BIO 360 - Exam 2 - Chapter 10 Sensory Processing SP 2023 PowerPoint Flashcards
The post-synaptic neuron can integrate the input of many
presynaptic neurons. Concepts of ______ and ______ summation.
spatial / temporal
The combination of several nearly simultaneous graded potentials is called spatial summation. The word spatial {spatium, space} refers to the fact that the graded potentials originate at different locations (spaces) on the neuron.
Summation that occurs from graded potentials overlapping in time is called temporal summation {tempus, time}.
Coded by number of receptors activated and frequency
of action potentials is called ______?
Coded by duration of a train of action potentials is called ______? - Some receptors can adapt or cease to respond.
intensity / duration
Fig. 10.6 Coding for stimulus intensity and duration
For individual sensory neurons, intensity discrimination begins at the receptor. If a stimulus is below threshold, the primary sensory neuron does not respond. Once stimulus intensity exceeds threshold, the primary sensory neuron begins to fire action potentials. As stimulus intensity increases, the receptor potential amplitude (strength) increases in proportion, and the frequency of action potentials in the primary sensory neuron increases, up to a maximum rate.
Figure 8-27a & Figure 8-27b
Figure 8-28a, 8-28b
What is the difference between no summation and summation causing an action potential?
No summation: two graded potentials will not cause an action potential if they are apart in time.
Summation causing an action potential: if two sub-threshold potentials arrive at the trigger zone within a short period of time, they may sum and create an action potential.
Figure 8-29a
What is presynaptic inhibition?
a modulatory neuron synapses on one collateral of the presynaptic neuron and selectively inhibits one target.
Table 10.1 Information processing by the sensory division
Somatic stimuli and visceral stimuli.
Somatic stimuli: muscle length & tension, proprioception.
Visceral stimuli: blood pressure,
Table 10.2 Types of Sensory Receptors
Chemoreceptors: Oxygen, pH, various organic molecules such as (glucose).
Mechanoreceptors: Pressure (baroreceptors), cell stretch (osmoreceptors), Vibration, acceleration, sounds
Thermoreceptors: Varying degrees of heat
Photoreceptors: Photons of light
Sensory Pathways
Stimulus as physical energy –> sensory receptor acts as a ______.
transducer
Sensory Transduction
- Stimulus energy converted into information processed by CNS.
- Ion channels or second messengers initiate membrane
potential change - ______ ______: Preferred form of stimulus
- ______ : Minimum stimulus
- ______ ______: Change in sensory receptor membrane potential.
Adequate stimulus / Threshold / Receptor potential
Fig. 10.1 Simple, complex, and nonneural sensory receptors
S______ r______ are neurons with free nerve endings.
Most s______ s______ r______ are cells that release neurotransmitter onto sensory neurons, initiating an action potential.
Simple receptors / special senses receptors
Receptive fields are different in different sensory ______!
Vision/photoreceptors – L______ / W______.
Audition/mechanoreceptors – F________ of Pr______ Wa______ . Olfaction/chemoreceptors – range of molecules.
modalities
light wavelength; frequency of pressure waves; range of molecules
Fig. 10.2 Receptive fields of sensory neurons: Two-Point Discrimination
Convergence – multiple primary to single 2nd sensory neuron = NO 2pt convergence
1:1 primary to secondary sensory neurons - two separate touches = 2pt convergence
In addition, sensory neurons of neighboring receptive fields may exhibit convergence, in which multiple presynaptic neurons provide input to a smaller number of postsynaptic neurons (Fig. 10.2). Convergence allows multiple simultaneous subthreshold stimuli to sum at the postsynaptic (secondary) neuron.
When multiple primary sensory neurons converge on a single secondary sensory neuron, their individual receptive fields merge into a single, large secondary receptive field, as shown in Figure 10.2a. There is no two-point convergence - one signal goes to the brain.
In contrast, more sensitive areas of skin, such as the fingertips, have smaller receptive fields, with as little as a 1:1 relationship between primary and secondary sensory neurons (Fig. 10.2b). In these regions, two pins separated by as little as 2 mm can be perceived as two separate touches.There is two-point discrimination - two signals go to the brain.
Fig. 10.5 Lateral inhibition
What is Lateral inhibition?
Lateral inhibition: capacity of excited neurons to reduce the activity of their neighbors.
The response of the primary sensory neurons A, B, and C are proportional to the intensity of the stimulus in each receptor field. Secondary sensory neurons inhibit secondary neurons A and C, creating greater contrast between B and its neighbors.
Fig. 10.15 Anatomy Summary . . . The ear
