Test 2 🧠 Flashcards
What is the purpose of hyperpolarization of cells?
Used by body to suppress activity
Inside cell is more negative, takes more stimulus to turn on
Suppresses electrical activity in excitable cells
What happens in regard to voltage gated Na channels if cell isn’t repolarized?
They won’t be able to be used for another action potential
Fewer voltage gated Na channels or no voltage gated channels = no action potential
Differentiate between voltage gated Na channels and voltage gated Ca2+ channels:
Same structure as voltage gated Na channels
Voltage gated Ca channels are slower
Known as slow Ca channels
What is Dihydropyridine?
class of calcium channel blockers (blocks DHP receptor)
Why is chloride useful in neurons?
Important in CNS
Hyperpolarize/ suppress electrical activity in excitable cells
How are chloride channels opened up to allow for hyperpolarization in the cell?
GABA receptors open up chloride channels in neurons
Increase chloride permeability= makes cells more negative and more difficult to excite
Stages of action potentials:
- Resting
- Stimulus causes depolarization to an area
- Action potential spreads
- Resetting after depolarization
What generates the depolarization during the initial phase of an action potential?
Outside force causing area of depolarization–Na coming in through channels
Starts with a small area: outside electrical stimulus,
Ex: electrodes hooked up to a muscle
Ex: taserOu
Where are most of the voltage gated Na channels located?
Cell wall
Why are they called voltage gated sodium channels?
VG Na channels open up when there is enough initial depolarization
VG Na channels open up when there is a change in membrane voltage (membrane depolarizing)
What happens after VG Na channels open?
depolarization spreads and more VG Na channels are activated
action potential is fired
How does an action potential travel?
Spreads away from initial area of excitement
What affects how the depolarization wave travels?
2 way propogation:
-if initial excitation in middle
-AP travels both way
-shorter amount of time to depolarize
(EX:taser, paddles to chest)
1 way propogation:
-initial excitation is on one end
-potential travels opposite direction from one end to the other
-takes longer to get entire activation
How does repolarization wave travel?
Repolarization moves in the same direction as initial depolarization
Describe how actions potential are positive feedback:
positive feedback is the basis for normal propagation of action potentials
initial stimulus –> Na comes in–> activates VG Na –> MORE Na comes in
amplifies intial response of letting Na in
Aside from external stimuli, What is another way we could have activation of initial depolarization?
Through a process mediated by a neurotransmitter
Motor Neuron
Set of neurons that are specialized to talk to skeletal muscles
attach to skeletal muscles and activate them
Where do motor neurons communicate with the skeletal muscles?
Each skeletal muscle fiber talks to at least one motor neuron
How do motor neurons communicate with skeletal muscle?
neurotransmitters
What would be the process if the brain wants to contract a muscle?
Motor neuron activated in spinal cord–> activation produces action potential that moves from brain to spinal cord–>action potential reaches where motor neuron connects with muscle
What is the path that action potential flows through a neuron?
action potential flows from top pf neuron down to distal end
What releases neurotransmitter?
Motor neurons
What is the NMJ
Neuro Muscular Junction: area that connects 2 cells together via neurotransmitter
need receptors on target cell
What are the neurotransmitter receptors on skeletal muscle?
nicotinic acetylcholine receptor (nAch)–specialized for skeletal muscle (some in brain)
differ from acetylcholine receptors in other parts of the body
How does acetylcholine bind to the receptor?
2 binding sites
each site should be occupied simultaneously for the channel to allow current through it
donut shape protein in cell wall
-lined with amino acids (-) charge–repel negative electrolytes
What are the nAch receptors specific to?
specific for charged ions–negative charge on inside of channel created by amino acid lining
What generates majority of current through nAch receptors?
Sodium
Describe how nAch receptors enable an action potential:
Motor neuron needs to excite skeletal muscle–> sends neurotransmitter –> neurotrans binds to nAch receptor –> nAch receptor opens up and allows Na+ to flood into cell
Why are the nAch receptors called nicotinic?
nicotine can stimulate this neurotransmitter
ex: a bunch of nicotine can stimulate acetylcholine being released from motor neurons (causing tremors, shaky)
Why is Na+ the predominant current through nAch and not Ca2+?
Na+ is smaller than Ca2+
chemical and electrical current for Na+
Is there other current through nAch channels besides Na+?
-Small amount of K+ that can leak out: most is prevented from moving out because there is so much Na+ it boots it to the side
-a little calcium: Comes into cell but much less than Na+ because Ca2+ is big and clunky (doesn’t fit through channel very well)
Where are the voltage gated Na+ channels in relation to the nAch receptors?
VG Na+ channels are usually situated next to nAch receptors
initial current though nAch receptor sets off VG Na+ channels since they are close by
Is there potential to run out of nAch receptors in healthy person?
in a healthy person this system is robust: way more channels that we actually need, more VG Na+ channels than we need, receptors are in large abundance–so anytime we get acetylcholine release from motor neuron skeletal muscles will contract
Where do paralytics work?
Neuromuscular junction
What happens if there is dysfunction relationship between CNS and skeletal muscle?
Skeletal muscle is a large compartment of intracellular container
if dysfunction relationship then causes massive problems–things that are not suppose to be sequestered in skeletal muscle leak all over the place
What mediates the interaction at the NMJ?
depolarization mediated event
Wha change would be expected in a cell if we are trying to slow something down?
Hyperpolarization
(inhibition)
What are mAch-R?
Muscarinic acetylcholine receptors
responsive to a chemical called muscarine–found in rainforest
Where in the body are mAch-R located?
heart, smooth muscle, lungs
What is the purpose of mAch-R in the heart?
Mediate pumping levels of heart and electrical activity by controlling how hyperpolarized the cell is
Where in the heart are mAch-R found?
Pacing centers (SA/AV nodes)
Where is the SA node?
right side of heart
Where is the AV node?
top of the septum
What is the path that actions potentials take in the heart?
SA node–>atria–>AV node–> ventricle
What nerves are specialized in communicating with SA/AV nodes?
Vagus nerves: come into contact with pacing structures in the heart
Which vagus nerve innervates each node?
Right vagus nerve innervates SA node
Left vagus nerve innervates AV node
What neurotransmitter is released by vagus nerve in the nodal area?
Acetylcholine
What type of receptor is mAch-R?
GPCR
Describe mechanism of action for mAch-R:
Acetylcholine binds to receptor–> alpha subunit from muscarinic Ach receptor are now activated –> alpha moves away from receptor–causes K+ channels in cell wall to open
What is a task of the alpha subunit of mAch receptors?
- communicate with K+ channels in cell wall to open more
What is the relationship between acetylcholine and K+ channels?
when there is a lot of acetylcholine around–there are lots of K+ channels open
leaky channels and extra K+ channels that can be activated with Ach
What happens to membrane potential when the cell has more K+ channels open?
K+ leaving the cell
cell is more negative
increased electronegativity (makes cell more difficult to excite but can still excite)
What effect does the hyperpolarized Vrm have on the heart?
influences how fast pacemakers works
When looking at heart beat, what does the trough between beats indicate?
Vrm
What happens in the heart if we adjust Vrm lower than normal?
Hyperpolarized: cycle would have lower starting point and will take longer to get up to area where action potential is fired
What is the function of Ach mediated hyperpolarization in the heart?
Used by body to pump the breaks on heart
we have alot of Ach being released by vagus nerve all the time–keeps the heart in check
What happens with massive vagal stimulation of the heart?
Expect heart rate to slow down:
-K+ permeability increases
-pacemaker cells are hyperpolarized
-HR slows down
What is a side effect of Antimuscarinic meds?
side effect: increased HR
blocks acetylcholine from binding to GPCR
alpha subunit no longer active
K+ channels close and makes cell more +
Vrm more +: starting point for heart beat is closer to point where action potential will fire (shorter time between action potential so increase HR)
Describe how basline Ach activity effects the heart:
Atropine blocks normal vagus activity on heart
this implies alot of baseline Ach activity normally because if there wasnt baseline activity of Ach through muscarinic receptors then atropine would have no effect
What does atropine do to the heart?
blocks normal vagus activity on the heart (inhibits the breaks)
If there was no CNS influence how would resting HR change?
without CNS: HR would want to beat 100-110bpm
CNS slows that down with Ach and mAch-R to resting rate 70-72bpm
What is the main thing muscarinic receptors mediate?
K+ permeability
(through GPCR alpha subunit)
How is an action potential generated with physical pressure?
specialized structure gives off sensor then another structure takes sensor info and passes to CNS
What is an important pressure sensor in the heart?
Baroreceptor
lots of pressure sensors in the heart
What happens in regards to action potentials with light vs increased pressure?
Repeated action potentials with a lot of pressure
slower action potentials with light pressure or maybe no action potentials
What is the structure of pressure sensors that allows for action potentials?
pressure sensitive Na+ channels inside sensor
little pressure: not alot of Na+ permability
when pressure is applied, sensor get flattened out–walls of Na+ channels get wider and more Na+ can come in
Describe how increased physical pressure affects action potentials:
more pressure= more open N+ channels= more Na+ comes in and if + enough can create action potential
Why are pressure sensors necessary?
