Nervous System Flashcards
The Nervous System
One of the two major control systems of the body mediating systemic homeostatic processes
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what homeostatic processes does the NS mediate? (4)
muscle contraction
integration of blood oxygen, carbon dioxide, and pH levels via respiratory activity
regulation of volumes and pressures in the circulation via cardiovascular and urinary function
digestive system motility and secretion
the NS works along with — to Maintain Systemic
Homeostasis
Endocrine System (ES)
NS is — fix to homeostatic disturbance and ES is —
quick
slower long term maintenance
NS Functional unit =
Neurons
Neuroglia =
support cells for neurons
NS uses a combination of (2) to
communicate information around body
chemical and electrical signals
dendrites are simulated by (2)
environmental changes or the activities of other cells
cell body
contains the nucleus and mitochondria, ribosomes, and other organelles and inclusions
axon
conducts nerve impulse (AP) toward synaptic terminals
synaptic terminals affect
another neuron or effector organ (muscle or gland)
nissl bodies
clusters of ribosomes found in the cell body
Many neurons have axons
that are —
myelinated
— formed by neuroglia cells
Internodes
– form myelin for axons in CNS
Oligodendrocytes
– form myelin for axons in PNS
Schwann cells
Internodes separated by small
segments of axon not covered
in myelin –
Nodes of Ranvier
function of Nodes of Ranvier
Speed up the rate of nerve impulse conduction (Saltatory conduction)
types of neurons (structural classification) (4)
anaxonic
bipolar
pseudo unipolar
multipolar
Types of Neurons (Functional Classification) (3)
sensory
motor
interneurons
Sensory Neurons (pseudounipolar neurons, bipolar) (4)
Afferent division of PNS
Carry sensory information from reflex receptor to CNS
Dendrites/Cell body in PNS
Axons typically myelinated and extend into CNS
Motor Neurons (Multipolar neurons) (4)
Efferent division of PNS
Carry motor commands from CNS to EFFECTORS
Dendrites/Cell body in CNS
Axons typically myelinated, extend into PNS and synapse
with effectors
Interneurons (Multipolar, Anaxonic) (3)
Found only in the CNS
Carry information from one neuron to another
Integration
Information flows in
one direction
Action Potentials (AP): (5)
–Always the same (depolarization followed by repolarization) with no change in strength or size as they travel along the membrane
–All-or-none
–Triggered at Axon Hillock when Threshold Potential reached (Vm at which AP triggered; typically around -50mV))
–Always propagates along cell membrane of axon from axon hillock toward axon terminals
–Relatively fast changes in Vm
Graded Potentials (GP): (3)
–Small changes in membrane potential of variable strength/amplitude
–Only travel a short distance along membrane and lose strength as they travel
–Often last longer than APs
examples of GP (2)
EPSP
IPSP
EPSP
Excitatory postsynaptic potentials (depolarizations); moves Vm
towards threshold potential; increases likelihood of AP
IPSP
Inhibitory postsynaptic potentials (hyperpolarizations); moves Vm away
from threshold; decreases likelihood of AP
Depolarization
Vm becomes more positive (less
negative). EPSPs
Repolarization
Vm returns to resting value
Hyperpolarization
Vm becomes more negative than resting. IPSPs
Which ion channels, if
opened, cause an EPSP? (2)
Na
Ca
Which ion channels cause an IPSP? (2)
K closed
Cl open
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Example of a Graded Potential becoming an Action Potential in a Neuron (graph, A-F)
A. Resting Membrane Potential
B. EPSP depolarizes membrane
C. EPSP reaches threshold and causes voltage-gated Na+ channel to open—transition from graded
potential to action potential (axon hillock)
D. Depolarization; Na+ moves into the cell through open Voltage-gated (VG)-Na+ channels. Activated via positive feedback (see slide 16).
E. VG Na+ channels close & slow voltage-gated K+ channels open
F. Repolarization; K+ moves outside of the cell through open VG K+ channels
G. Hyperpolarization; VG K+ channels still open
H. Voltage-gated K+ channels close
A. Resting membrane potential
Activation gate
Closed
at resting Vm, quickly
opens at threshold
depolarization
Inactivation gate
Open
at resting Vm, slowly
closes at threshold
depolarization
Voltage-gated K+ channel:
Single voltage gate begins to open
at threshold, but is slow–delayed by
the same time as the VG Na+
channel’s inactivation gate.
