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biopsychology > chapter 2 > Flashcards

chapter 2 Flashcards

1
Q

The human nervous system comprises of :

A

two kinds of cells
neurons
Glia

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2
Q

Human brain contains how many neurons ?

A

86 billions individual neurons

the numbers of neuron varies from person to person

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3
Q

Neurons do what ?

A

receive information and transmit it to other cells

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4
Q

What did santiago Ramon y Cajal discover in the 1800s?

A

used newly develop staining techniques to show that a small gap separate the tips of one neuron’s fibers from the surface of the next neuron.

(ppw) was the first to demonstrate that the individual cells comprising the nervous system remained separate
He showed that they did not merge into each other as previously believed

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5
Q

How is the neurons similar to other cells in the body ?

explain

A 
both have the following structures : 
Membrane
Nucleus
Mitochondria
Ribosomes
Endoplasmic reticulum
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6
Q

Membrnae (plasma membrane)

A

a structure that seperates the inside of the cells from the outside cell environment
Composed of 2 layers of fat molecules that are free to flow around one another

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7
Q

Nucleus

A

contains chromosomes

all cells have a nucleus except for RBC

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8
Q

Mitochondrion

A

the structure that performs metabolic activities , providing the energy that the cell require for all other activities.
Need fuel and o2 to function

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9
Q

Ribosomes

A

translates proteins

either free or attached to ER

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10
Q

ER

A

endoplasmic reticulum

thin tubes that transport newly synthesize proteins to other locations

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11
Q

A motor neuron

A

Has its soma in the spinal cord
Receives excitation from other neurons through its dendrites
Conducts impulses along its axon to a muscle or gland

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12
Q

Sensory neuron

A

Is specialized at one end to be highly sensitive to a particular type of stimulation (touch, light, sound, etc.)
The cells soma is located on a stalk off the main trunk of the axon.
view p.31 for pic

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13
Q

Dendrites

A

Branching fibers with a surface lined with synaptic receptors responsible for bringing information into the neuron (brings info in from other 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 shape of the dendrites can vary a lot from one neuron to another.

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14
Q

cell body/ soma

A

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

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15
Q

Axons

A

Thin fiber of a neuron responsible for transmitting nerve impulses toward other neurons, organs, or muscles
Maybe have a myelin sheath, an insulating material that contains interruptions in the sheath known as nodes of Ranvier
Presynaptic terminals at the end points of an axon release chemicals to communicate with other neurons
so, its crosses the junction between one neuron and the next.

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16
Q

Afferent axon

A

refers to bringing information into a structure

(anatomy, towards the spinal and hence towards the brain)

ex: Every sensory neuron is afferent, it brings the information gathered from the skin towards the spinal cord.
A for admission

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17
Q

efferent axon

A

refers to carrying information away from a structure

(anatomy, away from the spinal cord and towards a muscle or skin.

ex: hence, every muscle neuron is efferent to the spinal cord..
sends information to the muscle to contract.

“E” for exit

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18
Q

Interneurons or intrinsic neurons

A

are those whose dendrites and axons are completely contained within a single structure

ex: an intrinsic neuron of the thalamus has its axon and all its dendrites within the thalamus.

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19
Q

Neurons vary in size, shape, and function

The shape and function det..

A

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 and enables it to receive input from a huge number of axons.

in contrast, certain cells in the retina have only short branches on their dendrites and therefore pool input from only a few sources. (figure 2.9d)

Hence, neutrons with wider branching connect with more neurons.

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20
Q

Astrocytes

A

Help synchronize the activity of the axon by wrapping around the presynaptic terminal and taking up chemicals released by the axon
Responsible for dilating blood vessels to bring more nutrients into brain areas with heightened activity

book: astrocytes wraps around the presynaptic terminals of a group of functionally related axons.
It takes up chemical that are release by the axons and then releasing it back to the axons, an astrocytes helps to synchronize the activity of the axons enabling them to send messages in waves.

In addition, astrocytes helps remove waste material created when neuron dies and control the amount of blood flow to each brain area.

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21
Q

Microglia

A

Remove waste material, viruses, and fungi from the brain

Also remove dead, dying, or damaged neurons

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22
Q

oligodendrocytes
schwann cells

where are they situated

A

Oligodendrocytes (in the brain and spinal cord) and Schwann cells (in the periphery of the body)
Specialize type of glia that Build the myelin sheath that surrounds and insulates certain vertebrate axons

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23
Q

Radial glia

A

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

24
Q

what happens to radial glia cells when embryonic dev. finishes

A

When embryonic development finishes, most radial glia differentiate into neurons and a smaller number differentiate into astrocytes and oligodendrocytes

25
Q

oligodendrocytes produce what ?

vs swann cells

A

Oligodendrocytes produce myelin sheaths that insulate certain vertebrate axons in the central nervous system

Schwann cells have a similar function in the periphery.

