Midterm Flashcards
(116 cards)
1
Q
2 major cell types of the nervous system
A
Neurons and glia
- Glia are more numerous (1 trillion glia vs. 100 billion neurons)
2
Q
Central Nervous System (CNS)
A
- Functions: Analyze and integrate information
- Has a blood-brain barrier
- Cannot regenerate (usually)
- Myelination: oligodendrocytes
- Terminology: nuclei, tracts
3
Q
Peripheral Nervous System (PNS)
A
- Functions: receive sensory info, muscle movement
- No blood-brain barrier
- Regenerates
- Myelination: Schwann cells
- Terminology: ganglia, nerves
4
Q
Gyrus, sulci, & fissures
A
- Gyrus: surface of brain
- Sulci: grooves
- Fissures: deep grooves
5
Q
Gray matter
A
- Cortex, Nuclei or Ganglia (groups of nerve cell bodies and neuropil) generally of similar function
- Neuropil - neuronal processes, synapses and glia
6
Q
White matter (& bundles vs. tracts)
A
- Bundles: (groups of myelinated axons [see below]) that course in the same direction
-
Tracts: also groups of axons - myelinated and un-myelinated but indicates origin, destination and therefore function
- e.g., corticospinal tract
7
Q
Cerebrospinal fluid, dura matter, and arachnoid matter
A
- Made in the ventricles
- Circulates between all the cells and their processes and in the space between a membrane on the brain surface (pia matter) and a membrane next to the skull or spine (arachnoid matter)
- called the subarachnoid space
8
Q
Blood vessels and coverings of the brain
A
Blood vessels:
- Arteries, capillaries, veins and venous sinuses
Coverings (meninges):
- Dura mater (tough mother)
- Arachnoid mater (spider web like)
- Pia mater (tender/affectionate)
9
Q
Types of neurons
A
- Stellate (star-like)
- Pyramidal (conical/triangular)
- Correspond to function
- Multiple dendrites, only one axon
- Neurons named after famous guys (Purkinje, Betz, Cajal, Retzius, Mauthner)
- Purkinje cell:
- One complex dendrite that resembles a sea fan
- Many synapses
10
Q
Golgi stain vs. Nissl stain
A
- Golgi stain: fills processes of some cells with black precipitates of heavy metals
- Nissl stain: stains all nuclei and neuronal cytoplasm blue
11
Q
Synapse types
A
Asymmetrical = type 1
- Postsynaptic membrane is thicker than presynaptic membrane; spherical clear vesicles
- These are excitatory synapses - on
Symmetrical = type 2
- Postsynaptic membrane same as presynaptic membrane; flattened clear vesicles
- These are inhibitory synapses - off
12
Q
3 types of glia
A
- Astrocytes: Maintains appropriate chemical environment for neuronal signaling (only in CNS)
- Oligodendrocytes: Lay down myelin around some (not all) axons (only in CNS)
- Microglial cell: Scavenger cells that remove cellular debris from sites of injury or normal cell turnover
13
Q
3 principle germ bands
A
- Ectoderm: forms skin, neurons
-
Mesoderm: forms notocord, muscle, kidney, bone, blood
- Underlies (neuro) ectodrm, and induces the neural plate
- Endoderm: forms lining of gut, lungs, placenta in mammals
14
Q
Neural crest cells, notocord, and neural floor plate
A
- Neural crest cells: make PNS, endocrine, pigment cells, connective tissues, and is source of ganglia
- Migrate into somites to form the PNS
- Derived from leading edge of neural folds
- Notocord: induces floor plate (helps polarize dorsal to ventral)
- Neural floor plate: rich source of neuronal porphogens & axonal cues
15
Q
Apoptosis
A
Programmed Cell Death
Instrinsic and extrinsic factors
Features: membrane blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation
Requires ATP
Systematic and clean
- Can be beneficial
16
Q
Necrosis
A
- Premature death of living cells
- Extrinsic factors only
Features: cell swelling, disruption of membranes, cell lysis, release of intracellular content (causing inflammation)
Detrimental
Often leads to buildup of dead tissue
17
Q
Nerve growth factor (NGF)
A
- One example of a neurotrophin (NT)
- Supplied by target, promotes cell growth (instead of apoptosis)
- Signals through tyrosine kinase (Trk) receptors
- Viktor Hamburger, Rita Levi-Montalcini, Stanley Cohen
18
Q
Bcl-2 gene
A
- This gene encodes an integral outer mitochondrial membrane protein that blocks the apoptotic death of some cells such as lymphocytes
- Overexpression of this causes B-Cell Leukemia
- Example of how cell death can be blocked by overexpression of a gene (as in Leukemia)
19
Q
Ced-4
A
Pro-apoptotic protein expressed primarily during embryogenesis of C. elegans, homologous to the human Apoptosis activity factor (Apaf)
20
Q
Apaf
A
- This scaffold protein binds to Cytochrome c and dATP to form a 7-spoke apoptosome complex
