Exam 2 Flashcards
1
Q
What are lesion studies?
A
Examining how damage disrupts function –> localization of function
Micro: small, isolated lesions produced experimentally in animals
Macro: studying behavior in humans after damage due to accident, stroke, tumor, etc.
2
Q
Limitations of lesion studies
A
Essentially case studies; don’t study the effects on distal regions
3
Q
Magnetic Resonance Imaging (MRI)
A
Form of neuroimaging
Uses the magnetic properties of protons in the brain to look at structure and function in a non-invasive way
4
Q
How does proton movement work in an MRI?
A
Protons align in the presence of a strong magnetic field –> an MRI applies magnetic pulses to generate local magnetic fields within the tissue
Protons in different tissues take different amounts of time to relax back out of alignment after a magnetic pulse –> this shows up in different grayscale shades on an MRI
5
Q
What can an MRI reveal?
A
Structural imaging of different shapes in the brain, white vs. gray matter, volume and thickness of tissue, and integrity of fiber tracts
Structure can relate to behavior
6
Q
How can we study how structure seen in MRI relates to behavior?
A
Voxel-based morphometry or voxel-based lesion-symptom mapping
7
Q
How can we analyze white matter pathways (connections and projections within the CNS)?
A
Diffusion tensor imaging (DTI) or diffusion spectrum imaging (DSI)
Both methods measure the diffusion of water molecules in myelinated axons and give a fractional anisotropy (FA) score
8
Q
What does the fractional anisotropy (FA) score mean?
A
Used to determine differences in myelination and associated behaviors
High scores mean water molecules are restricted, indicating a high level of myelination
9
Q
How can we directly measure brain activity?
A
Inserting electrodes into neurons and using electrode arrays to measure voltage changes
Using an EEG via the scalp to measure voltage changes
10
Q
How can we indirectly measure brain activity?
A
Examining oxygenated blood-flow-related signals (PET of fMRI) (neuroimaging)
Examining magnetic fields produced by neural activity (MEG) (recording)
11
Q
Magnetoencephalography (MEG)
A
Recording method of indirectly measuring brain activity on a macro level; measures currents via measuring tiny magnetic fields; better spatial resolution than EEG
12
Q
Electroencephalography (EEG)
A
Recording method of directly measuring brain activity on a macro level; measures electrical activity of neurons through currents that can be picked up at the scalp with electrode sensors; interpreted through ERP graphs
13
Q
Advantages of MEG and EEG (ERP)
A
Excellent temporal resolution in milliseconds
Most direct method of measuring online brain processing
Applicable to a wide range of participants
14
Q
Disadvantages of MEG and EEG (ERP)
A
Only measures at a cortical level
Poor relative spatial resolution (MEG»_space; EEG)
Difficult to localize the source of changes
Takes many trials to see patterns
15
Q
All methods of studying the brain! (8)
A
- lesion studies
- drug studies
- behavioral studies
- recording studies (single-unit, EEG, MEG)
- neuromodulation (opto-, chemo-, TMS, tDCS)
- neuroimaging (MRI, DTI, PET, fMRI)
- genetic studies
- clinical studies
16
Q
Types of resolution
A
Spatial (space) and temporal (time)
17
Q
Levels of spatial resolution
A
- subcellular
- cellular
- circuits
- groups of neurons
- systems
- behavior
18
Q
Functional MRI (fMRI)
A
Neuroimaging method
Uses a strong gradient magnetic field to take advantage of different magnetic resonances of oxyhemoglobin and deoxyhemoglobin molecules
Indirectly measures neural activity during task performance by giving blood oxygenation level-dependent (BOLD) signal
Highlights functional connectivity
19
Q
Advantages of fMRI
A
High spatial resolution
Online viewing of activity
Viewing of full brain rather than just the cortex
20
Q
Disadvantages of fMRI
A
Poor temporal resolution
Indirect measure of activity
Individual differences make it difficult to see persistent patterns
Participant limitations
Expensive
21
Q
Functional connectivity
A
The correlation between resting-state activity in different regions of the brain; thought to highlight regions that are structurally and functionally connected
22
Q
Neuromodulation methods
A
Micro: electrical and chemical stimulation, genetic manipulations
Macro: magnetic stimulation (TMS), direct or alternating current (tDCS)
23
Q
Micro neuromodulation through electrical stimulation
A
Implanted electrode transmits current into neuron/brain
24
Q
Micro neuromodulation through chemical stimulation
A
Transmission of agents known to excite neurons (for example, kainic acid is a glutamate agonist)
25
Micro neuromodulation through genetic manipulation
Optogenetics: genetic manipulations make cells responsive to light
Chemogenetics or DREADDs: genetic manipulations make cells responsive to chemicals
