Ch 10 Flashcards
Detects changes, makes decisions, stimulates muscles and glands to respond, and maintains homeostasis:
nervous system
React to changes and sends nerve impulses for communication:
neurons
Surround and support neurons, nourish neurons, sends and receive messages, help and maintain blood brain barrier
neuroglia
What is the CNS made up of?
brain and spinal cord
What is the PNS made up of?
cranial nerves and spinal nerves
The sensory division of PNS takes impulses where?
to the brain and spinal cord
The motor division of PNS takes impulses where?
away from the brain and spinal cord
Somatic nervous system:
skeletal muscle
Autonomic nervous system:
smooth muscle, cardiac muscle, glands
Sensory functions do what?
receive info
The integrative function does what?
coordinates sensory info to create sensations
Motor function does what?
decisions are acted upon
This is a division of motor protons of PNS that transmits voluntary instructions to skeletal muscles
somatic nervous system
This is a division of motor protons of PNS that transmits involuntary instructions from the CNS to smooth muscles, cardiac muscles, and glands
autonomic nervous system
T or F neurons vary in size and shape
T
Contains nucleus, cytoplasm, organelles, neurofilaments, chromatophilic substance:
cell body
Branched receptive surfaces:
dendrites
Transmits impulses and releases neurotransmitters to another neuron:
axon
What are Schwann cells composed of?
myelin and myelin sheath
PNS neuroglia that encase axons in a sheath:
Schwann cells
Gaps in myelin sheath between Schwann cells:
Nodes of Ranvier
In the PNS have a series of Schwann cells lined up along the axon, each having a wrapped coating of myelin insulating the axon:
myelinated axons
Are encased by Schwann cell cytoplasm, but there is no wrapped coating of myelin surrounding the axons:
unmyelinated axons
Multipolar neurons, bipolar neurons, and unipolar neurons are classification of neurons by what?
structure
99% of neurons, many processes (dendrites), most neurons of CNS:
multipolar neurons
Two processes and consists of eyes, ears, nose:
bipolar neurons
One process, cell bodies are in ganglia, sensory:
unipolar neurons
Sensory neurons, interneurons, motor neurons are classification of neurons by what?
function
Carry impulses to CNS, most are unipolar, some are bipolar:
sensory neurons
Link neurons, multipolar, located in CNS:
interneurons
Multipolar, carry impulses away from CNS, carry impulses to effectors:
motor neurons
What are 3 general functions of neuroglia?
- provide structural support for neurons
- produce growth factors to nourish neurons
- aid in formation of synapses
Connects neurons to blood vessels, form scar tissue, regulate ion concentration, part of blood brain barrier:
astrocytes
Myelinated CNS axons and provide structural support:
oligodendrocytes
Phagocytic cell and provides structural support:
microglia
Lines central canal of spinal cord and ventricles of brain, help regulate composition of cerebrospinal fluid:
ependyma
Speed up nerve impulse transmission:
Schwann cells
Support clusters of neuron cell bodies:
Satellite cells
When does a neuron die?
when cell body is injured
(Neuron Regeneration of PNS) If a peripheral axon is injured, it may what?
regenerate
(Neuron Regeneration of PNS) Schwann cells and _______ remain.
neurilemma
(Neuron Regeneration of CNS) What do CNS axons lack?
neurilemma
(Neuron Regeneration of CNS) Is regenerating likely in this?
No
How do neurons communicate with each other?
synapses
A site at which a neuron transmits a nerve impulse to another neuron:
synapse
Send impulses:
presynaptic neuron
Receives impulses:
postsynaptic neuron
What separates these two neurons?
synaptic cleft
How does synaptic transmission work:
impulse travels down axon of presynaptic neuron
When impulse in synaptic transmission reaches synaptic knob, causes influx of ________.
Ca+2
This leaves to the release of what?
neurotransmitters
Electrically charged:
polarized
The inside of the membrane is what kind of charge?
