Endocrine System Flashcards
Describe Exocrine Glands?
Exocrine glands secret into ducts and so act locally. Sweat glands.
Describe Endocrine Glands?
No ducts. Secrete hormones into blood stream and so act at a distance.
What are some examples of endocrine glands and their associated hormones?
Metabolic rate - (Thyroid) Reproduction - Oestrogen/ testosterone) Stress Response - (Adrenaline&cortisol) Blood Glucose - (insulin glucagon) Blood Pressure - ADH, Aldosterone Immune system - Cortisol Growth (Growth Hormone) Blood Calcium (calcitonin/parathyroid)
Does the nervous system and the Endocrine system work closely together?
Yes. The nervous system works by releasing neurotransmitters into synaptic clefts and the Endocrine system works by releasing hormones into the blood stream.
What are some of the characteristics of NS and ES?
NS - Fast and short lasting and uses neurotransmitters at synapses
ES - Slow and long lasting and uses hormones produced in bloodstream.
Hormones only affect certain cells, how so?
Hormones only stimulate cells that have a matching receptor
What are the two hormone groups?
Water Soluble hormones (proteins) and Lipid Soluable hormones (steroids)
How do water soluble hormones work?
Mostly proteins.They require a second messenger receptor on the cell membrane?
Hypothalamic and pituitary hormones, GIT and insulin/adrenaline.
How do lipid soluble hormones work?
Mostly steroids. such as Sex hormones, cortisol, aldosterone, thyroid.
Lipid soluble hormones diffuse across the lipid portion and bind to receptors inside the cell
Describe the hypothalamus and pituitary gland and their connections?
The hypothalamus is the master gland and controls the pituitary. The pituitary is divided into two parts, the posterior pituitary (30%) and the anterior pituitary (70%). The PP is connected to the hypothalamus by neurons and is composed of nervous tissue while the AP is connected to the hypothalamus by blood vessels and is composed of glandular tissue.
What hormones do the PP and AP store and release?
The PP stores Oxytocin and ADH hormone and the AP stores six main hormones.
What does Oxytocin hormone do when released from PP?
Oxytocin release is triggered by a baby suckling on mothers breast and its release from PP activates milk ejection.
What do ADH hormone do when released from PP?
ADH acts on kidney to increase reabsorption in blood in order to decrease urine output
Decreases sweat production
What triggers stimulate the release of ADH?
Dehydration or severe blood loss.
What does the release of ADH stimulate?
- Increase reabsorption of water by kidneys
- Reduced sweat output
- Arteriole constriction to increase bp
- decrease urine output
What stimuli determine hormone release in both PP and AP?
In the PP regulated nervous system signals (ADH and Oxytocin)
In the AP chemical changes in the blood (insulin/glucagon)
What mechanism prevents the over secretion of hormones in the endocrine system?
Negative feedback
Discuss negative feedback in terms of Thyroid hormones.
- Low level of thyroid hormones or low metabolic rate stimulates thyrotropin releasing hormone (TRH) from hypothalamus
- In response to TRH the A-pituitary gland releases Thyroid Stimulating hormone (TSH)
- TSH into blood stimulates thyroid follicular cells which store thyroid hormones
- Thyroid Hormones released into blood by follicular cells
- Elevated TH inhibits release of TRH and TSH (negative feedback)
Discuss blood glucose homeostasis.
- Controlled by release of insulin and glucagon from pancreas.
- After a meal and BG is up, beta cells in islets of langerhans are stimulated to produce insulin = cellular uptake of glucose and decrease in BG
- After fasting and BG is down, alpha cells in islets of Langerhans are stimulated to produce glucagon which promotes glycogen breakdown in liver to increase BG
Discuss the basic composition and function of the adrenal glands.
Composed of outer cortex (85% of gland).
Outer cortex produces two groups of hormones
1) Mineralocorticoids - which controls electrolyte balance
2)Glucocorticoids - cortisol which controls long term stress response and metabolism -
The Inner medulla produces adrenaline and noradrenaline
What three malfunctions can cause endocrine disorders?
- To much hormone (Often cause by hypothalamic or pituitary tumour)
- To little hormone
- Reduced hormone sensitivity (insulin resistance)
Discuss Thyroid disorders, including congenital hypothyroidism.
Thyroid sets metabolic rate.
Hypothyroidism = low metabolic rate, weight gain, feel cold, tired, slow HR
Hyperthyroidism = high metabolic rate, weight loss,
Congential hypothyroidism affects 1/4000 babies and if untreated leads to mental and physical retardation
Discuss Iodine Deficiency Disorders (IDD)
Particularly virulent among peoples with low soil salinity and no access to seafood.
Can cause Goitre among adults and in bad causes neurological cretinism among pregnant women which damages fetal brain.
Discuss Growth Hormone Deficiency.
Lack of GH in childhood = Pituitary dwarfism
Surplus of GH in childhood = Giantism
In adult over secretion = Acromegaly
What are the major endocrine glands in the body?
Hypothalamus Pituitary Gland Thyroid & Parathyroid Thymus Adrenal Glands Pancreas Ovaries Testes
How to water soluble hormones reach their target receptor?
The hormone binds to a receptor on cell membrane. They then rely on a second messenger which brings about a change within the cell and the activity of its enzymes.
How do lipid soluble hormones reach their target organ?
They diffuse across the cell membrane and enter the cell and can therefore bring about a change in cellular activity without a second messenger.
What occurs in Diabetes Insipidus?
Causes a lack of ADH causing an increased urine volume leading to dehydration
What are the six hormones released by the pituitary gland under direction from the Hypothalamus?
Growth Hormone Prolactin Follicle stimulating hormone Luteinizing hormone Thyrotropic Hormone ACTH
What does the Thyroid gland regulate?
What hormones does it produce?
Metabolic Rate via hormones T3 & T4
Describe and example of hormonal positive feedback?
During labour - crowning at cervix stimulates the pituitary to secrete oxytocin which results in further contraction of uterus which increase pressure on cervix = positive feedback loop
What causes Hypothyroidism?
- Congenital
- Lack of Iodine
- Autoimmune disorder
- Following surgery for overactive thyroid
- Pituitary disorder
What causes Hyperthyroidism>
-Graves Disease (autoimmune) which causes expothalmaus
What can cause acromegaly?
Pituitary tumour
