Endocrinology Flashcards
What are the bodies two main control systems
- Nervous system
- Endocrine system
What do the nervous system and endocrine system control and integrate how are hormones secreted?
Processes such as:
- reproduction
- growth and development i.e. puberty, growth phases
- maintenance of electrolyte, water and nutrient balance of the blood
- regulation of cellular metabolism and energy balance
- mobilisation of body defenses - links immune system
Role of endocrine glands
Secrete hormones into systemic circulation/blood
Dense vascular place - lots of capillaries - red
What are hormones also called
Chemical messengers
What is main signal within the endocrine system
Hormone
How are hormones secreted?
Around body via specialised organs called endocrine glands - travels around body in blood
How are hormones transported and where do they go to
In blood to a tissue where they have a specific action
What is a hormone
A chemical substance which is secreted by specialised endocrine cells directly into the blood to exert an effect on distant target cells
What is the target cell
Local
Only specific target cell receptors around the body are able to identify hormone and respond to it.
What are the local target cells reffered as
Paracrines - Secreting another cell in same area
Autocrines - Having effect back onto themselves
What are the 2 types which hormones are made of?
Amino acid/proteins based
Lipid based- steroid based hormones
What are the 2 types of amino acid based hormones
- Polypeptides
- Modified amino acids
Amino acid based hormones - Polypeptides
- Polypeptides - long chain
- Can not pass through plasma membrane by diffusion- have to use specialised proteins/channels within plasma membrane which bind to receptors
- Water soluble - as they are protein based
- Most common e.g TRH, TSH, GnRH, FSH, insulin, glucagon
Amino acid based hormones - Modified amino acids
- Small
- Still cannot pass though plasma membranes by diffusion because….
- water soluble
e. g thyroxine
- water soluble
What are the lipid based/steroids hormones
- Synthesised by cholesterol - one of constituents of p.membrane - sit in hydrophobic region inside p.membrane
- Small, fat soluble - can pass through the plasma membrane by diffusion- as they can pass through the hydrophobic region
e. g. cortisol, oestrogen, testosterone
What are the 3 types of stimuli to release hormone
-Humoral stimulus
-Neural stimulus
-hormonal stimulus
These stimulate hormone secretion = maintain homeostasis
What is humoral stimulus?
- Hormone release caused by altered levels of certain critical ions or nutrients
- STIMULUS: Low conc of Ca2+ in capillary blood.
- RESPONSE: Parathyroid glands secrete parathyroid hormone ( PTH), which increases blood Ca2+.
- These glands are constantly monitoring levels of ions and nutrients in systemic circulation
- Endocrine glands sense if the levels are high or low and respond by secreting a hormone
- Which will exert an effect on another gland in the body to change the uptake or excrete the ions/nutrients to regulate the level in the blood.
What is neural stimulus?
- Hormone release caused by neural input
- Stimulated by nervous system
- STIMULUS: action potential in preganaglionic sympathetic fibres to adrenal medulla
- RESPONSE- regulate secretion of adrenaline by adrenal medulla cells
- Medulla of adrenal gland - secretes adrenaline - noradrenaline - regualtes fight or flight response - responds to external stimulus - sympathetic fibres coming from one of ganglions - regulate secretions of adrenaline and noradrenalin
What is hormonal stimulus
- Hormone release caused by another hormone
- STIMULUS- hormones from hypothalamus
- endocrine glands regulated by hormones
- RESPONSE- pituitary gland secretes hormones that stimulate other endocrine glands to secrete hormones
How is hormone release regualted
Negative feedback
Example of a negative feedback - homeostasis
hormonal stimulation
- Gland A- secrete hormone A in blood stream
- Hormone A - have effect on endocrine organ - Gland B
- Gland B induced to secrete hormone B back into blood stream
- Hormone B - some used up by a target organ (where it is needed)-Low levels of hormone B in blood stream
- Detected by gland A = secrete more hormone A so more hormone B = keep levels of hormone B constant
- Again gland A stimulated- repeat process
- When hormone B levels in blood build up and too much- it inhibits secretion of hormone A from gland A = not stimulating gland B to secrete hormone B - eventually blood stream levels of Hormone B decreases
What happens if iron levels too high
Can stop secretions of hormones
What are the main endocrine glands in the body?
