Nerve Impulses and Reflexes Guided NotesName:______

Do now

What are the 3 functions of the nervous system?

Irritability and Conductivity

Individual neurons have two major functional properties: irritability and conductivity.

Irritability = ability to ______and ______

Conductivity = ability to ______to other neurons, muscles, or glands.

Irritability

What types of stimulus trigger nerve impulses?

______(e.g. touch, temperature, pressure, tension, sight, hearing, chemical)

All ______(interneurons, motor neurons) ______released by other neurons

What is a nerve impulse?

A quick switch in ______that travels all the way along the axon of the neuron

Occurs due to flow of ions across the membrane

All – or – nothing

Resting Potential

Neurons at rest have an______across the cell membrane, known as the resting potential.

The resting potential is approximately -70mV.

The resting potential is maintained by:

______(3 Na+ pumped out for every 2 K+ pumped in)

______(K+ can diffuse back out to some degree)

______(- ions) within cell

Action Potential

An action potential involves the rapid depolarization and repolarization of the membrane.

Steps of an Action Potential

1) When a stimulus is applied to a nerve, ______, allowing Na+ to diffuse in.

2) Once a threshold is reached, ______, causing ______of the membrane.

When the membrane is depolarized, the inside of the membrane is ______than the outside.

3) Membrane ______occurs when Na+ gates close and K+ gates open, allowing net ______

______outside. Repolarization ______

______(more negatively charged inside)

4) The K+ gates close and the resting potential is maintained by the Na+ / K+ pump

Turn and Talk

At rest, what ions are most abundant outside the cell, and which are most abundant inside the cell?

Which side of the membrane is more negative at rest?

Describe how the movement of ions causes

Depolarization

Repolarization

Nerve Impulse Propagation

The nerve impulsemoves along the axon.

The change in voltage of onearea triggers thedepolarization of the next area.

Repolarization follows immediately.

In myelinated neurons the impulse “jumps” from node to node,

rather than traveling the whole length of the axon – makes the impulse

transmission much more efficient.

Conductivity

Synapses

•The ______is called a synapse

• Chemicals called ______carry the nerve impulse across the synapse.

Steps of synaptic transmission

  1. The nerve impulse reaches the axon terminal.
  2. Ca+ gates open, allowing Ca+ into the axon.
  3. The Ca+ causesvesicles containingneurotransmitters to empty into the synapse
  4. The neurotransmitters diffuse across the synaptic cleft and binds with receptors of the next neuron.
  5. Na+ channels openin the dendrites of the post-synapticneuron
  6. Post-synaptic neuron depolarizes
  7. Remainingneurotransmitter isbroken down.