ZOO502 Final Term Solved Papers Set 4

Zoo502

Donnan equilibrium 2

The phenomenon of unequal distribution of ions across the two sides of a differentially permeable membrane.

• Discovered by Frederick Donnan

in 1911.

• Given the name Donnan

equilibrium.

Definition

• “If diffusible solutes are separated

by a membrane that is freely permeable to water and electrolytes but totally impermeable to one species of ion, the diffusible solutes become unequally distributed between the two compartments”.

Example Take pure water in two compartments, separated by a membrane. Add KCl to one of them. KCl will ionize.

• Ions diffuse through the membrane until the conc. of K+ and Cl- becomes equal on both sides of the membrane.
• Now add a salt “KA” in I. It will produce K+ and A-.
• K+ is diffusible, but A- is not. So

Awill remain confined to I.

• K+ and Cl- quickly redistribute

to a new equilibrium.

• Presence of A- will cause an

unequal distribution of ions.

• K+ will be more conc. in I having Awhile

Clwill be less conc. in it.

Q Difference between epinephrine and nor epinephrine 2

Both are neurotransmitters, epinephrine is secreted by renal Medulla and norepinephrine by nervous system. Both are vasoconstrictor work during fight or flight. Checmically same except norepinephrine has additional methyle group. Norepinephrine acts on alpha-1, alpha-2, and beta-1 recpetors...works to raise the heart rate and modulate blood pressure Epinephrine acts on alpha-1, alpha-2, beta-1, AND beta-2..effective antihistamine and treatment for shock

Homeostasis and example 3

Homeostasis

• Walter Cannon (1929)
• The tendency of an

organism to maintain relative internal stability

Homeostasis—Definition

• To keep internal fluctuations in a

narrow range.

• The ability to protect internal

environment from the harms of fluctuations in external environment.

• Homeostasis does not mean to keep a

fixed internal environment. Homeostasis—Examples

• Homeostatic regulation of water
• Homeostatic regulation of

temperature

• Regulation of pH
• Regulation of glucose

concentration

• Regulation of osmotic pressure
• Regulation of oxygen level
• Regulation of ion conc.

Environmental Fluctuations

• Most habitats are quite hostile to

animal cells Examples

• Freshwater is more dilute
• Seawater is more salty
• Environmental temperature

may be too hot or too cold Need for Homeostatic Mechanisms

• Environmental fluctuations

are disruptive to the functions of cells, tissues and organs

• So, physiological regulatory

systems to maintain relatively stable conditions are a necessity.

Note on axon 5

Axon

• Long and thick process

with constant diameter.

• Arises from cell body.
• Lengths vary from few

mm to more than a meter.