Ch 11 Functional Organization of Nervous Tissue Flashcards
Nervous system divisions?
CNS & PNS. PNS includes:
- Afferent (sensory) Nervous System
- Efferent (motor) nervous system include:
a. somatic motor (voluntary)
b. autonomic (involuntary) which includes:
i. sympathetic (fight or flight)
ii. parasympathetic (rest & digest)
iii. enteric (controls digestive)
cells of the nervous system
neurons and glial cells (neuroglia)
characteristics of neurons?
respond to a stimulus, produce & transmit electrochemical impulses, release chemical messages
which cells are more common in nervous system & by how much?
glial cells (make sure neurons keep working) ; 5X
functional unit of a neuron
Action Potential
parts of a neuron
soma= cell body dendrite= receive messages in neuron axon= carries impulses
part of an axon
axon hillock, trigger zone, collateral, presynaptic terminal, , axolemma (membrane of axon), axoplasm (cytoplasm of axon)
Axons in CNS are called? PNS?
CNS= tract
PNS=nerve
Dendrites in CNS are called? PNS?
CNS= nuclei PNS= ganglion
two types of neuronal transport
- axoplasmic flow: one direction; moves SOLUBLE compounds via rhythmic contractions; supply for growth, repair, renewal
- axonal transport: multidirectional; moves INSOLUBLE along microtubules
a. anterograde= away from soma
b. retrograde= towards soma
Functional classification of neurons
- sensory/afferent: brings info to brain
- motor/efferent: bring info to target organ
- association/interneuron: strictly within CNS; send into to brain; connects motor and sensory
structural classification of neurons
- (pseudo-) unipolar: sensory neurons
- Bipolar: retinal and olfactory neurons
- multipolar: motor neurons
Glial cells of the CNS
astrocytes, ependymal cells, microglia, oligodendrocytes
astrocytes
CNS; most common glial cell; blood brain barrier
ependymal cells
CNS; line ventricles and central canal
Specialized are the cerebrospinal fluid
microglia
CNS; specialized macrophages; respond to inflammation
oligodendrocytes
CNS; extensions insulate portions of several CNS axons= WHITE MATTER
GRAY MATTER= dendrites & soma
glial cells of the PNS
schwann cells (wrap entire cell around axon), satellite cells (provide support and nutrients)
unmyelinated axons are located where?
in folds of Schwann cells or oligodendrocytes
multiple sclerosis
autoimmune disease
schwann cells and oligodendrocyte extensions wrap around many times
myelin sheath
completion of myelin sheath development at what age?
1-2 years; why it is pointless to potty train before 2 years, bc myelination to urinary bladder is not complete
oligodendrocytes cont to produce 3 growth inhibiting proteins and astrocytes form glial scar that blocks regrowth when what?
when CNS axon is severed
When schwann cells stop producing growth inhibiting proteins, form regeneration tube
when PNS axon is severed
difference in change across a membrane
membrane potential
membrane potential is caused by?
presence of anions (neg. charge), membrane permeability, cation concentration gradients
What anion do we not like in our cells!?
Na; K+ is inside the cell, Na- is outside
unequal distribution of charges across plasma membrane
potenial difference
we let what ion move easiest
K+; it is more permeable
at what are electrical and diffusion forces equal and opposite?
equilibrium potential
describes voltage across cell membrane if only one ion could diffuse
Nernst Equation
membrane voltage of cell not producing impulses (sending messages)
resting membrane potential
at rest all cells have a ______ internal charge & ______ distribution of ions
negative & unequal
value of RMP
-70 mV
three types of membrane ion channels
leak channels: open all the time
voltage gated channels: respond to change in RMP
ligand gated channels: little molecules bond to open
which channels are closed at resting membrane potential?
voltage and ligand gated channels
potential difference between K+ and Na+ becomes smalls;
depolarization: influx of Na+
potential difference between K+ and Na+ becomes greater
hyperpolarization: taking (+) away from inside or letting (-) inside the cell
excitable cells (neurons and muscle fibers) discharge RMP to generate/conduct impulses
action potential
MP becomes more positive
depolarization
MP returns to RMP
repolarization
MP becomes more negative
hyperpolarization
threshold value
-55 mV
during depolarization: influx? at threshold, which channels open? what type of feedback loop? peaks at what value?
