Reticular Formation and Control of Muscle Activity Flashcards
The RETICULAR FORMATION (RF) is a:
network or reticulum of many neurons that comprises the core of the neuroaxis.
It is an __________________ old (early to develop) system that originally was thought to be diffusely organized.
ontegenetically
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.
collaterals
caudal and rostral
Consequently, all levels of the CNS are _____________________ either directly or indirectly by way of the reticular formation.
interconnected
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.
postural control
pain
arousal, sleep, and attention
respiratory
cardiac
General organization: There are dozens of _____________ and _____________ of the RF. We will only deal with the general organization and a few specific nuclei.
nuclei and subdivisions
- ________________________ – largest division
- _____________________– thin column of neurons along the midline of the brainstem
- Miscellaneous nuclei – _____________________________________________
- Central Division (Lateral and Medial Zone) – largest division
- Raphe Nuclei (Midline Zone) – thin column of neurons along the midline of the brainstem
- Miscellaneous nuclei – paramedian pontine RF (PPRF), pedunculopontine nucleus, locus ceruleus, ventral tegmental area.
Central Division –
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.
Central Division, consists of a __________ medial zone (____________) and a ________________ lateral zone (__________).
large (efferent)
smaller (afferent)
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.
large
ALL
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 _____________________.
cortical
medial
cerebrum, cerebellum, thalamus (central median nucleus) and spinal cord.
Medial zone –
gives rise to the major efferent pathways from the reticular formation.
Vital function regulation – nuclei of the medial zone receive input from:
1) lateral zone
2) a variety of peripheral receptors, including the carotid body relayed through the solitary nucleus
3) hypothalamus, and
4) prefrontal cortex.
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 _____________________.
preganglionic
lateral
thoracic
vagus nerve
somatic
inhalation and expiration
Some patients with lesions to the brainstem that involve these regulatory centers have abnormal ________________________ or difficulty ________________________ with hypertension.
respiratory patterns
regulating blood pressure
Additional reticular nuclei (of medial zone) regulate _______________ and _______________.
swallowing
vomiting
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.
lateral
Their (nuclei of medial role_somatic motor activity regulation) role is to influence _________ motor neurons for the purpose of regulating __________________________________.
lower
postural, reflexive, and voluntary muscle control.
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 ______________.
ipsilaterally
both ipsilaterally and contralaterally
bilaterally
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.
medial activation
pontine
ventral funiculus
ventral horn
What is the function of the medial (pontine) reticulospinal tract?
Function is to facilitate tonic facilitation of axial or postural flexors along with proximal joint muscles.
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.
pontine (i think it is medulla..??) reticular formation
lateral funiculus
lateral side
What is the function of the lateral (medulla) reticulospinal tract?
Function is to assist the lateral vestibulospinal pathway in tonically facilitating lower motor neurons of the extensors and inhibiting flexors.
This tonic (of lateral RS tract) activity also influences the (y) motor neuron system to assist in the _____________________________.
sensitivity of stretch reflex activity.
Raphe Nuclei (Midline Zone) – located in _______________ along the ___________ just anterior to the periaqueductal gray (central gray), many of the neurons use __________________ as their neurotransmitter.
brainstem
midline
serotonin (5-HT)
The raphe nuclei receive input from a wide variety of ______________________________________areas. Output consists of ascending and descending pathways.
brainstem, cortical, cerebellar and spinal
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 _____________________________.
Serotonergic
arousal, sleep, and mood
cerebrum and brainstem
Descending pathways (of raphe nuclei) – ________________ neurons modulate __________ input at the level of the “gate” in _________________ of the spinal gray.
Serotonergic
pain
dorsal horn
Modulation of _______________________________ also occurs at the solitary nucleus and spinal trigeminal nucleus.
visceral (CN X) and facial (CN V) pain
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)
spinoreticular
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 ______________________.
nonspecific
motor
anterior
motivation or arousal
Raphespinal neurons in the ____________ horn influence the __________________ system.
lateral
cardiovascular
Paramedian pontine RF –
associated with cranial nerves of the extraocular eye muscles.
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.
facial colliculus
surround abducens nucleus
pedunculopontine nucleus –
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.
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.
walking
cerebral
caudate and putamen
Locus Ceruleus –
a major norepinephrine (NE) system that is located in the rostral pontine central gray region.
Although the locus ceruleus receives only ____________ input from ________ brainstem nuclei, it sends ______________ ascending and descending connections.
restricted
two
widespread
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 _____________.
attention.
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.
cerulospinal
motor
anterior horn
pain
dorsal
Ventral Tegmental Area –
one of two dopamine (DA) projecting systems in the brainstem (the other is from substantia nigra).
