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What is included in the CNS
Brain and spinal cord
Primary function of the CNS
Control and integration
What structures are included in the PNS
Cranial nerves and spinal nerves
What is the primary function of the peripheral nervous system
communication; it connects CNS to receptors, glands, etc.
What are the cell types in the nervous system
neurons and neuroglia
function of neurons
conduct electrical signals; basic cell or nervous system,
function of neuroglia
majority of all nerve tissues; supports neurons
where is the action potential generated on a neuron
the axon hillock
axonal transport
transporting things down the axon
what is the function of myelin
speed up signal transmission
All axons in the PNS, whether myelinated or unmyelinated, are surrounded by:
a continuous living sheath of Schwann cells
afferent neurons send signals:
into the CNS
Efferent neurons send signals
out of the CNS into the PNS
efferent and afferent neurons are part of the
PNS
interneurons are part of the
CNS
function of astrocytes
regulate the external environment of the neurons in the CNS
microglia function
migrate throughout the environment and help remove foreign substances —> can phagocytose foreign material and degenerative material
function of ependymal cells
epithelial cells that line the ventricles of the CNS; help support the cavity in which we house the brain and spinal cord; help control the composition of the fluid located in the CNS
can CNS axons regenerate
generally no
can PNS neurons regenerate
yes
what facilitates the regeneration of axons in the PNS
regeneration tube formed by Schwann cells that release chemicals calling other cells to help repair and regenerate
Schwann cells _NS
PNS; myelin-sheath former
Oligodendroytes _NS
CNS; myelin sheath former
at rest, neurons are relatively permeable to ___ ions
K+
at rest, neurons are relatively impermeable to ____ ions
Na+
depolarization
less negative than resting membrane potential
repolarization
membrane returning to the polarized resting potential
hyperpolarization
even more negative than the resting membrane potential
what happens during the depolarization of an action potential
voltage sensitive Na+ channels open as the membrane depolarizes —> when threshold is reached, more Na+ channels open
what happens during the peak of an action potential
Na+ channels become inactivated; Voltage gated K+ channels open
what happens during repolarization of an action potential
K+ leaves the neuron down the concentration gradient through the open K+ channels
What happens after hyperpolarization
K+ is still slowly leaving, and the cell returns to resting membrane potential
how are differences in stimulus intensity detected?
by the frequency of action potential generation
action potential refractory period description
due to INACTIVATED Na+ channels; if you apply a second stim. during that time, on that patch of neuron, no second action potential will be generated unless the membrane potential returns to almost zero
what is the relative refractory period due to
continued outward diffusion of K+; overshoot; need a strong stimulus to depolarize during this period
crossing the synapse sequence
action potential reaches the end of the axon terminals —> this causes gated calcium channels on the pre-synaptic cell to open —> calcium flows into the cell —> this causes the exocytosis of vesicles containing neurotransmitters —> neurotransmitters bind to the post synaptic cell —> gated sodium channels open on the post synaptic cell —> induces a synaptic potential in the postynaptic cell
what are the two types of synaptic potential
EPSP and IPSP
EPSP
excitatory post synaptic potential; results in depolarization of the post-synaptic membrane; if these signals are strong enough, an action potential occurs
IPSP
inhibitory post synaptic potential; postsynaptic membrane hyperpolarizes; opens Cl- channel, hyperpolarizing the cell
common neurotransmitters
acetylcholine
GABA
Glutamate
Glycine
Norepinephrine and epinephrine
what type of neurotransmitter is ACH
excitatory
what type of neurotransmitter is GABA
inhibitory
what type of neurotransmitter is Glutamate
excitatory
what type of neurotransmitter is Glycine
inhibitory
what type of neutrotransmitters are norepinephrine and epinephrine
inhibitory/excitatory; just depends on the tissue
how do neurotransmitters act on postsynaptic cells
through controlling ion channels
ACh uses what type of receptor to open K+ channels
g-protein coupled channels
Norepinephrine uses what kind of receptors
G-coupled proteins that use cAMP as a secondary messenger
what is the function of acetylcholinesterase (AChE)
breaks ACh down into component parts, which are then taken back into the presynaptic cell for reuse
convergence
many presynaptic neurons converge onto one post-synaptic neuron
divergence
many post synaptic neurons diverge from one pre-synaptic neuron
Temporal summation explanation
signals occur more frequently —> theshold is reached
spatial summation
more axons are sending signals to the post-synaptic neuron