CNS uses them to keep an eye on whats going on around us
How are nerves classified?
Size
Myelination state
How does diameter of neuron affect action potentials?
Small diameter fibers are slower
Larger diameter fiber sends faster
largest neuron diameter 20micometers
smallest neuron diameter 0.5micrometer
How is myelination state categorized?
A fibers: heavily myelinated
B fibers: lightly myelinated
C fibers: non myelinated
Give example of nerves in the body that are myelinated:
motor neurons: Big and heavily myelinated
What type of info is carried by small unmyelinated fibers?
Crude info–ex: cold/warm, tickle
What are the smaller subunits that neurons are divided into?
Alpha
beta
gamma
delta
(from largest to smallest category)
Describe the cell body of a neuron:
also known as SOMA
all neurons have cell body
contains nucleus, mitochondria, place to build things the cell needs
some synapses on cell body
How does the threshold potential affect the action potential?
this is the bar that the stimulus has to get over to create an action potential
- if you barely pass it, it takes longer to have an action potential
- if you fly past the bar then you have an action potential quickly
What causes an extension of action potential in the heart? (the pause)
the slow calcium channels
How does extracellular chloride affect membrane potential?
It brings negative charges into the cell to make it harder to excite
- also could hyperpolarize the cell
- keeps the “brakes” on the nervous system
How does extracellular calcium affect electrical excitability of the cell?
It has two positive charges with a huge chemical gradient - it has a calming affect on the excitability
What does calcium do to the sodium channels?
It is BIG and CLUNKY and sits at the entrance of the cell wall and blocks the influx of sodium
- this limits resting sodium permeability through sodium leak channels
- inhibits electrical activity of the cell
How does hypocalcemia affect the excitability of the cell?
There is less calcium to block the sodium channels, so more sodium influx makes the cell more positive
Why would giving supplemental calcium to a patient help them?
It would block more sodium permeability to make a more negative membrane potential aka make it not as excitable
How does calcium affect skeletal muscle?
If a motor neuron is not surrounded by a normal amount of calcium, the membrane potential would be more positive and it would increase the amount of contractions happening in the muscle (tetany or trousseau’s sign)
How does magnesium function?
A lot like calcium, it’s large and has a double positive charge
- makes things more hyperpolarized
- reduces electrical activity of a cell or the heart
What are the main things that affect the rate of electrical propagation?
- length of the nerve (longer nerve = longer to get there)
- width (wider = quicker)
- insulation (more insulation = faster action potential) ex. myelin sheath
Describe the myelin sheath
- made from sphingomyelin in the cell wall
- Schwann cells grows and wraps itself in a spiral around the neuron
- each layer is compacted and the water is squeezed out which leaves a lipid layer for protection
How exactly does myelination help with action potential?
It covers up the Na/K pumps which will prevent sodium from coming out - it will keep it in the cell and have to keep moving downstream to make the action potential faster
- this also reduces the energy requirements of the cell
- myelinated neurons are less prone to ischemia
How does a myelinated neuron affect anesthesia?
If they’re myelinated, they will need more local anesthetic to block them because of the high density of fast sodium channels at the nodes
What is saltatory conduction?
The movement of sodium from one node to the next - since the sodium can’t move out, it must move forward
What are the cells that are responsible for creating and maintaining myelin?
Oligodendrocytes and Schwann Cells
Where are oligodendrocytes located?
CNS - brain, spinal cord, cranial nerve 2, retinas
Where are Schwann cells located?
Peripheral nervous system
What happens if there is demyelination?
The stuff (pumps) sitting under the myelin start to disappear
- Fast sodium channels and VG potassium channels start to go away
- this leaves only Na/K pumps that push the sodium out and it cuts the action potential short
What are some common causes of demyelination?
Guillain-Barre, infection, MS, autoimmune response to vaccines, genetics
What type of synapses occur at dendrites?
Can be excitatory or inhibitory in nature for target
Differentiate excitatory Vs inhibitory interactions at synapse:
Excitatory: more positive membrane potential
Inhibitory: lower than average membrane potential–hyperpolarization. more difficult to excite
How many connections can a neuron have with other neurons?
Some neurons have connections with over 10,000 of their neighbors
Common with decision making neurons because receiving input from lots of different places)
Why do we not have myelinated dendrites?
Messages wouldnt be able to get through to receptors. Myelin would get in the way of the synapses
What is the Axon?
specialized to send action potentials quickly
most axons are myelinated
nodes of ranvier
How are action potentials conducted quickly through the axon?
Axons are usually myelinated
Nodes of ranvier–Na+ current jumps from one node to the next
Presynaptic terminal
tail end of sending portion of neuron (axon)
synapse of target cell
presynaptic portion of next synapse in pathway
What mediates inhibition at the axon hillock?
GABA mediated inhibition
Axon hillock
Very beginning part of axon
input from other places in nerbous system that suppresses over activity in neurons
4 inhibitory connections–GABA mediatef
How do GABA receptors function?
Increase chloride permeability–increase chloride means more inhibition of cell
GABA is key component of controlling electrical activity in CNS
What would happen if all GABA is removed?
Inhibition is removed
would expect over the top crazy levels of CNS activity–Seizures
Explain the physiology of an alcoholic going through withdrawals:
Alcohol is GABA receptor agonist
Alcoholics who drink alot over a long period of time, body stops producing their own GABA
If you take alcohol away and body isnt producing any of its own GABA–results in massive overactivity of CNS and seizures
How does GABA work at the axon hillock?
Makes sure no over activity of axon–CNS break system
no excitatory connection at axon hillock
Why are there no excitatory connection at the axon hillock?
They would bypass the rest of the cell–no longer decision makers if cell isnt taking to account all connections with other parts of the nervous system
Difference between glial cells and neurons?
glial cells divide/multiple and neurons do not really
If you had a brain tumor what kind of cells would it likely be?
Glial
neurons do not divide quickly
List the macroglia cells:
Astrocytes
Ependymal cells
Oligodendrocytes
Schwann cells
Astrocytes
Star shaped
Appendages connect with outside of endothelial cells
Attach to capillaries in the brain
How do astrocytes function as supporting structures?
Projection from cell body of astrocyte (astrocytic end foot) wraps around capillaries surrounding CNS for support
How are astrocytes useful in CNS?
Support
Maintain electrolyte balance in CNS–CSF buffer, important in maintaining pH of CSF
Ependymal cell function:
Useful in producing CSF and moving CSF around
MAIN SOURCE OF CSF–cilia used to help CSF move downstream and around entire system until it exits
Oligodendrocyte function:
Myelin producing cell in CNS
Schwann cell function:
Myelin producing cell in PNS
Microglia
Small nervous system cell
Immune system for any structure that contains CSF
Good at digesting things that need to be broken down
Function as Macrophages in CSF
What would happen if there is a dead cell in the CSF?
Microglia would break it down
Multipolar Neuron
Decision making cells
Decide whether or not to fire action potential
Lots of area for communication with other neurons
What is an example of multipolar neuron?
Motor neuron
EX: If there are enough pain sensors telling motor neuron something is painful the motor neuron would make decision to move
Bipolar Neuron:
Sensory–sense and pass info along
2 projections used in special organs
Optic nerve
photoreceptors in retina send action potentials to brain
Pseudounipolar neuron:
Majority of sensory cells parked in spinal cord or immediately outside spinal cord
sensing–cell body does not make decisions
What is the purpose of the cell body in pseudounipolar neurons?
Exists as a place to build proteins and replace things in the neuron
cell body supports the rest of the structures
Are decisions made in pseudounipolar neurons?
Decisions are made by sensor itself then relays info from dendrite down to axon and pass info to CNS
True unipolar
Said we didnt have to know but also said we didnt have to know amino acids SOOOOOO
these neurons are not found in humans (only in lower life forms)
What is another term for sensible / sensing neurons?
somatic
What is the purpose of free nerve endings?
Pain sensors/ nociceptors
Other examples from lecture of pressure sensors:
Pacinian corpuscle
Messiners corpuscle
Golgi tendon apparatus
Muscle spindle
What is the function of the golgi tendon apparatus?
Feedback on skeletal muscles
Pressure/stretch sensors integrated in tendons that are connected to skeletal muscle
Muscle spindle
Woven skeletal muscle
confirms if a muscle has contracted or not
How do somatic sensory receptors function in the body?
Take a physical environmental disturbance and turn into electrical signal that is relayed to rest of the body
What is adaptation of sensors?
resetting/ adjustments to new normal
some sensors adapt slow others adapt quickly–some do not adapt at all
Explain reverse adaptation:
Really strong stimulus for long period of time–becomes more sensitized to that stimulus
Function of baroreceptors?
Monitor and adjust BP for changes from normal
What is the purpose of resetting baroreceptors?
Gives the body ability to adjust BP changes from new normal
allows room to change up signal being fed into brainstem
Gives us ability to have a system work at different set points
What would happen if we didnt have baroreceptor adaptation?
If baroreceptors kept firing at fast rate with increase BP unadapted system would be limited in response to further changes from new normal
About how long does it take baroreceptors to adapt and is it considered fast or slow?
takes around 2 days
slow adaptation
most specialized sensors adapt much quicker
Why do sensors adapt?
