Use complete sentences to explain what happens in the nervous system when your finger is hurt. Include an explanation of what a neuron is.

Nervous System: Tissue damage activates pain receptors in the skin. A signal is sent from the peripheral nerve, to the spinal cord where neurotransmitters or chemical messengers are released. This activates other nerves to pass a signal to the brain. The signals are relayed to the somatosensory cortex for pain, sensation, touch, etc.

Neuron: A neuron is a nerve cell that carries electrical impulses. Neurons are the basic units of our nervous system. Neurons have a cell body, dendrites, and an axon, which are nerve fibers. There are about 86 billion neurons in the human brain, which is about 10% of all brain cells.

d. organisms have cells with different shapes and functions.