Musculoskeletal - 521 - (1-3) Dr. Fernandez Test Flashcards
What are the two sensory divisions of the Nervous System?
Visceral and Somatic
The autonomic nervous system is ALWAYS
Motor
The somatic motor division of the PNS innervates…
Skeletal Muscle
What percentage of interneurons comprise the human nervous system?
90%
How long can a neuron live?
Whole life
What are some exceptions to neurons being amitotic?
Olfactory neurons - some areas of the brain.
What are Nissl bodies?
They are dark areas associated with Ribosomes and thus a lot of protein production
Is a Schwann cell a glial cell?
Yes - specialized type
What histologically indicated an axon hillock?
No Nissl bodies.
What is another name for Nissl Bodies?
Chromatophilic substance
Are dendrites myelinated?
No
Can an axon be branched?
Yes
What is another name for the axon hillock?
Initial Segment
Which is smoother, the axon or the dendrites?
Axon
What is the most common type of neuron morphology?
Multipolar
Where are Bipolar neurons found?
Olfactory and Retina
Where are unipolar neurons found?
Dorsal root ganglia
What are the two main processes that form off a unipolar neuron?
Central process (goes to spinal cord) and peripheral process
A neuron that has only dendrites, in which the soma acts as an axon, is called…
Anaxonic
What percentage do glial cells make up in the CNS?
90% (50% by volume)
Name 4 kinds of CNS glia and 1 PNS glia.
Astrocyte, oligodendrocyte, microglia, ependymal
Schwann Cells
What is the apparatus that separates neurons from capillaries and what cell does it come from?
Perivascular feet.
Astrocyte (remember - a glial cell)
What cell covers axons in the CNS?
Oligodendrocytes
What cells are simple columnar ciliated?
Ependymal cells
Which glial cell is responsible for CNS immune activity?
Microglia
Do oligodendrocytes myelinate axons?
Negative ghost rider. They cover axons in the CNS
How many nerve fibers can an oligodendrocyte wrap?
How many can a Schwann cell wrap?
Many
One
Can an oligodendrocyte form a myelin sheath?
Yes - they can wrap multiple times
When developmentally does myelination stop?
adulthood
What is the lipid makeup of myelin?
80%
Are all axons myelinated?
No. But all are wrapped
What is the gap between Schwann cells called?
Node of Ranvier
If an axon is wrapped once it is…
If an axon is wrapped many times it is…
Unmyelinated
myelinated
Can myelination occur in the adult brain?
You better freakin hope so.
The brain does this continually to form new skills (especially motor) and acquire new memories
New myelination is KEY for learning and pathway reinforcement
Explain the difference between electrical potential and current.
potential - difference in charge
current - movement of said charge
What is the Na/K pump ratio?
3 Na OUT for 2 K IN
Why does nerve tissue have such a high use of ATP?
Na/K pumps run continuously and require one ATP per cycle
K leak channels accomplish what?
More negative charge outside cell
Na leak channel accomplish what?
Prevent hyperpolarization - not many of these
Why does the Axon Hillock have such high density of voltage gated channels?
Trigger zone for initiating action potential
500 per square micron
What additional voltage gated channel is present at the terminal bouton?
Ca++
What can initiate a local potential?
ligands (hormones or neurotransmitters)
light, temperature, mechanical disturbance
Local potentials are (3 things)…
Graded, Decremental, and Reversible
What are 2 types of postsynaptic potentials?
Excitatory (Na+ flows into cell)
Inhibitory (K+ leaves cell - hyperpolarization)
Do neurotransmitters have to be exclusively excitatory or inhibitory?
No. Depends on receptors.
ACh excitatory in muscle cells and inhibitory in Cardiac tissue.
Excitatory postsynaptic potentials make the membrane more…
positive
Inhibitory postsynaptic potentials make the membrane more…
negative (hyperpolarized)
What two things can directly cause hyperpolarization in an IPSP
Either Cl- flows in or K+ flows out
What is the difference between temporal and spatial summation?
Temporal - signal comes from single source (many times)
Spatial - many sources of local potentials cause action potential
A rapid spreading wave of depolarization and repolarization is called a….
Action Potential
EPSP’s take the membrane______ to threshold
IPSP’s take the membrane ______ to threshold
Closer to
Further From
Where is an important site of depolarization in the cell (after dendritic stimulis)?
Axon Hillock
What is the peak charge of depolariztion?
+35 mV
What ion depolarizes?
What ion repolarizes?
Na in
K out
What does the slow action of K+ channels cause?
Hyperpolarization
Is a nerve signal decrimental?
No - it’s like a fuse.
What is the Refractory Period?
Short time after action potential fires when it is resistant to stimulation
What is the Absolute refractory period
firing of potential
What is the Relative refractory period
Hyperpolarized stage
What two processes in the membrane are always on?
