C2.2 Neural Signaling

Neuron

Cells in the nervous system that carry electrical impulses.

Dendrites

Short branched nerve fibers that receive signals from other neurons and transmit them to the cell body.

Axons

Elongated nerve fibers that transmit electrical impulses from the cell body to other neurons, muscles, or glands.

Myelinated nerve fibers

Nerve fibers with myelin sheaths around the axon

What are myelin sheaths made of?

Layers of Schwann cells

What are gaps between myelin sheaths called?

Nodes of Ranvier

Membrane potential

Difference in voltage inside and outside a cell membrane

Resting potential

The membrane potential when an impulse is not being transmitted, typically around -70mV.

Action potential

A rapid change in the cell's membrane potential during a nerve impulse.

Depolarization

A change in membrane potential from negative to positive, reaching approximately +35mV.

Repolarization

The process of membrane potential returning back from positive to negative.

Sodium-potassium pump

A pump that transfers 3 sodium ions out and 2 potassium ions in using active transport to establish and maintain concentration gradients.

Synapse

A junction between neurons or between neurons and muscle fibers or gland cells where signals are transmitted.

Neurotransmitter

Chemicals that carry signals across the synaptic gap from one neuron to another.

Effectors

Cells that carry out the response to a stimulus (muscle fiber, gland cells, etc)

Synaptic gap

Space between the axon and dendrite of neighbouring neurons

What occurs at the presynaptic membrane at depolarization?

Calcium ion channels open and calcium ions enter the neuron

What occurs at the presynaptic neuron after calcium ion channels open?

Vesicles containing neurotransmitters move to and merge with the membrane, releasing neurotransmitters into the synaptic gap by exocytosis

What occurs at the postsynaptic neuron after the release of neurotransmitters?

Neurotransmitters bind to receptors in the postsynaptic membrane, causing ion channels to open.

What occurs at the postsynaptic neuron after ion channels open?

Ions diffuse into the neuron, causing membrane potential to rise, triggering an action potential

What happens to neurotransmitters after action potential at postsynaptic neuron is reached?

Broken down by enzymes and reabsorbed into the presynaptic neuron

Acetylcholinesterase

An enzyme present in the synaptic gap that breaks down acetylcholine into choline and acetate.

What occurs when threshold potential is reached?

Sodium channels open, sodium ions diffuse into the axon, leading to depolarization of the neuron

How does repolarization occur?

Potassium channels open in response to depolarization, potassium ions diffuse out of the axon, repolarization of neuron

Local current

At depolarization, the influx of sodium ions in the axon causes them to diffuse along the axon to the polarized area

Saltatory conduction

A process where nerve impulses jump from one node of Ranvier to the next in myelinated fibers, speeding up transmission.

Property of Schwann cells

Prevents ion movements

Why do action potentials only occur at Nodes of Ranvier in myelinated nerve fibers?

Sodium/potassium pumps are clustered at the Nodes of Ranvier

Neonicotinoids

Synthetic compounds that irreversibly bind to acetylcholine receptors, blocking transmission in the insect CNS.

Cocaine

Binds to dopamine reuptake transporters, causing dopamine to build up in the synaptic gap, which stimulates neurotransmission of dopamine

GABA

An inhibitory neurotransmitter that causes chloride ions to enter the neuron by binding to the receptor, causing hyperpolarization of the neuron

Hyperpolarization

The process by which a postsynaptic neuron becomes less likely to propagate an action potential due to the entry of chloride ions decreasing membrane potential.

Summation

The process by which multiple releases of excitatory neurotransmitters combine to cause an action potential.

Where are pain receptors located in the nervous system?

Nerve endings of sensory neurons near the skin

How are pain signals transmitted to the CNS?

Pain signals are transmitted when ion movement in sensory neurons generates an action potential, which travels to the spinal column where interneurons relay the signal to the CNS.

Emergent property

A property that emerges from the interactions of individual elements within a system, like consciousness from neuron interactions.