Sensory neurons, also known as afferent neurons, are the information scouts of our nervous system. They act like tiny spies, constantly gathering information about the world around us (and inside us) and sending those messages up to the brain.

Function:

• Detect various stimuli from the environment: light, sound, touch, taste, smell, temperature, etc.

• They can also detect internal changes in the body like blood pressure or hunger.

• Convert these stimuli into electrical signals the brain can understand. This process is called sensory transduction.

Structure:

• Similar to other neurons, they have a cell body, dendrites, and an axon.

• Dendrites: These are tiny antennae that receive information from the environment or from within the body.

• Cell body: This is the processing center of the neuron.

• Axon: This is a long fiber that carries the converted electrical signal up to the brain or spinal cord.

Types:

• There are two main categories:

  • Peripheral sensory neurons: These detect information from the external environment like touch, sound, or temperature.

  • Visceral sensory neurons: These are located within the body and monitor internal conditions like blood pressure or organ stretch.

Analogy:

Imagine your finger touches a hot stove. A sensory neuron in your fingertip detects the heat (stimulus) through dendrites. This information is converted into an electrical signal in the cell body. The electrical signal then travels up the axon to your brain, which interprets it as "hot!" and tells you to move your finger away.

Thermoreceptors: The Temperature Sensors

• Thermoreceptors are specialized sensory neurons responsible for detecting temperature changes, both warm and cold.

• They are located throughout the body, primarily in the skin but also in organs like the hypothalamus (involved in core body temperature regulation).

Specialization:

• Unlike some sensory neurons that can detect multiple stimuli (like touch and pressure), thermoreceptors are highly specialized.

• There are actually two main types:

  • Warm receptors: Their activity increases with rising temperature.

  • Cold receptors: Their activity increases with falling temperature.

• Interestingly, some cold receptors can also respond with a brief burst of activity to very high temperatures, exceeding normal body temperature.

From Temperature Change to Signal:

• When a thermoreceptor detects a temperature shift, its internal chemistry changes.

• This change triggers an electrical signal to be generated in the sensory neuron. The stronger the temperature change, the greater the firing rate of the signal.

Sending the Message:

• The electrical signal travels up the axon of the sensory neuron to the spinal cord and brain.

• Different brain regions interpret these signals based on location and type of thermoreceptor (warmth or cold). This allows us to perceive gradations in temperature and helps regulate our body temperature through mechanisms like sweating or shivering.

Thermoreceptors and Sensory Neurons: Working Together

So, thermoreceptors are specialized sensory neurons crucial for temperature perception and maintaining body temperature. They are a fascinating example of how our sensory system is finely tuned to detect specific aspects of our environment.