26
Macro neuromodulation
Transcranial magnetic stimulation (TMS) and direct current stimulation (tDCS)
Cause temporary lesion or beneficial excitation depending on frequency and type
27
Advantages of macro neuromodulation
Temporary effects
Can cause both excitation or inhibition
Relatively inexpensive (tDCS)
28
Disadvantages of macro neuromodulation
Poor spatial resolution and localization
Alternative methods needed to assess underlying effect
Participant limitations
29
Behavioral studies
Micro: cells and molecules
Macro: animals/humans
Can measure performance on tasks, use standardized measures in research and diagnosis (behavioral, cognitive, or achievement), designed to measure functions to understand underlying deficits
30
Standardized tests
Measure achievement (reading, spelling, math) and behavior (depression, anxiety, attention)
Used to place individual performance in the context of the "average" population
31
Advantages of behavioral studies
Non-invasive, relatively inexpensive
32
Disadvantages of behavioral studies
Multiple potential underpinnings to complex behaviors
Need alternative method to asses underlying effect
Participant limitations
33
How can we use animal models in research?
- genetic modulation
- developmental studies
- modeling brain abnormalities
34
Advantages of animal models
Higher level of control
Higher degree of manipulation in the system
Molecules to systems in one model
35
Disadvantages of animal models
Impossible to model all human behaviors in animals
System doesn't perfectly parallel human brain
36
Sensation
The transduction of an external stimulus into an electrical signal (light, sound, touch)
37
Perception
The point at which a stimulus enters conscious awareness in the brain
38
Sensory receptors
Specialized cells that detect a particular category of stimulus
39
Sensory transduction
Process by which sensory stimuli are transduced into graded receptor potentials
40
Receptor potential
The graded electrical potential produced by a receptor cell in response to a sensory stimulus
41
What do we need to know about sensory stimuli? (four factors)
Modality: what?
Frequency: when?
Intensity: how much?
Location: where?
42
Modality (what)
Indicated by which neurons are active; different neurons have different pathways to the brain and different senses have specialized receptors
Receptive field: the area/type/range of stimulus that neurons/receptors process; various in size and complexity of stimulus and quality of receptor
43
Frequency (when)
When the stimulus occurs; the temporal distance between stimuli
44
Intensity (how much)
Graded changes in potential and action potential firing rate
45
Location (where)
From where the stimulus comes into the body
In the eye, visual info hits different parts of the retina which correspond to nerve and reception location
46
Dynamic range
Neurons have a low ratio of largest signal to smallest signal; made up for by relative timing of action potentials and pattern of firings over time (range fractionation, adaptation, lateral inhibition)
47
Range fractionation
Different receptors and pathways carry info from different ranges of stimuli
48
Adaptation
Rapidly and slowly adapting neurons; neurons don't conduct steady info, so rate of firing decreases after initial burst --> change or differential is more informative than absolute value
49
Lateral inhibition
Sharpens edges and contrast rather than absolute levels; interneurons at relays between afferent neurons send inhibitory signals to moderate signals while emphasizing intense signals
50
Sensory pathway for eyes
eyes --> thalamus --> primary visual cortex
51
Sensory pathway for ears
ears --> midbrain --> thalamus --> temporal lobe
52
Sensory pathway for skin
skin --> midbrain --> thalamus --> primary sensory cortex
53
Sensory pathway for smell
nose --> temporal lobe
54
Stimulus in the visual system
light (electromagnetic radiation)
55
Acuity
Depends on convergence of photoreceptors onto ganglion cells
Less acuity = more photoreceptors per ganglion cell
Highest acuity = one photoreceptor per ganglion cell (fovea)
55
How does light travel through the eye?
cornea --> pupil --> lens --> retina
56
Fovea
The center of the retina where most cones are concentrated; has the highest visual acuity
57
How does light travel through post-retinal neurons?
photoreceptors (rods and cones) --> horizontal cells --> bipolar cells --> ganglion cells
58
Rods
- long outer segment
- more discs and photopigments
- one type of pigment opsin
- do not contribute to color vision
- greater light sensitivity
- low-light
- periphery
59
Cones
- short outer segment
- fewer discs and photopigments
- three types of pigment opsins (blue, green, red)
- ability to perceive color
- daylight
- center/fovea
60
How do photoreceptors contribute to the flow of info?
