Question

What kind of action can be caused by neurons? (a) Stimulatory (b) Inhibitory (c) Both (a) and (b) (d) Excitatory

Short answer

Both statements (a) and (b) are correct, hence the correct answer is (c) Both (a) and (b).

Step-by-step solution

- Understanding Neurons

Neurons are the units of the nervous system, the cells responsible for receiving sensory input from the external world, sending motor commands to our muscles, and transforming and relaying the electrical signals at every step in between.

- Studying the Options

Now let's look at the options. 'Stimulatory' refers to the capacity of some neurons to excite and provoke a response from other neurons or from the muscles. 'Inhibitory' refers to the ability of certain neurons to prevent or suppress a response. 'Excitatory' is another term for 'stimulatory'. It describes the capability to provoke a response.

- Selecting the Correct Option

Knowing now that neurons can sometimes stimulate other neurons or muscles and sometimes inhibit them depending on the situation and the type of neuron, the correct option is (c) Both (a) and (b).

Key concepts

Neural Communication

Neural communication is an intricate process that allows neurons, the specialized cells of the nervous system, to transmit information throughout the body. This process begins when a neuron receives a signal from its environment or other cells. This signal, in the form of neurotransmitters released across a gap called the synapse, is picked up by the dendrites—the antenna-like extensions of the neuron. The cell body processes this information, and if the signal is strong enough, it triggers an action potential.

An action potential is an electrical charge that travels down the neuron’s axon to communicate with other neurons, muscle cells, or glands. This is akin to an electrical current moving along a wire, causing downstream effects. To further elaborate, the action potential is an all-or-nothing event; once the threshold is reached, the neuron will fire and the message is sent. The axon terminals then release neurotransmitters into another synapse, and the cycle begins anew in the next cell.

Steps in Neural Communication

• Signal reception, where neurotransmitters bind to receptors.
• Signal integration, determining if the neuron will fire.
• Action potential generation, the transmission of an electrical signal.
• Neurotransmitter release, communication to the next neuron.

These are the underlying mechanisms that allow our nervous system to respond to both internal and external stimuli, controlling everything from our thoughts to our movements.

Excitatory and Inhibitory Signals

Within the realm of neural communication, there exist two primary types of signals: excitatory and inhibitory. These signals are crucial for the proper functioning of the nervous system, providing a balance that allows precise control over body processes. Excitatory signals encourage a neuron to fire an action potential. When excitatory neurotransmitters bind to receptors on a neuron, they cause positively charged ions to enter the cell, making it more likely that the neuron will reach the threshold for an action potential.

In contrast, inhibitory signals reduce the likelihood of a neuron firing. Inhibitory neurotransmitters prompt negatively charged ions to enter the neuron or positively charged ions to leave, making the inside of the cell more negative and increasing the difficulty for an action potential to occur.

Key Differences Between Excitatory and Inhibitory Signals

• Excitatory signals cause depolarization, pushing the neuron closer to firing.
• Inhibitory signals cause hyperpolarization, pulling the neuron away from the firing threshold.

These two types of signals work in tandem to regulate responses and maintain equilibrium within the nervous system. For example, in muscle coordination, excitatory signals might prompt muscle contraction, while inhibitory signals ensure muscles don't contract excessively or at the wrong time.

Nervous System Function

The nervous system serves as the command center for the entire body, orchestrating a multitude of functions essential for survival and well-being. It is divided into two main parts: the central nervous system (CNS), comprising the brain and spinal cord, and the peripheral nervous system (PNS), including all other neural elements.

The CNS processes and integrates information it receives from the PNS and generates appropriate reactions. For example, if you touch a hot stove, sensory neurons in the PNS send a message to the CNS, which then quickly sends back a message through motor neurons to withdraw your hand. This protective reflex is just one example of the nervous system coordinating a complex response to maintain body integrity and function.

Essential Functions of the Nervous System

• Sensing changes with sensory receptors.
• Processing and interpreting sensory input.
• Dictating a response by activating effector organs.

The nervous system also plays key roles in cognition, emotions, and maintaining homeostasis—the body's internal balance—by regulating heart rate, blood pressure, breathing, and digestion. The balance of excitatory and inhibitory signals is pivotal in ensuring that the nervous system responds accurately to a wide array of stimuli, ranging from basic reflexes to highly complex thought processes.