5. Endocrine System Flashcards
Give examples of endocrine glands
-Pituitary
-Thyroid
-Parathyroid
-Adrenals
-Pancrease
-Ovaries and Testes
-Pineal
Is the hypothalamus a gland?
-No, it is better described as a neuroendocrine organ, as it integrates the nervous and endocrine systems.
-but it does produce releasing and inhibiting hormones that regulate the pituitary gland
Give some hormones that the hypothalamus releases
-Thyrotropin releasing hormone (TRH)
-Corticotropin releasing hormone (CRH)
-Gonadotropin releasing hormone (GnRH)
-Growth hormone releasing hormone (GHRH)
-Somatostatin
-Dopamine
-Vasopressin and Oxytocin
Describe how the pituitary gland is divided?
Into two main lobes:
-Anterior pituitary (adenohypophysis): Releases hormones in response to signals from the hypothalamus
-Posterior pituitary (neurohypophysis): Stores and releases hormones produced by the hypothalamus
Give hormones released by the anterior lobe of the pituitary gland
-Growth Hormone (GH)
-Thyroid stimulating hormone (TSH)
-Adrenocorticotropic hormone (ACTH)
-Luteinising hormone (LH)
-Follicle stimulating hormone (FSH)
-Prolactin
Give hormones released by the posterior lobe of the pituitary gland
-Oxytocin
-ADH/Vasopressin
Give the hormones released by the thyroid gland, and their functions
-T4 and T3, both involved in increasing metabolism and energy production, body temperature regulation, growth and development and heart rate and digestion
-Calcitonin, involving in lowering blood calcium levels by inhibiting bone breakdown and promoting calcium storage in bones
What regulates the activity of the thyroid gland?
-Hypothalamus release of TRH leads to stimulation of TSH release
-TSH stimulates the thyroid gland to release T3 and T4
-High T3 and T4 inhibit TRH and TSH release through negative feedback
Give the hormone that the parathyroid gland releases, and their functions
-Parathyroid hormone
-Plays a crucial role in calcium homeostasis, acting on the bones, kidneys and intestines
Give the hormones that the pancreas releases, and their functions
-Insulin, lowering blood glucose levels
-Glucose, increasing blood glucose levels
-Somatostatin, inhibits insulin and glucagon release to prevent extreme fluctuations in blood glucose levels
-Pancreatic polypeptide, regulating pancreatic enzyme secretion
Give the hormones that the adrenal glands release, and their functions
-Cortisol (glucocorticoids) regulating metabolism and immune response, helping the body respond to stress
-Aldosterone (mineralocorticoids) regulating sodium and potassium reabsorption, controlling blood pressure
-Androgens acting as precursors to sex hormones
-Catecholamines as part of fight or flight stress response
Give the hormones that the testes release, and their functions
-Testosterone, involved in development of male reproductive tissues, promoting secondary sexual characteristics and promotes spermatogenesis
-Inhibin, involved in the inhibition of the secretion of FSH, regulating sperm production
-Estradiol in small amounts, involved in sperm maturation
Give the hormones that the ovaries release, and their functions
-Oestrogen, involved in development of female reproductive tissues, promoting secondary sexual characteristics, regulates the menstrual cycle and aids in maturation of oocytes
-Progesterone, involved in preparing the uterus and regulating the menstrual cycle. Helps prevent further ovulation during pregnancy.
-Inhibin, involved in inhibition of FSH and works in controlling number of eggs maturing in each cycle
Describe simply endocrine communication
Hormones are secreted into the bloodstream and bind to target cell receptors
Give the sections of the adrenal glands
-Adrenal cortex (outer layer)
-Adrenal medulla (inner layer)
Give the sections of the adrenal cortex
-Zona glomerulosa (outermost layer)
-Zona fasciculata (middle layer)
-Zona reticularis (innermost layer)
Give the hormones secreted by each section of the adrenal cortex
-Z Glomerulosa secretes mineralocorticoids (aldosterone)
-Z Fasciculata secretes glucocorticoids (cortisol)
-Z Reticularis secretes androgens (DHEA)
Give the hormones secreted by the adrenal medulla
-Adrenaline
-Noradrenaline
Describe the mechanism of action by which steroid hormones act
-Lipid soluble hormones (eg thyroid hormones) bind to carrier proteins until they reach target tissues
-Diffuse easily through the cell membrane due to fat solubility
-Bind to intracellular receptors inside the cell
-Hormone receptor complex enters the nucleus and binds to promoters to regulate the transcription of target genes
-These genes are translated and carry out specific cellular effects
Describe the mechanism of action by which water soluble hormones act
-Peptides, proteins and catecholamines are hydrophilic, meaning they cannot pass through the cell membrane
-They bind to specific receptors on the plasma membrane of the target cell
-This signal is transducer through an intracellular signalling pathway (often involving second messengers)
-The second messengers activate protein kinases, which in turn alter the activity of other proteins
-Eliciting a cellular response
