Lab Exam 2 Flashcards
Metabolism
sum of all chemical reactions that take place in the body
Hormone
a regulatory signaling molecule created by endocrine organs & transported through the blood to stimulate a response
Target Cell
the cell that responds to the chemical messenger
Receptor
the proteins on a target cell that recognize & bind a chemical messenger
3 structural classes of hormones
-amines
-peptides
-steroids
Amines
derived from amino acids & contain amine groups
Examples of amines
dopamine, norepi, epi, thyroid hormones, histamine
Peptides
chains of 50 or less amino acids
Steroids
synthesized on demand from cholesterol, immediate release due to hydrophobic characteristics
G protein coupled receptor (GPCR)
- 1st messenger binds to receptor & activates G protein
- G protein releases alpha subunit, GDP to GTP, alpha subunit binds to adenylate cyclase
- Adenylate cyclase turns ATP to cAMP
- cAMP activates protein kinase A
- protein kinase A phosphorylates protein to alter activity using ATP
- cell response triggered
Enzyme linked receptor
- messenger binds to receptor causing change in conformation
- tyrosine kinase activated
- tyrosine kinase phosphorylates intracellular protein
- cell response triggered
Channel linked receptor
receptor & ion channel are the same protein
Thyroid Axis
- hypothalamus releases TRH to activate pituitary gland
- pituitary gland releases TSH to activate thyroid
- thyroid releases T4 & T3
How does thyroid hormone affect metabolism?
increases Na/K pump
What are the units for BMR?
ml O2/kg/hr
How can BMR be affected clinically?
-BMR will be low if TRH or TSH levels are low
-Thyroxine injections can increase BMR
Hypophysectomy
removal of pituitary gland
Thyroidectomy
removal of thyroid gland
How does estrogen affect bone density?
-it stimulate bone growth & density & protects against osteoporosis
Which hormone replacement therapies would be used to counteract osteoporosis?
estrogen & calcitonin injections
Normal T score range
+1 to -0.99
Osteopenia T score range
-1 to -2.49
Osteoporosis T score range
-2.5 or lower
When is insulin released?
secreted by beta cells in the pancreas in response to high blood glucose levels
When is glucagon released?
secreted by alpha cells in the pancreas in response to low blood glucose levels
What are the effects of alloxan?
Induces diabetes mellitus, ROS destroys pancreatic beta cells & causes hyperglycemia due to no release of insulin
HPA Axis
- hypothalamus releases CRH to activate anterior pituitary
- anterior pituitary release ACTH to activate adrenal cortex
- adrenal cortex releases cortisol
Cushing’s Syndrome
high cortisol level, low ACTH levels
primary endocrine disorder
Cushing’s Disease
high levels of cortisol & ACTH
secondary endocrine disorder
Addison’s Disease
low cortisol level, high ACTH level
primary endocrine disorder
Primary endocrine disorders
abnormality in the endocrine organ
Secondary endocrine disorders
abnormality in the hormone
3 parts of a neuron
soma, dendrites, axon
Excitability
the ability to respond to stimuli & convert them into action potentials
Conductivity
capability of transmitting an action potential along the length of the cell
Where on the neuron does an action potential occur?
axon
Electrochemical gradient
sum of the electrical and chemical gradients acting on an ion
Equilibrium potential
the membrane potential when the electrical driving force is equal in magnitude & opposite in direction to the chemical driving force giving an electrochemical driving force of zero
Formula for equilibrium potential
61/charge of ion times log (extracellular fluid/ intracellular fluid)
ICF concentration for K+
140
ECF concentration for K+
4
ICF concentration for Na+
15
ECF concentration for Na+
145
ICF concentration for Ca2+
less than 0.001
ECF concentration for Ca2+
1.8
Subthreshold stimulus
stimulus that is too small in magnitude to produce an action potential
Depolarization
voltage gated Na+ channels are open, brings membrane back to threshold (0)
Hyperpolarization
K+ channels open & K+ moves out of the cell, membrane potential becomes more negative
Threshold Stimulus
minimum intensity required from a stimulus to produce a response
Absolute refractory period
period where all Na+ channels are closed & the cell cannot be stimulated at all
Relative refractory period
period where some Na+ channels reset to open (can pump some Na+ into the cell), a stronger stimulus is needed to stimulate cell
What are the effects of nerve size & myelination on conduction velocity?
myelination increases the rate of an action potential
a large diameter increases the rate of an action potential
Tetrodotoxin (TTX)
blocks voltage gated Na+ channels that are needed to produce an action potential
Curare
block acetylcholine receptor
Lidocaine
blocks Na+ flux across a membrane
Ether
opens K+ ion channels causing the neuron to become hyperpolarized
Epimysium
surrounds the entire muscle
Perimysium
surrounds the fascicle
Endomysium
surrounds individual muscle fibers