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HAN 200 > Chapter 11 > Flashcards

Chapter 11 Flashcards

1
Q

Functions of the Nervous System

A
  1. Sensory input: (afferent neuron)
    - > info gathered by sensory receptors about internal and external changes
  2. Integration: (interneuron)
    - > interpretation of sensory input
  3. Motor output: (efferent neuron)
    - > activation of effector organs (muscles & glands) produces a response
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2
Q

Divisions of the Nervous system

A

CNS:

  • > Brain & spinal cord
  • > command center

PNS:

  • > paired spinal and cranial nerves carry messages to and from the CNS
  • > 2 directions
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3
Q

PNS

A

Two functional divisions:

  1. Sensory (afferent) division (to the brain)
    - >SOMATIC afferent fibers- convey impulses from skin, skeletal muscles, and joints

-> VISCERAL afferent fibers-convey impulses from visceral organs

  1. Motor (efferent) division (away from brain)
    - >Transmits impulses from the CNS to effector organs (muscles & glands)
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4
Q

Motor division of PNS

A
  1. Somatic (voluntary) nervous system
    - > conscious control of skeletal muscles
  2. Autonomic (involuntary) nervous system (ANS)
    - > regulates smooth muscle, cardiac muscle, and glands
    - > 2 functional subdivisions: Sympathetic & parasympathetic
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5
Q

Nervous tissue

A

2 principle cell types:
1. Neurons- exitable cells that transmit electrical signals

  1. Neuroglia (glial cells)-supporting cells:
    - > Astrocytes (CNS)
    - > Microglial (CNS)
    - > Ependymal (CNS)
    - > Oligodendrocytes (CNS)
    - > Schwann cells (PNS)
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6
Q

Neurons

A
  • > have extreme longevity. Given good nutrition can last a lifetime
  • > Amitotic
  • > High metabolic rate & require continous and abundant supplies of oxygen
  • > the plasma membrane of the cell body acts as part of the receptive region that receives info from other neurons.
  • > cell body is the major biosynthetic center and metabolic center of a neuron
  • > includes mitochondria, golgi app, rough ER (also called the chromatophilic substance), free ribosomes.
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7
Q

Most neuron cell bodies are located in the CNS, where they are protected by the bones of the skull and vertebral column. Clusters of cell bodies in the CNS are called NUCLEI/ NUCLEUS

A

TRUE!

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8
Q

Cell bodies that lie along the nerves in the PNS are called ganglia

The PNS consists chiefly of neuron processes (whose cell bodies are in the CNS)

A

TRUE!

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9
Q

2 types of neuron processes

A

dendrites and axons

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10
Q

Dendrites

A

of motor neurons are short, tapering, diffusely branching extensions.

  • > the main receptive or input regions, provide an enormous surface area for receiving signals from other neurons
  • > dendritic spines: thorny appendages with bulbous or spiky ends- which represent points of close contact (synapses) w/ other neurons
  • > convey incoming messages toward the cell body. These electrical signals are usually not action potentials (nerve impulses) but are short-distance signals called GRADED POTENTIALS
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11
Q

The axon

A
  • > neuron never has more than 1
  • > arises from a cone shaped area of the cell body caled the axon hillock
  • > any long axon is also called a nerve fiber
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12
Q

Tract

A

a bundle of axons in the CNS

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13
Q

Nerve

A

A bundle of axons in the PNS

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14
Q

The axon: functional characteristics

A
  • > The conducting region of the neuron
  • > generates nerve impulses and transmits them, typically away from the cell body, along the plasma membrane, or axolemma
  • > when the impulse reaches the axon terminals it causes neurotransmitters-signaling chemicals- to be released in the extracellular space
  • > neurotransmitters either excite or inhibit neurons (muscle or gland cells) with which the axon is in close contact.
  • > neuron receives and sends signals to other neurons, carrying on “conversations” with many different neurons at the same time
  • > axon LACKS rough ER and golgi apparatus- the structures involved with protein synthesis and packaging
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15
Q

What does an axon depend on?

A
  • > Its cell body to renew the necessary proteins and membrane components
  • > efficient transport mechanisms to distribute them
  • > axons quickly decay if cut or damaged bad
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16
Q

Axonal transport

A
  • > Anterograde movement: movement away from the cell body.
  • > Retrograde movement: Movement toward the cell body. Important means of intracellular communication, allows the cell body to be advised of conditions at the axon terminals. Also delivers vesicles to the cell body containing signal molecules (such as nerve growth factor)
  • > Bidirectional transport mechanism is responsible for axonal transport. Uses different ATP-dependent “motor” proteins (kinesin or dynein), depending on direction
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17
Q

