A&P 1-Chapter 12 Review
Which type of neuroglial cell engulfs cellular debris, waste products, and pathogens?
Microglia
What do neurons lack that most cells contain? What does this mean for the cell?
Most neurons lack centrioles and this means it cannot divide
What do nissl bodies do in response to injury?
Nissl bodies disperse, cell increases rate of protein synthesis
What is an example of flow of materials from the synaptic knob to the cell body?
Rabies is an example of flow of materials from the synaptic knob to the cell body.
Which carries impulses faster, continuous or saltatory?
Saltatory
Information about conditions inside and outside the body is known as _____________.
Sensory data
What are the 3 functional classifications of neurons?
Sensory neurons, motor neurons, and interneurons
Which controls skeletal muscle contractions?
Somatic nervous system (SNS)
What are the two divisions of the efferent division of the PNS?
Somatic nervous system (SNS) and Autonomic nervous system (ANS) (visceral motor system)
What is facilitation?
a neuron that is brought closer to the threshold
What is the all or none principle in relation to the neuron?
a stimulus either produces a typical action potential or does not produce one at all.
Describe the electrochemical gradient on Na.
a. Extracellular - high b. Intracellular - low c. Chemical gradient drives Na+ into cell d. Extracellular Na attracted to negative charge on inner surface
Describe the electrochemical gradient on K
a. Intracellular - high b. extracellular - low c. chemical gradient tends to drive out of cell d. electrical gradient opposes this movement because K+ attracted to - on inside and repelled by + outside
What does the peripheral nervous system consist of?
a. all the neural tissue outside the CNS b. carries sensory information to the CNS and carries motor commands to peripheral tissues and systems c. nerves - bundles of axons (nerve fibers) in the PNS; carries sensory information and motor commands d. cranial nerves - nerves connected to the brain e. spinal nerves - nerves connected to the spinal cord
Describe the events at a cholinergic synapse.
a. an action potential arrives and depolarizes the synaptic knob (normal stimulus for neurotransmitter release is depolarization of synaptic knob) b. Extracellular calcium ions enter the synaptic knob, triggering exocytosis of ACh (depolarization of synaptic knob opens voltage regulated Ca gates) c. ACh binds to receptors and depolarizes the postsynaptic membrane (primary response is increased permeability to Na) Depolarization is graded, if brought to threshold, an action potential will appear in the postsynaptic neuron d. ACh is removed by AChE - effects on the postsynaptic membrane are temporary
What are the 4 structural classifications of neurons?
a. anaxonic neuron b. bipolar neuron c. Unipolar neuron d. Multipolar neuron
Propagated changes in the transmembrane potential that, once initiated, affect and entire excitable membrane are known as _____________.
action potentials
Which brings sensory information to the CNS?
afferent division
What are the two functional divisions of the peripheral nervous system?
afferent division and efferent division
Sensory neurons are also known as ____________________.
afferent nuerons
The cells active and passive mechanisms do not ensure _____________________ .
an equal distribution of charges.
What is hyperplatization?
an increase in the negativity of the resting potential form -70mV to -80mV or more
Which are small and you cannot tell the axon from the dendrites?
anaxonic neuron
What is depolarization?
any shift from the resting potential - changes in potential from -70mV to smaller negative values
What do the ciliated ones in the brain assist in?
assist in circulation of CSF (cerebrospinal fluid - surrounds brain and spinal cord, provides protective cushion and transports dissolved gases, nutrients, and wastes)
Which is star shaped?
astrocytes
Which is the most numerous neuroglia?
astrocytes
What is the cell membrane covering the axoplasm?
axolemma
What is the long process from the cell body that is capable of propagating an electrical impulse?
axon
What are efferent fibers?
axons traveling away from CNS
What is the cytoplasm of the axon?
axoplasm
What are the functions of the CNS?
b. integrates, processes, and coordinates sensory data and motor commands c. higher functions (ex. - intelligence, memory, learning and emotion) d. sensory data - information about conditions inside/outside the body (ex. Body temp) e. motor commands - control or adjust activities of peripheral organs (ex. Control skeletal muscles when you walk)
What is the initial segment?
base of the axon
When does myelination begin and end?
begins late in development and not complete until early adolescence
Which has one dendrite, one axon, and a cell body inbetween?
bipolar neuron
What are nerves?