Photoreceptors transduce light into a graded potential which alters glutamate release (hyperpolarizing)
61
How do bipolar and ganglion cells contribute to the flow of info?
On-center or off-center cells react differently based on location and type of stimulus (depolarizing)
62
How do horizontal and amacrine cells contribute to the flow of info?
Mediate horizontal interactions of cells
63
How do ganglion cells contribute to the flow of info?
Fire action potentials and send axons to the higher visual system (excitatory)
64
Explain center-surround receptive fields
Sensory systems are interested in contrast rather than absolute levels; on-center and off-center cells are either excitatory or inhibitory depending on where in their field the light is shone
65
On-center cell response
Light shone onto center: excitatory
Light shone onto surround: inhibitory
Light diffused across both: weak response
66
Off-center cell response
Light shone onto center: inhibitory
Light shone onto surround: excitatory
Light diffused across both: weak response
67
How do cones and ganglion cells respond to colored light?
Cones come in red, green, and blue
Ganglion cells come in red-green or yellow-blue
Different colors of light excite or inhibit different cones and ganglion cells to determine color perception
68
Types of ganglion cells
Magno and parvo
69
Magno cells
Large, lots of myelin, rapid conduction, provide info about motion and location
70
Parvo cells
Small, less myelin, slower conduction, provide info about form and color
71
Lateral Geniculate Nucleus (LGN)
Structure in the thalamus where visual information travels to; retinotopic organization maintained from LGN to primary visual cortex
72
Six layers of the LGN
Layer 1: contralateral eye, magno cells
Layer 2: ipsilateral eye, mango cells
Layers 3 and 5: ipsilateral eye, parvo cells
Layers 4 and 6: contralateral eye, parvo cells
73
Structure of primary visual cortex (striate cortex)
Six striated layers organized into ~2,500 modules
74
Modules
Each module receives input from both eyes, all orientation columns, and blobs for one region of the visual field
Process info from a specific area and pass it on to other modules
Can be synonymous with a hypercolumn or made up of multiple hypercolumns
75
Hypercolumns
Receive info from both eyes and all orientations; contain ocular dominance columns, orientation columns, and blobs
76
Ocular dominance columns and orientation columns
Ocular dominance columns: columns perpendicular to cortical surface of primary visual cortex (aka striate cortex) and are either left or right eye dominant
Orientation columns: respond to specific orientations of visual info; cross-reference with ocular dominance columns
77
Cells in the V1
Interested in oriented edges rather than circular receptive fields
Simple cells, complex cells, and hypercomplex cells
78
Simple cells
Center-surround inhibition with a line of certain orientation; cell only responds to stimuli that fall within the excitatory region
79
Complex cells
Line of certain orientation moving in receptive field; cell is excited by any stimulus of that orientation, but in any location
80
Hypercomplex cells
Line of certain orientation with end inhibitory regions, detect ends of lines of particular orientation; excited by stimuli whose ends don't intercept with inhibitory region
81
Two main visual processing streams out of V1
Dorsal stream (where and how) and ventral stream (what)
82
Dorsal stream
Where and how: analysis of motion, spatial relations, shape, and size
Direct movements such as eye movement, reaching, grasping, other guided movements
Associated with magno neurons
Goes to posterior parietal lobe via intraparietal sulcus
83
What might occur with damage to the dorsal stream?
