Lecture 5 Flashcards
What is the importance of the endocrine system?
- chemical regulation and communicaton uses endocrine/nervous systems
- second great control system
- coordinates w NS and directs activity of bodies cells
- more slowly acting and uses chemical messengers called hormones
What are the major processes that the endocrine system controls?
- behaviour
- repro
- growth and development
- maintaining electrolyte, water and nutrient balance of blood
- regulating cellular metabolism and energy balance
- defenses against stressors
What is the relation of the endocrine system to stress?
most chronic and prolonged responses to stress events are the result of the endocrine axes
What are the four main endocrine axes?
- adreno-cortical axis
- somatotropic axis
- thyroid axis
- posterior pituitary axis
What are the hormonal classifications?
amino acid based molecules
steroids
lipids
What is the basis of hormone action?
blood borne hormones circulate throughout the body
but have action on certain tissue cells or organs (target cells/organs)
Is hormone action specific?
yes
What are the general steps to a hormonal action?
reception of signal: hormone binds to specific receptor protein
signal transduction
response: change in cell behaviour
Can one hormone bind to a variety of receptors in various target cells?
yes
How does a rhythmic release levels rising and falling over again occur with hormonal stimulation?
as the final hormones increase they feed back to inhibit release of initial stimulating hormone
When does neural stimuli cause hormone release?
in isolated cases only
Explain the negative feedback loop
some internal or external stimulus triggers hormone secretion-> leads to increase level of hormones in the body-> the rising levels inhibit further hormone release
What is the difference between endocrine and exocrine glands?
Endocrine glands:
- ductless
- release hormones into the blood or lymph
- e.g. hypothalamus, pituitary, thyroid, adrenal
Exocrine glands:
- have ducts
- release products at the bodies surface or into cavities
- e.g. pancreas, gonads
What is the endocrine action of the hypothalamus?
- receives information from nerves
- sends nervous and endocrin signals
- uses pituitary gland to relay directions to other glands
- post pit: nervous tissue
- ant pit: endocrine cells
What is the function of the posterior pituitary?
- acts as storage for hormones produced in hypothalamus
- releases them into blood stream
- oxytocin: during parturition and lactation
- ADH: inhibits or prevents urine volume production = blood volume increases
What is the function of the anterior pituitary?
- produces and releases six hormones in total
- GH
- prolactin
- ACTH
- TSH
- FSH
- LH
What is the adrenal gland structure?
cortex (glandular)
medulla (neural)
- medulla is central and is surrounded by cortex
What are the three layers of the adrenal cortex?
Mineralocorticoid secreting area
glucocorticoid secreting area
sex hormone secreting area
What does the adrenal medulla develop from?
knot of nervous tissue
What is the adrenal medulla stimulated by?
sympathetic NS
What are the two hormones released from the adrenal medulla?
catecholamines
- epinephrine (adrenaline)
- norepinephrine (noradrenaline)
- responsible for fight or flight response
What is the function of the thyroid gland?
- makes two hormones
- Thyroid hormone: T3 (triiodothyronine) and T4 (thyroxine)
- calcitonin