bundles of axons (nerve fibers) in the PNS; carries sensory information and motor commands
What are the functions of the PNS?
carries sensory information to the CNS and carries motor commands to peripheral tissues and systems
Where do motor neurons carry information?
carry info from CNS to peripheral effectors
What is the soma?
cell body of neuron
What effect does the electrical gradient have on the movement of K and Na?
cell membrane is more permeable to potassium than to sodium, so potassium leaves more readily than Na enters, this equals an interior net loss of positive charge, leaving an excess of negatively charge proteins
What is a neurotransmitter and where is it released from?
chemical messengers released by the presynaptic cell affect the postsynaptic cell (communication); packaged in synaptic vesicles
Which of the above is the most common type?
chemical synapses
What is the most wide spread synapse?
cholinergic synapse
At resting potential, most gate channels are __________.
closed
What are nissl bodies?
clusters of rough endoplasmic reticulum and ribosomes - synthesize proteins
What is a ganglion?
collection of neuron cell bodies in the PNS
What are motor commands?
control or adjust activities of peripheral organs (ex. Control skeletal muscles when you walk)
What is a membrane channel responsible for?
control the movement of ions across the cell membrane
The nerves connected to the brain are called ______________.
cranial nerves
What is perikaryon?
cytoplasm of neuron
What is Wallerian degeneration?
(PNS) schwann cells form hollow cord that follows path of neuron
What is an action potential?
- electrical impulse propagated across the surface of an axon and does not diminish as it moves away from its source
Describe the steps of a nerve impulse starting from depolarization of the initial segment to exciting the next neuron.
...
What is the threshold?
...
What is synaptic delay?
0.2-0.5 msec delay between arrival of action potential at synaptic knob and the effect on the post synaptic membrane, The fewer synapses involved, the shorter the total synaptic delay and the faster the response
What are the fine processes of dendritic branches?
dendritic spines
The effect of a neurotransmitter depends on what?
depends on the properties of the receptor, not on the nature of the neurotransmitter
Which carries motor commands to muscles and glands?
efferent division
Motor neurons are also known as _________________.
efferent neurons
What are synaptic terminals?
end of telodendria, part of synapse
What are the 4 types of neuroglia in the CNS?
ependymal cells, astrocytes, oligodendrocytes, microglia
Which are the epithelial cells that line the central canal of the spinal cord and ventricles of the brain?
epithelial cells
What does the sodium exchange pump do?
exchanges 3 intracellular sodium ions for 2 extracellular potassium, as resting potential it ejects sodium ions as soon as they come in, balances the passive forces of diffusion and the resting potential remains stable
What is an afferent fiber?
extend between sensory receptor and the spinal cord or brain
What do exteroceptors monitor?
external environment
What are telodendria?
fine extensions at the end of the axon or collaterals
What is the refractory period?
from the time an action potential begins until the normal resting potential has stabilized, the membrane will not respond normally to additional depolarizing stimuli
What is an excitatory postsynaptic potential?
graded depolarization caused by the arrival of a neurotransmitter at the postsynaptic membrane
What is an inhibitory postsynaptic potential?
graded hyperpolarization of the postsynaptic membrane
Changes if the transmembrane potential that cannot spread far form the area surrounding the site of stimulation is a _____________.
graded potentials
What is a post synaptic potential?
graded potentials that develop in the postsynaptic membrane in response to a neurotransmitter
What type of matter is dominated by unmyelinated fibers?
gray matter
What is the presynaptic cell?
has the synaptic terminal and sends a message
What will K and Na do in response to the chemical gradient passive force?
high concentration of K+ inside cell, tends to moveout through open K channels (concentration or chemical gradient) ii. high concentration of Na+ outside, so tend to come in
What are the two categories of neurotransmitters and what does each cause?
i. excitatory neurotransmitters - cause depolarization and promote the generation of action potentials ii. inhibitory neurotransmitter - cause hyperpolarization and suppress the generation of action potentials
What are the functions of Astrocytes?
i. maintaining the blood-brain barrier - isolates the CNS from general circulation ii. creating a three-dimensional framework for the CNS iii. repair damaged neural tissue iv. guiding neuron development v. controlling the interstitial environment
Why is there limited regeneration in the CNS?
i. more axons likely to be involved ii. astrocytes produce scar tissue that can prevent axon growth iii. astrocytes release chemicals that block the regrowth axon
What is synaptic fatigue?
