pre exam 3 (part 2) Flashcards
1
Q
action potential generation at the AIS
A
- AIS has high density of voltage-gated ion channels
- if threshold potential reached, tons of Na+ let in from these
2
Q
action potential propagation along the axon
A
- # of action potentials must be conserved (same at AIS and at axon terminal)
- voltage gated ion channels along the axon restore the action potential as it’s conducted
- myelination increases speed of conduction
3
Q
unmyelinated vs myelinated axons
A
unmyelinated
- came first, common in autonomic parts of the brain
- more Na+ and K+ channels because current is lost (and voltage must be conserved)
myelinated
- myelinated by oligodendryoctes
- Na+ and K+ channels only at nodes of ranvier
- 4-10x faster
*15k miles of axons in the body!
4
Q
demyelination
A
- demyelination causes loss of action potentials in nerves and circuit disfunction
- many diseases result from demyelination, MS is common (antibodies against myelin-making protein)
5
Q
significance of Na+/K+ pump for membrane potential
A
- expressed in every cell
- pump is electrogenic–generates a negative electric potential in the cell (3 Na+ out, 2 K+ in)
- negative potential from pump powers membrane transport (Na+ diffuses in when channels open based on concentration AND electrical gradient)
6
Q
positive and negative feedback
A
positive
- positive feedback loops move you away from a set point
- few examples in bio, inherently unstable
negative
- negative feedback loops move you toward the set point
- allow control
7
Q
significance of the hypothalamus and pituitary gland
A
- major hubs of homeostatic control
- all the hormonal output is controlled by feedback loops
8
Q
respiration feedback loop
A
- lack of O2/increase in CO2
- peripheral/central chemoreceptors sense
- activate respiratory centers in medulla
- activate breathing muscles
- increase alveolar ventilation rate
9
Q
blood pressure regulation loop
A
- baroreceptors sense change in blood pressure
- medulla responds (sympathetic or parasympathetic)
- HR and SV change, altering blood flow
- blood pressure is corrected to set point
10
Q
role of thyroxine
A
- thyroxine regulates metabolism in all cells
- sets the basal metabolic rate of the cell
11
Q
hypothalamus/anterior pituitary relationship
A
- anterior pituitary and 6 hormones that come out of it are regulated by releasing hormones from the hypothalamus
- each pituitary hormone has a unique releasing or inhibiting hormone from the hypothalamus
- hormones released by different cell types
12
Q
regulation of thyroxine
A
- 2 forms of thyroid hormones: thyroxine (T4) and triiodothyronine (T3)
- low levels of T3/4 signal release of thyrotropin releasing hormone (TRH) from hypothalamus
- causes release of thyroid stimulating hormone (TSH) from anterior pituitary
- TSH binds to thyroid stimulating hormone receptor (TSHR), releasing T3 and T4
13
Q
normal blood glucose levels
A
70-140 mg/dl
14
Q
T3 vs T4
A
- T3 (triiodothyronine) is more biologically active than T4 (thyroxine)
- after transporters bring T3/4 into cell, T4 converted into T3
- deiodinases D1 and D2 remove an iodine from T4 to make T3
15
Q
function of T3 in the cell
A
- T3 is a global transcription factor (increases metabolism in all cells)
- binds to its hormone receptor element on DNA (TRE)
- binding to different genes (some enhanced and some inhibited) has a net effect of increasing metabolism