Often adapt to give ability to sense change
CNS set up this way to be efficient–cut down signals where it can to decrease noise
EX: holding ball example
Somatic sensor blocking variables:
attached to neurons of different sizes or myelination
some are easier to block with local anesthetic than others depending on orientation (if on outside of nerve bundle or buried further into nerve )
What dictates how sensitive sensors are with blockage of local anesthesia?
Anatomy
What are some other ways for cells to talk to each other?
Electrical or Chemical Synapse
What is an electrical synapse made of?
- 6 Connexin proteins assemble to make a Connexon
- 2 Connexon create a gap junction
- Connexon sits in the cell wall and connects with a neighboring cell with a connexon
- this creates a conduit to allow for current to move between the cells
What is a downside to using an electrical synapse?
It can operate in both directions - if you have a rogue action potential circling the heart then it could be bad
What is another term for electrical synapse?
Gap junctions
What ions can travel through a gap junction?
All small ions can travel through, but the majority of the current is sodium
What type of transport is a gap junction?
Simple diffusion
What makes up a chemical synapse?
Sending cell = presynaptic terminal
Receiving end = postsynaptic terminal
A - Telencephalon
B - Diencephalon
C - Brain Stem
D - Cerebellum
C1 - Midbrain
C2 - Pons
C3 - Medulla Oblongata
A - frontal lobe
B - Central sulcus
C - Occipital lobe
D - Cerebellum
E - Temporal lobe
F - Lateral sulcus (temporolateral fissure)
Longitudinal Cerebral Fissure
A- Anterior Rootlets
B- Anterior Root
C- Posterior Rootlets
D- Posterior Root with Spinal Ganglion
E- Spinal Nerve
A- Vertebral Arch
B- Superior Articular Process
C- Pedicle
D- Vertebral Notch
E- Lamina (difficult to mark with this view–after the pedicle)
F- Inferior Articular Process
G- Inferior Articular Facet
H- Spinous Process
I- Vertebral Body
A- Vertebral Foramen
B- Vertebral Body
C- Pedicle
D- Spinous Process
E- Superior Articular Facet
F- Transverse Process
G- Superior Articular Process
How is sensory info transmitted?
Once info is in dorsal horn–it hops over to ascending pathway in white mater to be routed up toward brain and brainstem
What is the dividing point between CNS and PNS?
Spinal Nerve
How does motor info travel in the spinal cord?
Motor information is sent out the front of the SC through anterior horn
How does sensory info enter the spinal cord?
Sensory info enters horizontally through posterior rootlets
Comes in from the side and enters the back of the cord to interact with cell bodies in the dorsal horn
Where are the majority of ascending pathways in the spinal cord located?
In the rear of the spinal cord
Some in the front and a few on the lateral sides of the cord
What are examples of signals that get sent through ascending pathways?
Sensory stimuli
pressure sensors, pain sensors
What happens at the spinal nerve anatomically?
Combination of sensory and motor pathways
How do motor signals contribute to the spinal nerve?
Motor signals come out of the cord
Relayed through anterior rootlets
Pass through anterior root
Then joins sensory info from the back of the cord to create the spinal nerve
What is the function of most spinal nerves?
Mixed sensory and motor function
What is unique about posterior root compared to anterior root?
Posterior root– big lump
Lump is collection of cell bodies from Pseudounipolar (sensing) cells
Bulge area called Spinal Ganglion
Why are there no ganglion in the anterior root?
Anterior deals with motor so most of those cells are Multipolar cells–cell bodies will be in the anterior horns
What is primary function for descending spinal tract and where are these pathways located in the spinal cord?
Function for motor signal
Pathway on lateral sides of spinal cord and some in anterior
How many spinal nerves do we have?
2 spinal nerves at every level of vertebrae
one exiting on left side, one exiting on right side
How many cervical vertebrae do we have? How many cervical spinal nerves?
7 vertebrae
8 pairs of spinal nerves
Why do we have more cervical spinal nerves than cervical spinal vertebrae?
C1 spinal nerves come out about C1 vertebrae, all of the other cervical spinal nerves exit under the next vertebrae (C2 nerves come out below C1)
How many thoracic vertebrae and spinal nerves?
12 thoracic vertebrae
12 pairs of thoracic spinal nerves (exit underneath vertebrae)
How many lumbar vertebrae and spinal nerves?
5 lumbar vertebrae
5 pairs of lumbar spinal nerves (exit underneath vertebrae)
How many sacral vertebrae and spinal nerves?
At birth we have 5 sacral vertebrae–fuse as we age
5 pairs of sacral spinal nerves associated with original vertebrae
named for vertebrae they originate under
How many coccygeal vertebrae and spinal nerves?
Start with 4 coccygeal vertebrae–fuse into 2 coccygeal vertebrae as adults
one extra set of coccygeal spinal nerves
What are dermatomes used for?
Dermatomes are different regions of the body that are innervated by spinal nerves–topical map where spinal nerves are routed (dermatome man)
Generically where do the cervical, thoracic, lumbar, and sacral spinal nerves innervate?
Cervical nerves: Sensory top of neck and back of head
Thoracic nerves: Chest area
Lumbar Nerves: front of legs
Sacral nerves: back of legs/butt
How can we identify where the spinal nerves are on a person?
Use anatomical spine markers-spinal nerves comes out of spinal column
What is the typical spine curvature for a young/healthy person?
“S” curvature (front to back curvature)
Neck: Lordosis (anterior curve)
Thoracic: Kyphosis (posterior curve)
Lumbar: Lordosis
Sacral/coccygeal: Kyphosis
Where is the most common place to have abnormal curvature of the spine?
Thoracic Kyphosis–common
Occurs with age–posture change–hunch back
What happens with pathologic amounts of curvature in the spine?
Destabilizes overall structure of the spine and puts pressure on structures held within the spine
What is scoliosis?
Abnormal lateral curvature of spine (left and right)
Common problem–most people that have it don’t even know–sometimes its bad enough to need surgery
Common pathologic spine curvature:
Kyphoscoliosis: combo of 2 abnormal curvature
abnormal kyphotic curvature and abnormal scoliotic curvature
What is the shape of the spine at birth and why is development crucial?
Only Kyphotic curve at birth
Ex: why its hard for newborn to hold head up–anatomical problem because center of mass on a structure that is incapable of absorbing movement
Cant start walking/balancing until “S” shape curve starts to form crucial development process
What is the point of the vertebral body?
Large weight supporting structure
Intervertebral disc sits on vertebral body
How does vertebral body size correlate with different levels of the spine?
Higher up in spine= smaller vertebral body
Lower back has a lot of weight to support so need the vertebral body to be bigger
What is the purpose of the vertebral arch?
Encases the cord and spinal roots/spinal nerves
What is a process in anatomy?
a body extension
Area for vertebrae to connect
What are the palpable bumps on our back?
From the spinous process on each vertebrae
How many transverse process do we have per vertebrae?
2
How many superior articular processes per vertebrae?
2–processes that fit together with processes from the bottom of the vertebrae above
What does the term articular mean?
Connecting one thing to another
How many inferior articular processes per vertebrae?
2–connect with superior articular processes in vertebrae below
What is the purpose of inferior vertebral notch?
Located under the pedicle
Provides an area where spinal nerve can exit on each side of spine
What is the point called where superior articular process and inferior articular process connect?
Inferior/superior articular facet–cartilage
What structures are in all cervical vertebrae?
Vertebral foramen (wide)
Vertebral arch
Body
Superior articular process
Superior articular facet
What are the specialized structures only found in the neck vertebrae?
Bifid spinous process (only in cspine) C2-C5
Transverse foramen
Sulcus in transverse process
Which cervical vertebrae are expected to be bifid?
C2-C5 almost always bifid
C6: 50% of the time
C7: 0.3% bifid (usually a single spinous process)
Where is the transverse foramen located and what is its purpose?
Located in the transverse processes
Where the vertebral arteries run through
2 vertebral arteries (one of each side of neck)
Supply the back of the brain
What are the blood supplies for the brain and brainstem?
2 Vertebral arteries: back of brain
2 Carotid arteries: anterior brain perfusion
Which vertebrae has transverse foramen?
All cervical vertebrae
C7 has transverse foramen but vertebral artery doesn’t pass through it
What is the sulcus in the transverse process?
Hollowed out groove where cervical spinal nerves can hang out
What is anatomical term for hollowed out spot?
Sulcus
“sulcus in transverse process for spinal nerve”
Why is vertebral foramen larger in cervical vertebrae compared to lower back?
The spinal cord is wider and larger at the neck compared to lower back
Further down on the cord the less info is sent
More info being sent by the top of the cord so it should be wider
What is the name for C1 vertebrae?
Atlas: specialized to create clean attachment to base of skull
specialized vertebrae
What is the name for C2?
Axis: unique connection with C1
Typical Cervical Vertebrae
A- Spinous Process
B- Vertebral Foramen
C- Lamina
D- Pedicle
E- Transverse process with sulcus for spinal nerves
F- Transverse Foramen
G- Superior Articular Facet
H- Body
What are the fucntions of each lobe?
