Ch.10
Long-distance signals of axons
action potentials
Always open
leakage (non gated) channels
What are the two main types of ion channels?
leakage channels and gated channels
What pigment do you see in most elderly brain cells?
lipofuscin
What is the destruction of myelin sheaths in CNS by an immune response?
multiple sclerosis
99% of neurons, many processes, most neurons of CNS
multipolar neurons
What are the three classifications of neurons by structure?
multipolar, bipolar, unipolar
What is the sodium potassium pump important for?
muscle contraction and nerve conduction
Whitish, protein-lipid substance
myelin
Protects and electrically insulates axon, increases speed of nerve impulse transmission
myelin functions
Concentric layers of Schwann cell plasma membrane around axon
myelin sheath
Gaps between adjacent Schwann cells, sites where axon collaterals can emerge, formerly called nodes of Ranvier
myelin sheath gaps
Myelinated/Unmyelinated axons 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
Segmented sheath around most long or large-diameter axons
myelinated fibers
Where do neurons communicate?
synapses
What separates the two neurons?
synaptic cleft
What do axons do?
transmit nerve impulses along membrane to axon terminal
What does the motor (efferent) division do?
transmits impulses from CNS to effector organs
True or False: Axons lack rough ER and Golgi apparatus.
true
True or False: Mature neurons do not divide.
true
True or False: many chemical & electrical factors affect opening & closing of gated channels
true
True or False: neurons vary in size and shape.
true
True or False: non-myelinated fibers conduct impulses more slowly.
true
True or False: they may differ in length and size of their axons and dendrites.
true
True or false: If cell body is injured, the neuron usually dies.
true
True or false: neurons are highly excitable.
true
One process, cell bodies are in ganglia, sensory
unipolar neurons
Myelinated/Unmyelinated axons are encased by Schwann cell cytoplasm, but there is no wrapped coating of myelin surrounding the axons
unmyelinated
Where is cerebral spinal fluid produced?
ventricles of the brain
Mostly soma and unmyelinated fibers
gray matter
What serve as selective membrane ion channels?
large proteins
How many cranial nerves are there?
12
How many spinal nerves are there?
31
What are the types of neuroglia in the PNS?
Schwann cells and satellite cells
Contains both neuron cell bodies and their processes Processes see as white matter Cell bodies as grey matter
CNS
What are the two divisions of the nervous system?
CNS and PNS
A "nerve" is a collection of axons. Where would it be found?
PNS
Contains mainly neuron processes (few cell bodies)
PNS
Produce myelin sheath found on some peripheral axons. Speed up speed of nerve impulse transmission.
Schwann cells
What cell makes up the myelin in the PNS?
Schwann cells
Away from the cell body
anterograde
Support and brace neurons. Play role in exchanges between capillaries and neurons. Guide migration of young neurons. Control chemical environment around neurons. Respond to nerve impulses and neurotransmitters. Influence neuronal functioning (participate in information processing in brain).
astrocyte functions
Connect neurons to blood vessels; exchange nutrients and growth factors. Aid metabolism of certain substances. Regulate ion concentrations, such as K+. Part of Blood Brain Barrier.
astrocytes
Which type of cell are the most abundant CNS neuroglia?
astrocytes
Transmits impulses and releases neurotransmitters to another neuron or effector (another neuron, a muscle cell or a gland cell); a neuron may only have 1 axon
axon
Action potentials are generated at the
axon hillock
Two processes - eyes, ears, nose
bipolar neurons
What does the central nervous system contain?
brain and spinal cord
How can membrane potential changes be produced?
by changes in membrane permeability to ions
How are molecules moved along axons?
by motor proteins and cytoskeletal elements
Contains nucleus, cytoplasm, organelles, neurofilaments, chromatophilic substance (Nissl bodies)
cell body (soma)
What do ependymal cells line?
cerebrospinal fluid-filled cavities
Ions flow along their ___________________ when they move from an area of high concentration to an area of low concentration.
chemical gradient
What are the three types of gated channels?
chemically gated, voltage gated, mechanically gated
What does the peripheral nervous system do?
connects the central nervous system to other body parts (or the rest of the body)
What do dendrites do?
convey incoming messages toward cell body as graded potentials (short distance signals)
What does the peripheral nervous system contain?
cranial nerves and spinal nerves
What are microglia in the CNS?
defensive cells
What part of the cell is the "receiving" end?
dendrite, cell body
Branched receptive surfaces; a neuron may have many
dendrites
What generates a resting potential?
differences in ions across the membrane (due to sodium and potassium pump) and differential permeability of the plasma membrane
What are treatments of multiple sclerosis?
drugs that suppress immune activity
Ions flow along their __________________ when they move toward an area of opposite charge.
electrical gradient.
The electrical and chemical gradients taken together
electrochemical gradient
Line central canal of spinal cord & ventricles of brain, cover choroid plexuses. Help regulate composition of cerebrospinal fluid. Cuboidal or columnar cells; ciliated.
ependymal cells
True or False: "Neuron" and "nerve" can be used interchangeably.
false
True or False: Neurons experience a high rate of cell division.
false
True or False: myelin is found on axons and dendrites.
false
Is multiple sclerosis more common in males or females?
females
What do the processes on oligodendrocytes do?
form myelin sheaths around CNS nerve fibers
Motor (efferent) information travels TO/FROM the brain.
from
Part of protein changes shape to open/close channel
gated channels
Ions diffuse quickly across membrane along electrochemical gradients
gated channels are open
Incoming signals operating over short distances
graded potentials
What two types of signals do changes produce?
