Test 2: CNS/PNS PART 1 Flashcards
Toward the midline
Medial
Away from the midline
Lateral
Proximal and distal need a reference point.
If midline is reference point, then elbow is _______ to the fingers on the hand.
The elbow is _______ to the shoulder.
Elbow is proximal to the fingers
Elbow is distal to the shoulder.
Towards the head
Superior/cephalic
Away from the head
Inferior or caudal
The CNS is composed of what?
Brain and spinal cord.
The components of the CNS are enclosed/protected in boney structures. What are they?
Brain: skull
SC: vertebral column
PNS is composed of what
Nerves and ganglia
How many pairs of cranial nerves in the PNS? Where is their origin?
12 pairs of cranial nerves
Origin is in various parts of the brain
How many pair of spinal nerves?
Where is their origin?
31 pair of spinal nerves
Origin is various spinal segments
Cluster of nerve cell bodies and their associated dendrites
Ganglia
The PNS is further subdivided into what two nervous systems
Afferent (sensory)
Efferent
Conducts impulses towards the CNS
Afferent sensory nervous system
Conducting impulses away from the CNS
Efferent PNS
Efferent is subdivided into what 2 things
Somatic motor
Autonomic
Conducts impulses away from CNS towards the skeletal muscle fibers to bring about contraction
Efferent somatic motor PNS
The efferent somatic motor system is under conscious control. TRUE/FALSE.
TRUE
This system is not under conscious control, such as the bladder, heart, lungs etc. innervates tissue other than skeletal muscle fibers
Autonomic nervous system
Sympathetic and parasympathetic
What type of information do afferent pathways carry?
Sensory information
Afferent/efferent pathways have one single ______.
Neuron
Autonomic pathways have _____ neuron(s) in their pathways
TWO neurons
What are the two types of neurons in an autonomic efferent pathway? What is in between?
Preganglionic neuron–>
Autonomic ganglion–>
Postganglionic neuron–>
Syanapses on non-skeletal muscle tissue
The basic STRUCTURAL component of the nervous system
The Neuron (or nerve fiber or nerve cell)
Nerve cell body
Soma
The endoplasmic reticulum of the neuron
Nissl bodies
The neuron includes multiple ribosomes, prominent Golgi apparatus, and multiple mitochondria. What do you think the primary fxn is?
Protein synthesis
To be later modified into NT’s
Structures that extend out from the nerve cell body
Dendrites
A neuron can have many dendrites, but never just one or zero. TRUE/FALSE?
FALSE
Neurons can have one, many or zero dendrites.
What is the purpose of dendrites
To conduct electrical impulses from a point of origin on dendritic membrane toward the nerve cell body
Dendrites have very few ________ which makes them poor conductors of APs
Very few voltage gated sodium channels
How do dendrites conduct impulses to the nerve cell body
Electrotonic conduction
The cytoplasm of the dendrites and the cytoplasm of the nerve cell body has high conc of ______
Electrolytes
What provides/favors for electrotonic conduction? How far down the nerve cell body is electrotonic conduction used?
The electrolytes in the cytoplasm and the large diameter of the nerve cell body.
All the way from the dendrites to the axon hillock
This allows for free flow of electrical impulse down the nerve cell body and favors electrotonic conduction.
Large diameter of the nerve cell body– less resistance.
Where impulses are summed up and where RMP moves to TP.
Axon hillock.
Axons have lots of ________ so they are very good conductors of AP
Voltage gated Na channels
What is the purpose of the axon
Conduct AP from the nerve cell body to the terminal portion of the axon.
Once depolarization happens at the axon, the AP is conducted unidirectionally. Why?
Very few v-g Na channels in the soma
This allows for one nerve cell/impulse to conduct an impulse and influence multiple target tissues
Collateral axons
Each collateral axon terminates where?
