Introduction to Endocrine and Exocrine Glands Flashcards
Define hormone
A regulatory substance, usually steroid or peptide, produced in an organ or specialised group of cells, transported in tissue fluids (blood), stimulate specific cells or tissues into action
define neurotransmitter
a chemical substance released at the end of a nerve fibre by the arrival of a nerve impulse, diffuses across the synapse, effects the transfer of the impulse to another nerve fibre, a muscle fibre, a gland cell or some other structure.
define receptor
Target cell for hormone / neurotransmitter
define ligand
Natural chemical which triggers the receptor
define agonist
Binds to the receptor and triggers a response
Can be a natural ligand or a drug
define antagonist
Binds to the same receptor and dampens/blocks a response
Usually a drug
two types of hormones
water soluble
lipid soluble
water soluble hormones include…
Include amine-containing hormones.
Adrenaline
Noradrenaline
lipi dsoluble hormones include…
Include the steroid containing hormones.
Cortisol
Aldosterone
Androgens
Oestrogens and progestogens
Water soluble hormones have their receptors
outside
Water soluble hormones cannot
diffuse across the lipid cell membranes
The binding of …
the hormone to the receptor activates enzymes inside the cell that regulate the biochemical activity of the cell..
cellular processes are modulated (regulated by…
…. instructions the cell receives by the attachment of the hormone to the receptor withoutthe hormone molecule actually entering the cell.
fat soluble hormones are…
lipophilic - they dissolve in fats
what are fat soluble hormones usually formed from?
cholesterol (an important component of cell membranes) so are also referred to as steroid hormones.
Lipid soluble hormones have their receptors
inside their target cells
Because the hormones are lipid soluble, they can…
diffuse across cell membranes
the hormone moleccules passes through the..
cell membrane and binds to a receptor to form a hormone receptor complex
The hormone molecule passes through the cell membrane and binds t
a receptor to form a hormone-receptor complex.
The hormone-receptor complex moves to
the nucleus of the cell and binds to a region of DNA.
The binding of the complex to the cell’s DNA alters
gene expression and causes genes to switch ‘on’ or ‘off’ the activity of enzymes that regulate the activity of the cell.
what is a gland?
A gland is one or more cells that make and secrete a particular product.
where are glands located?
Glands are located throughout various parts of the human body.
Usually glandular secretions contain…
… proteins
Usually glandular secretions contain proteins, but some glands produce…
… lipid or steroid rich secretions (e.g. hormones, enzymes).
An endocrine gland makes…
… hormones that are released directly into the bloodand travel to tissues and organs all over the body.
Also known as ductless glands.
An exocrine gland makes …
… substances such as sweat, tears, saliva, milk, and digestive juices that it releases into a duct or opening to a body surface.
what are unicellulr glands composed off
Composed of a single cell, scattered within epithelial sheets.
what is an example of unicellular glands?
An example of this is goblet cells.
describe goblet cells
Modified simple columnar epithelial cell.
Secrete mucin
Form mucus in H20
Microvilli on surface
Found in intestines, respiratory tract, and conjunctiva of the eye.
what are multicellular glands composed of?
Composed of several cells.
how are multicellular glands formed?
Form by invagination (pocket) from an epithelial sheet.
what do most multicellular glands have?
Most have ducts to connect them to the epithelial sheet.
multicellular glands can be
simple or compound
the three types of multicellular glands?
Tubular, Alveolar, or tubuloalveolar.
exocrine doesnt have to…
leave the body, it refers to a secretion passing through a duct.
the exocrine glands release their secretions into an
external environment - lumen, cavity, skin.
the endocrine system release their secretions …
internally
In the blood = endocrine
In between cells = paracrine
the endocrine system produces hormones secreted by…
exocytosis directly into the extracellular space where they inter the blood/lymph and travel to their specific target organs.
Two systems control all physiological processes
nervous system
endocrine system
describe nervous system
exerts point-to-point control through nerves.
Electrical in nature.
Fast.
describe endocrine system
- Broadcasts hormonal changes to essentially all cells by secretion into blood and extracellular fluid.
- Target cells must bear a receptor for the hormone being broadcast in order to respond
Mature endocrine glands eventually …
… lose their ducts, often called ductless glands
endocrine glands produce hormones by
exocytosis directly into the extracellular fluid.
