2A - intro to neuro Flashcards
neurons
a nerve cell; the basic building block of the nervous system
what are the two types of neurons
sensory and motor
neuroglia
non-excitable cells supporting, insulating, and nourishing neurons
-ex. Schwann cells
myelin sheath
a layer of fatty tissue segmentally encasing the fibres of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next
multipolar motor neuron
a neuron with a single axon and multiple dendrites; the most common type of neuron in the nervous system
pseudounipolar neuron
carry information from periphery to brain, whereas multipolar neurons carry information from brain to periphery
cell body
integrates all signals together, decides whether neuron will or will not send action potential
dendrites
collect information, synapse with other things
trigger zone
where action potential is generated. pieces of information are summed together. axon hillock
axon
the extension of a neuron, ending in branching terminal fibres, through which messages pass to other neurons or to muscles or glands
axon terminal
the endpoint of a neuron where synapses occur (with other neurons or with an end organ, such as muscle)
nodes of ranvier
gaps in the myelin sheath to which voltage-gated sodium channels are confined
peripheral process
sum the information collected by dendrites to decide whether there is an action potential worth sending or not
Sensory neurons
neurons that carry incoming information from the sensory receptors to the brain and spinal cord
motor neurons
neurons that carry outgoing information from the brain and spinal cord to the muscles and glands
ganglia
clusters of cell bodies in the PNS
oligodendrocyte
a type of glial cell that forms myelin in the central nervous system. Forms several myelin sheaths, and myelinated sections of several axons
Schwann cell
a type of glial cell that forms myelin in the peripheral nervous system. Forms one myelin sheath, and myelinated one section of an axon
what is multiple sclerosis
a chronic disease of the central nervous system marked by damage to the myelin sheath
- problems with oligodendrocytes, they can’t repair themselves
- secondary demyelination because many axons myelinated by a single oligodendrocyte
age range of onset of multiple sclerosis
20-50
how much does multiple sclerosis decrease life expectancy
7-14 years
what happens in the body when someone has multiple sclerosis
plaques occur in the brain and spinal cord causing tremor, weakness, incoordination, paresthesia, and disturbances in vision and speech
what is Guillain-Barre syndrome
inflammation of the myelin sheath of peripheral nerves
how is Guillain-barre syndrome characterized
rapidly worsening muscle weakness that may lead to temporary paralysis
recovery rate of Guillain-barre syndrome
80-90% recover within 2-4 weeks
progressive depolarization
the cause for electrical signal propagation (current)
resting membrane potential
-80mV
the outside of the cell is rich in which positively charged ion
sodium (Na+)
the inside of the cell is rich in this negatively charged ion
potassium (K)
conduction velocity
the speed at which an action potential is propagated along the length of an axon
what two factors does conduction velocity depend on?
- fibre diameter -> larger fibre diameter = faster conduction velocity
- myelination -> myelination means faster conduction velocity than unmyelinated
saltatory conduction
rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of ranvier to another, skipping the myelin sheathed regions of membrane
neuronal synapse
synapses that occur between two neurons, where transmission of nerve impulses occurs
presynaptic neuron
conducts impulses toward the synapse
postsynaptic neuron
transmits impulses away from the synapse
synaptic cleft
the narrow gap that separates the presynaptic neuron from the postsynaptic cell
step 1 of neuronal synapse
impulse arrives at end bulb
step 2 of neuronal synapse
voltage gated calcium (Ca2+) channels open, Ca2+ flows into cell
step 3 of neuronal synapse
increased concentration of Ca2+ causes neurotransmitter release
step 4 of neuronal synapse
Neurotransmitters cross synaptic cleft to bind receptors on postsynaptic membrane
step 5 of neuronal synapse
voltage gated channels open allowing Na+ to enter cell
step 6 of neuronal synapse
postsynaptic cell depolarizes