Na+ influx
voltage gated sodium channels
positive feedback
+30 mV
during repolarization: what happens to channels? what happens to ions? what type of feedback? value is back at?
VG Na+ channels inactivate, VG K+ channels open
K+ is driven outward
negative feedback
-70 mV (RMP)
during hyperpolarization:
what establishes RMP?
MP becomes _____ __________ than RMP
Na+/K+ pump (3 Na+ out, 2 K+ in) more negative (
unable to respond to stimulus?
refractory period
absolute refractory period?
ABSOLUTELY can’t respond a new stimulus in this section (hill looking part of graph)
relative refractory period?
hyper polarized can respond but with BIG STIMULUS; doesn’t happen often
APs are ___ __ _______
all or nothing
amplitude of APs remains constant
frequency-modulated
local potential not sufficient to initiate AP
subthreshold
not a good conductor
axon
ability of neuron to transmit charges through axoplasm (just enough Na+ to stimulate next channel)
cable properties
conduction in unmyelinated axons
also called?
depolarization in every single section along axon; one direction bc section before is in absolute refractory period
CONTINUOUS CONDUCTION
conduction in myelinated axons
also called?
AP regenerated only at nodes of ranvier (where VG Na+ channels are concentrated); speeds up propagation
SALTATORY CONDUCTION
functional connection between presynaptic neuron and post synaptic cell
synapse
axodendritic synapse?
axosomatic synapse?
axoaxonic synapse?
attach to dendrite
attach to cell body (soma)
attach–rarely
depolarization flows from presynaptic into postsynaptic cell through gap junctions; in syncytial tissues
electrical synapse; syncytial= muscles function as one unit
NT stored in synaptic vesicles and released into synaptic cleft
chemical synapse
results from changes in charge across membrane, graded, no threshold, no refractory period
local potentials
EPSP
excitatory postsynaptic potential: local depolarization occurs; stimulatory response; make membrane more (+)
IPSP
inhibitory postsynaptic potential: causes hyperpolarization; inhibitory response; add (-)
postsynaptic potenials summate what 2 ways?
spatial summation: impulses received from DIFFERENT SYNAPSES at the same time
temporal summation: multiple sigmas arrive in RAPID SUCCESSION at the same synapse
spatial and temporal summation occur simultaneously
total summation
excitatory neuron synapses on presynaptic neuron and increases the amt of NT released by releasing more excitatory NT
presynaptic facilitation (ENHANCE)
inhibitory neuron synapses of presynaptic neuron and decreases amt of NT released by releasing more inhibitory NT
presynaptic inhibition (REDUCE) EX: loss of dopamine? lose inhibition --- Parkinson's with uncontrollable tremors
inhibitory neuron synapses onto postsynaptic cell
postsynaptic inhibition: won’t completely stop the signal, just lessen it
types of synaptic pathways
convergent: synthesis of data in brain
divergent: important info transmitted to many parts of brain
oscillating circuits: memory and learning
different types of neurotransmitters
acetylcholine (ACh), acetylcholinesterase (AChE), monoamine NT, amino acid NT, polypeptide NT, lipid NT, gases NT
Receptors for ACh
cholinergic receptors–nicotinic–curare; ALWAYS EXCITATORY
muscarinic receptors–atropine(nightshade) ; EXCITATORY OR INHIBITORY
ex. or inhabit based on receptor it binds to
enzyme that breaks down ACh into acetic acid and choline
acetylcholinesterase
G protein couple receptors
serotonin: ex-tryptophan
catecholamines: alpha and beta adrenergic receptors and dopanergic recepetors
loss of dopamine
parkinsons
neurotransmitters are inactivated by
presynaptic reuptake and
- monoamine oxidase (MAO): breaks down all AA
- catechol-O-methyltransferase (COMT): breaks down JUST catecholine
glutamic acid and aspartic acid
AA NT ; major CNS excitatory
glycine
inhibitory-block channels; w/strychine (rat poison) can’t control voluntary mvmt
GABA
most common in brain
Huntingtons Disease
over time GABA receptors in brain degenerate (men mostly)
satiety following meals; released in gut when full
cholecystokinin (CCK)
natural painkiller NT
substance P, endorphins, enkephalins, dynorphin
similar to THC in marijuana
endocannabinoids
