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A & P 1 > Chapter 11 Nervous System & Nervous Tissue > Flashcards

Chapter 11 Nervous System & Nervous Tissue Flashcards

1
Q

Nervous system

A

the body system consisting of the brain, spinal cord, & nerves; one of the chief homeostatic systems in the body

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2
Q

Central Nervous System (CNS)

A

Brain: made up of billions of nerve cells or neurons; protected by bones of skull

Spinal Cord: Made up of millions of neurons; much fewer than brain; Spinal cord begins at foramen magnum and continues through vertebral foramina of first cervical to first or second lumbar vertebra
•Connects the brain w/ the peripheral nervous system
•Main function is to integrate information

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3
Q

Peripheral Nervous System (PNS)

A

Nerves: carry signals to & from the central nervous system; Nerves consist of axons of neurons bundled together with blood vessels and connective tissue; carry signals to and from CNS; classified based on origin or destination
Comprised of:
12 pairs of cranial nerves; nerves originating from or traveling to the brain
31 pairs of spinal nerves; nerves originating from or traveling to the spinal cord

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4
Q

Functional Divisions of the Nervous System

A

Sensory Functions- gathers information about the internal & external environment of the body

Integrative Functions- analyzes & interprets the detected sensory stimuli & determines an appropriate response; 99% of input is “filtered out”

Motor Functions- actions performed in response to integration; carries impulses from CNS to responsive parts, such as muscles or glands (autonomic & somatic)

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5
Q

Sensory Functions

A

gathers information about the internal & external environment of the body

PNS Sensory Division: sensory stimuli are first detected by structures of the PNS

Somatic Sensory Division: (special sensory division) consist of neurons that carry signals from skeletal muscles, bones, joints, & skin

Visceral Sensory Division: consist of neurons that transmit signals form

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6
Q

Integrative Functions

A

analyzes & interprets the detected sensory stimuli & determines an appropriate response; 99% of input is “filtered out”

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7
Q

Motor Functions

A

actions performed in response to integration; carries impulses from CNS to responsive parts, such as muscles or glands (autonomic & somatic)

PNS Motor Division: consist of motor neurons that carry out motor functions of the nervous system

Somatic Motor Division: (voluntary motor division) consist of neurons that transmits signals to skeletal muscles

Visceral Motor Division: (autonomic nervous system (ANS)/ involuntary motor division) consist of neurons that carry signals primarily to thoracic & abdominal viscera

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8
Q

Neurons

A

the excitable cell type responsible for sending & receiving signals in the form of action potentials.
•Conduct electrical impulses
•React to chemical and physical changes in their environment

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9
Q

Neuroglia cells

A

(neuroglia) does NOT transmit signals but serves a variety of supportive functions
•Supporting cells of the CNS
•Similar function to connective tissues

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10
Q

Structural Classification of Neurons:

A

Multipolar Neurons: a neuron with one axon & two or more dendrites; widest variability in shape & size. Most common type of neuron

Bipolar Neurons: a neuron with one axon & one dendrite; sensory neurons, located in the retina of the eye & the olfactory epithelium of the nasal cavity

Unipolar Neurons: a neuron with two axons- a peripheral process that brings input to the cell body & a central process that brings input to a target cell; detect stimuli such as touch, pressure, & pain

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11
Q

Functional Classification of Neuron

A

Sensory Neurons: (afferent) a neuron that detects changes in the environment & carry signals towards the CNS

Interneurons: (association) neurons between sensory & motor neurons that perform integrative functions; relay messages within the CNS

Motor Neurons: (efferent) a neuron that transmits motor impulses away from the CNS to muscles & glands

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12
Q

CNS Neuroglia

A

Astrocytes: a neuroglia cell of the CNS that facilitates information of the blood brain barrier, regulates extracellular environment of the brain, anchors neurons & blood vessels in place, & repair damaged brain tissue

Oligodendrocytes: a neuroglia cells of the CNS that myelinates certain axons

Microglia: act as phagocytes

Ependymal Cells: a ciliated neuroglia cell of the CNS that lines the hollow cavities of the brain & spinal cord; cilia beat to circulate cerebrospinal fluid

