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NSC 201 > Unit 1: Neuroanatomy > Flashcards

Unit 1: Neuroanatomy Flashcards

1
Q

Neurobiology

A

Study of cells of the nervous system and the organization of these cells into functional circuits that process information and mediate behavior

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2
Q

Nissl Stain

A

Basic dyes stain nuclei of all cells as well as clumps surrounding the nuclei of neurons. Stain reacts with nucleic acids. Distinguishes between neurons and glia and arrangement of neurons

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3
Q

Golgi Stain

A

Silver chromate solution makes a small percentage of neurons become darkly colored

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4
Q

Grey matter

A

On surface in brain, neurons and synapses

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5
Q

White matter

A

Connects grey matter, myelinated, axons

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6
Q

Ben Franklin (1751)

A

Experiments and observations on electricity

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7
Q

Luigi Galvani and Emil du Bois-Reymond (1800)

A

Electrical stimulation of nerves causes muscle movement

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8
Q

Charles Bell and Francois Magendie (1810)

A

Dorsal roots of spinal cord carry sensory info into brain, ventral roots carry motor info out to muscles

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9
Q

Marie-Jean Pierre Flourens (1823)

A

Cerebrum: sensation/perception
Cerebellum: motor coordination (does not initiate movement but does it well)

Localization theory

Cut birds brains

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10
Q

Paul Broca (1861)

A

Left frontal lobe is responsible for the production of speech

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11
Q

Charles Darwin (1859)

A

Common behaviors: common mechanisms
Specialized traits: specialized mechanisms

Nervous system of different species evolved from common ancestors by natural selection

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12
Q

Reticular theory

A

Nerves are continuous (old theory)

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13
Q

Neuron doctrine

A

Nerve cells are separate, distinct entities (new theory). They communicate by contact, not continuity

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14
Q

Microscopes (early 1800s)

A

First opportunity to examine tissue at high magnification

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15
Q

Theodore Schwann (1839)

A

All tissues are composed of microscopic units called cells

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16
Q

Camilo Golgi (1873)

A

Soaked brains in silver chromate solution=Golgi stain=small percentage of neurons become darkly colored in their entirety (based on complexity, argued for reticular theory)

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17
Q

Santiago Ramon y Cajal (1900)

A

Used Golgi methods to draw out circuitry in many regions of the brain (advocate of neuron doctrine)

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18
Q

Electron microscope (1950s)

A

Uses electron beam instead of light to form better images, neurons in contact but no continuity (neuron doctrine wins)

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19
Q

Neuron

A

Dendrites (receive inputs from other neurons) –> soma (processes info) –> axon (transmits output of processing to other neurons)

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20
Q

How do neurons differ from other cells? (2)

A
  1. They stop dividing after birth

2. They have dendrites and axons (specialized structures designed to receive and transmit info)

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21
Q

What distinguishes cells from each other?

A

Specific parts of DNA that are used to assemble the cell (genes). DNA within every cell in the body is the same

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22
Q

Where does protein synthesis occur?

A

Ribosomes in cytoplasm. Ribosomes can be freely floating in cytosol or bound to rough ER

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23
Q

What is binding regulated by?

A

Transcription factors

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24
Q

Where are proteins that are synthesized in free ribosomes destined for?

A

Internal structures such as the cytosol, nucleus, and mitochondria

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25
Q

Where are proteins that are synthesized on rough ER destined for?

A

Inserted into plasma membrane or enclosed in vesicles to be released from neurons as neurotransmitters

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26
Q

What does the Golgi apparatus do?

A

Site of extensive “post-translational” chemical processing of proteins released from rough ER, also directs transmembrane and secretory proteins to their destination (soma, dendrites, or axon)

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27
Q

Mitochondria

A

Site of cellular respiration, import pyruvic acid oxygen, Krebs cycle and ETC, produces ATP

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28
Q

Neuronal Membrane

A

Barrier to enclose cytoplasm and exclude certain substances, phospholipid bilayer

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29
Q

What can DNA microarrays be used for?

