Special Senses Flashcards
What is the sensory system?
Portion of the nervous system composed of
1. Sensory receptors
2. Nerve pathways that conduct sensory info from receptors to CNS
3. Parts of the brain that process sensory information
What are the two types of sensory receptors?
- One with a receptor membrane
- One with a receptor cell, which releases vesicles containg neurotransmitters
In response to a stimulus, what do receptors generate?
Graded potentials that can initiate APs, which travel into CNS
What is an adequate stimulus?
A form of energy to which a sensory receptor is most responsive
What are the major classes of sensory receptors? (5)
- Chemoreceptors (O2, CO2, glucose)
- Mechanoreceptors (pressure, cell stretch, sound, vibration)
- Photoreceptors (photons of light)
- Thermoreceptors (degrees of heat)
- Nociceptors (pain)
What are the four properties of all stimuli?
- Modality
- Location
- Intensity
- Duration
What is modality?
The type of stimulus; there is a specialized receptor for each type of stimulus modality
What is location?
Identified by receptive fields
What is lateral inhibition?
- Increase of contrast between active receptive fields and inactive neighbours
- Exact localization which increases the brain’s ability to localize the input
What is intensity?
Coded by number of receptors activated, and frequency of APs
What is duration?
Coded by duration of APs
What is the difference between phasic and tonic receptors?
Phasic Receptors: Quick to respond, but adapt rapidly to constant stimuli, sensitive to changes.
Tonic Receptors: Sustain a response to constant stimuli, less prone to rapid adaptation, maintain sensitivity over time.
What is somatic sensation?
Sensation from the skin, skeletal muscles, bones, tendons, and joints initiated by a variety of sensory receptors
What is the somatic sense pathway?
What does viscual perception require? (2)
- The eye; an organic which focuses the visual image and responds to light
- Neural pathways, which interpret the signals and transform the visual image into a pattern of graded and action potentials
What are major components of the human eye? (3)
- Optic disk (blind spot): where neurons join into the optic nerve
- Macula: round area at the center of retina, at the back of the eyeball
- Fovea: the center part of the macula, which is the region of sharpest vision
What is the retina?
The layer of photoreceptors cells and glial cells within the eye that captures incoming photons and transmits them
What are the optics of vision?
Relies on refraction