Biology presentationBiology presentation

Lu WeiLu Wei

Chen xinluChen xinlu

Hu zhenzhenHu zhenzhen

He shanliang He shanliang

Minh TueMinh Tue

Our topicOur topic

The transmission of nerve signals The transmission of nerve signals from one neuron to another is often from one neuron to another is often mediated by chemical substances, or mediated by chemical substances, or neurotransmitters. Explain how neurotransmitters. Explain how electrical signals arriving at the pre-electrical signals arriving at the pre-synaptic neuron are converted to synaptic neuron are converted to chemical signals and back to chemical signals and back to electrical signals at the post-synaptic electrical signals at the post-synaptic neuron. In addition to chemical neuron. In addition to chemical neurotransmitters, what other forms neurotransmitters, what other forms of signals may be transmitted of signals may be transmitted between two neurons.between two neurons.

Neurons create electrical signals Neurons create electrical signals across their membranesacross their membranes

The researchers found that unstimulThe researchers found that unstimulated, inactive neurons maintain a coated, inactive neurons maintain a constant electrical difference, or potentinstant electrical difference, or potential, across the poles of a battery. As ial, across the poles of a battery. As in a battery, the electrical potential acn a battery, the electrical potential across a neuron membrane stores enerross a neuron membrane stores energy. This potential across a neuron mgy. This potential across a neuron membrane stores energy, called the reembrane stores energy, called the resting potential ,that is always sting potential ,that is always

negative inside the cell and ranges negative inside the cell and ranges from-40 to-90 mV.from-40 to-90 mV.

If the neuron is stimulated, either If the neuron is stimulated, either naturally or by an experimenter, naturally or by an experimenter, the negative potential inside the the negative potential inside the neuron can be made either more neuron can be made either more or less negative. If it is made or less negative. If it is made enough less negative that it enough less negative that it reached a level called threshold, reached a level called threshold, an action potential is triggered. an action potential is triggered. During an action potential, the During an action potential, the neuron’s potential rapidly rises to neuron’s potential rapidly rises to about +50mV inside the cell.about +50mV inside the cell.

Action potentials last a few Action potentials last a few milliseconds before the cell’s milliseconds before the cell’s negative resting potential flows negative resting potential flows rapidly down the axon to the rapidly down the axon to the synaptic terminal, where the synaptic terminal, where the signal is communicated to signal is communicated to another cell at a synapse.another cell at a synapse.

Neuron communicate at synapsesNeuron communicate at synapses

Once an action potential reaches the Once an action potential reaches the synaptic terminal of a neuron, a synaptic terminal of a neuron, a muscle cell, or a gland. This muscle cell, or a gland. This transmission occurs at synapses. transmission occurs at synapses. The signals transmitted at synapses The signals transmitted at synapses are called postsynaptic potentials. are called postsynaptic potentials. At a synaptic terminal, an action At a synaptic terminal, an action potential encounters a synapse, potential encounters a synapse, where parts of 2 neurons are where parts of 2 neurons are specialized to communicate with one specialized to communicate with one another. another.

A tiny gap separates the synaptic A tiny gap separates the synaptic terminal of the first neuron, the terminal of the first neuron, the pre-synaptic neuron, from the pre-synaptic neuron, from the second neuron, the postsynaptic second neuron, the postsynaptic neuron. Both the dendrites and neuron. Both the dendrites and the cell bodies of neurons are the cell bodies of neurons are typically covered with synapses. typically covered with synapses. The synapse includes the The synapse includes the synaptic terminal of the pre-synaptic terminal of the pre-synaptic neuron, the gap, and synaptic neuron, the gap, and the specialized membrane of the the specialized membrane of the postsynaptic neuron, which postsynaptic neuron, which

Which contains receptors for Which contains receptors for neurotransmitters.neurotransmitters.

When an action potential reaches When an action potential reaches a synaptic terminal, the inside of a synaptic terminal, the inside of the terminal becomes positively the terminal becomes positively charged. This charge causes charged. This charge causes storage vesicle in the synaptic storage vesicle in the synaptic terminal to release terminal to release neurotransmitter molecules neurotransmitter molecules rapidly diffuse across the gap rapidly diffuse across the gap and briefly bind to receptors in and briefly bind to receptors in the membrane of the the membrane of the postsynaptic neuron beforepostsynaptic neuron before

Diffusing away and being taken Diffusing away and being taken back into the presynaptic neuron.back into the presynaptic neuron.

The other forms of signalsThe other forms of signals

Postsynaptic potential (PSP)Postsynaptic potential (PSP) Excitatory postsynaptic potentialExcitatory postsynaptic potential

(EPSP) (EPSP)

Inhibitory postsynaptic potential Inhibitory postsynaptic potential (IPSP)(IPSP)

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