- Frontal: thinking
- Parietal: primary somatosensory cortex
- Occipital: primary visual cortex
- Temporal: processes hearing and language comprehension
Define these terms:
Sulcus
Fissure
Gyrus
Sulcus = groove
Fissure = really deep groove
Gryus = “lump” of tissue - separated by grooves
How does information get from one side of the brain to the other?
Corpus callosum bridges the two sides
Where does language comprehension take place?
Wernicke’s area (temporal lobe)
Where does word formation take place?
Broca’s area (frontal lobe)
Where are emotional responses developed?
Limbic system
Why is grey matter in the spinal cord a darker color?
- less myelin
- has lots of cell bodies where the decisions are usually made
Why is white matter in the spinal cord a lighter color?
- there’s more myelin
- not as many cell bodies
How does the left and right side of the spinal cord communicate with each other?
- Lamina X in the grey matter
- Anterior white commissure in the white area
How does CSF travel?
It is produced in the brain and travels through the central canal of the spinal cord
- the canal is lined with ciliated cells that pushes CSF down the cord
How does information travel through the spinal cord?
Sensory information comes in the back through the dorsal horn and motor function comes out the anterior horns in the front
A: Corpus Callosum
B: hypothalamus
C: Pons
D: Medulla oblongata
E: Cerebellum
F: Occipital Lobe
A: Dorsal horns
B: Anterior horn
C: Anterior Median Fissure (sulcus)
D: Anterior white commissure
E: Central Canal
F: Posterior median Fissure (sulcus)
What is the name of C1 and where does it come from?
Atlas - Mythical god who held the weight of the world on his shoulders
What’s the biggest difference of C1?
There’s no vertebral body - it doesn’t need to support as much weight
Where is the “pivot point” in C1?
The anterior arch is where C2 connects to C1 and provides a rotational axis
What is the opening at the base of the skull called?
Foramen magnum
What are occipital condyle for?
Downward projections in the base of the skull that have cartilage to fit together with C1
What is the ligament that connects the top of the spine to the base of the skull?
Atlantooccipital ligament
What does the axis have that’s specific to it?
Dens - bony projection that connects to C1
- it creates a connection that allows your skull to rotate
What is C2 called?
Axis
What is different about the ligamentum flava flav?
- they are more stretchy
- it may feel different if you hit it with a needle
- could have a midline that’s not fused completely
Where is the vertebral prominens?
- it’s the marker in the back of the neck that divides the cervical and thoracic spine
- if you look in a textbook it will say C7 but Schmidt says it’s more like T1
Why don’t you see thoracic spine injuries very often?
There’s alot of things connected to this part of the spine so this makes it stronger and more robust
Why is the thoracic spine hard to access with a needle?
The spinous processes are all angled downward so a midline approach would be hard
What are true ribs and where do they connect on the spine?
- the first 7 ribs that connect directly to the sternum from a piece of cartilage
- they connect to costal facets on the body of the vertebra and the transverse process
What are false ribs?
Ribs 8, 9 and 10 that don’t have a dedicated connection to the sternum;
- they connect to the cartilage on rib 7
What are floating ribs?
The last two ribs that aren’t connected to the rest of the thorax
- they are very easy to jar loose from the connecting spots
What are the unique structures of the thoracic spine?
- downward facing spinous facet
- 2 costal facets on the back of the vertebral body (superior and inferior costal facet)
- the shape of the body is in the shape of a heart & the left side is flatter because it is compressed by the aorta
Where do the head and neck of the ribs attach?
- Head attaches to the costal facets of the vertebral body
- Neck comes in contact with the costal facet of the transverse process at the coastal tubercle
Label Atlas
A: Superior Articular Facet
B: Posterior Arch
C: Posterior tubercle
D: Transverse process
E: Transverse foramen
F: Anterior arch
G: Anterior tubercle
H: Facet for dens
A: Occipital Condyle
B: Foramen Magnum
A: Anterior articular facet
B: Dens
C: Superior articular facet
D: Posterior articular facet
E: Body
F: Transverse process
G: Spinous process
A: Vertebral foramen
B: Dens
C: Superior articular facet
D: Anterior articular facet
E: Spinous process
A: Anterior longitudinal ligament
B: Posterior longitudinal ligament
C: Ligamentum flava
D: Interspinous ligament
E: Supraspinous ligament
F: Inter-transverse ligament
Characteristic of lumbar spine:
Large vertebral bodies—-supports a lot of weight
What is the curvature of the lumbar spine?
Lordotic (anterior curvature)
How can you increase chances of successful spinal access in lumbar spine?
Have patient lean forward
Where does the lumbar spine connect with the sacrum?
Inferior articular process of L5 connects with superior articular process from sacrum
Why is lumbar spine popular spot for epidurals/spinal anesthesia?
Anatomy is easier to approach with a needle
Spinous processes angle straight back
And intervertebral foramen
How are the intervertebral foramen formed?
The Pedicles have notches in them—superior and inferior vertebral notches from neighboring vertebrae line up to form Foramen
What the the purpose of the intervertebral foramen?
Openings between vertebrae where spinal nerves can exit the spine
At what point in life does the sacrum become completely fused?
Usually by 14-15 years old
What are the transverse lines on the sacrum?
The points where the vertebrae fused
Where does the intervertebral disc sit in the sacrum?
Sacral Promontory—weight supporting structure at the top of sacrum
What is the purpose of the intervertebral disc on top of the sacrum?
Gives a place for L5 body to rest (cushion)
Opening down the center of the fused sacrum:
Sacral canal
What is located in the sacral canal?
Spinal nerves and nerve roots hang out in sacral canal before they exit
What are the openings in the front and back of the sacrum?
Sacral Foramina
How many sacral foramina do we have?
Anterior and posterior sacral foramina
4 on each side- 8 total anterior and 8 total posterior
What is the function of sacral foramina?
Places where spinal nerves and nerve roots can exit sacrum
A place to get drugs into sacral canal
Posterior sacrum bony prominences that are palpable:
Median sacral crest: spinous processes that have fused together (middle back of sacrum)
Lateral sacral crest: transverse processes have fused (one on each side)
Medial sacral crest: fusion of superior and inferior articular processes (between median sacral crest and lateral sacral crest)
What is a crest in anatomy?
A ridge
Opening at the base of the sacrum and purpose for it:
Sacral hiatus—exit point for coccygeal spinal nerves (1 pair)
Allows some ligaments to pass through
Raised ridges/bumps on either side of sacral hiatus —projections that come off the side
Sacral cornua
A: Inter-transverse ligament
B: Anterior longitudinal ligament
C: Ligamentum flava
A: Anterior longitudinal ligament
B: Ligamentum flava
C: Interspinous ligaments
D: Inter-transverse ligaments
E: Supraspinous ligament
How many coccygeal vertebrae do we have as adults?
2
A: Apex of Dens
B: Posterior longitudinal
C: Anterior longitudinal ligament
D: Nuchal ligament
E: Supraspinous ligament
What type of vertebrae is this?
Thoracic vertebrae
A: Superior costal facet
B: Inferior costal facet
C: Inferior articular facet
D: Spinous process
E: Transverse process
Most superior ridge of the pelvis; palpable even in obese patients
Iliac crest
What level vertebrae would you be at if you draw a line on top of 2 iliac crests?
Middle of L4
below that line–L4-L5 interspace
above that line–L3-L4 interspace
What is the marker of the iliac crests used for?
Epidural marker
2 palpable bumps on the top back side of the pelvis
Posterior Superior Iliac Spines
Marker that we use posterior superior iliac spine for:
Used for markers to estimate access to S2 posterior sacral foramina
Palpate posterior superior iliac spine–drop down 1cm and move 1cm midline
Why S2 and not S1 to get drugs into sacral canal?
If moving perpendicular to the body with a needle–S1 opening is very difficult to hit straight on
S1 openings more to the side than is does to the back
Bump below superior iliac spines:
Posterior inferior iliac spines–much harder to palpate–posterior superior iliac spine is actually visible so it a better marker
What are the attachment points of the inguinal ligament?
Anterior superior iliac spine
Pubic tubercle
Can inguinal ligament be palpated?
Should be able to feel for this if not see it even if patient is obese. Would have to tape up pannus with straps ;)
Ligament that runs on the front of all vertebral bodies down entire length of spine:
Anterior longitudinal ligament
Iliolumbar ligament:
Connects transverse processes of L4 and L5 to the top of the pelvis
Describe anatomical differences in pelvis between men and women:
Women have wider opening in pelvis and broader hips
What is the cartilage that separates the hip bones that come together at the front of the pelvis?
Pubic symphysis
Where is the umbilicus marker and what is it used for?
The belly button–should be at intervertenbral disc between L3-L4
BUT this is not really used because there is alot of variation with extra weight–better to use bony markers
What are the “2 sets of hips” Dr schmidt references in lecture?
Greater trochanter of femur
Sides of pelvis
Supraspinous ligament
Tips of spinous processes all the way down the spine–visualize on posterior pelvis
How many intervertebral dics do we have?