Telodendria which branch into a terminal buton or presynaptic cleft/presynaptic membrane
Terminates in a terminal buton, presynaptic cleft or presynaptic membrane
Each telodendria
When electrical impulse gets to terminal buton, there is release of _______
Neurotransmitter
Form the myelin sheaths around axons in the PNS
Schwann cells
Gaps between Schwann cells where axon is exposed and the only place that APs can occur along the axon
Nodes of ranvier
Three types of neuron
Multipolar
Bipolar
Unipolar or pseudounipolar
How many axons do neurons have?
ONE AXON ONLY FOR ALL NEURONS
These neurons have many dendrites, one axon, found in the brain, sc and PNS.
Example?
Multipolar neurons
Skeletal muscle fibers
Neurons with one dendrite, one axon, sensory afferent neurons.
Where are the only two places these are found?
Bipolar neurons
Found in the optic pathways and olefactory neurons
Where are multipolar neurons found in the optic pathway? Where do they terminate?
Rods and cones of the retina
Terminate in the primary visual cortex in the occipital lobe
Where would dendrites be in the olefactory pathway?
Where would it terminate?
In the nose
Terminate in the olefactory center
Have no true dendrites attached to the nerve cell body, have sensory receptors that bypass the nerve cell body.
Unipolar
Virtually all sensory neurons are what type of neuron?
Unipolar.
Cells that make up the nervous system
Neuroglia
Star shaped cells found in the brain
Astrocytes
Wrap around the capillaries in the brain– one component of the bbb.
Foot processes of the astrocytes.
2nd part of the bbb where capillary endothelial cells adjoin
Tight junction
Partially protects the brain from toxic substances
BBB
If you have a drug that you need to give a pt, but know it will not cross the bbb, what type of administration can you do to get it to the brain?
Injection into the subarachnoid space
Pro-drug will cross bbb and then be metabolized into the correct drug in the brain
Example of prodrug that we treat Parkinson’s with? How does it work?
L-dopa.
Crosses bbb, then metabolized to form dopamine, then dopamine bids with target cell receptors in corpus striatum
Highly invasive cancers of the astrocytes that can be very aggressive
Astrocytoma or gleoblastoma
Line the ventricles of the brain and the passageways from one ventricle to the next
Ependymal cells
Form the corroid plexuses
Nonciliated ependymal cells
Synthesize CSF from the plasma
Corroid plexuses made up of nonciliated ependymal cells
Move CSF through the ventricles and eventually to the subarachnoid space
Ciliated ependymal cells
Resident macrophages of the brain
Migroglia
Microglia phagocytose what?
Old brain cells
Bacteria
Cancer cells
Anything that looks abnormal
We are born with microglia which protect us from foreign objects, worn out neurons, tumors and cancers, they are part of our ____________ system.
Innate immune system
Form the myelin sheaths around axons in the CNS
Oligodendrocytes
Not all axons in the CNS are myelinated. TRUE/FALSE?
FALSE
All axons in the CNS are myelinated !
A single oligodendrocytes can form the myelin sheaths around multiple axons. TRUE/FALSE.
TRUE
Oligodendrocytes cover ___ mm of space on an axon, so need multiple to cover an axon.
1 mm
All axons are myelinated in the PNS. TRUE/FALSE.
FALSE
Not all axons are myelinated in the PNS.
AP moving from node of ranvier to node of ranvier etc… is called?
Soltatory conduction
How are AP conducted on an unmyelinated axon?
V-g Na channels must be opened along every single segment of the axon.. do not have nodes of ranvier
Most efficent/fastest way of conduction along an axon
Saltatory conduction
Type A nerve fibers are ALL myelinated. TRUE/FALSE.
TRUE.
--Type A α – Type A β – Type A γ – Type A δ What do the symbols mean?
- Type A α ALPHA
– Type A β BETA
– Type A γ GAMMA
– Type A δ DELTA
Type C fibers are all unmyelinated. TRUE/FALSE.
Which NS are they found in?
TRUE.
PNS bc they are all unmyelinated.
Diameter of unmyelinated axons ________ micrometers.
0.5-2.0 micrometers
Diameter of myelinated fibers _______ micrometers.
