Chapter 2: Structure and Function of the Nervous System Flashcards
Embryonic stem cells destined to form the nervous system become two primary types: […]
neurons and glial cells (supporting cells)
Glial cells provide (3)…
metabolic support, protection, and insulation for neurons
Sensory neurons are sensitive to […].
environmental stimuli
Interneurons consist of…
nerve cells within the brain and spinal cord
Interneurons form complex interacting neural circuits and are responsible for (5)…
- conscious sensation
- recognition
- memory
- decision making
- cognition
Motor neurons direct a […] appropriate for the situation.
biobehavioral response
Neurons have what three major external features?
- soma
- dendrites
- axon
Neurons are enclosed by a […] and are filled with salty, gelatinous fluid– […].
semipermeable membrane; cytoplasm
T/F: Neurons have mitochondria.
true; they contain a lot because of the energy (ATP) requirement
Synapse:
gap between dendrites and the soma
Convergence:
when a neuron receives and integrates a vast amount of information from many cells
Divergence:
when integrated information is transmitted to a few neurons or to thousands of other neurons
Dendrites are usually covered with short […] this dramatically increases the receiving […].
dendritic spines; surface area
T/F: Dendrites and their spines exhibit constant modification.
true due to new associations with external interactions
How do the dendrites in someone who is intellectually impaired appear?
smaller and immature
Describe the appearance of dendrites/dendritic spines of someone who has schizophrenia:
dendritic size is normal; dendritic spine density is reduced
*particularly in the prefrontal cortex
Axons transmit information that is generated by the […].
axon hillock
Axon collaterals:
branching of neuron ends to influence many more cells
At the end of axons, there are small enlargements called […] which are located near the […] or […] of other cells.
terminal buttons; dendrites; somas
Terminal buttons are also called:
axon terminals or boutons
What is contained in terminal buttons?
synaptic vesicles of neurochemicals called neurotransmitters
How is myelin created?
concentric layers of glial cells
What are the two types of glial cells that create myelin sheath?
- Schwann cells
2. oligodendroglia cells
Schwann cells myelinate […] that serves […], organs, and […].
peripheral nerves; muscles; glands
Nodes of Ranvier:
bare spots along the axon
The thicker the myelin…
the quicker the conduction
How does myelination save energy?
reducing the effort required to restore the neuron to its resting state after transmission of the electrical signal
MS is an […] disease in which the immune system attacks a […] in the […] produced by […] only.
autoimmune; protein; myelin; oligodendrocytes
MS symptoms:
fatigue, numbness, poor coordination/balance, vision problems, bladder, bowel, and sexual dysfunction, cognitive function, and depression
The cell body is responsible for the […] of the neuron.
metabolic care
One of the most important functions of the soma is the synthesis of […] which are needed throughout the cell for […] and […].
proteins; growth; maintenance
What are the proteins included in the soma’s synthesis?
- enzymes
- receptors
- components of the cell membrane
Chromosomes:
long strands of DNA
Genes:
small portions of chromosomes that code for the manufacture of a specific protein
Transcription factors are […] that direct […].
nuclear proteins; protein production
Where do transcription factors bind?
promoter region
DNA methylation:
attachment of methyl group to a gene that causes a decrease in expression
Epigenetic modification. Is this pre or postnatal?
both; modifications can be created and passed on to future generations depending on the external conditions
What are some of the external conditions that can cause epigenetic modifications?
- stress
- abuse
- starvation/overeating
- environmental toxins
etc
Explain epigenetic modifications a child could experience if they’re overeating.
the child will undergo modifications that over-expresses the genes for obesity and under-expresses those for longevity
T/F: Maternal experiences influence the fetus.
true
T/F: Environmental events occurring before conception can also impact the health/behavior of offspring.
true
a stressed parent before conception can contribute to mental and physical difficulties of the offspring
Axoplasmic transport:
transportation of proteins produced in the soma of neurons
What does axoplasmic depend on?
cytoskeleton structure
Cytoskeleton: a matrix composed of […]. These include […] and […] that form a mesh-like mass that provides shape of the cell.
tubular structures; microtubules; neurofilaments
Microtubules run […] down the axon. It provides a […] along which small packets of newly synthesized […] are carried by specialized […].
longitudinally; stationary track; proteins; motor proteins
Newly synthesized proteins are packaged in the […] and transported in an […] toward the axon terminals.
