Second Lecture 7/17

Front 1

What is Osmosis?

Back 1

the Diffusion of water across the membrane down a water concentration gradient.

Front 2

What is Osmotic Pressure?

Back 2

Front 3

If you place a red blood cell in a solution and there is no osmotic gradient or movement of water this fluid is considered?

Back 3

Isotonic

Front 4

If you place a red blood cell in a solution and there is an osmotic gradient of water into the cell this fluid is considered?

Back 4

Hypotonic

Front 5

If you place a red blood cell in a solution and there is an osmotic gradient of water out of the cell this fluid is considered?

Back 5

Hypertonic

Front 6

What type of receptor is a Nicotinic Receptor?

Back 6

Ligand Gated Ion Channel. Found on skeletal muscles and activates with acetylcholine.

Glycine is the inhibitory neurotransmitter which is part of a Cl- channel.

Front 7

What type of receptor is a Muscarinic Receptor?

Back 7

A G coupled protein which involves a 2nd messenger.

Acetylcholine and Muscarine are the ligands that bind to the receptor on tissue such as heart muscle.

Front 8

Second messenger systems have what kind of effect on the signal?

Back 8

Amplification- providing a huge amplification of the initial signal.

Front 9

Back 9

Front 10

What does the Peripheral Nervous System consist of?

Back 10

12 Cranial Nerves

31 Spinal Nerves

Front 11

What are the 2 types of nervous tissue?

Back 11

Neurons-Functional units of NS

Excitability-change membrane potential in response to stimulus

Conductivity-transmit change down membrane

Support Cells-6 different types, provide physical and metabolic support. (90% of cell but 50% of volume)

Front 12

Name the 6 different types of support cells.

Back 12

Astrocytes

Microglial

Ependymal

Oligodendrocytes

Schwann

Satellite

Front 13

Back 13

Astrocytes-form BBB, regulates ionic composition of ISF surrounding neurons

Front 14

Back 14

Microglial-confines the CNS, kill foreign organism

Front 15

Back 15

Ependymal-produces CSF

Front 16

Back 16

Oligodendrocytes-form myelin sheath in CNS

Front 17

Back 17

Schwann-Form myelin sheath in PNS

Satellite-regulate ions in ISF around Ganglia (Unipolar Nerve Cells)

Front 18

What two things limit the exchange between the plasma and the ISF in the Blood Brain Barrier?

Back 18

No pores or gaps between the adjacent endothelial cells

Processes from the astrocytes wrap aroun the tube to limit exchange.

Must be small & lipid soluble to pass through

Front 19

Back 19

Front 20

Back 20

Bipolar Neuron

Front 21

Back 21

Multipolar Neuron-Most common type 99%

Front 22

Back 22

Unipolar Neuron- Found in PNS, part of afferent NS

Front 23

What are the parts of the multipolar Neuron?

Back 23

Front 24

What is Myelin?

Back 24

the Sheath that lines an axon determines how fast the AP is transmitted (myelinated-faster)

Oligodendrocytes in the CNS and Schwann in PNS

Front 25

What is a Nerve?

Back 25

A lot of Axons packaged together in the PNS.

Front 26

What is a Mixed Nerve?

Back 26

a Combination of efferent and afferent nerves.

All spinal nerves are mixed.

Front 27

What is a Nerve tract?

Back 27

a bundle of axons contained within the CNS.

Front 28

What is a membrane potential?

Back 28

When the inside of a cell is slightly negative when compared to the outside.

Front 29

What is an electrical Potential difference?

Back 29

The amount of charge difference across the membrane.

Front 30

What is the formula for Ohm's Law?

Back 30

Current=Voltage/Resistance I=V/R

Conductance is the inverse of Resistance g=1/R

Front 31

What is the ionic mechanism of Membrane Potentials?

Neurons at rest have a membrane potential of -70mV

Back 31

It is created by a combination of:

1-direction of Na+ & K+ concentration gradients across the membrane.