Akinetopsia or visuospatial neglect
84
Akinetopsia
Extremely rare disorder where patients cannot perceive motion; occurs with bilateral damage to V5 and results in processing of snapshots without any flow
85
Visuospatial neglect
More common disorder where the brain neglects to consciously process certain areas of the visual field (most commonly left visual field with damage to right parietal damage)
Patients can sense stimuli on the neglected side, but ignore it until it's been pointed out to them
86
Ventral stream
What: form and color
Includes lateral occipital complex (LOC), fusiform face area (FFA), extrastriate body area (EBA), and parahippocampal place area (PPA)
Associated with parvo neurons
Goes to temporal lobe via V2, V4, and ITC
87
Lateral occipital complex (LOC)
Responsive to objects
88
Fusiform face area (FFA)
Responsive to faces and other areas of human expertise; in the inferior temporal cortex
89
Extrastriate body area (EBA)
Responsive to human bodies and body parts
90
Parahippocampal place area
Responsive to scenes and backgrounds
91
Cerebral achromatopsia
Damage to V4 causes non-retinal color blindness; patient only sees in black and white and cannot imagine or remember color
92
Visual agnosias
A set of disorders caused by damage to the ventral stream and characterized by failure to know/inability to perceive or identify visual stimulus
Prosopagnosia and object agnosia
93
Prosopagnosia
Damage to FFA
Congenital prosopagnosia or Williams Syndrome
Patient can identify details in an image, but is unable to piece together the details into the context of a larger, whole image (including faces)
94
Object agnosia
Patient can identify the larger object but not its details
95
Transduction in the auditory system
outer ear --> middle ear --> inner ear and Organ of Corti
96
Transmission in the auditory system
spiral ganglia --> brainstem cochlear nuclei --> medulla (superior olivary complex) --> decussation --> inferior colliculi --> MGN of the thalamus --> primary auditory cortex (A1)
97
Auditory stimulus
Compressions and rarefactions of air
Frequency, amplitude, and timbre
98
Frequency
Hz, perception of pitch
Human auditory range is 20 Hz to 20,000 Hz
99
Amplitude
dB, perception of loudness
100
Timbre
Complexity of sound
101
Outer ear
Pinna, ear canal, tympanic membrane (separation)
102
Middle ear
Ossicles and oval window
103
Inner ear
Cochlea
104
Impedance matching
The ear turns movement in air into movement in fluid; air vibrations tend to lessen in fluid
Waves are amplified to match original impact by the oval window being much smaller than the tympanic membrane
105
Conductive hearing loss
Problem in outer or inner ear such as earwax, swimmer's ear, ruptured eardrum, otitis media, or ostosclerosis
106
Sensorineural hearing loss
Problem in cochlea; presbycusis or noise-induced
107
Cochlea
Aka snail shell or bony labyrinth
Oval window vibrated by ossicles; fluid in cochlea vibrates up to apex and back down to displace round window
108
Chambers of the cochlea
Oval window inserts into the scala vestibuli, which winds up to the apex and comes back down as the scala tympani
The scala media sits between the other two chambers
109
Scala vestibuli and scala tympani
Filled with perilymph (extracellular fluid) which vibrates with vibrations of the oval window
110
Scala media
Filled with endolymph (high in potassium and low in sodium); contains the basilar membrane and the Organ of Corti
111
Organ of Corti
This is where fluid vibration turns into electrical signals sent to the brain; done via hair cells with potassium channels
112
Hair cells
Inner: carry 90% of auditory signal
Outer: modulatory/amplifying role
Hair cells release more (depolarization) or less (hyperpolarization) glutamate depending on whether they bend toward or away from the kinocilium, respectively
Tip links open and close potassium channels to alter neurotransmitter release into the auditory nerve
113
How does the auditory system code for frequency?
Tonotopic mapping:
The Organ of Corti sits atop the basilar membrane
The basilar membrane is wider/floppier at the apex of the cochlea (lower freq.), and more narrow/rigid at the base (higher freq.)
Depending on frequency of sound, different places along the basilar membrane vibrate, causing different hair cells to activate
114
Presbycusis
Progressive hearing loss of higher frequencies that increases with age; occurs with loss of outer hair cells starting at base to the apex of the basilar membrane, in addition to thickening of narrow base
115
Noise-induced sensorineural deafness
One-time, very loud noise may cause hearing loss with possible recovery
Long-term exposure to moderately loud noise may lead to progressive loss
116
Cochlear implant external mechanisms
External: the microphone picks up on sound, the speech processor divides sound into channels, and the transmitter transmits to the receiver
117
Cochlear implant internal mechanisms
Internal: receiver and stimulator convert signals into electric impulses sent via cable to electrodes, an array of ~120 electrodes is wound through the cochlea to stimulate the spiral ganglion
117
How does the auditory system code for amplitude?
The firing rate of the spiral ganglion and the auditory nerve
The spread of firing of axons; more intense sound will maximally shift larger area of the basilar membrane, indicating that the sound is louder
118
How does the auditory system code for location?