Fibers project from the VTA to ___________ and _____________ cortical areas and are believed to play a role in ___________ (decision making) and ______________.
limbic AND frontal
cognition AND motivation
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.
serotonergic
depression
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 __________________________________________________.
muscle
integrity of both the upper and lower motor neuron components
Additionally, systems that modulate the activity of the upper motor neurons, such as _________________________ must be intact (for muscular/ reflex activity to occur)
cerebellum and basal ganglia
Where are the cell bodies of the lateral corticospinal pathway located?
areas 8,6,4,3,1,2,5
Where does the lateral cotricospinal pathway terminate?
lateral part of contralateral ventral horn; dorsal horn (from 3,1,2,5)
The voluntary motor activity is of:
of proximal and distal limb musculature, fractionated (fine) motor activityW
The fibers (of lateral corticospinal pathway) ending in the ____________ horn are involved in ______________ and _______________ of incoming sensory signals specific to ongoing motor activity.
dorsal horn
feedback and modulation
Where are the cell bodies of the Anterior (medial) corticospinal pathway located?
cell bodies in areas 4,6
Where does the Anterior (medial) corticospinal pathway terminate?
in medial part of ipsilateral (but notes-contralateral??) ventral horn
The voluntary activity of the anterior (medial) corticospinal pathway terminate is of:
of axial musculature
Where are the cell bodies of the rubrospinal pathway located?
cell bodies in the Red Nucleus
Where does the rubrospinal pathway terminate?
in lateral part of contralateral ventral horn, cervical region primarily
The voluntary activity of the Rubrospinal pathway is:
voluntary (fractionated) activity of distal UE musculature, primarily flexors of the digits
Where are the cell bodies of the Tectospinal pathway located?
cell bodies in superior colliculus
Where does the tectospinal pathway terminate?
in the medial part of contralateral ventral horn, cervical region primarily
The tectospinal pathway controls coordination of the:
neck movements with eye movements, reflexive turning toward stimulus
Where are the cell bodies of the Lateral Vestibulospinal pathway located?
cell bodies primarily in Lateral Vestibular nucleus
Where does the Lateral Vestibulospinal pathway terminate?
in ipsilateral ventral horns of all levels, but heavier in lower thoracic through sacral levels
The lateral Vestibulospinal pathway is facilitory to:
extensor lower motor neurons as response to head movement
Where are the cell bodies of the Medial Vestibulospinal pathway located?
cell bodies in Medial and Inferior vestibular nuclei
Where does the Medial Vestibulospinal pathway terminate?
bilaterally in ventral horn of cervical and upper thoracic cord
The Medial Vestibulospinal pathway is facilitory to:
to ipsilateral lower motor neurons of neck, inhibitory to contralateral lower motor neurons of neck, facilitory to extensors of upper extremities
Where are the cell bodies of the Lateral (medullary) reticulospinal pathway located?
cell bodies in medullary reticular formation
Where does the Lateral (medullary) reticulospinal pathway terminate?
in lateral part of ventral horn on interneurons effecting bilateral segmental LMNs
The Lateral (medullary) reticulospinal pathway functions primarily to facilitate:
functions primarily to facilitate flexor LMNS and thus decrease the activity of extensor LMNs
Where are the cell bodies of the Medial (pontine) reticulospinal pathway located?
cell bodies in pontine reticular formation
Where does the Medial (pontine) reticulospinal pathway terminate?
terminate in medial part of ventral horn on interneurons effecting bilateral segmental LMNs, primarily in the cervical region
The Medial (pontine) reticulospinal pathway functions to facilitate:
functions to facilitate extensors of the UE bilaterally
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.
posture
vestibular
reticular formation
This influence is mediated by activity on both the _______ motor neuron and ______ motor neurons, mostly through _______________ connections
α
γ
interneuronal
Voluntary motor activity is dependent on the _________.
cortex
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.
lateral corticospina
area 6 (premotor and supplementary motor cortical regions) AND area 4 (primary motor cortex)
Running parallel to this pathway is the __________________________ pathway (area 6 to pontine and medullary reticular nuclei).
corticoreticulospinal
Thus, area 6 is serving three functions:
- direct corticospinal fibers, 2. direct input to are 4, and
- indirect corticoreticulospinal fibers.
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.
corticospinal
supplementary
reticulospinal
excitability
______________ and ______________ Posture as an example of changes in descending control over motor activity
Decerebrate
Decorticate
Decerebrate posture –
when brainstem pathways are disconnected from the cortex by a midbrain lesion caudal to the red nucleus.
In decerebrate posture, lateral vestibulospinal tract maintains tonic activity over _____________ of the __________________ extremities.
extensors
upper and lower
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 ____________________________________.
devoid
antagonistic
Flexor
extension of both the upper and lower extremities.
Decorticate posture –
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.
The resultant of decorticate posture is:
flexion at the elbow in UE with extension of the LE.