A

Determine which genes are expressed uniquely in neurons, or which genes are more or less abundant in normal vs diseases brains

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30
Q

Important properties of genetic engineering (2)

A
  1. Target specificity (strand break)

2. Temporal control (inducible drugs)

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31
Q

Neurite

A

Includes many dendrites and one axon, designed to receive and transmit information

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32
Q

Axon characteristics

A

Constant radius, long and branch at right angles, have myelin sheath and transmit electro-chemical signals

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33
Q

Dendrite characteristics

A

Taper off in shape, shorter and branch profusely at all angles, no myelin sheath, receive electro-chemical signals

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34
Q

Roles of cytoskeleton

A

Gives shape to neuron (changes), mechanical support, aids in transport, allows cells to migrate, segregated chromosomes during cell division

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35
Q

What is tau?

A

A protein that allows for change in microtubules and helps neuron change shape continually

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36
Q

How is axon different from soma? (2)

A
  1. No ribosomes in axon= no protein synthesis

2. Protein composition of axonal membrane is fundamentally different than soma

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37
Q

How is the cytoplasm in the axon terminal different than in the axon proper? (3)

A
  1. Microtubules do not extend into terminal
  2. Terminal contains numerous small bubbles called synaptic vesicles
  3. Terminal contains many mitochondria (high energy needs because of long transport)
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38
Q

What way does information flow?

A

Pre to post synaptic side of synapse (axon terminal of one neuron to dendrite or soma of the next cell)

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39
Q

Why is axoplasmic transport needed?

A

Axons lack ribosomes so proteins are made in soma and shipped to axon, fast transport is in the microtubules

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40
Q

Anterograde

A

Towards the terminal: kinesin

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41
Q

Retrograde

A

Back to the soma: dynein

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42
Q

Tract Tracing

A

Used to trace the paths of axons

Anterograde: trace axons projecting away from cell bodies

Retrograde: trace axons projecting into area of cell bodies

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43
Q

Dendritic spines

A

Isolate various chemical reactions that are triggered by some type of synaptic activity, has free ribosomes in base of spine=protein synthesis

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44
Q

Glia cells

A

Outnumbers neurons 5:1, provides structure/metabolic support to neurons

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45
Q

Oligodendrocytes

A

Extensions rich in myelin, create myelin sheaths around axons in CNS

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46
Q

Schwann Cells

A

Similar in function of oligodendrocytes, but in PNS, can guide axonal regeneration

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47
Q

Microglia

A

Involved in response to injury or disease, exist in state of rest until activated

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48
Q

Astrocytes

A

Largest glia, star-shaped, many functions:

Form barrier to unwanted substances entering brain, control blood flow to neurons, maintain proper chemical state outside of neurons, removes waste, surround synapses and can modify neuronal signals, send nutrients (glucose) to neurons, digests old neuronal parts, secrets neurotransmitters and glialtransmitters

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49
Q

Central Nervous System Function

A

Interprets sensory input, initiates movement, and mediates complex cognitive processes

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50
Q

Peripheral Nervous System Function

A

Serves to bring sensory info into CNS (afferents) and carry motor signals out from CNS (efferents)

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51
Q

Rostral

A

Anterior- towards the front/nose

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52
Q

Caudal

A

Posterior- towards the back/tail

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53
Q

Ipsilateral

A

Structures on same side of head

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54
Q

Contralateral

A

Structures on opposite side of head

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55
Q

Sagittal cut

A

Left vs right

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56
Q

Horizontal (transverse) cut

A

Top vs bottom

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57
Q

Frontal (coronal) cut

A

Front vs back

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58
Q

Cross-section cut

A

Cut at right angle to spinal cord

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59
Q

3 major fissures (large grooves) in cerebrum

A
  1. Longitudinal 2. Central 2. Lateral

Divides hemisphere into four lobes: frontal, parietal, temporal, occipital

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60
Q

3 large gyri (bumps) in cerebrum

A
  1. Precentral 2. Postcentral 3. Superior temporal
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61
Q

