The Endrocrine System Flashcards
Endo
Means within
Crine
To secrete
Glands
Organs which produce and secrete substances
Chemical messenger
A compound which transmits a message
What hormone does the heart produce
Atrial naturietic hormone
Why do we need the endocrine system
To maintain homeostasis
Homeostasis
The maintenance of relatively constant states within the body
Target cells
Cells processing the receptors for a specific hormone and so are receptive to their effects
Target organ
Organ/tissue containing the target cells for a specific hormone
Difference between endocrine systems exo and endo
What do endocrine glands do
Secrete hormones
Released direcetly into blood stream
Exocrine glands long answer
Secrete eg sweat and tears
Exo external
Release secretions out of the body via ducts
Referred to as ducted glands
Not apart of endocrine systems
10 major endocrine organs
MAIN IN EXAM ALWAYS multiple choice know the table well
Hypothalamus and pit where they found
Within lungs two primary endocrine organs what are they
Function of hormone
Hormones primarily serve to regulate the
metabolic function/cellular activity of other cells
Common hormone effects
– Alteration of plasma membrane permeability/electrical
state
– Stimulation of protein/enzyme synthesis
– Activation/deactivation of enzymes
– Stimulation of secretions
– Stimulation of mitosis
What is the functional classification of hormone
- Trophic hormones
- Sex hormones
- Anabolic hormones
What are trophic hormones
- Target other endocrine gland
Sex hormones
Target reproductive tissues
Anabolic hormones
Bring about anabolism in their target cells
Chemical classification of hormones - based on hormone structure
- Steroid hormones ———> steroid hormones
- Protein / polypeptide hormones
- Modified amino-acid hormones. —————-> non steroid hormones
What is the solubility of hormones
Steroid hormones are lipid-soluble
• Protein/polypeptide hormones are water-soluble
• Majority of modified amino-acid hormones are water-
soluble. Exceptions: thyroid hormones – lipid soluble
Receptor location depends on the solubility of the hormone
Where are receptors located for hormones
Either inside or on the surface of the target cell
Receptor location depends on the solubility of the hormone
How do water soluable hormones work
As they are unable to bund to phospholipid belayer.
They bund to the receptor on the surface of the target cell
As they cannot pass the plasma membrane, water soluable hormones do not affect gene transcription
How do lipid soluable hormone work
• Are able to cross the phospholipid bilayer and so …
• Bind to receptors inside the target cell
• As they can pass the plasma membrane, lipid-soluble
hormones are able to alter gene transcription
• They are therefore able to cause alteration of cellular
What are steroid hormones
Steroid hormones are lipid-soluble
• Secreted by, e.g. adrenal cortex, ovaries and testes
Steroid hormones are transported through the blood
by specialised carrier proteins
• They are mostly derived from cholesterol
Two main classifications of steroid hormones
Corticosteroids
Sex steroids
Examples of corticosteroids
Cortisol
Aldosterone
Non steroid hormones- protein/ polypeptide hormones
Protein/polypeptide hormones are water-soluble
• Secreted by, e.g. pituitary, pancreas
Examples of protein/polypeptide hormones
- Insulin & Glucagon
– Human growth hormone
– Follicle-stimulating hormone - anti diuretic hormone
Modified amino acid hormones - non steroid hormones
modified amino-acid hormones are water
soluble. Exceptions: thyroid hormones – lipid soluble
• Secreted by, e.g. thyroid gland, pineal gland
Have ine on the end
Based on amino acids tryptophan and tyrosine
Types of amino acid hormones
Tryptophan derived example:
– Melatonin
• Produced and secreted by pineal gland
• Has roles in the sleep cycle
• It is the only hormone known to be produced by the pineal gland
• Tyrosine derived examples:
– Thyroxine (T4), triiodothyronine (T3)
• Produced and secreted by thyroid
• Have roles in metabolic rate
– Epinephrine (adrenaline), norepinephrine (noradrenaline)
• Produced and secreted by medulla of adrenal gland
• Have roles in cardiac output and blood sugar levels. Fight or flight response
Hypothalamus
Situated at base of brain, superior to (i.e. above)
the pituitary gland
• Key role in homeostasis
• Primary roles …
– Signals pituitary to start/stop hormone production
– Produces a number of its own hormones
