Human Anatomy & Physiology (Human Body Systems)

Unit 2: Unit 2: Communication (Nervous & Endocrine)HBS 2.1Human Body Systems: nervous system

Trace a neural signal through a neuron

Follow a message from one neuron's dendrite to the next across a synapse, naming where it is electrical and where it is chemical.

Builds on (2 levels back)inferred · med confidence

A cell has specialized parts: A neuron is a cell; tracing a signal means naming its parts in order, so you first need the idea that a cell's parts each have a job.
Communication needs a direction: A message has a start and an end. Knowing signals travel one direction sets up the dendrite-to-axon-terminal path.

Prerequisites are inferred: pending teacher review.

Re-learn the skill with worked practice and clear examples.

Inside a neuron the signal is electrical and runs dendrite to cell body to axon to axon terminal. At the synapse it becomes chemical: a neurotransmitter crosses the gap to the next neuron's dendrite.

Step 1: Name the parts in order

Dendrite (receives) to cell body (holds the nucleus) to axon (the long fiber) to axon terminal (the sending tip). This whole path inside one neuron carries an electrical impulse.

Step 2: Cross the gap chemically

Neurons do not touch. The tiny gap between them is the synapse. The electrical impulse cannot jump it, so the axon terminal releases a chemical called a neurotransmitter that drifts across and lands on the next neuron's dendrite.

Step 3: Sum up the two parts

Electrical ALONG the axon, chemical ACROSS the synapse. Then the next neuron starts the electrical part over again.

Practice

A signal is moving down the axon and reaches the axon terminal. How does the message get to the NEXT neuron?

Reviewed

Two neurons side by side. The left neuron's branchy dendrites and round cell body lead into a long axon ending in a tip. A small gap separates that tip from the right neuron's dendrites. Dots sit in the gap. Nothing is labeled.

A.The electrical impulse jumps straight across the gap into the next neuron
B.The axon terminal releases a neurotransmitter that crosses the synapse to the next neuron's dendrite
C.The two neurons fuse together so the message passes through
D.The message stops because neurons cannot connect

Show the worked solution ▾

Answer: B. The axon terminal releases a neurotransmitter that crosses the synapse to the next neuron's dendrite

Step 1: Spot the gap: The diagram shows the sending tip does not touch the next cell: there is a small space (the synapse) with dots in it.
Step 2: Cross it chemically: The tip releases a chemical, a neurotransmitter (the dots), which drifts across and lands on the next neuron's dendrites.

Why it's right: Neurons do not touch; the axon terminal releases a neurotransmitter that crosses the synapse to the next neuron's dendrite.

Why the others miss:

A: The electrical impulse cannot jump the gap; that is why a chemical is used.
C: Neurons stay separate: they do not fuse to pass a message.
D: The message does continue; the synapse is how neurons connect.

Aligned to Human Body Systems: synaptic transmission · reading level ~grade 9

Where you'd see this

Many medicines (like some used for depression or pain) work by changing how much neurotransmitter stays in the synapse.

Careers that use this

Neurologist: Figures out where a signal is failing: along an axon or at a synapse: to explain a patient's numbness or weakness.

Video library

Watch: Trace a neural signal through a neuron

2-Minute Neuroscience: Synaptic Transmission

Neuroscientifically Challenged

Guided notes

Fill these in as you work through the lesson.

Big idea: A nerve signal travels one direction through a neuron: in at the dendrites, down the axon as an electrical impulse, then across the synapse as a chemical to the next neuron's dendrite.

Key terms: write the meaning

Dendrite (the branch that receives the incoming message):
Axon (the long fiber the impulse travels down):
Synapse (the tiny gap between two neurons):
Neurotransmitter (the chemical that crosses the gap):

The rule

Inside one neuron the signal is and runs from dendrite to cell body to axon to terminal. To reach the next neuron it crosses the as a chemical called a .

Check yourself

Put these in order: axon, dendrite, axon terminal, cell body.
Where is the signal electrical, and where does it become chemical?
Why can't the impulse just jump straight into the next neuron without the synapse?

Work one example

A signal starts at a neuron's dendrites. Write the full path it takes to send a message to the next neuron, and at each step say whether it is electrical or chemical.