Commissures

A

Fiber tracts in cerebral hemispheres, largest is corpus callosum

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62
Q

3 different areas of cerebrum

A
  1. Outer area of neuronal cell bodies (grey matter of cerebral cortex) 2. Inner area of myelinated axons (white matter) 3. Subcortical areas of grey matter
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63
Q

Ventricular system

A

Fluid-filled caverns and canals

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64
Q

Folium

A

Ridge or gyrus in the cerebellum

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65
Q

Diencephalon

A

Either side of third ventricle

  1. Thalamus
  2. Hypothalamus
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66
Q

Midbrain

A

Cerebral aqueduct

  1. Tectum
  2. Tegmentum
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67
Q

Pons

A

Below 4th ventricle

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68
Q

Medulla

A

Below 4th ventricle, continuous with spinal cord

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69
Q

Computer tomography (CT)

A

Measures opacity to x-rays

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70
Q

Magnetic Resonance Imaging (MRI)

A

Measures hydrogen atom response to magnetic fields

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71
Q

Diffusion Tensor Imaging (DTI)

A

Used to visualize large bundles of axons (track movement)

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72
Q

Positron Emission Tomography (PET)

A

Inject radioactive substance, have subject perform behavior, scan horizontal slice in brain

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73
Q

Functional Magnetic Resonance Imaging (fMRI)

A

No substance injected, have subject perform behavior, scan brain for de/oxygenated hemoglobin

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74
Q

Regions of the vertebral column (4)

A
  1. Cervical (8) 2. Thoracic (12) 3. Lumbar (5) 4. Sacral (5)

1 coccygeal

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75
Q

Dorsal root in spinal cord

A

Brings sensory information into the spinal cord (afferent), cell bodies in dorsal root ganglion

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76
Q

Ventral root in spinal cord

A

Carries motor information away from spinal cord (efferent), somas in cord

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77
Q

Sensory examples

A

Unipolar, dorsal, ascending, afferent

78
Q

Motor examples

A

Ventral, descending, efferent

80
Q

How do spinal cord areas differ than in the brain?

A

Grey matter is inside in H shape rather than outside. Outer area is white matter

81
Q

Spinal cord grey matter

A

Divided into dorsal and ventral horns, each contains prominent nuclear groups

82
Q

Meninges

A

Protects the brain and spinal cord from coming into contact with the bones (skull and vertebral column, respectively)

83
Q

Three membranes of meninges

A
  1. Dura matter 2. Arachnoid membrane 3. Pia mater
84
Q

Cerebrospinal fluid

A

Fills sub-arachnoid space covering brain and spinal cord, similar to blood but with few proteins and RBC or WBC, produced by choroid plexus in ventricles, supports the CNS and provides cushioning against injury

85
Q

Blood supplies from three main arteries

A
  1. Anterior 2. Middle 3. Posterior cerebral arteries

Receives input from vertebral and internal carotid arteries

86
Q

Spinal cord is supplied by three main arteries

A
  1. Anterior spinal artery 2. Right 3. Left posterior arteries
87
Q

Barriers in blood supply

A

Tightly packed endothelial cells, help maintain environment of CNS

Impedes passage of: foreign substances, proteins/other large molecules, highly charged molecules, hormones and neurotransmitters

Glucose actively transported

88
Q

Why is the barrier in blood supply weak in some areas?

A

Allows monitoring of chemical composition of blood

89
Q

Somatic (PNS)

A

Conscious, provides sensory and motor innervation, sensations such as light and pain, voluntary movements

90
Q

Autonomic (PNS)

A

Unconscious, regulates organ functions that maintain homeostasis, has 2 efferent components: sympathetic & parasympathetic

91
Q

Second stage neurons in autonomic

A

Far from target in sympathetic, but near target organ in parasympathetic

92
Q

Cranial Nerves Acronym

A

On Occasion Our Trusty Truck Acts Funny, Very Good Vehicle Any How

Some Say Marry Money, But My Brother Says Big Brains Matter Most
(S-sensory, M-motor, B-both)

