- spread by fecal-oral route - attaches to receptors in cells of small intestine - diarrhea and/or upset stomach

Lecture 8 Flashcards by Karolina Kowalczyk

muscle contractions and relaxations that are rapid, stereotyped, involuntary, and coordinated (knee jerk, swallowing, pain withdrawal)

reflex responses

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initiation and termination are

voluntary and triggered by peripheral stimuli (running, walking, chewing)

rhythmic motor patterns

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initiated movements to accomplish a specific goal; largely learned movements that improve with practice (as one learns to anticipate and correct for environmental obstacles)

voluntary movements

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What is the upper motor system responsible for?

planning and selecting movements

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What is the lower motor system responsible for?

executing movements

* simple sensory-motor reflexes

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measures electrical activity in muscles

EMG - electromyograph

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type of motor neurons that originate in ventral horn of spinal cord; form the “final common pathway”

Aα type

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Each Aα type motor neuron innervates fibers within a ___. Each muscle fiber innervated by a ___.

single muscle

single motor neuron

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All motor neurons innervating a single muscle are grouped in clusters called ____.

motor pools

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Motor pools are located with a slight spread along the ____.

anterior-posterior axis

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Describe the proximal to distal spatial map for the ventral horn.

Distal muscles are located at the outer edges, axial muscles are located toward the center

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Describe the flexor to extensor spatial map for the ventral horn.

Flexors are located more dorsal (towards back), extensors are located more ventral (towards front)

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What are some characteristics of lower motor neuron diseases?

decreased tone, weakness, retardation of movement, hyporeflexia, and muscle wasting

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How is polio spread?

spread by fecal-oral route
attaches to receptors in cells of small intestine
diarrhea and/or upset stomach

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Polio that stops at the GI tract

abortive poliomyelitis

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15% of polio cases result in this

aseptic meningitis

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____ occurs in __% of cases. It targets motor neurons to cause muscle weakness (~__% of nerves affected. Nerve death results in ___. Progression stops only when ___ (paralysis is permanent).

paralytic poliomyelitis
1-5
50
paralysis
immune system overcomes the virus

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ALS (___) is the result of both genetic and spontaneous mechanisms. It can results from mutations in ___, which is __. It causes hardening of ___.

Amyotrophic lateral sclerosis
SOD1
autosomal dominant
lateral corticospinal columns

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What are the symptoms of ALS?

muscle wasting
hyper-reflexia (combination of both upper and motor neuron signs of disease)
increasing muscle weakness (especially in arms and legs)
clumsiness
muscle cramps and spasms
difficulty speaking, swallowing, and breathing

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lower motor neuron and all the muscle fibers it innervates

motor unit

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____ are small fibers and with small motor units. “Red” fibers contract slowly but are relatively ____. They are rich in ___ (oxidative phosphorylation) and allow for ____ (e.g., posture).

slow (S), aka Type I
resistant to fatigue
mitochondria
sustained muscle contraction

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___ are large fibers and involve larger, more powerful motor units. They are the larger pale muscle fibers. The contain sparse mitochondria (use ___ instead) and are ____.

fast fatigable (FF), aka Type IIa
mitochondria
glycolysis
easily fatigued

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__ fibers are intermediate in size and ___ than FF but ___.

fast fatigue-resistant (FR), aka Type IIb
slower
less fatigable

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What is Henneman’s Size Principal?

