Endocrine system Flashcards
What are the two control system of homeostasis and what are their differences?
AUTONOMIC NERVOUS
SYSTEM:
-Rapid change.
-Less precise.
-Shorter duration.
-Neurotransmitters.
-Control centre:
Central nervous system
ENDOCRINE SYSTEM
-Slower change.
-More precise.
-Longer duration.
-Hormones.
-Control centre:
Hypothalamus.
What are the two types of glands?
- EXOCRINE
* Excrete products into ducts leading to
body cavities / organ / skin.
* Examples: Salivary glands (saliva), gastric
glands (digestive enzymes), mammary glands. - ENDOCRINE
* Ductless, secreting hormones directly into
the blood.
* Examples: Pituitary, adrenals, thyroid.
List the name of the 10 endocrine glands.
- Hypothalamus (neuroendocrine gland).
- Pituitary (glandular and neuroendocrine).
- Pineal.
- Thyroid.
- Parathyroid.
- Adrenal.
- Pancreatic: islets of Langerhans.
- Thymus.
- Ovaries.
- Testes.
List the seven endocrine tissues
- Adipose tissue — leptin (suppresses food intake) and resistin
(blood glucose). - Heart — atrial natriuretic peptide (blood pressure).
- GIT — stomach: ghrelin and gastrin (satiety and gastric emptying).
- Liver — angiotensinogen, insulin-like growth factor (IGF),
thrombopoietin. - Placenta — human chorionic gonadotropin (hCG) and progesterone.
- Kidneys — erythropoietin (RBC production) and calcitriol (vit. D).
- Skin — cholecalciferol (vit. D).
What is down regulation and up regulation hormone?
- If a hormone is present in
excess, the number of target
cell receptors may
decrease. - Example: Hormones
increase during puberty. - A deficiency in hormone
causes an increase in the
number of receptors on target
cells. - Example: Increased number
of oxytocin receptors in third
trimester of pregnancy.
Which gland is the master endocrine gland?
Pituitary gland as it controls other glands and is regulated by hypothalamus
How are hypothalamus and pituitary gland connected?
The hypothalamus and pituitary
gland are connected by a stalk of
nerve fibres and network of
capillaries.
List of hypothalamus and anterior pituitary hormones
-Tyhrotrophin releasing hormone (TRH)- Thyroid stimulating hormone(TSH)- Targets thyroid gland
-Growth hormone releasing hormone(GHRH) and growth hormone Inhibiting hormone(GHIH)- Growth hormone(GH)- Targets most body tissues
-Corticotropin releasing Hormone (CRH)- Adrenocorticotropic hormone (ACTH) and Melanocyte stimulating Hormone(MSH)- Targets adrenal cortex and skin
- Prolactin releasing hormone(PRH) and Prolactin inhibiting hormone(PIH) (Dopamine)- Prolactin(PRL)- Targets breasts
-Gonadotropin releasing hormone (GnRH)- Follicle stimulating hormone (FSH) and Luteinising Hormone (LH)-
Targets Ovaries and Testes
What are the two posterior pituitary hormones?
Oxytocin and Antidiuretic hormone (ADH)
What are the functions/activities of Growth hormone and when do they have increased production?
ACTIVITY:
1. Regulates metabolism in many organs.
2. Stimulates release of insulin-like
growth factors (IGFs) in cells.
3. Promotes growth and division of most
body cells (especially bone and muscle).
4. Breaks down fats and glycogen.
INCREASED PRODUCTION:
* Night-time (sleep — stage three, four).
* Hypoglycaemia.
* Exercise.
* Childhood and adolescence
What are the functions/activities of thyroid glands and when they have increased production?
ACTIVITY:
1. Growth and activity of the
thyroid gland: Increasing
thyroid hormone production
— thyroxine (T4) and triiodothyronine (T3).
PRODUCTION:
* Lowest levels in the early
evening and highest during
the night.
What are the functions/activities of Adrenocorticotropic glands and when they have increased production?
ACTIVITY:
1. Output of steroid hormones:
Glucocorticoids, especially cortisol.
2. Circadian rhythm (sleep / wake cycle).
INCREASED PRODUCTION:
* Hypoglycaemia.
* Exercise.
* Stressors such as emotions, fever.
* Interleukin-1 (inflammatory
response to infection).
PRODUCTION:
* Highest in the morning and lowest
at midnight.
What are the functions/actions of Prolactin hormone and when is it produced more?
ACTIVITY:
1. Stimulates lactation:
Prolactin + oxytocin = lactation.
2. Prevents pregnancy during lactation
(inhibits GnRH).
3. Breast maturation after childbirth.
Matures mammary glands in pregnancy.
PRODUCTION:
* After birth (delivery of placenta).
* Suckling: the more milk removed, the more produced.
* Emotional stress.
* Sleep.
Follicle stimulating hormone and luteinising hormone?
- FSH:
- Production of gametes (sex cells)
in males and females. - Increases oestrogen production (F).
- Stimulates testosterone production (M).
- LH
- Triggers ovulation and formation of the
corpus luteum in females. - Increases secretion of progesterone (F).
- Stimulates secretion of testosterone (M).
Melanocyte stimulating Hormone
Produced by the anterior pituitary in
response to UV light.