Myelin sheath

A
  • > whitish, fatty (protein-lipoid) segmented myelin sheath
  • > protects and electrically insulates fibers, and it increases the transmission speed of nerve impulses
  • > myelin sheaths are only associated with axons.
  • > dendrites are NONmyelinated
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18
Q

Myelination in the PNS

A

-> formed by schwann cells

-
>indent to recieve an axon and then wrap themselves around it in a jelly roll fashion

  1. A schwann cell envelops an axon
  2. The schwann cell then rotates around the axon, wrapping its plasma membrane loosely around it in successive layers
  3. the schwann cell cytoplasm is forced between the membranes. The tight membrane wrappings surrounding the axon form the myelin sheath
    - >plasma membranes of mylinating cells contain much less protein than those of most body cells.
    - > adjacent schwann cells do not touch one another so there are gaps in the sheath. These myelin sheath gaps or nodes of Ranvier occur along a myelinated axon. Axon collaterals can emerge at these gaps
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19
Q

Schwann cells (PNS)

A
  • > Surround peripheral nerve fibers and form myelin sheaths

- >Vital to regeneration of damaged peripheral nerve fibers

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20
Q

Myelination in the CNS

A
  • > oligodendrocytes form myelin sheath
  • > myelin sheaths in the CNS lack an outer collar of perinuclear cytoplasm bc cell extensions do the coiling and the squeezed out cytoplasm is forced back toward the centrally located nucleus instead of peripherally
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21
Q

Multipolar neurons

A

have 3 or more processes- one axon and the rest dendrites. major type in CNS

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22
Q

Bipolar neurons

A

have 2 processes- an axon and a dendrite-that extend from opposite sides of the cell body. rare neurons. found in some of the special sense organs such as in the retina of the eye and in the olfactory mucosa

very rare

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23
Q

Unipolar neurons

A

have a single short process that emerges from the cell body and divides T-like into proximal and distal branches. The distal peripheral process is often associated with a sensory receptor. The central process enters the CNS. Unipolar neurons are more accurately called pseudounipolar neurons because they originate as bipolar neurons

  • > found mainly in the PNS. common only in dorsal root ganglia of the spinal cord and sensory ganglia of cranial nerves
  • > in place of dendrites unipolar neurons have “receptive endings” (sensory terminals) at the end of the peripheral process
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24
Q

Sensory or afferent neurons

A

transmit impulses from sensory receptors in the skin or internal organs toward or into the CNS

-> all sensory neurons are unipolar, and their cell bodies are located in sensory ganglia outside the CNS

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25
Q

Motor or efferent neurons

A

carry impulses away from the CNS to the effector organs (muscles and glands) of the body.

->multipolar

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26
Q

Interneurons or association neurons

A

lie between motor and sensory neurons in neural pathways and shuttle signals through the CNS pathways where integration occurs

->almost all are multipolar

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27
Q

White matter

A

dense collections of myelinated fibers (tracts)

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28
Q

Gray matter

A

mostly neuron cell bodies and unmyelinated fibers

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29
Q

voltage

A

the measure of potential energy generated by seperated electrical charges

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30
Q

potential difference

A

voltage measured between 2 points

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31
Q

current

A

the flow of electrical charge from one point to another is a current and it can be used to do work

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32
Q

the amount of charge that moves between 2 points depends on 2 factors: voltage and resistance

A
  • > substances with high electrical resistance are insulators

- >substances with low resistance are conductors

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33
Q

3 main types of gated channels

A
  • > chemically gated channels
  • > voltage-gated channels
  • > mechanically gated channels
34
Q

chemically gated channels

A

-> also known as ligand-gated channels, open when the appropriate chemical (in this case neurotransmitter) binds

35
Q

voltage-gated channels

A

open and close in response to changes in the membrane potential

36
Q

mechanically gated channels

A

open in response to physical deformation of the receptor (as in sensory receptors for touch and pressure)

37
Q

2 factors generate the resting membrane potential

A
  1. differences in the ionic composition of the intracellular and extracellular fluids
  2. differences in the plasma membranes permeability to those ions
38
Q

Resting membrane potential

A

Potential difference across the membrane of a resting cell
->Approximately –70 mV in neurons (inside of membrane is negatively charged relative to outside)

Generated by:

  • > Differences in ionic makeup of ICF and ECF
  • > Differential permeability of the plasma membrane
39
Q

Differences in ionic makeup

A
  • > Outside the cell has higher concentrations of Na+

- >Inside the cell has higher concentration of K+ and negatively charged proteins (A–)

40
Q

at resting membrane potential, the negative interior of the cell is due to a much greater ability for K+ to diffuse out of the cell than for Na+ to diffuse into the cell