Distance: intensity attenuates with distance, high frequencies attenuate more than low
Direction: vertical (bad in humans) and horizontal (good in humans) planes
Input from both ears is integrated at the superior olive in the medulla where timing differences help map out locations in space
119
Horizontal hearing cues
Interaural intensity cues and interaural timing cues
120
Interaural intensity cues
Head forms "sound shadow" so sound is louder in the ear that it's closest to; this is mostly used for higher frequencies
121
Interaural timing cues
Relative phase will reach each ear at a different point depending on its location; this is mostly used for lower frequencies
122
How do we perceive complex sounds?
Pattern recognition, localization, planum temporale, and further processing streams
123
Pattern recognition
Extraction of particular patterns of constantly changing activity
124
Planum temporale
Area with many connections between auditory system and cortical language areas, including primary and secondary auditory cortices and Wernicke’s area
125
Auditory processing streams for language
Dorsal: sound to motor output of speech (e.g. “repeat after me”); Broca’s area
Ventral: sound to meaning; Wernicke’s area
126
How is music processing differently in the brain?
Processing in auditory association cortices is more complex and right-lateralized
127
How does the brain change with musical training?
Motor system: violinists, pianists, etc. have higher cortical representation of non-dominant hand
Auditory system: A1 is 130% larger and 102% more responsive
Connectivity: corpus callosum and arcuate fasciculus volume/response differ between different types of musical training
128
Amusia
A disorder where patients have a normal perception of speech and environmental sounds, but reduced ability to process music; music sounds like meaningless noise without tune or melody
Usually acquired and congenital and features a thicker right STG and right IFG
129
What does the vestibular system do?
Maintains balance, keeps the head in an upright position, and adjusts eye movements to accommodate for head movements
130
Structures of the vestibular system
Vestibular sacs and semicircular canals
131
Vestibular sacs
Utricle and saccule; respond to gravity and info about head orientation
Floor of utricle and wall of saccule contain patches of receptive tissue with hair cells embedded into gelatinous mass containing otoconia (small crystals of calcium carbonate)
The weight of the otoconia causes mass to shift as orientation of head changes, shearing cilia of hair cells
132
Semicircular canals
Respond to angular acceleration and changes in head rotation alone three major planes of the head
Receptors in each canal respond to angular acceleration in one plane
Cupula within ampulla exerts shear on hair cells
133
Cutaneous senses
Having to do with the skin
134
Proprioception
Having to do with body position
135
Kinesthesia
Having to do with movement
136
Two-point discrimination
Reflects the degree of somatosensory innervation of the skin at different locations
2-4 mm on the fingertip; 4-5 cm on the thigh
137
How does touch code for location?
The organization of dermatomes and which receptors are active
138
How does touch code for intensity?
Receptor activity reflects degree of skin indentation
139
Four important mechanoreceptors
Merkel disks, Meissner corpuscles, Pacinian corpuscles, and Ruffinin endings
140
Properties of Merkel disks
Code for pressure, have a smaller receptive field, shallow, slowly adapting 1 fiber, low frequency range of 0.3-3 Hz
141
Properties of Meissner corpuscles
Code for fluttering touch, have a smaller receptive field, shallow, rapidly adapting 1 fiber, frequency range of 3-40 Hz
142
Properties of Ruffini endings
Code for stretching, larger receptive field, deeper, slowly adapting 2 fiber, frequency range of 14-400 Hz
143
Properties of Pacinian corpuscles
Code for vibration, larger receptive field, deeper, rapidly adapting 2 fiber, frequency range of 10-500 Hz
144
Temperature receptors
Different receptors exist for different temperature ranges; 6 main thermal receptors from the TRP family
Cold temp. receptors are more superficial while warm temp. receptors are deeper
145
Proprioceptors
Receptors that receive info from muscles and joints; muscle spindles and golgi tendon organs
146
Muscle spindles
Lay parallel to muscles and are very sensitive to the length and stretch of muscles; provide sensory input for stretch reflect where brain is not required
LA afferent circuits
147
LA afferent circuit
Muscle spindle sends info to spinal cord via LA afferent neurons --> synapse directly onto alpha moto neurons --> inhibitory neurons innervate reciprocal muscles --> agonist is active, and the antagonist relaxes
148
Golgi tendon organs
Junctions between tendons and muscles; good at sensing load and weight and protects muscles from excessively heavy loads by causing muscle to relax and drop
149
How does touch info get to the brain?
Sensory signals join spinal cord at different points depending on location and dermatomes --> info goes into dorsal root ganglion and out from ventral root --> medial lemniscal pathway
150
Medial lemniscal pathway
Dorsal pathway where touch info travels through dorsal column, decussates in the medulla, and travels to the thalamus and the somatosensory cortex
151
Where does touch info go in the thalamus?