That fibers are recruited in order of size. Aka., low stimulation – only Type I fibers, then IIb, then IIa. There is a range of forces to perform different motor tasks. The largest motor units recruited only when maximum force is needed

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Describe (temporal) summation in muscle fibers.

muscle fiber activated by new AP before relaxed from the previous AP --> produce more force; forces generated by temporally overlapping contractions are summed

tereotyped movements elicited by activation of skin or muscle receptors

spinal reflexes

innervate extrafusal muscle fibers; generate forces needed for movement

α motor neurons

innervate intrafusal muscle fibers; embedded within connective tissue of muscle; innervated by both sensory and motor neurons; report info about length and tension of muscle

γ motor neurons

sensory organ for determining muscle length and stretch; embedded in muscle

muscle spindle

During the stretch (___) reflex, discharge of ___ occurs related to ___ of muscle. When muscle stretched, it ___ firing rate. When muscle is shortened (goes slack), it ____ firing rate. Ia axon synapses on ___ and is ____.

``` myotatic Ia sensory axons length increases decreases alpha motor neuron monosynaptic ```

large diameter sensory fibers coiled around muscle spindles; thickest myelinated axons in body; fastest

Ia sensory axons

Stretch imposed on a muscle stretches ___ --> activates mechanically gated ion channels in ___ and initiates an AP. These sensory neurons synapse with ___ in the same muscle and with synergistic muscles in ___. The sensory neurons activate local ___ connections for ___ muscles.

``` intrafusal muscle fibers Ia axons motor neurons spinal cord ventral horn inhibitory antagonistic ```

a polysynatpic reflection that compensates posture during withdrawal from pain

flexor (withdrawal) reflex

During the flexor reflex, pain axon enters spinal cord and activates ____, which eventually excite ___ that control ___ muscles of affected limb. Other ___ inhibit ___ that control ___.

``` interneurons alpha motor neurons flexor inhibitory interneurons alpha motor neurons extensors ```

A reflex that activates extensor muscles and inhibit flexor muscles on the opposite side in response to a flexor reflex

crossed extensor reflex

inhibition that compensates for the excess load imposed by limb withdrawal

reciprocal inhibition

limb is extended and in | contact with the ground (can get quicker)

stance phase

limb is flexed to leave the ground and then brought forward to bring the next stance phase (stays relatively constant)

swing phase

Where are central pattern generators (CPG) located?

spine

individual neurons whose membrane properties allow them to generate rhythmic activity

pacemaker neurons

Pacemaker neurons neuron possesses both __ | channels and ___ channels. They will fire rhythmically when stimulated with ____.

Ca2+-activated K+ NMDA glutamate

Pacemaker neurons have regular __ channels to generate APs. NMDA channel blocked by ___ at hyperpolarizing membrane potential. Internal __ dissipates and __ channel shuts off. ___ block is removed upon depolarization.

``` voltage-gated Na+ and K+ Mg2+ Ca2+ Ca2+ -activated K+ Mg+2 ```

axons from ___ descend to influence local circuits in brainstem and spinal cord

upper motor neurons

What areas do upper motor pathways include?

-brainstem centers -cortical areas in frontal lobe

The brainstem is especially important for ___.

postural control

The motor and premotor cortex are responsible for ___.

planning and precise control of voluntary movement

The ___ is responsible for balance and posture; receives input from brainstem ___.

medial ventral horn | bilaterally

The ____ is responsible for voluntary movement of distal extremities; its controlled by ___ motor cortex (distal muscles operate independently).

lateral ventral horn | contralateral

The primary motor cortex is located in the ___. It receives input from __, ___ (incorporates multiple sensory modalities, used for planning). It controls the ___ side of the body and uses ____.

``` precentral gyrus S1 posterior parietal contralateral topographic organization ```

over-representation of brain regions that are required for most complicated motor behaviors (i.e., more space given to fine motor control)

homunculus

The primary motor cortex has _ layers; layer V is the ___. It is mapped the same way that sensory cortex is mapped. The ___ is essential in planning movements but does not provide direct input to __; coordinates movements in space.

6 output layer (pyramidal cells) posterior parietal spinal cord

The direct pathway from the cortex to the spinal cord is the ___. Axons cross in the __ and innervate the ___ ventral horn.

corticospinal tract medulla opposite

The indirect pathway from the cortex to the spinal cord is the ___. It allows for ___, especially for axial and proximal muscles.

corticoreticulospinal tract | postural adjustments

adjacent to primary motor cortex, extensive reciprocal connections; projects directly to spinal cord

premotor cortex

In the premotor cortex, neurons fire ___; responsible for conditional motor tasks that pair movement with a ____.

earlier | visual cue

neurons fire before initiation of task; cells fire when just thinking about an event

intention

What are the symptoms of upper motor neuron lesions?

