Physiology Motor

Front 1

What is controlled for voluntary movements?

Back 1

Single parameters can be controlled: Force, position, velocity, acceleration, direction.

Front 2

Contraction of skeletal muscle cells is controlled by the ______neuron.

Back 2

alpha motor

Front 3

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____.

Back 3

movement

Front 4

A motor unit consists of

Back 4

an individual motor neuron and all muscles fibers it innervates

Front 5

The total group of motor units that innervates a muscle is referred to as its .

Back 5

motor neuron pool

Front 6

Dorsal horn contains neurons with mainly ______functions.

Back 6

sensory e.g., the second order neurons of the anterolateral tract

Front 7

The middle zone of the gray matter contains mainly ___ that connect convergent pools of neurons.

Back 7

interneurons

Front 8

ventral horn of gray matter is primarily ____in function.

Back 8

motor

Front 9

Motor neuron pools (innervation of all motor units in a muscle) - extend several________ segments

Back 9

spinal cord

Front 10

Somatotopic organization of the ventral gray matter (ventral horn): Lateral

Back 10

- motor neurons of distal muscles of the segment

Front 11

Somatotopic organization of the ventral gray matter (ventral horn):Medial

Back 11

- motor neurons of proximal muscles of the segment

Front 12

Somatotopic organization of the ventral gray matter (ventral horn):Dorsal

Back 12

- motor neurons of flexors

Front 13

Somatotopic organization of the ventral gray matter (ventral horn):Ventral

Back 13

- motor neurons of extensors

Front 14

Descending pathways are functionally grouped as ___or____: based upon sites of termination in the spinal cord gray matter

Back 14

Lateral or Medial

Front 15

lateral motor pathways, controlling distal muscles, are located in the cord in the ______white matter, near the neurons of distal muscles

Back 15

lateral

Front 16

Major medial system pathways

Back 16

Vestibulospinal tract
Reticulospinal tract

Front 17

Vestibulospinal tract - originates from _____.

Back 17

vestibular nuclei;

Front 18

this pathway is concerned with equlibrium and maintenance of posture (and therefore controls mainly proximal muscle groups.

Back 18

Vestibulospinal tract

Front 19

Reticulospinal tract - originates from the _____.

Back 19

reticular formation;

Front 20

controls motor neurons of proximal muscles, therefore a posture and equilibrium path

Back 20

Reticulospinal tract

Front 21

Major lateral system pathways

Back 21

Rubrospinal tract
Corticospinal tract (Pyramidal tract)

Front 22

Rubrospinal tract - originates from the ____.

Back 22

red nucleus

Front 23

projects to motor neurons controlling distal musculature

Back 23

Rubrospinal tract

Front 24

Corticospinal tract (Pyramidal tract) - originates from widespread areas of _____(not just major motor areas).

Back 24

cortex

Front 25

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.

Back 25

Corticospinal tract

Front 26

Nature of the reflex arc:
sends input to the Spinal Cord (integrator).

Back 26

Afferent

Front 27

Nature of the reflex arc:
Afferent input is then coupled to the ______.

Back 27

Efferent(alpha motor neuron).

Front 28

Nature of the reflex arc:
The axon of the Alpha motor neuron completes the arc, innervating the ___.

Back 28

Skeletal Muscle

Front 29

Carried out entirely within spinal cord, but modified by higher centers

Back 29

reflex arc

Front 30

Consequences of spinal cord transection Immediate result:

Back 30

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)

Front 31

Consequences of spinal cord transection Long-term result

Back 31

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)

Front 32

increase in reflex strength that occurs over time is thought to be the result of

Back 32

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

Front 33

Receptor: Myotatic (stretch) reflex
The muscle spindle: a length detector consists of;

Back 33

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)

Front 34

Sensory nerve fibers
Group Ia afferent nerve fiber

Back 34

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)

Front 35

Sensory nerve fibers
Group II afferent nerve fiber

Back 35

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)

Front 36

Monosynaptic reflex arc (Fig. 9-8)

Back 36

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

Front 37

Descending control of the myotatic reflex: Gamma motor neurons: What is the purpose:

Back 37

- set the sensitivity of the reflex
-change the length of the spindle during voluntary movement.

Front 38

Two Gamma motor neuron types:

Back 38

dynamic and static

Front 39

Gamma motor neuron: dynamic

Back 39

Enhances response to active stretching of muscle

Front 40

Gamma motor neuron:static

Back 40

Enhances response to new static length of the muscle

Front 41

Alpha - Gamma coactivation:

Back 41

During voluntary movement, brain sets proper length of spindle at the same time it sends commands to shorten to extrafusal muscle

Front 42

Alpha - Gamma coactivation:

Back 42

"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

Front 43

Inverse myotatic reflex
Golgi tendon organ:

Back 43

a force detector (in series with the muscle fibers)

Front 44

Inverse myotatic reflex
Disynaptic reflex arc

Back 44

Afferent nerve fiber: Group Ib afferent
-Disynaptic inhibition of the motor neurons of the same muscle

Front 45

Inverse myotatic reflex Disynaptic reflex arc: Where does it synapse?

