PhysioPsych Chapter 2: Nerve Cells and Nerve Impulses

How many neurons does the average human brain have?

100 billion _______.

Schwann cells

(In the PNS) glia cells that build myelin sheaths SCN (Suprachiasmatic nucleus)

Presynaptic terminal

(end bulb or bouton) point where an axon releases chemicals

1 Presynaptic terminal

(end bulb or bouton) point where an axon releases chemicals 1

Nerve impulse

- The electrical message that is transmitted down the axon of a neuron; Does not travel directly down the axon, but is regenerated at points along the axon so that it is not weakened - The speed of this ranges from less than 1 meter/second to 100 meters/second - The brain is not set up to register small differences in the time of arrival of touch messages - However, in vision, movements must be detected as accurately as possible - The properties of impulse conduction are well adapted to the exact needs for information transfer in the nervous system

The inside of the membrane is slightly negative with respect to the outside, which is at approximately ____ millivolts.

-70 millivolts.

_______ _______ is the protein mediated process that expends energy to pump chemicals from the blood into the brain (such as glucose, certain hormones, amino acids, and vitamins).

Active transport.

____ help synchronize the activity of the axon by wrapping around the presynaptic terminal and taking up chemicals released by the axon.

Astrocytes.

The ______ _____ ______ is a mechanism that surrounds the brain and blocks most chemicals rom entering.

Blood Brain Barrier.

Oligodendrocytes are located in the _______ and _______ _____ while Schwann Cells are located in the _______ of the body.

Brain, Spinal Cord; Periphery.

Dendrites

Branching fibers with a surface lined with synaptic receptors responsible for bringing information into the neuron; Some also contain dendritic spines that further branch out and increase the surface area of the dendrite; The greater the surface area of the dendrite, the more information it can receive

The ______ ______ is transmitted down the axon of a neuron, and is regenerated at points along the axon so that it is not weakened.

Electrical Message.

What do vertebrate neurons depends on for energy and where do they get it?

Glucose, a sugar received from the blood brain barrier.

Where are oligodendrocytes located?

In the brain and spinal cord.

What are axons generally covered in?

Myelin sheathes with nodes of ranvier.

The _______ ________ demonstrates that the brain is not set up to register small differences in the time of arrival of touch messages. However, the properties of _____ ______ are well adapted to the exact needs for information transfer in the nervous system.

Nerve Impulse; Impulse control.

What two base kinds of cells is the human nervous system comprised of?

Neurons and Glia Cells.

What is the membrane of a neuron made of?

Phospholipid molecules and protein molecules.

What is at the end of a axon which releases chemicals to communicate with other neurons?

Presynaptic terminals.

Korsakoff's syndrome

Prolonged thiamine deficiency, common in chronic alcoholism, leads to death of neurons and a condition called Korsakoff's syndrome, marked by severe memory impairments.

______ _____ Guide the migration of neurons and the growth of their axons and dendrites during embryonic development.

Radial Glia.

What does a motor neuron (it's soma connected to the spinal cord) do?

Receives excitation from other neurons and conducts impulses along its axon to a muscle

The ______ _____ ______ maintains the electrical gradient.

Sodium Potassium Pump.

The ______ ______ _____ is a protein complex, continually pumping three sodium ions out of the cells while drawing two potassium ions into the cell, maintaining the electrical gradient.

Sodium Potassium Pump.

Which chemicals pass through channels in the neuron's membrane?

Sodium, potassium, calcium, and chloride.

Where in the neuron is the most responsible for metabolic work? (includes mitochondria)

Soma.

Why is chemotherapy difficult in batting brain cancer?

The Blood brain barrier keeps most chemicals out, thus that treatment is harder to do to beat cancer.

Fill in the Blank: The _______ separates the inside of the cell from the outside environment.

The Membrane.

Fill in the Blank: The _______ contains the chromosomes inside the cell.

The Nucleus

The _____ ____ tends to pull potassium ions into the cell.