1-20 micrometers. So much thicker than unmyelinated.
The larger the diameter of the axon, the poorer a conductor with more resistance to flow. TRUE/FALSE.
FALSE.
The larger the diameter, the better conductor the axon, and the less resistance to flow.
Unmyelinated type C fibers can transmit conduction ______ m/sec.
0.5-2 m/sec
Myelinated type A fibers can transmit conduction ________m/sec.
6-120 m/sec
Transmit crude touch/pressure, tickle, slow/aching pain are sent through what type of fibers?
Type C fibers
Cold and warmth that will not damage your tissues transmitted by what fibers?
Type C
Prickling, acute, sharp, fast pain transmitted through?
Type A Delta fibers
Deep touch/pressure that could damage tissues
Type A delta and some gamma
High discrimination touch through what type of fibers?
Can recognize what is in your hands while eyes closed
Type A Beta and Gamma
Vibration fibers?
Type A beta and gamma
Hair receptors fibers?
Very important for who?
Type A beta and gamma
Lower animals
monitor the tension of muscle fibers and send proprioceptive information back to the brain.
What type of fibers?
Primary ending muscle spindles and the Golgi tendon bodies
Type A Alpha
Fastest type of conduction fibers?
Type A Alpha
The information that allows our brain to know where our body is in time and space so we can walk a straight line, perform coordinated movements etc..
Proprioceptive information
Skeletal muscle fibers innervated what what type of fibers?
Type A alpha— so we can respond to changes rapidly
Sympathetic fibers are what type of fibers?
Type C
Bundle of axons in the PNS. Provide a pathway for electrical impulses.
NERVE.
Peripheral nerves are mixed nerves meaning?
They can transmit different types of info
Bundles of axons
Fascicles
All the axons within a fascicle transmit the exact same type of information. TRUE/FALSE
TRUE.
If you severed a peripheral nerve you would only lose sensory nerves. TRUE/FALSE?
FALSE
You would lose sensory, skeletal muscle, autonomic etc bc peripheral nerves include all types of fibers.
Bundle of axons and their myelin sheaths in the CNS
Tracts
Tracts form the _____ matter and can be ascending or descending.
Tracts connect spinal cord to the ______. The connect the brain to the ______. And one part of the brain to ________.
Tracts form the white matter.
Connect spinal cord to brain; brain to the SC; and one part of brain to other parts of the brain.
Cluster of nerve cell bodies and their associated dendrites, and where axons synapse with those dentrites.
Gray matter.
Composes the outside of the brain and inner part of the SC.
Gray matter.
Composed of tracts. Composes the inner part of the brain and outer part of the SC,
White matter.
Cluster of gray matter positioned within the white matter, in the CNS.
Nucleus
Cluster of nerve cell bodies and their dendrites and where they synapse
Ganglion
Where axon terminates, NT is released into synaptic cleft. NT diffuses across synaptic cleft and binds with receptors of postsynaptic membrane to bring about cell response.
Synapse
How most NT are released
Calcium dependent exocytosis.
AP runs down presynaptic terminal and opens up what?
Voltage gated Ca channels
Ca moves with its gradient from _______ to ______ the axoplasm.
From outside to inside
Ca influx into the axoplasm leads to binding of presynaptic __________ to presynaptic membrane, and release of ______ into the synaptic cleft.
Binding of presynaptic vesicle to membrane— release of NT
NT released binds with _________ on the postsynaptic membrane to bring about response
Receptors on postsynaptic membrane
This could be another axon, dendrites of another neuron, target tissue/organs, skeletal muscle fibers, etc.
Post synaptic membrane.
Binds with original axon and decreases NT release
Inhibitory neuron
Will bring about more NT release and exaggerated response
Excitatory neuron
How is Ach released into the synaptic cleft?
Ca dependent exocytosis
Enzyme in the synaptic cleft that breaks down Ach.
What two substances is Ach broken down into?