Between each vertebrae–some disc gets lost if vertebrae are fused (no sacral discs)
What is the purpose of the intervertebral discs?
Serve as a cushion between the bodies of vertebrae
What is the intervertebral disc made out of?
Nucleus pulposus: Gel filled center
Anulus Fibrosus: Fibrous housing for nucleus pulposus
What are some of the characteristics of the anulus fibrosus?
FIbers are structured in a crisscross pattern in front of vertebral bodies
Provides alot of strength in the front of the spine
No crosshatching patter in the back of spine–not as strong
What is used to sandwich nucleus pulposus and anulus fibrosus?
Hyaline cartilage places on tops and bottoms of vertebral bodies
What happens with disc herniation?
Injury causing loss of some nucleus pulposus when the anulus fibrosus has a weak spot–leaking out putting pressure on spinal nerve
In what direction do most disc herniations occur?
Nucleus pulposus almost always get pushed out the back since the front of spine is a lot stronger than the back
What are some potential interventions for disc herniation?
Discectomy: try to remove part of disc causing issue; minimally invasive
Fusion: Fuse some vertebrae together for stabilization–put plates and screws in from anterior approach
Laminectomy: Create more space so the spinal nerves isnt being compressed
What is a downside to spinal fusion?
Putting rods/screws into other vertebrae near the issue to stabilize–prevents movement in that area which creates extra stress on levels above and below the fusion
Lumbar fusion risks down the road:
Even if initial procedure is successful–years later need another surgery on vertebrae above and below that are now messed up from the added stress.
Usually not just one procedure because it reduces integrity of shock absorbing and increases stress on spine
How does a laminectomy help with a herniated disc?
Create more space so spinal nerve is not being pushed against intervertebral foramen
removing part of the bone to take pressure off–usually remove lamina (the less bone removed more likelihood for lasting solution)
How can lower back problems be alleviated without surgical interventions?
80% of lower back problem could be fixed with lifestyle changes and PT
Hamstring stretches–hamstrings are tight/rigid these muscles attach to back of spine compresses opening in vertebrae
What are the spinal meninges made of?
Connective tissue
What the are the 3 layers of spinal meninges?
1) Pia Mater
2) Arachnoid Mater
3) Dura Mater
Spinal Cord Pia Mater:
Tight layer stuck to neurons and glial cells in CNS (Neurons and glial cells underneath pia)
SC arachnoid mater:
Superficial to Pia–superficial to all large blood vessels that perfuse CNS
Subarachnoid layer in SC:
Underneath arachnoid layer–Where CSF is contained
Dura Mater in SC:
Outer layer on top of arachnoid mater–tough, robust
Subdural space in SC:
Between arachnoid and dura–potential space (nothing in this space in SC)
A: Body
B: Hyaline Cartilage
C: Nucleus Pulposus
D: Anulus Fibrosus
A: Anterior Longitudinal Ligament
B: Iliolumbar Ligament
C: Anterior Superior iliac Spine
D: Sacral Promontory
E: Inguinal Ligament
F: Anterior Inferior Iliac Spine
G: coccyx
H: Pubic Symphysis
I: Pubic tubercle
A: Superior Articular Process
B: Promontory
C: Anterior Superior Iliac Spine
D: Anterior Inferior Iliac Spine
E: Pubic Symphysis
F: Pubic Tubercle
G: Anterior Sacral Foramina
H: Posterior Inferior Iliac Spine
I: Iliac Crest
A: Iliac Crest
B: Sacral Canal
C: Superior Articular Process
D: Median sacral crest
E: Sacral Hiatus
F: Coccyx
G: Posterior Sacral Foramina
H: Posterior Superior Iliac Spines
I: Posterior Inferior Iliac Spine
A: Sacral Canal
B: Lateral Sacral Crest
C: Median Sacral Crest
D: Medial Sacral Crest
E: Sacral Hiatus
F: Sacral Cornua
G: Posterior Sacral Foramina
H: Superior Articular Facet
Lumbar vertebrae
A: Spinous Process
B: Transverse process
C: Superior Articular Process
D: Inferior Vertebral Notch
E: Superior Vertebral Notch
F: Intervertebral Foramen
G: Vertebral Body
H: Inferior articular process
I: Inferior articular facet
Cells that move portions of electrolytes from blood to CSF:
Ependymal cells
What is the primary mechanism of ependymal cells for producing CSF?
Na+ pump–primary active transport with ATP to pump Na+ into CSF
What do ependymal cells separate?
Separate CV circulatory system and CSF circulatory system
How do anesthetics affect CSF production?
Some anesthetics can increase or decrease the speed of sodium pumping
How does the ependymal cell get electrolytes to make CSF?
Ependymal cells have access to blood for water, Na+, and Cl-
Leaky to Na+ from blood
leaky to Cl- on blood side
water can slip across
How does Cl- and water move over to CSF?
Chloride passively follows sodium (positive charged Na+pulling negative Cl)
Water passively follows Na+ and Cl-
Area where ependymal cells are aggregated together to form a tissue that produces CSF:
Choroid Plexus
What are the main components of CSF?
Na+, Cl-, and water
How are K+ levels regulated in CSF?
Astrocytes–tuck away more than usual
What is a primary location(s) of choroid plexus?
Choroid plexus found in all ventricles
How many ventricles do we have in the brain/brainstem?
4
-2 lateral ventricle
-3rd ventricle
-4th ventricle
Where is the 3rd ventricle located?
Where hypothalamus would be in diencephalon (inner part of brain)
Where is the 4th ventricle located?
Middle of brain stem–anterior to cerebellum
Describe the drainage of CSF through the ventricles:
lateral ventricles drain into 3rd ventricle
3rd ventricle drains into 4th ventricle
4th ventricle CSF can exit from multiple different places
Pathway that allows CSF to flow from lateral ventricles to 3rd ventricle:
Interventricular foramen (Foramen of Monroe)
Pathway that allows CSF to flow from 3rd ventricle to 4th ventricle:
Cerebral Aqueduct (Aqueduct of Sylvius)
What the the pathways for CSF from the 4th ventricle:
1) Central Canal (in spinal cord)
2) Lateral Aperture (2) (foramen of luschka): horns on either side of 4th ventricle
3) Median Aperture (foramen of magendie): CSF exits out the back of ventricle
What is the purpose of the median aperture (foramen of magendie)?
Provide CSF circulation around cerebellum
Pool of CSF fed by median aperture that circulates CSF around cerebellum
Cerebellomedullary cistern (Cisterna Magna)
Why would you want to potentially sample CSF from Cerebellomedullary Cistern?
CSF is fresh/new–would sample from accessing foramen magnum (not used alot because super invasive)
Where is CSF reabsorption occurring?
Arachnoid Granulations: infoldings found at top of brain midline above longitudinal fissure
Explain how arachnoid granulations work?
Mediate majority of CSF reabsorption into CV system: If ICP is too high the arachnoid granulations open up and “blow off” some CSF back to CV system to normalize pressure
Where is another place that a small amount of CSF gets reabsorbed?
Area surrounding the spinal cord
What happens to CSF production if the exit paths get occluded?
CSF is still produced at the same rate–but nowhere for it to go so ventricles enlarge and push on other important structures surrounding the ventricles
If the cerebral aqueduct is occluded, what consequence would this have on brain?
CSF volume would increase in 3rd ventricle/lateral ventricles
(volume above exit point expect to grow in size and compress neurons and glial cells)
What is the most common CSF occlusion site and why?
Cerebral Aqueduct–narrow pathway (tumor or something could get lodged there easily)
Temporary fixes for non-communicating hydrocephalus:
provide path for CSF–Ex: bolt/drain to divert CSF (invasive and issues if they dont work)
Non communicating vs communicating hydrocephalus:
non communicating: blocked pathways CSF uses to exit
communicating: open pathways but CSF isnt being reabsorbed like it should be
Difference in the physical appearance of the brain with non communication and communicating hydrocephalus:
Non-communicating hydrocephalus–ventricle size increase
communicating hydrocephalus: No ventricle enlargement–just increase ICP
What would you expect to happen if a patient had a stroke and there are blood clots in the arachnoid granulations?
Would expect pressure throughout the system to be elevated because the arachnoid granulations are not functioning properly and CSF isnt being reabsorbed
Communicating hydrocephalus
What is the function of the cerebellum?
Part of brain responsible for coordinating complex motor tasks (coordinated movement)
What are the cranial sinuses responsible for perfusing?
The brain and spinal cord
What is a sinus?
a big vein
What is the sinus on top of the skull that runs midline in the sagittal plane?
Superior Sagittal Sinus
Where are arachnoid granulations located?
they sit on top of superior sagittal sinus
Sinus that runs below the most superior sinus in the same plane:
Inferior sagittal sinus
Connective tissues between superior and inferior sagittal sinuses:
Falx cerebri: fan structure, rigid separates left and right hemispheres
What is the tentorium Cerebelli?
extension of the Flax Cerebri down to back of the brain–provides a place for occipital lobe to sit (like a shelf)
What is below Tentorium Cerebelli?
Cerebellum
Straight sinus:
Connects superior and inferior sagittal sinuses–tail end of inferior sagittal sinus (where it straightens out)
Where does blood go after the straight sinus?