They produce hormones by exocytosis directly into the extracellular fluid,
This eventually …
… enters the blood, surrounding tissue or lymphatic system, and travels to specific organ targets
Most endocrine glands are
compact multi-cellular organs.
Some unicellular hormone-producing cells are
scattered in the digestive tract mucosa – diffuse endocrine system.
secretions of endocrine glands
Modified amino acids
Peptides
Steroids
Glycoproteins
the endocrine system releases hrmones into
interstitial fluid (local acton) and into circulation (target distant cells in the body)
the endocrine system regulates
homeostasis
What are the functions of the endocrine system?
- Regulates metabolism, H2O and electrolyte balance – homeostasis.
- Inducing adaptive changes to help the body cope with stressful situation.
- Promoting smooth sequential growth and development.
- Controlling reproduction.
- Regulating red blood cell production.
- Controlling and integrating activities of both the circulatory and digestive systems (along with the autonomic nervous system).
what are the central endocrine glands
Hypothalamus
Pineal gland
Pituitary gland
where is the hypothalamus located?
Located just below the thalamus of the brain (hypo means ‘under’ or ‘below’ in Greek).
the hypothalamus is the major link between
the nervous and endocrine systems.
The hypothalamus is linked to
the pituitary gland by the infundibulum and releases hormones to control the pituitary.
Hormones in the hypothalamus are made by
special neurosecretory cells.
hormones in the hypothalamus are packaged into
vesicles which are released and diffuse into primary plexus of the hypophyseal portal system
The hypothalamus produces a variety of
releasing and inhibiting hormones to control the Anterior Pituitary.
The hypothalamus produces a variety of releasing and inhibiting hormones to control the Anterior Pituitary.
These cause
… the anterior pituitary to start or stop secreting hormones.
the different releasing homrones
CRH – Corticotropin releasing hormone
GHRH – growth hormone releasing hormone (Somatocrinin)
GnRH – Gonadotrophin Releasing Hormone)
PRH – Prolactin Releasing Hormone (*though to exist)
TRH – Thyrotrophin Releasing Hormone
the different inhibiting hormones
GHIH – Growth Hormone Inhibiting Hormone (Somatostatin)
Dopamine – Prolactin Inhibiting Hormone.
hormones from the hypothalamus pass through the
the hypophyseal portal system to the anterior pituitary
The hypothalamus produces a variety of …
… releasing and inhibiting hormones to control the Anterior Pituitary.
- These cause the anterior pituitary to start or stop secreting hormones.
what are the releasing hormones produced in the hypothalamus ?
CRH – Corticotropin releasing hormone
GHRH – growth hormone releasing hormone (Somatocrinin)
GnRH – Gonadotrophin Releasing Hormone)
PRH – Prolactin Releasing Hormone (*though to exist)
TRH – Thyrotrophin Releasing Hormone
what are the inhibiting hormones produced in the hypothalamus?
GHIH – Growth Hormone Inhibiting Hormone (Somatostatin)
Dopamine – Prolactin Inhibiting Hormone.
the releasing and inhibting hormones pass through…
… the hypophyseal portal system to the anterior pituitary
the posterior pituitry does not synthesise…
… hormones
what does the posterior pituitry store and secretes?
Stores and secretes two hormones made by the hypothalamus.
the posterior pituitry stores and secretes two hormoines produced by the hypothalamus.
What are these?
- Vasopressin (Antidiuretic Hormone – ADH) - involved in the urinary system. Water balance/blood vessel constriction.
- Oxytocin (muscle contraction) – involved in birth and lactation.
the pituitry gland is split into…
… two parts: anterior and posterior
the anterior pituitry regulates what?
Regulates many physiological processes: stress, growth, reproduction, and lactation
what does the anterior pituitry gland synthesise and secrete?
- Synthesises and secretes a wide range of hormones from basophil cells.
- Synthesises releasing hormones.
the anterior pituitry contains…
… five different trophic cell* types (1-5)
the anterior pituitry secretes…
… seven different hormone types (I-VII).
what are the functions of trophic cells?
A trophic cell releases hormones that have other endocrine glands as their target.
what do somatotrophs secrete?