Acetylcholinesterase
Acetic acid and choline
Diffuses to the blood to be metabolized by the liver.
Acetic acid (acetate)
This substance is taken back up into the presynaptic terminal and repackaged to make Ach again.
Choline
Drug we give that inactivates acetylcholinesterase
Neostigmine
MOA of neostigmine
Inactivates Ach-esterase, allows Ach to accumulate and stay longer to bring about exaggerated response (such as return of skeletal muscle fxn)
How is NE released into synaptic cleft
Ca dependent exocytosis
How is NE removed from the synaptic cleft?
Reuptake pump and most NE is repacked to be used again.
What NE is not repackaged is metabolized by what?
MAO (monoaminoxidase)
What would happen if we inhibited MAO?
More NE would be available to be repackaged/released and have exaggerated response on postsynaptic membranes
Was used as psych drug but no longer prevalent bc of severe CV effects and severe jitteriness.
MAOI’s
Any stimulus/event that causes POSTSYNAPTIC membrane to move closer to TP
Excitatory postsynaptic potential
Any event/stimulus that causes postsynaptic membrane to become more - or RMP farther from TP is ?
Inhibitory postsynaptic potential
Example of EPSP with NE
NE binding with Na channels– Na influx into the cell causes RMP to become less negative and RMP to approach TP. EXCITATORY.
Example of IPSP with NE
NE binding with receptors that opens Cl channels and K channels. Cl- moves into the cell and K+ moving out of cell– both make more - RMP, farther from TP. INHIBITORY.
Found at the lower motor neuron synapses at neuromuscular jxn– responsible for skeletal muscle contraction
Acetylcholine
Plays major role in autonomic nervous system and found at many CNS synapses.
Ach.
What are the type of receptors for Ach
Nicotinic (1&2)
Muscarinic
Collectively the cholinergic receptors
Very fast responding receptors; ligand gated ion channels with short duration (1-2 msec)
Where are they found?
Nicotinic 1: neuromuscular synapses
Nicotinic 2: autonomic ganglionic synapses
When we give a paralytic like roc or vec, what type of receptor does it bind to?
Nicotinic 1
G-protein couple receptors, longer duration of action (100-250 msec) (Ach)
Muscarinic receptors
What are the catecholamines?
Dopamine
NE
Epi
Where is NE found
Sympathetic post ganglionic neuron synapses with target organ synapses &
Many CNS synapses
Watch pathway in the CNS is NE frequently found?
Locus ceruleus pathways
Plays major role in coordinated skeletal muscle movement in relation to nigrostriatal pathway/tract
Dopamine in the CNS
Neurohormone synthesized and secreted from the adrenal medulla ONLY!!
EPI
Epi binds with same target organ receptors as __________ and intensifies its effects.
NE
The same common ancestor AA to all catecholamines
Tyrosine
Synthesis of epi from AA?
Tyrosine–> L-dopa–> dopamine –> NE –> EPI (only in the adrenal medulla is the enzyme to convert NE to epi!!!)
How are catecholamines released?
Ca dependent exocytosis
What type of receptors do epi and NE bind to
Adrenergic receptors:
Alpha 1&2
Beta 1&2
Dopamine binds with what receptors
Dopaminergic receptors:
D1: activates adenylyl cyclase
D2: inactivates…
Found throughout CNS, brainstem, and limbic system
Serotonin
Players a role in emotional responses to environment
Limbic system/ serotonin
Serotonin is synthesized by __________ and released by _________.
L-tryptophan
Ca dependent exocytosis
Almost always released with other NT, almost never by itself
Serotonin
Serotonin has at least 7 receptors and most all are EXCITATORY/INHIBITORY?
INHIBITORY
This is ALWAYS INHIBITORY (AA).
GABA (gamma aminobutyric acid)
How is GABA released
Ca dependent exocytosis
Receptors for GABA?
GABA-A
GABA-b
GABA receptor on the POSTsynaptic membrane that open up Cl- channels resulting in membrane hyperpolarization
GABA A
GABA receptor on the PREsynaptic membrane, decrease the release of NT.
