Lecture 1: Introduction to Central & Peripheral Nervous System Disorders Flashcards
KNOW: Excessive glutamate (neurotransmitter) can result in cell death
Where can axons regenerate in the PNS or the CNS?
PNS
This is why neuroplasticity is so important
She wants to go over this stuff
What does ligand gated mean?
* Is this a gated channel
bdining of a substance (like a neurotransmitter) opens the channel.
This would be considered a gated channel
KNOW: A closed channel would be something like a leak channel. Its not gaited
What opens a voltage gated channel?
electrical potanetial
What opens a mechanical gated channel?
Some kind of modality. Think stretching it etc…
Neural anatomy
This picture is talking about what happens w/ a local action potantial
Some deformation of receptor happens
This may trigger a local potential
Then eventually the AP travels down the membrane (remember this is all or none and is a summation of the local potentials, and as soon as the minimum amount needed triggers it its all or none)
What is the CNS defined as?
* What are its 3 regions?
All structures encased in bone
Regions:
1) Spinal Cord
2) Brainstem & cerebellum
3) Cerebral regions
What is the PNS defined as?
* Does it include crainal nerve axons?
PNS = all structures NOT encased in bone (bone = verebtral column and skull)
Includes crainal nerve axons
What are our 3 vertical systems that have axons that extend trhough all regions (CNS and PNS) of the NS?
* Picture someone from head to toe and hose systems are everywhere
1) Somatosensory
2) Somatic (motor)
3) Autonomic
What is the order of the brainstem from superior –> inferior (rostural –> caudal)
Midbrain –> Pons –> Medulla
What is responsible for controlling bodily functions?
CNS
What is the center for behavioral and intellectual abilities?
CNS
Neurons where are organized into highly complex patterns that mediate information through synaptic interactions?
CNS
Outer most area of gray matter in the brain
Cerebral Cortex
* note it is part of the cerebrum
Highest order of conscious function and integration in CNS is what prt of the cerebrum?
Cerebral Cortex
Makes sense - vegetaive fucntion is innermost
Where is the primary motor corex located?
Pre central gyrus
Where is the primary somatosensory cortex?
Post central gyrus
Most CNS therapeutic medications tend to affect WHAT function indirectly by first altering the function of lower brain and SC structures?
* What is the exception?
affect cortical function
Exception = antiepileptic drugs where the cerebral cortex is targeted directly
Lots of medications affect cortical function (that external function), but first it will affect lower cortical structures (meaning those underneath that area)
Lobes of the cerebrum (6)
1) Frontal
2) Temporal
3) Parietal
4) Occipital
5) Limbic
6) Insular
Functionals of the frontal lobe? (2)
1) Motor
2) Personality
Functionals of the temporal lobe? (3)
1) Auditory
2) Learning
3) Memory
Functions of the parietal lobe? (1)
1) Sensory
Functions of the Occipital lobe? (1)
1) Intense emotions
Functions of the Insular lobe? (2)
1) Awareness of sensation
2) Limbic (some of those limbic functions are also tied in [intense emotions])
Deep structures of the cerebrum? (5)
1) diencephalon
2) Basal ganglia
3) Internal Capsule
4) Amygdala
5) Hippocampus
Sensory and motor homunculus
motor biggest = hands / lips (because we talk / manipulate small objects)
* think about why we would need it = fine motor control / dextairty
* for a dog this would be different
What are our 5 basal ganglia nuclei
1) Caudate
2) Putamen
3) Globus pallidus
4) Subthalamic nucleus (STN)
5) Substantia nigra
Which 3 basal ganglia are located in the cerebrum?
1) Caudate
2) Putamen
3) Globus pallidus
Which one of the basal ganglia is located in the diencephalon?
Subthalamic nucleus
Which basal ganglia is located in the midbrain?
Substantia nigra
basal ganglia are primarily involved in the control of …
* They also have waht kind of functions?
Motor activities
Also have psychologic functions
* think social / goal orientated behavior
* Think “do I run traffic light if running late for job interview”
* being happy vs frightened to see a dog
* they have non motor functions as well
KNOW: Certain medications that treat movement disorders exert their effects by interacting w/ basal ganglia structures
* makes sense because the primary function of the basal ganglia is motor activities
What two main things does the diencephalon do?