The electrical gradient.

the opening of potassium channels; Potassium ions flow out due to the concentration gradient and take with them their positive charge

The neuron is returned to its resting state by_____

restores the original distribution of ions (takes time); An unusually rapid series of action potentials can lead to a buildup of sodium within the axon- Can be toxic to a cell, but only in rare instances such as stroke and after the use of certain drugs

The sodium-potassium pump later_____

T/F: a sensory neuron has a soma.

True. Both Motor neurons and Sensory Neurons have soma/Cell bodies, but they aren't always located in the same place.

T/F: The greater the surface area of the dendrite, the more information it can receive.

True. The more dendrites available for receiving information, the more potential neuron impulses will travel down those dendrites from other neurons.

Glucose

a simple sugar; vertebrate neurons depend almost entirely on glucose; Because metabolizing glucose requires oxygen, neurons need a steady supply of oxygen;

The all-or-none law states that ____. a. a neuron produces an action potential of maximal strength, or none at all b. all neurons fire or none at all c. all neurons in a pathway fire at the same time, or none do d. all ions move in the same direction, or none do

a. a neuron produces an action potential of maximal strength, or none at all

The net effect of each cycle of the sodium-potassium pump is to ____. a. decrease the number of positively charged ions within the cell b. increase the number of positively charged ions within the cell c. decrease the number of positively charged ions outside the cell d. increase the number of negatively charged ions within the cell

a. decrease the number of positively charged ions within the cell

An axon has many branches, each of which swells at its tip. These are known as ____. a. presynaptic terminals b. efferent axons c. afferent axons d. intrinsic neurons

a. presynaptic terminals

1 Myelinated axons

axons covered with myelin sheaths

Myelinated axons

axons covered with myelin sheaths

Which type of glia builds myelin sheaths around axons in the periphery of the body? a. astrocytes b. Schwann cells c. oligodendrocytes d. radial glia

b. Schwann cells

What do neurons have that other cells do not? a. a plasma membrane b. large, branching extensions c. protein channels d. an endoplasmic reticulum

b. large, branching extensions

Protein channels allow ____ molecules to cross the cell membrane. a. large charged b. small charged c. large uncharged d. small uncharged

b. small charged

How do Astrocytes synchronize the activity of the axon?

by wrapping around the presynaptic terminal and taking up chemicals released by the axon.

What type of neuron in the pons receives information only from other cells in the pons and sends information only to other cells in the pons? a. afferent b. efferent c. intrinsic d. inter-synaptic

c. intrinsic

1 Neurons

cells that receive information and transmit it to other cells 1

Neurons

cells that receive information and transmit it to other cells; The human brain contains approximately 100 billion individual neurons; 16 billions in Cerebral cortex, 69 billions in Cerebellum, Less than 1 billion in the rest of the brain, and 1 billion in spinal cord - their shape is distinctive compared to other

After the peak of an action potential, what prevents sodium ions from continuing to enter the cell? a. There is no longer a concentration gradient for sodium. b. The sodium-potassium pump greatly increases its rate of activity. c. All the available sodium ions have already entered the cell. d. The sodium gates in the membrane close.

d. The sodium gates in the membrane close.

When a neuron is at rest, what is primarily responsible for moving potassium ions into the cell? a. concentration gradient b. an electrical gradient c. the sodium-potassium pump d. both the sodium-potassium pump and electrical gradient

d. both the sodium-potassium pump and electrical gradient

Electrical gradients lead to the ____. a. general movement of ions into the neuron b. general movement of ions out of the neuron c. movement of ions to areas having the same electrical charges d. movement of ions to areas having opposite electrical charges

d. movement of ions to areas having opposite electrical charges

What will most affect the speed of an action potential? a. the strength of the stimulus b. the time since the last action potential c. the length of the axon d. the resistance of the membrane

d. the resistance of the membrane

Why does the body need thiamine?

it is so the body can brain down and use glucose, a vital source of energy for vertebrate neurons.