Secrete human Growth Hormone (hGH)
somatotrophs causes …
… hepatocytes to produce Insulin-like Growth Factors (IGFs)
- IGF-1
- IGF-2
function of igf-1
(cell proliferation) – Regulates normal cell physiology/cancer (adults).
function of igf-2
(cell proliferation) – foetal development.
what do thyrotropbhs secrete?
Thyroid Stimulating Hormone (TSH)
what does Secrete Thyroid Stimulating Hormone (TSH) control?
Controls the Thyroid Gland.
what does Thyroid Stimulating Hormone (TSH) stimulate?
Stimulates T3 (triiodothyronine) and T4 (thyroxine) secretion.
what does Thyroid Stimulating Hormone (TSH) increase ?
Increase basal metabolic rate (BMR) / protein synthesis in cells of the body.
what do gonadotrophs secrete?
Secrete Follicle Stimulating Hormone (FSH)
Secrete Luteinising Hormone (LH)
what do Secrete Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH) secrete
Control oogenesis/ovulation and spermatogenesis
what does FSH trigger
FSH triggers development of the ovarian follicles/spermatocyte development
what does LH trigger
LH triggers ovulation in females and the development of the corpus luteum
what does LH stimulate
LH stimulates Leydig Cells to testosterone in males
what do lactotrophs secrete?
Secrete Prolactin
Along with oxytocin controls lactation
what do corticotrophs secrete?
Secrete Adrenocorticotrophic Hormone (ACTH)
Secrete Melanocyte Stimulating Hormone (MSH)
ACTH controls the release of
corticosteroids by the adrenal glands
MSH melanin production in …
… brain (appetite control) as well as skin and hair (UV ray protection, pigmentation).
function of melatonin
entrains body’s biological rhythms with external cues, inhibits gonadotropins, antioxidant, enhances immunity
melatonin is a derivative of…
… 5-HT (serotonin)
what does melatonin modulate?
Modulates sleep/wake cycles
The retina plays a large role in
circadian rhythms, relying on external stimuli
what regulates most circadian rythms in the body?
The Suprachiasmatic nucleus in the hypothalamus regulates most circadian rhythms in the body.
External stimuli interact with
the retina
Signals are then passed to the
SCN
The SCN is connected to
the Pineal Gland via the superior cervical ganglion (SCG)
The pineal gland regulates …
its release of melatonin in response to the stimuli
The pineal gland regulates its release of melatonin in response to the stimuli…
Increasing production and secretion of melatonin in response to darkness
Decreases production of melatonin in response to light
what is the main cell inthe pineal glands?
Pinealocytes are the main cell in the pineal gland, their primary function is the secretion of melatonin.
the pineal gland synthesises the
hormone melatonin
melatonin is released into the
systemic cirfculatory system by the pineal gland
the pineal gland produces…
the hormone melatonin
meltatonin is released by
pinealocytes
the pinneal gland in under the control of
sunlight
the pineal gland generates
rythms (via suprachiasmatic nucleus)
Produces the hormone melatonin
Released by pinealocytes
Under control of sunlight
Generates rhythms (via suprachiasmatic nucleus)
This is why there are consequences …
Shift work
Jet lag
Bright light during the night/using the phone before bed
the peripheral endocrine system
Parathyroid glands
Thyroid gland
Thymus
Adrenal glands
Pancreas
Kidneys
Testes
Ovaries
cotrisol and androgen production regulation process?
1) Hypothalamus secretes Corticotropin Releasing Hormone (CRH)
2) This travels to the pituitary.
3) The pituitary secretes Adrenocorticotrophic Hormone (ACTH).
4) This regulates cortisol and androgen production.
what do parathyroid glands secretre?
Secretes Parathyroid hormone (PTH)
affects of Secretes Parathyroid hormone (PTH)
Increases plasma Ca2+ concentration
Decreases plasma PO43- (phosphate) concentration
Stimulates Vitamin D activation.
what does the htyroid gland secrete?
Secretes T3 and T4
affects of T3 and T4 ?
increases metabolic rate, essential for normal growth and development.
what does the adrenal cortex secrete?
1) Adrenal cortex: Aldosterone and cortisol
2) Adrenal medulla secretes adrenaline and noradrenaline
what are the two adrenal glands?
adrenal cortex
adrenal medulla
what is the function of Adrenal cortex: Aldosterone and cortisol ?