Pineal - sleep/wake cycle Pituitary- Growth/lactation/thyroid Thyroid- Metabolism Thymus- T-cell maturation - wbc maturation, adolescence Adrenal-stress response Pancreas-glucose metabolism Ovaries-ovulation Testis-spermatogenesis
What does pineal gland cause
Drowsiness
Lowers body temp - at night - direct link between melatonin levels in bloody and body temp
What hormone does pineal gland secrete
Melatonin
What type of stimulus is melatonin
Neural
Where is pineal gland located
Middle of brain - no access to light
What is role of melatonin in pineal gland
Regulate sleep/wake cycle through neural stimulation from eyes back to pineal gland
Neural stimulation through retina - in retina - photoreceptor cells - melatonin cells or IPRG’s - detect levels of moon light in environment - relay most photoreceptors - some of them regulate pineal gland through nervous stimulation - back into through suprachiasmaticc nucleus - sends nervous innervation back to pineal gland - regualtes secretion of hormone called melatonin
When is melatonin secreted
Overnight - when dark - as meltaonin puts body in a state where you can sleep = need high levels of melatonin to sleep
Also regulates metabolism
What does the hypothalamus do?
- Receives input from higher brain centres- limbic system= detect emotional changes
- Receive input from visceral and somatic sense via brain stem (everywhere else in body- respond to physical changes- neural stimulus from touch , temp to brain which relays info)
- The release of hormones from the pituitary is regulated by different stimuli acting on the hypothalamus initially.- interaction into your endocrine system
- sends neurones into pituitary gland
What happens if tumour in pituitary gland
If present and it starts to grow, it cant go down or sidewards, can only go up. As it grows upwards it starts to compress nerves coming from retina to eye where you see and cuts off info from eye to brain = loss of vision
Lot of tumours in brain are in pituitary gland as its in bony cup
What is optic chiasm?
- Bundles of nerves coming from back of eye through optic nerve
- Cross middle line of brain
- Sits directly above the pituitary gland
What does pituitaty gland sit in
Bony cup
Lie close to optic nerve
What is the hypothalamus?
- Part of CNS/brain
- Regulate pituitary and pineal gland- uses neuroendocrine system - main relay point between nervous system and endocrine system
- links the CNS to endocrine system
What is master regulator of hormones in body
Pituitary gland
What are 2 regions of pituitary gland
Anterior lobe - front
Posterior lobe - back
What does these 2 regions do?
Secrete different hormones
and innervated differently by hypothalamus
What is anterior lobe?
- Produce and secrete hormones from cells within the anterior lobe itself into bloodstream
- Lots of different cells types - each type secretes different hormone
What are the anterior pituitary cells?
- Somatotrophs- growth hormone - v.active during childhood
- Lactrotophs- prolactin
- Corticotrophs- ACTH
- Thyrotrophs- TSH
- Gonadotrophs- FSH and LH
What does TSH stand for
Thyroid Stimulating Hormone
Role of posterior lobe
Secretes oxytocin and vasopressin ( ADH)
Role of posterior lobe
Secretes oxytocin and vasopressin ( ADH)
Regulation of Anterior Posterior Lobe
- Neuroendocrine hormones secreted from hypothalamus into blood which is detected by pituitary gland. Neurons can secrete hormones called neuroendocrine hormones
- Relationship between neuroendocrine hormones from hypothalamus and the hormones that are then released from the anterior pituitary
What do the hormones end in?
In RH- releasing hormone = stimulate
End in I- Inhibit release- from the cells in anterior pituitary lobe
How is the neuroendocrine gland signal getting to those cells in anterior pituitary lobe?
