4.5 Nervous Sys1 Flashcards
What divisions are in the afferent PNS?
Afferent=sensory
Somatic Receptors/Neurons
Visceral Receptors/Neurons
Special Sensory Receptors/Neurons
What are the divisions of the efferent PNS?
Efferent=motor Somatic Neurons/Effectors Autonomic Neurons/Effectors Sympathetic Parasympethetic
What are the major structures of a neuron?
Dendrites Cell Body Axon Axon Hillock Axon Terminal Myelin Sheath
What is the function of dendrites in neurons?
Stimulated by
environmental changes
or the activities of
other cells
What is a nerve? tract?
A bundle of axon fibers is a nerve in the peripheral nervous system, a tract in the central nervous system.
What are the coverings of nerves?
Epineurium: surrounds entire nerve (from CNS regions)
Perineurium: surrounds fascicles (bundles of axons from groups of neurons)
Endoneurium: surrounds myelinated and unmyelinated axons from single neurons
What is the function of schwann cells?
Surround all axons in PNS; responsible for myelination of peripheral axons; participate in repair process after injury
What is the function of oligodendrocytes?
Myelinate CNS
axons; provide
structural
framework
What is the function of astrocytes?
Maintain blood-brain barrier; provide structural support; regulate ion, nutrient, and dissolved-gas concentra- tions; absorb and recycle neurotransmitters; form scar tissue after injury
What is the function of microglia
Remove cell
debris, wastes,
and pathogens
by phagocytosis
What is the function of ependymal cells?
Line ventricles (brain) and central canal (spinal cord); assist in producing, circulating, and monitoring cerebrospinal fluid
What is ALS?
Amyotropic Lateral Sclerosis (ALS, or “Lou Gherig’s disease)
loss of upper and lower motor neurons that control voluntary muscles, muscle weakness, muscle atrophy and paralysis ultimately to respiratory muscle failure, sensation and cognitive ability intact
What is MS?
inflammation and damage to myelin and other CNS cells, remissions (healing) and exacerbations fluctuate, sensory and motor symptoms
What is Guillian-barre?
spinal, cranial and peripheral nerve damage likely by macrophage attack on myelin, axon damage
What is the resting membrane potential in mV? How is it maintained?
Resting membrane potential: -70mV
When measure resting potential, is measured with reference to the outside-– measure inside vs outside
How do we get a negative resting potential?
Lots of Na+ OUTSIDE cell vs Little K+ inside cell… the surplus of positive ions outside cell makes the cell appear/feel negative
The biggest contributor to resting membrane potential is the difference between Na+/K+ (charged protein help a little, but mostly Na/K)
Sodium/potassium pump is constantly working to keep/set the membrane potential
What happens when Na and K channels open, respectively?
sodium channels open excitation
Na+ ions move in depolarization
potassium channels open inhibition
K+ ions move out hyperpolarization
What are EPSP? IPSP? Significance?
EPSP- excitatory post synaptic potential
IPSP- Inhibitory post synaptic potential – by opening Cl- or K+ channel Makes cell more -
Where do neurons have graded potentials? Dendrites, receptors, cell bodies
If enough EPSP, the add up at axon hillock to create action potential
What are the voltage changes with the graded potentials?
EPSP; depolarizing, excitatory (+1 to +5mV from rest)
IPSP; hyperpolarizing, inhibitory (-1 to -5mV from rest
What are the steps of an action potential?
REST Depolarization to Threshold Threshold & Rapid depolarization Inactivation of Sodium & Activation of Potassium Hyperpolarization back to REST
What is the threshold voltage? What happens here?
-60mV
Na gates open
Rapid depolarization
What are temporal and spacial summation. Why important?
A single input is rarely enough to reach threshold
Two ways that graded potentials add up inside the cell (summation)
Temporal summation: graded potentials build up in time, by increasing frequency of a single input
Spatial summation: graded potentials build up in space by receiving multiple inputs in the same location
What happens during rapid depolarization? Voltage change?
-60mV to +30mV
Na gates open, Na in
K gates closed, K stays in
What happens when Vm = +30mV?
Na channel “plug” closes, stopping depolarization
K+ channels open, K+ comes in, begin depolarization
What is the absolute refractory period?
NO effect of increasing stimulation
the neuron is at its max open sodium channels, no further stimulation will change it
the sodium channels are then inactivated and cannot respond further
What is the relative refractory period?
effect of increased stimulation only if VERY strong
sodium channels reset, but the neuron is hyperpolarizing and it will be more difficult to activate it.
What is the order of operations in releasing a neuro-transmitter?
1- electric action potential arrives at synapse, depolarizing it
2- Ca++ ions enter synapse, trigger release of neurotransmitter by exocytosis
3- Neurotransmitter released to synaptic cleft
What are direct vs indirect neurotransmitters?
Direct: open ion channels
Indirect: lead to protein cascades within the neuron that open ion channels
What are excitatory vs inhibitory neurotransmitters?
Excitatory: ion channel opening leads to increase in membrane potential toward threshold (more action potentials, more “excitable”)
example: glutamate, increases Vm when opens Ca2+ channels
Inhibitory: ion channel opening leads to decrease in membrane potential away from threshold (fewer action potentials, less “excitable”)
examples: GABA, lowers Vm when opens Cl- channels
Where is Ash used?
central, peripheral and autonomic neurons
can be excitatory or inhibitory depending on nicotinic or muscarinic receptor sub-type
Where is glutamate used?
major excitatory neurotransmitter in central neurons
Where is GABA used?
major inhibitory neurotransmitter in central neurons
Where is serotonin used?
central neurons, GI tract, platelets
mood and behavior effects largely due to dorsal raphe neurons in the midbrain and pons
Where is dopamine used?
central neurons
behavior, motivation, attention, memory, learning effects largely due to substantia nigra neurons in the midbrain
Where is norepinephrine used?
central neurons, autonomic neurons
behavior, arousal, attention, anxiety, learning and memory effects largely due to locus coeruleus in pons