21
Q
Cytochrome C
A
- This freely-diffusible molecule is well known for it’s role in cellular respiration but it also functions to activate a caspase cascade, which commits the cell to the death process
22
Q
Caspase
A
- This family of proteins exists as inactive proenzymes that only become active after undergoing proteolytic processing and plays a central role in the execution-phase of cell apoptosis
23
Q
Mitochondria
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In response to a variety of apoptotic stimuli (i.e. DNA damage, ischemia, oxidative stress, etc.) it releases apoptogenic proteins to the cytoplasm that initiates the execution of apoptosis
24
Q
TrKA
A
High affinity receptor for nerve growth factor (NGF)
25
NGF
* This molecule that promotes the survival and differentiation of neurons was discovered by Rita Levi-Montalcini and Stanley Cohen in the 1950s while faculty members at Washington University in St Louis
26
Selective aggregation
* If you put dissociated embryonic tissures (vertebrate and invertebrate) in a dish, you will get formation of different animal embryos
* This suggests ancient (surface) adhesion molecules
* Cell adhesion gene = N-cadherin
27
Lamellipodium
The primary morphological characteristic is a sheetlike expansion of the growing axon at its tip
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filopodia
* The fine processes that extend from the lamellapodium
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Microtubule cytoskeleton
* Responsible for the elongation of the axon itself
30
Integrins
* A broad class of cell surface receptors that bind specifically to the extraceullular matrix cell adhesion molecules
* They do not have any kinase or direct signaling capacity
31
Netrins
* Secreted molecules that can attract or repel axons by binding to their receptors DCC (attract) and UNC5 (repulse)
* Opposing activities of netrin and slit occur at the ventral midline of the spinal cord. This guidance system ensure the axons relaying pain and termperature cross the midline at appropriate levels of the spinal cord and remain on the correct side until they reach their thalamic targets
32
Slits
* Secreted proteins that normally repel growth cones by engaging Robo class receptors
* Secreted factor important for preventing an axon from straying back over the midline once it has crossed initially
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Ephrins
* Cell surface molecules used to recognize appropriate pathways for growth and appropriate sites for synaptogenesis
* Found on growing axons and growth cones. Function via homophilic binding. Have been associated with fasciculation of axons
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Semaphorins
* Chemorepellent bound to cell surfaces or extracellular matrix that prevent extension of nearby axons
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Cell adhesion molecules
* Integral membrane proteins that utilize homophilic binding that have been associated with the bundling of groups of axons
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Calcium-dependent cell adhesion molecules
A family of diffusible molecules that act as attractive or repulsive cues to guide growing axons. First vertebrate gene identified was called Unc
37
Pioneer Neurons and Guidepost Cells
The first nerve cells to appear in limb buds of embryonic grasshoppers are a pair that lie at the distal tip and project axons along the length of the limb to the central nervous system
* The stereotyped route navigated by these pioneer axons is followed by other neurons and eventually becomes that of a major adult nerve trunk
* The guidance cues that delineate the route come from a set of nonadjacent guidpost cells along with the pioneers grow
38
Horizontal Gaze Palsy with Progressive Scoliosis
* Caused by mutation in ROBO3 gene.
* Robo3 ensures that motor and sensory nerve pathways cross over the midline by inhibiting Robo1/2-mediated repulsion.
* Drosophila robo disrupts longitudinal tract formation
* Mutation prevents axons in the corticospinal tract and trochlear nerve from growing past the midline, so the hindbrain and spinal cord undergo abnormal growth
39
Neurotrophins and their Receptors
* Signaling via Trk receptors can lead to a variety of cellular responses depending on the signaling cascade involved. The possibilities include cell survival, neurite growth, and activity dependent plasticity
* Signaling through p75 receptors can lead to neurite growth, cell cycle arrest, and cell death.