Sodium-potassium pump

mechanism that actively transports sodium ions out of the cell while drawing in two potassium ions

Sodium-potassium pump

mechanism that actively transports sodium ions out of the cell while drawing in two potassium ions; 3 Na out and 2 K in; - Helps to maintain the electrical gradient; - When the membrane is at rest:-Sodium channels are closed. - Potassium channels are partially closed allowing the slow passage of potassium

Voltage-gated channel

membrane channel whose permeability to sodium (or some other ion) depends on the voltage difference across the membrane

All-or-none law

principle that the amplitude and velocity of an action potential are independent of the stimulus that initiated it; - Action potentials are equal in intensity and speed within a given neuron.

Dendritic spines

short outgrowths that increase the surface area available for synapses; includes of shaft and spine

Depolarize (depolarization)

to reduce polarization toward zero across a membrane

What is the difference between a sensory neuron and a motor neuron?

A ______ ________ is specialized at one end to be highly sensitive to a particular type of stimulation (touch, light, sound, etc.). A _______ _________ receives excitation from other neurons and conducts impulses along its axon to a muscle, which allows for muscle movement and contraction.

At rest, the membrane maintains an ________ ______ called polarization, which is the difference in the ______ ______ inside and outside of the cell.

Electrical Gradient; Electrical charge.

Potassium enters the cell through channels because of the ______ ______

Electrical gradient.

Biological Psychology

Is the study of the psychological, evolutionally, developmental mechanism of behaviors and experience; Seeks biological explanations of behaviors

What are the 5 baseline structures in both neurons and in normal animal cells?

Membrane, Nucleus, Mitochondria, Ribosomes, Endoplasmic Reticulum.

Variations among neurons

Neurons vary in size, shape, and function; The shape of a neuron determines it connection with other neurons and its contribution to the nervous system; The function is closely related to the shape of a neuron - Example: Purkinje cells of the cerebellum branch extremely widely within a single plane; Bipolar neurons in the retina have only short branches, and some receive input from as few as two other cells.

Absolute refractory period

a time when the membrane is unable to produce an action potential

Which type of glia release chemicals that modify the activity of neighboring neurons? a. astrocytes b. Schwann cells c. oligodendrocytes d. radial glia

a. astrocytes

Which type of glia remove waste material in the nervous system? a. astrocytes b. Schwann cells c. oligodendrocytes d. radial glia

a. astrocytes

Nodes of Ranvier are ____. a. gaps in the myelin of axons b. also known as myelin sheath c. spiny outgrowths on dendrites d. responsible for cell metabolism

a. gaps in the myelin of axons

Radial glia ____. a. guide the migration of neurons during embryonic development b. synchronize the activity of axons c. wrap around the presynaptic terminals of several axons d. build the myelin sheaths that surround and insulate certain axons

a. guide the migration of neurons during embryonic development

Selective permeability

ability of some chemicals to pass more freely than others through a membrane; Sodium, potassium, calcium, and chloride pass through channels in the membrane

Action potential

all-or-none message sent by an axon; Action potentials can backpropagate into the cell body and dendrites -Dendrites become more susceptible to structural changes responsible for learning - Action potentials vary from one neuron to another in terms of amplitude, velocity, and shape - Studies of mammalian axons show that there is much variation in the types of protein channels and therefore in the characteristics of the action potentials

Myelin

an insulating material composed of fats and proteins

1 Myelin

an insulating material composed of fats and proteins 1

Dendrites ____. a. contain the nucleus, ribosomes, and other structures found in most cells b. are branching fibers that get narrower near their ends c. are thin fibers of constant diameter d. are an insulating material that cover an axon

b. are branching fibers that get narrower near their ends

Ordinarily, stimulation of a neuron takes place ____. a. through hyperpolarization b. at the synapse c. in the mitochondria d. in the endoplasmic reticulum

b. at the synapse

What is the main source of nutrition for vertebrate neurons? a. fats b. glucose c. sodium d. complex carbohydrates

b. glucose

During the relative refractory period, the ____. a. sodium gates are firmly closed b. sodium gates are reverting to their usual state c. sodium gates are wide open d. potassium gates are firmly closed

b. sodium gates are reverting to their usual state

What occurs when depolarization is less than the cell's threshold? a. Sodium is prevented from crossing the membrane. b. Potassium is prevented from crossing the membrane. c. Sodium crosses the membrane only slightly more than usual. d. The cell will still produce an action potential.