Na/K pump leakage channels (Na in / K out)
All healthy axons are covered by…
glial cells
The larger the diameter of the axon…
The faster the signal
What type of conduction occurs in myelinated axons?
Saltatory
How fast do signals travel in unmyelinated axons?
1-4 mph
How fast do signals travel in myelinated axons?
268 mph
What causes saltatory action in myelinated axons?
Current flow pushes Na to next node, which opens channels, etc.
The current flow along the inside of an axon in the area of a Schwann cell is…
Decremental
What is the disease in which myelin sheaths deteriorate, thought to be an immune disorder triggered by a virus?
Multiple Sclerosis
How many neurotransmitters are there?
Over 100 known
name 3 types of synapses:
axodendritic, axosomatic, axoaxonic
How many synapses are on a Purkinje cell?
100,000
Describe neurotransmitter direct/indirect effects.
Neurotransmitter can either bind directly to ion channel and change its shape (Direct)
or, indirect via second messengers
Terminal boutons have what additional voltage gated channels in their membrane?
Ca++
What does Ca++ generally do in the terminal bouton?
Activates protein kinases > phosphorylates proteins > exocytose vesicles
i.e. Ca > Calmodulin > kinase activated > phosphorylates synapsin (which triggers exocytosis of neurotransmitter)
How can repetitive firing change a synapse?
Increase number of receptors, increase membrane surface.
What are the 4 major categories of neurotransmitter?
ACh
Amino Acids
Biogenic Amines (AA’s with COOH removed)
Neuropeptides
What are two types of Biogenic Amines?
Catecholamines (epinepherine, dopamine)
Indolamines (serotonin, histamine)
Chains of 2-40 AA’s that have long lasting effects are called what?
Neuropoptides
What are some examples of neuropeptides?
opioids, somatostatin, substance P
What is a typical second messenger?
cAMP
Norepinepherine acts through what second messenger and is considered what type of synapse?
cAMP
Excitatory Adrenergic
What happens to most neurotransmitter after release?
Reuptake by the presynaptic neuron ending (bulb/bouton)
Describe an Inhibitory synapse?
GABA binds post-synapse and triggers Cl- channels.
This hyperpolarizes the cell
Which wast product induces sleepiness in the brain and is temporarily counteracted by caffeine?
Adenosine
caffeine binds but does not activate adenosine receptors
Where does the spinal cord begin and end?
Foramen Magnum to L1
Why does the spinal cord only go to L1?
Vertebral column grows faster than spinal cord.
What begins inferior to L1
Medullary cone
What is the structure from L2 to S5 called?
Cauda Equina
How many spinal nerves are there?
31 pairs
Where are spinal taps (and spinal anasthesia) usually done and why?
L3- L4. There is more leeway in the cauda equina, and the nerve fibers here are less likely to be pierced
What are spinal nerves that branch and merge called?
Plexus
What are the 3 Mater (Meninges) of the Spinal cord and brain?
Dura
Arachnoid
Pia
Where is an epidural given?
right outside the dura mater in fat/vasculature and anethetic diffuses from there
What is between the dura mater and the csf?
Arachnoid.
simple squamous w/ loose CT mesh
Where is the pia mater found?
On the surface of the spinal cord
Are the meninges sensitive to pain?
Extremely
while brain is not
CSF is found in the…
Subarachnoid space
What does the fat in the epidural space resemble?
Hypodermis
From superficial to deep, what are the layers of the meninges?
Dura - outside
Arachnoid - middle
then the CSF
Pia - layer around the spinal cord
What layer of the meninges is stretched/can be seen in spina bifida?
Dura mater
What matter is interior in the spinal cord and exterior in the brain?
Gray matter
Name the 3 horns of gray matter in the spinal cord?
Dorsal, ventral, lateral
The Dorsal Root is completely
Afferent/Sensory
The Ventral Root is completely
Efferent/Motor
Where do autonomic motor neurons arise from?
Lateral horn
How many pairs of Spinal nerves are there and what is the regional breakdown?
31 pairs 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal
What is the basal lamina and loose CT around Schwann cells called?
Endoneurium
What surrounds spinal nerve “fascicles”
Perineurium
What surrounds the entire spinal nerve?
Epineurium
Where are unipolar neurons found?
Dorsal Root ganglion
Where are PNS motor nerve cell bodies found?
Ventral or lateral horns of the spinal cord.
Where are the only places where there is one way traffic?
Roots
What 2 main branches do each spinal nerve have?
Dorsal ramus
Ventral ramus
What are the 3 classifications of nerve fibers and which one is unmyelinated?
A, B, and
C (unmyelinated)
What are the 4 divisions of A fibers and what do they do?
A- alpha (skeletal, proprioception)
A - beta (skin sensory)
A - gamma (motor efferent)
A - delta (sensory, dentin/pulp, fast pain, temp)
What fibers are autonomic preganglionic sympathetic?
B fibers
What fibers elicit dull slow pain?
C fibers
What general pattern does anesthetic follow in blocking of nerve fibers?