* Neurotrophins have distinct effects on different target neurons
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Topographic mapping
Posterior retinal axons project to the anterior tectum, and anterior retinal axons project to the posterior tectum
41
Sperry experiment
* When the optic nerve of a frog is surgically interrupted, the axons regenerate with appropriate specificity. Even when rotated the axons regenerate to the original position in the tectum
42
Rhombencephalon develops into:
* Medulla
* Pons
* Cerebellim
* Metencephalon
* Myencephalon
* I.e., rhombencephalon develops into brainstem
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Prosencephalon develops into:
* Cerebrum
* Diencephalon
* Telencephalon
* Diencephalon and telencephalon develop into cerebrum
* Hypothalamus
* Hippocampus
* Thalamus
* Optic cups
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Mesencephalon developes into:
* Midbrain
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Neural tube deveopes into:
* Spinal cord
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Hox genes
* Encode transcription factors
* Are present in humans
* Are also present in flies
47
Sonic hedgehog
* It plays a key role in regulating vertebrate organogenesis, such as in the growth of digits on limbs and organization of the brain
* It's a diffusable element
* Known as a morphogen (diffuses to form a concentration gradient and has different effects on the cells of the developing embryo depending on its concentration)
* Induces formation of distinct classes of ventral neurons at different rostrocaudal levels
48
Metaencephalon develops into:
* Pons
* Cerebellum
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Myeloencephalon develops into:
* Medulla
50
Thoracic vs Sacral Spinal Cord
* Size of white matter tracts increases as more axons are added on the way TO the brain and decreases as axons end on the way FROM the brain.
51
Intervertebral Foramen
* Between every pair of vertebra there are two apertures that allow for the passage of the spinal nerve root, dorsal root ganglion, the spinal artery of the segmental artery, communicating veins, and transforaminal ligaments.
52
Joseph Erlanger, Herbert Spencer Gasser, and Geurge H. Bishop
* Recording properties of nerve fibers using oscilloscope
53
Dorsal Root Ganglion Cells
* Contain **pseudo-unipolar cells**: one axon with two branches, central and peripheral.
* The axons in DRG are known as afferents, sending information into the central nervous system.
* The distal section of the axon may either be a bare nerve ending or encapsulated by a structure that helps it to relay specific information to the brain. A Meissner’s corpuscle or a Pacinian corpusle can be the encapsulating structure that helps the distal process become sensitive to mechanical stimulation.
* Single sensory endings (light & crude touch, pain, temperature and muscle senses
54
Alpha axons
* Very fast conduction velocity (80-120 m/s)
* Useful for discriminative touch
* e.g., being able to tell coins apart with eyes closed
* Has largest axon diameter (13-20 um)
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Gamma axon
* Somewhat slow conduction velocity (5-30 m/s)
* Useful for fast pain and temperature (cold)
* e.g., getting stabbed
* Has intermediate axon diameter (1-5 um)
56
C axon
* Slowest conduction velocity (0.5-2 m/s)
* Useful for slow pain and temperature (warm)
* Has smallest axon diameter (0.2-1.5 um)
57
Dermatome
* Area of skin that is mainly supplied by a single spinal nerve.
* There are 8 cervical nerves (C1 has no dermatome) 12 thoracic nerves, 5 lumbar nerves, and 5 sacral nerves each relaying sensation from a particular region to the brain
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Motor unit
* A motor neuron and the collection of skeletal muscle fibers it innervates
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Motor neuron pool
* The collection of motor neurons that innervates a single muscle
* Organized somatotopically - according to the body plan
60
Segmental nerve
A nerve that consists of the afferent and efferent axons from the dorsal and ventral roots of a spinal cord segment
61
Compound action potential
* The response of a _peripheral nerve_ to an electrical stimulus; it represents the sum of the action potentials of all active fibers in the nerve
62
Spinal motor neurons
* Multipolar
* Output diverges to several or many muscle cells (motor unit)
* Input converges from:
* signal or posterior (dorsal) root ganglion cells
* Spinal interneurons
* long tracts from the brain
* Integrate/decide whether to fire or not
* Map (flexors, extensors, proximal, distal)
63
Knee jerk reflex
* When the knee is struck, 1a muscle afferents fire
* There is a monosynaptic activation of the extensor alpha-motor nueron
* The agonist muscle contracts
* The knee extends
* Glycinergic (inhibitory) interneurons are activated to inhibit motor neurons to the flexor (antagonist) muscle
64
Stepping on a nail
* Stepping on a nail activates pain afferents in the skin
* This activates interneurons in the dorsal horn that excite flexors and inhibit extensors and the leg flexes or withdraws
* The crossed extensors are activated and the crossed flexors are inhibited to extend the other leg to stand on
65
Dorsal Column/Medial Lemniscus Pathway
* Sensory pathway responsible for transmitting fine touch, vibration, and conscious proprioceptive information from body to cerebral cortex as well as tactile pressure and two-point discrimination
* Name comes from two structures that the sensation travels up: Dorsal or posterior column of spinal cord and Medial lemniscus in the brainstem.