* What about the 8 other functions
1) Process emoion
2) Process some forms of memory
Other things it does
1) Regulate consciousness
2) Regulates attention
3) Maintain body temp
4) Maintain body metabolic rate
5) Maintain body chemical composition of the tissue
6) Regulate eating
7) Defensive and reproducive behavior
8) Influence the secretion of endocrine glands
What four structures does the diencephalon consist of?
1) Thalamus
2) Hypothalamus
3) Epithalamus
4) Subthalamus
KNOW: Thalamus = master control of homeostasis
KNOW: Several drugs affecting sensation and control of the body functions manifest their effects by interacting w/ the thalamus and hypothalamus
What is the large, egg shaped collection of nuclei in center of cerebrum?
* What does it do?
* What is it termed
Thalamus
Nuceli relay info to cerebral cortex, process emotional and some memory information, integrate different types of sensations, or regulate consciousness, arousal and attention
Termed the gateway to the cerebral cortex
What is lcoated inferior to the thalamus?
* what does it do (6)
Hypothalamus
1) Maintains body tem
2) maintains Metabolic rate
3) maintains body Chemical comspoition of tissues and fluids w/ an optimal functional range
4) Controls ANS
5) Link between NS and endocrine system
6) Circadian rhythms
What is located posteriosuperior to thalamus?
* What does it contain
* What does it do?
Epithalamus
Contains the pineal gland, which influences the secretion of other endocrine glands, including pituitary and adrenal
* Hormone secretion
What is located inferiolatearl to the thalamus?
* part of waht that controls what
* part of what?
Subthalamus
Part of the neural circuit that controls movement
Part of basal ganglia
What is the order of the brainstem from rostural to caudal?
Midbrain –> Pons –> Medulla
What 3 things does the reticular formation do?
* What part of the brain is it apart of?
1) Monitors/Controls consciousness
2) Regulates arousal
3) Regulates alrtness
Part of the brainstem
KNOW: CNS drugs that affect the individuals arousal state tend to exert their effects on the reticular formation
* makes sense this area does arousal and alrtness
EX: Sedatives decrease activity, caffeine increases activity
What is considered the little brain?
Cerebellum
Which part of the brain coordinates motor activity?
Cerebellum
Which part of the brain is responsible for comparing the actual movement with the intended motor pattern?
Cerebellum
It can make in the moment intrinsic adjustments
Which part of the brain controls the vestibular mechanisms resposnible for maintaining balance and posture?
Cerebellum
Damange to the cerebellum leads to ipsilatearl or contralateral deficits?
Ipsilateral
There is minimal crossing of these tracts
KNOW: for the cerebellum therapeutic medications are not usually targeted directly for the cerebellum, but incoordination and other movement disorders may result if a drug exerts a toxic side effect on the cerebellum (because it coorinates motor activity)
What two things does the limbic system do?
1) Emotional
2) Behavioral activity
What strucutres is the limbic system made from? (7)
1) Amygdala
2) Hippocampus
3) Cingulate gyrus
4) Hypothalamus
5) Thalamic nuclei
6) Mammilary bodies
7) Septum pellucidum
And others
NOTE: These are very deep structures
KNOW: For the limbic system CNS drugs affecting these aspect of behavior, including some antianxiety and antipsychotic medications, are believed to exert their beneficial effects primarily by altering activity in the limbic structures
* Remember limbic system does emtional and behavioral activity
KNOW: They gray matter (central butterfly) is an area of the spinal cord for synaptic connection between neurons
Surrounding white matter: myelinated axons, ascending/descending tracts between brain and SC
How many pairs of spinal nerves are their?
31 pairs
Cervical region, spinal nerves are found above or below the corresponding vertebrae?
- Except which one?
Above
Except the 8th spinal nerve which is found below C7 and above T1
The rest of the spinal nerves below this are found below their respective vertebrae
Do the thoracic, lumbar, sacral, coccyx spinal nerves run above or below their number?
Below
EX: L2 spinal nerve runs inferior to L2 vertebrae
What is the white matter in the spinal cord?
