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