if there is not enough ACh produced, the synapse remains inactive until ACh is replenished
Why does myelination improve coordination and control?
improves coordination and control by decreasing the time between the reception of a sensation and the initiation of an appropriate response
What functional type of neuron outnumbers all others?
interneurons
The areas of axon wrapped in myelin are known as ___________.
internodes
Where are interneurons located?
located within the brain and spinal cord
What is resistance?
measure of how much membrane restricts movement
What is myelin?
membranous wrapping of insulation, increases the speed at which an action potential travels along the axon
Which type is able to migrate through neural tissue?
microglia
Which type of neuroglial cells are least numerous and smallest?
microglia
What do interoceptors monitor?
monitor the digestive, respiratory, cardiovascular, urinary, and reproductive systems, taste, deep pressure and pain
What do proprioceptors monitor?
monitor the position and movement of skeletal muscles and joints
What is axoplasmic transport?
movement of materials (neurotransmitter, enzymes, and Lysosomes) between the cell body and the synaptic knob and vice versa. Materials flow in both directions.
Which has two or more dendrites and a single axon?
multipolar neuron
Which is the most common in the CNS?
multipolar neuron
What are voluntary contractions?
muscle contractions under your conscious control (ex. Writing and walking)
What are involuntary contractions?
muscle contractions under your subconscious control (ex. Put your hand on a hot stove) - reflex
What does axon diameter do to the propagation speed?
myelin increases speed
The inner surface has an excess of _____________ charges.
negative charges
What is involved in the cytoskeleton of a neuron?
neurofilaments, neurotubules, neurofibrils
What are the supporting cells of the nervous system called?
neuroglia
The basic functional unit of the nervous system is the _______________.
neuron
The areas in between internodes of oligodendrocytes are ______________.
nodes
What produces the myelin sheath in the CNS?
oligodendrocytes
What is a synaptic vesicle?
packages of neurotransmitters that are released by the presynaptic cell
What channels are always open?
passive or leak channels
What creates a current?
positive and negative attract, if nothing separates, move together and eliminate potential difference
The cytosol contains a high concentration of ___________.
potassium ions and negatively charged proteins
What are sensory receptors?
processes of specialized sensory neurons or cells monitored by sensory neurons
What is demyelination?
progressive destruction of myelin sheaths in both PNS and CNS, leads to loss of sensation and motor control
At each step, the message is repeated and the same events take place over and over, this is known as what?
propagation
What is the postsynaptic cell?
receives a message from the presynaptic cell
What are neuromodulators and what can they do?
released at the synapse with the main neurotransmitter, can alter rate of neurotransmitter release or change postsynaptic cell response
What is an interneurons responsible for?
responsible for distribution of sensory information and the coordination of motor activity
What is repolarization?
restoring normal resting potential after depolarization
What is a synaptic knob?
round synaptic terminal structure; contains mitochondria, portions of ER and neurotransmitter filled vesicles
What regulates the environment around the neurons?
satellite cells
What are the two neuroglia of the peripheral nervous system?
satellite cells and Schwann cells
What is responsible for myelination in the PNS?
schwann cells
The membrane of a neuron or axon is _______________________. What does this mean?
selectively permeable, means ions cannot freely cross, only through membrane channels
What is a receptor?
sensory structures that detect changes in the internal environment or respond to specific stimuli
What are collaterals?
side branches of an axon; enables communication with several cells
What are opioids and what do they do?
similar effects of opium and morphine, relief of pain, inhibit release of substance P that relays pain sensation
The extracellular fluid contains a high concentration of _______________.
sodium and chlorine ions
What do somatic motor neurons innervate? Visceral motor neurons?
somatic motor neurons innervate skeletal muscles and visceral motor neurons innervate all other peripheral effectors beside skeletal muscle
Which sensory neurons monitor the outside world?
somatic sensory neurons
The nerves connected to the spinal cord are called _______________.
spinal nerves
What is a graded potential?
stimulus produces temporary, localized change in the resting potential - graded potential - decreases with distance from stimulus
What are the two division of the Autonomic Nervous system?
sympathetic division and parasympathetic division
Where do neurons connect?
synapse
What is a neuromuscular junction?
synapse between a neuron and a muscle cell
What is a neuroglandular junction?
synapse between a neuron and a secretory (gland)cell
What is an effector?
target organs that respond to motor commands and do something
What is the difference between temporal and spatial summation?
temporal summation is the addition of stimuli occurring in rapid succession. Spatial summation involves multiple synapses that are active simultaneously.
