Question

3\. Which of the following options correctly describes the sequence of structures present between a receptor and an effector when \(D\) refers dendrite, A refers axon, S refers synapse and \(C B\) refers to cell body ? (a) \(D-C B-A-S-D-C B-A\) (b) \(A-D-C B-S-A-D-C B\) (c) \(D-C B-A-S-A-C B-D\) (d) \(D-A-S-C B-D-A-C B\)

Short answer

Option (c) correctly describes the sequence of structures present between a receptor and an effector.

Step-by-step solution

Understanding Neural Pathway Components

Firstly, understand the components of a neural pathway. A dendrite (D) receives signals and sends them to the cell body (CB). From the cell body, the signals are transmitted along the axon (A) to the synapse (S), which then relays signals to the dendrites of another neuron or directly to an effector such as a muscle or gland.

Determining the Correct Sequence

Knowing the correct flow of the signal, look for the sequence that follows the order: dendrite (D), cell body (CB), axon (A), and synapse (S). The sequence must end with a component that represents an effector or the beginning of another neuron, which could be a dendrite (D) again.

Eliminating Incorrect Options

Eliminate the sequences that do not follow the correct flow of a neural signal. Option (a) is incorrect because it suggests that the signal goes from the synapse back to the dendrite of the same neuron and then through its cell body and axon, which is not the natural flow. Option (b) is incorrect because it starts with an axon (A) and implies the signal goes from a synapse (S) to an axon directly, which isn't the correct sequence. Option (d) shows a sequence that involves going from synapse to cell body directly, which is not correct.

Identifying the Correct Sequence

Option (c) matches the correct neural signal flow: dendrite (D) to the cell body (CB), then along the axon (A), reaching the synapse (S), then to another axon (A) followed by another cell body (CB) and ending with a dendrite (D), which signifies the beginning of the next neuron in the pathway or the effector.

Key concepts

Dendrite Function

Dendrites are critical components of neurons, serving as the primary receivers of electrical signals. Imagine them like the antennae of a neuron, picking up messages from other nerve cells. These signals, often chemical in nature, are converted into electrical impulses that the dendrite then transmits to the neuron's cell body.

In a neuron, multiple dendrites protrude, each with numerous branches, allowing for the reception of signals from multiple other neurons simultaneously. This feature is essential for the complex communication networks that form between neurons in the brain. Moreover, the density and structure of dendritic branches can be influenced by learning and experience, underscoring their role in neural plasticity. Thus, dendrites are not merely passive receivers; they actively influence the strength and specificity of synaptic connections.

Neuron Signal Transmission

The process of signal transmission within a neuron is an intricately timed event. Once the dendrites collect signals, the cell body integrates these signals to determine if the message should be passed along. If the signal is strong enough, the cell body then initiates an action potential.

This action potential is an electrical charge that travels down the neuron's axon, a long, slender projection that can vary greatly in length. The axon functions as a high-speed highway for electrical impulses and is often insulated with a fatty substance called myelin, which increases signal transmission speed and efficiency. When the action potential reaches the end of the axon, the message must be communicated to another neuron or an effector cell, like a muscle or gland, which is where synapses come into play. Neurons convey messages at remarkable speeds, facilitating rapid coordination between various brain regions and the body.

Synapse Role

Synapses are the junctions where neurons connect and communicate with each other or with effector cells. They play the critical role of managing the direction and flow of neuronal signals, ensuring that communication is precise and regulated. When an action potential reaches a synapse, it prompts the release of neurotransmitters, which are chemical messengers.

These neurotransmitters cross the very small gap between neurons, called the synaptic cleft, to bind with receptor sites on the postsynaptic neuron's dendrite. This binding can either excite or inhibit the production of a new action potential in the receiving neuron. It's important to note that synaptic transmission is not a one-way process; synapses can also undergo changes that affect their strength and efficacy, a mechanism called synaptic plasticity, which is considered a cellular basis for learning and memory.