93
Q

Major divisions of the brain (5)

A

Forebrain: 1. Telencephalon (cerebrum) 2. Diencephalon

Midbrain: 3. Mesencephalon

Hindbrain: 4. Metencephalon 5. Myelencephalon

94
Q

Layers of neocortex (6)

A
  1. Axons and dendrites, synaptic integration 2. Densely packed stellate cells and a few pyramidal (input/output to other areas) 3. Loosely packed stellate cells with intermediate sizes pyramidal cells (input/output) 4. Bands of densely packed stellate cells, no pyramidal (input from thalamus) 5. Very large pyramidal cells, few loosely packed stellate (output brainstem/spinal cord) 6. Pyramidal cells of various sizes, loosely packed stellate (output to thalamus)
95
Q

Pyramidal cells

A

Output neurons, excitatory

96
Q

What causes columnar organization?

A

Vertical axons and dendrites, parallel processing

97
Q

Stellate cells

A

Local circuit, both excitatory and inhibitory

98
Q

Korbinian Brodmann

A

Defined ~50 distinct regions of neocortex, different structures=different functions

99
Q

Neocortex has 3 parts

A
  1. Sensory 2. Motor 3. Association (higher-order)
100
Q

Brodmann areas and functions

A

MEMORIZE DIAGRAM ON SLIDE

101
Q

Fiber tracts in white matter (3)

A
  1. Association- connect gyri in same hemisphere (short and long) 2. Commissural- connect corresponding gyri in opposite hemispheres
  2. Projection- connect cerebrum with other parts of brain and spinal cord
102
Q

Subcortical areas (3)

A
  1. Basal forebrain 2. Basal ganglia 3. Limbic system
103
Q

Basal forebrain

A

Includes nucleus accumbens (motivation and rewards) and nucleus basalis (sleep-wake cycle and learning and memory)

104
Q

Basal ganglia

A

Includes caudate & putamen (striatum), gloves pallidus, subthalamus (diencephalon), and substantia nigra (mesencephalon)

Plays a role in selection of which of several motor actions to execute at any given time. Damage=Parkinson’s or Huntington’s

105
Q

Limbic system components (3) and overall function

A
  1. Cerebral cortex 2. Subcortical 3. Diencephalon

Basic motivations (hypothalamus), emotion (amygdala), and learning and memory (hippocampus)

106
Q

Cerebral cortex of limbic system

A

Made up of hippocampus and cingulate cortex

107
Q

Subcortical of limbic system

A

Made up of amygdala and septum

108
Q

Diencephalon of limbic system

A

Made up of hypothalamus, mammillary bodies, and anterior nuclei of thalamus

109
Q

Spinal cord white matter

A

Organized into various ascending (somatosensory) and descending (motor) tracts

110
Q

What is the thalamus separated by?

A

Lamellae (fibers; white areas)

111
Q

Functions of the thalamus (3)

A
  1. Process/relay somatic nervous system info to cerebral cortex
  2. Sleep/wake states
  3. Consciousness
112
Q

Ascending sensory inputs (5)

A
  1. Medial geniculate body-sends to auditory primary cortex
  2. Lateral geniculate body-sends to visual cortex
  3. VPN- projects to post central gyrus, processes touch
  4. Ventral lateral nucleus- input from cerebellum, do it well
  5. Ventral anterior nucleus- input from basal ganglia
113
Q

Functions of hypothalamus (3)

A

Primitive functions

  1. Motivates search for food, drink, sleep, temp, mates
  2. Controls activities of autonomic nervous system
  3. Links nervous system to endocrine system by synthesizing and secreting hormones
114
Q

Tectum

A

Roof, dorsal surface

Composed of superior and inferior colliculi

115
Q

Tegmentum (3 colorful nuclei and 2 tracts)

A

Aka cerebral peduncles

Colorful nuclei:

  1. Periaqueductal grey (cell bodies)
  2. Red nucleus
  3. Substantia nigra

Two major fiber tracts:

  1. Medial lemniscus
  2. Pyramidal tract
116
Q

Periaqueductal gray (cell bodies)