A

true

41
Q

sodium-potassium pump

A
  • > pump first ejects 3 Na+ from the cell and then transports 2 K+ back into the cell
  • > this pump stabilizes the resting membrane potential by maintaining the concentration gradients for sodium and potassium
42
Q

changes in membrane potential can produce 2 types of signals

A
  • > graded potentials: usually incoming signals operating over short distances that have variable (graded) strength. dendrites
  • > action potentials: long distance signals of axons that always have the same strength, axons.
43
Q

Depolarization

A

a decrease in membrane potential: the inside of the membrane becomes less negative (moves closer to 0) than the resting potential

44
Q

Hyperpolarization

A

an increase in membrane potential: the inside of the membrane becomes more negative (moves farter from 0) that the resting potential. For ex: -70 mV-> -75

45
Q

graded potentials

A

Short-lived, localized changes in membrane potential

Depolarizations (excite) or hyperpolarizations (inhibit)

Graded potential spreads as local currents
small and localized

46
Q

Action potential

A

Brief reversal of membrane potential with a total amplitude of ~100 mV

  • > Occurs in muscle cells and axons of neurons
  • > Does not decrease in magnitude over distance
  • > Principal means of long-distance neural communication
  • > all or none
47
Q

slide 25 in ppw

A

diagram of action potential

48
Q

more Na+ ions outside the neuron than inside

A

true

49
Q

more K+ inside the neuron than outside

A

true

50
Q

leak channels allow Na and K ions to diffuse down their concentration gradients (more K leak channels)

A

true

51
Q

Graded potentials

A

short-lived, localized changes in membrane potential, usually in dendrites or the cell body

  • > changes cause current flows that decrease in magnitude with distance
  • > magnitude varies directly with stimulus strength - the stronger the stimulus, the more the voltage changes and the farther the current flows
  • > triggered by some change (a stimulus) in the neurons env. that opens gated ion channels
  • > decays with distance
  • > essential in initiating action potentials
52
Q

Different types of graded potentials

A
  • > receptor potential or a generator potential: produced when a sensory receptor is excited by its stimulus (light, pressure, chemicals)
  • > postsynaptic potential: produced when the stimulus is a neurotransmitter released by another neuron. Here, the neurotransmitter is released into a fluid-filled gap called a synapse and influences the neuron beyond the synapse.
53
Q

Action potentials

A
  • > Only cells with excitable membranes- neurons and muscle cells- can generate action potentials
  • > depolarization is followed by repolarization and often a short period of hyperpolarization
  • > do not decay with distance
  • > action potential also called a nerve impulse (typically only generated in axons)
  • > stimulus: changes the permeability of the neuron’s membrane by opening specific voltage-gated channels on the axon
54
Q

Generation of an action potential

A
  1. Resting-state:
    - > Only leakage channels for Na+ and K+ are open
  • > All gated Na+ and K+ channels are closed
    2. Depolarization: voltage-gated Na+ channels open.
    3. Repolarization: Na+ channels are inactivating, and voltage-gated K+ channels open
    4. Hyperpolarization: Some K+ channels remain open, and Na+ channels reset
55
Q

Threshold and the All-or-none phenomenon

A
  • > Not all local depolarization events produce APs. The depolarization must reach threshold values if an axon is to “fire”
  • > Threshold is the membrane potential at which the outward current created by K+ movement is exactly equal to the inward current created by Na+ movement
  • > Na+ permeability rises to such an extent that entering sodium ions “swamp” (exceed) the outward movement of K+, establishing the positive feedback cycle and generating an AP
  • > critical factor= the total amount of current that flows through the membrane during a stimulus
56
Q

Coding for stimulus intensity (action potential)

A
  • > CNS determines stimulus intensity by the frequency of impulses– higher frequency means stronger stimulus
  • > strong stimuli cause action potentials to occur more frequently
57
Q

Absolute & relative refractory period

A
  • > Absolute refractory period: Time from the opening of the Na+ channels and ends when the Na+ channels begin to reset to their original resting state.
  • > ensures that each AP is a separate, all-or-none event
  • > enforces one-way transmission of the AP
  • > Another AP cannot fire during the period
  • > Relative refractory period: Most Na+ channels have returned to their resting state, some K+ channels ae still open, and Repolarization is occurring
  • > Threshold for AP generation is elevated
  • > Exceptionally strong stimulus may generate an AP
58
Q

The synapse

A

A junction that mediates information transfer from one neuron:

  • > To another neuron, or to an effector cell (NMJ)
  • > Release of a neurotransmitter
  • > Has a presynaptic neuron and postsynaptic neuron
59
Q

Chemical Synapses

A

->Specialized for the release and reception of neurotransmitters

  • > Typically composed of two parts:
  • Axon terminal of the presynaptic neuron, which contains synaptic vesicles