Myelinated axons, ascending/descending tracts between brain and SC
KNOW: Spinal cord
- Certain CNS drugs exert some or all of their effects by modifying synaptic transmission in specific areas of gray matter, while other CNS drugs, such as narcotic analgesics, may exert an effect on synaptic tranmission in the gray matter of the cord as well as on synapses in other areas of the braun
- Some drugs may be specificially directed toward the white matter of the cord. Drugs such as local anesthetics can block action potential propagation in the white matter so that ascending or descending information is interrupted (ex - a spinal block)
What 3 arteries come off of the vertebral artery?
1) Anterior spinal arteries
2) Posterior spinal arteries
3) Posterior inferior cerebrallar artery
The anterior and posterior spinal arteries branch off what artery?
* What two areas of the brain do they supply?
Branch off the vertebral artery
Supply the
1) Spinal cord
2) Medulla
The posterior inferior cerebellar artery branches off what artery?
* It supplies what two structures?
Branches off the vertebral artery
Supplies the:
1) Medulla
2) Cerebellum
What artery turns into the basilar artery?
Vertebrals come together as the basilar artery
The basilar artery is the combination of the two vertebral arteries. The basilar artery branches into what 4 arteries?
1) Anterior inferior cerebellar artery
2) Superior cerebellar arteries
3) Posterior cerebral artery
4) Posterior choroidal artery
Anterior inferior cerebellar artery and the superior cerebellar arteries branch off of what artery?
* What two areas do they supply?
Branch off of the basilar artery
Supply the:
1) Pons
2) Cerebellum
The posterior cerebral artery branches from what artery? What 3 areas does it supply blood to?
Branches from the basilar artery
Supplies blood too:
1) Midbrain
2) Occipital lobe
3) Temporal lobe
The posterior choroidal artery is a branch off what artery? What 3 areas does it supply blood to?
Branch off the basilar artery
Supplies blood to:
1) 3rd ventricle
2) Thalamus
3) Hypothalamus
The intenral artery branches into what 3 arteries?
1) Anterior choroidal
2) Anterior cerebral artery
3) Middle cerebral artery
The anterior choroidal artery is a branch from what artery?
* It supplies what 5 areas?
Branch off the internal carotid artery
Supplies:
1) Lateral ventricle
2) Visual pathway
3) Basal ganglia
4) Internal capsule
5) Hippocampus
The anterior cerebral artery is a branch off what artery?
* It supplies what two areas
Branch off the internal carotid artery
Supplie:
1) Frontal lobe
2) Parietal lobe
The middle cerebral artery is a branch off what artery?
* It supplies what 3 things?
Branch off the internal carotid
Supplies:
1) Basal ganglia
2) Internal capsle
3) Most of lateral hemisphere
Circle of willis:
* ACA, ICA, PCA (x2) anastomse with 3 smaller arteries (1 ant/2 post communicating arteries)
* Allows distribution of blood to hemispheres if blockage present (MCA not part of it - damage here is very bad because it doesnt have a way to route blood around because its not part of the circle of willis)
* SO HELPS w/ BLOCKAGE
review
Lateral corticalspinal tract does what?
Motor
Dorsal column medial lemniscus tract does what
Sensory
What does the anteriolateral system do?
Sensory
Anterior = ventral = medial when talking about the tracts
Main tracts:
1) Dorsal column medial lemniscus (sensory)
2) Lateral corticospinal (motor)
3) Anteriolatearl system (sensory)
Dorsal Column Medical Lemniscus
* Is it sensory or motor?
* what 3 things does it convey
These are our posterior column pathways
Sensory
Conveys:
1) Proprioception
2) Vibration sense
3) Discriminative touch
The fasciulus gracilis and fasiculus cuneatus are both bundles of nerve fibers in the SC. However, the are specifically apart of what tract?
* What is the function of each?
* They are above and below what level?
Specifically part of the Dorsal Column medial lemniscus (sensory)
Fasiculus gracilis: area where lower limb/lower trunk medial neurons are located below T6
Fasiculus cuneatus: area where upper limb/upper trunk and neck lateral neurons are located Includes T6 and above
Where does the DCML (sensory) decussate (cross)?
Decussation = lower medulla
The DCML sustains a lesion caudal to the medulla (i.e., cortex/cerebrum/intera; capsule, midbrain, pons, upper medulla). What kind of loss is this?
