All Nervous system Flashcards
Where is potassium concentration highest?
inside the cell (makes it more negative inside the cell)
where is sodium concentration highest?
outside the cell
has more positive charge
what does the Na/K atpase pump do?
Pumps 3 sodium ions out and brings 2 potassium ions in
What prevents equilibrium of Na and K in the cell??
Na+/K+ ATPase pumps so we
(refer to the resting membrane
potential to be in the steady-
state)
what is the equilibrium potential for sodium?
+65 mV
what is the equilibrium potential for potassium?
-85 mV
what is an EPSP?
EPSPs will change the resting membrane potential to become more positive
What is an IPSP?
IPSPs will change the
resting membrane potential
to become more negative
what is spatial summation?
multiple neurons fire at the same time, but from different locations
and the areas of depolarization overlap
what is temporal summation?
multiple stimuli from the same
neuron occurs in rapid succession
Summation occurs at the _______ and starts the process of ________
axon hillock
axon conduction
When there is significant depolarization of the cell membrane what happens to Na channels?
they open causing significant depolarization (look at image on slide 382)
what helps repolarize the membrane?
opening of voltage gated K channels (downstroke)
what is the overshoot or delayed rectifier phase?
too much K enters making the cell hyperpolarized for a bit
what is the difference between absolute and relative refractory periods?
- The absolute refractory
period is the time when a
second action potential
cannot be conducted no
matter how great the
stimulus. - The relative refractory period
is the time when voltage-
gated sodium channels are
resetting, and a second
action potential can be
conducted as long as the
second stimulus is greater
than the first.
What inactivation also
allows the axon
potential to be
conducted in one
direction
Na channel inactivation (as the impulse travels down axon the Na close to make sure the potential only goes down the axon and not back up)
the larger the diameter of the axon, what happens?
less internal resistance so higher conduction velocity
where might you find large axonal diameter nerons?
Type A-alpha nerve fibers.
* These are efferent skeletal
muscle motor neurons
Type A-beta are involved in:
pressure and touch sensations.
HIGHLY MYELINATED
- Type A-delta are involved in:
fast pain, such as extremes in
pressure and temperature.
highly mylinated
- Type C fibers are involved in
slow pain and are postganglionic
autonomic nerve fibers.
not myelinated
________ are responsible for the development of the resting membrane potential.
Leak channels
______ leak channels make up the majority of this channels and allow for the resting membrane potential to be negative.
Potassium
Once the membrane potential meets threshold at the axon hillock, then an action potential will occur. This will require the opening of _____________
voltage-gated
sodium channels
_____________ channels will be responsible for the upstroke of the action potential and will undergo rapid inactivation.
Voltage-gated sodium
This along with the opening of _________channels will cause the downstroke of the action potential.
voltage-gated potassium
Since voltage-gated potassium channels are slower in closing this will result in an after ________ phase
hyperpolarization (undershoot)
what is the difference between a electrical and chemical synapse
electrical: gap junctions that allow small molecules to pass
chemical: neurotransmitters
what is an ionotropic post synaptic receptor?
receptors allow for ions to enter into the postsynaptic cell (usually sodium or calcium)
In order for a neurotransmitter to be released, there must
be an _______________ within the terminal button
increase in intracellular calcium
what is an metabotropic post synaptic receptor?
receptors require cell metabolism, and this is typically through a G-protein coupled receptor (GPCR) pathway
is ionotropic or metabotropic receptors faster action?
ionotropic is faster
what are some ways signals are terminated at the chemical synapse?
diffusion, degradation, autoreceptors, reuptake, or endocytosis of postsynaptic
receptors
what is an example of an auto receptor?
Alpha-2 adrenergic receptor (auto receptors release the neurotransmitters to themselves)
what do neuromodulators do?
enhance or diminish the
pre-synaptic and postsynaptic membrane potential
The neurotransmitter must then bind to either an_____ or ______ receptor unless it is a gaseous neurotransmitter.
ionotropic or metabotropic
The action potential is conducted down the axon to open up:
voltage- gated calcium channels. Calcium is the GO signal!
Increase in intracellular calcium at the terminal button will cause:
exocytosis of neurotransmitter and release into the synaptic cleft.
