Week 7 Science and Scholarship: Endocrine system Flashcards
what is autocrine signalling
chemicals effect the same cells that secreted them
what is paracrine signalling
chemicals are secreted onto neighbouring cells
what is endocrine signalling
chemicals are released into the bloodstream (hormones) to reach target cells throughout the body
contrast endocrine vs neural signalling
-endocrine communication is slower than nervous
-endocrine effect is longer lasting than nervous
identify any 6 functions of endocrine system
fluid and electrolyte balance
love and bonding
secondary sex characteristics
lactation
reproduction
pregnancy
temperature regulation
fuel metabolism
mood and emotions
stress
blood glucose levels
appetite and fuel intake
endocrine vs exocrine glands
-endocrine secretes directly into bloodstream vs exocrine secretes into ducts for external sue
-endocrine travels throughout the body to target tissues vs exocrine is delivered to specific locations
-endocrine eg=thyroid, adrenal and pituitary vs exocrine eg= sudoriferous glands , salivary glands and pancreas
what are the two ways endocrine glands can be arranged in the body
they can either be scattered eg pancreas or endocrine cells can be organised into specialised structures called glands
identify the key endocrine glands of the body
pituitary gland
thyroid gland
adrenal gland
parathyroid gland
adrenal gland
pancreas
location and structure of pituitary gland
-located at base of brain, just below hypothalamus and connected to it via pituitary stalk
-small, pea shaped and divided into anterior (adenohypophysis) and posterior lobes (neurohypophysis)
location and structure of adrenal gland
-located on top of each kidney
-triangle shaped, has inner medulla and outer cortex
location and structure of thyroid gland
-located below larynx, anterior to trachea on each side
-butterfly shaped, has two lobes connected by isthmus
location and structure of parathyroid gland
-four tiny rice sized glands
-on posterior surface of thyroid gland
location and structure of pineal gland
-small, pinecone shaped
-located deep in the brain
location and structure of pancreas
-elongated fish shaped organ
-behind the stomach
-houses endocrine cells called the islets of langerhan
function of pancreas
regulates Blood glucose through insulin and glucagon secretion
function of pineal gland
synthesises melatonin that regulated circadian rhythms and sleep wake cycles
function of parathyroid gland
maintains phosphate and calcium levels in the blood
function of thyroid gland
regulates metabolism ,neural activity, oxygen delivery and growth via thyroid hormones
function of adrenal glands
regulates stress response (adrenaline and cortisol), metabolism and electrolyte balance
function of pituitary gland
regulates various physiological responses
what is meant by non classical endocrine glands
organs , tissues that were not originally considered endocrine glands until it was found they released hormones
list the non classical endocrine glands
adipose tissue, kidney , GI tract
how is adipose tissue a non classical endocrine gland
secretes hormones like leptin that regulate appetite and metabolism
how is the kidney a non classical endocrine gland
releases erythropoietin (stimulates RBC production)
how is the GI tract a non classical endocrine gland
releases gastrin and cholecystokinin that regulate digestion and appetite
identify 3 main types of hormones
peptides/proteins
amines
steroid
features of peptide hormones
-chains of amino acids
-once synthesised they are released via exocytosis and stored until signalling
-bind to SURFACE cell receptors
-short half life
features of steroid hormones
-all derived from cholesterol
-released by simple diffusion, not stored
-bind to intercellular receptors
-longer half life
features of amine hormones
-derived from amino acids
-bind to SURFACE proteins
-short half life
-once synthesised by specific cells they are released via exocytosis and stored in vesicles
Explain how membrane receptors and downstream pathways transduce the actions of hormones
-the forming of a receptor-ligand complex activates an amplifier enzyme resulting in the activation of second messengers
-second messengers regulate cellular activity by influencing enzymes, genes etc
Describe the key intracellular events / actions triggered by steroid hormones
-steroid hormones diffuse across PCM and bind to intracellular receptors
