chapter 47 Flashcards
(75 cards)
Types of sensory receptors?
There are 5 main types:
1. Mechanoreceptors – respond to mechanical pressure or stretching, such as touch, vibration, or being pressed/pulled.
2. Thermoreceptors – detect temperature changes (some for cold, some for heat).
3. Nociceptors – sense pain from physical (e.g., cuts, strong pressure) or chemical damage (e.g., acid).
4. Electromagnetic receptors – located in the retina, respond to light, and allow vision.
5. Chemoreceptors – detect chemical changes like taste, smell, blood oxygen levels, osmolality, and CO2 levels.
Why do different receptors detect different things?
Each receptor is sensitive to a specific stimulus and ignores others. For example: rods and cones detect light, not heat or pressure; osmoreceptors respond to changes in fluid concentration, not sound; nociceptors respond to damage, not normal touch. This is called differential sensitivity—each receptor is built for its own signal type.
What is a modality of sensation?
A modality of sensation is a specific kind of feeling, like touch, pain, sound, or vision. Even though all nerves send the same electrical signal, the sensation depends on which brain area receives the signal.
What is the labeled line principle?
The labeled line principle states that the sensation type depends on where the signal ends in the brain, not how it was triggered. For example, activating a pain nerve always feels like pain to the brain, no matter how it’s activated (pressure, heat, electricity).
How do receptors turn stimuli into signals?
Receptors generate a receptor potential by changing their electrical state in response to a stimulus.
Mechanisms include:
1. Mechanical deformation opening ion channels.
2. Chemicals binding and opening channels.
3. Temperature changes altering membrane permeability.
4. Light altering membrane properties (especially in the eye). All cause ion flow, changing the receptor’s membrane potential.
What is a receptor potential?
A receptor potential is an electrical change in a receptor’s membrane due to ion movement triggered by a stimulus. It is the first step in converting a stimulus into a nerve signal.
How strong can receptor potentials get?
Receptor potentials can reach up to ~100 mV with strong stimuli, similar in size to a full action potential.
How do receptor potentials lead to action potentials?
If the receptor potential exceeds a threshold, it triggers action potentials in the connected nerve. Stronger stimuli raise the receptor potential more, causing a higher frequency of action potentials. The brain reads stimulus strength by counting these action potentials.
What is the Pacinian corpuscle?
It is a mechanoreceptor that responds to pressure. It has a central unmyelinated nerve tip inside onion-like connective layers. Outside the capsule, the fiber becomes myelinated. It converts mechanical pressure into electrical signals.
How does the Pacinian corpuscle create a receptor potential?
When pressure is applied, the connective layers compress the nerve tip, opening ion channels. Sodium ions flow in, creating a receptor potential. This causes local currents that travel to the first node of Ranvier and trigger action potentials.
What happens when stimulus strength increases?
As stimulus (e.g., pressure) increases, the receptor potential increases, causing more action potentials. However, this increase plateaus at a point—stronger stimuli eventually stop producing more signals. This prevents overstimulation while still allowing light-touch sensitivity.
Is this stimulus-to-signal behavior true for all receptors?
Yes. Most receptors in the body follow this pattern: stronger stimulus → stronger receptor potential → higher action potential frequency, until a saturation point is reached.
What is adaptation in sensory receptors?
Adaptation is the process by which sensory receptors reduce their response over time when a stimulus remains constant. They start by responding strongly, then slow down or stop entirely.
Which receptors adapt quickly?
Rapidly adapting receptors include Pacinian corpuscles (stop in <1 sec), hair receptors (stop in ~1 sec), and some joint and muscle receptors (take longer but still adapt).
Which receptors adapt slowly or not at all?
Slow or non-adapting receptors include baroreceptors (blood pressure sensors), pain receptors, and chemoreceptors (e.g., those detecting oxygen or carbon dioxide). Baroreceptors may never fully adapt.
How does the Pacinian corpuscle physically adapt?
The Pacinian corpuscle is viscoelastic. When pressure is applied, its layers move and transmit the force to the nerve fiber, creating a receptor potential. Then, fluid within the layers redistributes the force, reducing pressure on the nerve tip and stopping the response—even if pressure remains.
How does the Pacinian corpuscle electrically adapt?
Over time, the nerve fiber inside the Pacinian corpuscle undergoes accommodation. Sodium channels start to close with prolonged stimulation, preventing new signals from being generated. This is an internal electrical mechanism of adaptation.
What are the two ways the Pacinian corpuscle adapts?
- Physical adaptation through viscoelastic spread of pressure in connective layers. 2. Electrical adaptation via accommodation where sodium channels stop working due to prolonged stimulation.
What are tonic receptors?
Tonic receptors are slowly adapting receptors that keep firing as long as the stimulus is present. They are important for continuous monitoring of the body’s state and are used in sensing muscle tension, body position, blood pressure, and chemical levels.
Examples of tonic receptors?
Examples of tonic (slowly adapting) receptors include: muscle spindles, Golgi tendon organs, pain receptors, baroreceptors, and chemoreceptors (oxygen/CO₂ detectors).
What are phasic receptors?
Phasic receptors are rapidly adapting receptors that respond only to changes in stimulus. They fire when a stimulus starts or ends, and then stop. They are specialized for detecting movement, vibration, or changes.
Other names for phasic receptors?
Phasic receptors are also called: rate receptors, movement receptors, or rapidly adapting receptors.
Why are phasic receptors useful?
Phasic receptors are great for detecting changes or motion. For example, Pacinian corpuscles respond when pressure starts or stops but ignore constant pressure. They help detect quick changes in the environment.
Why are phasic receptors important for prediction?
Phasic receptors, like those in the vestibular system and joints, detect movement speed. This helps the brain predict body position during activities like running, allowing coordinated muscle action and balance.
