Reticular Formation and Control of Muscle Activity

Question 1

The RETICULAR FORMATION (RF) is a:

Answer 1

network or reticulum of many neurons that comprises the core of the neuroaxis.

Question 2

It is an __________________ old (early to develop) system that originally was thought to be diffusely organized.

Answer 2

ontegenetically

Question 3

Anatomical studies have shown that instead, the RF is composed of many well defined groups of neurons that receive _____________ from all ascending and descending systems and distribute their axons widely in ______________________ directions.

Answer 3

collaterals

caudal and rostral

Question 4

Consequently, all levels of the CNS are _____________________ either directly or indirectly by way of the reticular formation.

Answer 4

interconnected

Question 5

Nuclei in the reticular formation have a role in: regulating muscle tone for ____________________ during voluntary and reflexive movement; modulating the sense of __________, regulating ___________________________; and coordinating autonomic _________________ and _________________ function.

Answer 5

postural control

pain

arousal, sleep, and attention

respiratory

cardiac

Question 6

General organization: There are dozens of _____________ and _____________ of the RF. We will only deal with the general organization and a few specific nuclei.

Answer 6

nuclei and subdivisions

Question 7

1. ________________________ – largest division
2. _____________________– thin column of neurons along the midline of the brainstem
3. Miscellaneous nuclei – _____________________________________________

Answer 7

1. Central Division (Lateral and Medial Zone) – largest division
2. Raphe Nuclei (Midline Zone) – thin column of neurons along the midline of the brainstem
3. Miscellaneous nuclei – paramedian pontine RF (PPRF), pedunculopontine nucleus, locus ceruleus, ventral tegmental area.

Question 8

Central Division –

Answer 8

a continuous but diffuse column of neurons, begins as a continuation of the central gray interneuron network of the spinal cord (Lamina X) and ends in the midbrain.

Question 9

Central Division, consists of a __________ medial zone (____________) and a ________________ lateral zone (__________).

Answer 9

large (efferent)

smaller (afferent)

Question 10

Lateral zone – consists of neurons with _____________ dendrites that receive collateral input from _______ sensory and motor information carried by cranial nerves, spinal sensory pathways, and corticospinal, corticobulbar and corticopontine pathways.

Answer 10

large

ALL

Question 11

Sensory and ______________ inputs are integrated in the lateral zone. The lateral zone relays this integrated information to the _______________ zone. It also projects to the _____________________, _____________________, _____________________, and _____________________.

Answer 11

cortical

medial

cerebrum, cerebellum, thalamus (central median nucleus) and spinal cord.

Question 12

Medial zone –

Answer 12

gives rise to the major efferent pathways from the reticular formation.

Question 13

Vital function regulation – nuclei of the medial zone receive input from:

Answer 13

1) lateral zone
2) a variety of peripheral receptors, including the carotid body relayed through the solitary nucleus
3) hypothalamus, and
4) prefrontal cortex.

Question 14

Their (nuclei of the medial zone) role is to regulate vital cardiac and respiratory function through output to ___________________ sympathetic neurons in the ________________ horn of the _____________ spinal cord and preganglionic parasympathetic neurons associated with the _____________________ (cardiac), and to the spinal cord for ______________ control of motor neurons in the spinal cord that regulate _____________________.

Answer 14

preganglionic

lateral

thoracic

vagus nerve

somatic

inhalation and expiration

Question 15

Some patients with lesions to the brainstem that involve these regulatory centers have abnormal ________________________ or difficulty ________________________ with hypertension.

Answer 15

respiratory patterns

regulating blood pressure

Question 16

Additional reticular nuclei (of medial zone) regulate _______________ and _______________.

Answer 16

swallowing

vomiting

Question 17

Somatic motor activity regulation (of medial zone nuclei) – nuclei in the pons and medulla receive input from the cortex (corticoreticular pathway), cerebellum, vestibular nuclei, and somatosensory areas, via the ___________ zone.

Answer 17

lateral

Question 18

Their (nuclei of medial role_somatic motor activity regulation) role is to influence _________ motor neurons for the purpose of regulating __________________________________.