Increases Na+ reabsorption and K+ secretion
what is the function of Adrenal medulla secretes adrenaline and noradrenaline?
- Reinforces sympathetic nervous system
- Contributes to stress adaptation and blood pressure regulation
what does the pancreas produce?
- Insulin (beta cells)
- Glucagon (alpha cells)
- Somatostatin (delta cells)
The pancreas has both
endocrine and exocrine functions.
The endocrine cells within the pancreas are:
Alpha cells
Beta cells
Delta cells
Epsilon cells
Upsilon (PP) cells
insulin (beta cells) function
control of nutrient uptake into cells
glucagon (alpha cells) function
maintains nutrient levels in blood plasma during post-absorptive state.
Somatostatin (delta cells) funcrtion ?
suppresses the release of gastrointestinal hormones – inhibits digestion and absorption of nutrients
Ghrelin (epsilon cells) function?
stimulates appetite, regulates energy homeostasis, and carbohydrate metabolism.
Pancreatic polypeptide (upsilon cells) function?
modulates digestion of food by inhibition of gastric emptying as well as biliary secretion.
what cells produce Ghrelin ?
epsilon cells
what cells produce pancreatic polypeptides?
upsilon cells
how many adrenal glands?
There are two adrenal glands, one located on top of each kidney.
where are adrenal gland slocated?
on top of each kidney
shape of adrenal glands
They have a flattened pyramid shape 3-5 cm high and 2-3 cm wide.
the adnreal glands produce
hormones
like many other glands, they are under
under central control
what are the adrenal glands surrounded by…
Surrounded by a capsule of connective tissue and are highly vascularised.
the adrenal glandfs are differentiated into two regions :
Cortex and Medulla
The cortex comprises how uch of the adrenalg lands?
80-90% of the gland
function of the cortex of the adrenal glands
secretes hormones
how much of the adrenal glands are comprised of the adrenal medulla?
10-20% of the gland
medulla function??
secretes hormones
are the adrenal glands essential for life?
Yes! Loss of adrenal hormones leads to death by dehydration/electrolyte imbalance.
the cortex of tht adrenakl glands are subdivided into three zones?
zona glomerulosa (outer zone)
zona fasciculata (middle zone)
zona reticularis (inner zone)
Zona glomerulosa (outer zone) makes
mineralocorticoids (aldosterone).
Zona fasciculata (middle zone) makes
glucocorticoids (cortisol).
Zona reticularis (inner zone) makes
weak androgens (dehydroepiandrosterone – DHEA).
The adrenal medulla contains
chromaffin cells
function of chromaffin cells?
These are able to secrete Adrenaline (A) and Noradrenaline (NA).
Aldosterone is the major
mineralocorticoid produced by the adrenal gland.
functins of aldosterone
- The excretion of H+ ions into the urine to regulate the acid/base balance of the blood and prevent acidosis (blood pH < 7.35).
- Balancing the fluid and electrolyte levels (sodium Na+ and potassium K+).
- Regulating blood volume and blood pressure by regulating vascular resistance.
desribe the renin-angiotensis-aldosterone (RAA) pathway
1-4. Low blood pressure/volume causes secretion of renin.
5. Renin is a plasma protein that converts angiotensinogen into angiotensin I.
7-9. Angiotensin I is converted into angiotensin II by angiotensin-converting enzyme (ACE).
10. Angiotensin II causes cortex of adrenal glands to secrete aldosterone.
11-12. Increased levels of aldosterone causes retention of Na+ and water.
13-14. This causes an increase in blood volume and blood pressure.
15. Angiotensin II causes vasoconstriction of arterioles, also increasing blood pressure.
16. Increased extracellular K+ also stimulates aldosterone secretion.
Corticoid hormones (corticosteroids) are
stress hormones that are involved in a range of physiological processes, including regulating metabolism and the body’s stress response.
mechanism of corticoid hormones?
low blood cortisol causes neurosecretory cells in the hypothalamus to secrete corticotropin releasing hormone (CRH).
CRH stimulates?
the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary
ACTH travels in the blood to
the adrenal glands where it stimulates the production of glucocorticoids.
what does the cortex secrete?
