are in the hypothalamus
What happens when something goes wrong with the pituitary gland? Eg. what happens to people who havepituitary tumours?
the pituitary gland tends to push up on the bottom of the brain (optic chiasm- where optic nerves cross over) as it is tucked away
Eg. people with pituitary tumours first present with visual defects
Endocrine tissue is very _____. What does that mean?
reactive
- Prone into turning into tumours
- Can turn into benign metastases
- Why is that a problem if they are not malignant?
- Push up and create pressure
- Why is that a problem if they are not malignant?
What does it look like between the hypothalamus and the posterior pituitary gland?
What does it look like between the hypothalamus and the anterior pituitary gland?
What is anterior pituitary gland tissue?
Tissue that arises from the roof of the mouth
No nerve connections to the brain
What are 7 major hypophysiotrophic hormones?
What are the 6 hormone of the anterior pituitary?
- Thyroid stimulating hormone (TSH)
- Adrenocorticotrophic hormone (ACTH)
- Produces cortisol (stress)
- Growth hormone
- Prolactin
- Helps to produce milk
- Luteinising hormone (LH)
- Follicle-stimulating hormone (FSH)
- Work on gonads (ovaries or testes) to help produce for sex hormones and support the development of eggs or sperm
What are the 2 groups of anterior pituitary hormones?
- ‘Trophic’ hormones control activity another endocrine gland
- ACTH TSH LH & FSH ACTH, TSH, LH & FSH
- Hormones which have a direct effect in their own right
- Prolactin & growth hormone (Both direct effect and affects another endocrine hormone)
What happens to hormone secretion when pituitary stalk is sectioned? (i.e hypothalamo-pituitary disconnection?
It is possible to be broken (during trauma/accident)
What is “stalk section” hypothalamo-pituitary disconnection in FSH and LH, GH, TSH, ACTH, Prolactin?
Why does prolactin increase unlike the others?
- In normal circumstances –> don’t produce a lot of the other hormones (usually stimulate), but prolactin is always producing it and usually inhibit it (eg. dopamine) to keep it under control
- Stops becoming inhibited
- Becomes a risk for infertility in both genders