What are peripheral receptors?
specialized cells in the peripheral nervous system that respond to stimuli and allow us to perceive and interpret the world
examples chemoreceptors, mechanoreceptors, baroreceptors, thermoreceptors
nociceptors
what is anesthesia?
The loss of sensation or conscious response to a stimulus
(this is a destructive lesion)
what is Paresthesia?
an abnormal feeling of touch, such as tingling, burning, prickling, numbness, or pins & needles
what is hypesthesia?
a reduced sensitivity to touch. It can be temporary or permanent (irrative lesion)
what is the DMCL pathway?
dorsal column, medial lemniscus pathway– sensory pathway for CNS. fine touch, vibration, proprioception
For the DCML pathway what is the path it takes?
-dorsal column (first neuron)
-nuc gracillis/cutaneous in medulla (second neuron)
-third order in the thalamus to cerebral cortex
[detailed] what the first step of the DCML pathway?
Pacinian corpuscle detects the vibration
[detailed] what the second step of the DCML pathway?
goes into spinal cord and ascends into the cuneate fasciculus
[detailed] what the third step of the DCML pathway?
up to lower medulla, nucleus cuneatus (second order neuron cell body)
[detailed] what the forth step of the DCML pathway?
at the same level of the nucleus cuneatus there is a decussation of medial lemniscus
[detailed] what the fifth step of the DCML pathway?
then ascends through medulla, pons, midbrain (still in medial lemniscus)
[detailed] what the sixth step of the DCML pathway?
gets to ventral posterolateral nucleus of thalamus (VPL) second order neuron synapses here
[detailed] what the seventh step of the DCML pathway?
gets to third order neuron (stays on same side of body) projects to upper limb area of the cortex
be able to identify the pre and post central gyrus
kk
where does the sensory information go in the brain?
post central gyrus (somosensory cortex)
what does the spinothalamic pathway detect?
pain, temperature, itch
How does the ALS conduct its sensory information?
picked up by sensory ending, enters dorsal root ganglion, goes to cell body of first order neuron, unmyelinated type C (pain info much slower than others), enters second order neuron at dorsal horn, synapses right away, cross midline of spinal cord– decussates, also at level info came in, second order neuron goes up to third order neuron which is also in the ventroposteiolateral portion of the thalamus, then goes to postcentral gyrus
what is different about the synapses of the ALS vs DCML pathways
ALSO synapses at the level the level it comes in, DCML ascends all the way up before synapsing
What are some examples of voluntary movements
movements that improve greatly with practice, like piano, typing or reading
what are some examples of semiautomatic movements?
Mostly controlled by
brainstem and spinal cord
circuits, but INITIATION and
TERMINATION of movement
under cortical control
ex running or chewing, scratching
what are examples of involuntary motor movements?
least cortical control, reflex type movement like pulling hand away from hot object
what are lower motor neurons?
neurons in the spinal cord or brainstem that directly innervate skeletal muscles
what are upper motor neurons?
neurons in the cortex or brainstem that regulate LMN (enable complex movement for)
what is a local circuit neuron?
–Receive both sensory and UMN input
–Regulate LMNs – provide coordination between muscle group
what do upper motor neurons form?
descending tracts in white matter
what are basal ganglia and cerebellar nerves?
Regulate UMNs to help initiate movement, enable temporal and spatial precision and correct movement errors
- LMNs for the head, neck and face are in the ___________
cranial nerve motor nuclei of the brainstem
LMNs for the trunk, limbs and extremities are in the ________
spinal cord
Spinal cord lower motor neurons are located in _______
the ventral horn of the spinal cord
what is a somatopy?
when a part of the body is associated with a distinct location in the CNS
what do lower motor neurons give rise to?
axons that exit via ventral roots and travel to synapse directly with muscles
What is the medial ventral horn?
LMNs projecting to axial muscles and proximal limb muscles
what is the lateral ventral horn?
LMNs projecting to distal limb muscles
What would be the symptoms of a lesion to the motor root at T1?
inability to move the muscles, adduct and abduct fingers
what are brainstem LMN?