A

Pain modulation and defensive behavior

117
Q

Red nucleus (iron)

A

Motor coordination

118
Q

Substantia nigra (melanin)

A

Movement selection (part of basal ganglia)

119
Q

Medial lemniscus

A

Somatosensory fibers ascending to VPN of thalamus

120
Q

Pyramidal tract

A

Motor axons from primary motor cortex descending towards spinal cord

121
Q

Metencephalon

A

Pons and cerebellum

122
Q

Pons

A

Divided into dorsal and ventral pons

Dorsal: nuclei for 4 cranial nerves, sensory and motor functions

Ventral: pontine nuclei, receiving input from descending fibers of pyramidal tract, nuclei project axons into cerebellum via middle cerebellar peduncle

123
Q

Metencephalon

A

Cerebellum, connected to brain stem by cerebellar peduncles

  • Superior: primary output (VL thalamus; red nucleus)
  • Middle: input from contralateral motor cortex via pontine nuclei
  • Inferior: input from ipsilateral inferior olive
124
Q

Myelencephalon

A

Medulla oblongata, oldest portion of the brain

Ventral medulla surrounds central canal, dorsal medial is anterior to 4th ventricle

Connects higher levels of the brain to the spinal cord, regulates basic functions

125
Q

Medulla

A

Regulates basic autonomic functions

Contains dorsal column nuclei (cuneatus and gracilis; touch), solitary nucleus (taste), cochlear nucleus and ventral part of superior olive (hearing), inferior olivary nucleus (motor coordination)

126
Q

2 major fibers tracts in myelencephalon

A
  1. Medial lemniscus: ascending somatosensory fibers in dorsal column nuclei, axons cross brain stem and ascend to thalamus
  2. Medullary pyramids: descending motor axons from primary motor cortex
127
Q

Reticular Formation

A

Not a single structure, complex network of ~100 tiny nuclei that span the lower brainstem

128
Q

Functions of reticular formation

A

Sleep wake transitions, arousal/attention (reticular activating system), voluntary motor control, reward and addiction (ventral tegmental area), and mood (locus coeruleus, Raphe nuclei)

129
Q

Genetic and environmental causes of nervous system disorders (2)

A
  1. Gene copy number variation

2. Mutations in genes or regulation regions

130
Q

Phases of Development

A
  1. Ovum + sperm = zygote (cell division)
  2. Neurogenesis
  3. Structure formation
  4. Wiring the brain
131
Q

Germinal Stage

A

Potency:

  • Totipotent: fertilized egg–> morula
  • Pluripotent (embryonic stem cells): blastocyst
  • Multipotent; unipotent

End of stage: “baby in a compact disc”

132
Q

Gastrulation

A

Migration of blastocyst cells inward, leading to multiple distinct layers of tissue called germ layers

133
Q

Neurulation

A 
Nervous system emerges
Stages:
-Neural tube: CNS
-Inside tube: ventricles and spinal canal
-Neural crest: PNS
-Somite: skull and vertebrae
134
Q

Induction

A

When cells and tissues interact with one another to orchestrate developmental processes

135
Q

Mangold and Spemann (1924)

A

Embryonic induction, transplanted dorsal lip (future mesoderm, called the organizer) of one frog blastopore induced a second neural tube in a recipient frog embryo

136
Q

What causes induction of the neural plate?

A

Blockage of an inhibitory signal within ectoderm (process called disinhibition)

137
Q

How do cells become neurons?

A

When they dissociate, separated by removal of calcium from the medium

138
Q

Bone morphogenetic protein (BMP)

A

If added to dissociated culture dish, then cells develop into epidermis again. BMP inhibits (prevents) a neural fate

139
Q

What molecules interfere with BMP signals?

