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104 Cards in this Set

  • Front
  • Back
What is controlled for voluntary movements?
Single parameters can be controlled: Force, position, velocity, acceleration, direction.
Contraction of skeletal muscle cells is controlled by the ______neuron.
alpha motor
The final common pathway means that all central neurons that have motor control must ultimately affect the activity of an alpha motor neuron to cause____.
A motor unit consists of
an individual motor neuron and all muscles fibers it innervates
The total group of motor units that innervates a muscle is referred to as its .
motor neuron pool
Dorsal horn contains neurons with mainly ______functions.
sensory e.g., the second order neurons of the anterolateral tract
The middle zone of the gray matter contains mainly ___ that connect convergent pools of neurons.
ventral horn of gray matter is primarily ____in function.
Motor neuron pools (innervation of all motor units in a muscle) - extend several________ segments
spinal cord
Somatotopic organization of the ventral gray matter (ventral horn): Lateral
- motor neurons of distal muscles of the segment
Somatotopic organization of the ventral gray matter (ventral horn):Medial
- motor neurons of proximal muscles of the segment
Somatotopic organization of the ventral gray matter (ventral horn):Dorsal
- motor neurons of flexors
Somatotopic organization of the ventral gray matter (ventral horn):Ventral
- motor neurons of extensors
Descending pathways are functionally grouped as ___or____: based upon sites of termination in the spinal cord gray matter
Lateral or Medial
lateral motor pathways, controlling distal muscles, are located in the cord in the ______white matter, near the neurons of distal muscles
Major medial system pathways
Vestibulospinal tract
Reticulospinal tract
Vestibulospinal tract - originates from _____.
vestibular nuclei;
this pathway is concerned with equlibrium and maintenance of posture (and therefore controls mainly proximal muscle groups.
Vestibulospinal tract
Reticulospinal tract - originates from the _____.
reticular formation;
controls motor neurons of proximal muscles, therefore a posture and equilibrium path
Reticulospinal tract
Major lateral system pathways
Rubrospinal tract
Corticospinal tract (Pyramidal tract)
Rubrospinal tract - originates from the ____.
red nucleus
projects to motor neurons controlling distal musculature
Rubrospinal tract
Corticospinal tract (Pyramidal tract) - originates from widespread areas of _____(not just major motor areas).
Projects to distal motor neurons. Has monosynaptic connection to some distal motor neurons--those with best control, e.g., muscles controlling independent digit movement, muscles of speech.
Corticospinal tract
Nature of the reflex arc:
sends input to the Spinal Cord (integrator).
Nature of the reflex arc:
Afferent input is then coupled to the ______.
Efferent(alpha motor neuron).
Nature of the reflex arc:
The axon of the Alpha motor neuron completes the arc, innervating the ___.
Skeletal Muscle
Carried out entirely within spinal cord, but modified by higher centers
reflex arc
Consequences of spinal cord transection Immediate result:
Immediate result: spinal shock
a. Loss of all reflexes - areflexia
b. Flaccid paralysis
c. Loss of autonomic function (urination, defecation reflexes)
d. Lasts 3-4 weeks in humans (less in other animals)
Consequences of spinal cord transection Long-term result
a. Slow return of reflex functions
b. Reflexes may strengthen over time: hyperreflexia
c. Paralysis may change to spastic paralysis
d. Pathological reflexes may appear (Babinski response)
increase in reflex strength that occurs over time is thought to be the result of
synaptic strengthening

new reflex connections form to take over the "empty" spots where neurons from higher centers in the brain used to synapse with the alpha motor neuron
Receptor: Myotatic (stretch) reflex
The muscle spindle: a length detector consists of;
Spindles found in all skeletal muscles
Spindles contain intrafusal muscle fibers
a. Nuclear bag fibers
b. Nuclear chain fibers
c. Normal muscle fibers called extrafusal (outside the spindle)
Sensory nerve fibers
Group Ia afferent nerve fiber
a. Innervates both types of intrafusal muscle fibers
b. Ending known as primary ending (annulospiral)
c. Activated by stretch of the muscle (change in length)
Sensory nerve fibers
Group II afferent nerve fiber
a. Innervates both types of intrafusal fibers
b. Ending known as secondary ending (flower spray)
c. Reflex role complex (we won't worry about this one)
Monosynaptic reflex arc (Fig. 9-8)
1. Group Ia fiber synapses with alpha motorneuron to same muscle
2. Reciprocal innervation of motor neurons to antagonist muscles
a. Requires disynaptic (2 synapses) inhibition of antagonist muscle motor neurons
b. Reciprocal innervation common to all reflexes
3. Single synapse allows very fast response
Descending control of the myotatic reflex: Gamma motor neurons: What is the purpose:
- set the sensitivity of the reflex
-change the length of the spindle during voluntary movement.
