Ch. 12. LOC
When sodium ions flow into a cell through a leak channel they make the membrane potential more
positive/depolarized
An inhibitory neurotransmitter may cause the opening of a ______ channel.
potassium or chloride
Propagation of depolarization only flows away from the cell body towards the synaptic knob because ______.
previous regions in the axon have sodium channels in the inactive state
afferent
sensory, conveying toward a center (interneuron on spinal cord, usually an inhibitor of inhibitor)
The leak of potassium ions tends to drive the membrane potential to -90 millivolts, and yet the normal resting membrane potential (RMP) of a neuron is around -70 millivolts. What is the reason for this difference?
A small leak of sodium ions makes the RMP more positive.
Microglia
Act as phagocytes, eating damaged cells and bacteria, act as the brains immune system not white blood cells
Sensation modes
Afferent general: conscious Visceral: can't detect, pH, BP Special: vision, taste, smell, listen- stimulate a certain response in us
myelin destruction example
CNS myelin sclerosis: scar, autoimmune disease symptoms: cycles of relapse/remission visual and speech disturbance, bladder incontinence and muscle weakness -because controlling center and peripheral system is damaged! heat intolerance
Which of the following pumps can you find in the plasma membrane?
Ca2+ Na+/K+
Motor modes
Efferent, effectors Somatic: skeletal, voluntary Autonomic (ANS): smooth m, cardiac m, glands involuntary
Cerebrospinal Fluid
Fluid in the space between the meninges that acts as a shock absorber that protects the central nervous system. made from ependymal cells sleep matters for the waste clearing mechanism, and so pulling an all nighter the night before an exam is unnaffective
Which of the following ions have leak channels on the plasma membrane?
K+ Na+
_____ is caused by the destruction of oligodendrocytes.
Multiple sclerosis
The nerve impulse has the voltage-gated ______ channels opened first followed by the opening of the voltage-gated ______ channels.
Na+; K+
axonal transport
The transportation of materials from the neuronal cell body to distant regions in the dendrites and axons, and from the axon terminals back to the cell body.
True or false: There are more potassium leak channels in a neuron membrane than sodium leak channels.
True, The dominance of potassium leak makes the RMP negative.
Ohm's Law
V=IR, r - resistance, cell membrane in an insulator (separates ions) I - current, channels are conductors that allow ions to flow
______ are not commonly found in the receptive segment of a neuron.
Voltage-gated ion channels
perineurium surrounds
a fascicle of nerve fibers
True or false: Many voltage-gated channels are found in the receptive segment of a neuron.
false
ependymal cells
filtration cells line cavities of the brain and spinal cord, circulate cerebrospinal fluid similar to epithelial cells (ciliated columnar) involved in cerebrospinal fluid (CSF) production - line fluid filled space
the flow of sodium ions through sodium channels is best described as ______.
from outside the cell to inside
Channels that allow an ungated flow of specific ions from regions of high concentration to regions of low concentration are called .... channels.
leak
potential energy
mechanical or chemical
The small spaces that interrupt the myelin sheath are called ______.
neurofibril nodes
cell types of nervous tissue
neurons and neuroglia
A fascicle is a bundle of ________.
axons
Cytoplasm within an axon is called ______.
axoplasm
Most synapses in the human body are ______ synapses.
chemical
Neurons (nerve cells)
divas, exacting, excitable, hungry for oxygen communicate via "action Potentials" -, nerve signal, electrical signals to activate or inhibit
Match the location with the larger concentration of ions. extracellular and intracellular sodium and organic ions
extracellular matches sodium intracellular matches organic ions
What is found in the ganglia of spinal nerves?
neuron cell bodies
A ______ is a channel that is usually closed but which opens in response to binding a neurotransmitter.
neurotransmitter
which of the following would be likely to cause hyperpolarization of a neuron?
opening of a chemically gated chloride channel opening of a voltage-gated potassium channel
The sequential opening of voltage-gated sodium channels is followed by the sequential opening of voltage-gated .... channels.
potassium
Membrane molecules that use the energy of ATP to move ions against a concentration gradient are called
pumps
Chemical Potential Energy (CPE)
stored energy via "resting membrane potential" measured as difference in amount of separated changes (mV)
he process by which postsynaptic potentials are added together at the initial segment is known as
summation
Neuroglia (support cells)
support, and protect outnumber neurons 10:1
Which of the following segments of a neuron contains large numbers of voltage-gated potassium channels and voltage-gated sodium channels?
the conductive segment the initial segment
The all-or-none law refers to the fact that action potentials will only occur if the initial segment reaches
threshold
True or false: Most voltage-gated ion channels are closed until the electrical potential across a membrane changes.
true
Explain the general organization of the nervous system and identify which division(s) conduct afferent or efferent (or both) information.
2 organizations: structural and Functional Structural = CNS ( Brain and spinal cord) PNS (Nerves and Ganglia) Functional = input/output - Sensory Nervous system and Motor Nervous system Sensory = Somatic (conscious, eyes, ears, skin) or Visceral (receptors of blood vessels and internal organs) Motor = Somatic (voluntary/conscious) or Autonomic (cardiac muscle, smooth muscle, glands)
myelin sheath
A layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next signal doesn't decay, game of telephone uses less ATP if unmyelinated, slower
Define what is a "potential" and explain how the Resting Membrane Potential is (a) established, and (b) maintained.
