Sensory Systems Flashcards
How do our sensory systems work?
All of our sensory systems consist of specialised receptors, transducing sensory stimuli into action potentials in sensory axons, pathways leading into the central nervous system, and areas within the brain that analyse the input and produce perceptions from the raw sensory data.
What are the somatic senses?
All over the bodies (buried within the skin) are millions of receptors belonging to the somatic senses. These include touch, pressure, heat and cold, and pain. The afferent sensory pathways eventually reach the somatosensory cortex in the post central gyrus.
Pain sensation and perception are highly complex. Why?
They involve at least two sets of sensory pathways from the receptor to the spinal cord, and a sophisticated gating mechanism in the cord itself. The gate mechanism allows our sensitivity to pain to be influenced by central processes such as motivation and arousal.
What are the main areas for the analysis of pain?
The main areas for the analysis of pain are in the diencephalon and midbrain. An important neurotransmitter in these areas is enkephalin, a naturally occurring opiate-like chemical. The presence of enkephalin has been used to explain the effects of techniques such as acupuncture and hypnotism.
What kind of senses are taste and smell?
Taste and smell are chemical senses, with receptors combining with molecules dissolved in saliva and the nasal lining respectively. There are thought to be four primary tastes and seven qualities of smell, with the range of tastes and smells we can perceive built up from combinations of these primary qualities.
What is olfaction?
Olfaction , or smell, is the only of our sensory systems that does not involve a pathway synapsing in the thalamus. In general, areas dealing with taste and smell have widespread connections throughout the forebrain, allowing them to interact with processes such as memory, motivation, arousal, feeding, and sexual behaviour.
How do we hear?
Our hearing, or auditory receptors , are mechanoreceptors responding to the amplitude and frequency of sound pressure waves. The waves pass through the auditory canal to the eardrum or tympanic membrane, are transmitted across the middle ear via three small bones, and reach the cochlea in the inner ear.
What is in the basilar membrane?
Within the cochlea is the basilar membrane, on which are found the auditory hair cell receptors. Sound vibrations make the basilar membrane oscillate , and these oscillations produce action potentials in the hair cells. Single fibers of the auditory nerve seem to be frequency-specific, conducting only sounds of a particular pitch.
How does the sound get to the primary auditory cortex?
Pathways from the ear run via hindbrain, midbrain and thalamus to the primary auditory cortex in the temporal lobe. Each ear projects to both hemispheres. Auditory perception is built up as a sensory input and passes from primary cortex to secondary and tertiary areas.
What is proprioception and what is the vestibular apparatus?
Proprioception is our awareness of body movement and position in space. Besides touch and stretch receptors in limb joint and muscles, an important component of this system is the vestibular apparatus in the inner ear, close to the cochlea. The vestibular apparatus is made up of fluid-filled semicircular canals. Movements of the fluid is picked up by hair cell receptors in the canals, and allows the system to detect movement and position of the head in space.