- Secretes corticosteroid hormones
- Glucocorticoids
- Under control of ACTH
What do glucocorticoids do?
Remember – they are stress hormones, released by the body to deal with “challenging” situations.
what is the adrenal medulla?
The adrenal medulla is a modified sympathetic ganglion located at the centre of the adrenal gland.
what is the adrenal medulla made up of?
predominantly of chromaffin cells
what types of cells are the chromaffin cells?
neuroendocrine cells.
chromaffin cells do not function as…
…neurotransmitters.
rather than functioning as neurotransmitters, they …
… release hormones.
what is the adrenal medulla innervated by?
the autonomic nervous system (ANS)
The adrenal medulla is innervated by the autonomic nervous system (ANS) and can quickly …
stimulate catecholamine secretion
The adrenal medulla is innervated by the autonomic nervous system (ANS) and can quickly stimulate catecholamine secretion.
Specifically:
Adrenaline (epinephrine) – 80%
Noradrenaline (norepinephrine) – 20%
In the adrenal glands they are hormones – in the CNS they function as neurotransmitters.
What is the function of the adrenal medulla ?
Produce the ‘Fight of Flight’ response in response to stressful situations.
WHat are the effects of adrenal medulla function?
- Increase force and rate of heart contraction
- Increase blood pressure
- Dilate airways - B2 adrenoceptor
- Increase blood sugar by breaking down glycogen
what does the brain depend on to function?
The brain depends on glucose as fuel to function.
Reduction in brain glucose quickly leads to …
impairment of cognitive function, seizures, loss of consciousness, and permanent and irreversible brain damage.
During periods of hypoglycaemia, liver cells are stimulated by …
… glucocorticoids to convert amino acids or lactic acid into glucose (gluconeogenesis).
Additional glucose helps alleviate …
… stress by providing ATP to combat stresses
Additional glucose helps alleviate stress by providing ATP to combat stresses caused by:
- Exercise
- Fasting
- Fright
- Extremes of temperature
- High altitude
- Bleeding, trauma, and surgery
- Infection and disease
Stress can cause a higher susceptibility to
infection
Stress can cause a higher susceptibility to infection
This is caused by
an increase in the levels of cortisol.
- Anti-inflammatory action
what do Glucocorticoids inhibit ?
white blood cells during inflammation
High levels of glucocorticoids depress …
…the immune system.
- This can be good or very bad.
what reduces local inflammation in Psoriasis?
Topical corticosteroids
what lessens redness in Psoriasis ?
Hydrocortisone cream lessens the redness and prevents itching.
This is good.
in psoriasis, as topical corticosteroids / hydrocortisones creams suppress the immune response, they can…
… enable an infection to develop but hide the signs of infection.
This is bad.
If you have an organ transplant, you must take…
… drugs to prevent tissue rejection forever, or if the immune system is suppressed in an autoimmune disease glucocorticoid drugs will keep you alive.
This is good.
Getting the right balance between …
… suppression/infection is very difficult.
If the dose is not perfect, there is a …
… very high risk of opportunistic infection
If the dose is not perfect, there is a very high risk of opportunistic infection.
E.g…
Kaposi sarcoma (a type of tumour that causes lesions, on the skin caused by a form of the herpes virus)
This is bad.
what is Cushing’s syndrome caused by?
Caused by high levels of exposure to cortisol.
what is cushings syndrome?
- Overstimulation of the adrenal cortex by excessive hormone release
Cushings syndrome caused by Overstimulation of the adrenal cortex by excessive hormone release.
WHat are these hormones?
- Corticotrophin releasing hormone (CRH)
- Adrenocorticotropic hormone (ACTH) – corticotrophin
cushing syndromes Caused by high levels of exposure to cortisol.
which is
- Adrenal cortical adenoma secreting cortisol.
Very common benign tumour (up to 30% of us have it at death) but only 15% actually secrete hormones.
what tumours are present in cushings syndrome?
- ACTH secreting tumours
- These are not pituitary tumours as might be expected
- Called small cell carcinomas, they are highly malignant cancer, most commonly found in the lung
- They produce hormones including ACTH (ADH).
Exposure to glucocorticoid drugs (iatrogenic or side effects of treatment – preventable) can also cause cushings syndrome.
