Exam #6: Introduction to Sensory Flashcards
Define proprioceptor.
Receptors that provide a sense of self i.e. information about joint angles, muscle length, and muscle tension
Define adequate stimulus.
Under normal circumstances, a receptor is only affected by a certain threshold of a specific stimulus
Define nociceptor.
Pain receptor
Define sensory modality.
Different types of sensory stimuli e.g. vision, hearing, taste, smell, touch, pain, temperature, itch
Define receptive field.
Region of tissue within which a stimulus can evoke a change in the firing rate of a neuron
Define graphesthesia & agraphesthesia.
Sense through which figure or numbers drawn on skin are recognized
Define sterognosis & asterognosis.
Ability to recognize objects through touch alone
What is the difference between a receptor potential & an action potential?
Receptor potential= graded potentials produced by signal transduction of a sensory stimulus
Action potential= depolarization once threshold has been reached
**Receptor potentials of a sufficient strength will trigger action potentials
How does the nervous system can code for the “what” of a sensory stimulus?
Labeled line principle= chain of connected neurons from sensory receptor to brain area that perceives the stimulus
How does the nervous system can code for the “where” of a sensory stimulus?
Receptive field
How does the nervous system can code for the intensity of a sensory stimulus?
1) Increase frequency of nerve firing
2) Increase number of nerves firing
How does the nervous system can code for the duration of a sensory stimulus?
On/off signaling with continuous firing during stimulation
What is adaptation of a receptor?
When maintained/ constant stimulus leads to a decrease in firing in the associated sensory nerve over time
What is the difference between phasic, tonic, rapidly adapting, & slowly adapting? Give an example of somatosensory receptors of each type of adaptation.
Tonic= slowly adapting & signal intensity/ duration of stimulus
- E.g. merkel’s disk (detects steady pressure)
Phasic= rapidly adapting, signals onset & offset
- Pacinian corpuscle (detects rapid changes in stimulus)
How are nerve fibers classified?
Roman numeral (sensory only) & letter schemes (motor & sensory): I-IV & A-C
- I-III/ A & B are myelinated
- IV/C are NOT myleinated
State which type of nerve fibers is fastest & slowest.
Fastest= I/ A-alpha Slowest= IV/ C
Which type of nerve fiber conducts action potentials at 100 m/s, 50 m/s, 20 m/s, 1 m/s?
100= I/Aa 50= II/ Ab 20= III/Ad 1= IV/ C
How could you measure spatial resolution in the somatosensory system?
Two-point discrimination test
What is “two-point discrimination”? Which areas of the body show the best discrimination? The worst?
Two-point discrimination is a test of tactile acuity
- Good discrimination at lips and finger tips
- Poor on back & calf
List the receptors involved in proprioception. What is the difference between these receptors?
- Joint receptors
- Muscle spindles & golgi tendon organs
- Skin tactile receptors
What kinds of information are carried by the dorsal column and anterior column systems?
DC/ML=
1) Proprioception
2) Two-point discrimination
3) Vibration
Anterolateral i.e. Spinothalamic=
1) Pain
2) Temperature
Where does information in the dorsal column & anterior column cross the midline?
DC/ML= midline in the brainstem–decussation of the medial lemniscus
Anterolateral i.e. Spinothalamic= spinal cord
What kinds of deficits are associated with damage to each system, dorsal column and anterior column?
DC/ML= deficits in:
1) Proprioception
2) Two-point discrimination
3) Vibration
Anterolateral i.e. Spinothalamic= deficits in:
1) Pain
2) Temperature
What is the location of the somatosensory cortex? How is the somatosensory cortex organized?
- Parietal lobe (post-central gyrus)
- Broadmann 3,1,2
Medial= foot, leg, & genitals Lateral= face, trunk, arms