soma; anterograde direction
Abnormalities of the cytoskeleton constitute one of several pathological features of the brain in people with…
Alzheimer’s disease
Neurofibrillary tangles:
found in people who have Alzheimer’s
hyperphosphorylation causes tau to separate from the microtubules and leads to entanglement of the usually parallel tubules
Neurofibrillary tangles evidently lead to the microtubules becoming…
disintegrated and destroys the material transport system which stops neuron communication
Because the membrane is not […] to charged molecules, special devices are needed to move molecules such as […], […], and metabolic products across the membrane.
readily permeable; amino acids; glucose
Special devices to move molecules (AA; GLU; metabolites) are…
transporter proteins and charged particles/ion channels
Ion channels are […] molecules that penetrate through the cell membrane and have a […] through which ions pass.
protein; water-filled pore
List the 3 ways that ion channels allow passage.
- ligand binds to receptor on the channel
- voltage gate opened due to electrical potential across the membrane near the channel is altered
- modification of a channel by a secondary messenger (phosphate group)
Ion channel important characteristics:
- relatively specific for particular ions
2. normally closed that are momentarily open by specific stimuli
List the two types of channels:
- ligand gated
2. voltage gated
Direction of ion travel across a membrane:
high to low concentration
If an open gate allows the passage of Na, Cl, and Ca to enter the cell, what moves out?
K
Glial cells have a significant role in neuron function because they provide […] to neurons, maintain the […] of neurons, and provide […] function.
physical support; chemical environment; immunological
What are the 4 principal types of glial cells?
- oligodendroglia
- Schwann cells
- astrocytes
- microglia
Schwann cells produce myelin sheath for the […] while oligodendroglia produces for the […].
PNS; CNS
Each oligodendroglia in the […] send out […] that wrap around segments of […] nearby axons to form myelin sheath.
CNS; multiple sheetlike arms; multiple
Which myelin sheath producer releases nerve growth factors when an axon is damaged or needs to grow?
Schwann cells
Describe astrocytes:
large, star-shaped cells that have numerous extensions
Astrocytes […] with neurons and provide […]; in addition, they help to maintain the […] around neurons and modulate the […] as well by taking up excess […] that might otherwise damage cells.
intertwine; structural support; ionic environment; chemical environment; neurochemicals
Which glial cell is most likely to help necessary material to move from the blood to nerve cells?
astrocytes
Microglial:
small scavengers that collect at sites of neuron damage to remove dying cells
Which glial cell is the primary source of immune response in the CNS?
microglial
Which glial cell is responsible for the inflammation reaction that occurs after brain damage?
microglia
Which glial cell inhibits re-growth of axons following neuron damage?
oligodendroglia
Which glial cell performs gliosis?
astrocytes
Which glial cell provides a channel to guide axons to target?
Schwann cells
Which glial cell has a potential role in the etiology of schizophrenia?
microglia
When the normal resting electrical charge of a neuron is distributed sufficiently by incoming signals from other cells…
a threshold is reached that initiates the action potential to convey a message along the axon to the terminal
Resting membrane potential:
electrical charge inside the cell
The inside of the neuron is more […] than the outside, making the neuron […] in its resting state.
negative; polarized
What would the voltmeter read when measuring the inside resting potential?
-70 mV
What is responsible for creating a membrane potential?
uneven distribution of ions and selective permeability of the membrane
If the inside is more negative at the resting potential, what contributes to the negative charge?
negatively charged AA and proteins that cannot leave the cell
Electrostatic potential explains why…
K ion is pulled into the cell
Equilibrium potential for potassium:
when the two forces on K are balance
inward electrostatic pressure and outward concentration gradient
For every 3 ions of Na pumped out…
two K ions are pumped in
Na-K pump:
energy dependent pump that contributes to the resting potential
Which ion has a greater ability to move freely through ungated channels?
K
Action potential can be generated when the membrane potential…
is changed from -70 mV to the threshold for firing -50 mV
What happens at -50mV?
voltage-gated Na channels open and generate a rapid change in membrane potential
List characteristics of hyperpolarization (5):
- more negative inside the cell
- membrane potential is farther from threshold
- ISPS caused by Cl channel open/entry
- ISPS cause by K channel open/entry
- greater stimulation produces larger hyperpolarizations
List characteristics of depolarization (4):
- more positive inside the cell
- membrane potential moves toward threshold
- EPSP caused by Na channel open/entry
- greater stimulation produces larger polarizations
Local potentials are induced by…
small, local changes in ion distribution/electrical potential differences
If Na ions enter the cell the membrane potential is brought closer to…
reaching the threshold for firing
Depolarization is […] and hyperpolarization is […].