c. Sodium crosses the membrane only slightly more than usual.

Which of the following is an advantage of having a resting potential? a. The toxic effects of sodium are minimized inside the cell. b. No energy is required to maintain it. c. The cell is prepared to respond quickly to a stimulus. d. All of the ions are maintained in equal concentrations throughout the cytoplasm.

c. The cell is prepared to respond quickly to a stimulus.

As compared to dendrites, axons usually ____. a. form the information-receiving pole of the neuron b. are shorter in length c. are covered with myelin d. taper in diameter toward their periphery

c. are covered with myelin

As a general rule, axons convey information ____. a. toward dendrites of their own cell b. toward their own cell body c. away from their own cell body d. to surrounding glia

c. away from their own cell body

1 Radial glia

cells that guide the migration of neurons and the growth of axons and dendrites during embryological development

Radial glia

cells that guide the migration of neurons and the growth of axons and dendrites during embryological development

Which action would depolarize a neuron? a. decreasing membrane permeability to calcium b. increasing membrane permeability to potassium c. decreasing membrane permeability to sodium d. increasing membrane permeability to sodium

d. increasing membrane permeability to sodium

Molecules that can cross the blood-brain barrier are usually ____. a. large, uncharged molecules, such as lactose b. large, charged molecules c. neurotransmitters, such as dopamine d. molecules that can dissolve in the fats of the capillary walls

d. molecules that can dissolve in the fats of the capillary walls

Why does the brain need thiamine? a. to enable glucose to cross the blood-brain barrier b. as a source of fuel in case there is not enough glucose c. as a building block for making proteins d. to enable it to metabolize glucose

d. to enable it to metabolize glucose

The ______ ______ and the _______ _______ (the difference in distributions of ions) work to pull sodium ions into the cell

electrical gradient ; concentration gradient.

Hyperpolarization

increasing polarization across a membrane

1 Myelin sheath

insulating material that covers vertebrate axon

Myelin sheath

insulating material that covers vertebrate axon; contains interruptions in the sheath known as nodes of Ranvier

Interneuron

neuron whose axons and dendrites are all confined within a given structure 1

1 Ribosomes

sites for cell synthesization of new protein molecules

Saltatory conduction

the jumping of action potentials from node to node

Three principles of action potentials and the neuron

1. At the start, sodium ions are mostly outside the neuron, and potassium ions are mostly inside. 2. When the membrane is depolarized, sodium and potassium channels in the membrane open. 3. At the peak of the action potential, the sodium channels close.

____s are thin fibers of a neuron responsible for transmitting nerve impulses toward other neurons, organs, or muscles. May have a myelin sheath.

Axon

Neurons typically have one ____ but many ______.

Axon; Dendrites.

What is responsible for transmitting nerve inmpuses to other neurons, organs, or muscles?

Axons.

When the membrane is at rest, the sodium channels are _____, and potassium channels are ______ _____, allowing the slow passage of potassium.

Closed; partially closed.

The reason why Potassium leaves the cells through potassium channels is because of the ______ _______.

Concentration gradient.

The membrane of a neuron

Contains phosopholipid molecules and protein molecules

The four main components of all Neurons are ______, ____/Cell body, _____, and ________ _______.

Dendrites, Soma, Axon, Presynaptic Terminals.

Fill in the Blank: The _______ ________ is a network of thin tubes that transports newly synthesized proteins from the ribosomes to their location within the cell.