Answer 18

lower

postural, reflexive, and voluntary muscle control.

Question 19

Fibers (of medial zone nuclei in somatic motor regulation) descend in two separate pathways. Both pathways descend ___________________, but then can synapse on interneurons _____________________________. Thus, this influence can be seen ______________.

Answer 19

ipsilaterally

both ipsilaterally and contralaterally

bilaterally

Question 20

Medial (pontine) reticulospinal tract – part of the __________________ system, cell bodies originate in the ____________ RF, descend in ____________ funiculus as part of the MLF to end in the medial parts of the __________________, primarily at a cervical level.

Answer 20

medial activation

pontine

ventral funiculus

ventral horn

Question 21

What is the function of the medial (pontine) reticulospinal tract?

Answer 21

Function is to facilitate tonic facilitation of axial or postural flexors along with proximal joint muscles.

Question 22

Lateral (medulla) reticulospinal tract – part of the lateral activation system, cell bodies originate in the _______________________, descend in the ______________ funiculus to the lateral side of the ventral horn at all levels.

Answer 22

pontine (i think it is medulla..??) reticular formation

lateral funiculus

lateral side

Question 23

What is the function of the lateral (medulla) reticulospinal tract?

Answer 23

Function is to assist the lateral vestibulospinal pathway in tonically facilitating lower motor neurons of the extensors and inhibiting flexors.

Question 24

This tonic (of lateral RS tract) activity also influences the (y) motor neuron system to assist in the _____________________________.

Answer 24

sensitivity of stretch reflex activity.

Question 25

Raphe Nuclei (Midline Zone) – located in _______________ along the ___________ just anterior to the periaqueductal gray (central gray), many of the neurons use __________________ as their neurotransmitter.

Answer 25

brainstem midline serotonin (5-HT)

Question 26

The raphe nuclei receive input from a wide variety of ______________________________________areas. Output consists of ascending and descending pathways.

Answer 26

brainstem, cortical, cerebellar and spinal

Question 27

Ascending pathways (of raphe nuclei) – ___________________ neurons of the raphe play a major role in the reticular activating system that regulates ____________________________. Projection of the neuron pathways is throughout the _____________________________.

Answer 27

Serotonergic arousal, sleep, and mood cerebrum and brainstem

Question 28

Descending pathways (of raphe nuclei) – ________________ neurons modulate __________ input at the level of the “gate” in _________________ of the spinal gray.

Answer 28

Serotonergic pain dorsal horn

Question 29

Modulation of _______________________________ also occurs at the solitary nucleus and spinal trigeminal nucleus.

Answer 29

visceral (CN X) and facial (CN V) pain

Question 30

Input from the periaqueductal gray area that are receiving input from ___________________ pathways (part of the anterolateral system) are important in activating this system (descending pathway / pain)

Answer 30

spinoreticular

Question 31

The raphespinal pathway is a _____________________ tract that provides diffuse activation of ____________ neurons in the ____________ horn and may be involved in influencing motor output during levels of high ______________________.

Answer 31

nonspecific motor anterior motivation or arousal

Question 32

Raphespinal neurons in the ____________ horn influence the __________________ system.

Answer 32

lateral cardiovascular

Question 33

Paramedian pontine RF –

Answer 33

associated with cranial nerves of the extraocular eye muscles.

Question 34

The paramedian pontine RF is located at the level of the facial _____________, surrounding ______________. This was discussed in depth with cranial nerves III, IV, and VI.

Answer 34

facial colliculus surround abducens nucleus

Question 35

pedunculopontine nucleus –

Answer 35

an Acetylcholine (Ach) nucleus that is located in the caudal midbrain and projects to parts of the basal ganglia, vestibular nuclei and reticular spinal nuclei.

Question 36

The pedunculopontine nucleus is thought to have a role as a brainstem central pattern generator to induce __________ without __________control. It sends rhythmic impulses to ______________ and ______________ of the basal ganglia.

Answer 36

walking cerebral caudate and putamen

Question 37

Locus Ceruleus –

Answer 37

a major norepinephrine (NE) system that is located in the rostral pontine central gray region.