Function of hypothalamus
– Temperature regulation
– Thirst/water intake
– Hunger
– Behaviour
– Sleep cycles
Hormones produced by hypothalamus
Thyrotrophin Releasing Hormone
- Triggers Thyroid Stimulating Hormone (TSH) in pituitary
- Secretion of thyroxine from thyroid
• Corticotrophin Releasing Hormone
- Stimulates adrenocorticotrophic hormone (ACTH) in
pituitary
- Secretion of glucocorticoid hormones from adrenal cortex
• Growth hormone releasing hormone
- Stimulates human growth hormone
- Stimulates growth of bones, muscles etc
Pituitary
Situated at base of brain, inferior to (i.e. below) the
hypothalamus where it is connected via the infundibulum
(or pituitary stalk)
• Controlled by hormonal signals from hypothalamus
Function of pituitary
Causes hormone production and secretion which
signal/control other organs of the endocrine system,
notably thyroid gland, adrenal gland and gonads
What is the pituitary gland also referred as
Master gland
What are the two lobes of the pituitary gland
Anterior pituitary gland
Posterior pituitary gland
Both produce hormones - connected by intermediate lobe
Hormones secreted by anterior lobe
– Adrenocorticotropic hormone (ACTH)
• Maintains growth and development of the adrenal gland
• Stimulates adrenal gland cortisol and epinephrine production
– Follicle-stimulating hormone (FSH)
• Involved in sexual development (ovaries and testes)
• Control of menstrual cycle and control of sperm production
– Luteinising hormone (LH)
• Involved in sexual development (ovaries and testes)
• Control of menstrual cycle and control of sperm production
Hormones secreted by the posterior lobe
– Antidiuretic hormone (ADH)
• Produced by hypothalamus but stored & released by pituitary
• Serves to decrease urine volume and increase blood pressure
– Oxytocin
• Uterus contraction during childbirth
stimulates lactation
Pineal gland
• Pineal gland is situated deep within centre of the brain
• It sits within the region where the two halves (called
hemispheres) of the brain join
Produces hormone melatonin - derived from serotonin
Melatonin known to control out circadian
Thyroid gland
• Butterfly-shaped gland located in the neck.
• It is anterior to the trachea, inferior to the larynx
• Composed of two lateral lobes connected by an isthmus (a
constricted/narrowed ‘bridge’ between organs/part of)
• Associated with 4 parathyroid glands in calcium deposition
Thyroid gland functions
– Regulation of metabolism
• Thyroid hormones (TH)
– Growth and development
• Thyroid hormones (TH)
– Calcium deposition in bone
Calcitonin
What is thyroid tissue composed of
Thyroid follicles
Thyroid follicles
– Structural and functional units of the thyroid
– Round with a wall of densely packed follicular cells
– Follicular cells: Site of thyroid hormone production
Thyroid hormone
TH
Primary TH hormones
- Tetraiodothyronine (Thyroxine) (T4)
- Triiodothyronine (T3)
• T3 is more potent and is the main TH
Higher TH
Higher metabolic rate
Hypothyroidism
under-production of thyroid hormones
– Associated with weight gain, tiredness, impaired mental function
Hyperthyroidism
over-production of thyroid hormones
– Associated with weight loss, irritability, increased body
temperature
Hormones produced by thyroid gland
- Tetraiodothyronine (T4)
- Triiodothyronine (T3)
- Calcitonin (CT)
What do spaces between thyroid follicles contain
C cells which produce calcitonin (CT)
Serves to decrease blood calcium levels and increase calcium
What are C cells known as
Parafollicular cells
Para - next to / adjacent to
Adjacent to thyroid follicles
parathyroid glands
• Located on or near (hence, ‘para’) the posterior of the
thyroid
• Remember: thyroid has two lateral lobes, left and right
• Parathyroid glands are roughly situated on or near
each quadrant of the overall thyroid gland
• They are located on the posterior region of the lobes
• The parathyroid glands produce parathyroid
hormone (PTH)
Function of PTH
Raises blood calcium levels by removing calcium from bone
The itwo hormones work together to maintain the balance of blood calcium levels
Abnormal parathyroid function
• Hypoparathyroidism = under-production of PTH
– Causes decreased blood calcium levels → increased bone
calcium. Can cause muscle pains/cramps, tiredness and mood
alterations – anxiousness and depression
• Hyperparathyroidism = over-production of PTH
– Causes increased blood calcium levels → decreased bone
calcium. Can cause joint and bone pains, leading to osteoporosis.