graded potentials and action potentials
What can a buildup of tissue in the ventricles of the brain cause?
hydrocephalus
Processing and interpretation of sensory input (create sensations, add to memory, produce thoughts)
integration
Association neurons, link neurons, multipolar, located in CNS
interneurons
What is the central nervous system responsible for?
interpreting sensory input and dictating motor output (integration and control center)
Formed by membrane proteins, help regulate passage of specific ions into or out of the cell
ion channels
What creates an electrical current and voltage changes across membrane?
ion flow
What is the sodium potassium pump important in?
maintaining a resting potential
What do neurons use as a way to communicate with other cells?
membrane potential changes
Phagocytic cell; also provides structural support
microglia
Small, ovoid cells with thorny processes that touch and monitor neurons. Migrate toward injured neurons. Can transform or "activate" to phagocytize microorganisms and neuronal debris.
microglial cells
Multipolar, efferent, carry impulses away from CNS, carry impulses to effectors
motor neurons
Activation of effector organs (muscles and glands) produces a response
motor output
What disease is associated with destruction of myelin?
multiple sclerosis
A cell membrane is usually electrically charged, or polarized, so that the inside of the membrane is __________ charged with respect to the outside of the membrane. This is a result of __________________________ on the inside and the outside of the membrane.
negatively, unequal distribution of ions
A grossly visible anatomic structure, and is a bundle of axonal processes from many different neurons, wrapped in a connective tissue sheath.
nerve
Bundles of neuron processes in PNS
nerves
Detects changes, makes decisions, stimulates muscles and glands to respond, and maintains homeostasis
nervous system
Highly cellular; little extracellular space, tightly packed
nervous tissue
Small cells that surround and wrap delicate neurons
neuroglia
Surround and support neurons, help maintain blood-brain barrier
neuroglia
Provide structural support for neurons. In embryo, guide neurons into position, may stimulate specialization. Produce growth factors to nourish neurons and remove excess ions and neurotransmitters. Aid in formation of synapses.
neuroglia functions
A cell, one part of which is included in a nerve.
neuron
Arm-like extensions from the soma (cell body) of all neurons There are two main types: dendrites and axons
neuron processes
CNS axons lack neurilemma to act as guiding sheath. Oligodendrocytes do not proliferate after injury. Regeneration is unlikely.
neuron regeneration in the CNS
If a peripheral axon is injured, it may regenerate. Axon separated from cell body and its myelin sheath will degenerate. Schwann cells provide guiding sheath for growing axons. If growing axon establishes former connection, function will return; if not, function may be lost.
neuron regeneration the PNS
React to change and communication
neurons
Structural units of nervous system Large, highly specialized cells that conduct impulses Extreme longevity (100 years or more) Amitotic (with few exceptions) High metabolic rate (requires continuous supply of oxygen and glucose) All have cell body and one or more processes
neurons
Excitable cells that transmit electrical signals
neurons (nerve cells)
What two types of cells does neural tissue contain?
neurons and neuroglia
Thin fibers not wrapped in myelin; surrounded by Schwann cells but no coiling
non-myelinated fibers
Myelinate CNS axons; also provide structural support.
oligodendrocytes
What are some examples of sensory (afferent) information?
pain, vision, hearing
Receives impulse
postsynaptic neuron
Major intracellular positive ions (cations)
potassium (K+) ions
Sends impulse
presynaptic neuron
What are dendrites?
receptive region of neuron
Resting neuron is one that is not being stimulated. Sodium and potassium ions follow rules of diffusion, and move from area of high concentration to area of low concentration. 70 mV potential difference from inside to outside of cell. Membrane of the neuron is a polarized membrane, with more potassium ions inside the cell, more sodium ions outside the cell, and more negatively charged ions & proteins inside. Inside of cell is negative relative to the outside of the cell. RMP = -70mV, due to unequal charge distribution. If resting potential changes, sodium and potassium pump restores it.
resting membrane potential (RMP)
Approximately -70 mV in neurons (cytoplasmic side of membrane negatively charged relative to outside). Membrane termed polarized.
resting potential
Toward cell body
retrograde
Support clusters of neuron cell bodies (ganglia).
satellite cells
What are the two functional divisions of the peripheral nervous system?
sensory (afferent) and motor (efferent)
Information gathered by sensory receptors about internal and external changes
sensory input
What are the general functions of the nervous system?
sensory input, integration, motor output
Afferent neurons, carry impulse to CNS, most are unipolar, some are bipolar
sensory neurons
What are the three classifications of neurons by function?
sensory, interneurons, motor
Major extracellular position ions (cations)
sodium (Na+) ions
Transports Na+ ions out of cell and K+ ions into cell
sodium potassium pump
What are the two divisions of the motor (efferent) division?
somatic nervous system and autonomic nervous system
Convey impulses from skin, skeletal muscles, and joints to CNS
somatic sensory fibers
What does the sensory (afferent) division contain?
somatic sensory fibers and visceral sensory fibers
One-way transfer of information. Impulse travels down axon of presynaptic neuron to axon terminal. When impulse reaches synaptic knob, causes influx of Ca+2 ions. This leads to release of neurotransmitters from synaptic vesicles by exocytosis. Neurotransmitter will exert either excitatory or inhibitory effect on postsynaptic neuron.
synaptic transmission
Sensory information travels TO/FROM the brain.
to
Bundles of neuron processes in CNS
tracts
Convey impulses from visceral organs to CNS
visceral sensory fibers
In a gross brain specimen, myelin appears gray/white.
white
Dense collections of myelinated fibers
white matter