Contralateral loss
You read it from top to bottom because it starts in the brain. So if your loss is above the decussation (which is the lower medulla) than the loss will be contralateral. however, if the lesion is below the decusation the loss will be ipsilatearl
The DCML sustains a lesion lower than the medulla. are the loses ipsilateral or contralateral?
Ipsilateral. It crosses in the lower medulla so any lesions lower than that will provide ipsilatearl loss (i.e., lower medulla/SC/peripheral regions = ipsilateral loss)
Anteriolatearl system (ALS) =
Spimpthalamic tract
What 3 things are does the anteriolatearl system (spinothalamic tract) convey?
* Is it motor or sensory?
Sensory
Conveys:
1) Pain
2) Temp
3) Crude touch
Where does the anteriolateral system (spinothalamic tract) decussate?
Spinal cord (spinothalamic has spine in it)
An Anteriolateral system (spinothalamic tract) lesion that occurs in the cortex/cerebrum/internal capsule/midbrain/pons/medulla/SC leads to an ipsilatearl or contralateral loss
Contralateral loss below the level of the lesion (always looking from brain down)
NOTE: the decessation of this tract is in the SC basically right where the peripherla nerve jumps off, which is why the SC was included (because most of the SC is above the decusation, it only decusates right when it jumps off the SC)
A patient sustains an ALS/Spinothalamic tract lesion in the periphery. Are the loses ipsilatearl to contralateral
Ipsilatearl.
The decussation is in the SC at the level of where it hops off. The lesion is below the decussation = ipsialtearl loses
Crude touch = touch that you cannot specifically pinpoint
* Think itch / tickle / hair on your arm
Remember these are DCML branches
Spinothalamic = Anteriolatearl tract (sensory)
Notice the decussation is in the SC, however it decusates in the SC right before it hops into the periphery, meaning a lesion in the SC above this decussation leads to a contralateral loss (because the lesion is above the decusation)
DCML vs ALS contralateral vs ipsilatearl loss
DCML decusation = lower medulla
ALS = SC at level where peripherl nerve jumps off
Latearl corticospinal tract
* Motor or sensory?
* Decussation?
Motor (controls movement of the extremeitities)
Decussation = medulla
The Lateral Corticospinal tract (descending / motor) sustains a lesion above the medulla, is the loss ipsilatearl or contralateral?
Contralaterl weakness (weakness because its a motor tract)
Remember, you read these from top to bottom. The decussation in the medulla so if it has a lesion caudal to that than the loss will be contralateral
The latearl corticospinal tract sustains a lesion below/after medulla (think SC) where is the weakness found?
Ipsilateral the lesion (because the decusation is in the medulla)
Results in impaired voluntary control of movement BELOW the level of the lesion
What two tracts decusate in the medulla?
DCML (lower medulla)
Lateral corticospinal tract (medulla)
The lateral corticospinal tract is subdivided into two sections. What are they?
* What are the functions of each?
Lateral corticpsinal is divided into latearl and anterior subdivisions (but they both control motor because this is a motor tract)
Lateral = limbs = appendicular (think apendiges = limbs)
Anterior = neck, shoulders, trunk = axial
Peripherial region
* Encompasses the PNS
* Peripheral nerves are groups of axons
* Examples of nerves within the peripheral region/PNS –> median, ulnar,scatic and Cranial nerves
Dividing line shows PNS vs PNS
Remember cranial nerves named from anterior –> Posterior
She said know these
Dermatomes
myotomes
Lower motor neurons = Motor neurons
What are the only neurons that convey signals to extrafusal and intrafusal skeletal muscle fibers?
* They are the direct connection
Motor neurons (lower motor neurons)
Extrafusal: Standard m fibers that make up the bulk of skeletal muscles
* responsbile for m contraction and generating forces to move bones
* What we typically think of when considering m action during movement
Intrafusal: Specialized fibers found within muscle spindles, which are sensory receptors located in muscles
* Intrafusal fibers do not contribute to muscle contraction in the same way as extrafusal fibers, instead they detect change sin muscle length and rate of change
*
Motor neurons (lower motor neurons) are composed of alpha and gamma (two types of LMNs)
* Both types have cell bodies where?
* Axons leave the SC through the … Root
* What is a motor pool?
Both alpha and gamma have cell bodies in the ventral horn of the spinal cord (makes sense, anterior is motor, and these are LMNs)
Axons leave the SC through the ventral root
Motor pool = area of cell bodies whose axons project to a single muscle
What is a motor pool?
