Term
Sensory Pathways - Sensory systems receive information from the environment via sensory receptors in the periphery and transmit this
information through a series of neurons and synaptic relays to the CNS. |
|
Definition
|
|
Term
| Activated by stimuli in the environment and the basic function is to convert a stimulus into electrochemical energy. |
|
Definition
|
|
Term
| Stimuli --> Membrane conductance change --> generator potential --> Action potential |
|
Definition
| Fundamental Components of All Sensory Systems |
|
|
Term
| The usual and appropriate stimulus for a receptor and for which the receptor has the lowest threshold. |
|
Definition
|
|
Term
The change in membrane potential when a type of
stimulus excites a sensory receptor. |
|
Definition
| Receptor (generator) potential |
|
|
Term
| When the receptor potential rises above the threshold for eliciting action potentials in the nerve fiber innervating the sensory receptor, then action potentials begin to appear. |
|
Definition
| Initiation of action potentials |
|
|
Term
True or False: The longer the duration of the stimulus intensity, the more rapid the action potential.
True or False: The higher the stimulus intensity with the same duration, presents AP faster. |
|
Definition
|
|
Term
| Sensory receptors concerned with the external environment (includes all “five senses”). |
|
Definition
|
|
Term
| Sensory receptors concerned with the internal environment (e.g., temperature, chemical composition, stretching of tissue). |
|
Definition
|
|
Term
| Sensory receptors concerned about the position of the body in space (e.g., muscle spindles, joint receptors). |
|
Definition
|
|
Term
| Detect mechanical deformation of the body’s surface. |
|
Definition
|
|
Term
| Activated by changes in temperature on the surface of the body. |
|
Definition
|
|
Term
| Activated by noxious stimuli |
|
Definition
|
|
Term
| Detect light on the retina of the eye. |
|
Definition
|
|
Term
| Detect taste in the mouth, smell in the nose. |
|
Definition
|
|
Term
Mechanoreceptors
- Pacinian Corpuscles
Subcutaneous layers of nonhairy skin & in muscle
Pressure, vibration
- Meissner’s Corpuscles
Fingertips, nonhairy skin
Tactile discrimination
- Hair Follicle Receptors
Hairy skin
Detect velocity & direction of movement across skin
- Merkel’s Disks
Nonhairy skin
Detect vertical indentations of skin
- Ruffini’s Corpuscles
Dermis of hairy skin & in joint capsules
Detect stretch & joint rotation
- Tactile Disks
Hairy skin
Similar to Merkel’s Disks |
|
Definition
|
|
Term
| True or False: A nerve cell is influenced by a transmitter, while a sensory cell is influenced by a stimulus. |
|
Definition
|
|
Term
Present in skin and some mucous membranes.
Mechanoreceptors that detect pressure and vibration |
|
Definition
|
|
Term
The Pacinian Corpuscle - Pacinian corpuscles are present in the skin and some mucous membranes. They are mechanoreceptors, responding to pressure, or any
kind of mechanical stimulus causing a deformation of the corpuscle. |
|
Definition
|
|
Term
| True or False: A tactile stimulus activates Na+ influx producing a depolarizing receptor potential and initiation of an action potential. |
|
Definition
|
|
Term
Encoding of Stimulus Properties
The sensory receptor is sensitive to a form of physical energy – mechanical, thermal, chemical, or electromagnetic. The receptor transforms the stimulus energy into electrochemical energy, thereby establishing a common language for all sensory
systems. This conversion process is called stimulus transduction. Stimulus information is then represented in a series of action potentials by a process called neural encoding. The four fundamental attributes of sensory information - modality,
intensity, duration, and location-are each related to a separate stimulus feature, and codes exist for each. |
|
Definition
|
|
Term
| Different forms of energy are transformed by the nervous system into different sensations or sensory ??? |
|
Definition
|
|
Term
Intensity or magnitude of a sensation depends on the strength of the stimulus. The intensity function of the primary afferent fiber describes the relationship
between stimulus intensity and the rate or number of evoked action potentials.
a. Frequency code of stimulus intensity
The number of action potentials evoked per unit time is a function of the intensity of sensation.
b. Population code of stimulus intensity
A stronger stimulus also activates a greater number of receptors, so that the intensity of a stimulus is also encoded in the size of the responding receptor population. |
|
Definition
|
|
Term
Duration
The duration of a sensation is defined by the relationship between the stimulus intensity and the perceived intensity. When a continuous sensory
stimulus is applied, the sensory receptors respond at a high impulse rate at first and then at a progressively slower rate until finally many of them no longer respond. The perceived stimulus intensity becomes subthreshold with time, and the sensation is lost. This decrease in intensity is called sensory
adaptation.
a. Fast adaptation (Rapidly adapting)
The action potential frequency falls rapidly and then maintains a constant slow rate that does not show further adaptation. (Detect change in stimulus strength – Phasic or dynamic receptors).
Examples - Meisnner’s and Pacinian corpuscles, and hair follicles.
b. Slow adaptation (Slowly adapting)
As the receptor potential declines the interval between the action potentials increases correspondingly. (Detect continuous stimulus
strength – Tonic or static receptors). Examples - Merkel’s disks, Ruffini endings, nociceptors. |
|
Definition
|
|
Term
Location
Stimulus location is encoded by the receptive field of sensory neuron and may be enhanced by lateral inhibition.
a. Receptive fields
All sensory receptors have a receptive field, the space within the receptive sheet in which the sensory receptor is located and in which it transduces stimuli by changing the firing rate of a sensory neuron. The firing rate can be increased or decreased; therefore, receptive fields are described as excitatory or inhibitory.
b. Two-point threshold
The ability to perceive two nearby stimuli as distinct is quantified by determining the minimum distance between two detectable stimuli. |
|
Definition
|
|
Term
| Used for transmitting somatosensory information about discriminative touch, pressure, vibration, two-point discrimination, and proprioception. |
|
Definition
|
|
Term
| Used for transmitting somatosensory information about pain, temperature, and light touch. |
|
Definition
|
|
Term
The Somatosensory Homunculus
The fourth-order neurons located in the somatosensory cortical regions, S1 and S2, receives input from the third-order neuron integrating the complex information, and is represented in the map of the body, the somatosensory homunculus. |
|
Definition
|
|