Cranial nerve nuclei in the brainstem contain neurons whose axons innervate muscles in the head and neck
-can control one muscle or small subset of muscles
(example oculomotor nerve)
what is a local circuit neuron?
interneurons that terminate on lower motor neurons, integrate information from multiple sources and translate it to LMN
where do axons on UMN originate? where do they go?
cortex, travel to spinal cord forming lateral motor systems, synapse on LMN in SC controlling distal muscles
where do axons on UMN originate? where do they go?
Axons of UMNs originating in the brainstem form the medial
motor systems that synapse on LMNs controlling proximal
musculature
what are the three steps in voluntary movement?
planning, initiation, execution
What is involved in the planning phase?
UMNs in “association” areas (secondary motor cortices)
what is involved in the initiation phase?
UMN in primary motor cortex
what is involved in the execution phase?
LMN in brainstem and spinal cord
what brain areas are involved in planning?
premotor and supplementary motor area
the premotor cortex receives input from where and why?
parietal and occipital cortices – helps select movements based on external sensory stimuli such as visual or auditory input
what brain area is involved with initiating movement?
primary motor cortex
what do secondary motor cortices do?
Function in motor planning – selecting andcoordinating movements based on internal and external clues
the premotor cortex is on the ____ side of the brain
lateral
the primary motor cortex is on the _____ surface of the brain
medial
if a subject is told to do a guided task: a lightbulb flashes above a single key, they should play that key. They are told a tone will sound before the light
flashes, to warn them that the task is about to begin
then when does the premotor cortex fire?
When the tone sounds, but before the light flashes, neurons in the premotor cortex fire action potentials
◦ No movement has yet happened – premotor cortex is planning movement that will be performed
what is the supplementary motor area involved in?
planning complex sequences of movement, especially:
–Internally triggered movements
–E.g. selecting movements based on remembered sequences, mental ‘rehearsal’
–Coordinating two-handed movements
could be considered muscle memory tasks
in the piano example when would the supplementary motor cortex come into play?
if the subject was asked to play the ‘C’ chord shown below, coordinating both hands would cause neurons in the SMA to fire
Primary motor cortex (posterior portion of precentral gyrus) job is:
initiates signal to LMNs so that they in turn stimulate muscles to
contract to execute specific movements
what is in the coticospinal tract?
- Primary motor cortex (M1) – superior and medial surfaces
- Supplementary motor area
- Premotor cortex
where does the corticospinal tract course?
cortex, corona radiata, internal capsule, crus cerebri of midbrain, fiber bundles on base of pons, pyramids of medulla, decussate in caudal medulla
The lateral CST:
- Lateral CST:
- 80-90% of fibers
- Runs in the lateral funiculus of the SC
- Terminates unilaterally on LMNs in the lateral ventral horn
what is the function of the CST?
- Voluntary movements from neck to feet
◦ Lateral CST especially important for finely controlled, dexterous movements across a single joint
(most imp tract clinically
where does the lateral corticospinal tract originate?
sensorimotor cortex:
* Primary motor cortex
* Premotor and supplementary motor cortices
what is the course of the lateral corticospinal tract?
sensorimotor cortices corona radiate internal capsule
crus cerebri pontine fiber bundles pyramids pyramidal
decussation lateral funiculus of the spinal cord
reticulospinal tract originates in:
nuclei un reticular formation of pons/medulla
what is the function of the corticospinal tract?
movement of contralateral limbs, fine movements (e.g. of arms, hands, fingers, legs, feet, toes)
where does the corticospinal tract terminate?
unilaterally at all levels of spinal cord (mostly at cervical and lumbosacral enlargements)
what is the origin in the corticobulbar tract?
primary motor cortex
supplementary motor area
premotor cortex
what is the function of the reticulospinal tract?
control of trunk and proximal limb muscles to correct posture during anticipated instability (ex reaching for something out of reach so must shift center of gravity first)
what is the difference between vestibulospinal and reticulospinal tract?
vestibulospinal- feedback loop
reticulospinal- feedFOWARD loop
what is lower motor syndrome?
LMNs leads to death or atrophy of these neurons and their axons producing a collection of symptoms called LMN syndrome
what are symptoms of LMN syndrome
Paralysis and rapid muscle atrophy are symptoms
what is upper motor neuron syndrome?
weakness of muscles, abnormal reflex
how can you tell the difference between UMN and LMN syndrome?
lower lowers
upper increase
go over practice Q’s
