2. General Principles of Sensory Physiology Flashcards
Interaction between sensory system and motor system
Sensory receptors in the PNS generate an impulse
The CNS interprets the impulse
The PNS stimulates a response
Sensory receptors
Some specialized structures activated by stimuli and convert a stimulus into neuronal activity
Types of sensory receptors
- Endings of afferent neurons (somatosensory and olfactory systems)
- Specialized epithelial cells adjacent to an afferent neuron (visual, taste, and auditory systems)
- Specialized structure associated with nerve terminals (Pacinian corpuscles)
Simple receptors
Neurons with free nerve endings, work on somatosensory and olfactory systems
Complex neural receptors
Nerve endings enclosed in connective tissue capsules, Pacinian corpuscles
Special senses receptors
Cells that release neurotransmitter onto sensory neurons, initiating an action potential
5 types sensory receptors
Mechanoreceptors, photoreceptors, chemoreceptors, thermoreceptors, nociceptors
Mechanoreceptors
For touch, is a pacinian corpuscle and located on the skin
For audition, is a hair cell and located in the organ of corti
For vestibular, is a hair cell locating on macula, semicircular canal
Photoreceptors
For vision, rods and cones are the receptors and located on the retina
Chemoreceptors
For olfaction: olfactory receptors on olfactory mucosa.
For arterial Po2 on carotid and aortic bodies.
Fo pH of CSF on ventrolateral medulla
Thermoreceptors
For temperture, receptors are cold receptors and warm receptors, on skin.
Nociceptors
Detect stimuli causing tissue damage, can be thermal, mechanical or polymodal, located on skin.
Receptor potential vs. action potential
Receptor potential = graded, non-propagated
Action potential = hyperpolarizing or depolarizing
Sensory transduction
- Stimulus -> ion channel opening
- Current –> receptor potential
- Depolarization -> voltage gated sodium channels, action potentials
- Propagation -> NT release
- Transmission to CNS through sensory afferent neurons (1st, 2nd, 3rd, and 4th order)
Sensory unit
primary sensory neuron with all sensory receptors (endings or associated sensory receptor cells).
The smallest unit of sensory response.
Receptive field
an area of the body surface that when stimulated results in a change in firing rate of a sensory neuron.
What determinates the size of receptive field of a sensory neuron?
Terminal size and associated cells; Convergence
Receptive field variation in size
The smaller the receptive field, the more precisely the sensation can be localized or identified.
The higher the order of the CNS neuron, the more complex the receptive field.