Unit 2: The Endocrine System Flashcards
Homeostasis:
-balance within the body.
The endocrine system works in conjunction with the nervous system to:
-maintain homeostasis within the body.
Regulation of hormones:
•hormone levels are regulated through negative feedback mechanisms.
•the accumulation of a certain biochemical switches off hormone synthesis to maintain homeostasis.
•prevents small changes from becoming too large.
•designed to resist change.
•Ex. Blood glucose levels:
-eat a large meal—> increased blood sugar levels—> stimulates insulin production—> stimulates cells to take up glucose—> blood glucose levels drop and insulin production is not stimulated further.
Positive feedback loop:
•positive feedback systems reinforce change (a small effect is amplified).
•allows a discrete physiological event to be accomplished rapidly.
•once the event is accomplished, the feedback system stops.
•example: labour and birth.
The endocrine system is run by NEGATIVE FEEDBACK LOOPS.
Nervous vs endocrine system (change):
-NS: rapid response to change.
-ES: sustained response to change.
Nervous vs endocrine system (signals):
-NS: electrical/chemical signals.
-ES: hormonal signals.
Nervous vs endocrine system (signals relayed):
-NS: signals relayed through neurons.
-ES: signals relayed through the bloodstream.
Nervous vs endocrine system (affects):
-NS: affects specific locations.
-ES: affects whole-body functioning.
Key glands of the endocrine system:
-pineal gland, hypothalamus, pituitary gland, thyroid gland, parathyroid gland, thymus, adrenal gland, pancreas, ovary, testis.
•each gland is responsible for secreting specific hormones which, in turn, target and affect the function of specific tissues/organs.
Key terms:
•hyper (prefix): more than (ie. hyper-secretion).
•hypo (prefix): less than (ie. hypo-secretion).
•concentrated: a lot of solute in a given solution.
•dilute: little solute in a given solution.
Hypothalamus & pituitary:
•hypothalamus regulates the pituitary, via nerves and hormones.
•hypothalamus produces releasing hormones (factors) that stimulate the anterior pituitary gland to release a stored hormone.
•the pituitary is often called the “master gland” as it is responsible for releasing a number of hormones involved in critical functions.
•many hormones released from hypothalamus & pituitary are tropic hormones, meaning they stimulate other glands to release other hormones.
Anterior:
-front.
Posterior:
-back.
Posterior pituitary:
-stores but does not produce hormones (oxytocin and ADH). Connected to hypothalamus via nerves.
Anterior pituitary:
-synthesizes hGH, prolactin, TSH, ACTH, FSH, and LH. Stimulated by hypothalamus with hormones.
-(a bit slower compared to posterior).
Thyroid & parathyroid glands:
-thyroid—> produces thyroxine, calcitonin.
-parathyroid—> produces parathyroid hormone.
Adrenal cortex & adrenal medulla:
-different layers of the adrenal glands; located on top of the kidneys.
•adrenal medulla—> produces epinephrine and norepinephrine, involved in the short-term stress response.
•adrenal cortex—> produces cortisol and aldosterone, involved in the long-term stress response.
Medulla:
-middle.
Pancreas:
•specialized clusters of cells (known as islets of Langerhans) secrete hormones into the bloodstream responsible for glucose regulation.
•beta cells secrete insulin, alpha cells secrete glucagon.
Hormones:
-hormones interact with receptor proteins specific to their target tissue, including a change, which leads to a cascade of events within each cell.
•two types of hormones, classified by the way they interact with target cells:
1. Water soluble hormones (proteins, peptides, and amino acid derivatives) cannot cross the lipid membrane, and thus interact with cells by binding to external receptor cites.
2. Fat soluble hormones (steroids) are able to diffuse across the lipid membrane, and thus interact with cells by binding to receptor sites within the cytoplasm.