Blood can flow in lateral path either to right or left of skull: provides exit point for all venous blood returning through superior and inferior sagittal sinuses
Sinus Confluence:
Area where superior sagittal sinus, inferior sagittal sinus, and straight sinus connect to use lateral exit point
How many transverse sinus do we have?
2–one on each side
What is the purpose or transverse sinus?
Lateral exit point for superior and inferior sagittal sinuses
What is the structure of the sigmoid sinus?
“hairpin turn”
What is the function of the sigmoid sinus?
Blood moves to lateral sides of the skull and then takes a turn (sigmoid sinus) before moving to internal jugular veins
Venous collection pool int he front/middle part of the brain:
Cavernous Sinus
Where does the venous blood in the cavernous sinus come from?
Venous run off from face and front of the brain–it would join sigmoid sinus and then exit cranium via internal jugular veins
what the is function of external jugular veins?
For more superficial structures on the side of the head
What are the 4 vessels feeding arterial circulation of the brain and brainstem?
Vertebral arteries (2)
Internal carotid arteries (2)
Where are the vertebral arteries and carotid arteries located?
Vertebral arteries: running up back of neck (supply posterior of brain)
Internal carotid arteries: feed anterior portion of brain
what is the function of the external carotid artery?
In charge of giving blood supply to more superficial structures
What is normal arterial blood flow in the brain?
750mL/min
What determines blood flow in the brain?
blood flow is due to high metabolic rate of the brain
A: Superior articular facet
B: Costal facet (transverse process)
C: Intervertebral disc
How much of our body weight does the brain account for?
2-3% of our overall body weight
reason why its lopsided that our brain required 15% of our cardiac output compared to its small size
What is the brain blood flow rate based on tissue?
50mL/min/100g of tissue
How much of blood flow in brain is supplied to white vs grey matter?
Grey matter: 80%
white matter: 20%
Why is there an increase in blood flow to grey matter?
decision making happens here so very important
main metabolic requirement of CNS is to get blood flow to grey matter where decision are make and all action is happening
How can the white matter of the brain function without as much blood flow?
White mater is efficient for sending messages (myelinated) without using a ton of activity
A) Transverse Sinus
B) Sinus Confluence
C) Superior Sagittal Sinus
D) Straight Sinus
E) Tentorium Cerebelli
F) Cavernous Sinus
G) Sigmoid sinus
A:Costal tubercle
B: Neck
C: Head
What cells help regulate the contents of the CSF?
Astrocytes
In what order are the layers of the meninge?
Pia mater: directly on top of neurons and glial cells
Arachnoid: on top of pia
Dura mater: robust top layer filled with fat tissue and blood vessels
Where is a good location to do a spinal block?
It’s better to go in an an area where there’s less spinal cord - the neck has a thick cord so this is not ideal
- lower back has projections with more space around them so this is safer
How long is the spinal cord?
It goes from the medulla to the level of L1
What is the end of the cord at L1 called?
Conus medullaris?
What are the two enlargements of the spinal cord and why are they enlarged?
Cervical enlargement - feeds into the brachial plexus
Lumbar enlargement - feeds into the sciatic nerve and lumbar plexus
- they are larger because they have alot of innervations for all of the muscles that need to be controlled
What is the collection of nerve roots at the bottom of the cord called?
Cauda equina (horse’s tail) - roots that haven’t combined yet to form the spinal nerves
What is the filum terminale and it’s function?
extensions of the pia layer - helps keep the spinal cord anchored to the natural position in the spinal canal
A) Dura mater
B) Pia mater
C) Sinus confluence
D) Arachnoid Granulations
E) Superior sagital sinus
Describe the difference between the filum terminale internum and the filum terminale externum -
Internum - inside the dural sac
Externum - starts at the dural sac and goes down to the coccyx
Why is the filum terminale so important?
The growth of the bones in the spine occur faster than the spinal cord, so these ligaments prevent the cord from retracting up as you grow
What is the lumbar cistern?
Also called the dural sac
- storage area where CSF can circulate around the cauda equina
- extends from conus medullaris to the cauda equina
- makes for a good target for a CSF sample
What is the downside of taking a CSF sample from the lumbar cistern?
The CSF down there can get pooled up down there and isn’t well circulated so it can get stale - take these results with a grain of salt because the CSF is older
A) Falx Cerebri
B) Inferior Sagittal Sinus
C) Superior sagittal sinus
D) Straight sinus
E) Sinus Confluence
F) Transverse sinus
G) Sigmoid sinus
H) Cavernous Sinus
I) Tentorium cerebelli
What are some typical access points in the spine?
- Anatomical marker for L4 - above or below
-Sacral hiatus - base of the sacrum - Posterior sacral foramina
If a patient has a skull fracture, where would you suspect a bleed and why?
Epidural bleed - the dura is the layer closest to the skull so the and the fracture can rupture an artery running through it
What types of bleeds are more dangerous, why?
Epidural and Subarachnoid
- these are usually arterial so they will bleed faster and cause more damage
What is the supportive structure that keeps the space between the arachnoid and pia layer?
arachnoid trabecular
Explain the contents of CSF -
pH: around 7.31
Sodium: around 140
Chloride: higher than plasma - close to sodium (140)
Potassium: 40% less than plasma
Magnesium: higher than plasma
Glucose: around 60 meq/dL
Clear
A) Lateral ventricle
B) Cerebral Aqueduct
C) Interventricular foramen (foramen of monroe)
D) 3rd ventricle
E) Corpus Callosum
F) 4th ventricle
G) Lateral Aperture (foramen of luschka)
H) Central canal
I) Median Aperture (Foramen of magendie)
Why do the CSF contents vary from plasma?
the higher chloride, lower potassium and higher mag makes the cell more negative and “keep the brakes” on the central nervous system
Why is the CSF pH lower than blood?
The brain has it’s own buffer system with bicarb to buffer the CO2 that’s being produced
- bicarb is lower than in the blood
A) 3rd ventricle
B) Right lateral ventricle
C) Cerebral aqueduct (aqueduct of Sylvius)
D) 4th ventricle
What are the cerebral sinuses made from?
Wall of sinuses are made up of dura mater–they are robust and rigid compared to other veins in the body
what is the average amount of CSF in the body?
150 ml
How much CSF is produced per day?
500 ml
- replaced about 3x day on average
A: Dura mater
B: Arachnoid mater
C: Tentorium cerebelli
A: Epidural hematoma
B: Arachnoid
C: Arachnoid trabeculae
D: Pia mater
E: Subarachnoid space
F: Subdural hemorrhage
G: Dura mater
What is brain blood flow rate dependent on?
cerebral metabolic activity in the brain
Describe what happens to cerebral blood flow when we are active vs inactive:
If we are using out brain for alot of things–blood flow increases
If we are in a coma–low neurological activity and would expect low brain blood flow
Is there potential for increase in brain blood flow under homeostasis?
usually do not get extra brain blood flow when things are working normally
What is the circle of willis and its purpose?
A continuous structure that wraps around where arteries connect to anatomy–provides a pathway that will increase likelihood of collateral circulation in the brain if there is a problem in one of the arteries
What happens if there is a blockage in one of the arteries in the circle of willis?
If one artery if blocked then the blood should have another pathway to take to get to tissue that needs to be perfused
What is the name of the artery formed by the merging of both vertebral arteries?
Basilar Artery
At what point on the brain surface do the vertebral arteries merge to become the basilar artery?
Inferior to the pons
Where does the basilar artery feed into the circle of willis?
Posterior midline
What are the 3 large cerebral arteries?
Posterior cerebral artery
Middle cerebral artery
anterior cerebral artery
Where is the posterior cerebral artery located?
stems of basilar artery on the back of circle of willis
What part of the brain is perfused by posterior cerebral artery?
Back and far lateral brain perfusion
What is the largest cerebral artery?
Middle cerebral artery
What part of the brain is perfused by the middle cerebral artery?
majority of lateral and middle part of the brain
Where are the anterior cerebral arteries?
front of brain
What area of the brain does the anterior cerebral artery perfuse?
front and medial parts of the frontal lobe primarily
Name the sections of the anterior cerebral artery:
Post-communicating part of cerebral artery (A2)
Pre-communicating part of cerebral artery (A1)
The small artery that connects the two anterior cerebral arteries:
Anterior communicating artery
What is it important to have anterior communicating artery in the circle of willis?
Its the only way to have left to right cross talk in the front of the circles of willis
allows for anterior cerebral arteries to communicate
What name is given to the internal carotid arteries once they become a part of the circle of willis?
Name changes to middle cerebral artery
Name the sections of the posterior cerebral artery:
Post communicating posterior cerebral artery (P2)
Pre communicating posterior cerebral artery (P1)
What is the structure that connects posterior cerebral arteries to middle cerebral arteries?
POsterior communicating artery
What are the arteries for the cerebellum?
Superior cerebellar artery
Anterior inferior cerebellar artery
Posterior inferior cerebellar artery
Where is the superior inferior cerebellar artery?
Projects from top of basilar artery
Where is anterior inferior cerebellar artery?
middle portion–arises from basilar artery
Where is posterior inferior cerebellar artery?
