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Unit 4: The Nervous System
Terms in this set (90)
specialized cells capable of transmitting electrical impulses and then translating those electrical impulses to chemical signals
Neurons communicate using ______ and ______ forms of communication
electrical and chemical
occurs via ion exchange and the generation of membrane potentials down the length of the axon
occurs via neurotransmitter release from the presynaptic cell and the binding of these neurotransmitters to the postsynaptic cell
appendages that receive dignals from other cells
Soma (or cell body)
the location of the nucleus as well as organelles such as the endoplasmic reticulum and ribosomes.
where the cell body transitions to the axon, and where action potentials are initiated
a long appendage down which an action potential travels
nerve terminal or synaptic bouton
the end of the axon from which neurotransmitters are released
Nodes of Ranvier
exposed areas of myelinated axons that permit saltatory conduction
consists of the nerve terminal of the presynaptic neuron, the membrane of the postsynaptic cell, and the space between the two (synaptic cleft)
Many axons are coated with ______, an insulating substance that prevents signal loss.
Myelin is created by....
oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system
Myelin prevents ________ of the neural impulse and _____ of the neural impulses from adjacent neurons.
individual axons are bundled into ______ or _____.
A single nerve may carry multiple types of information such as ______, ______, or _______. Tracts contain only one type of information.
sensory; motor; mixed
In the central nervous system, axons may be bundled together to form ____.
The cell bodies of neurons in the same tract are grouped into ______
Neuroglia or glial cells
other cells within the nervous system in addition to neurons
nourish neurons and form the blood-brain barrier, which controls the transmission of solutes from the bloodstream into nervous tissue
line the ventricles of the brain and produce cerebrospinal fluid, which physically supports the brain and serves as a shack absorber
phagocytic cells that ingest and break down waste products and pathogens in the central nervous system
___________ (CNS) and ________ (PNS) produce myelin around axons.
Oligodendrocytes; Schwann cells
all-or-nothing messages used to relay electrical impulses down the axon to the synaptic bouton
Maintenance of Resting Membrane Potential
Action Potential Propagation
resting membrane potential
there is an electrical potential difference (voltage) between the inside of the neuron and the extracellular space
Resting potential is maintained using ________ of ions as well as the ______.
selective permeability; Na+/K+ ATPace
Excitatory signals cause _________ of the neuron
depolarization (raising the membrane potential from its resting point)
Inhibitory signals cause _______ of the neuron
hyperpolarization (lowering the membrane potential from its resting point)
the additive effects of multiple signals
multiple signals are integrated during a relatively short period of time
the additive effects are based on the number and location of the incoming signals
used to propagate signals down the axon
When enough excitatory stimulation occurs, the cell is ________ to the ______ and voltage-gated sodium channels open
depolarized; threshold value
Sodium flows into the neuron due to its strong ____________. This continues depolarizing the neuron.
At the peak of the action potential (approximately ____), sodium channels are ______ and ________ channels open.
+35mV; inactivated; potassium
closed sodium channels
before the cell reaches threshold, and after inactivation has been reversed
open sodium channels
from threshold to approximately +35mV
inactive sodium channels
from approximately +35mV to the resting potential
a restoration of the negative membrane potential
caused by the efflux of K+, it makes the neuron refractory to further action potentails
absolute refractory period
no amount of stimulation can cause another action potential to occur
relative refractory period
there must be a greater than normal stimulation to cause an action potential because the membrane is starting from a potential that is more negative then its resting value
The __________ brings the neuron back to the resting potential and restores the sodium and potassium gradients
While the axon is hyperpolarized, it is in the ________.
extraordinarily good insulator, preventing the dissipation of the electric signal in mammals
the neuron preceding the synaptic cleft
the neuron after the synaptic cleft
when a neuron signals to a gland or muscle, rather then another neuron
Most synapses are _____ in nature; they use small molecules referred to as ______ to send messages from one cell to the next
Neurotransmitters can be broken down by _______.
Neurotransmitters can be brought back into the presynaptic neuron using ________.
serotonin, dopamine, and norepinephrine are ______
neurostransmitter can diffuse out of the ______.
At the nerve terminal, neurotransmitters are released into the _______.
When action potential arrives at the nerve terminal, ____ channels open.
The influx of calcium causes ______ of vesicles filled with neurotransmitter with the _________, resulting in _______ of neurotransmitter into the synaptic cleft.
fusion; presynaptic membrane; exocytosis
The neurotransmitters bind to receptors on the postsynaptic cell, which may be _______ ion channels or _______ receptors.
lignad-gated; G protein-coupled
Neurotransmitters must be cleared from the _________ to stop propagation of the signal.
Functions of the nervous system
-sensation and perception
-cognitive (thinking) and problem solving
-executive function and planning
-language and comprehension and creation
-emotion and emotional expression
-balance and coordination
-regulation of endocrine organs
-regulation of heart rate, breathing rate, vascular resistance, temperature, and exocrine glands
three kinds of nerve cells in nervous system
sensory neurons, motor neurons, and interneurons
Sensory neurons (also known as afferent neurons)
transmit sensory information from receptors to the spinal cord and brain
Motor neurons (also known as efferent neurons)
transmit motor information from the brain and spinal cord to muscles and glands
found between other neurons and are the most numerous of the three types. Often linked to reflexive behavior
Afferent neurons ______ in the spinal cord toward the brain; efferent neurons _____ the spinal cord on their way to the rest of the body
central nervous system (CNS)
composed of the brain and spinal cord
consists of axons encased in myelin sheaths
consists of unmyelinated cell bodies and dendrites
four divisions of the spinal cord
cervical, thoracic, lumbar, sacral
The spinal cord is protected by the _______, which transmits nerves at the space between adjacent vertebrae.
peripheral nervous system (PNS)
made up of nerve tissue and fibers outside the brain and spinal cord, 12 pairs of cranial and 31 pairs of spinal nerves
somatic nervous system
consists of sensory and motor neurons distributed throughout the skin, joints, and muscles
autonomic nervous system (ANS)
regualtes heartbeat, respiration, digestion, and glandular secretions
The first neuron in the autonomic nervous system is called the _____ neuron. The second neuron is the _______ neuron.
ANS has two subdivisions:
the sympathetic nervous system and the parasympathetic nervous system
parasympathetic nervous system
main role is to conserve energy, associated with resting and sleeping states to reduce heart rate and constrict the bronchi
sympathetic nervous system
activated by stress, when activated it
-increases heart rate
-redistributes blood to muscles of locomotion
-increases blood glucose concentration
-relaxes the bronchi
-decreases digestion and peristalsis
-dilates the eyes to maximize light intake
-releases epinephrine into the bloodstream
control reflexive behavior, use the ability of interneurons in the spinal cord to relay information to the source of stimuli while simultaneously routing it to the brain
monosynaptic reflex arc
single synapse between the sensory neuron that receives the stimulus and the motor neuron that responds to it
ex: knee-jerk reflex
polysynaptic reflex arc
there is at least one interneuron between the sensory and motor neurons
ex: withdraw reflex (stepping on a nail)
action potential travels down the axon and initiates neurotransmitter release
pumps three sodium ions out of the cell for every two potassium ions pumped in
Structure of a Neuron
Breakdown of a Neurotransmitter by an Enzyme
Reuptake of a Neurotransmitter
Major Divisions of the Nervous System
The Spina Cord
Functions of the Parasympathetic Nervous System
Functions of the Sympathetic Nervous System
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