Thalamic projections to different subzones:
Spindles project to 3b
SA and RA mechanoreceptors project to 3b
RA mechanoreceptors project to 1
Deep tissue (pressure and limb position) project to 2
152
In what order does info pass through the somatosensory cortex?
Area 3 --> areas 1, 2, and 5
Receptive fields become larger and more complex and contain input from multiple receptor types and sources
153
Pain
Not excessive sensory stimulation, but actually a completely different input carried to the brain through different pathways
154
Pain receptors
Nociceptors
155
Components of pain
Sensory: pure perception
Emotional: immediate and chronic
156
What pathway does pain follow?
Tissue damage --> peripheral nerves --> spinal cord --> thalamus --> somatosensory cortex, frontal cortex, limbic system
157
Anterolateral or spinothalamic system
Pain fibers carry info into dorsal horn and decussate immediately, allowing for immediate reflex processing in the spinal cord
Signal travels up to the brain in anterolateral/spinothalamic tract and distributes to various regions
158
Brain regions involved in pain processing
Limbic system (emotional component), anterior cingulate cortex, midbrain periaqueductal gray (PAG), red nucleus, medullary raphe nuclei, reticular formation
159
Brain mechanisms for emotional component
Immediate: ACC and insula
Chronic: prefrontal cortex
160
Insula
Codes for emotional response to pain and processing of harm associated with certain actions; linked to motor system
161
What would damage to the insula cause?
Decrease in emotional response; patients would feel the pain but not perceive it as harmful or something to be avoided
162
Anterior cingulate cortex (ACC)
Codes for emotional unpleasantness of pain; activated when receiving pain or seeing other receiving pain, indicating connection to pain perception
Activity can decrease through hypnosis meant to reduce perception of unpleasantness of pain
Linked to limbic system
163
What is the effect of endogenous opioids?
Pain perception is modified by hormones or NTs released based on environment or context
Descending pathway from brain to spinal cord acts to "intercept" and inhibit pain signals at every level of cord, stopping conscious perception in the brain
164
Gate Theory
States that the transmission of pain signals can be modulated by descending pathways and interactions between touch and pain fibers in cord; signals are gated from getting to the brain
165
Methods of pain treatment
- stimulation of PAG (analgesia)
- opiates
- anti-inflammatories
- placebo effect
166
How does phantom limb pain appear?
Input from residual limb such as muscle contractions, ectopic activity from neuroma, dorsal root ganglia, and spinal cord; reorganization or preserved function in central nervous system
Contextual factors such as sensory stimulus, motor signals, and psychological factors
167
Taste
Gustation (bitter, sour, sweet, salty, umami)
168
How does the tongue process taste?
Tongue, palate, pharynx, and larynx contain about 10k taste buds mostly around foliate papillae on back of tongue
169
How do taste buds work?
Each contain about 20-50 receptor cells with protruding cilia
Transduction: chemical binds to receptor, alters membrane permeability, receptor potential, and NT release (mostly via G-protein)
170
How does taste info reach the brain?
Ipsilateral
Tongue --> chorda tympani --> nucleus of solitary tract (NST) in medulla --> thalamus --> gustatory cortex in insula
171
Where in the brain is taste info processed?
Primary gustatory cortex (insula) and secondary gustatory cortex (orbitofrontal cortex)
Hypothalamus and amygdala/limbic system
172
Smell stimulus
Oderants and volatile substances
173
Smell receptor cells
Six million olfactory receptors (bipolar neurons) in the olfactory epithelium at the top of the nasal cavity
174
How do olfactory receptors work?
Receptor cilia are sent to the surface of the mucosa where they are split into 10-20 cilia that penetrate mucus layer
Mucus dissolves oderants and stimulate receptors, then bundles of axons enter skull via holes in the cribriform plate and project towards the olfactory bulb
175
Olfactory bulb
Each receptor sends a single axon to the bulb where the axons synapse onto mitral cells in olfactory glomeruli
176
Mitral cells
Axons travel to rest of brain via olfactory nerve
177
Olfactory glomeruli
Bundle of dendrites of mitral cells and terminal buttons of axons
178
Where in the brain is smell processed?
Primary olfactory cortex in the limbic region, contain piriform and entorhinal cortices with olfactopic map
Piriform cortex sends signals to hypothalamus or dorsomedial thalamus and orbitofrontal cortex
