CNS/Sensory III Flashcards
What is sensation?
Awareness of sensory stimulation
What is perception?
The understanding of a sensation’s meaning
What is the law of specific nerve energies?
Regardless of how a sensory receptor is activated, the sensation felt corresponds to that of which the receptor is specialized.
Give an example of the law of specific nerve energies.
Rub your eyes hard and you will see light.
What is the law of projection?
Regardless of where in the brain you stimulate a sensory pathway, the sensation is always felt at the sensory receptor’s location.
The phenomenon of phantom limb pain corresponds to which law of perception? Explain why.
Law of projection. The axons from the original limb try to innervate something else, so they get activated by the wrong thing, creating the sense of phantom pain where the limb used to be
What is labeled-line code?
It is the notion that the brain knows the modality (class of stimulus) and location of every sensory afferent.
What is an exception to labeled-line code?
In certain instances dealing with pain - this is referred pain.
Name the 5 steps of sensory receptor functioning.
- Stimulus energy is received.
- The corresponding receptor membrane reacts with the stimulus energy
- The energy is used for transduction of ion channels
- The ion channels activate
- The signal is sent to the CNS via afferent neurons.
Stimulus energy gets converted into […]
Afferent activity
Name and explain the steps involved in the conversion of stimulus energy into afferent activity.
- Start with stimulus energy
- Membrane depolarization takes place, affecting receptor potential.
- If the threshold is met, action potentials are produced.
- Action potentials are propagated along the body to the brain.
- Neurotransmitters are released.
What happens if the membrane depolarization caused by stimulus energy doesn’t meet the threshold for an action potential?
No action potential will be fired. So even though something is touching you, for example, you won’t feel it.
What are the 3 levels of stimulus intensity?
Subthreshold, weak, strong
Describe how a subthreshold stimulus intensity will affect…
a) The magnitude of receptor potential
b) The frequency of action potentials
c) The magnitude of neurotransmitters release
a) The magnitude of the receptor potential will be small
b) No action potentials will be sent out
c) No neurotransmitter release
Describe how a weak stimulus intensity will affect…
a) The magnitude of receptor potential
b) The frequency of action potentials
c) The magnitude of neurotransmitters release
a) Medium receptor potential
b) A few action potentials released
c) Some neurotransmitter released
Describe how a strong stimulus intensity will affect…
a) The magnitude of receptor potential
b) The frequency of action potentials
c) The magnitude of neurotransmitters release
a) High magnitude of receptor potential
b) High frequency of action potential
c) High magnitude of neurotransmitters released
Explain the purpose of adaptation of afferent response.
The majority of afferents show adaptation, which allows us to be sensitive to changes in the sensory input.
How does adaptation of afferent response work? Compare non-adapting, slowly adapting, and rapidly adapting
In non-adapting afferents, the action potential frequency is constant and is slow to respond to change. In slowly adaptive afferents, there are moderate stimulus changes and some stimulus intensity. In rapidly adaptive afferents, it sends action potentials when there are fast stimulus changes. ??
What is a receptive field?
The region in space that activates a sensory receptor or neuron (afferent).
The response across a receptor field can be described as […]. Explain why.
Graded, because the location of the stimulus will be strongest at the direct area of contact, but the receptors around that one will got a smaller afferent response will less spikes.
Overlapping receptive fields produce […]
A population code
What is a population code?
It is when the body realizes that there’s a stimulus across several afferents. This allows the body to tell which receptive fields have been activated and how much.
What is stimulus acuity?
The ability to differentiate one stimulus from another on a given site.
Compare the relationship between acuity and location based on acuity for lips vs back.
For lips, since the receptor field size is smaller, acuity is higher. For back, since the receptor field size is larger, acuity is lower.