Thymus
• Located in the chest between the lungs
• Posterior to the breastbone (sternum)
• Anterior to the primary blood vessels
• Composed of two lobes, left and right
Produces range of polypeptide hormones (thymopoietin)
Role of thymus
Roles in production and maturation of T-lymphocytes (T-
cells) from thymocytes (form of immune cell in thymus
What are thymus linked conditions
Myasthenia gravis
– Rare autoimmune disorder affecting neuromuscular system
Pure Red Cell Aplasia (PRCA)
– Another rare autoimmune disorder, affecting production of
red blood cells (erythrocytes) in the bone marrow, causing
anaemia
• Anaemia:
Pancreas
• Situated within the abdomen, posterior to the stomach
• Long and flat organ
• Has endocrine and exocrine function
Exocrine function of pancreas
– Key role in digestion where is secretes digestive enzymes
into the start of the small intestine (called the duodenum)
– Enzymes for carbohydrate, lipid and protein breakdown
Endocrine function of pancreas
Primarily concerned with production of the hormones insulin
and glucagon in regulation of blood glucose levels
Hormones are secreted by special cells of the islets of langerhans 5 key cell types
Alpha cells - produce glucagon serves to raise blood glucose level
Beta cells - produces insulin serves to decrease blood glucose level
Delta cells - produce somatostatin also known as growth hormone inhibiting - inhibits insulin and glucagon
Gamma cells ( PP cells)
Produce pancreatic polypeptide regulates pancreatic function through reduction of appetite
Episilon cells - produce gherlin serves to induce feelings of hunger also inhibits insulin secretion
Alpha cells role in blood glucose regulation
Alpha and Beta Cells’ Blood Sugar Response
• Alpha cells detect blood glucose drop.
• Release glucagon.
• Glucagon circulates to liver for glycogen breakdown.
• Increased blood sugar levels.
Beta cells role in blood glucose regulation
• Beta cells release insulin when blood glucose rises.
• Insulin circulates throughout the body via the bloodstream, binding to cell surface insulin receptors.
• Insulin binding causes glucose transport proteins to move from cytoplasm to plasma membrane.
• Facilitated diffusion of glucose into cells reduces blood sugar levels.
Adrenal gland
• Adrenal glands are situated above the kidneys
• One adrenal gland above each kidney
• Each adrenal gland has two primary regions
– Adrenal cortex (the outer region)
– Adrenal medulla (the inner region)
Adrenal cortex
Produce steroid hormones cortisol
Cortisol plays role in stress response
Promotes glucose production
Glucose release into blood -> increased blood sugar levels
What hormone does adrenal gland produce
Aldosterone - role in the salt:water balance of
the body where it targets the nephrons of the kidneys
– It promotes reabsorption by the body of sodium and water
from the tubules of the nephrons
Decrease in urine vol
Increase in bp
Ovaries
They are oval in shape and are situated either side of
the uterus (womb)
• Females have two ovaries which produce and release
eggs (termed oocytes)
• responsible for producing the
hormones oestrogen and progesterone and their
release is controlled by the hypothalamus
Hormones produced by ovaries
Oestrogen- stimulates breast development
Development of reproductive organs
Progesterone
During pregnancy increases
Helps maintain endometrium between ovulation and menstruation
Testes
• Male equivalent of ovaries.
• Oval shape located in scrotum.
• Suspended by spermatic cord.
• Produce and release sperm.
• Responsible for testosterone production.
Testes - testosterone
• Secreted by Leydig cells of testes.
• Promotes male reproductive organ development.
• Stimulates public and chest hair production.
• Promotes muscle growth and development.
• Release controlled by hypothalamus and pituitary.
