A & P Lecture Review Guide 4

A & P Lecture Review Guide 4

What is the difference between intracellular fluid and extracellular fluid

Intracellular fluid: Fluid inside the cells

Extracellular fluid: Fluid outside of the cells

What are the 2 types of extracellular fluids?

Interstitial fluid: Fluid that fills the spaces between the cells

Plasma: The fluid part of the blood, found inside blood vessels.

What portion of body weight is represented by intracellular and extracellular fluid

ICF (intracellular): about 40% of body weight

ECF (extracellular) about 20% of body weight

What is a cation? What is the predominant cation in ICF and ECF?

Cation: A positively charged ion

ICF: Potassium (K+)

ECF: Sodium (Na+)

What is transmembrane potential?

The difference in electrical charge across a cells membrane (inside vs outside)

• in neurons the inside is usually more negative compared to the outside 

Passive channels (leak channels):

• always open

• permeability changes with conditions

Example: potassium leak channels

Active (gated) channels

• open and close in response to stimuli

• at resting potential most gated channels are closed

Chemically gated

• open in presence of specific chemicals at a binding site

• found on neuron cell body and dendrites 

Voltage gated

• respond to changes in transmembrane potential

• have activation gates (opens) and inactivation gates (closes)

• characteristic of excitable membrane•found in neural axons, skeletal muscle sarcolemma, cardiac muscle

Mechanically gated channel:

• respond to membrane distortion

• found in sensory receptors (touch, pressure, vibration

Propagation regarding an axon

• Propagation is how an action potential travels down the length of an axon

What is the resting membrane potential of a neuron?

-70mV

What is the threshold voltage of a voltage-gated sodium channel?

-55mV

What happens to the membrane potential when the voltage-gated sodium channel opens?

Sodium rushes into the neuron and the membrane potential becomes positive (30mV)

What is that phase of action potential called when sodium rushes into the cell?

Depolarization phase

What is the threshold voltage of a voltage-gated potassium channel?

-55 mV

hat is that phase of action potential called when potassium is ‘kicked’ out of the cell??

repolarization phase

The voltage-gated potassium channels are ‘slow to close’ and the membrane potential becomes more negative than the normal resting membrane potential. What is that phase of action potential called

Hyperpolarization

. Explain what is meant by the phrase, “An action potential is an all-or-none phenomenon.”

• Ifa stimulus exceeds the threshold amount, an action potential will always fire completely 

Absolute Refractory Period.

Where you absolutely cannot have a second action potential

Relative refractory period 

You can have another action potential but it has to be relatively strong

What is the sodium-potassium pump

It’s a little “ion machine” in the neuron’s cell membrane.

• It pushes 3 sodium ions (Na⁺) out of the cell.

• It pulls 2 potassium ions (K⁺) in.

• It uses energy (ATP) to do this.

why is the sodium-potassium pump so important to nerve impulse transmission?

• Keeps the inside of the neuron negative (around –70 mV).

• Resets the neuron after each nerve impulse so it can fire again.

• Creates the sodium and potassium imbalance that makes action potentials possible.

How many of each ion does the sodium-potassium pump move? In which direction does each ion get moved?

3 Na⁺ out, 2 K⁺ in.

Predict what would happen if there was an electrolyte imbalance (loss of homeostasis) of Na+ and K+ in the body in relation to Action Potentials

if Na⁺ and K⁺ levels are off, neurons can’t send signals properly — they may fire too easily or not fire at all, leading to muscle, nerve, or heart problems.