26
Q

Astrocytes

does what ?

A

Looks like a star

Astrocytes pass chemicals back and forth between neurons and blood and among neighboring neurons.

27
Q

Microglia

A

proliferate in areas of brain damage and remove toxic materials

-very small cells
removes waste material as well as viruses, fungi and other microorganism.
They function like part of the immune system

28
Q

How an astrocytes synchronizes associated axons ?

A

Branches of the astrocyte (in the center) surround the presynaptic terminals of related axons. If a few of them are active at once, the astrocyte absorbs some of the chemicals they release. It then temporarily inhibits all the axons to which it is connected. When the inhibition ceases, all of the axons are primed to respond again in synchrony

29
Q

Blood brain barrier

what is it ?
And why we need it ?

A

A mechanism that surrounds the brain and blocks most chemicals from entering
The immune system destroys damaged or infected cells throughout the body.
(hence kills the cells that the virus has infected)
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.
This wall also blocks out most nutrients.

30
Q

How the blood brain barrier works

A

Depends on the arrangement of endothelial cells that form the walls of the capillaries.
Outside the brain, such cells are separated by small gaps but in the brain, they are joined so tightly that virtually nothing passes between them.
We dont have this type of barrier near the other organs since it keeps nutrients out too.

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, as can certain fat-soluble molecules (since it can dissolve in the fats of the membrane)

Active transport : systems pump glucose (brains main fuel) and amino acids across the membrane.

31
Q

what is Active transport

Problems for treatment for brain cancer.

A

The protein-mediated process that expends energy to pump chemicals from the blood into the brain
Glucose, certain hormones, amino acids, and a few vitamins are brought into the brain via active transport
The blood-brain barrier is essential to health, but can pose a difficulty in allowing chemicals such as chemotherapy to treat brain cancer to pass the barrier

32
Q

Nourishment of vertebrate neuron s

A

Vertebrate neurons depend almost entirely on glucose
A sugar that is one of the few nutrients that can pass through the blood-brain barrier
Neurons need a steady supply of oxygen
20 percent of all oxygen consumed by the body is used by the brain

The metabolic pathway that uses glucose requires oxygen; therefore, uses up a lot of O2.

33
Q

the body need what ?

what hapens when there is a deficiency ?

A

The body needs a vitamin, thiamine, to use glucose
Prolonged thiamine deficiency leads to death of neurons as seen in Korsakoff’s syndrome, a result of chronic alcoholism
Korsakoff’s syndrome is marked by severe memory impairment

chronic alcoholic have a diet deficient in thiamine.

34
Q

Nerve impulse

What is the speed of the impulse ?

A touch to the shoulder reach the brain first or a touch to the foot ?

Would you notice the delay ?

A

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 nerve impulses ranges from less than 1 meter/second to 100 meters/second
A touch on the shoulder reaches the brain more quickly than a touch on the foot

No, You will not notice that your brain receive one stimulus before the other.

35
Q

Vision

A

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 control are well adapted to the exact needs for information transfer in the nervous system

36
Q

Resting potential

A

Messages in a neuron develop from disturbances of the resting potential
At rest, the membrane maintains an electrical gradient known as polarization (meaning a difference in the electrical charge in 2 location)
A difference in the electrical charge inside and outside of the cell

The inside of the membrane is slightly negative with respect to the outside (approximately 70 millivolts)
The resting potential of a neuron refers to the state of the neuron prior to the sending of a nerve impulse

37
Q

what kind of permeability the membrane has

A

The membrane is selectively permeable, allowing some chemicals to pass more freely than others
Most large or electrically charged ions and molecules cannot cross the membrane at all.
Sodium, potassium, calcium, and chloride pass through channels in the membrane

38
Q

When membrane is at rest

A

When the membrane is at rest:
Sodium channels are closed
Potassium channels are partially closed allowing the slow passage of potassium

39
Q

Ion channels - Na/K pump

A

The sodium-potassium pump is a protein complex
Continually pumps three sodium ions out of the cells while drawing two potassium ions into the cell
Helps to maintain the electrical gradient
Uses active transport (requires ATP)

40
Q

electrical gradient vs concentration gradient

A

The electrical gradient and the concentration gradient—the difference in distributions of ions—work to pull sodium ions into the cell
The electrical gradient tends to pull potassium ions into the cells
However, they slowly leak out, carrying a positive charge with them

book:
Sodium is positively charged and the inside of the cells is negatively charged - electrical gradient
- Tends to pull sodium into the cell
2nd : sodium is more concentrated outside than inside , so it is more likely to enter the cell than to leave it. Concentration gradient.

