(13) Posture and Movement

Question 1

(Introduction)

In veterinary neurology, abnormalities of posture and movement are more important than sensory disorders because animals readily express motor behavior but hardly at all report their feelings HAHAHAH

Question 2

(Preview: Posture/Movement Hierarchy)

(Spinal Cord and Cranial Nerve Motor Nuclei)

1. useful response to a stimulus (determined by local interneroun circuits)

(Hindbrain)

2. excitation of alpha and gamma motor units of extensor muscles (driven by spontaneous activity of reticular formation and vestibular neurons)
3. maintaining normal position of eyes, head, and body (vestibular system)

Answer 2

1. local reflex
2. standing posture
3. equilibrium

Question 3

(Preview: Posture/Movement Hierarchy cont)

(midbrain)

1. orienting head/eyes/ears toward abrupt visual/auditory stimuli (tectum)
2. moving individual joints (via red nucleus and rubrospinal tract)

(Forebrain)

3. species-specific patterns of reaction/posture/movement/gait (circuits involving basal nuclei, thalamus, and motor areas of cerebral cortex)
4. including learned movement sequences performed too rapidly for sesory feedback (involves patter generator neurons in premotor cortex)

Answer 3

1. orientation
2. specific movements
3. inherent movement sequences
4. learned movements

Question 4

(Brain Structures Concerned with Posture and Movement)

(HINDBRAIN)

(A. Reticular Formation)

1. Anatomy: mixture of what? found throughout what? gets synaptic input from what?

Answer 4

1. gray and white matter; midbrain and hindbrain; collateral branches of ascending tracts (spinothalamic tracts)

Question 5

(HINDBRAIN)

(Reticular Formation cont)

1-3. Physiology: spontaneous active neuronal circuits: perform several functions, including (3 things)

(standing posture and muscle tone via two pathways to alpha and gamma neurons)

(these are those two pahtways)

4. Arises from neurons located laterally in pons and medulla (name it). Is it dominant and spontaneously active? activates what neurons to extensor muscles of what?
5. Arises from neurons located medially in medulla (name it). Inhibits what and activates what? Is it spontaneuoulsy active? driven by what to present movement posture?

Answer 5

1. ascending system to alert cerebral cortex (via non-specific thalamic nuclei) vs. coma
2. vegetative centers: regulate heart rate, respiration, digestive tract, micturition, etc
3. standing posture and muscle tone via two pathways to alpha and gamma neurons
4. pontine reticulospinal tract; yes; alpha and gamma neurons to extensor muscles of proximal joints
5. medullary reticulospinal tract; inhibits neurons to extensor muscles and excites neurons to flexor muscles; no; cerebral cortex

Question 6

(HINDBRAIN)

1. What are the two descending tracts of the Vestibular Nuclei?
2. Which one drives standing posture? controls neck muscles?

*Vestibular nuclei also utilize the two reticulospinal tracts to adjust muscle tone

Answer 6

1. lateral vestibulospinal tract and medial vestibulspinal tract (mlf)
2. lateral; medial

Question 7

(MIDBRAIN)

(Red Nucleus)

1. Large neurons of the red nucleus gives rise to the what tract? the principal desceding tract for what in domestic animals?
2. the red nucleus is merely a collection of what? What synpase on large projection neurons in the red nucleus and control their activity?
3. The rubrospinal tract dessucates in what and descends in the what?
4. Rubrospinal fibers synapse on what and produce independent movements of shoulder/hip and elbow/stifle; carpus/hock? move digits?

Answer 7

1. rubrospinal tract; voluntary movement
2. projection neurons; asons from the motor area of the cerebral cortex
3. midbrain; dorsal half of the lateral funiculus
4. spinal interneurons; no

Question 8

(MIDBRAIN)

(Tectum)

1. Rostral and Caudal Colliculi are refex centers which do what?
2. Neurons in an interemediate layer of the rostral colliculus are sandwiched bewteen what layers?

3-4. Neurons in an interemediate layer of the rostral colliculus Give rise to what two tracts?

5. Using horizontal and vertical gaze centers in the reticular formation, the tectum rapidly shifts the eyes to focus on what?