The outside of the membrane is what kind of charge?
negative, positive
Major intracellular positive ions:
K+ ions
Major extracellular positive ions:
Na+ ions
Transports 3 Na+ ions out of cell and 2 K+ ions into cell:
Na+/K+ Pump
Formed by membrane proteins, help regulate passage of specific ions into or out of cell:
Ion channels
Resting neuron is one that is do what?
not being stimulated
_____ potential difference form inside to outside of cell
70 mV
In a polarized membrane more K+ ions are ________ and more Na+ ions are ______ of the cell.
inside, outside
Neurons are what kind of cells?
excitable
When membrane potential becomes more negative, the membrane is:
hyperpolarized
When membrane potential becomes less negative, the membrane is:
depolarized
When does action potential occur?
if degree of depolarization reaches threshold potential
At rest, the membrane is:
polarized (RMP= -70)
Threshold stimulus:
reached (-55 mV)
Sodium channels open and membrane:
depolarizes
Potassium leaves cytoplasm and membrane:
repolarizes
Action potentials are propagated down the length of the axon as:
nerve impulses
An action potential is a what kind of response?
all or none
If a neuron axon responds at all, it responds:
completely
All impulses carried on an axon are:
the same strength
Stimulus of greater intensity produce what kind of frequency of action potentials?
higher
During an impulse, the portion of the axon actively conducting the action potential is not able to respond to another threshold stimulus of normal strength:
refractory period
- Time when threshold stimulus cannot generate another action potential:
- Voltage-gated Na+ channels are briefly unresponsive:
absolute refractory period
- Time when only high-intensity stimulus can generate another action potential:
- Repolarization is not complete:
relative refractory period
Refractory period _________ number of action potentials generated per second.
limits
The speed of impulse conduction varies with:
myelination
Myelin is rich in lipids, and prevents water and water-soluble substance from crossing membrane; acts as
electrical insulator
Ions can cross membrane only through gaps in myelin sheath called:
Nodes of Ranvier
Myelinated axons transmits impulses through _______ _______ in which action potentials “jump” from node to node down the axon.
saltatory conduction
What also affects conduction speed?
axon diameter
Thick or thin axons transmit faster?
thick
- Reduces gradient for K+ to leave cell
- Threshold potential reached with stimulus of lower intensity
- Leads to excitable neurons, perhaps convulsions
increase in concentration of K+
- Neurons can become hyper polarized
- Action potentials are not generated
- Lack of impulses leads to muscle paralysis
decrease in concentration of K+
- Can be caused by some anesthetic drugs
- Stops impulses from passing through tissue fluid around axon
- Impulses do not reach brain
- There is no perception of touch and pain
Decrease in permeability to Na+ ions
Transmission of a nerve impulse from one neuron to another:
synaptic transmission
Local potentials resulting from changes in chemically gated ion channels are called:
synaptic potential
Increase permeability to Na+ ions, bring membrane closer to threshold, increase likelihood of generating impulses:
excitatory neurotransmitters
Move membrane farther from threshold, decrease likelihood of generating impulses:
inhibitory neurotransmitters
- Membrane change in which neurotransmitters opens Na+ channels
- Depolarizes membrane
- Action potential in postsynaptic neuron becomes more likely
excitatory postsynaptic potential
- Membrane change in which neurotransmitter opens K+ channels
- Hyperpolarizes membrane
- Action potential of postsynaptic neuron becomes less likely
inhibitory postsynaptic potential
EPSPs and IPSPs are added together in a process called:
summation
This leads to greater probability of an action potential:
net excitatory effect
This does not generate action potential:
net inhibitory
Summation of all inputs usually occurs where?
The trigger zone
Where are neurotransmitters produced?
rough ER and cytoplasm
When impulse reaches synaptic knob of axon, neurotransmitters are released by __________.
exocytosis
- Process of membrane recycling
- Synaptic vesicle becomes part of cell membrane as it releases neurotransmitters
- Endocytosis returns membrane to cytoplasm; forms new vesicles
vesicle trafficking
Neurons in brain or spinal cord synthesize what?
neuropeptides
Some neuropeptides act as what?
neurotransmitters
Substances which alter a neuron’s response to a neurotransmitter or block the release of a neurotransmitter:
neuromodulators
Human body produces opiated called:
endorphins
Groups of interneurons that make synaptic connections with each other, and are located completely within the CNS:
neuronal pools
- Increased neurotransmitter release, resulting from repeated impulses on excitatory presynaptic neurons
- Increases likelihood that postsynaptic cell will reach threshold
facilitation
- One neuron receives input from several neurons
- Makes it possible for a neuron to sum impulses from different sources
convergence
- One neuron sends impulses to several neurons, via branching of its axon
- Can amplify an impulse
- Activate several motor units in skeletal muscle
divergence
A drug that binds to receptor, and blocks neurotransmitter binding:
antagonist
A drug that activates receptor, causing action potential or aiding in binding of neurotransmitter:
agonist