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13
Q

PNS Neuroglia

A

Schwaan Cells: a neuroglia cell of the PNS that myelinates the axons of certain neurons; repair damaged axons in PNS. Interneuron/association neurons

Satellite Cells: a neuroglia cell of the PNS that surrounds & supports cell bodies of neurons

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14
Q

The Myelin Sheath

A

Myelin: a fatty substance that envelops & insulates the axon of certain neurons, increasing the speed of action potential conduction; formed from the plasma membranes of oligodendrocytes & Schwann cells
•Phospholipids, other lipids such as cholesterol, & proteins
•Myelinated axon: white matter; faster action potentials
•Unmyelinated axon: grey matter; are made up primarily of cell bodies & dendrites
Myelination: the process of myelin sheath formation
Importance: protection & insulation of axons

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15
Q

Differences in myelination of PNS & CNS

A

Presence or Absence of a Neurolemma- outer surface of a myelinated axon in PNS; composed of Schwann cell nucleus, organelles, & cytoplasm; not present in CNS

Number Axons Myelinated by a single glia cell- Oligodendrocytes have multiple process that can provide myelination for multiple axons in CNS while a Schwann cell only provides myelination for ONE axon in PNS

Timing of Myelination- myelination begins early in fetal development in PNS and much later in the CNS; very little myelin present in brain of newborn

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16
Q

Regeneration of Nervous Tisssue

A

Regeneration: the process by which a damaged tissue is replaced w/ the same tissue during healing

Regeneration in CNS- damaged axons & dendritesnearly nonexistent
•Lacks growth factors that trigger mitosis are absent in CNS
•Growth of astrocytes creates space-filled scar tissue that prohibits regeneration
•Lost function may be regained by retraining the remaining neurons

Regeneration in PNS- limited; can only occur if cell body remains intact
If regeneration occurs, its often imperfect. The axon will contact the wrong target cell or contact between the cells will not be re-established

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17
Q

The electrical changes across a neuron’s plasma membrane comes in two forms

A

1) Local potentials–>travel only short distances

2) Action potentials–>travel the entire length of an axon

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18
Q

Importance of Ion Channels, Pumps & Membrane Polarization:

A

•The resting membrane of the neuron is polarized
o Na+ and K+ ions are uneven distributed across the membrane; more Na+ outside & more K+ inside results in charge difference which give “potential energy”

  • Channels that could allow the ions to move are “gated” and closed under resting conditions
  • The Na+/K+ pump maintains the gradient
  • Na+/K+ pump brings 2 potassium ions into the cytosol as it moves 3 sodium ions into the extracellular fluid
  • When you measure the membrane potential of a neuron at rest, or the resting membrane potential, it measures about -70mV (polarized)
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19
Q

Leak Channel

A

Leak Channel: always open

Location: all over neuron

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20
Q

Ligand-gated Channel

A

Ligand-gated Channel: opens in response to a certain chemical (neurotransmitter), called a ligand binding to the channel or to a receptor associated with the channel
Location: Dendrites & cell body

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21
Q

Voltage-gated Channel

A

Voltage-gated Channel: opens or closes in response to changes in the cell’s membrane potential (electrical signal)
Location: mostly on axons; axolemma of a neuron

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22
Q

Mechanically-gated Channel

A

Mechanically Gated Channel: opens or closes in response to mechanical stimulation such as stretch, pressure, & vibration
Location: dendrites

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23
Q

Voltage numbers of States of Membrane Polarity:

A

inside is negative w/ respect to outside
•Polarization: -70mV
•Threshold: -55 to -50mV
•Depolarization: voltage shoots to + values (+30mV)
•Hyperpolarization: greater than -70mV

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24
Q

Local Potential

A

(graded potentials) a small change in the membrane potential in a specific region of a cell’s plasma membrane, when a neuron is stimulated just once