* Fine sensation is detected in the dermis by Meissner’s corpuscles, and an action potential is started. Action potential travels up an axon (where is the cell body of this neuron?) into the dorsal column of the spinal cord. Axons continue running up the dorsal column. At the level of the medulla oblongata, the axons synapse with neurons in gracile and cuneate nuclei
* The secondary neurons cross over to the other side of the medulla to form the medial lemniscus. The axons travel up the rest of the brain stem to their particular region (thalamus, ventral posterolateral nucleus, ventral posteromedial nucleus)
66
Corticospinal (Pyramidal) Pathway
* Axons from neurons in the cerbral cortex of the precentral, prefrontal, and postcentral gyri converge and move into the middle third of the cerebral peduncle, where they enter the pons as clustered fascicles.
* As the tract descends, the majority of the fibers controlling fine movements of the face and related areas cross to reach their specific motor nuclei.
* At the pontomedullary junction, the fibers emerge from the pyramids (corticospinal tract) on the anterior aspect of the medulla oblongata. In the medulla, 65-90% of fibers cross over to form the lateral corticospinal tract. The uncrossed fibers descend as the anterior corticospinal tract.
* The majority of fibers in the lateral and anterior corticospinal tracts terminates on interneurons in the spinal cord gray matter
67
Charles Sherrington and Edgar Adrian
* Nobel Prize 1932 for demonstrating reflexes require integrated activation and demonstrated reciprocal innervation of muscle
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Dimains of senses
* Exteroception (outside of us) vs. Interoception (within us [like stomach ache])
* Distance (hearing, smell, sight) vs. direct (touch, taste)
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3 kinds of stimuli
1. Radiant - light and thermal
2. Mechanical - pressure and sound
3. Chemical - molecules and ions
70
3 classes of transducers
1. Direct: by neurons
2. Mediated: by extensions, cell filters, receptor cells, complex organs
3. Code: onset, duration, intensity, change
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Ruffini’s end organ
* Slowly adapting receptor sensitive to skin stretch.
* Responds to sustained pressure and shows little adaptation
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Meissner’s corpuscle
* Responsible for sensitivity to light touch and low vibration.
* Rapidly adaptive receptors
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Pacinian corpuscle
* Sensitivity to vibration and pressure.
* Optimal sensitivity is higher frequency than Meissner’s corpuscle
* Deep pressure and fast vibrations
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Merkel’s disc
* Sustained touch and pressure response
* Form and texture perception
* Slowly adapting, enriched in the fingertips
* Highest spatial resolution
75
Free nerve endings
* Detect temperature, touch, or pain
* Depending on the fiber themselves they can be either fast or slow adapting
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Adequate stimulus
* The form of energy to which a particular sensory cell is **most** sensitive (light, touch etc)
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Law of specific nerve energies
* Depolarization of neurons in a pathway is interpreted as a particular form of stimulation
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Threshold
* The magnitude of a stimulus sufficient to depolarize the sensory neuron
* The lower the threshold, the more sensitive
* Most sensitive around the mouth
79
There are 3 classifications for visual cortex receptive field cells
* _Simple cells_ are elongated, for instance with an excitatory central oval and an inhibitory surrounding region. Or it can be rectangular with half and half. Images need to have a particular orientation.
* _Complex cell_ receptive fields need a correctly oriented bar of light and it must move in a particular direction.
* _Hypercomplex cell_ receptive fields need all of the above as well as the bar being of a particular length
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Types of neuronal adaptation
* Receptors that return to normal quickly are called phasic or rapidly adapting
* Receptors that are slow to return to normal firing are called tonic or slowly adapting.