-Receptor region on the postsynaptic neuron

60
Q

Termination of neurotransmitter effects

A
  • > Within a few milliseconds, the neurotransmitter effect is terminated:
  • Degradation by enzymes
  • Reuptake by astrocytes or axon terminal
  • Diffusion away from the synaptic cleft
61
Q

Postsynaptic Potentials

A
  • Graded potentials
  • Strength determined by:
  • > Amount of neurotransmitter released
  • > Time the neurotransmitter is in the area
  • Types of postsynaptic potentials
    1. EPSP—excitatory postsynaptic potentials
  1. IPSP—inhibitory postsynaptic potentials
62
Q

an action potential occurs if the combination of graded potentials exceeds a threshold

A

true

63
Q

Temporal summation

A

one neuron fires many times

64
Q

Spatial summation

A

Several neurons firing all at once

65
Q

Neurotransmitters

A

-> Most neurons make 2 or more neurotransmitters

Biogenic amines include:
-> Catecholamines-
dopamine, norepinephrine (NE), and epinephrine
-> indolamines: serotonin and histamine

Acetylcholine (Ach):

  • > Released at neuromuscular junctions and some ANS neurons
  • > Major neurotransmitter that controls muscle action
66
Q

norepinephrine (NE)

A

alertness
concentration
energy

67
Q

Serotonin

A

obsessions
compulsions
memory

68
Q

Dopamine

A

pleasure
reward
motivation/drive

69
Q

overlap between norepinephrine and dopamine

A

attention

70
Q

Overlap between norepinephrine and serotonin

A

anxiety
impulse
irritability

71
Q

Overlap between dopamine and serotonin

A

apetite
sex
aggression

72
Q

Overlap between norepinephrine and serotonin and dopamine

A

Mood

cognitive function

73
Q

Dopamine- Pleasure/reward

A

-> Our brains are wired to reward us with pleasure when we engage in behavior necessary for our species survival (food/reproduction)

Drugs of abuse:
Cocaine/Crack
-> Blocks the re update of dopamine
->Allows body to feel its effects over a prolonged period
->With continued use, body stops making dopamine
->This produces depression and cravings for the drug

74
Q

The basis for differentiation between gray matter and white matter in the CNS is the presence of _______ in white matter.

A

myelinated fibers

75
Q

Information transfer across chemical synapses

A
  1. Action potential arrives at axon terminal
  2. Voltage gated Ca2+ channels open and Ca2+ enters the axon terminal
  3. Ca2+ entry causes synaptic vesicles to release neurotransmitter by exocytosis
  4. Neurotransmitter diffuses across the synaptic cleft and binds to specific receptors on the postsynaptic membrane
  5. Binding of neurotransmitter opens ion channels, creating graded potentials
  6. neurotransmitter effects are terminated
76
Q

What division of the nervous system is most specifically responsible for voluntary motor control?

A
  • > Somatic nervous system
  • > The somatic nervous system is composed of somatic motor nerve fibers that conduct impulses from the central nervous system to skeletal muscles. It is often referred to as the voluntary nervous system because it allows us to consciously control our skeletal muscles.
77
Q

Destruction of which of the neuroglial cell types leads to the disease multiple scleroses (MS)?

A

The defects in nerve transmission associated with MS are caused by a loss of myelin within the CNS.

78
Q

Graded potentials originating in the dendrites and cell body are integrated (summated) at the axon hillock (C). Membrane potentials above threshold at the hillock will open voltage-gated Na+ channels found in the “trigger zone,” producing an action potential that proceeds down the axon.

A

TRUE

79
Q

Cold sores on the skin of the mouth occur when herpes simplex viruses that are dormant in neural ganglia become active and travel to the skin of the mouth. Which of the following is the mechanism by which these viruses travel from the ganglia (located within the head) to the skin of the mouth?

A

Anterograde transport
->This transport mechanism defines movement of material from the cell body (soma) of a neuron toward the axon terminals (synaptic knobs).

80
Q

When a neurotransmitter like acetylcholine is acting in an excitatory manner which of the following is likely a result of the acetylcholine acting on the postsynaptic cell?

A

chemically gated sodium channels will open

81
Q

nerve cell body

A
  • biosynthetic center of a neuron
  • rough ER: makes neurotransmitters
  • axon hillock: cone-shaped area from which axon arises

-clusters of cell bodies are called:
nuclei in CNS
ganglia in PNS

82
Q

functional classification of neurons

A

sensory:

  • transmit impulses from sensory receptors toward CNS
  • almost all are unipolar (1 projection)

motor:

  • carry impulses from CNS to effectors
  • multipolar

interneurons (association neurons):

  • lie between motor and sensory neurons
  • shuttle signal through CNS pathways; most are entirely within CNS
  • 99% of body’s neurons
  • multipolar

HAN 200 (15 decks)

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