Thin ones blocked first
so A-alpha is the last one blocked
Why would a patient still feel pressure?
That sense is in the large A-alpha type fibers.
What is the sensation of pain called?
Nociception
What substances stimulate nociception upon injury?
serotonin, protaglandins, histamine, K+, and ATP, and bradykinin
Are there any nociceptors in the brain?
No
From whence comes visceral pain?
organs
What defines an analgesic?
Maintain consciousness
What is a general term for dysfunction in the PNS?
Neuropathy
How do local anasthetics work?
They inhibit the influx of Na+ ions across a membrane
What are the 3 components to a local anesthetic?
aromatic ring
ester or amide
amine
Ester based anesthetic example:
cocaine, chloroprocaine
Amide based anesthetic example:
lidocaine
Describe the general mechanism for a local anesthetic.
Base forms a salt to pass through epineurium and recombines in the cytoplasm to block Na+ channels
What is the fewest number of synapses a reflex can have?
one
Example of a monosynaptic reflex:
stretch receptor
Example of polysynaptic reflex:
withdraw reflex
When you almost fall asleep and jerk your head, what type of reflex is that?
monosynaptic
What type of receptor initiates the stretch reflex?
Muscle spindles inervated with type a-alpha sensory neurons
What type of inhibition is part of the stretch reflex?
reciprocal (so one signal comes in - two go out)
What intermediate step is present in the patellar reflex arc?
Interneuron initiates inhibitory response (relaxing opposing muscle)
What prevents muscles from contracting excessively?
The Golgi tendon reflex
What additional feature is there to a crossed extensor reflex?
Interneuron needs to cross spinal cord to initiate additional contraction contralateral to balance
What two muscle fibers (type/location) are in the flexor withdrawal/crossed extensor reflex?
Type A-delta ipsilateral
Type A-delta contralateral
The autonomic nervous system is entirely…
Motor
Where is the cell body in a presynaptic neuron of the autonomic nervous system?
CNS
Where is the cell body in a postsnynaptic neuron of the autonomic nervous system?
Ganglion
Are postganglionic nerve fibers myelinated?
no
What characteristics to post-ganglionic axons have in the sympathetic division of the ANS?
Long, unmyelinated, branched
Where do preganglionic neurons of the Sympathetic division of the ANS originate in the spinal cord?
T1-L2
Where do preganglionic neurons of the Parasympathetic division of the ANS originate in the spinal cord?
Either brainstem or S2-S4
Parasympathetic preganglionic axons are:
Long and myelinated
Parasympathetic postganglionic axons are:
Short and unmyelinated
What are the four cranial nerves involved in parasympathetic division?
III, VII, IX, and X
The somas of preganglionic sympathetic neurons are in the:
Lateral Horn of the gray matter in T1-L2
How to remember Sympathetic pre and post ganglionic fiber lengths?
Think chain ganglia. Right next to spinal cord so unmyelinated post fiber is long
What are ganglia outside the Chain ganglia for Sympathetic division?
Collateral (aka prevertebral)
What two Rami connect the spinal nerve to the sympathetic chain ganglia?
White and Gray Rami
Where do Splanchnic nerves go?
Carry preganglionic sympathetic fibers to collateral (prevertebral) ganglia.
What fiber type are postgangionic?
C fibers (unmyelinated)
Where are 3 places sympathetic collateral ganglia innervate?
celiac, superior/inferior mesenteric)
Adrenal Medulla cells can be considered…
postganglionic sympathetic neurons
What class of molecule is epinepherine/norepinepherine?
catecholamines
T/F
The ganglionic fiber innervating the adrenal medulla has no synapse prior.
True
Where are parasympathetic ganglia generally located?
Close to or within the target organ.
What nervous system controls the digestive tract?
Enteric.
What neurotransmitter does the parasympathetic nervous system use?
ACh - the entire system is cholinergic - both pre and post ganglionic neurons
What neurotransmitters does the sympathetic nervous system use?
Both cholinergic and andrenergic
What do most post sympathetic neurons release as neurotransmitter?
norepinepherine (andrenergic)
What sympathetic postganglionic neurons are cholinergic?
Sweat glands, blood vessels,
The sympathetic adrenal innervation releases what transmitter at the medullary synapse?
ACh
What two cholinergic receptors are there in the ANS?
Nicotinc - always stimulatory
Muscarinic - stimulatory/inhibitory
What two andrenergic receptors are there in the ANS?
Alpha - mostly stimulatory
Beta - excitatory / inhibitory (depends on subtype)
Beta-1 adrenergic receptor does what to the heart?
Stimulates
hence beta blockers
Beta-2 andrenergic receptor does what?
Relaxes bronchial smooth muscle
What are some examples of singular (sympathetic) innervation?
Erector pili, adrenal medulla, some sweat glands
What is sympathetic tone?
firing frequency results in single-innervated sympathetic system.