What does the central nervous system consist of?
the brain and spinal cord
What is electrochemical gradient?
the sum of the chemical and electrical forces acting on that ion across the cell membrane
What is the axon hillock?
thickened region, connects the initial segment of the axon to the cell body
Where do sensory neurons deliver information?
to the CNS
What is resting potential?
transmembrane potential of a resting cell. All neural activities begin with a change in the resting potential of a neuron
What are some other neurotransmitters?
1. Norepinephrine - ANS, excitatory, depolarizing effect 2. Dopamine - CNS, either excitatory or inhibitory 3. Serotonin - CNS, may be responsible for many cases of severe chronic depression 4. Gamma aminobutyric acid or GABA - inhibitory
What are the 3 classes of gated channels? What does each respond to?
1. chemically regulated channels - open or close when they bind specific chemicals (Ach receptors) 2. voltage regulated channels - characteristic of excitable membrane - membrane capable of generating and conducting an action potential 3. mechanically regulated channels - open or close in response to physical distortion of the membrane surface
What are the 3 ways neurotransmitters and neuromodulators work?
1. compounds that have a direct effect on membrane potential - opening or closing membrane gated channels 2. compounds that have an indirect effect on membrane potential - have second messengers 3. lipid-soluble gases that exert their effects inside the cell
How do Astrocytes control the interstitial environment?
1. regulating the concentration of sodium ions, potassium ions, and carbon dioxide 2. providing a rapid transit system for the transport of nutrients, ions, and dissolved gases between capillaries and neurons 3. controlling the volume of blood flow through capillaries 4. absorbing and recycling some neurotransmitters 5. releasing chemicals that enhance or suppress communication across synaptic terminals
What is the resting potential? (number)
70mV
What does a cholinergic synapse release?
AcH
What are the 2 major divisions of the nervous system?
Central Nervous System (CNS) and Peripheral Nervous System (PNS)
Which part of the nervous system is responsible for higher functions such as intelligence, memory, learning, and emotion?
Central nervous system
What is the difference between continuous and saltatory propagation?
Continuous is an unmyelinated axon. In continuous propagation, i. action potential begins at the initial segment ii. the transmembrane potential becomes positive rather than negative iii. a local current then develops as sodium ions begin moving in the cytosol and the extracellular fluid - continuous propagation iv. each time a local current develops, the action potential moves forward, not backward because the previous segment is still in absolute refractory v. in continuous propagation, an action potential appears to move across the surface of a membrane in a series of tiny steps Saltatory propigation i. continuous propagation cannot occur along a myelinated axon, because myelin increase resistance to the flow of ions across the membrane ii. ions can readily cross the membrane only at nodes iii. when an action potential appears at the initial segment of a myelinated axon, the local current skips the internodes and depolarizes the node closest to the threshold iv. jumps from node to node - saltatory propagation v. carries impulses much more rapidly than continuous propagation vi. Myelination improves coordination and control by decreasing the time between the reception of a sensation and the initiation of an appropriate response
What are the processes of the cell body that receive information from other neurons?
Dendrites
Which controls smooth muscle, cardiac muscle, and glandular activity?
Autonomic nervous system (ANS)
What is the difference between chemical and electrical synapses?
Electrical Synapses a. located in the CNS and PNS b. extremely rare c. the presynaptic and postszynaptic membranes are locked together by gap junctions d. changes in the transmembrane potential of one cell will produce local currents that affect the other cell as if the two shared a common membrane Chemical Synapses a. cells are not directly coupled b. an arriving action potential may or may not release enough neurotransmitter to bring the postsynaptic neuron to threshold c. other factors may intervene and make the postsynaptic cell more or less sensitive to arriving stimuli d. most abundant type e. neurotransmitters
Describe type A,B, and C fibers.
Type A fiber - largest axon, myelinated, 300mph, urgent news Type B fiber - smaller, myelinated, 40 mph Type C fiber - unmyelinated, 2mph
Which has an axon and dendrite that are fused and the cell body lies off to one side?
Unipolar neuron
Which is most sensory neurons of the peripheral nervous system?
unipolar neuron
Which sensory neurons monitor the inside conditions?
visceral sensory neurons
What type of matter is dominated by myelinated fibers?
white matter
