Membrane Potentials / Membrane Polarity Today’s Topics Membrane Potentials / Membrane Polarity What you must know first … ECF vs. ICF Normal distribution of electrolytes Permeabilities to Na+ and K+ RMP (resting mem. potential) Is the result of … The Cardinal Rule Altering RMP for Communication & Contraction Chemical Synapses Components of… & Events at chemical synapses

Neuromuscular Junctions (Chemical Synapses) - The Big Picture Fig 9.10

Neuromuscular Junctions (Chemical Synapses) - The Big Picture Focus Fig 9.2 Fig 9.10

Must know first… ECF vs. ICF (extracellular vs. intracellular) Normal distribution of Na+, K+, Ca++, & proteins(A-) Permeability to K+ vs. Na+ Composition not same but concentration and osmolality = Both fluids electrically neutral and isotonic

RMP (Resting Membrane Potential) Definition… All body cells have an RMP of -50mV to -100mV Some cells are “electrically excitable”… e.g. neurons and muscle To get a response we must alter RMPs

RMP is due to: Na+/K+ pump. Mem. is more permeable to K+ leaking out than Na+ leaking in Proteins (-) are pulled to inner surface of membrane

The Cardinal Rule about RMP: “The tendency for K+ to diffuse out of the cell is the #1 factor determining RMP… The greater the conc gradient of K+ the greater the tendency … The greater the permeability of the mem. to K+, the greater the tendency… The greater the tendency for K+ to diffuse out the more Pro- pulled to the inner surface of the mem. and therefore the greater the RMP (farther from 0) (more negative)

Altering RMP at Chemical Synapses Focus Fig 9.2 Altering RMP at Chemical Synapses Fig 9.10

Video: events at a chemical synapse

Video: events at a chemical synapse

Text version… Focus Fig 9.1

Q&A

Remember the Big Picture Focus Fig 9.2 Remember the Big Picture Fig 9.13

RMP – The cardinal rule explained Fig 3.14 RMP – The cardinal rule explained

Depolarization vs. Hyperpolarization Fig 11.9

An Action Potential traveling Fig 11.11

What if…?

Graded (Local) Potentials and Summation Only on neurons Strength varies with amount of NT released Strength declines/weakens as it travels Can be combined with others via summation

Q&A

Q&A

Q&A

Q&A

Inflammation, local

Inflammation, systemic

S&S of local Inflammation? -

Inflammation, local Fig 4.12 S&S are result of inflammatory chemicals, 3 big ones: Histamine (from Mast cells) a) Binds to H1 receptors on arterioles causing vasodilation -  BF… -  permeability… b) Escaped proteins cause… c) Tissue edema then causes …

Inflammation, local Fig 4.12 Kinins - Activated when cells damaged - Bind to chemoreceptors …

Inflammation, local Fig 4.12 Prostaglandins - Produced in and released from leukocytes (WBCs) - Bind to arterioles causing vasodilation… - Bind to chemoreceptors causing pain – ouch!

Clinical Applications Benadryl Aspirin & Ibuprofen Cortisone cream -Blocks the histamine (H1) receptor sites on arterioles -called an “antihistamine” - Inhibits the formation and/or action of prostaglandins Inhibits the release and/or action of a variety of inflammatory chemicals Fig 4.12

Tissue Repair: Organization, Regeneration, & Fibrosis Blood clot replaced w granulation tissue Capillaries “bud” and grow Fibroblasts synthesize collagen fibers … Macrophages “clean up the mess” Regeneration… Fibrosis… Regenerative Capabilities Well / Moderately well Skin, mucous mem., adipose, bone, smooth muscle Poorly Tendons, ligaments, cartilage, skeletal muscle None Cardiac muscle, neurons of the CNS

Fibrosis cont’d: Adhesions