* Slowly adapting: Merkel and Ruffini and some free nerve endings
* Rapidly adapting: Meissner, Pacininan and free nerve endings
81
6th sense
* Position sense
* Syphilis causes an absense of the position sense
82
2 clinical findings in Tabes Dorsalis
1. Difficulty walking over uneven surfaces in the dark
2. Reduced or absent knee jerk reflexes
83
Rubrospinal Pathway
* Pathway from the red nucleus mediates voluntary control of movements, excepting the fine movements of fingers, toes and mouth
* Rubrospinal fibers (red) from large cells of caudal and medial red nucleus cross directly to the opposite side to descend.
* In the spinal cord, rubrospinal axons make excitatory synapses on interneurons between the posterior and anterior horns and on a few motor neurons in the ventral horn
84
Tectospinal Pathway
* Pathway from the superior colliculus mediates head and body orientation in response to localized visual, auditory, and tactile stimuli often from the same source
* Arise from large cells in deeper layers of superior colliculus and cross directly to the opposite side.
* Terminates in medial ventral horn of cervical spinal cord
85
Vestibulospinal Pathway
* Mediates head and body orientation in response to head linear and angular velocity and with respect to gravity
86
Reticulospinal Pathways
* Carry information from brain stem to both sides of spinal cord to stabilize movement on uneven surfaces. The tract terminates on neurons of the ventral horn and lateral motor nuclei
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Electrocorticography
* Placing electrodes directly on the exposed surface of the brain to record electrical activity from cerebral cortex
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Electroencephalography
* Recording electrical activity along the scalp. Measures voltage fluctuations resulting from ionic current flows within the brain
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Magnetoencephalography
* Technique for mapping brain activity produced by electric currents in the brain using magnometers
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Positron emission tomography
* Nuclear medicine imaging technique that produces 3-D image by detecting pairs of gamma rays emitted indirectly by a positron-emitting radioisotope
91
Functional magnetic resonance imaging
* measures brain activity by detecting changes in blood flow.
* Uses the blood-oxygen-level dependent contrast
92
Functional connectivity MRI
* Technique in which the intensity of blood fluctuations in small regions of interest are charted over time
93
Auditory Pathway
* Sound information for localization, discrimination, and speech is carried through a series of contralateral and ipsilateral pathways
94
Aprosodias (definition, motor and sensory aprosodias)
* Disorders of speech affect
* Prosody in language refers to ranges of rhythm, pitch, stress, intonation and so on
* Motor aprosodia is characterized by inability of patient to produce or imitate facial gestures
* Sensory aprosodia is characterized by inability of patient to comprehend or repeat emotional gestures
* Strong correlation with the right hemisphere of the brain
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Aphasias
* Disorders of speech content
96
Types of aphasias: Broca's, Wernicke's, conduction, global, anomic, trans-cortical motor, and sensory
**Broca's**: Decreased verbal out, decreased sentence repeat, decreased naming
**Wernicke's**: Fluent verbal out, decreased sentence repeat, decreased comprehension, decreased naming
**Conduction** (between Wernicke's and Broca's areas): Fluent verbal out, decreased sentence repeat, decreased naming
**Global**: Decreased verbal out, decreased sentence repeat, decreased comprehension, decreased naming
**Anomic**: Fluent verbal out, decreased naming
**Trans-cortical motor**: Decreased verbal out, decreased naming
**Sensory**: Fluent verbal out, decreased comprehension, decreased naming
97
Language functions unique to left and right hemispheres
* Left hemisphere: Lexical and syntactic language, writing
* Right hemisphere: Prosodic aspects of language (can't speak, but can express emotions with hand gestures), and spatial abilities
98
Language gender differences in brain activity
* During phonological tasks, brain activation in males is lateralized to the left inferior frontal gyrus regions
* In females, the pattern of activation is different, engaging more diffuse neural systems that involve both the left and right inferior frontal gyrus
99
Musicians with vs. without perfect pitch
* Musicians with perfect pitch revealed stronger leftward planum temporale asymmetry than nonmusicians or musicians without perfect pitch
* The results indicate that outstanding musical ability is associated with increased leftward asymmetry of cortex subserving music-related functions
100
Hebb's postulate
* Coordinated activity of a presynaptic terminal and postsynaptic neuron strengthens the synaptic connection between them
101
Early vs. late language acquisition
* Comparing fMRI of early bilinguals and late bilinguals to examine the functional area differences.
