The Endocrine System Flashcards
(22 cards)
how does the endocrine communicate
uses a chemical method of communication through hormones
- hormones released into the bloodstream
What is a hormone?
A hormone is a chemical transmitter/ messenger
transfers information and instructions from one set of cells to another
How are hormones released?
released in small amounts from endocrine glands, and is transported in the bloodstream to target organs or cells
what are target cells?
cell with a receptor that responds to the presence of a specific hormone
what are the endocrine glands and the hormones the secrete
- pineal gland = melatonin
- hypothalamus = controls release of hormones
- pituitary gland = various hormones
- thyroid gland = T3 & T4
- parathyroid gland = parathyroid hormone
- adrenal glands = cortiso, aldosterone, adrenaline
- pancreas = insulin and glucagon
- testes = testosterone
- ovaries = oestrogen and progesterone
What are the chemical classes of hormones
water soluble = cannot diffuse through the plasma membrane
lipid soluble = can diffuse through the plasma membrane
How do water soluble hormones travel through the blood and cause a response in target cells
- most circulate in the blood plasma in a free form
- free hormone diffuses out of the blood and into the extracellular fluid surrounding the target cell
- target cell receptor location on the surface of the plasma membrane (binds to surface)
- hormone reaction activates second messenger in the cytosol to trigger a response inside the cell
- response is specific to hormone (change is created)
how do lipid soluble hormones travel through the bloodstream to activate a response?
- most hormones travel through blood plasma bound to transport proteins
- some is free and unbound
- free hormone leaves blood and enters fluid around the cell
- target cell receptor in the nucleus or cytosol (pass through and bind)
- activates genes to trigger a response in target cell
What is the location of the hypothalamus and pituitary gland
Hypothalamus = region of the brain, anterior to the superior brainstem
Pituitary gland = connected inferiorly to the hypothalamus
What do the hypothalamus and pituitary gland do?
Hypothalamus:
- coordination centre for teh endocrine system
- directly controls activity of the pituitary gland
Pituitary gland:
- secretes hormones that regulate many body functions
What is the anatomy of the pituitary gland
posterior pituitary = direct extension of the hypothalamus
Anterior potuitary = attached to posterior potuitary
How does the posterior pituitary produce neurohormones (oxytocin and antidiuritic)
hormones are made in the hypothalamus
Stored in vesicles that travel down axons to the posterior pituitary
hormones are released into the blood via capillaries that surround the posterior pituitary
- (where they enter the bloodstream and travel to target organs)
what are the mechanisms of hormonal control from hypothalamus to anterior pituitary gland
hormone production (hypophysiotropic) from short axon neurons in hypothalamus
these hormones are released into the hypothalamic-hypophyseal portal systems (blood vesses connecting the hypothalamus to anterior pituitary)
the portal vessels deliver the hypophysiotropic hormones to anterior pituitary
What is the thyroid gland and thyroid hormone
thyroid = endocrine gland in the neck region
- plays a major role in metabolism growth and development
Thyroid hormones = T3, T4 are synthesised and stored in the thyroid gland
What is the process of thyroid hormone production
- thyrotrophin-releasing hormone (TRH) released from hypothalamus
Stimulates - thyroid-stimulating hormone (TSH) released from anterior pituitary
Stimulates - T3 & T4 released from the thyroid gland and enter into blood circulation
What is the function of the thyroid gland
- basal metabolism rate
- metabolism
- heat production
- regulation of tissue growth and development
- effects on cardiovascular system
What is the disruption of thyroid gland
hyperthyroidism = overactivtiy thyroid gland
- increase appetite and food intake, weight loss
- increse muscle weakness
- increase heat intolorance
- increase in mental alertness
- high heart palpitations
hypothyroidism = decreased thyroid hormone secretion
- low appetite = weight gain
- no energy
- cold intolerance
- slow speech/ reflexces
- slow heartreat
What is a feedback loop
a cycle of events in which the statis of a body conditioned is monitered, evaluated and changed
what are the 3 basic components of feedback loops and what do they do?
receptor (mointer): a body structure that moniters change in controlled condition and sends imput to control centre
control center (evaluator): evaluates input from receptors to generate output
Effectore (changer): recieves output from control centre and produces a response
What are the two types of feedback loops
Negative feedback = reverses/ opposes a change in a controlled condition
- regulates conditions in the body that remain fairly stable over long periods
Positive feedback = strengthens/ amplifies a change in one of the body’s controlled conditions
how does positive feedback work for oxytocin
oxytocin is a key driver during childbirth
1. initial stimulus = pushing against cervix activating stretch receptors
2. oxytocin is released = activating receptors to instruct oxytocin release
3. uterine contractions = stimulates muscles to contract pushing baby further
4. amplified contractions = cause more stretching of cervix, furthering release of oxytocin
5. positive feedback loop = creates a loop where each contraction leads to release and stronger contraction intensifying labour
how does the negative feedback loop work for the thyroid hormone
ensuring that when thyroid hormone levels are high the body decreases production…
- hypothalamus = the hypothalamus releases TRH, stimulates pituitary gland
- pituitary gland = PG releases TSH in response to TRH
- thyroid gland = TSH stimulates the thyroid gland to produce thyroid hormones (T3 & T4)
- T3 + T4 = these hormones travel through the body and reduce release of TRH annd TSH preventing excessive thyroid hormone.