-the hormone receptor complex undergoes conformational changes allowing it to bind to DNA called hormone response elements (HRE’s)
-this causes activation or repression of gene transcription and alters function of steroid hormones
identify the ways hormones can be stimulated
neural
hormonal
humoral
what is hormonal stimulation
stimulation from other hormones eg tropic hormones
what is neural stimulation
stimulation by nerve fibres
what is humoral stimulation
stimulation by a certain level of substance in blood eg ions
identify how target cells regulate the level of receptors
receptor up regulation and receptor down regulation
what’s receptor up regulation
target cells produce receptors in response to a high level of stimulus
what’s receptor down regulation
target cells lose receptors in response to a low level of horomes
Provide examples of negative feedback regulation of hormone secretion
thyroid hormones and insulin/glucagon work on negative feedback loops
Provide examples of positive feedback regulation of hormone secretion
oxytocin (childbirth) and clotting hormones (increased platelets) work on positive feedback loops
List the key factors that determine hormone concentration in the plasma
rate of secretion (most important )
rate of binding (to carriers)
rate of metabolism (removal)
Define the terms: hyposecretion and hypersecretion
hyposecretion is inadequate release of hormones from endocrine glands vs hypersecretion is excessive secretion of hormones form endocrine glands
the pancreas can be divided into ___ and ___ glands
endocrine and exocrine gland
structure and function of the exocrine portion of the pancreas
consists of acinar cells that secrete some digestive enzymes into ducts
structure and function of the endocrine portion of the pancreas
made of a cluster of cells called the Islets of langerhans that produced glucagon, insulin
identify the cells of the pancreas
alpha cells
beta cells
delta cells
PP cells
function of alpha cells
produce glucagon that helps to increase BGL
function of beta cells
produce insulin that helps to decrease BGL
function of delta cells
produce somatostatin that helps to regulate the release of other hormones eg insulin and glucagon
function of PP cells
produce pancreatic polypeptide that is involved in regulation of digestion and appetite
function of insulin
reduces blood glucose levels by converting excess glucose in the bloodstream into glycogen in liver and muscle cells
function of glucagon
increases blood glucose levels by breaking down glycogen stores of liver and muscle cells
briefly outline how glucose stimulates insulin secretion
–>Glucose entry
–>oxidative metabolism
–>↑ATP
–>inhibition of KATP channels
–>depolarization
–>opening of voltage-sensitive Ca2+ channels
–>↑[Ca2+]I
–>insulin secretion
Describe how insulin secretion is regulated via the autonomic nervous system
sympathetic - inhibits the secretion of insulin in response to low plasma glucose
parasympathetic- stimulates the secretion of insulin in response to high plasma glucose
what are GLUT
glucose transporter proteins that are responsible for transporting glucose across cell membranes
how many GLUT are there
4
“GLUT-1” …. “4”
function of GLUT-1
facilitates the transport of glucose across plasma membranes of most cells
function of GLUT-2
principal transporter of glucose between the blood and liver, and reabsorption of renal glucose
function of GLUT-3
principle transporter of glucose into CNS, neurons
function of GLUT-4
transports glucose into muscle and skeletal cells
identify insulin actions in carbohydrates
-facilitates glucose uptake and utilisation (most cells)
-stimulates glycogenesis and inhibits glycogenolysis (liver and muscle)
-increase conversion of glucose into fatty acids (triglycerides) in adipose cells
-inhibits gluconeogeneis (decreasing availability of amino acids and inhibiting hepatatic enzymes)
identify insulin actions in fats
-increase fatty acid uptake in adipose tissue
-increases fatty acid synthesis from glucose in adipose tissue
-decrease lipolysis in adipose
identify insulin actions in protein
-promotes active transport of protein in muscles
-increases protein synthesis
outline the pathways for blood glucose regulation
-hyperglycaemia ,release of insulin, glycogenesis , decrease BGL,
-hypoglycaemia,release of glucagon,glycogenolysis, increase BGL
T/F optimum blood glucose level
