CNS Part 2 Flashcards
midbrain contains (3)
centers for motor control
nuclei of the reticular formation
periqueductal gray region (PAG)
Midbrain:
Centers for motor control (3)
A. Substantia Nigra
B. Red Nucleus
C. Superior and Inferior Colliculi
The --- --- rises from the superior and inferior colliculi of the midbrain. It causes head turning in response to sudden visual or auditory stimuli.
tectospinal tract
“Morphine and endogenous opioid peptides also act in the midbrain Periaqueductal Gray (PAG) to induce
analgesia
The PAG is a part of a descending pathway that modulates
pain transmission by inhibition of
primary afferent transmission in the dorsal horn
These
PAG neurons activate neurons in the (2) that project to the spinal cord where they release serotonin and norepinephrine,
respectively, to inhibit the activity of dorsal horn neurons that receive input from nociceptive
afferent fibers
Nucleus Raphe Magnus and Rostral Ventromedial
Medulla
Pons (4)
- Pneumotaxic Center
- Nuclei of the Reticular Formation
- Pontine Reticular and Vestibular Nuclei for motor control.
- Swallowing Center (along with the Medulla Oblongata).
Pneumotaxic Center regulates centers in the —. Activation limits
— — and increases — —
Medulla
inspiration time
respiration rate
Cerebellum is Involved in (3)
motor control of
posture, muscle tone and
learning of repeated motor
functions
Diseases of the cerebellum result in (3)
alterations in gait, balance
and coordination of motor
activities; not paralysis.
the most inferior portion of brainstem
and is continuous with the spinal cord
medulla oblongata
medulla oblongata includes (5)
1. Autonomic control centers (Cardiovascular, Respiratory, Swallowing, Vomiting, etc.) 2. Nucleus Raphe Magnus (Serotonin) and Rostral Ventromedial Medulla (Norephinephrine) that release NT onto dorsal horn neurons to reduce ascending pain signals. 3. Medullary Reticular Nuclei (motor) 4. Pyramids (motor axons of the Corticospinal Tract) 5. Nuclei for the Reticular Formation
Nerve signals in the brainstem activate the cerebrum by activating
Neurohormonal Systems
Neurohormonal Systems release specific
facilitatory or inhibitory
substances into selected areas of the brain
Reticular excitatory activating
system (RAS) in the brainstem
activates the cortex via the
thalamus
– Pain signals increase the activity of the
excitatory area.
– ACH is one of the NT
Consciousness is maintained by the normal
functioning of the — above the mid pons and its
bilateral projections to the thalamus and cerebral
hemispheres.
RAS
Reticular inhibitory system
inhibits the activity of the
reticular
excitatory area.
– Serotonin is one of the NT for this system.
Coma results from lesions that affect either the
RAS or both cerebral hemispheres.
Barbiturates (ex. Thiopental) depress the RAS in
the brainstem, which controls
consciousness
— is involved in cognitive
functions, especially memory
Acetylcholine
— — accounts for
the majority of dementia cases. Its
incidence increases with age
Alzheimer’s Disease
Alzheimers is due to
neuronal accumulation of
abnormal proteins (A-Beta Amyloid
and tau -a microtubule associated
protein) and Neurofibrillary Tangles.
Areas most severely impacted by AD are
the (2)
hippocampus and temporal lobes.
AD causes degeneration of cholinergic
neurons in the — that project throughout the
cortex.
Nucleus Basalis of Meynert
Treatment for Alzheimer’s Disease
includes
Acetylcholinesterase Inhibitors
and NMDA (Glutamate receptor)
antagonist.
skipped
Serotonin influences a multitude of functions, including (10)
sleep, cognition, sensory
perception, motor activity, temperature regulation, nociception, mood, appetite,
sexual behavior, and hormone secretion
It has been hypothesized that every
neuron in the brain may be in synaptic
contact with a
serotonin neuron
— — are located in the
Midbrain, pons, and medulla
Raphe nuclei (ex. Nucleus Raphe Dorsalis), Pons (ex. Nucleus Raphe Pontis) and Medulla Oblongata (ex. Nucleus Raphe Magnus).
Nucleus Raphe Magnus is
involved in
dampening
ascending pain (nociceptive)
signals
The physiological processes under
dopaminergic control include (5)
reward, emotion, cognition, memory, and motor activity.