Endoplasmic Reticulum

Local neurons

Have short axons, exchange information with only close neighbors, and do not produce action potentials; When stimulated, produce graded potentials; Difficult to study due to their small size; Most of our knowledge has come from the study of large neurons. They are neurons without a normal axon.

Axon hillock

In a motor neuron, the action potential begins at the axon hillock (a swelling where the axon exits the soma)

Santiago Ramón y Cajal (1852-1934)

In the late 1800s, HE was the first to demonstrate that the individual cells comprising the nervous system remained separate- they did not merge into each other

What is the soma covered in?

It is covered with Synapses on its surface.

What is a sensory neuron for?

It is specialized at one end to be highly sensitive to a particular type of stimulation (touch, light, sound, etc.)

How the Blood-Brain Barrier Works

Most large molecules and electrically charged molecules cannot cross from the blood to the brain; A few small, uncharged molecules such as O2 and CO2 cross easily; Active transport systems pump glucose and amino acids across the membrane

A _______ _________ receives excitation from other neurons and conducts impulses along its axon to a muscle, which allows for muscle movement and contraction.

Motor Neuron.

Fill in the Blank: A ______ ______ has its soma in the spinal cord, receives excitation from other neurons, and conducts impulses along its axon to a muscle.

Motor Neuron.

The Cell body/Soma contains the ______, ________, and _______.

Nucleus, Mitochondria, Ribosomes.

______________ build the myelin sheath that surrounds and insulates certain vertebrate axons in the brain and spinal cord.

Oligodendrocytes

Methods for recording activity of a neuron

Researchers measure the resting potential by inserting a very thin microelectrode into the cell body; The diameter of the electrode must be small enough to enter without damaging the cell. The most common electrode is a fine glass tube filled with a salt solution, tapering to a tip diameter of 0.0005 mm or less. A reference electrode outside the cell completes the circuit

The messages in a neuron develop from disturbances of the _______ _______ of a neuron.

Resting Potential.

The ______ _______ of a neuron refers to the state of the neuron ______ the sending of a nerve impulse.

Resting Potential; prior to

__________ build the myelin sheath that surrounds and insulates certain vertebrate axons in the periphery of the body.

Schwann cells

A ______ ________ is specialized at one end to be highly sensitive to a particular type of stimulation (touch, light, sound, etc.).

Sensory Neuron

Medical breakthroughs of blood-brain barrier

Some viruses, e.g. reovirus, when injected directly into the bloodstream, can cross the blood-brain barrier. - Used to reach tumors inside the brain. - Once inside, it replicates cancer cells and activates the immune system to attack and kill all cancer cells

Na+ channels open, Na+ begins to enter cell Which step of the action potential is this?

Step 1 of the action potential

Na+ channels open, Na+ begins to enter cell K+ channels open, K+ begins to leave cell Na+ channels become refractory, no more Na+ enter cells K+ continues to leave cell, causes membrane potential to return to resting level K+ channels close, Na+ channels reset Extra K+ outside diffuses away

Step 1 of the action potential Step 2 of the action potential Step 3 of the action potential Step 4 of the action potential Step 5 of the action potential Step 6 of the action potential

K+ channels open, K+ begins to leave cell Which step of the action potential is this?

Step 2 of the action potential

Na+ channels become refractory, no more Na+ enter cells Which step of the action potential is this?

Step 3 of the action potential

K+ continues to leave cell, causes membrane potential to return to resting level Which step of the action potential is this?

Step 4 of the action potential

K+ channels close, Na+ channels reset. Which step of the action potential is this?

Step 5 of the action potential

Extra K+ outside diffuses away

Step 6 of the action potential

Fill in the Blank: The ________ performs metabolic activities and provides energy that the cell requires.

The Mitochondrion / Mitochondria.

The _______ _____ are at the end points of an axon, and release chemicals to communicate with other neurons.

The Presynaptic Terminals.

