The Endocrine System Flashcards
1.1 Define a hormone.
Specialised chemical messengers that alter the activity of a target cell.
1.1 Define the endocrine system.
A controlling system that produces and secretes hormones to influence metabolic activities through the blood.
1.2 Difference between endocrine and exocrine glands.
Exocrine glands secrete through ducts onto an epithelial surface. Endocrine glands secrete messengers into the bloodstream.
1.3 List 3 similarities and differences between the endocrine and nervous systems
Similarities: (x3)
○ Act via receptors
○ Hormones and neurotransmitters have multiple effects on the same organ
Chemicals can act as both neurotransmitters and hormones
Differences: (x3)
○ Communication: Endocrine communicates via chemicals, nervous system communicates via chemicals and electrical signals.
○ Distribution: Endocrine is widespread, nervous system is localised and specific.
○ Reaction to stimuli: endocrine is slow, nervous is fast
1.4 List the 2 main chemical classes of hormones and give examples of each
Steroids: Testosterone
Non-stoirds: Adrenaline/melatonin
1.5 Describe how hormones are transported to their site of action
Steroid are hydrophobic, must bind to transport hormones in blood. Target cells in nucelus
Non steroids are hydrophillic and mix easily with blood plasma. Target cell is cell membrane
1.6 Describe how hormones stimulate their target cells & state any differences between the main chemical groups of hormones
Steroid: lipid soluble & receptors are found within target cells cytosol. Binds to receptor molecule
Non steroids: cannot pass through cell membrane. Bind to receptor proteins on cell surface which activates second messengers (cAMP)
1.7 Describe how target cells can adjust their sensitivity to a hormone
Sensitivity = number of receptors
Up-regulation = increased cell receptors and cell sensitivity
Down regulation = decreased cell receptors and cell sensitivity
2.1 Describe the anatomy of the hypothalamus & pituitary gland & their relationship to each other (Hypothalamus)
Location: region of the diencephalon, forms the floor/part of walls of third ventricle. Superior to pituitary gland.
Function: major control centre of endocrines and ANS.
2.1 Describe the anatomy of the hypothalamus & pituitary gland & their relationship to each other (Pituitary)
Location: base of brain, inferior to hypothalamus, in sella turcica
Two regions: anterior and posterior
Connected to hypothalamus through stalk with a blood portal system. neural linkage for posterior pituitary and hypothalamus
2.2 List hormones produced by the hypothalamus, Whats the target organ/s or tissue & state principal effects of (TRH)
TRH: Thyrotropin-releasing hormone
Promotes secretion Prolactin (PRL) and Thyroid-stimulating hormone (TSH)
2.2 List hormones produced by the hypothalamus, Whats the target organ/s or tissue & state principal effects of (CRH)
(CRH) - Corticotropin-releasing hormone
Promotes secretion Adrenocorticotropic hormone (ACTH)
2.2 List hormones produced by the hypothalamus, Whats the target organ/s or tissue & state principal effects of (GnRH)
(GnRH) - Gonadotropin-releasing hormone
Promotes secretion follicle-stimulating hormone (FSH) and Luteinizing hormone (LH)
2.2 List hormones produced by the hypothalamus, Whats the target organ/s or tissue & state principal effects of (GHRH)
(GHRH) - Growth hormone-releasing hormone
Promotes secretion Growth hormone (GH)
2.2 List hormones produced by the hypothalamus, Whats the target organ/s or tissue & state principal effects of (PIH)
(PIH) - Prolactin-inhibiting hormone
Inhibits secretion Prolactin (PRL)
2.2 List hormones produced by the hypothalamus, Whats the target organ/s or tissue & state principal effects of Somatostatin
Somatostatin
Inhibits secretion Growth hormone (GH) and Thyroid stimulating hormone (TSH)
2.3 List hormones produced by the anterior pituitary gland, list target organ/s or tissue & state principal effects of (FSH)
(FSH) - Follicle-stimulating hormone
Target: Ovaries and Testes
Effect: F- Growth of ovarian follicles and secretion of estrogen, M- sperm production.
2.3 List hormones produced by the anterior pituitary gland, list target organ/s or tissue & state principal effects of (LH)
(LH) - Luteinizing hormone
Target: Ovaries and Testes
Effect: F- ovulation, maintenance of corpus luteum, M- testosterone production.
2.3 List hormones produced by the anterior pituitary gland, list target organ/s or tissue & state principal effects of (TSH)
(TSH) - Thyroid-stimulating hormone
Target: Thyroid gland
Effect: growth of thyroid gland, secretion of thyroid hormone.
2.3 List hormones produced by the anterior pituitary gland, list target organ/s or tissue & state principal effects of (ACTH)
(ACTH) - Adrenocorticotropic hormone
Target: Adrenal cortex
Effect: growth of adrenal cortex, secretion of glucocorticoids.
2.3 List hormones produced by the anterior pituitary gland, list target organ/s or tissue & state principal effects of (PRL)
(PRL) - Prolactin
Target: mammary glands, testes
Effect: F- Milk synthesis, M- increased (LH) sensitivity
2.3 List hormones produced by the anterior pituitary gland, list target organ/s or tissue & state principal effects of (GH)
(GH) - Growth Hormone
Target: Liver, bone, cartilage, muscle, fat
Effect: widespread tissue growth, especially in the stated tissues.