- Hypothalamic nuclei to anterior pituitary
- Neuroendocrine signals/hormones such as TRH, Gn RH, PIF are secreted/released in the neurones in the hypothalamic nuclei- have projections into into blood stream/capillaries
- Hormones travel down portal vein- in systemic circulation into capillaries which surround all the cells in the anterior lobe
- Cells respond to stimulus- act on speciifc cells to release their speicific hormones into the blood again - i.e. TSH , PRL , LH .FSH - inhibiting/regulaating secretion in response
- Hormones then secretion into hypophyseal vein- which takes hormones everywhere in the body/blood out through the vein
Role of TRH ( thyrotropin releasing hormone )
Stimulate secretion of TSH from thyrotrophs
Role of PIF ( dopamine )
Inhibits prolactin secreted
Role of GnRH
Stimulate FSH or LH to be secreted
Role of GHRH and GIH ( somatostatin )
Regulate growth hormone production
Role of GHRH and GIH ( somatostatin )
Regulate growth hormone production
What is GnRH in females?
GnRH- is secreted from the hypothalamus in a cyclical way leading to a CYCLICAL secretion ( over a month - consistenly burst of secretions, sudden surges of release of GnRH) of LH and FSH from the pituitary, which maintains the menstrual cycle.
- LH- acts on the ovarian follicle directly and it induces ovulation
- FSH- causes development of ovarian follicle and stimulates secretion of oestradiol and progesterone
What is GnRH in males?
- Release in continously pulsating action- burst on daily basis. Less cyclical action
- Causes the release of LH and FSH from the anterior pituitary - sameas females
- LH - acts on testes to produce testosterone
- FSH- acts on the testes to maintain spermatogenesis
- continuously producing sperm and testosterone - on a slightly short cyclical cycle- less level- get bursts/show more aggression suddenly at a time.
What do both males and females continously secrete
GnRH
Different effects depending on whether male/ female i.e. X/Y chromosome
What causes a period
Maintain uterinal wall or not maintaining it = breaks down = period
What is growth hormone also called
Somatropin
What is growth hormone
- Have a direct affect on other organs around the body ( not only endocrine glands ) e.g. skeletal muscle- stimulates skeletal muscle growth and protein synthesis for muscle growth
- Liver- regulate IGF- insulin growth factor -stimulates growth further
- Bone/Chondrocytes- increases axial length- forms cartilage which increases more bone. Overproduction = more cartilage = increase bone. Outside of bones = makes fingers and palms look bulky and wide
- Adipose tissue- increase fat oxidation- to make more ATP available for growth protein synthesis- metabolism. Regulates energy availiability as growing is energy demanding
What is growth hormone
- Have a direct affect on other organs around the body ( not only endocrine glands ) e.g. skeletal muscle- stimulates skeletal muscle growth and protein synthesis for muscle growth
- Liver- regulate IGF- insulin growth factor -stimulates growth further
- Bone/Chondrocytes- increases axial length- forms cartilage which increases more bone. Overproduction = more cartilage = increase bone. Outside of bones = makes fingers and palms look bulky and wide. Accumulates in hands and feet instead of bones, elongating axially length
- Adipose tissue- increase fat oxidation- to make more ATP available for growth protein synthesis- metabolism. Regulates energy availiability as growing is energy demanding -
What is gigantism
- Overproduction of growth hormone esp in hands and feet - high levels of IGF = controls excess elongation of bones
- If overproduction of GH when adult ( finish puberty ) - no longer growing - overstimulates chondrocytes
- Causes broad toes/hands
What can excess production of growth hormone cause?
Acromegaly - giganitsm - very tall - 7.5/8 ft tall
What does throid gland secrete
Thyroid hormone into bloodstream
What is secretion of thyroid hormones stimulated by
Thyroid Stimulating Hormone ( TSH ) - secreted from anterior pituitary
What hormones involved in TSH
-TSH exerts an effect on the Thyroid gland- in reponse to this secretes thryoid hormones such as thyroxine which can be converted into T3 (Tri iodothyronine)
Example of negative feedback of hormonal control - TSH
- In hypothalamus- TRH secreted down portal vein - detected in pituitary gland
- TSH- goes down vein into systemic circulation - goes through capillaries in thyroid gland
- Thyrothrops stimulated to secrete TSH - down hypophesal vein into systemic circulation through capillaires in thryoid gland.
