Biology Chapter 4: The Nervous System (4 Stars) Flashcards
Neurons are highly specialized cells responsible for the conduction of _________
impulses
Neurons communicate using both electrical and ______ forms of communication.
chemical
Electrical communication occurs via _____ and the generation of membrane potentials down the length of the axon.
ion exchange
Chemical communication occurs via ______ release from the presynaptic cell
neurotransmitter
release from the presynaptic cell and the binding of these neurotransmitters to the postsynaptic cell.
Dendrites are appendages that receive _____ from other cells.
signals
The ________ is the location of the nucleus as well as organelles such as the endoplasmic reticulum and ribosomes.
cell body or soma
The ______ is where the cell body transitions to the axon, and where action potentials are initiated.
axon hillock
The axon is a long appendage down which a(n) __________travels.
action potential
The nerve terminal or synaptic bouton is the ____ of the axon from which neurotransmitters are released.
end
Nodes of Ranvier are exposed areas of ______ axons that permit saltatory conduction.
myelinated
The synapse consists of the nerve terminal of the presynaptic neuron, the membrane of the postsynaptic cell, and the space between the two, called the _______
synaptic cleft.
Many axons are coated in ______, an insulating substance that prevents signal loss.
myelin
Myelin is created by ________ in the central nervous system and Schwann cells in the peripheral nervous system.
oligodendrocytes
Myelin prevents dissipation of the neural impulse and crossing of neural impulses from ______ neurons.
adjacent
Individual axons are bundled into ______ or tracts.
nerves
A single nerve may carry multiple types of information, including sensory, motor, or both. Tracts contain # ____ type of information.
only one
Cell bodies of neurons of the same type within a nerve ______ in ganglia in the peripheral nervous system.
cluster
Neuroglia or _____ cells are other cells within the nervous system in addition to neurons.
glial
Astrocytes nourish _______ and form the blood–brain barrier, which controls the transmission of solutes from the bloodstream into nervous tissue.
neurons
________ line the ventricles of the brain and produce cerebrospinal fluid, which physically supports the brain and serves as a shock absorber.
Ependymal cells
______ are phagocytic cells that ingest and break down waste products and pathogens in the central nervous system.
Microglia
Oligodendrocytes (CNS) and Schwann cells (PNS) produce _____ around axons.
myelin
All neurons exhibit a resting membrane potential of approximately ____ mV.
–70 mV.
Resting potential is maintained using selective permeability of ions as well as the ________
Na+ /K+ ATPase.
The Na+ /K+ ATPase pumps # ___ sodium ions out of the cell for every #___ potassium ions pumped in.
3 sodium ions out
2 potassium ions pumped in.
Incoming signals can be either _______ or inhibitory.
excitatory
Excitatory signals cause _______ of the neuron.
depolarization
Inhibitory signals cause __________ of the neuron.
hyperpolarization
______ summation refers to the addition of multiple signals near each other in time.
Temporal
_______ summation refers to the addition of multiple signals near each other in space.
Spatial
An action potential is used to propagate signals ______ the axon.
down
When enough excitatory stimulation occurs, the cell is _______ to the threshold voltage and voltage-gated ______ channels open.
depolarized
sodium
_____ flows into the neuron due to its strong electrochemical gradient. This continues depolarizing the neuron.
Sodium
At the peak of the action potential (approximately +35 mV), ________ channels are inactivated and ___________ channels open.
At the peak of the action potential (approximately +35 mV), sodium channels are inactivated and potassium channels open.
Potassium flows out of the neuron due to its strong electrochemical gradient,_______ the cell.
_________ channels stay open long enough to overshoot the action potential, resulting in a hyperpolarized neuron; then, the potassium channels close.
repolarizing the cell.
Potassium
While the axon is hyperpolarized, it is in its _______ period.
refractory period.
The impulse propagates down the length of the axon because the influx of sodium in one segment of the axon brings the subsequent segment of the axon to _______.
threshold.
The fact that the preceding segment of the axon is in its refractory period means that the action potential can only travel in one direction.
At the nerve terminal, neurotransmitters are released into the _______
synapse.
When the action potential arrives at the nerve terminal, voltage-gated calcium channels _____
open.
The influx of ______ causes fusion of vesicles filled with neurotransmitter with the presynaptic membrane, resulting in exocytosis of neurotransmitter into the synaptic cleft.
calcium
The neurotransmitters bind to receptors on the ________ cell, which may be ligand-gated ion channels or G protein-coupled receptors.
postsynaptic cells
The neurotransmitter can be ________ back into the presynaptic cell by reuptake channels.
absorbed
There are three types of neurons in the nervous system: motor (efferent) neurons, ________ and sensory (afferent) neurons.
interneurons
SAME
The nervous system is made up of the (2)
(CNS; brain and spinal cord) and peripheral nervous system (PNS; cranial and spinal nerves).
In the CNS, white matter consists of myelinated axons, and grey matter consists of _______ bodies and dendrites. In the brain, _______ matter is deeper than grey matter. In the spinal cord, ______ matter is deeper than white matter.
unmyelinated cell bodies
white matter
grey matter
The PNS is divided into the________ (voluntary) and autonomic (automatic) nervous systems.
somatic (voluntary)
The autonomic nervous system is further divided into the __________ (rest-and-digest) and ______ (fight-or-flight) branches.
parasympathetic
sympathetic
Reflex arcs use the ability of _______ in the spinal cord to relay information to the source of a stimulus while simultaneously routing it to the brain.
Reflex arcs use the ability of interneurons in the spinal cord to relay information to the source of a stimulus while simultaneously routing it to the brain.
In a monosynaptic reflex arc, the _______ neuron fires directly onto the motor (efferent, postsynaptic) neuron.
sensory (afferent, presynaptic)
In a polysynaptic reflex arc, the sensory neuron may fire onto a _____ neuron as well as interneurons that fire onto other motor neurons
motor
During the absolute refractory period, the cell is _____ to fire another action potential.
unable
During the relative refractory period, the cell requires a _____ than normal stimulus to fire an action potential.
larger
