Module 1 Flashcards
What are the primary organs of the endocrine system?
- hypothalamus
- pituitary gland
- thyroid & parathyroid gland
- adrenal glands
- pancreas
- gonads
- placenta
What does the endocrine system do?
- coordinate and integrate cellular activity throughout the body to maintain homeostasis
How does the endocrine system produce an effect on the body?
- chemical messengers (hormones) use the circulatory pathways
What are the functions of the endocrine system?
- homeostasis
- storage and utilization of energy
- regulation or growth, development, and reproduction
- response to environmental stimuli
Compared to the nervous system, the endocrine system speed of response is _______ but has a _______ response time.
- slower
- prolonged
T/F: Endocrine system response is more diffuse than the nervous system response.
- True
What are the three general components of the endocrine system?
- endocrine glands
- target organs
- hormones
What is a ductless gland that secretes hormones into blood?
- endocrine gland
What is the organ that contains cells with receptors that have hormone specific receptors?
- target organ
What are chemical messengers released by one cell and exert a biological action on a target cell?
- hormones
Describe the action of a hormone
- a single hormone can facilitate multiple effects
OR - many hormones collectivly produce a single effect
How is it possible for a single hormone to produce multiple effects?
- different receptor types
Why does the body have the ability to create one effect with many hormones?
- protective mechanism
What are the types of hormone signaling?
- endocrine
- paracrine
- autocrine
- intracrine
Describe the MOA of endocrine signaling
- hormones travel through blood stream to reach distant target tissue
Describe the MOA of paracrine signaling
- hormones release and act locally on the neighboring cells
Describe the MOA of autocrine signaling
- hormone is released by a cell then acts on the same cell that released it
Describe the MOA of intracrine signaling
- hormone produced in a cell and acts within the cell itself
How are hormone secretions regulated?
- negative feedback
- positive feedback
Which is more common, negative or positive feedback?
- negative
Describe how negative feedback regulates hormone secretion
- hormone action directly or indirectly inhibits further release of that hormone
Describe how positive feedback regulates hormone secretion
- hormone action directly of indirectly stimulates further release of that hormone
What are the two types of negative feedback loops?
- short (one or two steps)
- long (many steps)
What is a variation on the negative feedback loop?
- increasing levels of hormone stimulate the hormones inhibiting factor
How is a positive feedback loop terminated?
- outside stimulus
How are the types of hormones classified?
- derivative content
- solubility
What are the derivative content types of hormone classifications?
- a.a.
- peptide/protein
- steroid
- fatty acid
What are the solubility types of hormone classifications?
- lipid soluble, water insoluble (lipophilic, hydrophobic)
- water soluble, lipid insoluble (hydrophilic, lypophobic)
What types of hormones are lipophilic?
- steroid
- thyroid
What is the precursor for all steroid hormones?
- cholesterol
How are lipophilic hormones circulated in the plasma?
- bound to a protein carrier
What types of hormones are hydrophilic?
- most
How are hydrophilic hormones circulated in the plasma?
- ‘free’
Which has a shorter half life, lipophilic or hydrophilic hormones?
- hydrophilic
- free and easily broken down
What are the cellular mechanisms of hormonal action?
- direct binding of hormone receptors
- signal transduction
Where are hormone receptors located?
- cell membrane or within the cell
What do the number of receptors reflect?
- local or systemic conditions
What is up-regulation?
- [low hormone] will increase the number of receptors
What is the net result of up-regulation?
- increases sensitivity
What is down-regulation?
- [high hormone] will decrease the number of receptors
What is the net result of down-regulation?
- decreased sensitivitity
T/F: Receptor number is a fixed quantity
- False, dynamic & continuous turnover
Healthy receptors are adapting to make physiology _____ efficient while unhealthy receptors are making physiology _____ efficient.
- more
- less
Define signal transduction
- process by which hormones are communicated into the cell
What are the two types of signal transduction hormones?
- primary
- secondary
What is the type of signal transduction for lipophilic hormones?
- primary
What is the type of signals transduction for hydrophilic hormones?
- secondary
Define primary messenger as a type of signal transduction
- hormone itself enters the cell and mediates cell function
Define secondary messenger as a type of signal transduction
- messenger “link” between primary messenger and inside of the cell
How does a secondary messenger produce its action?
- hormone attaches to target receptor on cell membrane
- receptor stimulates interior cascade to produce desired physiologic action
Why do hydrophilic hormones require a secondary messenger mechanism for signaling?
- water soluble hormone can’t cross membrane
- needs messenger to communicate to interior structures
What is the Hypothalamic-Pituitary Axis (HPA)?
- critical signaling pathway for the endocrine system
What are the two sections of the HPA?
- anterior pituitary
- posterior pituitary
Describe the movement of hormones in the anterior pituitary
- hypothalamus releases “pituitary releasing hormones”
- releasing hormones descend via hypophyseal portal system
- releasing hormones either stimulate or inhibit release of pituitary hormone
What is the hypophyseal portal system?
- capillaries in hypothalamus communicate with pituitary capillaries before entering the venous system
Describe the movement of hormones in the posterior pituitary
- hypothalamic neurons produce hormones
- released via hypothalamus neuron directly into post. pit and enter blood
What are the two posterior pituitary hormones?
- ADH
- oxytocin
What is the function of the hypothalamus?
- ‘links’ CNS to endocrine system
Where is the hypothalamus located?
- diencephalon of CNS
What are the hormones that are released from the hypothalamus that control the ant. pit?
- The SUBmarine DA Prefers SOMe CRunchy Green growth hormone.
- TRH (thyrotropin releasing hormone)
- Substance-P
- DA
- PRF (prolactin releasing factor)
- Somatostatin (SRIF - somatotropin release-inhibiting factor)
- CRH (corticotropin releasing hormone)
- GnRH (gonadotropin releasing hormone)
- GHRH (growth hormone releasing hormone)
What is TRH and its action in the ant. pit?
- thyrotropin releasing hormone
- stimulates release of TSH (thyroid stimulating hormone)
What is GnRH and its action in the ant. pit?
- gonadotropin releasing hormone
- stimulates the release of LH (luteinizing hormone) and FHS (follicle stimulating hormone)
What is somatostatin and its action in the ant. pit?
- SRIF - somatotropin release-inhibiting factor
- inhibits release of GH (somatotropin) and TSH
What is GHRH and its action in the ant. pit?
- growth hormone releasing hormone
- stimulates the release of GH
What is CRH and its action in the ant. pit?
- corticotropin releasing hormone
- stimulates release of ACTH (adrenocorticotropic hormone) and B-endorphin