``` weakness spasticity increased tone hyperactive deep reflexes clonus Babinski's sign loss of fine voluntary movements ```

What are the symptoms of lower motor neuron lesions?

``` weakness paralysis decreased superficial reflexes hypoactive deep reflexes decreased tone fasciculations and fibrillations severe muscle atrophy ```

influence movements through upper motor neurons

basal ganglia

What are the 3 main nuclei of the basal ganglia?

caudate, putamen, globus pallidus

The basal ganglia form a loop with the ___ and the ___ to link the cortex with ___. They are required for ___.

substantia nigra subthalamic nucleus upper motor neurons voluntary movements

Inputs to caudate and putamen from the cortex are ____. They also receive ___ inputs from substantia nigra. Interneurons and thalamic neurons form ___.

excitatory (glutamatergic) dopaminergic inhibitory synapses

Neurons in the basal ganglia fire in anticipation of a ___ (putamen = ___, caudate = ___).

movement body movements eye movements

Caudate and putamen send inbihitory GABAergic projections to...?

– globus pallidus (internal and external segments) | – substantia nigra (pars reticulata)

GPi (globes pallidus) neurons project back to cortex via ____.

thalamus

When striatal neurons fire (in anticipation of movement), they ____. This allows upper motor neurons to send commands to lower motor neurons to ___.

inhibit the inhibition (i.e., disinhibition) | initiate movement

Spontaneous activity of the GABAergic GPi and pars reticulata neurons prevents ____.

unwanted movements

In the indirect pathway, the striatum projects to ___, then to ____. STN projects to ___, then to ____. STN projections are ____, which increases inhibition of GPi. (does the OPPOSITE of direct pathway!)

``` globus pallidus external nuclei subthalamic nuclei of central thalamus Gpi thalamus excitatory ```

Striatal neurons from the substantial nigra that project to GPi have __ receptors (___). Striatal neurons that project to GPe have __ receptors (____)

D1 excitatory D2 inhibitory

Dopamine ___ the direct pathway and ___ the indirect pathway.

excites | inhibits

Huntington's Diseases is entirely ____ and ____.

genetic | autosomal dominant

In Huntington's disease, the coding region has an abnormal amount of ____. This gets larger with each ___. This leads to the selective loss of ___, and in turn, the loss of inhibition of ___. This results in increased stimulation of ____ by basal ganglia.

``` CAG repeats generation stratal GABAergric neurons GPe motor cortex ```

What are the symptoms of Huntington's?

rapid, jerky movements with no clear purpose (chorea) | psychiatric symptoms as well

A neurodegenerative movement disorder that usually develops after age 50

Parkinson's Disease

What are the symptoms of Parkinson's?

``` difficulty walking, movement and coordination tremor rigidity akinesia postural instability ```

In Parkinson's, ____ are destroyed over time. ___ accumulates in deposits called ___ within dopamine neurons.

dopaminergic neurons alpha-synuclein Lewy bodies

Parkinson's is usually ___ but it has once been tied to ____ due to influenza. In 1976, contaminated batches of synthetic heroin (MPTP instead of MPPP) led to ____.

genetic molecular mimicry drug-induced Parkinson's

In Parkinson's, you lose dopaminergic neurons in ____, which decreases the ___ pathway and increases the ___ pathway. This leads to decreased stimulation of motor cortex by ____.

SN pars compacta direct indirect basal ganglia

What are the most popular treatments for Parkinson's?

L-dopa (can cross BBB) | sub thalamic deep brain stimulation

Lecture 8 Flashcards

(79 cards)