The Somatic Sensory System Flashcards
Describe a general pathway of a sensory system.
Stimuli –> Selective receptor structures –> intracellular amplification of signal –> neuronal signal to CNS
Where does the CNS receive touch and proprioception information?
From sensory nerves
How does the CNS generate movements after receiving external stimuli information?
By sending signals to muscles via motor nerves
Describe common features of sensory systems (sensory coding).
- Sensor organs are filters - highly selective and sensitive
- Transduction - stimulus energy transformed into neural electrical activity
How do cells respond to stimuli?
They respond to weak stimuli of one particular type (modality) and only respond to small portion of that stimulus.
What is a simple receptor?
Neurons with free nerve endings (somatosensory)
What is a complex receptor?
Nerve endings enclosed in connective tissue capsules.
What are specialized sense receptors?
These are non-neural and release NT onto sensory neurons
How are neurons classified?
By structure, location, types of stimuli they respond to
What are graded potentials?
These are changes in membrane potential that vary in size, as opposed to all-or-none
Where and how do graded potentials occur? How long do they last?
- Tend to occur in dendrites or soma of neuron
- Arise from the summation of the individual actions of ligand-gated ion channel proteins and decrease over time and space
- Size and duration are dependent on size and duration of stimulus
- Decay with time and distance
What is depolarization in terms of a graded potential?
When the graded potential is just underneath or barely meets the threshold
What is an action potential in terms of a graded potential?
An action potential is when the graded potentials exceeds a threshold.
What is hyperpolarization in terms of a graded potential?
It is when the graded potential fails to meet the threshold.
Action potentials are created when graded potentials exceed a threshold. Describe how graded potentials might also exceed the threshold in order to create an action potential.
When graded potentials, such as depolarization and hyperpolarization occur at the same time, sometimes it can be enough to cause a graded potential to exceed the threshold and create an AP.
What is the definition of summation in terms of physiology?
The additive effect of several electrical impulses on a neuromuscular junction (junction between a nerve cell and a muscle cell)
Summation can be either…?
Temporal or spatial?
Describe spatial summation in three steps.
- Simultaneous stimulation by several presynaptic neurons
- EPSPs spread from several synapses to axon hillock
- Postsynaptic neuron fires
What is an EPSP?
Excitatory post-synaptic potential
Makes it easier for the neuron to fire an AP
What is an IPSP?
Inhibitory post-synaptic potential
When the resulting change in membrane voltage makes it more difficult for the cell to fire an AP (lowering the firing rate)
Describe temporal summation in three steps.
- High frequency stimulation by one presynaptic neuron
- EPSPs spread from one synapse to axon hillock
- Postsynaptic neuron fires
What are the somatic senses?
Touch, proprioception, temperature, and nociception
What is proprioception?
The sense of body position perceived on both conscious and unconscious levels
What is the organ of perception for position sense?
The sensory cortex of the brain
