Neurons

Question 0

what type of charge do neurons carry?

Answer 0

relatively negative = -70mV

this is due to negatively charged protein cells and some Cl- ions

Question 1

What determines the electrical potential of a membrane

Answer 1

the movement of ions through the semi-permeable membranes

distribution of ions

Question 2

define non-gated channels

Answer 2

passively allow ions to cross

Question 3

types of gated-channels
what opens them
examples of each

Answer 3

Modality-gated - open in response to mechanical forces, temp, or chemicals
Ligand-gated - respond to NT’s; ex: NMJ
voltage-gated - respond to changes in electrical potential; ex: axon membrane

Question 4

axonal transport (orthograde axonal transport)

Answer 4

moves organelles and macromoleules (enzymes, protens) from cell body to axon terminals –> transported via microtubules

Question 5

anterograde axonal transport

types & what each carries

Answer 5

transport from the cell body to the terminal
Fast = moves macromolecules containing vesicles and mitochondria
Slow = carries structural and metabolic components

Question 6

retrograde axonal transport

Answer 6

transport from the terminal to the cell body
molecules like growth factors are transported back to the cell or recycled

pathogenically: rabies and tetanus are retrogradely transported

Question 7

pseudounipolar neurons
what’s the peripheral process do? central process?
what are their anatomical classifications?

Answer 7

found only in sensory ganglia of spinal nerves & somatosensory ganglia of cranial nerves

• peripheral process = conveys sensory info from somatic or visceral structures (goes with peripheral nerves)
• central process = courses with nerve root to convey sensory info into CNS (dorsal root ganglion)
• –they function together as a single axon - even though one is working as an axon and one as a dendrite

Question 8

multipolar neurons

Answer 8

neurons with a single axon and multiple dendritic processes

-most nerve cells are this

Question 9

bipolar neurons

Answer 9

round/oval perikaryon with singe process - usually axon + dendrite
found in special senses; i.e. retina, vestibular & cochlear ganglia (CN VIII), olfactory system

Question 10

unipolar neurons

Answer 10

single process, not common in humans

Question 11

are afferent and efferent synopsis for sensory/motor?

Answer 11

NO. afferent = towards; efferent = away.

general terms for these fibers

Question 12

where are interneurons located

Answer 12

all of interneuron must be in the CNS –> usually refers to the interneurons in the gray matter of the spinal cord

Question 13

define monosynaptic reflex arc

Answer 13

two neurons and one synapse

ex: muscle stretch reflex

Question 14

define resting potential
what do the ions do at this time
-relative concentration of each

Answer 14

when a neuron is not transmitting information & the inside is relatively more negative than the outside

K+ can easily diffuse in/out but Cl- & Na+ have trouble getting in –> more K+ in & more Na+ out

Question 15

define local potential

Answer 15

the initial change in membrane potential due to some stimulus –> only spreads a short distance
may or may not cause action potential
1. variable amplitude, 2. localized 3. travel short distances

Question 16

3 types of local (graded) potentials

Answer 16

1. synaptic potentials = potential changes in neurons
2. generator potentials (receptor potentials)= local potentials in sensory cells
3. end-plate potentials = synaptic potentials of muscle cells

Question 17

what is the threshold for an action potential

Answer 17

-55mV

Question 18

define the all or none principle

Answer 18

all action potentials are the same size = it either reaches it’s threshold and depolarizes or it doesn’t

Question 19

three events of an AP

Answer 19

1. rapid depolarization by Na+ in
2. decrease in Na+ as the channels close
3. Rapid repolarization by K+ influx –> hyperpolarization = refractory period

Question 20

2 ways to increase AP speed

Answer 20

1. increase the diameter of the axon
2. Mylein sheath –> myleinated internodes & unmyleinated nodes of Ranvier create saltatory conduction –> AP “jumps” from node to node

Question 21

What is peripheral neuropathy?

