Nerve signals are transmitted through a combination of electrical and chemical processes. Within a neuron (nerve cell), the signal travels as an electrical impulse. Between neurons, the signal is transmitted chemically via neurotransmitters.
Electrical Transmission within a Neuron:
The neuron's membrane maintains an electrical potential due to different ion concentrations inside and outside the cell. This difference creates an electrochemical gradient. When stimulated, ion channels open, altering the membrane potential and generating an action potential – a rapid electrical signal that propagates down the neuron's axon (a long fiber extending from the cell body). This electrical signal is the core of nerve impulse transmission within a single neuron. The axon, acting as a cable, transmits these impulses efficiently. Think of it as a domino effect of electrical changes along the axon.
Chemical Transmission Between Neurons:
At the synapse (the junction between two neurons), the electrical signal triggers the release of neurotransmitters from the presynaptic neuron. These chemical messengers diffuse across the synaptic cleft (the tiny gap between neurons) and bind to receptors on the postsynaptic neuron. This binding initiates a change in the postsynaptic neuron's membrane potential, potentially triggering a new action potential and continuing the signal. Each neuron can connect with hundreds of thousands of other neurons via this complex interplay of chemical and electrical processes. A single neuron might receive input from many other neurons, and depending on the strength and type of signals received and the summation of these signals, a further impulse may or may not be generated. This process is crucial for the brain's complex information processing.
Summary of Transmission Methods:
- Electrical: Within a neuron, along the axon, as an action potential.
- Chemical: Between neurons, across the synapse, via neurotransmitters.
The peripheral nervous system (PNS) is a network of nerves that carries signals from all parts of the body to the spinal cord (and vice versa), facilitating communication between the central nervous system (CNS) and the body. Noxious stimuli initiate messages transmitted via nerves to the spinal cord.
Examples:
- Sensory neurons transmit information from the body to the brain (e.g., feeling a hot stove).
- Motor neurons transmit signals from the brain to muscles (e.g., pulling your hand away from the hot stove).
- Interneurons connect sensory and motor neurons within the CNS.
