study guide exam 3 Flashcards by sophia rahman

aka ventral horn neurons innervates the skeletal muscles of the head and body

LMN

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Functions: to commend for movement (reflexive or voluntary)

LMN

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sensory neuron to lower motor neuron WITHOUT involvement of the upper motor neuron in cortex

reflexive movement

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what are the neuronal types of reflexive movement

LMN, sensory, interneurons, brainstem UMNs

**NOT cortical UMNs

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all the motor neurons innervating a single muscle are grouped together into a rod-shaped cluster

motor neuron pool

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Proximal muscles –> medial LMNs with____ ____ control

body postural

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distal muscles –> lateral LMNs w/ ___ ____ ___

skilled voluntary movement

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the axon form a single alpha motor neuron branches within muscles to synapse on many extrafusal fibers

motor unit

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generates small forces, most resistant to fatigue, low threshold for activation (tonically active and sustained effort)

slow motor unit

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generates large force + easily fatigued

Fast Fatigable (FF) motor units

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medium force + resistant to fatigue

Fast fatigue-resistant (FR) motor units

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gradual increases in muscle tension (or force) results from the progressive recruitment of motor units in a fixed order (S –> FR–> FF)

size principle

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maintain muscle length at a desired level ex. knee jerk reflex

muscle stretch reflex

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maintain muscle tension (force) at a desired level ex. weight lifting

Golgi tendon reflex

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Biological neural networks that produce rhythmic patterned outputs for locomotion without sensory feedback & without descending UMN

central pattern generators (CPGs)

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encode movements in central personal space, purposeful/pre-programmed movements, population coding *purposeful movements instead of contractions

primary motor cortex

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movements that are oriented toward extra personal space

premotor cortex

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stabilizing head position (vestibulo-cervical reflex)

MEDIAL vestibular nucleus

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stabilizing posture after existing unanticipated postural instability (vestibulo-spinal reflex)

lateral vestibular nucleus

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stabilizing posture to anticipated postural instability

reticular formation

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orienting head and eye movements (saccade)

superior colliculus

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anterior medial white matter and terminate in medial cell groups in both sides (functions: govern posture and balance mechanism of axial muscles)

UMNs in brainstem

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lateral white matter + terminate in lateral cell groups in contralateral side (functions: skilled voluntary movements of distal extremities)

UMNs in motor cortex

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contains over 90% of the fibers present in the corticospinal tract and runs the length of the spinal cord. The primary responsibility of the lateral corticospinal tract is to control the voluntary movement of contralateral limbs

lateral corticospinal tact

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Encode movements but not muscle contractions Encode intentions for movements in central personal space These movements are purposeful/preprogrammed movements Population encoding

general functional organization of the primary motor cortex

subset of UMNs in premotor cortex fire in both planning and observations of the particular movements being performed by others

Mirror motor neurons

Medium spiny neurons in caudate and putamen receive inputs from which two brain regions?

Cerebral cortex + substantia nigra pars compacta

What are the main sources of output from the basal ganglia to upper motor neurons in motor cortex or superior colliculus?

Globus pallidus and substantia nigra pars reticulata

sequence of events that occur during the function of the basal ganglia circuit indirect (stop)

Striatum D2R MSNs -> GPe -> STN -> GPi -> Thalamus

sequence of events that occur during the function of the basal ganglia circuit direct (GO)

Striatum D1R MSNs -> GPi -> Thalamus

loss of ____ neurons in substantia nigra pars compacta causes Parkinson's disease

dopamingeric

How does loss of dopaminergic inputs to striatum (caudate/putamen) cause hypokinetic symptoms in Parkinson’s disease?

Causes an increase of activity of the indirect pathway and diminishes the direct pathway

What are the effects of hypokinetic disorders on movement control pathways

Effects of hypokinetic disorders -> overactivity of indirect pathway, and underactivity of direct pathway ---> more tonic inhibition of thalamus.

Huntington’s disease is caused by degeneration of medium spiny neurons used which type of the dopamine receptor?

Globus Pallidus External (D2R)

How does degeneration of the basal ganglia circuits cause hyperkinetic symptoms in Huntington’s disease?

There is a loss of inhibitory input from caudate/putamen -> abnormally activation of globus pallidus external -> diminished excitatory subthalamic output to globus pallidus internal -> less tonic inhibition of thalamus -> increased excitation of motor cortex neurons ->

What are the effects of hyperkinetic disorders on movement control pathways

undesired choreiform (“dancelike”) movement in HD

What are the three parts of cerebellar cortex, their input sources and how do they receive inputs?

