LO 10 Flashcards
(61 cards)
Describe the endocrine system
- Second greatest controlling system of the body
- Performs the same general functions as the nervous system, e.g: communication and control
- Functions carried out by specialized glands that secrete chemicals called hormones
What are the two types of glands in the body?
- Exocrine - Secrete hormones through ducts (e.g. sweat glands, salivary glands)
- Endocrine - ‘ductless’ (secret hormones directly into the blood); Produce/secrete hormones as needed (generally do not store hormones)
Describe the path of hormones in the endocrine system
- Endocrine glands secrete their hormones into intercellular spaces
- Hormones then diffuse into the blood which transports them throughout the body
- Individual hormones have specific ‘target’ cells that they affect
- Result is a slower, long-lasting result (as opposed to nervous system, which is fast)
What are the body functions that hormones regulate?
- Metabolism
- Growth & development
- Calcium and blood sugar balance
- Reproduction
What are the two major classes of hormones?
- Non-steroidal (amino acid/protein)
- Steroidal (lipid or fat-soluble)
How do steroidal and non-steroidal hormones interact with/affect their target cells?
- Non-steroidal 🡪 second messenger mechanism
- Steroidal 🡪 Hormone-receptor complex mechanism
Describe the second messenger system
- Non-steroidal hormones are protein hormones
- Proteins cannot penetrate cell membranes without the help of a carrier, or messenger
- The non-steroidal protein hormone is referred to as the ‘first messenger’ , which binds to specific receptors in the target cell’s membrane
- This leads to chemical reactions that activate substances in the cell called ‘second messengers’
- Second messengers are what affect the cell’s activities
- cAMP is an example of a second messenger
Describe the mechanism of steroid hormone action
- Small, lipid-soluble molecules
- Can easily pass through the target cell’s membrane
- Move through the cytoplasm to the nucleus
- Bind to receptors in the nucleus to create a ‘hormone-receptor complex’
- The complex acts on the cell’s DNA 🡪affects cellular activity e.g. production of new proteins or enzymes that will affect the target cell
Describe the regulation of hormone secretion
- Negative feedback - Mechanisms that reverse the direction of a change in a physiologic system. e.g. insulin and blood sugar balance
- Positive feedback - (Uncommon) mechanisms that amplify physiologic changes, e.g. oxytocin & labour contractions
Describe prostaglandins (tissue hormones)
- Powerful substances found in a wide variety of body tissues (not typical hormones!)
- Lipid/fatty-acid based
- Often produced in a tissue and diffuse only a short distance to act on cells in that tissue (not transported in the blood to distant tissues organs as ‘regular’ endocrine hormones are)
- Influence many body functions, e.g. respiration, BP, G-I secretions, inflammation, reproduction
What are the 10 glands of the endocrine system?
- Pituitary gland
- Hypothalamus
- Thyroid gland
- Parathyroid gland
- Adrenal glands
- Pancreas
- Gonads (testes/ovaries)
- Thymus gland
- Placenta (temporary)
- Pineal gland
Describe the pituitary gland
- Powerful, pea-sized gland
- Produces or stores the greatest variety of hormones
- Attached to the brain at the hypothalamus
- Composed of 2 glands - Anterior pituitary gland (adenohypophysis); Posterior pituitary gland (neurohypophysis)
Which hormones does the anterior pituitary gland secrete?
- Thyroid-stimulating hormone (TSH)*
- Adrenocorticotropic hormone (ACTH)*
- Follicle-stimulating hormone (FSH)*
- Luteinizing hormone (LH)*
- Melanocyte-stimulating hormone (MSH)
- Growth hormone (GH)
- Prolactin hormone (PH)
- Tropic hormones: stimulate another endocrine gland to grow and secrete its hormones
Describe the function of TSH (Thyroid-stimulating hormone)
- Acts on thyroid gland
- Stimulates growth of the thyroid gland
- Stimulates thyroid to secrete thyroid hormone
Describe the function of ACTH (Adrenocorticotropic hormone )
- Acts on adrenal cortex
- Stimulates growth of the adrenal cortex
- Stimulates adrenal cortex to secrete its hormones (mainly cortisol)
Describe the function of FSH (Follicle-stimulating hormone )
- Acts on male and female gonads (testes/ovaries)
- In females - Initiates growth of ovarian follicles each month in the ovary and stimulates one or more follicles to develop to the stage of maturity and ovulation; Stimulates estrogen secretion by developing follicles
- In males - stimulates sperm production
Describe the function of LH (Luteinizing hormone) – ‘ovulating hormone’
- Acts with FSH on male & female gonads
- Stimulates estrogen secretion and follicle growth to maturity
- Causes ovulation (rupture of mature follilce 🡪 🡪releases ripe ovum)
- Stimulates the formation of the corpus luteum in the ruptured follicle (luteinization)
- Stimulates progesterone secretion by corpus luteum
- Stimulates testes to secrete testosterone in the male
Describe the function of MSH (Melanocyte-stimulating hormone )
- Acts on the adrenal cortex and melanocytes (in skin)
- Regulates function of adrenal cortex
- Causes rapid increase in the synthesis and spread of melanin in the skin
Describe the function of GH (Growth Hormone)
- Acts on all organs/tissues (esp. muscle & bone)
- Accelerates protein anabolism 🡪 tissue growth
- Accelerates fat catabolism
Slows glucose catabolism 🡪 🡪hyperglycemia
Describe the function of Prolactin or lactogenic hormone
- Stimulates breast development during pregnancy
- Stimulates secretion of breast milk after the delivery of the baby
The pituitary has a physical connection to the brain via the _________
Hypothalamus
Neurons run through the pituitary stalk connecting the two structures
Describe the function of the posterior pituitary gland
- Neuron cell bodies in the hypothalamus produce two hormones: ADH & oxytocin
- ADH & oxytocin travel to the posterior pituitary gland along the axons of the neurons that run from the hypothalamus to the posterior pituitary gland
- Release of these 2 hormones is controlled by nervous stimulation
Describe the function of Antidiuretic hormone (ADH)
- Targets kidneys
- Accelerates water absorption from urine in the kidney tubules into the blood 🡪decreases urine secretion (🡪water retention)
Describe the function of Oxytocin
- Targets uterus and breast tissue
- Stimulates the pregnant uterus to contract, initiating labour 🡪 oxytocin!
- Causes glandular cells of the breast to release milk into ducts (‘milk let-down)
- Breastfeeding 🡪oxytocin!