define glycogenesis
the synthesis of glycogen from glucose for storage in liver and muscle cells
which GLUT is dependent on insulin
4
define glycogenolysis
the breakdown of glycogen into glucose to increase BGL especially during fasting or high energy demand
define gluconeogenesis
the synthesis of glucose from non carbohydrate precursors eg lactate primarily occurs in the liver and kidneys to maintain BGL during fasting or low carb intake
what causes type 1 diabetes (aetiology)
autoimmune destruction of pancreatic beta cells
what causes type 2 diabetes (aetiology)
insulin resistance and impaired insulin secretion
what are the micro and macrovascular complication of diabetes
stroke risk, HTN, atherosclerosis
what are the peripheral neuropathic complications of diabetes
impaired reflexes, incontinence, peripheral neuropathy, gastroenteropathy
function of hypothalamus as a master regulator of key peripheral endocrine organs
regulatory centre for various bodily functions eg thirst, temperature and hunger
features of type 1 diabetes
-no insulin secreted
- chronic fasted state, ketoacidosis, glucosuria, polyuria, polydipsia
- can lead to coma and death
-10%
features of type 2 diabetes
- more common in older and overweight individuals
- large genetic component
-gradual decrease in insulin effect
-90%
function of pituitary gland as a master regulator of key peripheral endocrine organs
master gland that regulates hormone secretions and other endocrine glands
location and structure of hypothalamus
-small pea sized at base of brain below thalamus and above pituitary gland
-concial shape with base that rests on floor of 3rd apex and narrower apex that projects toward pituitary stalk
describe cellular composition of anterior pituitary gland
primarily composed of glandular tissue organised into various cells :
somatotrophs, lactotrophs, corticotrophs, gonadotrophs and thyrotrophs
-vascular connection
describe cellular composition of posterior pituitary gland
nerve fibres, glial cells and neurosecretory cells
-neural connection
contrast the functions of the anterior and posterior pituitary gland
-anterior produces and releases VARIOUS hormones
-posterior stores and releases HYPOTHALAMUS hormones
identify hormones released by pituitary gland and divide them into anterior and posterior classes
Anterior: ACTH, TSH, FSH, LH ,HGH
Posterior: ADH and oxytocin
ACTH function
stimulates adrenal glands to release cortisol and other steroid hormones
TSH function
stimulates thyroid gland to store and release thyroid hormones
LH function
triggers ovulation and stimulates production of sex hormones eg testosterone (male) , progesterone and oestrogen (females)
ADH function/ vasopressin
regulates water balance by promoting water reabsorption in kidney and vasoconstriction
HGH function
regulate growth and physical development
oxytocin function
stimulates uterine contractions and breastfeeding aswell as emotions and bonding
what hormone does each (anterior) pituitary cell release and where to
thyrotrophs- TSH to thyroid gland
somatotrophs- GH to liver, tissues, bone
lactotrophs - prolactin to mammary glands
corticotrophs- ACTH to adrenal cortex
gonadotrophs- LH/FSH to testes,ovaries
identify the two broad types of hypophysiotropic hormones
releasing and inhibiting hormone
function of releasing and inhibiting hormone
releasing stimulates the release of specific anterior pituitary hormones vs inhibiting suppresses the release of specific anterior pituitary hormones
function of:
-thyrotropin releasing hormone (TRH)
-corticotropin releasing hormone (CRH)
-gonadotropin releasing hormone (GnRH)
-GHRH
-GHIH
-prolactin releasing hormone (PRH)
-prolactin inhibiting hormone (PIH/dopamine)
-thyrotropin releasing hormone (TRH) =stimulates TSH (thyrotropin) and prolactin release
-corticotropin releasing hormone (CRH)
=stimulates ACTH release (corticotropin)
-gonadotropin releasing hormone (GnRH)
=stimulates release of FSH + LH
-GHRH
=stimulates release of HGH
-GHIH
=inhibits release of HGH and TSH
-prolactin releasing hormone (PRH)
=stimulates release of Prolactin
-prolactin inhibiting hormone (PIH/dopamine)
=inhibits release of prolactin
identify the factors that influence growth
genetics
nutriton
hormones
stress
describe how genetics influence growth
inherited traits can dictate potential growth
describe how nutrition can influence growth