* What are the 4 pool types?
Area of cell bodies whose axons project to a single muscle
Pool types:
1) Medial pools
2) Lateral pools
3) Anterior pools
4) Posterior pools
Medial pools innervate what two kinds of muscles?
Innervate axial and proximal muscles
Lateral pools innervate what one muscle type?
Innervate distal muscles
Anterior pools innervate what muscle types?
Extensor muscles
Posterior pools innervate what muscle types?
Flexor muscles
What happens to affected muscles if the LMN cell bodies and/or axons are destored? (5)
The muscles become denervated and undergo:
1) Decrease or loss of reflexes
2) Paresis or paralysis
3) Atrophy
4) Decrease or loss of muscle tone
5) Fibrillations
These are loss of function signs (I ahd this and now I have less of this)
CNS:
* In the brainstem and SC, interactions among signals from somatosensory neurons and descending upper motor neurons (UMNs, may also be called motor tracts) determine output from lower motor neurons (LMNs) to muscles
Upper motor neurons =
Motor tracts
Descending UMNs pathway:
Path is brain (CNS) –> LMNs in brainstem or SC
Postural/gross movement tracts (UMN) control what (2)
1) Control contraction of antigravity muscles
2) Groups of limb muscles
Selective motor control tracts (UMNs) control what (1)
Isolates contraction of individual muscles of limbs and face
Nonspecific tracts (UMNs) facilitates all …
LMNs
KNOW: Cerebellum and motor basal ganglia adjust activity in the descending motor tracts (UMNs), resulting in excitation or inhibition of LMNs
In all regions of CNS, sensory information adjusts motor activity
UMN syndrome signs (think stroke/SCI)
Loss of function signs (absence of a geature that is normally present)
* Paresis and paralysis
* Impaired selective motor contorl
* Absent or decreased muscle tone (flaccidity and hypotonia)
Gain of function signs (presence of a feature that is not normally present)
Spasiticity
* Myoplasticiity
* Hyperreflexia
* Excess reticulospinal drive (abnormal synergies)
* Rigidity
* Abnormal reflexes
* Compensatory and pathologic concetraction
Absence of a geasture that is normally present
Loss of function signs
Presence of a geasture that is not normally present (think spasticiity)
Gain of function signs
Putting together regions / subdivisions but adding the diagnosis
Primary roll of the sympathetic NS
* also regulates what 3 things?
Maintain optimal blood supply in the organs
Also regulates body temp/metabolic rate and regulates activities of viscera
What are thw two principal functions of the parasympathetic NS?
1) Energy conservation
2) Storage
Think rest and digest
Sympathetic/Parasympathetic effects
What are the 3 main stages of learning a motor skill? and what are they?
1) Cognitive - What to do
2) Associative - How to do (putting the peices together)
3) Autonomous - How to succeed (think being able to suceeed in environments that are variable and uncertain)
When looking at movement/motor learning we examine these things in the picture below
Things we can document
* Time
* Distance
* Outcome
* Retention
* Transfer task
* Environment
Variables to manipulate w/ motor learning
The ability of neurons to change their function, chemical profile (amount and type of neurotransmitters produced), or structure
Neurplasticity
The reorganization of neural connections within the brain
Plasticity
KNOW: Neuralplasticity enables people to recover from enural injury
Does neural regeneration occur in the CNS or PNS?
Occurs in the PNS but none in CNS
KNOW: There are limitations to nerve regerneration in CNS due to (oligodendrocytes secrete growth inhibiting substances, astrocytes form glial scars, lack of nerve griwth factor (this is secreted in the PNS by schwann cells)
Transected aons will send out new sprouts but this ceases after how long?
* therefore CNS damage can be permanent
2 weeks
Does swelling help neurons?
No, its very detrimental to neurons
KNOW: recovery of function in the CNS occurs if other regions take over that function
Experience dependent plasticity: Learning and memory
* This process requires the synthesis of new proteins, the growth of new synpases, and the modification of existing synapses
* Results in persistent, long-lasting changes in synaptic strength
* Hippocampus (declarative memory - example = names and events)
* Basal ganglia/motor cortex/cerebellum (procedural memory EX = motor tasks like riding a bike)
Hippocampus is resonbile for what kind of memory
Declartive memory
EX: Names/events
Basal ganglia/Motor cortex/cerebellum are responsible for what kind of emmory?