* The language processing regions are separated spatially between the native language and the second language acquired in adulthood.
* When acquired early in development, the native and second language tend to be represented in _common fontal cortical areas_
* Also, late learners have overlapping Wernicke's area, but non-overlapping Broca's area; early learners have overlapping Broca's area
* The frontal lobe languge-processing regions (Broca's area), second languages acquired in adulthood (late bilingual subjects) are spatially separated from native languages. However, when acquired during the early language acquisigion stage of development (early bilingual subjects), nativ and second languages tend to be represented in common frontal cortical areas
102
Adult plasticity
* E.g., prism goggles experiment
* Shows that "use/experience" produces lasting functional changes
* Their persistence has a measurable half-life
103
Cerebellar afferent pathways (IN)
* Tracts carry information to the cerebellum from the spinal cord, vestibular apparatus, medulla, pons, and cerebral cortex
104
Cerebellar efferent pathways
* Fibers from cerebellum project to the brain stem and thalamus to modulate motor and other functions
105
Mossy fibers
* Major input cells to the cerebellum
* They synapse on neurons deep in cerebellar nuclei and granule cells
* The granule cells give rise to axons called parallel fibers, which then branch to synapse with the Purkinje cells
106
Synaptic changes that can occur during adult plasticity
* More transmitter released
* Interneuron modulation
* Increased postsynaptic sensitivity
* Increased pre- and post-synaptic areas
107
Neuromorphological plasticity
* Follows developmental sequences and developmental gradients
* Possibly a mechanism to interpret actual arrangement of inputs (periphery)
* Activity is a mechanism
* The **sensitive period** (time in the life of the organism during which these changes can occur) is limited, largely coincident with developmental events
108
Functional plasticity
* Follows developmental sequences
* Possibly a mechanism to interpret arrangements of the periphery to suppress nonsense and to correctly interpret the world as it is experienced
* Activity is a mechanism
* **Critical period(s)** are coincident with developmental events ending as late as puberty
109
Adult plasticity
* Follows experience over existing connections
* Can lead to adjustments consistent with altered inputs/experience to produce the correct response and to interpret inputs correctly
* These adjustments persist for minutes/hours but decay over similar time frames if not re-enforced
* There may also be changes in brain dimensions
110
Mood disorders & the subgenual cortex (and other brain regions involved)
* Seritonergic pathway
* Cortical region just below the corpus collosum
* Significant _reduction_ in blood flow to this region in persons with different forms of clinical depression
* Also significant reductions in the volumes of the subgenual cortex
* Significant blood flow _increases_ in regions of the frontal lobes, the amygdala, the thalamus, and the brainstem
* Core of the amygdala is smaller in persons with recurring depression
111
Schizophrenia
* Serotonergic (and dopaminergic) pathways
* Fewer serotonergic fibers in the frontal cortex of the brains of schizophrenics
* Significant reduction of length of axonal processes in the cortex
* Differences in brain activity for verbal fluency (hypofrontality) and "auditory" verbal imagery task
* Enlarged ventricles, smaller hippocampus, possible reduction in cerebral asymmetries
112
The Olds experiment & cocaine
* Dopaminergic pathways
* No stimulation of different parts of pathway as reward, rat would not walk across a shock grid, but would if it could be stimulated on the other side of the grid
* If you give coke to addicted people, changers occur in nucleus accumbens of sub-collosal cortex, amygdala, and substantia nigra (areas where Dr. Olds gave stimulation to rats)
113
Victor A. McKisick
* Studied Marfan Syndrome
* Tall, indented chest (pectus excavatum), long digits, cardiovascular problems
* Fibrilin - connective tissue
* Autosomal dominant
* Organized a catalog of human inherited conditions (which has grown a lot)
114
Intellectual and developmental disabilities (IDDs)
* Trisomy 21 (Down syndrome)
* Williams syndrome (deletion at 7q11)
* Many more
115
Williams syndrome vs. Down Syndrome
* Williams: poor on global organization (internal fine)
* Can draw individual structures well, but can't organize them into something meaningful
* Significant increases in parts of parietal lobe
* Greater mean cortical thickness
* Down: poor on internal detail (global fine)
* Can draw overall structure, but the smaller components are out of order
* Reduction in frontal lobe size
116
Abnormal spindle protein gene (ASPM)
* Loss of this gene correlates in humans with IDD with small brains
* Gene thought to play a role in control of brain size