Question 38

Although the locus ceruleus receives only ____________ input from ________ brainstem nuclei, it sends ______________ ascending and descending connections.

Answer 38

restricted two widespread

Question 39

In regards to the locus ceruleus, ascending pathways to the thalamus, hypothalamus, basal forebrain and neocortex are involved in the ability to maintain and direct _____________.

Answer 39

attention.

Question 40

In regards to the locus ceruleus, the descending ______________ tract provides nonspecific activation of the ___________ neuron pool in the ________ horn, and modulation of _______ information in the _________ horn.

Answer 40

cerulospinal motor anterior horn pain dorsal

Question 41

Ventral Tegmental Area –

Answer 41

one of two dopamine (DA) projecting systems in the brainstem (the other is from substantia nigra).

Question 42

Fibers project from the VTA to ___________ and _____________ cortical areas and are believed to play a role in ___________ (decision making) and ______________.

Answer 42

limbic AND frontal cognition AND motivation

Question 43

The projections to the frontal lobe (from the VTA), are balanced with the ________________ pathways. Disturbances in these systems play a role in ____________ and other disorders of cognition and affect.

Answer 43

serotonergic depression

Question 44

The control of __________ activity, whether it is reflex activity, postural shifts, or voluntary movement activity, or some combination of all three, are based on the __________________________________________________.

Answer 44

muscle integrity of both the upper and lower motor neuron components

Question 45

Additionally, systems that modulate the activity of the upper motor neurons, such as _________________________ must be intact (for muscular/ reflex activity to occur)

Answer 45

cerebellum and basal ganglia

Question 46

Where are the cell bodies of the lateral corticospinal pathway located?

Answer 46

areas 8,6,4,3,1,2,5

Question 47

Where does the lateral cotricospinal pathway terminate?

Answer 47

lateral part of contralateral ventral horn; dorsal horn (from 3,1,2,5)

Question 48

The voluntary motor activity is of:

Answer 48

of proximal and distal limb musculature, fractionated (fine) motor activityW

Question 49

The fibers (of lateral corticospinal pathway) ending in the ____________ horn are involved in ______________ and _______________ of incoming sensory signals specific to ongoing motor activity.

Answer 49

dorsal horn feedback and modulation

Question 50

Where are the cell bodies of the Anterior (medial) corticospinal pathway located?

Answer 50

cell bodies in areas 4,6

Question 51

Where does the Anterior (medial) corticospinal pathway terminate?

Answer 51

in medial part of ipsilateral (but notes-contralateral??) ventral horn

Question 52

The voluntary activity of the anterior (medial) corticospinal pathway terminate is of:

Answer 52

of axial musculature

Question 53

Where are the cell bodies of the rubrospinal pathway located?

Answer 53

cell bodies in the Red Nucleus

Question 54

Where does the rubrospinal pathway terminate?

Answer 54

in lateral part of contralateral ventral horn, cervical region primarily

Question 55

The voluntary activity of the Rubrospinal pathway is:

Answer 55

voluntary (fractionated) activity of distal UE musculature, primarily flexors of the digits

Question 56

Where are the cell bodies of the Tectospinal pathway located?

Answer 56

cell bodies in superior colliculus

Question 57

Where does the tectospinal pathway terminate?

Answer 57

in the medial part of contralateral ventral horn, cervical region primarily

Question 58

The tectospinal pathway controls coordination of the:

Answer 58

neck movements with eye movements, reflexive turning toward stimulus

Question 59

Where are the cell bodies of the Lateral Vestibulospinal pathway located?

Answer 59

cell bodies primarily in Lateral Vestibular nucleus

Question 60

Where does the Lateral Vestibulospinal pathway terminate?

Answer 60

in ipsilateral ventral horns of all levels, but heavier in lower thoracic through sacral levels

Question 61

The lateral Vestibulospinal pathway is facilitory to:

Answer 61

extensor lower motor neurons as response to head movement

Question 62

Where are the cell bodies of the Medial Vestibulospinal pathway located?