- induce to secrete T3 and T4 in systemic circulation- regulate metabolism
- When metabolism not needed- T3 and T4 can build up
- An excess of T4 and T3 stimulates the anterior lobe of the pituitary gland to reduce TSH secretion into the bloodstream
- This reduces T4 AND T3 production in the thyroid gland
What regulates production of TSH
T4 and T3
How is TSH secretion controlled by the hypothalamus
- Hypothalamus secretes TRH
- Excess T4/T3 in the blood will inhibit the production and secretion of TRH by the hypothalamus- so dont over stimulate metablosim- needs to be regulated - lose weight easily
- To stop secretioon of TRH from hypothalamus - no more secretion of T3 and T4 - can have inhibitory effect directly in hypothalamus
- So T3/T4 has backup plan in case pituitary gland isnt listening
What does excess of T3 and T4 cause
Stimulation of anterior lobe of pituitary gland to reduce TSH secretion into bloodstream which reduces T4 and T3 production in thyroid gland = reduces T3/T4 circulation = removing block on TSH secretion - pituitary gland secretes TSH again
Why might you want to inhibit secretion of TSH from cells in pituitary gland
Might not want metabolism e.g. during night = levels of T3/T4 build up in blood - not being metabolised and used - detected back in pituitary gland by secreting cells
What does ACTH act on
Adrenal cortex of adrenal gland
What does ACTH result in
Production of cortisol regulate in diurnal rhythm -Stress response -Increase b.p -Increase blood glucose- energy boost
How do cortisol levels change during the day
- More cortisol secreted during day after you wake up. Decreases before going to bed - feel worse at night as cortisol levels decrease.
- Immune system starts to fight it off - use more energy so feel worse at night
What does prolactin produce and inhibit
milk production /lactation and mammary growth during pregnancy
-Inhibited by dopamine - which stops secretion of prolactin until needed
Role of prolactin inhibitory factor
Inhibits secretion of prolactin
Want it to be inhibited as prolactin induces lactation - milk production in mammary glands - only want that at end of pregnancy and whilst nursing = normally secreting dopamine ( prolactin inhibitoy factor )
What is prolactin inhibitory factor secreted from
Hypothalamus
What are the hormones from Posterior Pituitary
Oxytocin
Vasopressin ( ADH )
Function of oxytocin
- Happy hormone
- orgasm - pass on genes - increase offspring
- socialisation
- giving birth- helps mother baby bonding - forget pain of giving birth
Function of vasopressin
- regulate water of blood
- increase water retention by kidneys (antidiuretic)
- Constricts arterial walls therefore increases BP
- regulated by baroreceptors in atria - senses BP
- act through humoral stimulus- osmoreceptors also increase ADH release to reserve water
- ADH - Antideuretic hormone
What type of stimuli is ADH
Humoral - sense amount of water
Properties of Posterior Pituitary
- Hypothalamus to posterior pituitary via nervous innervation
- 2 types of nuclei: supra optic and paraventricular nuclei
- Hormones stored in nuclei then secreted in blood stream via posterior pituitary into hypophyseal veins - from neurons
- Hormones secreted are oxytocin and vasopessin (ADH)
- Hormones produced in hypothalamus and travel down into neurons - secreted by these neurons directly into bloodstream, come out through veins same as anterior lobe
- These neurones coming from supra optic and paraventricular nuclei in hypothalamus- innervate down in posterior lobe
- No cells in posterior lobe which produce and secrete hormones
- Posterior lobe acts as a store
How is posterior lobe different to anterior lobe
Neruones dont stop at vascular plexus and secrete neuroendocrine signals - neurone innervate directly down into posterior lobe of pituitary gland
Where are thryoid and parathryoid glands located
In neck
Sit either side - composed of 2 different types of endocrine glands - main bulk of it is on sides - thyroid gland - 2 lobes - back - posterior - 4 little spots - parathroid glands - release parathyroid hormone
Function of thryoid and parathryoid glands
. Important for calcium homeostasis maintenance - one of them induces Ca to increase and other induces Ca to decrease
. Regulate metabolism:
- protein synthesis
- lipid and carbohydrate metabolism
Why is thyroid gland red
Endocrine glands produce hormones that they have to secrete into blood = dense vascular place - lots of capillaries - blood = red
Need capillaries to sense whats going on in blood through humoral stimulus or respond to other hormones from pituitary gland
Why do females have more diseases than men
Men have hormone testonin which is immunosupresent - doesnt respond as badly to autoimmune diseases
How many parathyroid glands are there?