Answer 21

any pathologic change involving peripheral nerves –> usually involves disruption of the nerves’ mylein sheaths

Question 22

Guillain Barre Syndrome

Answer 22

PNS neuropathy; autoimmune disorder
acute inflammation and demyelination of PNA sensory & motor fibers caused by antibodies attacking the Schwann cells
–> decreased sensation & skeletal muscle paralysis

Question 23

Multiple Sclerosis

Answer 23

autoimmune disease
antibodies attack the oligodendrocytes of the CNS = patches of demylienation = “plaques” in the white matter
muscle weakness, lack of coordination, impaired vision, impaired sensation, slurred speech

Question 24

Why are nerve conduction studies administered?

Answer 24

to determine if the nerve transmission is slower than normal

Question 25

What is a compound action potential | 2 types

Answer 25

a measure of the combined electrical potential of a group of axons in a singe nerve compound motor action potential = CMAP compound sensory nerve action potential (SNAP)

Question 27

what are neuroglia (glia) cells? functions? types?

Answer 27

non-neural cells in CNS & PNA that support neurons by controlling the environment within in the CNS -shuttle nutrition from blood to neurons, remove waste products, maintain electrochemical surroundings. -Mitotic - esp. during trauma/disease CNS: astrocytes, oligodendrocytes, microglia, ependymal cells PNS: schwann cells, satellite cells

Question 27

what is the metabolic center of a neuron

Answer 27

the cell body - contains mitochondria, nuclues, nucleolus, nissl substance

Question 28

define astrocytes types what are their function

Answer 28

type of glia cell found in PNS & CNS protoplasmic = gray matter fibrous = white matter they cover the cells capillaries along with cell body, axons, dendrites & synapses where they play a role in metabolism of NT's like GABA

Question 29

what are Nissl bodies

Answer 29

large amounts of rough ER in the cell body of a neuron - there because a neuron creates a lot of protein

Question 30

what is chromatolysis | what does it indicate

Answer 30

loss of color of the nissil bodies due to damage of the neuron -- usually indicates potential neuron death

Question 31

what is a neurophil / where is it located

Answer 31

=dendrite and synapses located in the gray matter of the Nervous System

Question 32

what form do cell bodies take in the the CNS? (2); in the PNS?

Answer 32

laminae = sheets/layers OR ganglia in CNS | ganglia only in PNS

Question 33

what direction do dendrites conduct

Answer 33

towards the cell body

Question 34

what direction do axons conduct?

Answer 34

away from the cell body

Question 35

define axon collaterals | define axon hillock

Answer 35

branches off of axons | location in which axons arise

Question 36

define arborizing

Answer 36

axons branching into fine terminal branches

Question 37

alternate names for white matter in the CNS

Answer 37

tract, fascicle, lemniscus, bundle

Question 38

what gets myleinated

Answer 38

large diameter axons

Question 39

job of microfilaments in the neuron

Answer 39

important in anchoring receptor molecule at synapses and for movement of the advancing tip of growing axons

Question 40

tau's role in neurofibillary tangesq

Answer 40

it's dissociation from the microtubule forming filaments is what causes the cells to tangle

Question 41

astrocytes in injury

Answer 41

they proliferate & enlarge (as reactive astrocytes) & form glial scars via gliosis they are responsible for why the CNS has poor regenerative abilities They also fill the demyelinated spaces in the CNS during MS = MS plaques

Question 42

what are microglial cells

Answer 42

immune effector cells of the CNS - involved in inflammation | act as macrophages

Question 43

what are ependymal cells

Answer 43

cells that form the choroid plexus epithelium | =secretes CSF

Question 44

Most common brain tumors of CNS in order. | of PNS?

Answer 44

1. glioblastoma = multiple glia cells 2. astrocytomas = astrocytes 3. Oligodendrogliomas 4. ependymomas = from the ependymal cells (rare) PNS = vestibular schwannoma