Action Potentials and Ion Movement

what portion of total body weight (TBW) is represented by extracellular fluid

16% interstitial fluid+ 4% plasma. (20% total)

How many potassium and sodium does the sodium potassium pump move?

3 sodium 2 potassium

Voltage Gated Channel

A voltage-gated Na+ channel that responds to changes in the membrane potential. At its resting membrane potential of -70 mV the channel is closed; at -60 mV the channel opens; at +30 mV, the channel is inactivated

Chemically Gated Channel

Chemically Gated Channel: a chemically gated (ligand-gated) Na+ channel that opens in response to the presence of ACh (ligand) at a binding cite

what are the differences between axons and dendrites?

Dendrites receive messages from other cells Axons pass messages from the cell body to other neurons, muscles, or glands

Label the major structures found in a neuron and describe their functions

Dendrites- signal receptive region nerve cell Axon- impulse generating and conducting region Myelin Sheath-serves to protect and insulate axon/increases speed

Extracellular fluid, which is also called_______ and _________

Extracellular fluid (ECF) surrounds all cells in the body. Extracellular fluid has two primary constituents: the fluid component of the BLOOD (called plasma) and the INTERSTITIAL FLUID (IF) that surrounds all cells not in the blood.

How do sodium and potassium leak channels play a role in the development of the negative membrane potential of the axolemma (plasma membrane of the axon)?

K+ and Na+ are positively charged, and if positively charged ions leak into a cell then the cell becomes more positively charged and the area outside the cell becomes more negatively charged. Negative cell potential causes + ion channels to open

What is the sodium-potassium pump, and why is it so important to nerve impulse transmission?

Move potassium ions into the cell while simultaneously moving sodium ions out of the cell.

Which neurological disease destroy the myelin sheath of neurons in the CNS? What might be some symptoms early on in this disease?

Multiple Sclerosis is a disease characterized by recurrent incidents of demyelination that affects axons in the optic nerve, brain, and spinal cord. Common signs include partial loss of vision, problems w speech, balance and general motor coordination

What are the major electrolytes found in the human body and what are the normal ranges of the concentrations of these electrolytes?

Na: Extracellular: 142, Intracellular: 10 K: Extracellular: 4, Intracellular: 140 Ca: Extracellular: 5, Intracellular: 1 Mg: Extracellular: 3, Intracellular: 58 Cl: Extracellular: 103, Intracellular: 4 Amino Acids: Extracellular: 5, Intracellular: 40 Glucose mg%: Extracellular: 90, Intracellular: 0-20

Along the axons of myelinated neurons there are gaps in the myelin where the axolemma (cell membrane of the axon) is exposed. What is the name given to these gaps in myelin? What is the significance of these gaps in the myeline sheath?

Nodes of Ranvier: periodic gap in the insulating sheath (myelin) on the axon of certain neurons that serves to facilitate the rapid conduction of nerve impulses.

Repolarization (falling phase)

Repolarization phase, is caused by the flow of potassium ions out of the cell and the interior of the cell loses positive ions

what is meant by the term "propagation" in regards to an axon?

Sending a signal from one end of the neuron to another

intravascular fluid

The fluid space within the blood vessels is made up of blood cells and serum (water, clotting factors, chemicals, and electrolytes).

depolarization (rising phase)

The process during the action potential when sodium is rushing into the cell causing the interior of the cell to become more negative

What is the significance of water in the human body?

Water takes up 60% of total body weight. It is continually distributed between the digestive tract, blood stream and intracellular fluid.

membrane potential

When a nerve or muscle cell is at "rest", its membrane potential is called the resting membrane potential. In a typical neuron, this is about -70 millivolts

Explain what is meant by the phase "An action potential is an all of none pheonomenon"

a given stimulus either triggers a typical action p

Mechanically Gated Channel

a mechanically gated channel, which opens in response to distortion of the membrane

action potential

a neural impulse; a brief electrical charge that travels down an axon

activation gates

closed at rest; open with depolarization, allowing Na+ to enter cell

axon terminal

electrical impulse is converted to a chemical signal

intracellular fluid

fluid within a cell 40% body weight

polarity

needed in neurons for communication

inactivation gates

open at rest; block channel once it is open to prevent more Na+ from entering cell

saltatory

propagation of action potentials along myelinated axons form one node of ranvier to another, increasing conduction velocity of action potentials

How many Na and K ions does the Na/K pumps move and in what direction do these two ions move?

pumps 3 sodiums out to 2 potassiums in.

What is myelin and what is its primary function?

serves to protect and electrically insulate axon increases speed of transmission of nerve impulses **only associates w axons, not dendrites

What is meant by the term "polarity" in regard to the cell membrane of a neuron?

spatial differences in the shape, structure, and cell function

threshold

the level of stimulation required to trigger a neural impulse (between -60 mV and -55 mV)

What is salutatory conduction?

the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.

resting potential

the state of the neuron when not firing a neural impulse

refractory period (absolute and relative)

the time following an action potential during which a new action potential cannot be initiated