* Stimulated by corticotropin releasing
hormone (CRH) — released from
hypothalamus. So MSH and ACTH
share CRH as their precursor hormone.
* Role in skin, hair and eye pigmentation
in humans.
* Can be excessively produced as part of some
pathologies, such as the hyperpigmentation
of skin seen in Addison’s disease.
Oxytocin
ACTIVITY:
1. Contracts uterus in childbirth (parturition).
2. Contracts lactating breast.
3. Bonding hormone (mother with baby):
Social bonding, trust, skin contact,
cuddle hormone.
PRODUCTION:
* Suckling.
* Childbirth (positive feedback).
* Emotional state: Fear or anxiety may
inhibit release of oxytocin or milk let-down. Emotions can
trigger oxytocin — just hearing baby’s cry can start lactation
Antidiuretic hormone (ADH)
Hypothalamus monitors concentration of body
fluid.
ACTIVITY:
1. Reduces urine output by stimulating
reabsorption of water in the kidneys.
2. Vasoconstriction in skin and abdominal
organs to increase blood pressure.
PRODUCTION:
* Increased osmotic pressure, hypovolaemia
(reduced fluid intake, thirst, vomiting).
INHIBITION:
* Reduced osmotic pressure, increased fluid
intake, alcohol.
Pineal Gland: Melatonin
The pineal gland is a small pea-sized gland in the
midline of the brain that produces melatonin.
* Specialised photoreceptors in the retina detect light /
darkness cues.
* Levels are highest in children and decline with age.
* Stimulated by: Night, darkness (retinal feedback).
* Reduced by: Daylight, irregular sleep
patterns (jetlag, night-shifts).
ACTIVITY:
* Setting of the circadian rhythm:
Metabolic, physiological and behavioural
alterations that follow a 24-hour rhythm.
* A potent antioxidant, DNA protective.
Thymus gland: Thymosin
The thymus is a bi-lobed gland, located
behind the sternum, which plays an
important role in immune development.
* The thymus atrophies after puberty and
is replaced by fibrous tissue.
ACTIVITY:
* Hormones produced by the thymus
promote the maturation of T-Lymphocytes. *
* Immature T-cells migrate from the red bone
marrow to the cortex of the thymus. Mature
T-lymphocytes then migrate to the lymphatic system
Thyroid Gland
A butterfly-shaped gland that is inferior to the
larynx and located either side of the trachea.
* Influences metabolic rate (catabolic + anabolic)
and is an important ‘growth hormone’ in early life.
* Follicular cells produce thyroid hormones:
* Thyroxine (T4) — has four iodine atoms.
* Triiodothyronine (T3) — has three iodine atoms.
* T4 and T3 are synthesised from iodine and a
specialised thyroid protein called thyroglobulin
(Tg) rich in tyrosine.
* Follicular cells trap and store most of the body’s
iodide via active transport from blood to cytosol.
Thyroid Hormone
The major form of thyroid hormone in the blood
is thyroxine (ratio of T4 to T3 is approx. 20:1).
* Selenium-containing enzymes are used in the conversion
of T4 to T3. Zinc is also needed for this.
* T3 is the more biologically active form:
Three-four times more potent than T4.
* This allows the body to maintain a stable
pool of thyroid hormones from which the
active, free hormones can be released as
required.
* Thyroid hormone levels are measured in terms of free T4 and T3.
* Most body cells have receptors for thyroid hormones.
ACTIVITY
:
* Increase metabolic rate and heat production. * Essential for normal growth and
development and CNS function.
* Work in conjunction with adrenaline and
noradrenaline, insulin and growth hormone.
PRODUCTION: * Stimulated by: TSH, exercise, stress,
malnutrition, low blood glucose, low T3 to T4
- Reduced by: Low TSH, high T3
- Highest levels at night. * Higher levels during adolescence,
pregnancy and female reproductive years.
Adrenal Glands
The adrenals are paired glands superior
to the kidneys. Divided into the:
1. Medulla (inner): Part of the autonomic NS,
producing:
* Adrenaline (epinephrine).
* Noradrenaline (norepinephrine).
* Dopamine.
2. Cortex (outer): Produces three groups
of steroid hormones:
* Glucocorticoids (mostly cortisol).
* Mineralocorticoids (mostly aldosterone).
* Sex hormones (mostly androgens).
Adrenaline and Noradrenaline
Adrenaline (80%) and noradrenaline (20%)
are produced by the adrenal medulla.
* They both intensify the sympathetic response.
* Released by chromaffin cells (quick release
because innervated directly by sympathetic NS).
* Adrenaline has greater influence on the heart.
Noradrenaline affects blood vessels.
* Stimulated by: Exercise, fasting, shock,
elevated temperature, infection, disease,
emotional stress, caffeine.
* Inhibited by: Eating, sleeping, calmness,
diaphragmatic breathing.
Glucocorticoids
Steroid hormones produced in the
adrenal cortex which regulate
metabolism and resistance to stress.
* This is mostly cortisol.
ACTIVITY:
1. Stimulating gluconeogenesis.
2. Proteolysis (amino acids from protein).
3. Lipolysis.
4. Production of glucose by the liver.
5. Reduces immune response (and tissue repair).
6. Anti-inflammatory — hence therapeutic use of steroids.
7. Weak reabsorption of sodium and water from kidney tubules