4 small parathyroid gland which release parathyroid hormone
what are the two types of cells in the thyroid gland?
Thyroid follicular cells
Calcitonin cells
what is the function of thyroid follicular cells?
Produce T3 and T4 hormones - control secretion of T3 and T4
Regulate metabolism and respond to TSH
what is the function of calcitonin cells?
In follicles produce calcitonin which decreases calcium uptake in digestive system.
C cells are smaller
What happens if Ca levels too high
Decrease uptake by secreting calcitonin
What do thyroid hormones T3 and T4 require?
Iodine
What is the main hormone secreted by thyroid gland
T4 - Thyroxine
What is T4
A precursor to T3 which is more potent
T4 produced first, T4 can be modified to T3
Modified amino acid - addition of mineral iodine - important because can get iodine deficiency
What does T3 affect
. Growth - need energy/metabolism
. Metabolism increases
. Body temperature regulation - biproduct of metabolism - heat - lost energy. Increase metabolism - warm body
. Mood - amount of available energy
What happens during iodine depletion
Cant produce enough T3 and T4 - end up with hypothyroidism which is underactive throid gland - cant maintain metabolism properly
what kind of cells are present in the parathyroid gland?
Cells that secrete PTH
How are levels of PTH regulated
By free Ca in bloodstream
PTH retains Ca
what type of stimuli occurs in the parathyroid glands?
Humoral stimulus
because levels of PTH regulated by amount of free calcium in the bloodstream
what does PTH respond to?
Low Ca levels - secrete hormone to retain Ca in body to get more Ca in
How does PTH retain Calcium?
. Increases renal tube absorption of calcium in the kidney - decrease Ca loss through urine. In kidneys you get rid of xs irons in urine. One of the irons you get rid of is Ca, if you dont want to get rid of it, kidneys respond by reabsorbing more Ca - higher levels of PTH
. Regulate amount of absorption of Ca through GI tract
Where are adrenal glands located?
On top of kidney
What are 3 regions of kidney
. Capsule - surrounding outside - holds everything together
. Medulla - in the centre , which are large blood vessel
respond to neural stimulus
. Cortex - ACTH from pituitary acts here
respond to hormonal stimulus
What happens in kidney transplant
Left with 3 kidneys - 2 originally and 1 transplanted in them - due to adrenal glands - still work even if kidney failure as its seperate organ
Dont want to take kidney out as you’ll take adrenal gland out as well
What hormones does cortex release in respond to ACTH -hormones of adrenal gland
- Corticosteroids
1. mineral corticosteroids
2. glucocorticoids - Androgens
what is the function of mineral corticoids?
. retains water and maintains BP and blood volume , it does this by increasing Na+ retention by the kidney and water.- increases water and na absorption
. electrolyte balance and blood pressure
what is the function of glucocorticoids?
. increases metabolism of fats/glucose
. increases blood glucose levels through gluconeogensis
. suppresses immune system
. linked to stress
what is the function of androgens?