Two Gamma motor neuron types:
dynamic and static
Gamma motor neuron: dynamic
Enhances response to active stretching of muscle
Gamma motor neuron:static
Enhances response to new static length of the muscle
Alpha - Gamma coactivation:
During voluntary movement, brain sets proper length of spindle at the same time it sends commands to shorten to extrafusal muscle
Alpha - Gamma coactivation:
"brain" sends a command to alpha motor neurons to initiate a movement it also sends a command to the gamma motor neurons to "take up the slack" in the spindle as the voluntary movement occurs. This allows the spindle to operate normally no matter what the starting length of the skeletal muscle
Inverse myotatic reflex
Golgi tendon organ:
a force detector (in series with the muscle fibers)
Inverse myotatic reflex
Disynaptic reflex arc
Afferent nerve fiber: Group Ib afferent
-Disynaptic inhibition of the motor neurons of the same muscle
Inverse myotatic reflex Disynaptic reflex arc: Where does it synapse?
Synapses with interneuron in spinal cord:
Inverse myotatic reflex
Disynaptic reflex arc: The synapse causes
Disynaptic inhibition of the motor neurons of the same muscle
Inverse myotatic reflex
Disynaptic reflex arc:
Reciprocal innervation of motor neurons of antagonist muscles: facilitation of motor neurons of antagonist muscles
Inverse myotatic reflex
Serves protective function; also provides force control during voluntary movement
Inverse myotatic reflex
Golgi tendon organ: Describe it's protective function in the muscle
force or tension in a muscle increases, this reflex will attempt to inhibit the motor neurons of the muscle and cause it to lengthen--thereby protecting the muscle from tearing
Flexor withdrawal reflex
Nociceptors and associated A delta and C (Group III and IV) afferent nerve fibers
provide input to the spinal cord: designed to remove limb from painful stimulus
Flexor withdrawal reflex
Multisynaptic integration within the spinal cord:
1. Slower reflex due to many synaptic delays
2. More widespread output: motor neurons of many muscles may be affected
3. Reverberation may occur: keeps limb away from source of pain
4. Reciprocal innervation required
Flexor withdrawal reflex
Output usually facilitates motor neurons of flexors, inhibits motor neurons of extensors
Flexor withdrawal reflex
May have a crossed-extensor component
Medial Pathways
Vestibulospinal tract
Reticulospinal tract
Ventral corticospinal tract
Lateral Pathways
Lateral corticospinal tract (Pyramidal tract)
Rubrospinal tract*
Corticobulbar system has components comparable to medial and lateral systems
Lateral Vestibulospinal Tract
Lateral vestibular n.
Major input from utricle
Descends ipsilaterally in ventral funiculus
Primarily stimulates proximal extensors
Posture relative to linear accelerations, etc.