excitatory; inhibitory
Neurotransmitters act on the […] membrane.
postsynaptic
List the significant characteristics of local potentials:
- graded– the larger the stimulus, the greater is the magnitude of hyper/depolarization
- rapidly decay once the stimulus stops
- integration– summation; they can add to amplify change or cancel each other out
Where in the neuron does integration occur?
within the axon hillock
The summation of local potentials at the axon hillock is responsible for generation of the […].
action potential
At the voltage -50mV, the […] occurs, causing […] ions to be driven in the cell and changing the membrane potential to […].
action potential; Na; +40mV
Absolute refractory period is the time that…
the Na ion channels are closed and cannot be open, regardless of the amount of excitation
What is the maximum number of action potentials that can occur?
1200 impulses/second
During the rising phase, the change in membrane potential due to […] entry causes the voltage-gated […] channels to open and move […] of the cell.
Na ion; K ion; K ions
The membrane potential actually […] the resting potential. This means the membrane is […] for a short amount of time.
overshoots; hyperpolarized
What can relieve the membrane when it is hyperpolarized?
Until the excess K ion diffuses away or is exchanged for Na ion by the Na-K pump
The brief hyperpolarizing phase is called the …
relative refractory period
T/F: The size of an action potential is related to the amount of stimulation.
false the two are unrelated (all-or-none)
Does the action potential decrease in size as it moves down an axon?
no, it is nondecremental
In myelinated axons (compared to unmylelinated), the speed of conduction is as much as […] times quicker.
15
Saltatory conduction:
the jump of conduction along a myelinated axon; action potential occurs only at the nodes of Ranvier in these types of axons
Myelinated axons use […] energy because the Na/K pump only has to work […].
less; at the nodes rather than all along the axon
Anesthetics impair axonal conduction by…
blocking voltage-gated Na channels
Blocking the Na channel means an […] cannot occur, and transmission of the pain signal cannot […].
action potential; reach the brain
Several antiepileptic drugs also block […] channels. It […] to close these channels so it can prolong the […] state of the channel, slowing down the […].
Na ion; selectively binds; refractory; firing rate
PNS can be divided into:
somatic and autonomic nervous system
Somatic nervous system:
controls voluntary muscles with both spinal nerves and cranial nerves
Autonomic nervous system:
autonomic nerves and some cranial nerves that control the function of organs and glands (EDIT)
The autonomic nervous system has both the…
sympathetic and parasympathetic divisions
The somatic nervous system can be referred to […] nerves as each spinal nerve consists of […] or […] neurons.
sensory; motor
Within each mixed nerve, sensory information is carried from the […] and from […] into the […] of the spinal cord by neurons that have their cell bodies in the […]. These are known as […].
surface of the body; muscles; dorsal horn; dorsal root ganglion; sensory afferents
Mixed nerves also have motor neurons, which are cells beginning in the […] of the spinal cord and ending on […]. These are called […] and are responsible for […].
ventral horn; skeletal muscles; motor efferents; voluntary movements
Which cranial nerve innervates organs in the viscera?
X; the vagus nerve
The vagus nerve consists of …
both sensory and motor neurons
What do the nerves in the ANS regulate?
the internal environment; innervate smooth muscles (heart, intestine, urinary bladder, glands)
ANS purpose:
control functions that provide/conserve energy appropriate to the environmental needs of the organism
List the two divisions of the ANS:
- sympathetic
2. parasympathetic
Sympathetic division predominates when…
energy expenditure is necessary; times of stress, excitment, and exertion
Fight or flight is what division of the nervous system?
sympathetic
Parasympathetic division predominates at times when…
energy reserves can be conserved and stored for later use
What are some examples of the parasympathetic division at work?
increase of salivation, digestion, storage of glucose and other nutrients and also slows heart rate and decreases respiration
What are some examples of the sympathetic division at work?
increases heart rate and blood pressure, stimulates secretion of adrenaline, increases blood flow to skeletal muscles
In contrast, the cell bodies of efferent parasympathetic neurons are located either in the […] or in the […] of the spinal cord in the […].
brain; ventral horn; sacral region
Which cranial nerves are efferent parasympathetic?
3, 7, 9, 10
Preganglionic fiber release […]..
acetylcholine
The delicate tissues that layer the brain and spinal cord are also known as […].
meninges
List the 3 meninges:
- dura mater
- arachnoid
- pia mater
Dura mater:
toughest and outermost layer
Arachnoid:
just below the dura, membrane with a web-like sublayer filled with CSF (subarachnoid)
