neurons ch3 Flashcards
overall goal of nervous system is
enable organism, to move its body appropriately to succeed at 4 fours - feeding, fleeing, fighting and reproducing
uses predictions of what is going inside and outside the body to make predictions about and act accordingly
neurons communicate via __ and __ signals
chemical and electrical
neurons have same organelles as other cells, what makes them different
what makes them able to do this
they can transmit electrical signals fast over long distances - when they arrive at destination they trigger a specialized form of chem signaling
because of the proteins on their membranes
summarize the neurons 1st zones of importance
dendrite - branching extensions from cell body that collect info from lots of tiny chem signals they receive along their extent. collect info and pass it on to soma
summarize the neurons 2nd zones of importance
soma or cell body - key feature is Nucleus, control centre, integrates (sums up) signals coming in from the dendrites
summarize the neurons 3rd zones of importance
3 ways it differs from dendrite
axon - nerve fiber, reaches long distances, cable to conduct signals rapidly,
differs: only on axon, can be many branches of dendrites, axons remain constant length and dendrites are tapered, axons are a lot longer
summarize the neurons 4th zones of importance
axon terminals - axons brach into 10k terminals at end. have small swellings at each tip, which contain packages of chemicals that can be released into the space between cells
synapse is the gap between axon terminals and dendrites or somas of others cell, how does this differ in cns vs pns
synapse links to other neurons in Central NS
synapse links to other neurons, muslces, or glands in Peripheral NS
what are en passant synapses
although most synapses occur at axon terminals, they can also exist along axon itself - en passant synapses
4 critical functions of neuron
collect
integrate
conduct
output
what categories do we get when we classify neurons by function
Sensory - directly respond to signals from outside environment (light waves, sound, odour)
Motor - have direct output to muscles or glands - final step for signals to exit nervous system
Interneurons - not beginning or end, inbetween sensation of singal and action at other end. most neurons are this type
what roles do glial clells play in the nervous system
speed up signalling,
regulate concentrations of extracellular (outside cell) chemicals,
determine the extent to which networks of neurons can modify their connections
list 4 types of glial cells
Oligodendrocytes
Schwann Cells
Astrocyte
Microglia
what do Oligodendrocytes Glial cells do
found only where
large cells that wrap around axons (myelination) to speed signals. one oligodendrocytes can wrap axons of 50 diff neurons
only in Central NS
what do Schwann Cells Glial cells do
found only where
wrap around axons (myelination) to speed signals. can only fit around one axon unlike Oligodendrocytes
peripheral NS
what are the gaps between myelin sheaths called
nodes of ranvier
not all axons become myelinated - which do which don’t
subcortical (deep brain structures) and peripheral axons are myelinated
those in the cortex (outer layer of brain) often are not myelinated
neurotransmission
cells communications across small gulfs of space to other targets
neurotransmitters
the chemicals released from one cell to another to send a message by changing chemical concentration at target
space between pre and post synaptic cells is called?
how does its small space help
synaptic cleft
small only 20-50 nanometers
this small distance allowed the [ ] of neurotransmitters to rise and decay rapidly
in presynaptic cell - where are neurotransmitters packaged before release
small spherical packages called Synaptic Vesicles
how is released of presynaptic chemicals done
synaptic vesicles (contain neurotransmitters) fuse with the outer membrane causing molecules to spill out into the cleft
what are the 4 categories of Neurotransmitters?
not a neurotransmitter - but what else can carry signals, how do they enter post cell. why do we say they work in opposite way. they are called ________ transmitters
Acetylcholine - used in frog experiment - stands in category of its own. excitatory - causes muscle contractions
Monoamines - large molecules: dopamine, epinephrine, norepinephrine, serotnin and melatonin
Amino Acids - smaller, building blocks of proteins,
Peptides - short strings of amino acids,
gasses like nitric-oxide and carbon monoxide which diffuse directly into cell membrane. opposite because they are produced in dendrites 1 cell and cross synapse backwards to axons of post cell. so they are called Retrograde Transmitters
most neurosn will release one peptide neurotransmitter in addition to 1 or a few smaller enurotreansmitters - what is the rule of order here?
release smaller neurotransmitters first and only start to release the larger peptide neurotransmitters after they have ben stimulated repeatedly
when chemicals are relased into synapse from pre cell how do they enter post cell
bind to Receptors: specialized proteins in the membrane of post synaptic cell
when reached the post cell there are two receptor types which let in transmitters transmit a signal to another cell: they __ or __
Ionotropic Receptors: located n an ion channel. quick response, cause a direct flow of Ions into or out of the cell
Metabotropic Receptors: not on ion channels, own unit in membrane, when nt binds to it, iniates more indirect changes inside the cell by a cascade of signals eventually leading to ion channel opening, longer process, they stay open longer