Endocrine System Flashcards
What are endocrine glands?
Secrete their product into the extracellular space around the secretory cells. Secretion then diffuses into blood capillaries to be carried to target cells e.g. hormones
What are exocrine glands?
Secrete their product into ducts. Ducts carry the secretion into body cavities, into the lumen of an organ, or to the outer surface of the body. e.g. saliva, sweat, tears etc
What is the hypothalamus?
Works with the pituitary to regulate nearly all aspects of growth, development, metabolism and homeostasis
What is the job of releasing hormones?
To instruct the pituitary gland to produce and release its hormones made in the glands anterior lobe.
Which hormones are releasing hormones?
- CRH - Corticosteroid releasing hormone
- GHRH - Growth hormone releasing hormone
- GnRH - Gonadotrophic releasing hormone
- TRH - Thyrotrophic releasing hormone
What is the pituitary?
A small sized grape like gland attached to the hypothalamus by the infundibulum
What is the infundibulum?
Contains the hypophyseal portal veins and axons of the hypothalamic neurones. It is split into the anterior and posterior
What is the posterior pituitary?
Stores and releases the hypothalamus hormones ADH and oxytocin
What is anterior pituitary?
This manufactures and secretes hormones in response to releasing or inhibiting hormones from the hypothalamus
What is the thyroid gland?
Butterfly shaped gland situated below the larynx
What are follicular cells?
Secrete and store T3 and T4 (both forms of thyroxin) to regulate the metabolic rate it requires iodine to produce these hormones
What are parafollicular cells?
Make calcitonin inhibits the activity of osteoclasts to decrease calcium in the blood
What are parathyroid glands?
The number of parathyroid glands varies, some are attached to the thyroid gland but there may also be some free glands in the neck. Produces parathyroid hormone to regulate the levels of Ca2+, Mg2+ and HPO42- in the blood by enhancing the breakdown of bones and reducing or increasing loss by kidneys.
What are pancreatic islets?
Main products are glucagon and insulin
What is insulin?
reduces blood glucose levels by enabling glucose to enter the cells for use in the mitochondria and into the liver for storage
What is glucagon?
Increases blood glucose by triggering the livers capacity to convert glycogen (the storage form of glucose) back to glucose. The glucose can circulate and be used by the cells energy
What is diabetes mellitus?
The loss or inability to maintain blood glucose homeostasis. Chronically high levels of blood glucose can damage capillaries and caused vascular disease
Where are the adrenal glands?
Located on the top of the kidney
What are the inner adrenal medulla?
Contains sympathetic neutrons of the autonomic nervous system which produced adrenaline and noradrenaline
What is the outer zone of the adrenal cortex?
Makes mineralocorticoids to regulate mineral ions e.g. aldosterone affects the kidneys to increase plasma Na+ as a result increases water reabsorption in kidneys
What is the middle zone (zona fasciculate) of the adrenal cortex?
Makes glucocorticoids e.g. cortisol to increase protein and lipid turnover, increases livers ability to convert glucose and it decrease inflammation
What is the inner zone of the adrenal cortex?
Makes androgen
What are the pineal glands?
A small gland attached to the roof of the third ventricle of the brain. Secretes melatonin in the dark and during sleep to influence the body’s biological clock
What are the thymus glands?
Produces thymosin. Located close to the heart in the mediastinum. Large in infants and smaller in adults. Promotes T - lymphocyte synthesis (white blood cells)
What are the other endocrine tissues?
- Stomach - gastin and grehlin = hunger hormones
- Placenta - progesterone = keeps pregnancy going
- Embryo - chorionic gonadotrophin = present in pregnancy tests
- Adipose tissue (fat cells) - leptin = feeling full
- Duodenum - GIP and cholecystokinin = coordinating the activity in the duodenum
What are the 3 classes hormones are grouped into based on their structure?
- Peptides
- Amines
- Steroids
What do all hormones act as?
Receptors
What do steroidal hormones do?
Diffuse into cells and are primary messengers
What do peptide hormones do?
Cannot enter cells. Binding to a target cell activates cAMP or calcium as a secondary messenger system inside the cell
What do amine hormones do?
Function like peptides and some like steroids
What is the control of hormone secretion?
Hormone production and secretion can be stimulated and inhibited by -
1) signals from the nervous system e.g. nerve impulses to the adrenal medulla regulate the release of adrenaline
2) Chemical changes in the blood e.g. blood Ca2+ level regulates secretion of parathyroid hormone
3) Other hormones e.g. adrenocorticotropic hormone form the anterior pituitary gland stimulates release of glucocorticoids by the adrenal cortex
What does the endocrine system do?
Responds slowly to stimuli but produces long lasting results to maintain homeostasis.
Which hormone is released by the pineal gland?
Melatonin
Which hormones are released by the thyroid gland?
- Triodothyronine (T3)
- Thyroxide (T4)
- Calcitonin
Which hormones are released by the parathyroid gland?
Parathyroid hormone
Which hormones are released by the adrenal cortex?
- Glucocorticoids
- Mineralocorticoids / Aldosterone
Which hormones are released by the adrenal medulla?
- Adrenaline
- Noradenaline
Which hormones are released by the kidneys?
- Erythropoietin
- Calcitriol
Which hormones are released by the testes?
Androgen
Which hormones are released by the ovaries?
- Estrogen
- Progesterone
Which hormones are released by the pancreas?
- Insulin
- Glucagon
Which hormones are produced in the thymus?
Thymosin
Which hormones are secreted in the posterior lobe of the pituitary glands?
- ADH
- Oxytocin
Which hormones are secreted in the anterior lobe of the pituitary glands?
- ACTH - Adrenocorticotropic hormone
- TSH - Thyroid stimulating hormone
- GH- Growth hormone
- PRL- Prolactin
- FSH - Follicle stimulating hormone
- LH - Luteinising hormone