2-Difference in conductance of resting membrane to the Na+ & K+

Front 32

Is the resting membrane 50-70% more permeable or leaky to Na+ or K+?

Back 32

It is more permeable to K+.

Front 33

What does the Na/K pump do in the cell membrane?

Back 33

Using ATP transports Na+ out of the cell and K+ back into the cell. It transports 3 Na out for 2 K in.

Front 34

What does the Nernst Equation Calculate?

Back 34

It allows you to calculate the Em required to provide an electrical force equal in magnitude but opposite in direction to the chemical force for any Ion (i.e. the equilibrium potential).

Front 35

What is the formula for Nernst Equation?

Back 35

z is the valence of the Ion

Front 36

Back 36

Front 37

What are the four terms describing changes in the membrane potential?

Back 37

Front 38

How can the resting Em (i.e.-70mV) be changed?

Back 38

A change in the Em can be produced by any stimulus that changes permeability (i.e. conductance) of the membrane to any ion.

Front 39

What are the three classes of gated Ion Channels that produce a change in the cell membrane potential?

Back 39

Chemically Regulated Ion Channels

Voltage Regulated Ion Channels

Mechanically Regulated Ion Channels

Front 40

Back 40

Chemically Regulated Ion Channels

Four Types

Cation Na+ & K+

K+

Cl-

Ca++

Depends on NT or Drug is bound to the Receptor

Front 41

Back 41

Voltage Regulated Ion Channel

Three types

Na+(has 2 gates ECF & ICF)

K+

Ca++

Front 42

Voltage Regulated Ion Channels function how?

Back 42

Membrane depolarizes from -70 to -50 (Threshold potential) then the activation gate rapidly opens

The inactivation gate starts to close but takes 1/3 of a msec longer

Both gates need to reset completely before the channel can activate again

Front 43

Back 43

Mechanically Regulated Ion Channels

Mostly occurs in certain types of sensory receptors

Usually cation channels

Front 44

What are the two forms of Electrical Signals used by neurons?

Back 44

Graded or Local potentials-short distance signal

May inhibit or trigger AP

Action Potentials-Long distance signals

Always triggered by graded potentials

Front 45

What are the four characteristics of graded potentials?

Back 45

Can be excitatory (Cation channel) or inhibitory (anion channel)

Amplitude is proportional to the intensity of the stimulus

Potentials decay as they move over distance (decremental conduction)

Can be summated if 2 of more occur close enough together in time

Front 46

What are the two types of Summative effects for graded potentials?

Back 46

Temporal (stimulated at the same location)

Spatial (stimulated a different locations)

Front 47

Do action potentials conduct with or without decrement?

Back 47

Without-no loss of signal over conduction

Front 48

Where are AP initiated in unipolar neurons?

Where are AP initiated in multipolar neurons?

Back 48

In unipolar neurons it is initiated in the very first initial segment of the axon.

In Multipolar neurons it is initiated in the axon hillock and propagated without decrement down the length of the axon to the terminals

Front 49

Why is the resting membrane potential of skeletal and cardiac muscle more negative?

Back 49

The membrane is more permeable to K+.

It is harder to hyperpolarize as the Em is pretty much at the K+ equilibrium Em

Front 50

Does an AP require ATP?

Back 50

No, it is entirely passive.

Also a singe AP has no effect on the ICF & ECF concentrations of Na+ or K+

Front 51

What are the four stages of AP?

Back 51

Resting State

Depolarization-Caused by Na+ entering cell

Repolarization-Caused by K+ Leaving cell

Hyperpolarization-Caused by K+ continuing to leave the cell

Front 52

Back 52

Front 53

Why doesn't the concentration gradients run down when multiple action potentials occur?

Back 53

Because the Na+/K+ pump, it's action is regulated by the Na+ concentration in the ICF. If the Na+ concentration decreases by multiple AP the Na+/K+ pump increases its activity.

With prolonged exercise K+ ECF may increase, gets ahead of pump (transient)