Fill in the Blank: The _______ are sites within the cell that synthesizes new protein molecules.

The Ribosomes.

Where does the motor neuron have it's soma?

The Spinal Cord.

What are the branching fibers of dendrites used for?

The branching fibers' surfaces are lined with synaptic receptors and are responsible for bringing information into the neuron from presynaptic terminals of other neurons.

Graded potential

a membrane potential that varies in magnitude in proportion to the intensity of the stimulus; do not follow the all-or- none law; Depolarize or hyperpolarize in proportion to the stimulation

Active transport

a protein-mediated process that expends energy to enable a molecule to cross a membrane; Glucose, certain hormones, amino acids, and a few vitamins e.g. iron, A, and D, are brought into the brain via active transport

The neuron will produce an action potential only if the depolarization exceeds the ____. a. Threshold of excitation b. the resting potential c. hyperpolarization d. the refractory period

a. Threshold of excitation

What causes potassium ions to leave the axon just after the peak of the action potential? a. a continuing concentration gradient and the opening of the potassium gates b. an increase in the concentration gradient across the membrane c. an increased tendency of the sodium-potassium pump to push potassium out d. binding of potassium ions to proteins that leave at this time

a. a continuing concentration gradient and the opening of the potassium gates

When a membrane is at rest, what attracts potassium ions to the inside of the cell? a. an electrical gradient b. a concentration gradient c. both an electrical gradient and a concentration gradient d. neither an electrical gradient nor a concentration gradient

a. an electrical gradient

A presynaptic terminal is also known as ____. a. an end bulb b. a node of Ranvier c. myelin d. a spine

a. an end bulb

Which action will produce a hyperpolarization of a neuron? a. applying a negative charge inside the neuron with a microelectrode b. applying a positive charge inside the neuron with a microelectrode c. increasing the membrane's permeability to sodium d. decreasing the membrane's permeability to potassium

a. applying a negative charge inside the neuron with a microelectrode

When a neuron's membrane is at rest, the concentration gradient tends to move sodium ____ the cell and the electrical gradient tends to move it ____ the cell. a. into; into b. into; out of c. out of; into d. out of; out of

a. into; into

Korsakoff's syndrome ____. a. is marked by severe memory impairments b. results from too much thiamine c. results from lack of oxygen to the brain d. is due to a breakdown of the blood-brain barrier

a. is marked by severe memory impairments

The resting potential is mainly the result of ____. a. negatively charged proteins inside the cell b. positively charged proteins inside the cell c. negatively charged proteins outside the cell d. positively charged proteins outside the cell

a. negatively charged proteins inside the cell

When the potential across a membrane reaches threshold, the sodium channels ____. a. open to let sodium enter the cell rapidly b. close to prevent sodium from entering the cell c. open to let sodium exit the cell rapidly d. close to prevent sodium from exiting the cell

a. open to let sodium enter the cell rapidly

The action potential of a neuron depends mostly on what movement of ions? a. sodium ions entering the cell b. sodium ions leaving the cell c. potassium ions entering the cell d. potassium ions leaving the cell

a. sodium ions entering the cell

Afferent axon

axon that brings information into a structure

The concentration gradient refers to the ____. a. fact that the concentration of ions is greater on the inside of a neuron b. fact that the concentration of ions is greater on the outside of a neuron c. difference in distribution for various ions between the inside and outside of the membrane d. negatively charged proteins inside the cell

c. difference in distribution for various ions between the inside and outside of the membrane

Under which conditions would the sodium-potassium pump likely be far less effective in creating a concentration gradient? a. if dendrites were generally longer than axons b. if the glia-to-neuron ratio were higher c. if selective permeability of the membrane did not exist d. if it were an active transport system that required energy

c. if selective permeability of the membrane did not exist

At the peak of the action potential, the electrical gradient of potassium ____. a. is the same as during the resting potential b. pulls sodium into the cell c. pushes potassium out of the cell d. pulls potassium into the cell

c. pushes potassium out of the cell

Resting potential

condition of a neuron's membrane when it has not been stimulated or inhibited; Inside = slightly negative (-70mv) - refers to the state of the neuron prior to the sending of a nerve impulse