Pottasium :
is positively charged and is attracted to the negative charge cell
2nd : potassium is more concentrated inside the cell , so the concentration gradient tend to drive it out .

41
Q

The sodium and potassium gradients for a resting membrane

A

Sodium ions are more concentrated outside the neuron, and potassium ions more concentrated inside. Protein and chloride ions (not shown) bear negative charges inside the cell. At rest, almost no sodium ions cross the membrane except by the sodium–potassium pump. Potassium tends to flow into the cell because of an electrical gradient but tends to flow out because of the concentration gradient. However, potassium gates retard the flow of potassium when the membrane is at rest.

42
Q

The resting potential remains stable until the neuron is stimulated

hyperpolarization
depolarization
threshold of excitation

A

Hyperpolarization: increasing the polarization or the difference between the electrical charge of two places
Depolarization: decreasing the polarization toward zero
The threshold of excitation: a level above which any stimulation produces a massive depolarization

43
Q

action potential

A

A rapid depolarization of the neuron
The action potential threshold varies from one neuron to another, but is consistent for each neuron
Stimulation of the neuron past the threshold of excitation triggers a nerve impulse or action potential

44
Q

Voltage-activated channels

A

Membrane channels whose permeability depends upon the voltage difference across the membrane
Sodium and potassium channels
When sodium channels are opened, positively charged sodium ions rush in and a subsequent nerve impulse occurs

45
Q

The movement of sodium and potassium ions during an action potential

A

Sodium ions cross during the peak of the action potential, and potassium ions cross later in the opposite direction, returning the membrane to its original polarization

After an action potential occurs, sodium channels are quickly closed
The neuron is returned to its resting state by the opening of potassium channels
Potassium ions flow out due to the concentration gradient and take with them their positive charge
The sodium-potassium pump later restores the original distribution of ions

46
Q

Restoring the Sodium-Potassium Pump

A

The process of restoring the sodium-potassium pump to its 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

47
Q

Blocking Sodium Channels

A

Local anesthetic drugs block sodium channels and therefore prevent action potentials from occurring
Example: Novocain and Xylocaine

48
Q

All or none law :

A

Action potentials back-propagate into the cell body and dendrites
Dendrites become more susceptible to structural changes responsible for learning
The all-or-none law
States that the amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiated it
Action potentials are equal in intensity and speed within a given neuron

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

49
Q

Refractory period

A

After an action potential, a neuron has a refractory period during which time the neuron resists the production of another action potential
The absolute refractory period: the first part of the period in which the membrane cannot produce an action potential
The relative refractory period: the second part, in which it takes a stronger than usual stimulus to trigger an action potential

50
Q

Propagation of an Action Potential

A

In a motor neuron, the action potential begins at the axon hillock (a swelling where the axon exits the soma)
Propagation of the action potential: the transmission of the action potential down the axon
The action potential does not directly travel down the axon

As an action potential occurs at one point on the axon, enough sodium enters to depolarize the next point to its threshold, producing an action potential at that point. In this manner the action potential flows along the axon, remaining at equal strength throughout. Behind each area of sodium entry, potassium ions exit, restoring the resting potential

51
Q

Myelin sheath

A

The myelin sheath of axons are interrupted by short unmyelinated sections called nodes of Ranvier
Myelin is an insulating material composed of fats and proteins
At each node of Ranvier, the action potential is regenerated by a chain of positively charged ions pushed along by the previous segment

52
Q

Saltotory conduction

A

The “jumping” of the action potential from node to node
Provides rapid conduction of impulses
Conserves energy for the cell

53
Q

Multiple sclerosis

A

disease in which the myelin sheath is destroyed

Associated with poor muscle coordination and sometimes visual impairments

54
Q

Local neurons

Is it difficult to study ? Why?

A

Have short axons, exchange information with only close neighbors, and do not produce action potentials
When stimulated, produce graded potentials—membrane potentials that vary in magnitude and do not follow the all-or-none law
Depolarize or hyperpolarize in proportion to the stimulation

Difficult to study due to their small size
Most of our knowledge has come from the study of large neurons
Myth
Only 10 percent of neurons are active at any given moment
Truth
You use all of your brain, even at times when you might not be using it very well

55
Q

Is the blood brain barrier essential to health >

A

Yes it is.
People who have alzheimer disease , their endothelial cells lining the brain blood vessels shrink and harmful chemicals can now enter the brain

biopsychology (6 decks)

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