Answer 62

cell bodies in Medial and Inferior vestibular nuclei

Question 63

Where does the Medial Vestibulospinal pathway terminate?

Answer 63

bilaterally in ventral horn of cervical and upper thoracic cord

Question 64

The Medial Vestibulospinal pathway is facilitory to:

Answer 64

to ipsilateral lower motor neurons of neck, inhibitory to contralateral lower motor neurons of neck, facilitory to extensors of upper extremities

Question 65

Where are the cell bodies of the Lateral (medullary) reticulospinal pathway located?

Answer 65

cell bodies in medullary reticular formation

Question 66

Where does the Lateral (medullary) reticulospinal pathway terminate?

Answer 66

in lateral part of ventral horn on interneurons effecting bilateral segmental LMNs

Question 67

The Lateral (medullary) reticulospinal pathway functions primarily to facilitate:

Answer 67

functions primarily to facilitate flexor LMNS and thus decrease the activity of extensor LMNs

Question 68

Where are the cell bodies of the Medial (pontine) reticulospinal pathway located?

Answer 68

cell bodies in pontine reticular formation

Question 69

Where does the Medial (pontine) reticulospinal pathway terminate?

Answer 69

terminate in medial part of ventral horn on interneurons effecting bilateral segmental LMNs, primarily in the cervical region

Question 70

The Medial (pontine) reticulospinal pathway functions to facilitate:

Answer 70

functions to facilitate extensors of the UE bilaterally

Question 71

The brainstem pathways function to help in maintaining static and reactive ___________ through ___________ input, through ascending sensory information that is entering the _________________, or through cerebellar influences via the red nucleus, vestibular nuclei, and reticular formation.

Answer 71

posture vestibular reticular formation

Question 72

This influence is mediated by activity on both the _______ motor neuron and ______ motor neurons, mostly through _______________ connections

Answer 72

α γ interneuronal

Question 73

Voluntary motor activity is dependent on the _________.

Answer 73

cortex

Question 74

The main pathway for necessary to generate volitional movement is via the ________________________ tract, which is receiving information from _______________________________________ and _______________________________________under the modulatory influence of cerebellum and basal ganglia.

Answer 74

lateral corticospina area 6 (premotor and supplementary motor cortical regions) AND area 4 (primary motor cortex)

Question 75

Running parallel to this pathway is the __________________________ pathway (area 6 to pontine and medullary reticular nuclei).

Answer 75

corticoreticulospinal

Question 76

Thus, area 6 is serving three functions:

Answer 76

1. direct corticospinal fibers, 2. direct input to are 4, and 3. indirect corticoreticulospinal fibers.

Question 77

Anticipatory postural responses (preparatory postural responses prior to voluntary limb movements) are prepared through the __________________ projections from the __________________ motor cortex. Influence from these cortical regions onto the _________________ pathways is important for regulating the __________________ of these pathways.

Answer 77

corticospinal supplementary reticulospinal excitability

Question 78

______________ and ______________ Posture as an example of changes in descending control over motor activity

Answer 78

Decerebrate Decorticate

Question 79

Decerebrate posture –

Answer 79

when brainstem pathways are disconnected from the cortex by a midbrain lesion caudal to the red nucleus.

Question 80

In decerebrate posture, lateral vestibulospinal tract maintains tonic activity over _____________ of the __________________ extremities.

Answer 80

extensors upper and lower

Question 81

In decerebrate posture, reticulospinal tracts are ____________ of influence from cortex due to lesion. This lets the vestibulospinal pathways maintain their activity without ________________ activity of the reticulospinal paths. ___________ influence from rubrospinal tract is also lost. The resultant posture is ____________________________________.

Answer 81

devoid antagonistic Flexor extension of both the upper and lower extremities.

Question 82

Decorticate posture –

Answer 82

when lesion is above the level of the red nucleus, rubrospinal influence on UE flexors causes flexor posture in UE, while extensor tone is still dominant in LE.

Question 83

The resultant of decorticate posture is:

Answer 83

flexion at the elbow in UE with extension of the LE.