Procedural memory
EX: Motor tasks like riding a bike
Explicit memory = Declaritive
Implicit memory = Procedural
10 principles of neuroplasticity
1) Use it or lose it
2) Use it and improve on it
3) Specificity (task needs to be specific to deficit)
4) Repetition
5) Intensity (can’t be easy)
6) Time (quick care after injury)
7) Salience (has to be meaningful to pt)
8) Age
9) Transference (tasks need to relate to others)
10) Interference (gaps, medical issues etc.. can affect chances of recovery)
CNS organization
* Cerebrum
* Basal ganglia
* Diencephalon
* Brainstem
* Cerebellum
* Limbic system
* Spinal cord
Unique structure and function of CNS capillaries, which act as a selective filter and protects the CNS by limiting the substances that enter the brain and SC
Blood brain barrier (BBB)
Drugs need to cross BBB to reach CNS!
Clinical pharmacotheraptucs (drug –> CNS)
* Ensure adequate delivery to brain and SC for optimal effects
* Lipid soluble drugs can pass via passive diffusion
* Barbiturates (ex phenobarbital) - causes relaxation or drowsiness, used for seizures, slows activity in the brain
BBB can remove drugs and toxins from brain
* It is a slective filter
Chemical that convey information among neurons =
Neurotransmitters
Do neurotransmitters produec exciation or inhibition of the other neurons?
Both!
KNOW: Neurotransmitters are released by a presynaptic neuron and act directly on postsynaptic ion channels or activate proteins inside the postsynaptic neuron (meaning they are local to the postsynaptic membrane)
Affect the postsynaptic neuron either directly, byt activiating ion channels (ionotropic), or indirectly, by activating proteins inside the postsynaptic neuron (metabotropic)
Neurotransmitter release results in the generation of a local potential
Neurotransmitters can act postsynaptically two different ways. Explain each
Can act directly by activating ion channels (ionotrophic)
Can act indirectly by activating proteins inside the postsynaptic neuron (metabotropic)
What neurotransmitter has a role in coginition and memory; regulates control of movmeent and autonomic function?
Acetylcholine
What is the primary CNS location of acetylcholine? (4)
1) cerebral cortex
2) Basal ganglia
3) limbic and thalamic regions
4) Spinal interneurons
Iacetylcholine has a generl effect of
CNS = exciation
KNOW: In the PNS acetylchiline has a significant role at the neuromusuclar junction
Dopamine:
* Role (3)
* Location (2)
* General effect (1)
* what kind of chemical is it?
Role:
1) Motor control
2) Mood
3) Emotions
CNS location:
1) Basal ganglia
2) Limbic system
General effect:
1) Inhibition
Amines
Norepinephrine
* Role (1)
* Primary CNS location (1)
* General effect (1)
* Chemical
Role:
1) Active surveillance by increasing attention to sensory information, “fight or flight” reaction to stress
Primary CNS location:
1) Neurons that originate in brainstem and hypothalamus and are projected throughout other areas of brain
General effect:
1) Inhibition (overall effect following synapse is often general exciation of brain)
Amines
Serotonin
* Role (3)
* Primary CNS location (1)
* General effect (1)
* Chemical
Role:
1) mediating pain
2) Mood
3) Behavior
Priamry CNS location:
1) Neurons originating in brainstem that project upward (to hypothalamus) and downward (to spinal cord)
General effect: Inhibition
Amines
What are the 3 Amines?
1) Dopamine
2) Norepinephrine
3) Serotonin
What are the 3 Amino Acids?
