The Endocrine System Flashcards
State the main function of the endocrine system.
Maintaining homeostasis by:
- Releasing chemical messengers (hormones) to change cell activity.
- Feedback - responding to stimuli by secreting more/less of a hormone to change original stimulus.
Describe how hormones are secreted and transported.
Hormones are chemical messengers that are secreted by specialised cells in a particular tissue, and transported via the blood.
May affect:
- All body cells
- Target cell
- Target organ
NOTE: The target cell/organ of the hormone has recpetors complimnetary to that of the hormone and vice versa !
Describe how hormones work in terms of saturation.
Hormones are only able to influence cells with a specific receptor which is complimentary to that of the hormone.
Saturation occurs when all receptors are occuiped/full, and therefore, any addition of more hormones will cease to have an affect on the target cell/organ.
NOTE: Think lock and key model !
State how hormones influence the function/action/activity of a cell.
A hormone works by changing the activities/quantities of proteins and enzymes produced by:
- Activating genes in the nucleus so proteins are produced
- Changing shape/structure of enzymes (on/off)
- Changing enzyme/protein production rate by inreasing/decreasing transcription and translation.
Define negative feedback.
A response which is opposite/reversing of the stimulus.
Describe the impact of over/under secretion of a hormone.
Over or under secretion of hormones will cause the body to function abnormally.
Describe hormone clearence.
Hormones must be turned off once the desired affect is achieved, which is done by breaking down hormone molecules.
Some are broken down in the target cell however this occurs most in the liver and kidneys.
NOTE: Excreted in bile or urine !
State and describe the 3 different types of hormones.
- Protein hormones = proteins
- Amine hormones = single amino acids
- steroid hormones = lipids
Describe how water soluble hormones are transported across the membrane.
- Protein + Amine hormones.
- Hydrophilic = cannot diffuse across the membrane.
- Attatch to receptor proteins in the membrane of the cell.
- Causes Secondary messenger substance to diffuse through the cell and activate a particular enzyme.
- Quick response, short lasting effects.
NOTE: can undergo gene expression then cytoplasmic response or go straight to cytoplasmic response !
Describe how lipid soluble hormones are transported across the membrane.
- Steroid hormones.
- Hydrophobic = can diffuse across the membrane.
- Combines with receptor inside the cell (nucleus or cytoplasm).
- Hormone receptor complex binds to section of gene activating/inhibiting transcription and protein synthesis (gene expression).
- Slow to have effect, long lasting.
NOTE: must undergo gene regulation prior to cytoplasmic response !
Distinguish between endocrine and exocrine glands.
Exocrine = secretes into ducts that carry the secretion to the surface/body cavities e.g. sweat + salivary glands.
Endocrine = secretes hormones into extracellular fluid which passes into capillaries to be transported across the body.
State the different endocrine glands.
- Pituitary
- Hypothalamus
- Pineal
- Thyroid
- Parathyroid
- Thymus
- Pancreas
- Adrenal Cortex
- Adrenal medulla
- Gondads (Ovaries + Testes)
Describe the diffeent hormones secreted by the anterior pituitary.
Growth Hormone
Target: Most cells.
Function: Stimulates general body growth + regulates aspects of metabolism such as protein synthesis/lysis.
Follicle Stimulating Hormone (FSH)
Target: Ovaries/Testes.
Function: Stimulates maturation of ova in follicles, secretion of oestrogen by ovaries + production of sperm in testes.
Luteinising Hormone (LH)
Target: Ovaries/Testes.
Function: Ovulation, formation of corpus luteum in females + secretion of testosterone in males.
Thyroid Stimulating hormone (TSH)
Target: Thyroid.
Function: Stimulates thyroid to produce/release thyroxine.
Adrenocorticotropic hormone
Target: Adrenal cortex.
Function: Stimulates adrenal cortex to secrete hormones, mainly cortisol.
Prolactin
Target: Breasts.
Function: Breast developement and milk production in females.
NOTE: FLAG TOP !
Describe the different hormones secreted by the posterior pituitary.
Antidiuretic Hormone
Target: Kidney.
Function: Increases premeability of distal convoluted tubule/collecting so water is reabsorbed back into blood + urine production decreases.
Oxytocin
Target: Breasts + Uterus.
Function: Causes contraction of smooth muscles of uterus during child birth + release of milk from breasts.
Describe the different hormones secreted by the hypothalamus.
Releasing/inhibiting factors
Target: Anterior pituitary.
Function:Controls the release of various hormones from anterior pituitary.