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25
Q

Action Potential

A

a quick, temporary rapid depolarization & repolarization of the membrane potential of a cell
•Signals are sent through an axon to another neuron, a muscle fiber, or a gland
•Axons can generate action potentials; dendrites & cell bodies generate LOCAL potentials only
•Action potentials START at the axon hillock & END at the axon terminal

26
Q

States of Voltage-Gated Channels

A

Two types of voltage-gated channels are involved in depolarization & repolarization of an action potential  one for sodium ions & one for potassium ions
Found in the axolemma of a neuron, which is why only axons have action potential

27
Q

Events of an Action Potential

A

1) A local potential depolarizes the axolemma of the trigger zone to threshold
2) Voltage-gated Na+ channels activate, Na+ enter, & the axon section depolarizes
3) Na+ channels inactivate & voltage-gated K+ channels activate, & repolarization begins
4) Na+ channels return to the resting state & repolarization continues
5) The axolemma may hyperpolarize before K+ channels return to the resting state; after this, the axolemma returns to the resting membrane potential

28
Q

Refractory Period & Two Phases

A

Refractory Period: for a brief time after a neuron has produced an action potential, the membrane cannot be stimulated to fire another one. Neurons are limited in how often they can fire action potentials.

Two Phases: Absolute refractory period & Relative Refractory period

Absolute refractory period: no additional stimulus, no matter how strong, is able to produce an additional action potential

Relative refractory period: Only a strong stimulus will produce an action potential

29
Q

Local Potentials

A

Due to signal at the dendrites/cell body
Decremental (strength decreases over short distances)
May be inhibitory or excitatory
Uses ligand gated channels (cell body/dendrites)
Reversible
Only travels a short distance

30
Q

Action Potentials

A

Due to signal summation at the axon hillock/trigger zone
Non-decremental (strength does NOT dimmish)
Always causes a depolarization (excitatory)
Uses voltage gated channels (axon)
Irreversible
Travels all the way down the axon

31
Q

Classification of Axons by Conduction Speed

A

axons are classified according to conduction speed; the diameter of the axon & the presence or absence of myelin sheath

Type A fiber: largest-diameter axons & thick myelinated; fastest conduction speed. Found in CNS where rapid communication occurs such as certain sensory axons from joints & muscle fibers, as well as motor axons to skeletal muscles

Type B fiber: medium in diameter & lightly myelinated; intermediate speeds. Found in certain efferent fibers of the autonomic nervous system & certain sensory axons coming from organs

Type C fiber: smallest fibers & unmyelinated; slowest conduction speed. Found in efferent fibers of the autonomic nervous system & certain sensory axons that transmit pan, temperature, & certain pressure sensations

32
Q

Synapse

A

the location where a presynaptic neuron communicates with its target cell

33
Q

Neuronal synapses

A

synapses that occur between two neurons; electrical & chemical

34
Q

Pre-synaptic Neuron

A

the neuron that is sending the message from its axon terminal

35
Q

Post-synaptic Neuron

A

the neuron that is receiving the message from its dendrite, cell body, or axon

36
Q

Synaptic transmission

A

the transfer of chemical or electrical signals between neurons at a synapse; allow voluntary movement, cognition, sensation, emotion, etc.

37
Q

Synaptic cleft

A

the small space between the axon terminal of a presynaptic neuron & its target cell; filled w/ extracellular fluid & proteins such as enzymes

38
Q

Chemical Synapses

A

a presynaptic neuron releases neurotransmitter to trigger a change in a postsynaptic neuron; more common b/c they’re more efficient

39
Q

Events of a Local Potential (Chemical Synapse)

A

1) An action potential in the presynaptic neuron triggers Ca2+ channels in the axon terminal to open
2) Influx of Ca2+ causes synaptic vesicles to release neurotransmitters into the synaptic cleft
3) Neurotransmitters bind to receptors n the postsynaptic neuron
4) Ion channels open, leading to a local potential & possibly an action potential

40
Q

Post-synaptic potentials

A

a positive or negative charge in the membrane potential of a neuron as a result of a synaptic transmission. It can move the membrane potential at the rigger zone either closer or farther way from the threshold.