(Medial Vestibulosp. Tract)
Pontine Reticulospinal Tract
Origin: reticular formation (pons)
Widespread inputs
Descends ipsilaterally in ventral funiculus
Terminates on medial interneurons
Excites extensors, inhibits flexors
Control of posture
(Medullary reticulospinal tract)
Ruburospinal Tract
Origin: Red Nucleus in midbrain
Corticorubrospinal tract
Crosses midline
Does not extend beyond cervical level in humans
Distal flexors facilitated
RN may “initiate” some movements
Lateral Corticospinal Tract
60% frontal lobe
Areas 4, 6
These project mainly to ventral horn
40% parietal lobe
Areas 3a, 3b, 1, 2, 5, 7
These project mainly to dorsal horn (modulation of sensory input - “sensorimotor system?”)
Lateral Corticospinal Tract
Majority decussate (85%) forming lateral corticospinal tract
Ventral (anterior) CST is uncrossed, ends in upper cord
Some monosynaptic to distal flexors
Corticobulbar Fibers
Pyramidal tract sends axons to many cranial nerve nuclei
Predominately crossed system but significant bilateral distribution
Clinical Considerations: Lateral
Weakness in distal flexors
Babinski sign
No spasticity
Loss of fractionation of movement
PT Syndrome quite different
Clinical Considerations:
Decrease in proximal muscle tone
Impaired locomotion
Manipulation of digits not impaired
Primary Motor Cortex
Supplementary motor cortex
Premotor cortex
Prefrontal cortex
Basal ganglia
Posterior parietal association cortex
SI cortex
Premotor Cortex- Area 6
Somatotopic - 2 areas (rostral, caudal)
Controls groups of muscles
“Plans” movements (fires before MI, 80 ms)
Supplementary Motor Cortex
Bilateral movement control
Somatotopic (may have multiple representations
Programming for “nonsymmetrical” bilateral movements
Mental rehearsal increases blood flow
Parietal Lobe Contribution
SI contribution required
Posterior parietal lobe, Areas 5 and 7
Earliest activity for voluntary movement
Readiness potential
Integrates body position, sensory status, initiates “plan for voluntary movement
up to 800 ms before movement!
Upper Motor Neuron cause negative and positive signs
UMN->LMN-alpha motor
Distribution of Signs: Lower vs Upper Motor Neuron Disease
LMN +++ UMN ++
Distribution of Signs: Lower vs Upper Motor Neuron Disease
LMN +++ UMN +/-
Distribution of Signs: Lower vs Upper Motor Neuron Disease
LMN ++ UMN -
Distribution of Signs: Lower vs Upper Motor Neuron Disease
DTR Reflexes
LMN dec UMN inc
Distribution of Signs: Lower vs Upper Motor Neuron Disease
Muscle Tone
LMN dec UMN inc
Distribution of Signs: Lower vs Upper Motor Neuron Disease
LMN - UMN ++
Distribution of Signs: Lower vs Upper Motor Neuron Disease
Clasp-Knife Reflex
LMN - UMN ++
Overall Functions:
To monitor and make corrective adjustments to motor commands initiated elsewhere
Also participates in learning motor programs
Cortex covers 3 pairs of deep nuclei
Dentate N.
N. Interpositus
Fastigial N.
The Vermis & Flocculondular lobe control
Balance and Posture, work with the Vestibular
Cerebrocerebellum -> Dentate Nucleus -> To motor and premotor corticies
Motor Planning
Intermediate Hemisphere -> Interposed Nuclei -> To lateral descending Systems
Motor execution
Vermis -> Fastigial nuclei -> To Medial descending systems
Motor execution
Vestibulo Cerebellum -> to vestibular nuclei
Balance and eye movement
Cerebeller Disorders
Damage produces problems of
Synergy (asynergia)
Intention tremor
Lateral damage affects distal muscles; medial damage affect trunk (somatotopic)
Effects are ipsilateral
No sensory deficits are produced
Functions of the Basal Ganglia
To initiate and regulate gross intentional movements of the body
To provide appropriate background muscle tone for intended movements
Scaling of movements
Other non-motor behavior
Movement Disorders of the Basal Ganglia
General symptoms:
Change in muscle tone
Hyperkinetic or hypokinetic disorders
Hyperkinetic: dyskinesias
Hypokinetic: bradykinesia
Parkinson's Disease
Due to loss of cells making dopamine in the substantia nigra (imbalance in excitation and inhibition in basal ganglia)
Characteristics: (both hypo and hyperkinetic)
Tremor at rest
Bradykinesia (akinesia)
L-Dopa therapy; anticholinergic drugs, etc
Tissue transplant (fetal tissue; adrenal medulla cells)
Deep brain stimulation, etc.