Answer 8

1. orient head, eyes, and ears toward sudden visual and auditory stimuli
2. visual and somatic sensory layers
3. tectospinal fibers - descend to the cervical spinal cord (for head turning)
4. tectobulbar fibers - to cranial nerve nuclei that control ear and eye movement
5. novel stimuli (saccadic movement)

Question 9

1. What is quick eye movement used to shift focus to new visual features?
2. What occurs during the stops following saccades?

Answer 9

1. saccade
2. visual perception

Question 10

REad the sections on substantia nigra and subthalamus…. bottom of 103 and top of 104 (it’s little text)

Question 11

(FOREBRAIN)

(Basal Nuclei - Basal Ganglia)

1. Anatomically, the term “basal nuclei” refers to what?

2-3. What are the two ways that the nuclei may be grouped?

4. Physiologically, what five nuclei play a motor role (participating in circuits that involve what??

Answer 11

1. non-cortical gray matter of telencephalon
2. Striatum = accumbens, caudate, and putamen; named for internal capsule gray matter striations
3. lentiform nucleus = putamen and globus pallidus, together they have the shape of a lens
4. accumbens, caudate, putamen, globus pallidus, and endopeduncular nuclei (thalamus and cerebral cortex)

Question 12

(Forebrain - Basal Nuclei Cont)

1. Basal Nuclei suppress what?
2. They regulate the selection, onset, and cessation of “voluntary” movement by participating in what circuits involving what areas of cerebral cortex?
3. The motor cortex executes actual movements via what descending tracts? Do basal nuclei themselves give rise to descending tracts?

Answer 12

1. unwanted movements
2. thalamocortical circuits involving motor-related areas of cerebral cortex
3. pyramidal or extrapyramidal descending tracts; no

Question 13

(Basal Nuclei cont)

1. Note: Voluntary movement is initiated by regions of cerebral cortex responsible for what and what (+ location)?
2. Do initiating areas of cerebral cortex communicate their movement needs directly to the motor-related cortex? What do they do instead? These forebrain circuits are the mechanisms for selection/execution of what and the supression of what?

Answer 13

1. emotionally driven behavior (limbic cortex) or goal driven decisions (assocation cortex)
2. no; communicate via circuits involving basal nuclei and thalamus; desired movements; unwanted movements

Question 14

(Basal Nuclei)

(Two categories of voluntary movement circuits)

1. the one involving the caudate nucleus is active in what? particularly during what?
2. The other, involving the putamen controls what? particularly in the case of what?

Answer 14

1. selecting and assembling movements, particularly during learning
2. amplitudes and durations of movements ; particularly in the case of habitually performed movements that can be performed with minimal thinking

Question 15

(Basal Nuclei)

1. All projections from basal nuclei are excitatory or inhibitory?
2. The output basal nuclei (name them) are tonically active in what?
3. The input basal nuclei (name them) require what?
4. So to activate desired movements the input nuclei do what to the output nuclei?

Answer 15

1. inhibitory
2. globus pallidus and endopeduncular nucleus; suppressing movement
3. accumbens, caudate, and puntamen; require excitatory input from the cerebral cortex
4. disinhibit them!!!! oMG

Question 16

(Basal Nuclei)

1. Particularly in primates, damage to basal nuclei impairs either what or what? (give fancy names too)
2. In domestic mammals, lesions of the basal nuclei produce what three things?

Answer 16

1. movement onset (hypokinetic syndromes) or movement cessation (hyperkinetic syndromes)
2. circling toward the damaged side, pacing, and muscle hypertonia

Question 17

LOOK AT FIGURE ON 105 ALOT!!!!

Question 18

(Cerebral Cortex - motor-related areas)

1. The motor area of the cerebral cortex executes what? The other motor-related areas of cortex are involved in what other voluntary movements?

Answer 18

1. practiced voluntary movements; planning/learning/selecting

Question 19

(Cerebral - motor related areas)

(motor area)

1. located around what?
2. Main source of how many descedning pathway systems? what are they?
3. Each output neuron from the motor cortex innervates what?

4. The cerebral cortex is organized to control what not what?

Answer 19

1. cruciate sulcus
2. two; direct pyramidal and indirect extrapyramidal
3. multiple motor nuclei

4. movement not muscles

Question 20

(Cerebral cortex - motor-related areas)

(premotor area)

1. collection of what regions that project to what area?
2. Involved in doing what two things?

