The Nervous System Flashcards
2 types of neural cells
Neurons and Glia
The CNS consists of:
The brain and the spinal cord
What does the CNS do?
it receives, processes, stores and transfers information
The two subdivisions of the PNS
the sensory division and the motor division
the input neuron is called
the sensory neuron
the communication neuron is called
the interneuron
the output neuron is called
the motor neuron
what do glial cells provide?
support/glue
Neurons are cells specialized for…
communication
type of neuron specialized to respond to a certain type of stimulus such as pressure or light
sensory neuron
type of neuron that transmits impulses away from the CNs
motor neuron
how many neurons are in the human nervous system?
85 billion
All neurons consist of what parts
a cell body, one or more dendrites and an axon
the main body of a neuron
the cell body
where is the nucleus located in neurons?
the cell body
slender extensions of the cell body that receive information from other neurons
dendrites
the long, slender tube of cell membrane containing a small amount of cytoplasm, a part of a neuron:
the axon
axons of sensory neurons originate from a …
dendrite
axons from an interneuron and motor neuron originate from
the point of union with the cell body called the axon hillock
at the other end of axons, axon branches into slender extensions called
axon terminals
axon terminals end in small rounded tips called
axon bulbs
types of cells that provide physical support and protection to neurons and help maintain healthy concentrations of important chemicals in the fluid surrounding them
glial cells
what do neuroglial cells not generate?
impulses
type of cell in brain and spinal cord that act as the first and main form of active immune defense in the CNS
Microglia
the garbage collecting glial cell is called
macrophage
the generic term for cells in the CNS which are neither neurons, nor microglia
macroglia
the most abundant type of macroglia
astrocytes
the name astrocyte is because of
the shape of a star
two major functions of astrocytes
neuron support and component of blood brain barrier
3 types of macroglia
atrocytes, oligodendrocytes and schwann cells
where are oligodendrocytes ?
wrapped around axons in the CNS
2 functions of oligodendrocytes
create myelin sheath and assist in conduction in CNS only
what do shwann cells provide?
myelination to the PNS only
What is myelination?
the forming of a myelin sheath around a nerve to allow nerve impulses to move more quickly
4 components of neurons
- Dendrites
- Soma/Cell Bosy
- Axon
- Synaptic bouton
the input component of a neuron is
the dendrites
the integrating component of a neuron is
the soma/cell body
the conducting component of the neuron is the
axon
the output component of the neuron is the
synaptic bouton
the chemical-electrical signal from one neuron to a target is called
action potentials
the sudden reversal of the voltage difference across the membrane is called
action potential
when sodium-potassium pumps go through a cycle, the effect is a removal of what?
one osmotic particle and a positive charge
the charge of the cell cytoplasm is what compared to the interstitial fluid?
slightly negative
the difference in voltage across the cell membrane is called
membrane potential
the tails of phospholipid molecules have what relation to water?
hydrophobic
the resting potential of a neuron is
~-70mV
The sodium potassium pump actively transports how many sodium ions out of the cell for 2 potassium ions?
3 Na+
which side of the membrane has a higher concentration of sodium?
the interstitial fluid
what is always leaking from the cell by passive diffusiion?
sodium
depolarizting the membrane means
moving the voltage closer to zero
making a membrane voltage more negative is called
hyperpolarization
the transient local changes in resting potential during impulses are called
graded potentials
when incoming signals from other neurons produce a bigger change in membrane potential than does one impulse alone
summation
if the sum of all graded potentials reaches the threshold, what happens?
an action potential
another word for action potential
electrical impulse
an action potential occurs as a sequence of three event:
depolarization, repolarization and reestablishment of the resting potential
concentraion differences lead to…
ion movement as a result of diffusion
ions will naturally move in what direction of a concentration gradient?
down
during depolarization of the membrane, what happens?
sodium moves into the axon
what happens during repolarizzation
potassium moves out of the axon
What happens during the reestablishment of restin potentialÉ
potassium channels close
the period when another action potential cannot be generated is called
the absolute refractory period
the presence of an absolute refractory period ensures
that action potentials move in one direction only
the absolute refractory period is followed by
a brief relative refractory period
During the relative refractory period, most of the potassium channels are
still open and the membrane is slightly hyperpolarized, making it harder to generate the next action potential
Between adjacent schwann cells on the axon are short, uninsulated gaps called
nodes of Ranvier
the mylein sheath provides 3 function
- Saves neuron energy
- Speeds up transmission of impulses
- helps regeneration of damaged axons in PNS
the leaping pattern for conduction along myelinated neurons is called
saltatory conduction
a 10 degree increate in temperature results in what for membranesÉ
double of conduction velocity
to convert information from neuron to target (muscle, cell, etc.) the action potential releases a chemical called
neurotransmitter
neurotransmitters cross a speciallized junction called
synapse
the entire signalling process from neuron to target cell is called
synaptic transmission
in the first step of synaptic transmission, an action potential arrives where and causes whatÉ
arrives at the axon bulb and causes calcium channels in presynaptic membrane to open
the presence of calcium during synaptic transmission causes what?
vesicles to fuse with presynaptic membrane and release their neurotransmitters into synaptic cleft
the neurtransmitters reach the postsynaptic membrane by
diffusion over the synaptic cleft
what is the synaptic cleft?
the space between the pre and post synaptic membranes
when molecules of the neurotransmitter bind to the postsynaptic membrane, what happens?
certain chemically gated channels such as that for sodium, open
When the channels on the postsynaptic membrane open, what happens?
sodium ions diffuse inward and produce graded depolarization of the postsynaptic membrane
graded potentials are caused by the opening of
chemically senstivive ion channels
