L01: Neuroanatomy/Neuro Exam (Carrera) Flashcards
Nernst Potential
diffusion potential level across a membrane that exactly opposes the net diffusion of a particular ion through the membrane
- determined by the ratio of the concs. of an ion on the 2 sides of the membrane
- helps establish resting membrane potential
K/Na “leak” channels are most permeable to:
K+
membrane potential must be what to depolarize?
0
what happens during depolarization
- increase in Na permeability, influx of positive
- potential may approach 0 or greater
what happens during repolarization
- Na channels begin to close
- K channels open more
- re-establishment of RMP
Ca deficit –> Na channels
activates them with little increases in membrane potential, leading to a very excitable nerve (tetany)
action potential threshold is reached when:
Na ions entering the fiber >K+ leaving the fiber
AP propagation
AP elicited at any point on an excitable membrane exites adjacent portions of the membrane
Refractory period due to:
Na channels becoming inactivated
how is excitation inhibited?
high extracellular Ca (dec. permeability to Na)
local anesthetics to block Na channels
perikaryon
cell body of a neuron
myelin sheath composed of what in PNS
Schwann cells
larger diameter fiber has faster or slower conduction?
faster
how are postsynaptic receptors excited?
opening of Na channels
dec. conduction through Cl/K channels
how are postsynaptic receptors inhibited?
opening of Cl channels
inc. K+ out of the neuron
which NT excitatory
Ach (usually)
Where NE synthesized
adrenergic n. terminal
-reuptake into adrenergic endings, diffused away, or enzymatically destroyed
presynaptic inhibition
release of inhibitory substance (GABA) onto presynaptic fibrils
- cancels effect of Na influx
- occurs in many sensory pathways to minimize sideways spread
where do APs begin?
Axon initial segment (loaded with Na channels)
alkalosis inc./dec. excitability for synaptic transmission?
increases
end plate potential
local positive potential in the muscle fiber created by inlux of Na into m. fiber
sarcoplasm
fluid filling spaces b/w myofibrils in a m. fiber
sarcolemma
true cell membrane in muscle
myofibrils
make up muscle fiber; actin and myosin filaments
-myosin heads controlled by ATP-ase
what activates actin and myosin sliding?
Ca influx
transverse tubules
penetrate through muscle fibers to communicats APs deep into muscle
can APs be generated by stretch?
yes
which fibers secrete Ach?
cholinergic
which fibers secrete NE?
adrenergic
all preganglionic neurons are ____
cholinergic
Most parasympathetic postganglionic neurons are ___
cholinergic
most sympathetic postganglionic neurons are ____
adrenergic
where are muscarinic receptors found
on all effector cells stim. by postganglionic cholinergic neurons of sympathetic or PS systems
where are nicotinic receptors found
- found in autonomic ganglia at synapses b/w pre and postganglionic neurons of sympathtic and PS systems
- NMJ
NE excites mainly alpha/beta receptors
alpha
what detects m. stretch
muscle spindle
golgi tendon organs
- detect m. tension
- sensory
- locally inhibitory to a single muscle
alpha motor neuron fx
innervate skeletal m.
gamma motor neuron fx
- transmit impulses through smaller nerves
- controls m. tone
Renshaw cells
prevent neurons from firing inappropriately (inhibited in Strychnine poisoning)
Forebrain = ***
cerebrum (cerebral cortex, hippocampu, basal nuclei)
diencephalon (thalamus, hypothalamus)
Midbrain = ***
(mesencephalon)
cn3,4
rostral and caudal colliculi
Cerebellum = ***
cn5-12
motor tracts
proprioceptive tracts
Brainstem = ***
connection to cn8
unconscious proprioception
(inhibitory)
Ascending Reticular Activating System fx
receives sensory info from the spinal cord and cranial nerves. Projects, through thalamic relays, diffusely to the cerebral cortex, thus maintaining consciousness
superficial to deep on spinal cord: proprioceptive tracts –> motor tracts –> pain
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