Ch.7 Pt. 1 Flashcards
What are the 2 Principles of Sensory Organization
- Sensation: detecting a stimulus (receptors)
- Perception: understanding the stimulus (CNS - primarily cortex)
Primary:
Input from thalamic relay nuclei
e.g: In the visual system, the striate cortex receives input from the lateral geniculate nucleus
Secondary:
Input mainly from a primary and secondary cortexes within the sensory system
Association:
Input from more than on sensory system, usually from the secondary sensory cortex.
Principles of Sensory Organization: Hierarchal Organization:
Specificity and complexity increases with each level
- Essentially the higher the level of damage, the more specific the deficit
What is 1/5 level of the Hierarchal Organization?
- Receptors
- Damage at this level usually associated with absence of function within that sensory modality
- eg. no rod or cones - blind
What is the 2/5 level of Hierarchal Organization?
- Thalamic Relay Nuclei
What is the 3/5 level of Hierarchal Organization?
- Primary Sensory Cortex
What is the 4/5 level of Hierarchal Organization?
- Secondary Sensory Cortex
What is the 5/5 level of Hierarchal Organization?
- Association Cortex
- Damage at these levels (cortex) usually associated with abnormalities in the perception of that sensory modality ex fusiform face area - problems identifying faces
What is Parallel Processing ?
Simultaneous analysis of signals along different pathways
- The former Model was SERIAL and it believed there was only one pathway from each level
- The newer model is Parallel which has multiple pathways from each level
What is the function of the auditory system?
To perceive sound frown the vibration of air
The way humans see light within a specific range of wavelength is similar to…
How humans perceive vibration of a specific frequency
What are pure tones, and what are they used for?
- Pure Tones are tones with only a single frequency
- And they are used to study the auditory system
How are ‘natural’ sounds different from pure tones?
- Natural sounds are more complex and they are made up of more than one frequency
What are the Auditory Systems Property of sound (physical dimensions)? (3)
- Amplitude (high- low)
- Frequency (low-high)
- Complexity (pure-rich)
What perceptual dimension is associated with Amplitude?
Loudness
What Perceptual dimension is associated with Frequency?
Pitch
What perceptual dimension is associated with Complexity?
Timbre
What are the 3 major divisions of the ear?
- External Ear
- Middle Ear
- Inner Ear
What can you find around the external ear?
Pinna and the ear canal
What can you find within the middle ear
- Tympanic Membrane (ear drum), Ossicles and Oval Window
What can you find within the Inner Ear?
Coachlea
What is the function of the outer ear?
To collect and focus sound onto the ear drum
What is the function of the middle ear?
To concentrate sound and energy
- Sound Waves place pressure on the ear drum causing it to move -‘pushing’ and ‘pulling’ it
- The motion of the ear drum causes the ossicles too move
- The stapes connect to a part of the inner ear (the oval window)
What is the function of the Inner Ear (Cochlea)?
Convert sound energy (vibrations of air) into waves of fluid
- It is compromised of 3 fluid filled canals that are separated by different membranes (2 of importance)
- The Basilar Membrane
- The tectorial membrane
Frequencies in the Cochlea
- High Frequencies displace basilar membrance in base of cochlea
- Low frequencies displace basilar membrane in apex of cochlea
Where is the basilar membrane the thickest?
The basilar membrane is thickest and broadest at the apex of the cochlea
What is the Function of the Organ of Corti? (located at the Inner Ear)
To deliver mechanical energy to the receptor cells of the ear (the hair cells)
What is the Organ of Corti comprised of?
- The Tectorial Membrane, the Basilar Membrane and the hair cells
When does the fluid within the Cochlea move?
- When the Stapes pull on the oval window
- When the fluid in the canals move this causes the membranes to move as well
- This results in a shearing motion between the 2 membranes with the hair cells in the middle
What is the function of the Hair Cells (In inner ear)?
They are the sensory receptors of the auditory system
What is the structure of the Hair Cells?
Cell Body attached deep into the basilar membrane. At the top there are bunches of cilia (hairs) that are collectively called stereocillia
What are the 2 types of hair cells?
- Inner hair cells - single row (3500 cells)
2. Outer hair cells - three rows (12 000 cells
What takes place at the hair cells?
Mechanoelctrical Transduction takes place
- Ion channels on each of the bunches of hair cells (sterocillia) are linked together by ‘tip links’
- When the sterocillia are not moving the ion channels are closed which means hair cell is at resting potential
TAKE NOTES OF THE INNER EAR HAIR CELLS!!!!
It could be a fill in the blank question
Distinguishing features of hair cells
- Opening of ion channels are opened through mechanical force
- Hair cells are also tonotopically organized (specific hair cells respond to specific frequencies
- Hair cells can not be replaced, you have what you are born with.
- They use ion channels ( quicker than metabotropic receptors)
- Hair cells can be damaged by scar tissue or certain antibiotics
- Tip links are critical for hearing (mechanotranotraasductio) - absent in mice
- Hair cells can be damaged by scar tissue or certain antibiotics
How does Auditory information reach the primary visual cortex?
via multiple pathways (At least 4)
- Not like vision which just takes one pathway
The stream of info from the ear to the primary auditory cortex is …
From ear -> 8th cranial nerve -> brain stem ->thalamus -> primary auditory cortex
More indepth info about he move of info from ear to primary auditory cortex:
- Cochlear Nucleus: In the brainstem where the 8th cranial never makes 1st synapse in the brain tonotopically organized
- Superior olivary nucleus: in the brainstem first place where signals from both ears converge. Important for localization of sound
- Inferior Colliculus: in the midbrain
- Medial Geniculate Nucleus: Thalamus
- Primary Auditory Cortex.
What is the Superior Colliculus responsible for?
Responsible for moving our head and eyes towards sounds
- It collects info from the visual system, the somatosensory system and the auditory system
Where is the Primary Auditory Cortex Found?
Found on Heschl’s Gyrus on the Temporal Lobe
The Primary Auditory Cortex is organized into what?
functional columns
- Neurons in these columns respond to similar types of sounds
What is the Anterior pathway known as?
The what pathwayMGN
- Includes the primary visual cortex, areas of temporal cortex to the prefrontal cortex
What is the Posterior pathway known as?
The Where pathway MGN
- Inclued the primary visual cortex, posterior parietal cortex and PFC
What are 3 problems with the Auditory System?
- Conductive Deafness
- Sensorineural Deafness
- Auditory Cortex Damage
What is Conductive Deafness?
Damage or stiffening of the ossicles
What is Sensorineural Deafness?
Loss of hair cells
What is Auditory Cortex Damage?
Problems with the perception of spun. Deficit will be specific to the are of the cortex damaged