A

Released by dorsal lip in amphibians, blocks anti-neural effects of BMP, induces region of embryo to develop into neural tissue=brain and spinal cord

  • Ceberus (Cb)
  • Chordin (Chd)
  • Noggin (Nd)
  • Follistatin
140
Q

Neural Tube

A

Forms 2 plates

  1. Dorsal aspect of tube develops into roof plate in response to BMP being released by non-neural ectoderm. Releases BMP and Wnt
  2. Ventral part of tube turns into floor plate in response to release of SHH from notochord. Secretes SHH
141
Q

Is BMP sensory or motor?

A

Sensory (dorsal)

142
Q

Is SHH sensory or motor?

A

Motor (ventral)

143
Q

What does symmetrical cell division (cell proliferation) result in?

A

More radial glial cells

144
Q

What is neural still cell proliferation (symmetric cell division) and differentiation (asymmetric cell division) controlled by? (2)

A
  1. Morphogenetic factors

2. Cell-to-cell signaling

145
Q

Morphogens

A

Soluble molecules that diffuse and control cell fate decisions in a concentration-dependent fashion

146
Q

What does Notch do?

A

Suppresses differentiation in other cells (lateral inhibition)

147
Q

Lateral expansion

A

Symmetric, proliferation divisions, bigger

148
Q

Radial growth

A

Asymmetric, neuro genetic and differentiative divisions, thicker

149
Q

Gross Morphology

A

Proliferation and differentiation cause the neural tube to change its size and shape

150
Q

Where are shape changes (morphology) most pronounced?

A

Rostral end of tube (future brain and cerebellum)

151
Q

Temporal order of what the rostral end of the tube shows

A
  1. Three swellings which give rise to the forebrain, midbrain, and hindbrain
  2. Five dwellings which give rise to major divisions of the brain
152
Q

Milestones in morphological development of forebrain (4)

A
  1. Flexion forwards
  2. Posterior growth of telencephalic swellings so that they lie over, lateral to and fuse with diencephalon
  3. Sprouting from diencephalon of optic stalks and cups that give rise to optic nerves and retinas
  4. Sprouting from ventral surface of cerebral hemispheres of olfactory bulbs
153
Q

Milestones in the morphological development of midbrain (3)

A
  1. Dorsal surface (tectum) shows four bumps (colliculi)
  2. Floor of midbrain becomes tegmentum and projection fibers accumulate on lateral edges
  3. Cerebral aqueduct narrows
154
Q

Milestones in hindbrain (2)

A
  1. In metencephalon, tissue along dorsal-lateral wall grows to form rhombic lips and expands to form cerebellum
  2. In myelencephalon, ventral and lateral walls swell so 4th ventricle is at the roof and projection fibers pass along the ventral surface
155
Q

Where can neurogenesis be seen?

A

Olfactory bulb and hippocampus

156
Q

What two things govern migration of cells?

A

Time and location

157
Q

Migrating cells

A

Immature (lacks dendrites and axons)

158
Q

What are two major ways for a cell to migrate?

A
  1. Radial 2. Tangential
159
Q

Functions of radial glial cells (2)

A
  1. Progenitors to produce (by asymmetric cell division) neurons and glia 2. Migratory guides for the newly generated neurons
160
Q

Migration patterns (Spinal cord, PNS, brain)

A

Spinal cord: radial
PNS: tangential
Brain: radial (67%), tangential (33%)

161
Q

Corticogenesis

A

Formation of cortex (6 layers), preplate is created first which separates into marginal zone

162
Q

Protein Reelin

A

Released by Cajal-Retzius cells in marginal zone, allows newly arrived cells to pass through existing plates since cortex is assembled “inside-out”

163
Q

Neuro-progenitor cells (NPCs)

A

Initially express high levels of pro-neural genes. Later the level drops and NPCs become gliogenic

164
Q

What do gliogenic cells differentiate into?

A

First into astrocytes and then later into oligodendrocytes as Notch signaling decreases from high to low

165
Q

Which connections in the cortex are the most dense?