41
Q

Excitatory Postsynaptic potential (EPSP):

A

a small local depolarization; becomes less negative due to the influx of positive ions
•The membrane potential of the postsynaptic neuron moves closer to threshold
•Ligand-gated channels (sodium or calcium) open & these positively charged ions enter the postsynaptic neurons & will cause a local depolarization

42
Q

Inhibitory postsynaptic potential (IPSP):

A

a small, local hyperpolarization; becomes more negative due to the outflow of positive ions or the influx of negative ions
•The membrane potential of the post-synaptic neuron moves away from threshold
•Ligand-gated potassium ions channels open causes the cytosol to lose + charge & makes the membrane potential become more negative
•Ligand-gated chloride ion channels open these anions enter the neuron & makes the membrane potential more negative

43
Q

Neural Integration

A

The process by which a neuron integrates all of the postsynaptic potentials from multiple presynaptic neurons

44
Q

Summation

A

adding the input from several postsynaptic potentials to affect the membrane potential at the trigger zone/axon hillock

  • Temporal Summation: the additive effect of a excitatory postsynaptic triggered by a SINGLE presynaptic neuron that fires action potential in rapid succession
  • Spatial Summation: The additive effect of excitatory postsynaptic potentials triggered by MULTIPLE presynaptic neurons firing action potentials simultaneously
45
Q

Summation of IPSP

A

the postsynaptic neuron becomes less & less likely to fire an action potential

46
Q

Summation of IPSPs & EPSP

A

results depend in the individual strength of IPSP & EPSP—if the IPSP is stronger, the membrane potential will hyperpolarize slightly, & if the EPSP is stronger, the membrane potential will depolarize slightly

47
Q

Synaptic Transmission Termination

A

it’s how neurotransmitters are removed from the synaptic cleft. When neurotransmitter molecules have been removed from the synaptic cleft, synaptic transmission is complete

•Neurotransmitters usually remain in the synaptic left for a short time

Diffusion & Absorption: neurotransmitters diffuse away from the synaptic left into the surrounding extra-cellular matrix

Degradation: neurotransmitters are degraded by enzymes in the synaptic cleft
Example: AChE digest ACh

Reuptake: neurotransmitters are taken back into the presynaptic neuron by proteins in its axolemma; they’re either repackaged into synaptic vesicles or degraded by enzymes.

48
Q

Classes of neurotransmitter receptors:

A

Ionotropic receptors: rapid, but short-lived effects on the membrane potential of the postsynaptic neuron; receptors that are part of ligand-gated ion channels

Metabotropic receptors: elicit much slower changes in the membrane potential of the postsynaptic neuron, but the effects are typically longer lasting & more varied than those of the ionotropic receptors

49
Q

Acetylcholine

A

ACh: in PNS & CNS how association neurons “talk to each other (nicotine)

50
Q

Norepinephrine & Epinephrine

A 
Norepi= neurotransmitter 
Epi= hormone adrenaline
51
Q

Dopamine

A

pleasure & reward system

52
Q

Serotonin

A

Mood/depression-target of many antidepressants

53
Q

Glutamate

A

High stimulatory- learning & memory

54
Q

GABA

A

Major depressant- but is critical for modulating how neurons talk to each other (increased w/ alcohol)

55
Q

Endorphins

A

Natural pain killers

56
Q

Adenosine

A

Lowers brain activity=sleepy

caffeine suppresses this activity

57
Q

Neuronal Pool

A

a network of neurons that perform a common function; they have a specific patterns of organization called neural circuits

58
Q

Neural Circuits

A

pattern of connection between neuronal pools

59
Q

Diverging circuit

A

One or more input neurons that contact an increasing number of postsynaptic neurons

60
Q

Converging circuit

A

the signals from multiple neurons converge into one or more final postsynaptic neuron. Axon terminals from multiple input neurons join onto a single postsynaptic neuron.

A & P 1 (8 decks)

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