Quiz #2: Reflex Action/Arcs & Nerve Impulse Conduction

How can peripheral nerves best be studied?

Examining reflex actions/arcs

Reflex Actions

Involuntary, quick responses by an organ or organ system to a stimulus outside the CNS

Examples of Reflex Actions

• Blinking

• Sneezing

• Coughing

• Shivering

• Quick Balance Recovery

• Sudden withdrawal of limb

Why do reflex actions occur?

As a response to protect the body and maintain homeostasis

Are response times long or short for reflex actions?

Short

Reflex Arc

The route/path which an impulse must travel to bring about a reflex action

Once a reflex begins, which way does it travel?

It always proceeds in the same direction

Reflex Arc Pathway

1. Nerve endings (receptors) receive a stimulus

2. Stimulus is transformed into nerve impulse

3. Sensory nerves conduct impulses to CNS

4. Interneurons conduct impulse from sensory to motor neurons

5. The impulse is conducted to an effector, such as a muscle, organ, or gland

6. The effector causes a response or reflex action to the original stimulus

What happens during or after a reflex action takes place?

The impulse may be conducted to the brain where it is converted to a perception and you become conscious of the stimulus

What happens when there are more synapses in the reflex pathway?

It takes longer for a reflex to occur

Irritability

The ability for a neuron to respond to a stimulus

Conductivity

The ability of a neuron to transmit a nerve impulse

When does nerve activity begin?

Receptors within the skin, eyes, ears, nose, muscles, etc. are stimulated

What is the charge of a resting neuron?

Outside: Positive

Inside: Negative

A resting neuron is also known as what?

Polarized- different charges inside and outside

All or none principle

Electrical charges separated by region have the potential to do work should the difference in charges disappear

What happens in a depolarized neuron?

Na+ ions moved into the cell, making the inside more positive because of the Na influx from the outside of the cell

What is the charge of a depolarized neuron?

Outside: Negative

Inside: Positive

What is the charge of a repolarized neuron?

Outside: Positive

Inside: Negative

What happens during repolarization?

Potassium ions flow out, making the inside negative and outside positive again.

• More K ions on outside

Is a transmission of an impulse down an axon electrical or chemical?

Electrical

Is the stimulation of another neuron or effector at a synapse by a neurotransmitter electrical or chemical?

Chemical

Does a resting neuron conduct impulses?

No

When an action potential is generated, is the cell membrane more or less permeable to sodium?

More

When a nerve cell is depolarized and repolarized, what kind of current is produced?

Bioelectric

Salutatory Conduction

Nerve impulses traveling are jumping node to node, increasing the speed of the nerve impulse

Steps of Nerve Impulse Transmission

1. Receptors within skin, eyes, ears, etc. are stimulated

2. Resting Neuron/Polarized: Positive outside (Na), negative inside (K)

3. Depolarized Neuron: Negative outside (K) Positive inside (Na)

4. Repolarized Neuron: Positive outside (K), negative inside (Na)

When a series of action potentials occur, what is created?

A nerve impulse