Midterm 1 - Nerve Cell Function/Synaptic Transmission Flashcards
what does the sensory system consist of
sensory nerve fibers from sensory cells
what kind of system is the sensory system
afferent
where is info generated
central nervous system
what does the CNS consist of
brain and spinal cord
what is the peripheral nervous system
info conveyors
what is the somatic motor sytem
specialized system that focuses on skeletal muscle
what does the somatic motor system consist of
motor nerve fibers to skeletal muscles
what kind of system is the somatic motor system
efferent
what two systems are a part of the autonomic system
sympathetic nervous system
parasympathetic nervous system
what does the autonomic system consist of
motor nerve fibers to glands, the heart, and smooth musculature
when is the sympathetic nervous system activated
during critical situations
when is the parasympathetic nervous system activated
at rest
what type of system is the autonomic system
efferent
what are the 2 types of cells that compose nervous tissue
neurons
glial cells
what are the nerve cells able to transmit info
neurons
what are neutrons composed of
cell body and processes (axons and dendrites)
what does the axon do
move info away from cell body
what does the dendrite do
moves info towards cell body
what does the cell body do
integrates in- and outgoing info
what can neurons be categorized based on
the number of processes
what are the 3 categories
multipolar
pseudounipolar
bipolar
where are multipolar neurons mainly found
CNS
where are pseudounipolar neurons mainly found
PNS
where are bipolar neurons mainly found
sensory organs
what can neurons be classified by
function
what type of neuron is from PNS to CNS
sensory (afferent)
what type of neuron is from CNS to muscles and glands
motor (efferent)
what type of neuron relay info between neurons within the CNS
interneurons (associations)
what are specialized “receptors”
transducers
what do transducers do
convert stimuli to signal
what are glial cells
non-neuronal cells
are neurons or glial cells more abundant and by how much
glial cells - 10x more abundant
examples of glial cells
oligodendrocytes
astrocytes
ependymal cells
microglia
why do we need glial cells
there is no structural support or access to blood without them
what do glial cells provide
structural support to nervous tissue
what do glial cells participate in
myelin formation
what type of glial cells participate in myelin formation
oligodendrocytes
what do glial cells secrete
glutamate
what does the secreted glutamate do
modulate excitatory level of neurons
what type of glial cell modulates excitatory levels of neurons
astrocytes
what to microglia possess
phagocytic activity
what is special about glial cells
they contact both blood and neurons
what do glial cells do due to it being the contact between neurons and blood
transport of nutrients
what do neurons not store
glucose
oxygen
what does grey matter correspond to
cell bodies
what does white matter correspond to
bundles of nueron processes
what gives white matter the white appearance
myelin sheaths
what are nerves
bundles of axons
where do nerves run
to or from the CNS
what are ganglia
clusters cell bodies of sensory neurons - outside of the CNS
where are cell bodies of motor nerves located
in the CNS
what is myelin
white lipid around nerve fibers
what is the white lipid of myelin called
sphingomyelin
do all fibers have myelin
no, only white matter
what are the interruptions in myelin called
nodes of Ranvier
what is the distance between nodes of Ranvier
every 1-2 mm
what does every cell body possess
resting membrane potential
what does the resting membrane potential result from
a difference in charge across the cell membrane (between cytosol and extracellular fluid)
what is the charge difference in resting membrane potential
the inside of the membrane is negative RELATIVE to outside
what does the difference in absolute value between cell types depend on
amount of charges
ion channels
thickness of membrane
what is the average RMP in nerve cells
-70 to -90 mV
is resting membrane potential maintained
always
where is the charge electro neutral
intra- and extracellular compartments
what charges occur in cytosol
negative charges carried by large organic molecules are attracted to the membrane by the positive charges on the outside
what maintains the resting membrane potential
selective permeability
Na+/K+ pump
Large anions trapped on inner surface of membrane
what is the ratio of Na+ and K+ to maintain RMP
3 Na+ out
2 K+ in
what is the selective permeability to maintain RMP
passive based on diffusion - passive ion leakage through channels (concentration gradient)
are anions of negative or positive charge
negative
why does the RMP not achieve equilibrium
the Na+ / K+ pump
is the resting membrane permeable to K+
yes
is the resting membrane permeable to Na+, Cl-, and Ca2+
barely - positive charges accumulate outside
what does Na+ go against
concentration gradient and against membrane polarity
how much energy do ion pumps require
lots: 40% of ATP availability
what are excitable cells
cells that can generate electrical impulses (APs)
what do excitable cells need in order to generate action potential
stimulation
what is the refractory period
the time when neurons cannot be restimulated - until RMP is restored
types of gated channels
voltage-gated
ligand-gated
ion-gated
what are ligand gated channels
binding cites for neurotransmitters
what is each channel composed of
several subunits
what does each channel have various degrees of
specificity
what rule do nerve cells follow
all-or-none rule
what does the all-or-none rule involve
when threshold is met, an AP is generated
does the amplitude of AP change per cells
no, it is fixed for that cell
what is intensity of a AP encoded by
the frequency of APs, not the amplitude
how does an AP work
depolarization and repolarization processes propagate along cell membrane
why is the change in potential needed
to reach threshold on the nearby micro domain to trigger opening of gated channels
what is the difference between APs in myelinated or unmyelinated axons
myelinated - only occurs at the nodes of Ranvier
are myelinated or unmyelinated fibers faster at transmitting connection
myelinated
what is saltatory conduction
the current jumping from one node to another due to myelin preventing ion leakage
what makes the speed of connection so much faster in myelinated axon
velocity increases as less membrane is affected = less energy required to transport ions
what does nerve velocity (AP speed) depend on
dissipation of current
factors that effect dissipation of current
thickness of myelin
diameter of the fiber
what diameter of the fiber leads to faster AP
thicker = faster
what is synaptic transmission
continuity of signal between neurons or between a neuron and a target cell
example of target cells involved in synaptic transmission
skeletal muscle (neuromuscular synapse)
what is the electric insulator
cell membrane made of phospholipids
what is the synaptic gap/cleft
the gap between pre and post synaptic cell membranes
gap junction
rarely, direct continuity in electric impulse
what are neuronal synapses in vertebrates
predominantly chemical synapses
what does electrical activity to get across synaptic cleft
neurotransmitter
what are neurotransmitters
molecules able to transmit info from a neuron
what do neurotransmitters do
convert electrical signal (AP) into a chemical signal
what are neurotransmitters classified on
their molecular size and composition
2 classifications of neurotransmitters
small molecules
neuropeptides (3-40 AA)
where are small molecule neurotransmitters synthesized
nerve terminals by specific enzymes at level of cell body
what are small molecule neurotransmitters
amino acid derivatives ; biogenic amines
where are neuropeptides synthesized
cell body
where are neuropeptides packaged
secretory vesicles
where are neuropeptides transported
site of release
where is postsynaptic folding common
in neuromuscular synapse
where is postsynaptic folding not common
in interneurons
what does postsynaptic folding do
increases surface
what is the neuromuscular synapse transmitter
Acetylcholine
can receptors get desensitized
yes - when continuously stimulated
what does 1 neuron = in the case of neuromuscular synapse
1 neuron = AP = muscle cell depolarization
in neuron-neuron synapse, what can 1 neuron receive
impulse from multiple other neurons
what are the 2 types of synapses in neuron-neuron synapse
excitatory
inhibitory
does 1 impulse always lead to a response in neuron-neuron synapse
no - needs to reach threshold
what is excitatory synapse
depolarization = entry of Na+
what is inhibitory synapse
hyperpolarization = entry of Cl- and/or outflow of K+
does inhibitory synapse raise membrane potential
no