(supplementary motor area)

3. What is represented in this specialized premotor cortex located medially? It is active when thinking about what?

Answer 20

1. cortical regions that project to motor area
2. assembling complex movements and generating learned, rapid-sequence movements (pattern generator circuits)
3. the entire body; proposed movements

Question 21

(III. Voluntary Movement)

1. Voluntary movements originate in the forebrain from circuits involving what three things?
2. The forebrain circuits select and execute movements decided by what in response to what?

Answer 21

1. basal nuclei, thalamus, and motor areas of the cerebral cortex
2. assocation cortex in response to stimuli and emotional drive

Question 22

What are the four steps of the Voluntary Movement Process? (plus what region is associated with each)

Answer 22

1. External Cue/ Internal Urge (sensory cortex/ limbic system)
2. decision (assocation neocortex)
3. selection (what) (premotor and caudate)
4. execution (how) (motor area and putamen)

* limbic and accumbens assocaiated with 3 and 4

Question 23

(Descending Pathways for volunatry movement)

1. Fall into how many categories?
2. What one is a direct connection from motor and premotor areas of cerebral cortex to motor unit efferent neurons, generally via what? Axons travel in the pyramids of the what?
3. What does this tract controls particularly what? It is especially concerned with what?
4. Most pyramidal tract (85% in human) decussate where and from what which terminates where?
5. What do remaining axons form? Cross at the level what? innervates what?

Answer 23

1. two
2. pyramidal tract; via local interneurons; medulla oblongata
3. musculature of teh manus and pes; precise movements of individual digits (also lips and tongue)
4. decussate at medullary-spinal juction; form the lateral corticospinal tract; terminates in lateral motor nuclei of ventral horn enlargements (limb muscles)
5. the ventral corticospinal tract; crosses at level of termination in the spinal cord; innervates medial motor nuclei (postural muscles).

Question 24

(Descending Pathways for voluntary movement)

1. The term applied to non-pyramidal voluntary movement tracts?
2. Under the direction of cerebral cortex (motor areas), these tracts control what? generating what? Is this system most imporant in domestic animals, naturally?
3. What are the principal extrapyramidal tracts (3 of them)?

Answer 24

1. extrapyramidal tracts
2. control trunk and proximal limb musculature (vs. manus/pes); generating coarse components of posture/movement/locomotion; it naturally is
3. rubrospinal tract, pontine reticulospinal tract, and medullary reticulospinal tract

Question 25

1. Do voluntary movements engage multiple descending tracts?

A specific voluntary movement (a feline paw swipe) would involve rubrospinal and pyramidal tracts and require associated postural adjustments involving reticulospinal tracts

Answer 25

1. yes!

Question 26

(Veterinary Clinical Considerations)

(UPPER MOTOR NEURO DAMAGE)

in order of mild to severe deficits

NAME WHAT IS LOST

1: paresis (partial paralysis or weakness) of manus & pes; inability to move digits and lips independently & rapidly; deficient tactile placing (also evident by not clearing curbs & steps); clinical hopping deficits.
2: disappearance of learned movement skills; spastic paralysis (absence of voluntary movement capability, plus hypertonic limb extension due to release of pontine reticular formation suppression).
3: persistent standing posture but may exhibit phasic actions (sitting, stepping, etc.) if prodded to do so; capable of righting reactions to restore standing posture.
4: limbs rigidly extended constantly in a “saw-horse” attitude (decerebrate rigidity); no locomotion or righting capability; tonic neck reflexes present (postural adjustments initiated by neck proprioceptors).
5: temporary areflexia may be evident with abrupt injury (spinal shock); paralysis without spasticity; local spinal reflexes intact; crossed extension accompanies the withdrawal reflex.

Answer 26

1. Loss of only pyramidal tract
2. Loss of motor cortex
3. Loss of whole forebrain (= midbrain animal)
4. Loss of forebrain & midbrain (= hindbrain animal)
5. Loss of whole brain (= spinal animal)

Question 27

(Lower Motor Neuron Damage)

What occurs in spinal cord or peripheral nerve damage?

Answer 27

paralysis and areflexia (flaccid paralysis); severe atrophy (denervation) atrophy of skeletal muscles over weeks

Question 28

LOOK AT PG 108 a whole bunch!