EXCITABLE TISSUES, ACTION POTENTIAL

What are excitable tissues?

Tissues capable of responding to a stimulus by generating and conducting an action potential.

Which are the two major excitable tissues?

Nervous tissue and muscle tissue.

What electrical signal do excitable tissues generate?

Excitable tissue

What is the primary function of nervous tissue?
What is the primary function of muscle tissue?

To receive, process, and transmit information.

To contract and produce movement or force.

Name the three types of muscle tissue.

Skeletal, cardiac, and smooth muscle.

Which muscle lines hollow organs?

Smooth muscle

Define excitability (irritability).

The ability of a cell to respond to a stimulus by generating an action potential.

Define conductivity.

The ability to transmit an action potential along the membrane.

What are the two refractory period?

Absolute and relative refractory periods.

What is the all-or-none law?

Once threshold is reached, a full action potential occurs; if not, none occurs.

Does stimulus strength affect the size of an action potential?

No. It’s either All or None

What are ion channels?

Membrane proteins that allow ions to cross the membrane.

What is the function of the Na/K pump?

How many are pumped in and out?

Maintains Na and K gradients using ATP.

3 Sodium ion and 2 Potassium ion.

Which ion is mainly responsible for the negative resting membrane potential?

K ion

What is the resting membrane potential (RMP)?

The electrical potential difference across the membrane when the cell is at rest.

What is the approximate RMP of a neuron?

Approximately -70 mV

What is the approximate RMP of skeletal muscle?

Approximately -90 mV

Why is the inside of the cell negative at rest?

Due to K ion leakage, impermeable intracellular anions, and the Na/K pump.

Which channels are mainly open at rest?

Potassium leak channels.

What maintains the resting membrane potential?

K ion leak channels and the Na/K ion pump.

Define action potential.

A rapid, temporary reversal of membrane potential following stimulation.

What is threshold potential?

The minimum membrane potential required to trigger an action potential.

What happens during depolarization?

Na ion Voltage gated channels open and Na enters the cell.

What happens during repolarization?

K ion voltage gated channels open and K ion leaves the cell.

What is hyperpolarization?

The membrane becomes more negative than the resting membrane potential.

Why does hyperpolarization occur?

K ion channels remain open briefly, allowing extra K ion to leave.

What restores the membrane after an action potential?

Closure of K ion channels and continued action of the Na/K ion pump.

What is the first event after threshold is reached?

Opening of Na ion voltage gated channels.

What happens to Na ion channels after depolarization?

They become inactivated.

What opens after Na ion channels inactivate?

K ion Voltage-gated Channels.

Why is the refractory period physiologically important?

It prevents continuous firing and ensures one-way impulse conduction.

Why can’t t an action potential travel backward in a neuron?

The membrane behind it is in the refractory period.

Which process requires ATP: K ion leak or Na/K ion pump?

Na/K ion pump

What would happen if the Na/K ion pump stopped work?

Ion gradients would gradually disappear, making normal electrical activity impossible.

Local anesthetics block the movement of which ion?

Na ion

Why do local anesthetics prevent pain sensation?

They block action potential generation and conduction in nerves.