The resting potential of a neuron refers to the ____. a. net positive charge on the inside of the neuron b. ions which rest in one place in the cell c. movement of ions to the outside of the neuron d. net negative charge on the inside of the neuron

d. net negative charge on the inside of the neuron

Local anesthetic drugs attach to the sodium channels of the membrane, which ____. a. allows sodium ions to enter and stop action potential b. prevents potassium ions from entering and stopping action potential c. allows potassium ions to enter and stop action potential d. prevents sodium ions from entering and stopping action potential

d. prevents sodium ions from entering and stopping action potential

The idea that a neuron's membrane is polarized refers to a difference in electrical potential between ____. a. the axons and the dendrites b. the axon hillock and the cell body c. sodium ions and potassium ions d. the inside and the outside of the membrane

d. the inside and the outside of the membrane

What is one major cause for the resting potential of a neuron's membrane? a. a difference in size between axons and dendrites b. a high permeability of the membrane to water molecules c. the refractory period of the membrane d. the sodium-potassium pump

d. the sodium-potassium pump

1 Purkinje cell

flat cells in sequential planes, in the cerebellar cortex, parallel to one another

Schwann cells

glia cells that build myelin sheaths

Oligodendrocytes

glia cells that build myelin sheaths (In the CNS)

1 Oligodendrocytes

glia cells that build myelin sheaths 1

1 Nodes of Ranvier

interruptions in the myelin sheath of vertebrate axons 1

Nodes of Ranvier

interruptions in the myelin sheath of vertebrate axons; At each node of Ranvier, the action potential is regenerated by a chain of positively charged ions pushed along by the previous segment.

How does an astrocyte synchronize associated axons?

it connects to the synapse enveloped by astrocyte and receives signals from many neurons and sends those signals back out to other connected neurons.

Voltage-gated channels

membrane channel whose permeability to sodium (or some other ion) depends on the voltage difference across the membrane

_______ in the brain generally do not regenerate, thus having the ______ ______ _____ is vitally important.

neurons; blood brain barrier.

After an action potential occurs, sodium channels are_____

quickly closed

Ribosomes

sites for cell synthesization of new protein molecules Ritalin

Astrocytes

star-shaped glia that synchronize the activity of the axons by wrapping around the presynaptic terminal and taking up chemicals released by the axon; If a few of associated axons are active at once, the astrocyte absorbs some of the chemicals they release and then temporarily inhibits all the axons

Cell body (soma)

structure containing the nucleus, ribosomes, and mitochondria

Soma (cell body)

structure containing the nucleus, ribosomes, and mitochondria; Responsible for the metabolic work of the neuron; Covered with synapses on its surface in many neurons

1 Nucleus

structure that contains the chromosomes 1

Nucleus

structure that contains the chromosomes; Cell brain

1 Mitochondrion

structure that performs metabolic activities 1

Mitochondrion

structure that performs metabolic activities; takes in nutrients, breaks them down, and creates energy rich molecules for the cell. - have its own genes

Membrane

structure that separates the inside of the cell from the outside environment

Membrane(plasma membrane)

structure that separates the inside of the cell from the outside environment; selectively permeable

Axon

thin fiber of constant diameter; the neuron's information sender; The axon conveys an impulse toward other neurons, an organ, or a muscle; Axons can be more than a meter in length; Presynaptic terminals at the end points of an axon release chemicals to communicate with other neurons; maybe have a myelin sheath

Relative refractory period

time after the absolute refractory period that requires a stronger stimulus to initiate an action potential

Refractory period

time when the cell resists the production of further action potentials

1 Refractory period

time when the cell resists the production of further action potentials 1

What is the job of the Microglia?

to remove waste material, viruses, and fungi from the brain.