A

Connections “up” and “down” within thickness of cortex vs connections that spread side to side

166
Q

Protein semaphorin 3A

A

Secreted by cells in marginal zone, attracts dendrites and repels axons

167
Q

Cell fate decisions in spinal cord controlled by 3 morphogens

A

1 and 2. Release of BMP and Wnt from roof plate causes dorsally located neural precursor cells to develop into sensory neurons 3. Release of SHH from the floor plate induces ventrally located precursor cells to become motor neurons

168
Q

PNS development

A

Develops from neural crest cells; migration of precursor stem cells is tangential in nature

169
Q

What are cell fate decisions in PNS controlled by?

A

Complex spatiotemporal patterns of gene expression

170
Q

Aids to aggregation (3)

A
  1. Cell Adhesion Molecules (CAMs)
  2. Gap junctions pass cytoplasm between cells
  3. Morphogenic factors
171
Q

Cells in commissural plate

A

Cells release morphogens fibroblast growth factor (Fgf8) which affects expression level of transcription factors Pax6 and Emx2. Fgf8 (and Pax6) promotes development of anterior structures. Emx2 promotes development of posterior structures

172
Q

What happens if mice are engineered to produce less Emx2?

A

Expansion of anterior cortical areas such as motor cortex and shrinkage of posterior cortical area such as visual cortex

173
Q

What happens if Pax6 is knocked out?

A

Expansion of visual cortex (posterior) and shrinkage of motor cortex (anterior cortical area)

174
Q

Growth cone

A

Growing tip of a neurite. Has thin spikes called filopodia that extend and retract to probe the environment

175
Q

Chemoaffinity hypothesis

A

Neurons make connections with their targets based on interactions with specific molecular markers=follows guidance cues (ex: cutting optic nerve in frog)

176
Q

Multi step process of pathway formation (for axons-3)

A
  1. Pathway selection (to a structure)
  2. Target selection (to a sub-structure)
  3. Address selection (particular zone)
177
Q

Pathway formation depends critically on communication between cells (3)

A
  1. Long-range
  2. Short-range
  3. Neural
178
Q

Chemorepulsion/ contact repulsion

A

Long range: Semaphorins

Short range: Eph ligands, ECM (ex: tenascins)

179
Q

Chemoattraction/ contact attraction

A

Long range: Netrins

Short range: Ig CAMS, Cadherins, ECM (ex: laminins)

180
Q

Chemical guidance cues

A

Attract or repels, long-range or short-range

181
Q

Long range cues

A

Axons grow in dot to dot manner, once Netrin is high —> switch —> slit produced and repulses (Robo is a slit receptor)

182
Q

Short range cues result from two types of contact

A
  1. Direct cell to cell contact

2. Contact between cells and extra cellular secretions

183
Q

Ephrin signaling

A

Axons expressing the receptor eph are repelled by their contact with cellular membranes expressing ephrin

184
Q

Short range ECM

A

Secreted to provide structural support to tissue, axon elongation occurs if integrins on their surface bind to laminin proteins in ECM, travel is aided by fasciculation

185
Q

Synapse Formation

A

Process enhanced by presence of glial cells (especially astrocytes)

  1. Axon releases agrin
  2. Agrin binds to MuSK on muscle cell membrane
  3. MuSK activates rapsyn, promotes migration of postsynaptic acetylcholine receptors to synapse
  4. Muscle cell releases calcium, induces cytoskeletal changes in axon to assume morphology of terminal bouton
186
Q

Synapse Rearrangement

A

Diffuse pattern of synaptic contact is characteristic of early development, more focused pattern is present after synaptic rearrangement

187
Q

Synapse rearrangement- two mechanisms

A
  1. Apoptosis

2. Neural activity

188
Q

Apoptosis

A

Triggered if a neuron fails to obtain life preserving chemicals (ex: neurotrophins) supplied by its targets

189
Q

Hebbian modification

A

If one neuron is important to another, increases efficacy when pre synaptic and post synaptic neurons are coactive

190
Q

Growth is a consequence of (3)

A
  1. Synaptogenesis
  2. Myelination
  3. Dendritic branching
191
Q

Many opportunities for experience to influence development (3)

A
  1. Deprivation vs enrichment
  2. Critical period
  3. Sensitive period

NSC 201 (5 decks)

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