Flashcards in Costanzo Neurophysiology - General Sensory Systems Deck (25):
What type of cells are sensory receptors?
Specialized epithelial cells
Occasionally primary afferent neurons - i.e. olfactory chemoreceptors
What do sensory receptors transmit?
Transduce environmental signals into neural signals
What environmental signals can be detected by sensory receptors?
1. Mechanical force
What are the 4 types of sensory transducers?
What are 5 examples of mechanoreceptors?
1. Pacinian Corpuscles
2. Joint receptors
3. Stretch receptors
4. Hair cells in auditory and vestibular systems
5. Baroreceptors in carotid sinus
What are some examples of photoreceptors?
Rods and cones in of the retina
What are 4 examples of chemoreceptors?
1. Olfactory receptors
2. Taste receptors
4. Carotid body O2 receptors
What detects extremes of temperature and pain?
What is a receptive field? What makes an excitatory or inhibitory receptive field?
Area of the body, that, when stimulated, changes the firing rate of a sensory neuron. If the firing rate of the sensory neuron is increased the receptive field is excitatory. If the firing rate of the sensory neuron is decreased the receptive field is inhibitory.
What are the steps in initial sensory transduction?
1. Stimulus arrives at sensory receptor
2. Ion channels are opened in the sensory receptor
3. Change in membrane potential achieved
What is the typical ion flow in a sensory receptor? What is the exception?
Usually the current is inward = depolarization of the receptor
Exception is photoreceptor, light decreases inward current and causes hyperpolarization
What happens to the membrane potential if the receptor potential is depolarizing? How are receptor potentials graded?
It brings the membrane potential closer to threshold. If the receptor potential is large enough, the membrane potential will exceed threshold and an action potential will fire in the sensory neuron.
Receptor potentials graded in size depending on the size of the stimulus.
How are sensory receptors different in terms of adaptation?
Slowly adapting/tonic receptors
Rapidly adapting/phasic receptors
What are 3 examples of slowly adapting/tonic receptors?
How do slowly adapting/tonic receptors behave?
Respond repetitively to prolonged stimulus
Detect a steady stimulus
What are 2 examples of rapidly adapting/phasic receptors?
How do rapidly adapting/phasic receptors behave?
Show a decline in AP frequency with time in response to a constant stimulus
Primarily detect onset and offset of a stimulus
Potentially, how many neurons can be involved in an afferent sensory pathway?
What are first order neurons in an afferent sensory pathway? What do they do? Where are the cell bodies located?
Primary afferent neurons that receive the transduced signal and send the information to the CNS.
Cell bodies are located in the DRG or spinal cord ganglia.
Where are the second order neurons in an afferent sensory pathway located?
located in spinal cord or brain stem
What info do the second order neurons in an afferent sensory pathway receive?
Info from one or more primary afferent neurons in relay nuclei and transmit it to the thalamus
Where do the axons from second order neurons in an afferent sensory pathway go?
May cross the midline in a relay nucleus in the spinal cord before they ascend to the thalamus.
Sensory information originating on one side of the body ascends to a contralateral thalamus
Where are third order neurons in an afferent sensory pathway located? From here, where is the information transmitted?
In relay nuclei of thalamus.
Encoded sensory information ascends to the cerebral cortex.
Where are the fourth order neurons in an afferent sensory pathway located?
In appropriate sensory area of the cerebral cortex