GABA B
Two types of drugs that bind to gaba receptors that we give
Propofol
Midazolam
This is (AA) that is ALWAYS EXCITATORY.
Major NT for fast, acute, sharp pain.
Glutamate
What type of receptors does glutamate bind to?
NMDA
QA
KA
Is ketamine an NMDA agonist/antagonist?
Antagonist– blocks the receptor bc its excitatory if activated.
Major NT for the transmission of slow, long-term chronic pain.
Substance P
Receptors for Substance P
Neurokinin
What are the endogenous opioid peptides?
Endorphins
Enkephalins
Dynorphins
Where are endogenous opioids found and how are they released.
Many sites in CNS and ca dependent exocytosis
Receptors for endogenous opioids
Mu: endorphins
Kappa: dynorphins
Delta: enkephalins
All neuropeptides (endogenous op) are EXCITATORY/INHIBITORY.
INHIBITORY
These are very potent and may cause prolonged cell response, sometimes days, weeks or months.
Endogenous opioids/ neuropeptides
This is released along with a NT and either intensifies or decreased the effect the NT has on the postsynaptic membrane
Neuromodulator
What are the 3 types of summation?
Spatial
Temporal
Combined spacial and temporal
2 or more impulses occurring on different dendritic membranes simultaneously
Spatial summation
Impulses arriving over time at the same dendritic membrane
Temporal summation
With spatial summation, impulses must add up to get RMP to TP. If one impulse is inhibitory and the other is excitatory, what will happen at the axon hillock?
Nothing, they will cancel each other out.
With temporal summation, impulses must be HIGH/LOW magnitude and arrive QUICKLY/SLOWLY after one another to conduct an AP
High magnitude
Quickly follow each other
What happens at axon hillock with an action potential depends on what?
The net sum of spatial and. Temporal impulses
Basic FUNCTIONAL component of the nervous system
Reflex Arc
A reflex are is defined by ________ input, and _______ output. Or can be _______ input and _______ output.
Sensory input
Motor output
Sensory input
Autonomic output
One neuron that has an axon that synapses on multiple nerve cell bodies is what type of pathway
Divergent pathway
Multiple neurons and their axons synapse on a single neuron is what type of pathway
Convergent pathway
Allows brain to localize stimulus, analyze, and formulate a response to the stimulus in a reflex arc
Site of divergence of the sensory afferent neuron
Site of convergence example in a sensory-motor reflex arc
Where brain responds to stimulus and sensory divergent neuron synapse to determine motor response
Feedback into the nerve cell body that regulates output from the nerve cell; regulatory mechanism
Oscillating pathway
Oscillating pathways are characterized by what?
Periods of activity and periods of fatigue
Two examples of oscillating pathways?
Sleep wake cycle: when pathway active, we are awake, when not active, we sleep.
Respiratory cycle: when active, we inspire, when pathway fatigues, inspiration stops and we expire
When is a neuron unable to every repair it self?
When the nerve cell body is crushed or injured
Axons can repair themselves under what conditions?
Axons have to be closely approximated.
If axon is not approximated, what happens?
Muscle will atrophy and will have nerve injury
What event brings an end to depolarization and intiates repolarization?
Closure of v-g Na channels and about the same time opening of v-g K channels
Hyperkalemia _________ the cell so is closer to TP.
Hyperkalemia HYPERPOLARIZES the cell
Hypokalemia ________ the cell making it further from TP.
Hypokalemia HYPERPOLARIZES the cell
When we think about calcium , we think about changes in the __________ potential
Threshold potential
What occurs at RMP?
K leak channels
Na leak channels
Na-K pump
- charged proteins accumulating on membrane
What would the outcome be if glutamate and gaba bind simultaneously with their receptors on a postsynaptic membrane.
They would cancel each other out.
Outcome of glutamate binding with NMDA receptor would be EXCITATORY/INHIBITORY
EXCITATORY