Back 45

Synapses with interneuron in spinal cord:

Front 46

Inverse myotatic reflex
Disynaptic reflex arc: The synapse causes

Back 46

Disynaptic inhibition of the motor neurons of the same muscle

Front 47

Inverse myotatic reflex
Disynaptic reflex arc:

Back 47

Reciprocal innervation of motor neurons of antagonist muscles: facilitation of motor neurons of antagonist muscles

Front 48

Inverse myotatic reflex

Back 48

Serves protective function; also provides force control during voluntary movement

Front 49

Inverse myotatic reflex
Golgi tendon organ: Describe it's protective function in the muscle

Back 49

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

Front 50

Flexor withdrawal reflex

Back 50

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

Front 51

Flexor withdrawal reflex
Multisynaptic integration within the spinal cord:

Back 51

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

Front 52

Flexor withdrawal reflex

Back 52

Output usually facilitates motor neurons of flexors, inhibits motor neurons of extensors

Front 53

Flexor withdrawal reflex

Back 53

May have a crossed-extensor component

Front 54

Medial Pathways

Back 54

Vestibulospinal tract
Reticulospinal tract
Ventral corticospinal tract

Front 55

Lateral Pathways

Back 55

Lateral corticospinal tract (Pyramidal tract)
Rubrospinal tract*
Corticobulbar system has components comparable to medial and lateral systems

Front 56

Lateral Vestibulospinal Tract

Back 56

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)

Front 57

Pontine Reticulospinal Tract

Back 57

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)

Front 58

Ruburospinal Tract

Back 58

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

Front 59

Lateral Corticospinal Tract

Back 59

Origin
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?”)

Front 60

Lateral Corticospinal Tract

Back 60

Majority decussate (85%) forming lateral corticospinal tract
Ventral (anterior) CST is uncrossed, ends in upper cord
Some monosynaptic to distal flexors

Front 61

Corticobulbar Fibers

Back 61

Pyramidal tract sends axons to many cranial nerve nuclei
Predominately crossed system but significant bilateral distribution

Front 62

Clinical Considerations: Lateral

Back 62

Weakness in distal flexors
Babinski sign
No spasticity
Loss of fractionation of movement
PT Syndrome quite different

Front 63

Clinical Considerations:
Medial

Back 63

Decrease in proximal muscle tone
Impaired locomotion
Manipulation of digits not impaired

Front 64

Primary Motor Cortex

Back 64

BRODMANN’S AREA 4
PRECENTRAL GYRUS
PARTIAL ORIGIN OF CORTICOSPINAL TRACT
RECEIVES ITS INPUT (ORDERS) FROM
Supplementary motor cortex
Premotor cortex
Prefrontal cortex
Basal ganglia
Cerebellum
Posterior parietal association cortex
SI cortex

Front 65

Premotor Cortex- Area 6

Back 65

Somatotopic - 2 areas (rostral, caudal)
Controls groups of muscles
“Plans” movements (fires before MI, 80 ms)

Front 66

Supplementary Motor Cortex

Back 66

Bilateral movement control
Somatotopic (may have multiple representations
Programming for “nonsymmetrical” bilateral movements
Mental rehearsal increases blood flow

Front 67

Parietal Lobe Contribution

Back 67

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!

Front 68

Upper Motor Neuron cause negative and positive signs
UMN->LMN-alpha motor

Back 68

WEAKNESS (PARESIS)
LOSS OF ABDOMINAL REFLEXES
BABINSKI SIGN
INCREASED STRETCH REFLEXES
INCREASED MUSCLE TONE
CLONUS
CLASP KNIFE REFLEX

Front 69

Distribution of Signs: Lower vs Upper Motor Neuron Disease
Weakness

Back 69

LMN +++ UMN ++

Front 70

Distribution of Signs: Lower vs Upper Motor Neuron Disease
Wasting

Back 70

LMN +++ UMN +/-

Front 71

Distribution of Signs: Lower vs Upper Motor Neuron Disease
Fasciculations

Back 71

LMN ++ UMN -

Front 72

Distribution of Signs: Lower vs Upper Motor Neuron Disease
DTR Reflexes

Back 72

LMN dec UMN inc

Front 73

Distribution of Signs: Lower vs Upper Motor Neuron Disease
Muscle Tone

Back 73

LMN dec UMN inc

Front 74

Distribution of Signs: Lower vs Upper Motor Neuron Disease
Clonus

Back 74

LMN - UMN ++

Front 75

Distribution of Signs: Lower vs Upper Motor Neuron Disease
Clasp-Knife Reflex

Back 75

LMN - UMN ++

Front 76

Cerebellum
Overall Functions:

Back 76

To monitor and make corrective adjustments to motor commands initiated elsewhere
Also participates in learning motor programs

Front 77

Cortex covers 3 pairs of deep nuclei

Back 77

Dentate N.
N. Interpositus
Fastigial N.