1) GABA (gamma-aminobutyric acid)
2) Glutamate
3) Glycine
GABA
* Role (1)
* Primary CNS location (1)
* General effect (1)
Role
1) Prevents neural overactivity
Primary CNS location
1) interneurons throught SC, cerebellum, basal ganglia, cerebral cortex
General effect
1) inhibition - principle inhibitory NT
Glutamate
* Role (2)
* Primary CNS location (1)
* General effect (1)
Role
1) Learning / Development
2) Excitotoxicity
Primary CNS location
1) Interneurons throughout brain and SC
General effect
1) Exciation - principle excitatory NT
Glycine
* Role (1)
* Primary CNS location (1)
* General effect (1)
Role
1) Process motor/sensory infor (movement, vision, auditory)
Primary CNS location
1) Interneurons in SC / brainstem
General effect
1) inhibition (but GABA is the primary inhibitory NT)
What are our 2 peptides
1) Substance P
2) Enkephalins
Substance P
* Role (1)
* Primary CNS location (1)
* General effect (1)
Role
1) Pain modulation
Primary CNS location
1) Pathways in SC and brain that mediate painful stimuli
General effect
1) Exciation
Enkephalins
* Role (2)
* Primary CNS location (1)
* General effect (1)
Role
1) Endogenous opioids
2) Pain inhibition
Primary CNS location
1) Pain supression pathways in SC and Braain
General effect
1) Exciation
Following the route of neurotransmitters
General mechanisms of CNS drugs:
CNS drugs work by modifying synaptic transmission
1) In order to treat specific disorders
2) Or to alter the general level of arousal of the CNS
EX: Phychotic behavior: associated w/ overactivity in central synapses that use dopamin as a neurotransmitter
* Drug therapy in this situation consists of agents that decrease activity at central dopamine synapses
Parkinsons disease: decrease in activity at specific dopamine synapses
* Antiparkinsian drugs attempt to increase dopaminergic transmission at these synapses and bring synaptic activity back to a normal level
CNS synapse: sites where drugs can alter transmission:
1) Action potential arrives at presynaptic potential; NT release initated
2) Synthesis of NT
3) Storage of NT
4) Release of NT
5) Reuptake of NT back into presynaptic terminal
6) Degradation of released NT
7) Action at the postsynaptic receptor (allowed or blocked, agonist vs antagonist)
8) Presynaptic autoreceptors (present on some types of chemical synapses)
9) Membrane effects (organization and fluidity may be altered)
Alterations can happen at lots of places. Amazong that pharcuiticals can alter at all these places
Drugs affecting the brain and SC usually exert their effects by modifying synaptic transmission
1) Drugs may be targeted for specific synapses in an attempt to rectify some problem w/ transmission at that particular synapse
2) Drugs may increase or decrease the excitability of CNS neurons in an attempt to have a more general effect on the overall level of consciousness of the individual
So it can be more torageted or it can be more general
The picture below shows the interaction between norepinephrine, serotonin and dopamine
So its hard to specifically treat some psychologic disorders because of this overlap between drugs
Interactions:
* Illustrates the interplay between NE, Serotonin, and DA to control mood, anxiety, appetitite, motivation, and other emotions and behaviors
* Difficult to design drugs to treat specific psychological disorders because of the interplay and overlap (positive is w/ the overlap, the brain is able to alternate pathways for feelings and behaviors)
Example: drugs designed to specifically inhibit impulsive behavior are likely to have side effects on emotions, aggression, cognition and anxiety
Norepinephrine is a critical mediator of attention and arousal
* overactivity of the norepinphrine system contributes to panic and post-traumatic stress disorder
Diagnostic Tests
CT scan
* Rapid and realtive inexpensive snapshot of the CNS
* Damaged within tissue can be identified
* Most benefical in acute intracranial hemorrhage
MRI
Study choice to evaluate all lesions in the brain and spine
* Modality of choice for detecting cogenital malformations
* Infection of the spine better evaulated by MRI
Note that CT is more sensitive for subtle fractures, calcifications and acute subarachnoid hemorrhage
Cannot be performed on patients w/L intraorbital forign bodies, pacemakers, or non-MRI compatible implants, such as artifical heart valves, vascular clips, cochlear implants, or ventilators. May require sedation for some individuals with cognitive impairment or intolerance for small spaces
FMRI
Based on blood oxygenation level-dependent imaging of the brain and provides evidence of cerebral activation during any given task (ex - motor, visual or cognitive), typically in contrast to a resting or control state
Shows both neuroanatomy and functions of the brain and is a brain mapping tool