2.4 List hormones stored by the posterior pituitary gland, list target organ/s or tissue & state principal effects
(ADH) - Antidiuretic hormone
○ Target: Kidneys
○ Effect: Water retention
(OT) - Oxytocin
○ Target: Uterus, mammary glands
○ Effect: Labour contractions, milk release, ejaculation, sperm transport
2.5 Explain how pituitary secretion is controlled by the hypothalamus and target organs and exemplify using multiple examples
Anterior Pituitary Control: Hypothalamus secretes hormones into blood. Travels to hypophyseal portal system. Adenohypophysis is where the target cells of releasing hormones are located. Feedback loop.
Posterior Pituitary Control: regulated by hypothalamus, brain centres and feedback from organs. feedback can be positive or negative hence increase or decrease section of hormones.
2.6 Describe the effects of growth hormone
Growth Hormone has widespread effects on the body tissues especially on cartilage, bone, muscle and fat.
Bone growth at epiphyseal plates, thickening, and remodelling of bone are influenced during childhood.
3.1 Pineal gland; state its location, list the hormone/s it produces and their effects
Location: in centre of the brain between the two hemispheres, in roof of third ventricle.
Hormones/Effects: Melatonin - body’s biological clock and sleep/wake cycles
3.2 Thyroid gland; state its location, describe its structure, list hormones produced & their effects
Location: in the neck inferior to larynx and wrapped around the trachea
Structure: Consists sacs called thyroid follicles which are lined with follicular cells (secrete T3 &T4) that surround a protein rich collar
Parafollicular C cells (Secrete calcitonin) are found between follicles
Hormones/Effects:
T3 & T4 increase basal metabolic rate.
Calcitonin increases osteoblast activity & raises blood calcium levels. Promotes calcium deposition and bone formation
3.3 Parathyroid gland; state its location, describe its structure, list hormones produced & their effects
Location: in the neck and embedded in the posterior surface of the thyroid gland
Consists of four ovoid glands
Hormones/Effects: Parathyroid hormone in response to hypocalcaemia
Parathyroid hormone function:
Increase blood calcium levels
Increase osteoblast activity
Enhancing the reabsorption of Ca2+ and the secretion of phosphate by the kidneys
3.4 Adrenal glands; state their location, describe its structure, list hormones produced & their effects - Adrenal cortex Aldosterone
Aldosterone (Zona glomerulosa) -
regulate electrolyte excretion and intravascular volume
affects distal tubules and cortical collecting ducts of kidneys
increase sodium and reabsorption and potassium excretion
3.4 Adrenal glands; state their location, describe its structure, list hormones produced & their effects - Adrenal cortex Glucocorticoids
Glucocorticoids (Zona fasciculata) -
□ Stimulated by ACTH, glucocorticoids stimulate fat and protein catabolism
□ Stimulate gluconeogenesis
□ Increase blood glucose and fatty acid levels in the bloodstream
□ Glucose sparing effect
□ Supress immune system with long-term secretion
□ Anti-inflammatory effect & Generally helps the body adapt to stress
3.4 Adrenal glands; state their location, describe its structure, list hormones produced & their effects - Adrenal cortex Conadocorticoids
Conadocorticoids (Zona reticularis) -
Weak androgens such as dehydroepiandrosterone (DHEA)
Some oestradiol supplement that functions of the sex steroid produced by the gonads
3.4 Adrenal glands; state their location, describe its structure, list hormones produced & their effects - Adrenal medulla
Adrenaline & noradrenaline - (Fight or flight response)
□ Increase cardiac output
□ Dilation of blood vessels in heart, lungs, brain and muscles
□ Vasoconstriction in vessels of skin and viscera
□ Increase blood glucose
□ Increase RR and metabolism
□ Increase fatty acid metabolism from adipose tissue
3.5 The pancreatic islets; state their location, describe their structure, list hormones produced & their effects
Location: in the curve of the duodenum
• Endocrine portion of the pancreas
Hormones/Effects: Endocrine islets of Langerhans consists of three different cell types that secrete hormones:
Glucagon Function: (Alpha)
□ Secreted in response to low blood glucose
□ Increase blood glucose levels by using energy reserves
□ Stimulates glycogen breakdown to glucose
□ Stimulates breakdown of fats to free fatty acids
Insulin Function: (Beta)
□ Secreted in response to high blood glucose
□ Increase glucose uptake and synthesis of energy stores
□ Also stimulates amino acid uptake and protein synthesis
□ Anabolic hormone
Somatostatin Function: (Delta)
□ Inhibits secretion of insulin and glucagon & Slows absorption of GIT.
3.6 The gonads; state their location, describe their structure, list hormones produced and their effects
Location: Testes and Ovaries
○ Testes:
paired oval glands located in the scrotum,
consists of microscopic seminiferous tubules that produce sperm
with interstitial cells, they produce testosterone.
○ Ovaries:
Paired oval bodies located in the female pelvic cavity Consist of follicles which surround egg cells
Produce the hormone oestradiol, progesterone, and inhibin.
Hormones/Effects: Testosterone, Oestradiol, Progesterone, and Inhibin:
○ Testosterone Function:
Develop male genitals and accessory sex organs
Development of secondar sex characteristics
Stimulate libido
○ Estrogen Function:
Regulates the female reproductive cycle
Stimulate female secondary sex characteristics
○ Progesterone Function:
Inhibits thickness of endometrium, pro-pregnancy hormone
○ Inhibin:
Supress FSH secretion