Usually through certain asthma/rheumatoid arthritis/immunosuppression
examples of glucocorticoid drugs which can cause cushings syndrome
iatrogenic or side effects of treatment – preventable
what are Cushing’s syndrome: symptoms?
Excessive gluconeogenesis
Elevated blood glucose
Glucose gets deposited as fat – moon face
Buffalo hump
Loss of lean muscle
Weakness
what does cushings syndrome treatment depend on?
Treatment depends on the cause.
what is the main Adrenal Androgen?
DHEA (Dehydroepiandrosterone)
what is DHEA (Dehydroepiandrosterone) ?
Steroid hormone precursor produced by the zona reticularis
whats the function of DHEA prior to puberty?
Prior to puberty it is the major androgen in males then testosterone takes over
whats the main androgen in females?
DHEA (Dehydroepiandrosterone) is the main androgen in females
DHEA function in males?
Pubic hair development, insignificant after puberty.
DHEA function in females?
- Sex drive (libido).
- Converted to oestrogen (female sex hormone) by other tissue in the body.
- After menopause, they will be the only source of oestrogen.
What is CAH stand for?
Congenital Adrenal Hyperplasia (CAH).
What is AGS stand for?
DHEA and Adreno-Genital Syndrome
What is Congenital Adrenal Hyperplasia (CAH)?
CAH is a group of conditions in which the adrenal gland is over – or under-active.
what is CAH caused by?
It is caused by a genetic defect that affects the enzymes that synthesise corticosteroid hormones.
what does CAH lead to?
Leads to insufficient cortisol production.
In CAH, low cortisol means…
… no negative feedback
in CAH, the anterior pituitary produces
a large amount of ACTH.
in CAH, In the developing foetus, the adrenal glands overproduce…
… large quantities of steroids.
- Some of these have strong androgenic activity.
what is the consequence of CAH in females?
In females the consequence is that the foetus and baby will be genetically female by may have ambiguous or male external genitalia.
CAH pathologies of females?
- Due to the overproduction of large quantities of steroids females may have a penis and scrotum (empty), or an enlarged clitoris.
- They will have female internal gonads (ovaries).
- Menstrual irregularity in adolescence.
- Infertility through failure to ovulate.
CAH pathologies of males?
- Most males show no phenotypic signs of CAH at birth.
- Some may soon show heart rhythm abnormalities, mineral imbalances (hyponatraemia), and low blood sugar levels (hypoglycaemia).
The Gonads (male testes and female ovaries), like many other glands, are under central control of…
… the hypothalamus.
The hypothalamus secretes …
… Gonadotrophin Releasing Hormone (GnRH).
GnRH acts on …
… the pituitary, stimulating the release of:
- Luteinising Hormone (LH)
- Follicle Stimulating Hormone (FSH)
what are the functions of oestrogen in females?
Responsible for secondary sexual characteristic:
Growth of breasts and pubic hair
Growth spurt and bone growth
Widening of the hips
More subcutaneous fat on the hips, thighs, and buttocks
Monthly development and release of one (1) ‘egg’
Proliferation of the endometrium during the menstrual cycle in preparation for pregnancy.
function of Luteinising Hormone (LH) in females?
Acts on the theca cells that surround the follicles that synthesise androgens (androstenedione) that is converted to oestrogens by the enzyme aromatase.
function of Follicle Stimulating Hormone (FSH) in females?
Stimulates immature ovarian follicles to develop and mature (oogenesis – egg development).
function of Luteinising Hormone (LH) in males?
Acts on the Leydig cells (interstitial cells) in the testes.
The Leydig cells synthesise testosterone.
function of Follicle Stimulating Hormone (FSH) in males?
Acts on the Sertoli cells to stimulate spermatogenesis (sperm production).
function of testosterone in males?
Responsible for secondary sexual characteristic:
Enlargement of the larynx and laryngeal muscle (voice drops).
Enlargement of the genitalia.
Growth of pubic and facial hair.
Bone growth (growth spurt).
Broadening of the shoulders.
Fusing of the epiphyseal plates.
the different gonadotropins?
Luteinising Hormone (LH)
Follicle Stimulating Hormone (FSH)
Testosterone / Oestrogen
go look at slide 70 and 71