Noninvasive procedure with no known risks, FMRI is used for presurgical mapping of motor, language and memory functions and allows neurosurgeons to be aware of and to navigate the precise location of corticies and structural anomalies from space occupying lesions
PET
Cellular activity via regional blood flow in the brain
Used to monitor changes in the brain with functional activity
Can be used to depict the regional density of a number of neurotransmitters, allowing researchers to better understand the role of different parts of the brain during activity
PET/CT combo - provides powerful metabolic and anatomic information
DATSCAN
Single photon emission CT markers of the presynaptic dopamin transporter system (DaT) allow differential diagnosis of neurological conditions affecting the basal ganglia
Looks at dopamine reuptake in basal ganglia
DTI
Analysis of structural integrity of white matter tracts through quantifying anisotrophy of diffusion of water in white matter
EEG
Cerebral ischemia produces neuronal dysfunction, leading to slowing of frequencies or reduced amplitude in EEG tracing
Generalized (globial ischemia) or regional (focal ischemia)
Depth of ischemia is associated w/ the severity of EEG changes
EEG cannot assess the whole cerebral cortex, however, and is less reliable at assessing subcortical structures (makes sense because its so superficial)
Evoked potentials
Electrophysiologic evoked potentials measure brain responses to various forms of stimulation (somatosensory, auditory, visual)
Used as a daignostic adjunct to move conventional imaging for various neurologic conditions
Transcranial Doppler Ultrasonography
Uniquely measures local blood flow velocity in the proximal portions of large intracranial arteries
Near-infrared spectroscopy
Uses light optical spectroscopy in the near-infrared range to evalaute brain oxygen saturation by measuring regional cerebral venous oxygen saturation
Transcranial magnetic stimulation
Brain stimulation technique that allows study of the phsyiology of the CNS, identifying the functional role of specific brain structures and exploring large scale network dynamics
Diagnostic value as well as thearpeutic potential (treatment) for several neuropsychiatric disorders
Used for things like anxiety and depression
Electrodiagnostic studies - NCS and EMG
Nerve conduction studies also called nerve conduction velocity
* Sensory or motor
* Evaluation fucntion of peripheral nerves
* Typically performed w/ electrode
Electromyography
* Looking at: muscle activity, CNS vs PNS
* Surface electrode or needle
So one is muscle and the other is nerve
NCS
EMG
Needle EMG
at rest nothing should be going on
fibrilation always pathological
The aging brain shows only a small loss of neuron if its healthy. #?
10%
How much does the brain shrink per year after the age of 30?
0.8% per year after 30
Why does the brain weigh less w/ age?
Due to the thinning of myelin
KNOW: Older brains have fewer synapses, postsynaptic receptors, dendrites and smaller amounts of neurotransmitters
How much does BF to the brain decline between 33 and 61?
23%
The aging brain
* Sensory receptors become less sensitive because the action potential threshold icnreases w/ age
* Older neurons are more stiff with less fluid and respond less effectively to sensory stimulation
* Some LMNs in SC and brainstem are lost w/ age
* Fewer large motor units are present and remaining LMNs each innervate more skeletal muscle fibers
The aging NS
The functional effects of these changes include:
* Skeletal m atrophy
* Less precise control of movement
* Decreased sensitivity of the somatosensory system
* Processing speeds slow
* Neuroplasticity decreases (but still present throughout life!)
Interventions
Methods to control central nervous system damage
* Damage and disease can result from changes in prodiction and reuptake of neurotransmitters
* Drug therapy can stimulate or regulate NT release and/or NT synthesis
* Other drugs can protect the cell membrane
* Stem cells - embryonic vs adult (now somatic)
Treatment of nonneural dysfunction
* many drugs used to treat neurological disorders influence nonneural tissue, including cerebral blood vessels and glia
* Certain drugs control cerebral edema
* Viruses that replicate nonnueural tissue
Prognosis
Links diagnosis to outcomes and identifies need for treatment
Physiological basis for the recovery of function
* after injury - changes in structure and function of neurons occurs
* Regardless of the cause of the dysfunction, resultatnt signs and symptoms depend on the site and size of the lesions
* Neural shock (cerebral shock, spinal shock)
* Redistribution of cortical mapping
* Neural modifiability or adaptation
* Learning
1) During the intital phases of motor learning, large and diffuse regions of the braina re active
2) When tasks are repeated, the # of active regions in the brain are reduced
3) When a motor task is learned, only small, distinct regions of the brain show an increased activity when performing a task