Furthest back–arise from each of the vertebral arteries (below the pons)
Why are subarachnoid bleeds more difficult than other intracranial bleeds?
usually arterial- blood is infiltrating some of the neurons and glial cells in are of hemorrhage
hard to remove blood without injuring underlying structures
What causes subarachnoid bleeds?
Genetics/lifestyle
alcoholism: BVs are thin and dont handle abuse very well. Or if person has HTN long periods of HTN make aneurysm more prone to burst
What is the top byproduct of metabolism that is involved in regulation of brain blood flow?
CO2
What is the correlation with CO2 and brain blood flow?
CO2 is produced by metabolism
The more CO2 we produce the higher the brain blood flow
How does increase CO2 cause increased blood flow to brain?
Local areas of the brain that have high activity are producing lots of CO2
CO2 moves into BVs surrounding that tissue and causes vasodilation
What is brain/blood flow autoregulation?
System that can maintain constant brain blood flow under changing conditions
How can the body gage how much perfusion it needs to the brain?
CO2 levels
We need as much perfusion as it takes to wipe out the CO2 that is being produced
once we get that done then blood flow will not increase any further
What drives blood flow?
systemic blood pressure
If there is an increase in systemic BP in a healthy person, what would happen to cerebral blood flow?
brain blood flow would not change (autoregulation is working)
How does the brain adjust to prevent over perfusion?
increases vascular resistance (vasoconstriction)
If feed vessels in the circle of willis have higher than normal pressure what will happen?
The vessels will constrict to limit any over perfusion that might come from increased BP
How does the brain prevent under perfusion during low BP?
brain blood vessels must relax to help maintain normal amounts of blood flow (dilation)
A: External carotid artery
B: Common carotid artery
C: Vertebral artery
What type of relationship would we see between brain blood flow and BP if autoregulation was not present?
linear
increase blood flow with increase bp
decrease blood flow with decrease BP
What would be a potential issue from unregulated cerebral over perfusion?
Risk of blowing up any aneurysm in the brain
A: Anterior communicating artery
B: Pre-communicating anterior cerebral artery (A1)
C: Post-communicating posterior cerebral artery (P2)
D: Pre-communicating posterior cerebral artery
E: Vertebral artery
F: Basilar artery
G: Posterior communicating artery
H: Middle cerebral artery
I: Post-communicating anterior cerebral artery (A2)
What would happen with unregulated cerebral under perfusion?
cell death
What is the BP range that cerebral blood flow autoregulation functions best at?
50-150
Why does autoregulation fail when outside allocated BP range?
If BP is lower (below 50) the bvs really cant dilate any further
if they cant relax any more then there will be further drop in BP causing a decrease in blood flow
What does LLA represent?
Lower limit of autoregulation (50)
What does ULA stand for?
Upper limit of autoregulation (150)
What happens to autoregulation in a patient with chronically elevated blood pressure?
Autoregulation adapts and shift new normal limits to higher values
What is a physical adaptation to chronic HTN?
Atherosclerosis: blood vessel harden up then they can can try to clamp down and prevent hyper perfusion
BVs can clamp down better but wont dilate very well
How does atherosclerosis in the brain occur?
It is a biproduct of HTN but also an adaptation to prevent over perfusion
How can autoregulation relate to patients overall health?
Autoregulation is used to gage health of cerebral circulation
Ability of vessel to dilate is related to cardiovascular health
In a healthy person, How does brain blood flow overcome blood clot of ischemia?
Vascular beds are capable of solving problems by opening up collateral circulation–if a vessel is clogged there other open vessels in the area should relax and help increase perfusion to affected area
If a patient has atherosclerosis from HTN what would happen in regards to cerebral blood flow if they had an ischemic stroke?
Blood vessels dont relax
They will have a much larger area of injury since the BVs dont relax and create collateral flow
How can we check vascular health?
Look at the blood vessels ability to dilate
Do we have collateral blood flood in the brain if we are healthy?
Yes-we have collateral brain flow all through life
we wouldnt notice any difference since the brain is finding ways to perfuse the tissue
What happens to cerebral blood flow in a patient with uncontrolled diabetes or hypertension?
Blood vessels do not have ability to dilate–which is why these patients have more serious diseases or strokes then you would otherwise
What are some drugs that alter autoregulation?
Volatile anesthetics–take some of the autoregulation offline
not a flat line with normal autoregulation, more of a slope
How is impaired autoregulation depicted in a graph representing pressure and blood flow relation?
The steeper the slope–the more autoregulation is affected by drug
What determines whether a motor neuron is turned on or not?
amount of stimulus it gets in the anterior horn
What happens once the action potential reaches the end of the neuron?
Slow voltage gated calcium channels open (P-type calcium channel)
When do P-type calcium channels open?
when an action potential is sensed/ in response to depolarization and allows Ca2+ into motor neuron
What happens once Ca2+ enters into motor neuron?
Storage vesicles move to cell wall and excrete neurotransmitter
What is another name for the acetylcholine storage vesicles?
VP-1 storage vesicles
VP-2 storage vesicles
What does VP stand for?
Vesicular Pool
Where is the different between VP-1 vs VP-2 vesicles?
VP-1: not ready to go yet (May be away from cell wall or not full of neurotransmitter yet)
VP-2: Storage vesicles are ready to go (ready to be activated by Ca2+ and secrete neurotransmitter to NMJ)
Which acetylcholine vesicles are there more of?
Lots of VP-1
smaller number of VP-2 that are ready to go
What happens when Ca2+ comes into cell after action potential?
Ca2+ causes vesicles to move to cell wall–fuse with it and empty contents into NMJ
What shuts of vesicles from fusing and dumping neurotransmitter into NMJ?
Ca2+ pumps: take Ca2+ that moved in from P-type calcium channel and removes it from neuron
Need ATP–very fast process
What happens to the vesicles when calcium is pumped out of the neuron?
removing calcium gets acetylcholine vesicles to stop fusing and emptying neurotransmitter
What helps reset a neuron?
Na/K ATPase
Voltage gated K+ channels: open when action potential passes through to help reset cell
Ca2+ sensitive K+ channels: K+ channel in motor neuron that is Ca2+ dependent K+ channel
What do acetylcholine receptors on skeletal muscles look like?
function a cylinders
2 binding sites for aCH–when both occupied the channel opens
Where are the nAch receptors on skeletal muscles located?
Located on target cell at the synapse–close to motor neuron
How many receptors are there at each NMJ?
millions of nAch receptors at each NMJ–concentrated area at this area of the motor neuron
What is end plate potential?
Depolarization that is happening in the muscle d/t nAch receptors opening up
end plate potential is the initial stimulus and then an action potential follows
Does end plate potential always lead to action potential?
end plate potential in health muscles always leads to action potential–will always open fast Na+ channels
When does end plate potential turn into action potential?
When voltage gated Na+ channels are opened
Where are voltage gated sodium channels located in skeletal muscle?
fast Na+ channels are located right next to nAch receptors–when these are open the action potential can spread down the length of skeletal muscle
What are action potentials mediated by?
Voltage gates Na+ channels
What is the approximate bare minimum of nAch receptors that need to be activated for an end plate potential?
500,000 activated receptors–not an issue because we have vast excess receptors and neurotransmitter than we actually need
What happens after voltage gated Na+ channels open on skeletal muscle?
muscle contraction with the spread of action potential down the skeletal muscle
What are skeletal muscles important for besides muscle contraction?
Important to keep body temp up
What do anesthetics do to skeletal muscles?
Takes them “off line”
Volatile anesthetics tend to reduce amount of muscle activity
What is the largest container within the body?
Skeletal muscles
lots of internal volume
What is associated with every skeletal muscle?
A motor neuron
How many motor neurons per skeletal muscle cell?
Vast majority of skeletal muscles have cells that are innervated my just one motor neuron
some muscles in the body are innervated by more than one motor neuron
On average, how many motor neurons control each skeletal muscle cell?
one motor neuron
What is an example of muscles in the body that are innervated by more than one motor neuron?
Ocular muscle in the eye socket are controlled by more than one motor neuron
How can motor neuron cell bodies be excited?
Descending spinal pathways
Reflex Arcs
How can an reflex arc elicit a muscle contraction?
Sensory pathway feeds into reflex system
strong pain signal coming into the cord–reflex arc can get involved
strong pain signal might elicit a muscle to contract to withdraw from pain
What is a fiber?
Term for cell in skeletal muscles
How are fibers in muscles arranged?
Fibers are arranged in groups within the muscle itself
What are the contractile elements of the skeletal muscles and how are they arranged?
Actin and myosin
arranged in tubelike structures
What does the prefix Sarco- denote?
muscle
What is the sarcoplasmic reticulum?
Specialized ER in skeletal muscles where calcium is stored
If a skeletal muscle needs calcium to contract, where does the calcium come from?
usually from internal stores in the SR
What happens to calcium in the skeletal muscle after muscle has contracted?
It gets quickly tucked back into SR through calcium pumps
What is the function of the transverse tubules (T-tubules)?