1. cerebrocerebellum 2.spinocerebellum 3.Vestibulocerebellum

receives input indirectly from the cerebral cortex via pontine nuclei

Cerebrocerebellum

receives input directly from spinal cord and brainstem

Spinocerebellum

receives input from vestibular nuclei

Vestibulocerebellum

When considering the functional organization of the cerebellum and the cerebral cortex, one should determine which is associated with ipsilateral representation and which is associated with contralateral representation

Cerebellum is concerned with ipsilateral representation whereas cerebral cortex is concerned with contralateral representation

long term learning and memory

Function of inferior olive

Includes the dentate nucleus, two interposed nuclei, fastigial nucleus: each of these nuclei receives input from a different region of the cerebellar cortex and then sends outputs to upper motors neurons in motor cortex (via thalamic relay) or brainstem

deep cerebellar nuclei

main output sources

mossy fibers

mossy fibers synapse on cerebellar granule cells which then give rise to axons to help form excitatory synapses with Purkinje cells.

Parallel fibers

axons of the modulatory input from inferior olive form that help form excitatory synapses with Purkinje cells

Climbing fibers

convey main inputs

Parallel fibers

convey modulatory inputs

Climbing fibers

Main inputs from cortex, spinal cord, and vestibular system -> mossy fiber > parallel fiber -> Purkinje cell -> deep cerebellar nuclei -> output -> correct motor errors for ongoing movements.

Parallel fiber pathway

modulatory inputs from inferior olive -> climbing fiber -> Purkinje cell -(motor learning and memory)-> deep cerebellar nuclei -> output -? Encode motor learning and memory

Climbing fiber pathway

controls expression of segmentation of hindbrain and spinal cord in human

Homeobox

regulates cell movements for lengthening the neural plate and neural tube

Noncanonical pathway

play roles in the initial specification of the neural plate (neural induction) and the subsequent differentiation of the dorsal part

bone morphogenetic proteins

endogenous antagonists that modulate BMP signaling

noggin and chordin

mutations in Shh holoprosencephaly Establishing neuronal identity, particularly motor neurons in the ventral portion of the spinal cord and hindbrain (ventralizing signal)

sonic hedgehog

key regulators of neural stem cell decisions to generate either additional stem cells or postmitotic neurons

Delta/Notch signaling

influence the detachment of neurons from the radial glia

Reelin

How do inductive signals establish neuron identity

Diffusible inductive signals

transcriptional factors that are expressed in each cell that are mediated by diffusible inductive signals as well as local cell-cell signals

Transcriptional code

slow division, self renew

symmetrical

transit amplifying cells that are molecularly distinct from slowly diving radial glial stem cells

Asymmetric

first born cells are eventually located in the deepest layers and later born neurons migrate radially, travelling through the older cells and coming to lie superficial to them (located in more superficial layers)

Inside out manner

How are the final fates of neural crest cells determined?

Proper exit (initial positional identity) Proper migration through terrain that provides instructive + trophic signals

What are the two major functions of radial glial cells in the developing CNS?

1. Acting as migratory guides 2. They are neuronal progenitor (stem) cells in the developing cortex

Location of lower motor neurons in the spinal cord

Located in the VENTRAL HORN of spinal cord gray matter

what is the sequence of events of the general steps for construction of neural circuits?

1. Neuronal polarization 2. Axon outgrowth: growth cone 3. Axon guidance and targeting 4. Synapse formation (aka. Synaptogenesis) 5. Neuronal survival and synapse maturation (synapse elimination + refinement) --> neuronal survival and synapse maturation is regulated bu neurotrophins and neural activity

41. What are the five members of the neurotrophin family?

* Nerve growth factor (NGF) * Brain derived neurotrophic factor (BDNF) * Neurotrophin-3 (NT-3) * Neurotrophin 4 & 5 (NT- 4/5)

How does the growth cone regulate its motility?

Axon guidance and targeting; axon guidance molecules

distributed preferentially in the nascent axon to define the axon **neuron polarization

pars protein

chemoattractant

netrin

chemorepellent + has receptor robo

slit

associated with the bundling or fasciculation of groups of axons

L1 CAM

constitute a cell-cell recognition code & initiate bidirectional signaling

Ephrin/Eph

mediators of synapse identity + synapse specificity

Protocadherin

binds to ErB receptors on postsynaptic cells to elicit increased synthesis and insertion of NT receptors

* Neuregulin 1

helps localize synaptic vesicles, docking proteins and fusion molecules in the presynaptic active zone

* Neurexins

Notochord formation -> induction of neuroectoderm and formation of neural plate -> folding of neural plate to form the neural tube and specification of neural crest

sequence of events of neurulation

* Neurons and glia of the sensory and autonomic ganglia * Neurons of the enteric nervous system

progeny of neural crest cells (or cell types derived from neural crest cells)

Telencephalon gives rise to the cerebral cortex and hippocampus gives rise to basal ganglia

* Prosencephalon

Midbrain tegmentum, superior, and inferior colliculi

* Mesenephalon

Cerebellum, pons, and medulla

* Rhombencephalon

failure of the prosencephalon to divide into two cerebral hemispheres

* Holoprosencephaly

Sources of inductive signals for the induction and patterning of the nervous syste

* Notochord * Floorplate * Roofplate * Neuroectoderm * Adjacent mesodermal tissues such as somites