Endocrinology Part 1 (8.1) Flashcards
1
Q
What are the endocrine system and nervous system known as in the body?
A
- two major control systems of the vertebrate body
2
Q
What can homeostasis be defined as?
A
- monitoring & coordinating of internal environment
- make appropriate adaptive changes
- regulate growth, development, senescence
- enables to respond + adapt to changes in external environment e.g. temperature change, food intake
3
Q
What is the nervous system?
A
- network of neurons
- transmit signals along dedicated pathways
4
Q
What is the endocrine system?
A
- hormones are chemical signaling molecules that travel through the blood + reach every part of the body
- only target cells have receptors that allows them to respond
5
Q
What do organisms use homeostasis for?
A
- to maintain a “steady state”
- to maintain an internal balance regardless of external environment
- e.g. body temp, blood, pH + glucose conc.
- maintained at a constant level
6
Q
How does homeostasis work?
A
- moderate changes in an internal environment
- fluctuations above/below a set point = stimulus
- detected by a sensor and trigger an immune response
- response returns variable to a set point
7
Q
What is a hormone?
A
- chemical messenger produced and secreted by a specialised endocrine gland, transported in the bloodstream
- to a distant target, organ/cell where it elicits a physiological response
8
Q
What are the 3 different classes of hormones?
A
- proteins/peptides, *growth hormone
- cholesterol derivatives, *steroids, vitamin D
- modified amino acids, *adrenaline, thyroid hormones
9
Q
What happens in target cell recognition? - Part 2
A
- non lipid-soluble hormones e.g. protein hormones - cannot diffuse through the phospholipid layers
- action upon target cells must be carried out indirectly
- binding to an extra-cellular receptor + this triggers an intracellular signalling cascade - “second messenger system”
10
Q
What are the stages of the second messenger model?
A
- the hormone itself = the first messenger
- binds to specific receptors on the cell-surface membrane of target cells
- forms a hormone complex
- activates an enzyme within the cell
- production of a chemical that acts as a second messaenger
11
Q
What happens in target cell recognition?
A
- lipid- soluble hormones (e.g. steroid hormones) diffuse through the phospholipid bilayer
- bind to an intracellular receptor that directly activates target molecules
(changes in gene expression)
12
Q
What are some hormones actions?
A
- affect growth, development, metabolic activity & function of tissues
- may be stimulatory/inhibitory
- may act on several tissues/ just one specific target tissue - major difference between endocrine & nervous system
- responsive tissues must have specific receptors for that hormone
13
Q
What are circulating hormone levels influenced by?
A
- rate of secretion, *by endocrine gland
- rate of metabolism, *by target tissue, blood, liver, kidney
- serum binding proteins, *transport in blood - solubility tissue etc.
14
Q
What regulates hormone secretion?
A
- physiological changes e.g. blood glucose and insulin
- by endogenous rhythms, e.g. infradian cycles
- by feedback mechanisms, e.g. negative feedback, which maintain homeostasis
15
Q
What does endogenous mean?
A
“built in”