. precursors to testosterone
. estrogen has effect maintaining male/female characteristics
- Estrogen injections feminises characteristics BUT increasing testosterin = male characteritics
What is example of mineralcorticoids
Aldosterone
What is example of glucocorticoids
Cortisol
Which hormones does adrenal cortex produce
Hormones derived from cholestrol - steroid hormone
Regulation of hormone secretion from cortex of adrenal gland
. Corticosteroids are regulated by ACTH from the anterior pituitary gland
. ACTH secretion is regulated by CRH secretion from the hypothalamus
. Negative feedback:
- Hypothalamus secretes CRH
- CRH stimulates CRH in pituitary gland to secrete ACTH
- ACTH from vein into systemic circulatoon through capillaries in adrenal cortex and stimulates cells to secrete glucocorticoids
what is the function of the medulla?
Secretes hormones that help cope with emotional or physical stress
What are the 2 hormones in the medulla
- Adrenaline - epinephrine
- Noradrenaline - norepinephrine
How are hormones released from medulla
Sympathetic innervation
Fight or flight response - quick signal to secrete hormones - use nerual stimulation - N.S as signals along axons travel faster than endocrine system
What type of gland is pancreas
Exocrine and endocrine
How does pancreas act as an exocrine gland
Releases pancreatic enzymes into the duodenum to aid digestion
How does pancreas act as an endocrine gland
Secretes insulin and glucagon to regulate blood glucose levels
Regulate blood sugar levels in blood
What are the main hormone pancreas secretes
Insulin and glucagon - regulate blood sugar levels
What are the endocrine cells of the pancreas
Islets of Langerhans
what is the structure of islet of langerhans ?
Uniformly distributed along fenestrated capillaries with pores to allow easy transfer of hormones in/out the blood
Clusters of secretory cells
No specific cellular pattern or lamination
How are islets linked
By bridges/linkages of these cells
what are the 5 cell types that make up the islet of langerhans?
- alpha cells 30-40%
- beta cells 50%
- delta cells 10-20%
- F cells - 10-20%
- epsilon cells - 10-20%
What is the function of the function of the 5 types of cells that make up the islet of langerhans?
they secrete hormones
1. alpha cells - secrete glucagon - increase blood sugar level
2. beta cell - secrete insulin - decrease blood sugar level
3. delta cells - somatostatin and gastrin -
gastrin - regulates the exocrine function of pancreas - amount of secretion of enzymes into digestive tract
somatostatin- inhibits gastrin secretion - low rate of digestion
4. F cells - pancreatic polypeptide - regulate digestive enzyme
5. Epsilon cells - ghrelin- controls hunger
tells you when to eat - also found in high conc of people with depression - depressed - over eat - increase levels of ghrelin - overeat
Function of alpha cells in the pancreas ?
. secrete glucagon
. liver breaks down glycogen to glucose
. glucagon increase blood glucose levels
Function of beta cells in the pancreas ?
. secrete insulin
. Increase glucose uptake
. Insulin decreases blood glucose levels
What is the main metabolic effect of insulin ?
. Facilitates uptake of glucose into muscle and adipocytes
. Stimulate liver to store glucose as glycogen
. Stimulates liver to convert excess glycogen to fatty acids - increase glycogen levels - store them as fatty acids
- WITHOUT INSULIN - LESS ENERGY- CANT MAKE RESERVES - CANT UPTAKE GLUCOSE INTO MUSCLE CELLS - VASCULAR AND NEURONAL PROBLEMS - OXIDATIVE DAMAGE OF ENDOTHELIAL CELLS
What does misregulation of blood glucose levels cause
Diabetes
What is type 1 diabetes ?
An autoimmune disease that kills off the pancreatic beta cells
What happens when you have type 1 diabetes ?
- Less insulin production and secretion
. This leads to a loss of control of blood glucose levels - they increase
what is the function of insulin ?
Suppresses glucagon secretion.
what happens when there is no insulin?
Glucagon is secreted in excess which increases blood glucose levels further
Whats role of beta cells
Cells associated with diabetes
Regulation of insulin
What happens if diabetic retinography
Start to see little changes with blood vessels - endothelial cells weaken and you get microaneurysms - support cells dying of due to toxicity of sugar - create anuerums - weak points
- Causes tight junctions of blood retinal barrier to detach and open up - break - blood leaking out into neural retina - kill of neurons