Front 78

The Vermis & Flocculondular lobe control

Back 78

Balance and Posture, work with the Vestibular

Front 79

Cerebrocerebellum -> Dentate Nucleus -> To motor and premotor corticies

Back 79

Motor Planning

Front 80

Intermediate Hemisphere -> Interposed Nuclei -> To lateral descending Systems

Back 80

Motor execution

Front 81

Vermis -> Fastigial nuclei -> To Medial descending systems

Back 81

Motor execution

Front 82

Vestibulo Cerebellum -> to vestibular nuclei

Back 82

Balance and eye movement

Front 83

Cerebeller Disorders

Back 83

Damage produces problems of
Synergy (asynergia)
Equilibrium
Tone
Intention tremor
Lateral damage affects distal muscles; medial damage affect trunk (somatotopic)
Effects are ipsilateral
No sensory deficits are produced

Front 84

Functions of the Basal Ganglia

Back 84

Movement
To initiate and regulate gross intentional movements of the body
To provide appropriate background muscle tone for intended movements
Scaling of movements
Cognition
Mood
Other non-motor behavior

Front 85

Movement Disorders of the Basal Ganglia

Back 85

General symptoms:
Change in muscle tone
Increase
Decrease
Hyperkinetic or hypokinetic disorders
Hyperkinetic: dyskinesias
Hypokinetic: bradykinesia

Front 86

Parkinson's Disease

Back 86

Due to loss of cells making dopamine in the substantia nigra (imbalance in excitation and inhibition in basal ganglia)
Characteristics: (both hypo and hyperkinetic)
Rigidity
Tremor at rest
Bradykinesia (akinesia)
Treatments
L-Dopa therapy; anticholinergic drugs, etc
Tissue transplant (fetal tissue; adrenal medulla cells)
Pallidotomy,
Deep brain stimulation, etc.

Front 87

Huntington's Chorea

Back 87

Due to loss of GABAergic and cholinergic neurons in striatum
Characteristics:
Autosomal dominant disorder
Decreased muscle tone
Choreiform movements (chorea: “dance”)
Dementia
Death

Front 88

Athetosis

Back 88

Due to loss of cells in cortex or caudate and putamen
Athetotic cerebral palsy
Characteristics:
Increased muscle tone
Athetoid movements

Front 89

Hemiballismus

Back 89

Due to damage of the subthalamic nucleus
Characteristics:
Decreased muscle tone
Ballistic movements
Usually gets better over time

Front 90

ANS

Back 90

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

Front 91

ANS Concepts

Back 91

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

Front 92

SNS

Back 92

Organized to mobilize the body for activity
Produces selective energy expenditure, catabolic functions and cardiopulmonary adjustments for intense activity
“Fight or Flight”

Front 93

PNS

Back 93

Organized for energy conservation
Reduces energy expenditure and increases energy stores
“Rest and Digest”

Front 94

Somatic VS Autonomic Intervention: Somatic

Back 94

One neuron
ACh

Front 95

Somatic VS Autonomic Intervention:Autonomic

Back 95

2 neuron chain
ACh at pre- to postganglionic synapse

Front 96

Somatic VS Autonomic Intervention:Postganglionic transmitters differ

Back 96

NE (sympathetic)
ACh (parasym.)

Front 97

Origin of Peripherial ANS: SNS

Back 97

Thoracolumbar
Paravertebral and prevertebral ganglia

Front 98

Origin of Peripherial ANS: PNS

Back 98

Craniosacral
III, VII, IX, X
S2, S3, S4
Ganglia near or in target tissue

Front 99

SNS

Back 99

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

Front 100

SNS Neurotransmitters

Back 100

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
Neuropeptides
Adrenal Medulla - Epinephrine and NE
Receptor heterogeneity - Alpha and Beta
a1, a2, b1, b2, b3

Front 101

Adrenal Medulla

Back 101

Preganglionic innervation of chromaffin cells
Act as “postganglionics”
Release epinephrine, norepinephrine
Travel via blood to target receptors (Hormone)
Contributes to sympathetic tone

Front 102

PNS

Back 102

Craniosacral division
CN III, VII, IX, X
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

Front 103

PNS Intervention

Back 103

Pre- to Postganglionic: nicotinic cholinergic
Postganglionic to target: muscarinic cholinergic

Front 104

Autonomic Pharm

Back 104

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