Lecture 25 Flashcards
(24 cards)
What is blood glucose important for, and what are the normal levels? (fasting and non-fasting)
- for ATP production
- 3.5-6 mmol/L fasting
- 3.5-8 mmol/L non-fasting
What is sodium important for, and what are the normal levels?
- for AP generation and ECF volume
- 135-145 mmol/L
What is calcium important for and what are the normal levels?
- for structure, neural transmission, muscle contraction, blood clotting, enzyme function
- 2.2-2.6 mmol/L
What is potassium important for and what are the normal levels?
- resting membrane potential determinant, nerve and muscle function
- 3.5-5 mmol/L
What is ECF osmolarity important for and what are the normal levels?
- maintain cell volume
- 275-300 mosmol/L
What is a regulated variable for homeostasis?
Is what variable system senses and tries to keep stable
What is set point?
The target value for the variable
What is the reference range?
Values of the regulated variable within normal limits
What is the difference between inter-individual and intra-individual variation?
- inter=variation between individuals
- intra=fluctuation within individual
What are the components of a negative feedback loop?
- sensors, monitors variable + detects deviation
- control centre/integrator, compares variable’s actual value to set-point
- communication pathways, sends signals to effectors from control centre
- effectors=oppose change and restore to set-point
What is positive feedback? Why is it useful and what are 2 examples?
- moves variable further away from set point
- less common
- useful when process needs to be driven to completion
- e.g blood clotting, child birth
What is feed forward response?
- detection or anticipation of conditions that could disrupt homeostasis
- e.g shivering, putting more layers on
What makes the endocrine system different from the nervous system (basically what is the endocrine system idk how to word this question)?
- circulating hormones
- hormones bind to membrane or intracellular receptors of target cells
- slower, but more widespread and lasts longer
What are paracines and autocrines?
- local hormones
- paracrines = act on nearby cells
- autocrines = acts on cell that secreted them
What are amino acid derivatives with examples?
- synthesised by modifying particular amino acids
- tyrosine > catecholamines
- tyrosine > thyroid hormone
- Tryptophan > serotonin and melatonin
- Histadine > histamine
What are peptide hormones?
- chains of 3 to 49 amino
acids - e.g ADH
What are protein hormones?
- chains of 50 to 200 amino
acids - e.g hGH, insulin
- if carb group = glycoprotein hormone
How are protein and peptide hormones synthesized?
- 1st as larger preprohormones that are not biologically active
- Cleaved to form smaller prohormones in ER
- Packaged into secretory vesicles in Golgi apparatus. During this process enzymes in
vesicles cleave prohormones to produced active hormone and inactive fragments
What are lipid derivatives?
- synthesized as needed
- steroid hormones derived from cholesterol (lipid soluble)
- Differences in the chemical groups attached at various sites on the 4 ring structure are responsible for producing diverse effects
- binds to transport proteins for movement around body
How would a free lipid soluble hormone do hormone stuff?
- ‘free’ lipid soluble hormone molecule diffuses from
blood to interstitial fluid and then through the lipid
bilayer of the plasma membrane - Hormone binds to receptors in the cytoplasm or nucleus.
- The activated receptor-hormone then binds to steroid
response elements (SRE) on DNA. - Gene expression altered by switching specific genes on
or off. - New mRNA is transcribed and moves to ribosomes
- mRNA translated on ribosomes to produce new proteins
» altered cell structure and/or function
How would a free thyroid hormone do hormone stuff?
1.’free’ thyroid hormone molecule diffuses
from blood to interstitial fluid and then through the lipid bilayer
2. Hormone binds to receptors in the mitochondria or nucleus.
- increased energy production
(mitochondria)
- Altered gene activation (nucleus) and
protein production on RER
>altered cell structure and/or
function
What is the action of water soluble hormones?
- integral membrane proteins at cell surface as not lipid soluble
- The hormone binds to these receptors acting as a ‘first messenger’
- The activated receptor (via its coupling to a G
protein) then causes the production of a ‘second
messenger’ inside the cell - 2nd messengers include cyclic AMP (cAMP), calcium ions
What are G-protein coupled receptors?
- transmembrane proteins
- Intracellular domains coupled to G-proteins that can bind guanosine nucleotides (GTP and GDP)
How do G-protein coupled receptors work?
- Binding of hormone to receptor (externally) activates G-protein (internally)
- G-protein subunit can then activate enzymes on inner cell membrane to produce a ‘second’ messenger or alter ion channels
- Second messengers or calcium-calmodulin can then switch on or off various enzymes within the cell
