Nervous System Overview and Action Potentials 1 Flashcards
What are the overall functions of the nervous system
keep the body in systemic homeostatic processes by
-muscle contraction
-integration of blood oxygen, carbon dioxide, and pH levels via respiratory activity
-regulation of volumes and pressures in circulation via cardiovascular and urinary function
-digestive system motility and secretion
What is the functional unit of nervous system?
neurons
What are neuroglia?
support cells for neurons
What type of signals does the nervous system use?
both electrical and chemical signals
What is the integrating center of the nervous system?
the CNS
-brain and spinal cord
What cells are a part of the effector pathway in the nervous system?
motor neurons
What cells are a part of the affector pathway in the nervous system?
sensory neurons
What are dendrites?
ends of the neurons that are stimulated by environmental changes or the activities of other cells
What are the cell body of neurons?
parts of the neurons that contain the nucleus and organelles
What is the axon hillock?
the first part of the axon
What is the axon?
the part of the neuron that conducts the nerve impulses
What are the synaptic terminals?
ends of the neuron that affect other neuron or effector organ
What are the nissl bodies?
clusters of ribosomes in the nucleus that give a gray appearance
Where are there more nissl bodies?
in the gray matter of the brain
What are internodes?
the segments of the myelin on a neuron
What make the internodes in the PNS?
Schwann cells
What make the internodes in the CNS?
Oligodentrocytes
What is the space that separates the internodes on the axon of a neuron?
nodes of Ranvier
What is the function of the neurons?
speed up the rate of the nerve impulse
What is saltatory conduction?
the jumping of action potential down the axon with the use of the myelin
What are sensory neurons?
-parts of the afferent division of PNS
-carry sensory info from reflex to CNS
-axons typically myelinated and extend to CNS
-dendrites/cell bodies in PNS
What type of neurons are sensory neurons usually?
pseudounipolar or bipolar
What are motor neurons?
-efferent division of PNS
-carry motor commands from CNS to effectors
-dendrites/cell bodies in CNS
-ions typically myelinated, extend into PNS and synapse with effectors
What type of neurons are motor neurons usually?
multipolar
What are interneurons?
-found only in CNS
-carry information from one neuron to another
-integration
-may or may not be myelinated
What type of neurons are interneurons?
multipolar or anaxonic
What are the two types of electrical signals in neurons?
action potentials and graded potentials
What are action potentials?
-always the same with no change in strength or size as they travel
-all-or-none
-triggered at axon hillock when threshold potential reached
-always propagates along cell membrane
-relatively fast changes in Vm
What are graded potentials?
-small changes in membrane potential of variable strength/amplitude
-only travel a short distance along membrane and lose strength as they travel
-typically last longer than APs
What are synaptic potentials?
generative in post synaptic cell in a synapse
What are EPSPs?
excitatory postsynaptic potentials
-depolarizations
-Vm move toward threshold potentials
-increase likelihood of AP
What are IPSPs?
inhibitory postsynaptic potentials
-hyperpolarizatios
-move away from Vm
-decrease likelihood of Vm
What are receptor potentials?
reflex receptor
-excitatory
What are end plate potentials?
skeletal muscles
-excitatory
What is depolarization?
Vm becomes more positive
-EPSPs
What is repolarization?
Vm returns to resting value
What is hyperpolarization?
Vm becomes more negative than resting
-IPSPs
What happens to Na channels when the membrane potential reaches threshold?
voltage gated sodium channels open and allow Na to enter the cell rapidly
Once the action potential gets to the amplitude, what happens to the Na and K channels?
the voltage gated Na channels close and the voltage gated K channels open and K flows out
What causes hyperpolarization?
the voltage gated K channels remain open after resting membrane potential is reached, so more K can leave causing the membrane potential to become more negative than rest
What is special about the voltage gated Na channels?
there are two gates
-activation gate
-inactivation gate
How does the activation gate of voltage gated Na channels work?
closed at resting membrane potential
-quickly open at threshold depolarization
How does the inactivation gate of voltage gated Na channels work?
open at resting membrane potential
-slowly closes at threshold depolarizataion
How do voltage gated K channels work?
single voltage gate begins to open at threshold
-but is slow
-open around the same time the VG channel inactivation gate closes
Does Na or K have a faster conductance through voltage gated channels?
Na
-the activation gate is fast and opens quickly allowing Na to flow faster than K
What type of feedback does activation of Na channels occur?
positive feedback