adequate nutrient intake is required for optimal growth
describe how hormones can influence growth
chemical messengers eg HGH influence growth
describe how stress can influence growth
environmental or physiological factors that can negatively impact growth
distinguish between foetal and post natal growth
-foetal growth occurs during prenatal period vs post natal occurs after birth
-placental hormones vs HGH mainly
Briefly outline the various metabolic actions of HGH
-protein synthesis = increase protein production (cells)
-protein degradation=inhibit protein destruction (tissues)
-lipolysis= increase breakdown of fats into FA’s
-hepatic gluconeogenesis = raises glucose production in liver
-insulin sensitivity = decrease muscle cells responsiveness to insulin
-utilisation of FFA’s = encourages muscle cell to use free fatty acids as energy source
identify stimuli that can be a positive or negative factor in HGH release
-exercise
-stress
-hypooglycaemia
-fasting (low IGF-1)
-circadian rhythms
-high AA
-low FA’s
how does stress impact HGH release
stimulates HGH release as part of body response to stressors
how does exercise impact HGH release
stimulates HGH release especially during vigorous physical activity
how does fasting impact HGH release
leads to HGH release due to low levels of insulin like growth factor-1
how do high AA levels impact HGH release
elevate HGH release, especially after supplements or high protein meal
how do low FA levels impact HGH release
stimulates HGH secretion
how do circadian rhythms impact HGH release
HGH secretion peaks during sleep stages according to body clock
how does hypoglycaemia impact HGH release
low BGL stimulates HGH release to increase glucose production
distinguish between IGF-1 and IGF-2
IGF-1 = mainly made in liver and stimulates cell growth and proliferation in various tissues
IGF-2 = primarily involved in foetal development and growth
what signal transduction and receptor type does HGH function on
JAK/STAT
surface cell membrane receptors
name some HGH disorders
gigantism
acromegaly
dwarfism
what’s gigantism
excess growth and stature due to overproduction of HGH before epiphyseal plate closure
what’s acromegaly
progressive enlargement of extremities and tissues due to excess HGH secretion after epiphyseal plate closure
what’s dwarfism
condition causing extremely small stature and development delays
identify the main gonadotropins
LH and FSH
FSH function
stimulates growth and development of sperm and ovarian follicles (men and women respectively)
outline how the gonadotropins are regulated
1.LH stimulates thecal cells in ovarian follicle
2. thecal cells convert cholesterol into androgen
3. androgen diffuses across thecal cells into adjacent granulosa cells
4.FSH stimulates granulosa cells of ovarian follicle
5.granulosa cells converts androgen into oestrogen
6a.some is secreted into blood –> systemic effects
6b.some is remains in follicle –> antral formation
7.local oestrogen along with FSH stimulates proliferation of granulosa cells
identify the three hormones released by the thyroid gland
T3
T4
calcitonin
T3 function
triiodothyronine controls metabolism, growth and development
T4 function
thyroxine regulates metabolism and energy balance
calcitonin function
regulates Ca levels in blood and bone metabolism
what two hormones regulate thyroid gland function
TRH thyrotropin releasing hormone
TSH thyroid stimulating hormone
TRH function
(released by hypothalamus)
stimulates the release of TSH from the pituitary gland
TSH function
stimulates thyroid gland to produce and secrete T3 and T4
provide a few examples of thyroid diseases
hashimotos disease
graves disease
immunogenic thyrotoxicosis
whats hashimotos disease
autoimmune disease that results in hypothyroidism due to inflammation and destruction of the thyroid gland
whats graves disease
autoimmune disease that results in hyperthyroidism due to production of antibodies that stimulate thyroid gland
whats immunogenic thyrotoxicosis
hyperthyroidism resulting from over stimulation of thyroid by antibodies, often associated with autoimmune diseases eg graves
describe how thyroid disorder symptoms are classified
hyperthyroidism = tachycardia, tachypnoea, nervousness
hypothyroidism = bradycardia, weight gain, fatigue
what factors regulate Ca levels in blood
PTH
calcitonin
vitamin D
calcitriol
how does PTH regulate Ca levels