Neurons in the Substantia
Nigra Compacta project to
the Basal Nuclei; this is the
pathway that degenerates in
Parkinson’s Disease
Neurons in the – —- — project to
the Nucleus Accumbens
and the Prefrontal Cortex
Ventral
Tegmental Area
Neurons in the Ventral Tegmental Area project to the Nucleus Accumbens and the Prefrontal Cortex. Dysfunction in this pathway is associated with (4)
addiction, schizophrenia and psychoses (bipolar depression) and learning deficits.
Norepinephrine impacts all areas of the brain and facilitates excitatory
synaptic transmission leading to (2)
attention and arousal
“The monoamine hypothesis of depression suggests that depression is related to a deficiency in the amount or function of cortical and limbic (3)
serotonin (5-HT), norepinephrine
(NE), and dopamine (DA). “
All classes of antidepressants appear to enhance the synaptic availability of (3)
5-HT,
norepinephrine, or dopamine
Most voluntary movements
‘initiated’ by the cerebral cortex
are achieved when the cortex
activates ‘patterns’ of
function
stored in lower brain areas –
the brainstem, basal ganglia
and cerebellum.
The motor system learns by
doing and performance
improves with repetition.
Involves
Long-Term
Potentiation
Pyramidal/Direct
Pathway
UMNs from the cerebral cortex initiate and direct sequences of voluntary movement
Extrapyramidal/
Indirect
Pathways
UMNs originate in motor centers in the brainstem and direct subconscious muscle tone, posture, balance and orientation of the head and body
Damage to UMN causes --- --- on muscles on the --- side of the body. This results in (3)
spastic paralysis opposite increased muscle tone, exaggeration of reflexes and pathological reflexes such as the Babinski Reflex
Damage to the LMN causes --- --- of muscles on the --- side of the body. There is neither voluntary nor reflex action of the muscle fibers and tone is decreased
flaccid paralysis
same
The LMN is cholinergic and releases
– that binds to nicotinic receptors
on skeletal muscle.
ACH
The motor cortex has three regions:
(1) Premotor Area/Cortex
(2) Supplementary Motor Area/Cortex
(3) Primary Motor Area/Cortex
The — — sets posture (ex.
position shoulder and arm) at the start of
planned movement .
Premotor cortex
The Premotor area
determines the overall
motor plan
The — — — activates
specific muscles to execute the plan
Primary motor cortex (UMN)
More than half of the Primary Motor Cortex is devoted to
controlling the muscle of the (2)
hands and muscles of speech
The — — — is
involved in organizing or planning motor
sequences
supplementary motor cortex
The supplementary motor cortex is
involved in organizing or planning motor
sequences. Lesions of this area produce (2)
awkwardness in performing complex activities
and difficulty with bimanual coordination
Axons from neurons in the Supplementary and Primary Motor
Cortex make up the
Corticospinal (Lateral and Ventral) and
Corticospinal (Pyramidal) Tract
• Called the
Direct Motor Pathway
Corticospinal (Pyramidal) Tract
• Fibers originate in the — — and the fibers descend through the
Motor Cortex
internal capsule of the cerebrum
Corticospinal (Pyramidal) Tract
• In the Medulla Oblongata, these axons form
bundles known as the
pyramids
90% of the axons decussate to the contralateral side in
the medulla oblongata. These axons form the
Lateral
Corticospinal Tract of the spinal cord.
• DISTAL MUSCLES
The 10% that do not decussate in the medulla and
these axons from the
Anterior Corticospinal Tract.
These fibers decussate in the spinal cord before
synapsing with the LMN.
• PROXIMAL MUSCLES
Both synapse with the LMN in the
Dorsal Horn
of the spinal cord
Corticobulbar Tract
• Fibers originate in the — — and
terminate on
motor cortex
nuclei in the brainstem
Corticobulbar Tract
• The following cranial nerves receive
input from the corticobulbar tract:
– Oculomotor (CN III), Trochlear (CN IV), Trigeminal (CN V), Abducens (CN VI), Facial (CN VII), Glossopharyngeal (IX), Accessory (CN XI), Vagus (X), Hypoglossal (CN XII)
Corticobulbar Tract
• Innervate LMN that control
conscious
control over skeletal muscles that move
the eye, jaw, face and some muscles of
the neck and pharynx.