Perpendicular pathway (infolding) that allows action potential to move deep into the muscle cell
makes sure deep parts of muscle cell are activated
What happens when calcium is liberated in the skeletal muscle?
Drives actin and myosin cross-bridge cycling–muscle contraction
What physical change happens to muscle fibers when they contracted?
Muscle fiber shortens with contraction
How big is the NMJ in relation to size of skeletal muscle?
NMJ is a small area compared to size of skeletal muscle
Each spot where motor neuron innervates skeletal muscle has one neuromuscular junction
How many neuromuscular junctions are there in each skeletal muscle?
Probably tons
Every fiber has different NMJ associated with it
What causes skeletal muscles cells to look cross-hatched or zebra like pattern?
Actin and Myosin filaments
How does the muscle get needed energy?
There are lots of mitochondria in the muscles close to the neuromuscular junction
What would be the result in the target cell if there is large release of acetylcholine from the motor neuron?
Skeletal muscle would have lots of depolarization and should follow through with action potential (in healthy tissue)
What are clefts?
Infoldings at the NMJ on the skeletal muscle
What is the difference between primary and secondary clefts?
Primary Clefts: just one infolding
Secondary Clefts: more than one infolding
Are there Acetylcholine receptors located throughout the clefts in the post synaptic terminal?
acetylcholine receptors are toward the surface of the clefts–at the beginning part to keep receptors closer to neuron
Where is the primary location of voltage gated Na+ channels on skeletal muscles?
Concentrated on inside the clefts but also continue down the length of the skeletal muscle
What is the enzyme that breaks down acetylcholine and what components is it broken down into?
acetylcholinesterase enzyme–breaks acetylcholine down into acetyl (acetate) and choline
What is the purpose of acetylcholinesterase?
limits the length of depolarization from contact with the motor neuron
helps shut target down to reset things for another stimulus from motor neuron
Where is acetylcholinesterase produced and stored?
produced by skeletal muscles
it is fastened to skeletal muscle itself (parks at NMJ)
What enzymatic reaction occurs with the action of acetylcholinesterase?
Hydrolysis
What happens to the broken down components of acetylcholine?
No longer has an effect on the receptors on skeletal muscles
so its recycled by the motor neuron
Where is choline produced?
Motor neuron–specific enzymes that assemble acetylcholine
What myelinates motor neurons?
Schwann cells
Where are schwann cells in motor neurons located?
At the terminal end of motor neurons–manage the myelination of the motor neuron all the way back to spinal cord
How many nACh-Rs receptors at typical NMJ?
5 million
How many nACh-Rs are activated in a typical synaptic response?
500,000
What precent of nACh-Rs open in response to acetylcholine during a typical response?
10%
What is the bare minimum acetylcholine release to maintain muscle contraction?
at least 1 million acetylcholine molecules
since receptor needs 2 bound to activate probably release closer to 2 million acetylcholine molecules
What can happen to acetylcholine when trying to cross NMJ?
Acetylcholinesterase breaks it down before it reaches the target
What type of response is elicited when nACh-receptor has one unoccupied binding site?
No response–channel remains closed/ inactive
How many subunits do nACh-Receptors have?
5 subunits
2 of 5 have acetylcholine binding sites
How do nACh-R antagonists block acetylcholine?
Bind to sites on nACh-r; only need to block one of the binding sites to block the channel
What is Curare?
Naturally occurring paralytic–most non depolarizing paralytics are modeled after
Old acetylcholine receptor antagonist
Biologic found in rainforests used to paralyze prey when hunting
What causes exocytosis during the process of a muscle contraction?
Exocytosis is mediated by calcium interacting with storage vesicles
What channels are primarily involved in generating a normal looking action potential in the skeletal muscle?
VG Na+ and VG K+
How do skeletal muscles know what to do when an action potential is being transmitted?
Voltage sensors (DHP receptors) in the cell wall that can detect action potentials
What occurs when DHP receptors sense an action potential come through?
DHP receptor open up calcium release channels in the SR
Where is the sarcoplasmic reticulum located?
SR is close to the cell wall and in proximity to the transverse tubules; also very close to voltage sensors (DHP)
What is DHP?
Dihydropyridine receptor–not a receptor but a voltage sensor
some calcium channel blockers are DHP calcium channel blockers
How do DHP receptors function in skeletal muscle?
DHP receptors are tethered to the door keeping calcium release channel closed
They facilitate release of calcium from the SR when an action potential is sensed
How do DHP receptors open door to SR?
A physical spring like attachment from receptor to SR door
action potential comes through and sensor tugs on calcium release channel to liberate calcium inside “pops the cork”
Where does majority of calcium that is used for muscle contraction come from?
Sarcoplasmic reticulum
a little calcium can come in through DHP voltage sensors
How are voltage gates Ca2+ channels and DHP voltage sensors different?
Voltage gated Ca2+ channels allow for large amount of calcium to enter compared to DHP voltage sensors which only have a small amount of calcium enter the cell
Where are the 2 places DHP voltage sensors are located?
Cell wall
Transverse Tubule
Sensors in both of these places have a physical attachment to calcium release channel in SR
What is another name for calcium release channels that are attached to DHP receptors?
Ryanodine Receptor (RyR)
Does not function as a receptor buts its reactive to a chemica
sensitive to a chemical called ryanodine–chemical will open channel
A patient has hypocalcemia and is displaying trousseaus sign. This is primarily due to the effects of hypocalcemia in:
A) The skeletal muscle
B) The brain
C) The motor neuron
D) The mitochondria
answer: C: hypocalcemia would cause neuron membrane potential to be depolarized increasing activity of neuron that increases activity of skeletal muscle
skeletal muscles can contract without needing outside calcium–because they have lots of calcium tucked away in the skeletal muscle
How does calcium get put back into SR in skeletal muscles?
SERCA (calcium pump): sarcoplasmic endoplasmic reticulum calcium ATPase
What type of transport is SERCA?
Primary active transport–burns ATP directly to put calcium into container it doesnt want to go into (expends energy to do so)
What is another term for intracellular fluid in skeletal muscle?
Sarcoplasm
How is choline transported from the synapse it is liberated in back to the motor neuron?
ATPase mediated pump (choline pump)
Choline sodium transporter–choline follows Na+ gradient
Where is acetate resynthesizes?
In the mitochondria in the neuron–lots of mitochondria in neuron and skeletal muscle (supply ATP for all ion transporters in neuron)
Where can choline be stored?
In cell wall as phosphatidylcholine
What are some examples of things that can go wrong in a motor neuron?
Myasthenia gravis and LEMS
What is myasthenia gravis?
Condition where the body develops antibodies to the nACh receptor
- these antibodies bind and destroy the receptor
What usually causes myasthenia gravis?
Inflammation or genetic anomaly to the thymus gland
What are some treatments for myasthenia gravis?
- remove the thymus gland
- plasmapheresis
- Stigmine drugs
How do stigmine drugs work?
- target the acetylcholinesterase enzymes
- inhibit the breakdown of acetylcholine will prolong activity at the NMJ and increase chances that nACh receptors will be activated
What is LEMS? (Lambert-eaton myasthenic syndrome)
- typically neoplastic
- body develops antibodies to P-type calcium channels
- this reduces the calcium coming into the cell and ACh isn’t released
What are some treatments for LEMS?
- plasmapheresis
- remove lung tumor
- potassium channel blockers
How do potassium channel blockers work and why are they dangerous?
They close VG potassium channels or prevent them from opening - results in depolarization
- longer depolarization of the MN allows for more time for calcium channels to be open
- they are dangerous because they are not specific for motor neurons, they also affect the potassium channels in the heart
What are some examples of potassium channel blockers?
- TEA: tetraethylammonium
- Diaminopyridine
- Amiodarone (fairly safe cause it sucks at it’s job)
How do NON-depolarizing muscle relaxants work?
They are receptor antagonists - prevents action potential from happening
- you only need to bind one out of two sites to cause paralysis
How do depolarizing muscle relaxants work?
Succinocholine = 2 acetylcholine are attached to each other
- it causes sustained depolarization by keeping nACh receptors open for an extended period of time
Why doesn’t acetylcholinesterase break down succinylcholine?
It normally breaks down the ester bonds in the native acetylcholine, with succinylcholine the 2 acetylcholine are super stuck together so the enzyme has a hard time getting in to break the ester bond
Why is there muscle twitching when giving succinylcholine?
Because the medication causes a depolarization and creates an action potential that causes a small contraction
What is an important side effect of giving succinylcholine?
Elevated potassium in the blood - Sodium is constantly coming in and makes the membrane potential more positive and it will push potassium out of the cell to try and make the cell more negative
- usually increases by .5
What category of drug is Succinylcholine? (more specific than paralytic)
nACh-receptor agonist
A) Anterior Atlanto-occipital ligament
B) Posterior tubercle
C) Intervertebral Disc
D) anterior longitudinal ligament
E) Posterior longitudinal ligament
F) External occipital protuberance
G) Dens
H) Posterior antlanto-occipital ligament
I) nuchal ligament
J) Ligamenta Flava
K) Vertebral arch
L) intervertebral foramen
M) spinous process
N) interspinous ligament
O) supraspinous ligament