Huntington's Chorea
Due to loss of GABAergic and cholinergic neurons in striatum
Autosomal dominant disorder
Decreased muscle tone
Choreiform movements (chorea: “dance”)
Due to loss of cells in cortex or caudate and putamen
Athetotic cerebral palsy
Increased muscle tone
Athetoid movements
Due to damage of the subthalamic nucleus
Decreased muscle tone
Ballistic movements
Usually gets better over time
Introduction - historical perspective
Overall Function - coordination and regulation of bodily functions needed for survival - homeostasis
Consists of central and peripheral structures
Consists of 2 (or 3) divisions
Sympathetic division
Parasympathetic division
Enteric nervous system
ANS Concepts
Critical role in maintaining homeostasis and permitting adaptation for almost every organ in the body
Sympathetic and parasympathetic often act as physiologic antagonists
The SNS is activated by changes in the environment; often discharges as a whole, orchestrating response to a threat
The ParaNS is generally continuously active coordinating the actions of several organs for specific functions, e.g., digestion, excretion
ANS is a target for many pharmacological interventions, e.g., hypertension, arrhythmia
Organized to mobilize the body for activity
Produces selective energy expenditure, catabolic functions and cardiopulmonary adjustments for intense activity
“Fight or Flight”
Organized for energy conservation
Reduces energy expenditure and increases energy stores
“Rest and Digest”
Somatic VS Autonomic Intervention: Somatic
One neuron
Somatic VS Autonomic Intervention:Autonomic
2 neuron chain
ACh at pre- to postganglionic synapse
Somatic VS Autonomic Intervention:Postganglionic transmitters differ
NE (sympathetic)
ACh (parasym.)
Origin of Peripherial ANS: SNS
Paravertebral and prevertebral ganglia
Origin of Peripherial ANS: PNS
S2, S3, S4
Ganglia near or in target tissue
Thoracolumbar System (T1 - L2 or L3)
Short preganglionic, long postganglionic
Synapse in paravertebral (chain) ganglia or via splanchnic nerves in prevertebral ganglia (e.g., celiac, superior mesenteric)
Characterized by divergence
Sympathetic “tone”
Exception: preganglionic innervation of chromaffin cells in adrenal medulla
SNS Neurotransmitters
Preganglionic - cholinergic (nicotinic)
Postganglionic - usually adrenergic
Exceptions: innervation of sweat glands cholinergic (except palms of hands)
Some smooth muscle in blood vessels of skeletal muscle are cholinergic
Adrenal Medulla - Epinephrine and NE
Receptor heterogeneity - Alpha and Beta
a1, a2, b1, b2, b3
Adrenal Medulla
Preganglionic innervation of chromaffin cells
Act as “postganglionics”
Release epinephrine, norepinephrine
Travel via blood to target receptors (Hormone)
Contributes to sympathetic tone
Craniosacral division
S2, S3, S4
Long preganglionic, short postganglionic
Synapse near or within target tissue
Less divergence
Little “tone” (except vagal tone at heart)
No innervation of body wall or limbs
Pre and postganglionics are cholinergic
PNS Intervention
Pre- to Postganglionic: nicotinic cholinergic
Postganglionic to target: muscarinic cholinergic
Autonomic Pharm
Multiple venues for manipulation:
Synthesis of transmitter(s)
Storage of transmitter(s)
Release of transmitters at ganglia and target organs
Binding of transmitters (receptor subtypes)
Removal of chemicals from receptors
Re-uptake or metabolism of transmitters