Nervous System Flashcards
What is the function of a neuron?
Transmit electrical impulse and translate impulse into a chemical signal
What is another name for a neuron’s cell body?
Soma
What is another name for a neuron’s soma?
Cell body
Where is the nucleus of a neuron found?
Cell body / Soma
Where is the endoplasmic reticulum and ribosomes of the neuron found?
Cell body / Soma
What emanates directly from the cell body?
Dendrites
What do dendrites do?
Receive incoming messages from other cells
Where does a cell signal go from the dendrite?
Cell body to the axon hillock
What does the axon hillock do?
Integrates incoming signals and plays an important role in action potentials
What is the axon?
Long appendage from the cell body that terminates in close proximity to a target structure
What is myelin?
Fatty membrane covering mammalian nerve fibers (insulation to prevent loss of signals)
Does myelin increase or decrease the speed of conduction of an axon?
Increases
Where is myelin produced in the CNS?
Oligodendrocytes
Where is myelin produced in the PNS?
Schwann cells
What are nodes of Ranvier?
Small breaks in the myelin sheath that leads to exposed areas of axon membrane
Besides myelin, what increases the speed of a nerve impulse?
Nodes of Ranvier
What is another name for the nerve terminal?
Synaptic bouton
What is another name for the synaptic bouton?
Nerve terminal
Are neurons connected?
No
Synaptic cleft
Space between one nerve terminal and another nerve’s dendrites into which neurotransmitters are released
Synapse is composed of?
Nerve terminal
Synaptic Cleft
Postsynaptic membrane
What are ganglia?
Cell bodies of neurons of the same type
How many types of information does one tract carry?
One
What are the cell bodies of a neuron in a tract known as?
Nuclei
What is the function of glial cells?
Provide structure and support
What do astrocytes do?
Nourish neurons
Form the blood-brain barrier
What do ependymal cells do?
Line ventricles
Produce CSF
Shock absorber
What cells form the blood-brain barrier?
Astrocytes
What cells produce CSF?
Ependymal cells
What cells line the ventricles?
Ependymal cells
What do microglia do?
Pahgocytic cells that ingest and break down pathogens and waste in CNS
What cells are phagocytic in the CNS?
Microglia
Neuron resting membrane potential? Where do the negative ions lie?
-70 mV
Negative inside
Is there more potassium inside or outside the cell?
Inside (140mM to 4mM)
Potassium leak channels
Slow, favorable leak of potassium out of the cell
Equilibrium potential of potassium
Concentration gradient pulls K out of the cell but negative charge pulls the cation back in = no net movement
-90mV
Is there more sodium inside or outside the cell?
Outside (12mM to 145mM)
Sodium leak channels
Slow, favorable leak of sodium into the cell
Equilibrium potential of sodium
60mV
Na+/K+ ATPase
Continually pumps potassium into the cell and sodium out of the cell
Does excitatory input cause de- or hyper-polarization and what does that mean?
Depolarization - raises the membrane potential and causes an action potential
Does inhibitory input cause de- or hyper-polarization and what does that mean?
Hyperpolarization - lowers the membrane potential and lessens the chance of an action potential
What is the threshold for an action potential?
-55 to -40mV
What happens to the ions when the membrane reaches the threshold?
Migration of sodium into the cell due to electrochemical gradient leading to rapid depolarization
What happens to the ions during repolarization?
Potassium leaves the cell
Absolute refractory period
No amount of stimulation can cause another action potential to occur
Relative refractory period
Greater than normal stimulation is required to generate an action potential because the cell is more negative than usual
What is the functional purpose of the refractory period?
Information can only flow in one direction
How does length and cross-sectional area of the axon affect the speed of action potentials?
Increased length - higher resistance and slower conduction
Increased area - lower resistance and faster propagatiom
Does length or area contribute more to action potential speed?
Area
What does saltatory conduction mean?
Action potential signals hop from one node of Ranvier to another - ions can only move into and out of the cell at these nodes due to insulation caused by myelin
Effector
Name for the post-synaptic cell if it is a muscle or gland rather than another neuron
Differentiate between electrical and chemical transmission during an action potential
Electrical signals are passed down the length of an axon
Chemical (neurotransmitter) signals are used to pass the signal from one neuron to the next
What is the first chemical step of an action potential at the nerve terminal?
Voltage-gated ion channels open and cause an influx of calcium into the neuron
What does the increase in intracellular calcium during an action potential cause?
Fusion of membrane-bound vesicles with the membrane leading to exocytosis of the neurotransmitter
What are the three ways that neurotransmitters can be removed from the synaptic cleft and what is a classic example of each?
- Breakdown by an enzyme - acetylcholine
- Reuptake carriers bring the neurotransmitter back to the presynaptic neuron - serotonin, dopamine, norepi
- Simple diffusion out of the synaptic cleft - NO gas
Inactivation during an action potential
When the membrane potential reaches +35, the sodium gates close and potassium channels open
Monosynaptic reflex arc
Sensory neuron fires directly onto the motor neuron
Polysynaptic reflex arc
Sensory neuron fires onto motor neurons as well as interneurons that then fire onto motor neurons
Are motor neurons afferent or efferent?
Efferent
Are sensory neurons afferent or efferent?
Afferent
Are motor neurons presynaptic or post-synaptic?
Post
Are sensory neurons presynaptic or post-synaptic?
Pre
