NERVOUS SYSTEM Flashcards
Neurons
-functional units of nervous system
-functions to transmit information
Cell body
-houses the nucleus and cytoplasm
-neuron control center
-receives graded potentials
Axon
-propagation of the action potential
Dendrite
-receives information
-transmits graded potentials toward the cell body
Synaptic knob
-location where a neuron is connected to another neuron or effector
Axon hillock
-receives graded potentials
-initiates the action potential
Synapse
-specialized junction where neurons connect and transmit signals to each other
-a single neuron can contain thousands of synapses
Synaptic cleft
-small gap between neurons where communication takes place
-separates the presynaptic ending and the postsynaptic cell
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
Neurofibril node
-gaps in myeline sheaths
Multipolar neurons
-multiple processes from cell body
-many dendrites and 1 axon
Bipolar neurons
-1 dendrite and I axon from cell body
Unipolar neurons
-single short process from cell body
Sensory (afferent) neurons
-convey action potentials (APs) into the CNS through cranial or spinal nerves
-most are unipolar
Motor (efferent) neurons
-convey APs away from the CNS to effectors in the periphery
-most are multipolar
Interneurons
-located within the CNS between sensory and motor neurons
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
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
Ligand-gated ion channels
-open when a neurotransmitter latches onto its receptor
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
