W4 notes pt 2 Flashcards
organ of Corti
Resting on top of the basilar membrane is the organ of Corti, which contains many rows of hair cells that transduce sound energy into neural signals
auditory nerve
Bending hair cells stimulates the release of neurotransmitters onto the cells of the auditory nerve
from the medulla, sound info is sent to….
From the medulla, sound information is sent to the midbrain, which manages reflexive responses to sound, such as turning toward the source of a loud noise
midbrain function
In addition, the midbrain participates in sound localization, or the identification of a source of sound
The midbrain passes information to the thalamus, which in turn sends sound information to the primary auditory cortex, located in the temporal lobe
pinna
The pinna helps us localize sounds in the vertical plane, or in space above or below the head
Somatosensation
Somatosensation provides us with info about the position and movement of our bodies, along with touch, skin temp and pain
vestibular system
Adjacent to the structures responsible for encoding sound, we find the structures of the vestibular system, which provide us with info about body position and movement
pathway to guide voluntary movement
Vestibular info travels from the medulla to the thalamus, the primary somatosensory cortex of the parietal lobe, and then the primary motor cortex in the frontal lobe
Allows vestibular info to guide voluntary movement
pathway of touch
Info about touch travels from the skin to the spinal cord
Once inside, touch pathways proceed to the thalamus, along with input from the cranial nerves originating in the touch receptors in the skin of the face, mouth, and tongue
The thalamus transmits touch info to the primary somatosensory cortex, located in the parietal lobe
The representation of touch in the primary sensory cortex is plastic, which means…
that it changes in response to increases or decreases in input from a body part
fast myelinated axons
Fast, myelinated axons are responsible for that sharp “ouch” sensation that often accompanies an injury
slower unmyelinated axons
Slower, unmyelinated axons are responsible for dull, aching sensation
pathway for pain
Pain fibres from the body form synapses with cells in the spinal cord, which in turn sends pain messages to the thalamus
This info takes a relatively direct route, with only one synapse in the spinal cord separating the periphery of the body and the thalamus in the forebrain
This arrangement ensures that pain messages are received by the brain fast
From the thalamus, pain info is sent to the anterior cingulate cortex and the insula, which manage the emotional qualities of pain, and to the somatosensory cortex in the parietal lobe, which manages info about the location and intensity of pain
gate control theory of pain
Suggests that input from touch fibres competes with input from pain receptors, possibly preventing pain messages from reaching the brain
if the gate is open…
If the gate is open, pain signals travel to the brain and are perceived
if the gate is closed
If the gate is closed, it’s possible that the pain may not be perceived at all
factors that may close the gate
Factors that may close the gate to pain include psychological factors (e.g., a child too excited by a birthday party to let a skinned knee bother them or a soldier in such a state of arousal that they fail to notice their injuries until the battle is over)
perception of pain
The perception of pain is affected by the descending influence of higher brain centres
periaqueductal grey
The periaqueductal grey is a major target for opioid painkillers, such as morphine
Electrical stimulation of the periaqueductal gray produces a significant reduction in the experience of pain
olfaction
sense of smell
Our chemical senses begin with molecules suspended in the air in the case of olfaction
Olfaction provides more information from a distance, like vision and audition,
gustation
sense of taste
-chemical senses dissolved in saliva
gustation, like the somatosenses, involves information from contact with the body
olfaction
Air containing olfactory stimuli is taken in through the nostrils and circulated within the nasal cavities connected to the nostrils, where it interacts with olfactory receptors
olfactory epithelium
The receptors are located in a thin layer of cells within the nasal cavity known as the olfactory epithelium
Unlike most neurons, the olfactory receptors regularly die and are replaced by new receptor cells in cycles lasting 4 to 6 weeks
olfactory nerve
The other branch carries info back to the CNS as part of the olfactory nerve
olfactory bulbs
The olfactory nerves fibres synapse in one of the 2 olfactory bulbs, located just below the mass of the frontal lobes
olfactory pathway
Unlike most other sensory input to the brain, olfactory pathways do not make direct connections with the thalamus before the information reaches the cerebral cortex
Instead, fibres from the olfactory bulbs proceed to the olfactory cortex, located in the lower portions of the frontal lobe extending into the temporal lobe, and to the amygdala
Because of the role these areas of the brain play in emotion, these pathways may account for the significant emotional rxns we experience in response to odour
papillae
Papillae are small bumps on the tongue that contain taste buds
taste buds
Taste buds are a structure found in papillae that contain taste receptor cells
taste pathway
Info about taste travels from the mouth and tongue to the medulla
The medulla in turn communicates with the thalamus, which sends taste info to the insula, lower somatosensory cortex of the parietal lobe, and to the orbitofrontal cortex, where the emotional pleasantness or unpleasantness of particular stimuli is processed
Olfaction and gustation share three interesting perceptual themes:
(a) We can easily identify a number of complex stimuli combining many types of molecules, such as the aroma of coffee
(b) we can detect small differences among similar smells and tastes
(c) our experience often shapes our perception of an olfactory or gustatory stimulus