Propagation of the active potential

transmission of an action potential down an axon

Glia

type of cell in the nervous system that, in contrast to neurons, does not conduct impulses over long distances

Glia (neuroglia)

type of cell in the nervous system that, in contrast to neurons, does not conduct impulses over long distances; "glue"; non-neuronal cells; maintain homeostasis, form myelin, and provide support and protection for neurons in the CNS and PNS

Thiamine

vitamin, necessary to use glucose

Blood-brain barrier

A mechanism that surrounds the brain and blocks most chemicals from entering; Because neurons in the brain generally do not regenerate, it is vitally important for the blood brain barrier to block incoming viruses, bacteria, or other harmful material from entering

The problem of the blood-brain barrier

The blood-brain barrier is essential to health, but can pose a difficulty in allowing chemicals such as chemotherapy for brain cancer to pass the barrier

When the neuronal membrane is at rest, the potassium channels ____. a. permit potassium ions to pass quickly and easily b. permit potassium ions to pass slowly c. prohibit any movement of potassium ions d. help to open up the sodium channels

b. permit potassium ions to pass slowly

Neurons differ most strongly from other body cells in their ____. a. temperature b. shape c. osmotic pressure d. mitochondria

b. shape

The major disadvantage of a blood-brain barrier is that ____. a. many chemicals can easily diffuse into the brain b. so much glucose is required to maintain it c. certain required chemicals must be actively transported d. viruses cannot escape

c. certain required chemicals must be actively transported

In the normal course of an action potential, ____. a. sodium channel remain open for long periods of time b. the concentration of sodium equalizes across the membrane c. sodium remains much more concentrated outside than inside the neuron d. subthreshold stimulation intensifies the action potential

c. sodium remains much more concentrated outside than inside the neuron

Microglia

cells that remove waste material (dead cells and weak synapses...) and other microorganisms such as viruses and fungi from the nervous system

The speed of an action potential down an unmyelinated axon is best described as ____. a. the speed of electricity, regardless of the size of the axon b. less than 1 meter per second, regardless of the size of the axon c. faster in thin axons than in thick ones d. faster in thick axons than in thin ones

d. faster in thick axons than in thin ones

The concentration gradient for potassium tends to ____. a. draw potassium into the cell b. push chloride out of the cell c. push sodium out of the cell d. push potassium out of the cell

d. push potassium out of the cell

What structure is composed of two layers of fat molecules that are free to flow around one another? a. the endoplasmic reticulum b. a ribosome c. a mitochondrion d. the membrane

d. the membrane

Depolarization

decreasing polarization toward zero across a membrane Depression

Concentration gradient

difference in distribution of ions across the neuron's membrane; tends to push potassium ions out of the cell and pulls sodium ions into the cell

Electrical gradient (polarization)

difference in electrical charges between the inside and outside of the cell (membrane); tends to pull potassium and sodium ions into the cell

Multiple sclerosis

disease in which the myelin sheath is destroyed; Associated with poor muscle coordination and sometimes visual impairments.

Local anesthetic

drug that attaches to the sodium channels of the membrane, stopping action potentials (ex. Novocain and Xylocaine)

Local anesthetics

drugs that attach to the sodium channels of the membrane, stopping action potentials

Threshold

minimum amount of membrane depolarization necessary to trigger an action potential; A rapid depolarization of the neuron will occur after reaching the threshold of excitation

Endoplasmic reticulum

network of membranous thin tubes that transport newly synthesized proteins to other locations; functions as a manufacturing and packaging system

Efferent axon

neuron that carries information away from a structure

Sensory neuron

neuron that is highly sensitive to a specific type of stimulation

1 Motor neuron

neuron that receives excitation from other neurons and conducts impulses to a muscle

Motor neuron

neuron that receives excitation from other neurons and conducts impulses to a muscle; Has its soma in the spinal cord

Interneuron (intrinsic neuron)

neuron whose axons and dendrites are all confined within a given structure