General Senses Flashcards
What does receptive field mean?
Area monitored by single sensory neuron
What does receptor specificity mean?
Each receptor prefers a specific type of stimulus (mechanical, chemical, temperature).
How does a receptor respond to a stimulus?
- Stimulus opens chemically or mechanically gated channels and causes a graded potential at the trigger zone.
- Undergoes transduction
- Reaches a threshold, then produces an action potential.
What is a threshold?
Minimum stimulus intensity require to activate a receptor.
What is transduction?
Conversion of stimulus into information that can be transformed by nervous system.
What are examples of action potential patterns?
- Tonic: continuous action potential that increase/decrease in response to strength of stimulus
- Phasic: silent, AP occurs in presence of stimulus
- Tonic phasic
What are the four classes of receptors?
- Thermoreceptors: Temperature.
- Chemoreceptors: Chemical or chemical concentration.
- Mechanoreceptors: Physcial disortion of plasma membrane
- Nociceptors: Actual or potential tissue damage.
Describe thermo receptors
- Monitors non-painful temperature and helps to maintain stable body temperature.
- Located in the skin and CNS (hypothalamus and spinal cord).
Describe chemo receptors
- Detect small changes in the concentration of specific chemical or pH.
- Respond to stimuli that physically distort plasma membrane.
Describe nociceptors
- Detect actual or potential tissue damage.
- Has a large receptive field, why it is difficult to determine exact source of painful sensation
- Discharge action potential in response to: extreme temperature, mechanical damage, dissolved chemicals.
What is stimulus location?
Destination of sensory information in central nervous system provides information about where sensory information originated from the body.
What is stimulus intensity?
Number of receptors activated and frequency of discharge of action potentials.
What is stimulus duration?
How long does the sensory neuron discharge action potentials?
What does adaptation refer to and what are the 2 types?
- Change in response to constant stimulus.
- Peripheral and central
What is peripheral adaptation?
- Involves change in activity of receptor.
- Decreases amount of information in central nervous system
What is central adaptation?
- Involves change in within central nervous system
- Decreases amount of information in cerebral cortex
What are the 3 classes of mechanoreceptors?
- Tactile receptors: touch, pressure, vibration.
- Baroreceptor: minor changes in pressure.
- Proprioceptor: position, stretch and tendon.
Can you name one specific example of a mechanoreceptor found in skin
Muscle spindles (increases skeletal muscle stretch).
Where are muscle spindles and Golgi receptors found.
Muscles spindles: skeletal muscle tissues, they run parallel to muscle fibers.
Golgi tendon organs: collagen fibers of tendons and joint capsules.
What type of stimulus do muscle spindles and Golgi tendon organs detect?
The type of stimulus they detect is change in muscle stretch/length.
What shape are sensory neurons and where is the receptor, axon and cell body located?
Receptors are located on dendrites of sensory neurons. Cell body is located in the dorsal root ganglion.
Axon enters spinal cord via dorsal root.
What is the first order neuron?
Is the receptor on dendrites of sensory neuron.
What is the second order neuron?
Relays sensory information from spinal cord to thalamus.
What is the third order neuron?
Relays sensory information from thalamus to
primary somatosensory cortex.
What happens when action potentials reach the spinal cord?
Trigger reflex and may also be relayed to the cerebral cortex.
What is the spinothalamic pathways?
-Anterior and lateral spinothalaic pathways
-Dorsal column medial meniscal pathways
1) Peripheral tissues
Receptors on dendrites of sensory neurons
First order neurons
2) Spinal Cord
Second order neurons
3) Thalamus
Third order neurons
What is the role of primary somatosensory cortex in spinothalamic pathways?
-Sends information to primary somatosensory cortex.
Posterior Parietal Cortex
-Integrates somatosensory information with particularly visual system.
-Perception & interpretation of spatial relationships.
-Accurate body image.
-Learning tasks that involve accurate coordination of body in space.
What is the difference with spinocerebellar pathways?
- Only first and second order neurons.
- Second order neurons may or may not cross the midline.
- No thalamus.
- Terminates in cerebellum instead of somatosensory cortex.
What does somatic sensation below neck involve?
- Anterior and lateral spinothalamic pathways.
- Dorsal column medial lemniscal pathway
- Spinocerebellar pathway.
What does somatic sensation above the neck involve?
Trigeminal nerve (cranial nerve V).
