Introduction Flashcards
If you want to build a sensing machine, what would you need?
- Something that receives and translates information into the language of the machine → sensory receptors and axons that translate the energy of the stimulus into electrical signals.
- Something that transports information for processing → axons that transport the signal to the series of relay nuclei.
- Something that integrates and processes information → interneurons and local circuitry in nuclei that process the signal.
What’s the difference between non-sensory and sensory neurons?
- Non-sensory neurons can generate an action potential through EPSP or IPSP
- Sensory neurons have a different morphology and respond differently. Here a change in light/dark causes a change in membrane potential which leads to the release of neurotransmitters.
What are mechanical receptors?
- To what do they respond?
- What is their reaction?
- Receptors that respond to touch and proprioception, hearing and balance.
- The physical stretch or tension on the receptor deforms the membrane and opens the channels.
What are chemical receptors?
Receptors that respond to pain, itch, small, taste. Here a chemical binds to the receptor.
What are photoreceptors?
- To what do they respond?
- What is their reaction?
- Receptors that respond to vision via photoreceptors in the retina.
- It results in the change in conformation of a photosensitive protein.
What are thermal receptors?
- To what do they respond?
- What is their reaction?
- Respond to temperature.
- Receptor activation results in the change of postsynaptic potential.
This picture depicts the different mechanoreceptors that are located in the skin.
Explain how Meissner corpuscle mechanoreceptors respond to the sensing of a stimulus.
Meissner corpuscle → responds to light touch and are able to rapidly adapt to stimuli by firing high frequency action potentials, therefore these receptors are very sensitive. But they are less accurate in sensing stimuli.
This picture depicts the different mechanoreceptors that are located in the skin.
Explain how Merkel cells respond to the sensing of a stimulus.
Merkel cells are the most accurate in sensing stimuli (shape, intensity of stimulus)
This picture depicts the different mechanoreceptors that are located in the skin.
Explain how Ruffini corpuscle mechanoreceptors respond to the sensing of a stimulus.
Ruffini corpuscle receptors are less sensitive and mostly respond to sustained pressure, but show little adaptation.
This picture depicts the different mechanoreceptors that are located in the skin.
Explain how Pacinian corpuscle mechanoreceptors respond to the sensing of a stimulus.
Pacinian corpuscle receptors react differently, but react very well to the stimulus (very small changes in stimuli, but not able to distinguish shape changes and fine details).
What is proprioception?
It is the sense of self-movement and body position → the position of the muscles and joints of the body.
Why is the location of receptors important?
In order to respond appropriately to a stimuli, it is Important to know the position or location of the stimuli.
- What is a topographic map?
- What is retinotopy?
- A topographic map is the ordered projection of a sensory surface (e.g. retina or skin) or an effector system (e.g. musculature), to one or more structures of the central nervous system.
- Retinotopy is the mapping of the visual input from the retina to neurons, particularly those neurons within the visual stream.
What determines the spatial resolution of a stimulus?
The size of the receptive field and the density of receptors
Why is the intensity of the stimulus important?
Receptors have a certain sensory threshold (which is determined by the sensitivity of the receptors). The intensity of the stimulus determines whether an action potential is triggered.
What happens when there’s a change in the intensity of the stimulus?
This results in a change in membrane potential, which also affects the chances of generating an action potential.
What happens when a receptor potential is achieved, but this doesn’t result in an action potential?
Then information will be lost, because the threshold for action potential is not reached. Cells can react, but the brain cannot.
There are different responses to a stimulus:
- Slowly adapting responses
- Rapidly adapting responses
- Adaptation
Describe these responses.
How does the stimulus change in time (how does it detect the change in stimulus)?
- Slowly adaptic responses → changes in stimulus are coded in frequency. Here they continue in responding to the stimulus.
- Rapidly adapting responses → only respond to changes in stimulus intensity and thus fire action potentials at the start (and end) of the stimulus.
- Adaptation → a constant stimulus fades from consciousness (habituation).
Sensory systems are able to detect contrasts and motion
What are sensory systems able to detect?
Contrasts and motion
What is parallel processing?
The ability of the brain to simultaneously process incoming stimuli of differing quality.
What is convenient about parallel processing of stimuli?
It increases the speed of processing
Is topographical representation maintained during parallel processing?
Yes, in the brain the orderly spatial relationship between the distribution of neural receptors in an area of the body and the related distribution of neurons representing the same functions in cortical sensory region of the brain is maintained during parallel processing.
What occurs during parallel processing?
Decussation → the cross-over of sensory information to the opposite hemisphere.
What else is important during parallel processing?
Feedback connections/descending projections, to modulate/process the information.
