NERVOUS SYSTEM Flashcards by Adin Clark

Neurons

-functional units of nervous system
-functions to transmit information

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Cell body

-houses the nucleus and cytoplasm
-neuron control center
-receives graded potentials

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Axon

-propagation of the action potential

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Dendrite

-receives information
-transmits graded potentials toward the cell body

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Synaptic knob

-location where a neuron is connected to another neuron or effector

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Axon hillock

-receives graded potentials
-initiates the action potential

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Synapse

-specialized junction where neurons connect and transmit signals to each other
-a single neuron can contain thousands of synapses

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Synaptic cleft

-small gap between neurons where communication takes place
-separates the presynaptic ending and the postsynaptic cell

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Myelin

-insulating layer of fatty substances and protein that surrounds nerves
-enables electrical impulses t travel quickly
functions include:
-speeds up communication in the brain
-water balance
-cognitive function: helps neurons respond to signals involved in memory formation
and other cognitive functions

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Neurofibril node

-gaps in myeline sheaths

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Multipolar neurons

-multiple processes from cell body
-many dendrites and 1 axon

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Bipolar neurons

-1 dendrite and I axon from cell body

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Unipolar neurons

-single short process from cell body

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Sensory (afferent) neurons

-convey action potentials (APs) into the CNS through cranial or spinal nerves
-most are unipolar

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Motor (efferent) neurons

-convey APs away from the CNS to effectors in the periphery
-most are multipolar

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Interneurons

-located within the CNS between sensory and motor neurons

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Resting membrane potential

-difference in charge inside and outside of the cell
-voltage measured across the plasma membrane
-set up by leak channels
-Na/k pump
-voltage difference from inside and outside the cell at rest due to the RMP is -70mV

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Electrochemical gradient

-when ion channels are open, they allow specific ions to move across the plasma membrane
-movement of ions depends on both the chemical gradient (concentration gradient) and the electrical gradient (electro chemical gradient)
-ions move form high concentration to low concentration=> chemical
-cations (+) move to negatively charged areas and anions (-) move to positively charged areas=> electrical

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Ligand-gated ion channels

-open when a neurotransmitter latches onto its receptor

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Mechanically gated ion channels

-open in response to mechanical deformation

Voltage-gated ion channels

-open in response to change in the transmembrane electrical potential

Graded potentials

-communication
-established on the receptive segment by opening chemically gated channels
-spreads for a short distance
-can vary in magnitude and direction
-can be added up resulting in a larger or smaller graded potential (summation)
-dendrites and cell body is the only places it can be generated
-can change the membrane potential

Depolarizing graded potentials

-membrane potential gets more positive
-also called post-synaptic potential (EPSP)

Hyper-polarization graded potential

-when the membrane potential gets more negative
-farther away from the threshold value
-also called inhibitory post-synaptic potentials (IPSP)

Action potentials

-communication -electrical signal travels the length of the axon -always the same (all or non) -if a neuron receives a threshold stimulus, an AP is produces and spreads down the axon of the neuron -graded potentials depolarize the neuron from -70mV to threshold (-55mV)

Depolarizing phase

-Na+ channels open -cell becomes more positive -graded potentials above the threshold causes a series of events: -voltage gated Na+ channels open -Na+ rushes into the cell -inside of cell more positive -membrane potential reaches +30 mV -depolarization

Repolarizing phase

-K+ channels open -cell returns to negative RMP -Na+ channels close -K+ voltage gated channels open -K+ moves out of the cell -cell returns to a more negative state until RMP of -70mV is restored -repolarization

After-hyperpolarization phase

-K+ channels remain open -causes hyperpolarization -membrane potential becomes even more negative - -90mV -once K+ channels close the membrane potential returns to resting levels

Absolute refractory period

-period during which a cell cannot generate another AP -occurs due to Na+ channels inactivation -must first return to resting state

Relative refractory period

-period where a second action potential can be initiated but requires larger stimulus -due to K+ channels being open and causing hyperpolarization

Neurotransmitter

-CNS and PNS both have excitatory and inhibitory neurotransmitters -acetylcholine (Ach) -common neurotransmitter -released by the PNS and CNS neurons -ACH is excitatory at the NMJ but inhibitory at other synapses -many amino acids can act as neurotransmitters -glutamate -released by nearly all excitatory neurons in the brain -GABA -inhibitory transmitter for 1/3 of all brain synapses Which can cause: -Excitatory postsynaptic potential (EPSP) -Inhibitory postsynaptic potential (IPSP)

Excitatory postsynaptic potential (EPSP)

-membrane potential becomes more positive

Inhibitory postsynaptic potential (IPSP)

-when membrane potential gets more negative -farther away from the threshold value

Neuroglia

-support and maintain neuronal function -greatly outnumber the neurons -non-excitable cells

Astrocytes

-helps form BBB -maintain the chemical environment -Ca2+ and K+

Oligodendrocytes

-produce myelin in the CNS

Microglia

-participate in phagocytosis

Ependymal cells

-form and circulates the CSF

Satellite cells

-support cells in the PNS -regulates ions and nutrients

Neurolemmocytes (Schwann cells)

-produce myelin in the PNS

Central Nervous system

-CNS consists of the brain and spinal cord

Peripheral nervous system

-PNS consists of all nervous tissue outside the CNS

Somatic NS

-SNS -consists of: -somatic sensory (afferent) neurons -stimuli from special senses, skin and proprioceptors -somatic motor (efferent) neurons -transmit signal to skeletal muscles -voluntary -effectors are the skeletal muscles -interneurons

Autonomic NS

-ANS -consists of: -sensory neurons -convey information from receptors in visceral orans to CNS -motor neurons under involuntary control -transmit signals to smooth and cardiac muscles and glands -consists of two branches- sympathetic and parasympathetic

Enteric NS

-ENS -the operation of the “brain to the gut” -controls the function of the GI tract -can operate independently from the CNS

Be able to draw a neuron and label all parts

Be able to draw a synapse and label all components

Be able to draw the graph of membrane potential over time for an action potential, and label the phases