Human Physiology Introduction

1) some way to measure the regulated variable

2) some way to alter (effect) the regulated variable

3) a way of linking measurement and regulation

Positive feedback is difficult to regulate until some massive event occurs

(i.e. - oxytocin in childbirth or luetinizing hormone during ovulation)

Water is a DIPOLE

Polarity makes water a good solvent for ions

Bonds btw adjacent water molecules are LABILE and TRANSIENT.

Bonds are made and broken in a fraction of a second and these loose bonds give water unusually high surface tension and cohesiveness.

• Water is a great solvent for IONS.
• (i.e. - NaCl)

*remember "like dissolves like"

SELECTIVE dissolving

• Water dissolves certain organomolecules that do not dissociate into ions but do have polar properties.
• (i.e. - alcohols, sugars, hormones)

High HEAT capacity

This means water is difficult to heat and, since the body is mostly water, body temp remains relatively constant.

High latent heat of EVAPORATION

It takes a lot of energy to heat liquid water into vapor. This is why we sweat to lose heat and cool down.

Relatively INCOMPRESSIBLE

When a force is applied to it, it exerts nearly the same force.

This makes blood pressure possible.

Compounds containing both polar and non-polar groups or regions.

Lipids and steroids

The cell membrane has low permeability to POLAR substances like IONS, SUGARS, INSULIN and greater permeability to NON-POLAR substances like STEROID HORMONES, CO₂ , O₂

Phospholipids have a charged head and two uncharged tails making them amphipathic.

• O <--charged head
• l l
• l l <--uncharged tails

A type of lipid found in cellular menbranes and mostly in the brain

1) Phosphoglycerides - have glycerol backbone

2) Sphingolipids - have sphingosine backbone

3) Sterols - nonpolar, slightly water soluble (i.e. cholesterol)

Cell membranes contain both LIPIDS and PROTEINS

Peripheral - associated with the surface of the membrane (i.e. G-protein)

Integral - span the membrane

1) Passive transport pore and channels

2) Active transport pumps (Na/K pump)

3) Membrane lined enzymes

4) Receptors

Maintenance of relatively constant conditions within the internal environment of the body

The response of a system goes in the opposite direction of the changes that it set in motion.

(INHIBITORY)

The response of a system goes in the same direction of the changes that it set in motion.

A barrier separating a cell from ECF consisting of phospholipids, proteins, and cholesterols.

A sphere formed by a single layer of phospholipids with the polar region facing the aqueous environment and the nonpolar regions facing inward.

• 1) Passive transport pores and channels
• 2) Active transport pumps
• 3) Membrane lined enzymes
• 4)Receptors

Fats with a glycerol backbone containing a phosphorous group

Molecules within the membrane exchange places with adjacent molecules 10⁷ times per second, but rarely change with molecules from the other side of the bilayer. Fluidity is important for receptor function and placement.