stimulates calcium release from bones and enhances calcium reabsorption from kidneys
how does calcitonin regulate Ca levels
inhibits osteoclast activity and promotes Ca deposition in bones to lower Ca levels
how does calcitriol regulate Ca levels
active form of Vitamin D, enhances Ca absorption from the intestines and regulates calcium metabolism for bone health and blood calcium balance
how does vitamin D regulate Ca levels
facilitates intestinal absorption of Ca and P promoting bone mineralisation
briefly outline how PTH secretion is regulated
it is regulated mainly by the calcium concentration of blood
-in turn the bones (resorption) , kidneys (resorption of P(-) or CA(+) and urinary cAMP(+)) and intestines (absorption) respond
whats hypercalaemia
elevated Ca levels in blood
–> weakness, fatigue, bone pain and kidney stones
whats hypocalaemia
lowered levels of Ca in blood
–> muscle spasm, tetany and seizures
what are the three layers of the adrenal cortex
zona reticularis (inner)
zona fasciculata (middle)
zona glomerulosa (outer)
what hormone class does the adrenal medulla secrete
catecholamines
what hormone class does the zona fasciculata secrete
glucocorticoids eg cortisol
what hormone class does the zona reticularis secrete
androgens eg sex hormones
what hormone class does the zona glomerulosa secrete
mineralocorticoids eg aldosterone
what stimulates zona fasciculata
ACTH
what stimulates zona reticularis
ACTH
what stimulates zona glomerulosa
angiotensin II
Plasma K+
what stimulates adrenal medulla
Sympathetic NS
function of zona fasciculata
resist stress
metabolism
function of zona retiuclaris
male sex hormone
function of adrenal medulla
resist stress
function of zona glomerulosa
electrolyte balance and BP
Outline, in brief, how hormone secretion from the adrenal gland is regulated
-regulated by the hypothalamic-adrenal-pituitary axis (HPA)
-when stressed hypothalamus releases CRH that stimulates anterior pituitary gland to secrete ACTH
-ACTH acts on zona fasciculata which causes release of glucocorticoids, mainly cortisol
-cortisol supports actions of catecholamines in stress response
identify the adrenal gland hormones
cortisol
androgens
aldosterone
noradrenaline
adrenaline
function of cortisol
regulates metabolism, immune function and stress response
function of androgens
secondary sex characteristics and libido
function of aldosterone
controls electrolyte balance and BP by promoting sodium reabsorption and potassium secretion as part of the RAAS in kidneys
function of adrenaline and noradrenaline
mediates body fight or filght response by increasing heart rate, BP and energy mobilisation
briefly outline how cortisol effects various body parts
cardiovascular-increase BP and HR
brain-cognition, mood, stress response
Immune-supresses immune function
metabolic-regulates glucose metabolism and promotes gluconeogenesis
bone-inhibits bone formation and promotes bone resorption
name disorder of adrenal gland
phaeochromocytoma (secondary HTN)
conn’s syndrome
cushing’s syndrome
Addisons disease
congenital adrenal hyperplasia
describe phaeochromocytoma
adrenal tumour causing excess secretion of catecholamines
describe congenital adrenal hyperplasia
genetic disorder causing adrenal steroid enzyme difficulties
describe conns syndrome
primary aldosteronism causing excess aldosterone release
describe Cushing’s syndrome
hypercortisolism resulting form various causes
describe Addisons disease
adrenal insufficiency due to autoimmune destruction or other causes
outline the flow chart of anterior pituitary gland action for stress
increase CRH
increase ACTH
increase cortisol
increased BGL
outline flow chart for adrenal medulla action for stress
increase adrenaline
Pancreas: increase glucagon t/f increase BGL and FA’s
Smooth muscle vasoconstriction and kidney:
increase renin, increase angiotensin II and increase aldosterone
outline flow chart for posterior pituitary gland action for stress
increase vasopressin
increase water retention and increase BP
what are some secondary causes of increased insulin
-high AA’s
-low FA’s
-GI enzymes
-Parasympathetic system
what are some secondary causes of increased glucagon
-low AA’s
-high FA’s
-GI enzymes
-sympathetic system
how does weight loss occur for type 1 diabetes patients
-increased concentration of glucose (can’t regulate BGL)
-less glycogen stores
-adipose tissue broken down/ more glucosuria and polyuria
-weight loss