"potential": separation of charges, ready to do work and signal neurotransmitter resting membrane potential is when it is not actively sending a message but is ready, like Sadie Hawkins dance with 2 8th graders separated - but with charge - establishes: an unequal distribution of charge with a positive outside of cell membrane and negative inside THERE ARE MORE K + leak Channels than NA+ established by : electrochemical gradients and permeability maintained: by NA K ATPase, sodium potassium ATPase this is what the thyroid hormone is signaling to, is the primary thermoregulation system in the body
graded potential vs action potential
-graded potential: small deviation from the resting membrane potential that makes the membrane either more polarized or less polarized; occurs when a stimulus causes mechanically-gated or ligand-gated channels to open or close in an excitable cell's plasma membrane -action potential (aka impulse): all or nothing response, no takebacks, propagated all the way through the cell and is fired - prior to it being fired, many little events of graded potential? a sequence of rapidly occurring events that decrease and reverse the membrane potential and then eventually restore it to the resting state; occurs in the axon of a neuron when depolarization reaches a certain level termed the threshold (-55mV)
Synapse of the reflex arc
-stimulus 1) receptor 2) sensory neuron 3)integration center 4) moto neuron 5) effector -response
Neurolemmocytes (Schwann cells)
1) myelinate axons in the PNS 2) allows for faster action potential propagation along an axon - act like oligodendrocytes
Progression of PNS nerve fiber (axons)
1) neurolemmocyte starts to wrap around 1 mm portion of axon - like cinnamon role 2) consecutive layers 3) Overlapping - myelin shift 4) neurilemma is the cytoplasm and nuclease of neurolemmocyte
how to establish a negative RMP?
1) suppose a cell only has K+ leak channels (always open) simply a facilitated diffusion example net efflux of + charge - membrane interior is more negative 2) now add one Na + leak channel, net influx of + charge, membrane interior is more positive answer: THERE ARE MORE K + leak Channels, K+ efflux (leading cell) > Na+ influx (into cell) 3) rinse and repeat 70x, to get RMP of -70 mV relative to external
Oligodendrocytes (CNS)
Myelinate several CNS axons; provide structural framework - white matter is myelinated axons - to improve nerve electrical velocity - damaging myelination can damage intelligence/communication
know any jokes about sodium? want to hear a joke about potassium? lead to potentials due to different concentrations in the plasma membrane, which lead to behaviors due to change in charge (current)
Na+ K+
which of the following membrane transporters are present throughout the membrane of a neuron?
Na+/K+ pumps sodium leak channels potassium leak channels
How to maintain a negative RMP?
Na-K ATPase, - 3 (loss of Na+) + 2 (gain of two K+) stable pumps ions against electro-chemical gradients
how do excitable cells perform work?
alter the resting state of PE in the RMP
The functions of astrocytes are to ______.
assist neuronal development help form the blood-brain barrier regulate the composition of interstitial fluid
Which glial cell occupies the space of dying neurons?
astrocytes
CNS glial cells
astrocytes, microglia, ependymal cells, oligodendrocytes
The presence of ______ ions causes the synaptic vesicles to bind to the membrane, allowing neurotransmitters to be released.
calcium
The total length of the axon is called the ___ segment
conductive
Which of the following are characteristics of neurons?
conductivity amitotic secretion extreme longevity excitability
Resting Membrane Potential (RMP)
direct message charge difference across the plasma membrane ready to do "work"
satellite cells
hang out in gangs - ganglions (posterior root ganglion) 1) electrically insulates PNS cell bodies 2) regulates nutrient and waste exchange for cell bodies in ganglia - goes from out to in neuron - sensory - act like astrocytes
The event that occurs when the inside of a cell becomes more negative than the resting membrane potential is called
hyperpolarization
f you were moving across a neuron's membrane from the receptive segment toward the transmissive segment, in the ______ is where would you first encounter large numbers of voltage-gated Na+ and K+ channels.
initial
efferent
motor, conveying away from the center (interneuron on spinal cord)
Nueron
nerve cell that carries messages throughout the body as electrical signals - specialized, action potentials - highly metabolic - constantly need O2 and glucose - usually amitotic- "new" neurons are rare
PNS glial cells
satellite cells and neurolemmocyte cells
Mechanical Potential Energy
stored energy; energy of position
Axon
the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands - one per neuron, arises from axon hillock (axillary region of an axon) - transmits AP away from cell body - axonal transport = anterograde (prox to distal) or retrograde (distal to proximal)
Synapse
the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron
Most sensory neurons are ______.
unipolar
______ are unique channels in that they have three states; resting, activation, and inactivation.
voltage gated channels
Astrocytes
- Most abundant, versatile, and highly branched glial cells - Cling to neurons, synaptic endings, and capillaries - control chemical environment by sensing any uptake, ingesting, to regulate solute in order to breakdown or continue uptake - forms blood brain barrier - mechanical support to neurons ASTRO MEANS STAR SHAPED
Dendrites
- receptive/numerous - a neuron's bushy, branching extensions that receive messages and conduct impulses toward the cell body (soma) - conduct graded/local potentials (not AP) which are short distance and have rapid signal decay
Which describes the propagation of depolarization down an axon?
The flow of Na+ to downstream regions causes depolarization of adjacent regions.
When more ion channels open, the electrical resistance of the membrane
decreases