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Anatomy (Pharm 110) > 5.1 Nervous tissue > Flashcards

5.1 Nervous tissue Flashcards

1
Q

divisions of motor system

A

Central Nervous System (CNS):

  • Brain annd spinal chord of doral body cavity
  • integration and control center: interprets sensory input and dictates motor output

Peripheral Nervous System

  • portion of the nervous system CNS
  • Consists mainly or nerves that extend from brain and spinal chord
    • spinal nerves to and rom spinal chord
    • Cranial neres to and from brain
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2
Q

Sensory division of PNS

and ex

A

*afferent pathway

  • somate and visceral sensory nerve fibers
  • conducts impulses from receptos to CNS
    ex: Skin -> Somatic sensory fibers

Ex: stomac -> isceral sensory fibers

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3
Q

Motor divison of CNS

A

* efferent pathway: motor nerve fibers (conduct impulses from CNS -> effectors

  • somatic (voluntary, cns -> skeletal muscles) and autonomic division (visceral motor fibers, involuntary)
  • autonomic is further divided into: sympathetic and parasympathetic
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4
Q

What are the two principal types of cells in the NS

A

1) Neurons: excitable cells that transmit electrical signals
2) Neuroglia (glial cells): supporting cells (6 types)

* Neuroglia out number neurons by a 10:1 ratio -> make up half the mass of the brain

*in CNS extracellular space is less than 20%

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5
Q

What are the types of neuroglia?

A

CNS: Astrocytes, microglia, ependymal cells, oligodendrocytes

PNS: Satellite and Schwann cells

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6
Q

What are astrocytes

A

*only in CNS, most abundant cell in brain (20-40% of gial cells)

  • guides migration of young neurons an dformation of synpases, suppors anchors and braces neurons
  • cover capillaries and help determine capillary permeability
  • control chemical env (neurotransmitters and ions, mop up K+)
  • have gap junctions to communicate between astrocytes (Ca2+ pulses)

participate in information processing in brain -> modulate synpatic transmission and play role in long term propogation

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7
Q

Role of astrocytes in BBB

A
  • NOT A BIG RILE
  • tight junctions and basal lamina of cerebral endothelial cells play biggest role in BBB
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8
Q

What are Microglia?

A

Small, ovoid cells with thorny processes

  • Migrate toward injured neurons
  • Phagocytize microorganisms & neuronal debris
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9
Q

WHat are ependymal cells

A

*CNS

  • range in shape from squamous to columnar
  • Ciliated cells circulate cerebrospinal fluid (CSF) around CNS
  • Line central ventricular cavities of brain & spinal column
  • Produce CSF
  • Separate the CNS interstitial fluid from CSF
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10
Q

what are oligodentrocutes

A

*CNS

One cell can produce processes that wrap up to 60 axons (1 μm)

• Forming insulating myelin sheaths

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11
Q

What are satellite glial cells (SGC)

A

*PNS

Surround neuron cell bodies in ganglia of PNS

  • Control microenvironment around neuron cell body
  • Similar to astrocytes of the CNS
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12
Q

What are Schwann cells

A

*PNS

Most form myelin sheaths around axons

• Vital for function, maintenance and regeneration of damaged nerve fibers

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13
Q

How do schwann cells myelinate?

A
  1. envelopes an axon
  2. Schwann cell rotates around axon, wrapping its plasma membrane loosely around it in successive layers.
  3. Schwann cell cytoplasm is forced from between membranes (tight membrane wrappings surrounding axon form myelin sheath).
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14
Q

what is the Myelin Sheath?

A

Composed of myelin, a whitish, protein-lipid substance

Function: Protect and electrically insulate axon & Increase speed of nerve impulse transmission

– Myelinated fibers: segmented sheath surrounds most long or large-diameter axons

– Nonmyelinated fibers: do not contain sheath -> Conduct impulses more slowly

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15
Q

Myelin sheaths in the PNS

A
  • Schwann cells wrap many times around axon
  • neurilemma: peripheral buldge of Schwann cell cytoplasm
  • gaps in myelin sheal between adjacent schwann cells = Nodes of Ranvier

*sites wehre axon collaterals can emerge

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16
Q

Unmyelinated Axons in the PNS

A
  • thin nerve fibers are unmyelinated
  • one Schwann cell may incompletely enclose 15+ unmyelinated exaons
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17
Q

Myelin Sheaths in the CNS

A

Formed by processes of oligodendrocytes

  • Nodes of Ranvier
  • No neurilemma
  • Thinnest fibers (axons) are unmyelinated
  • One oligodendrocyte can wrap around up to 60 axons
  • Gives rise to white matter
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18
Q

what are Neurons/ their special charcateristics of neurons

A
  • Neurons = structural units of the nervous system
  • large highly specialized cells that conduct impulses

Special characteristics: exteme longevity (lasts lifetime), amitotic (non dividing), high metabolic rate: req continuous supply of oxygen and glucose

*al have cell body and one or more processes

19
Q

What is the other name for the Neuron cell body?

It is the ____ center of the neuron

what structureal features does it contain?

A

Neuron cell body = Perikaryon or soma

  • biosynthetic centre of the neuron

*synthesizes proteins, membranes and chemicals

contains a Rouhg ER (chromatophilic substance or Bissl bodies

*PM is part of the region that receives input along with the dendrites

20
Q

CLusters of Nuerno cell bodies are called ___ in the CNS and ___ in the PNS

A

Nuclei in CNS
– Ganglia in PNS

21
Q

what is the axon hillock

A

part of neuron cell body (perikaryon)

  • cone shaped area from which axon arises (lacks nissle bodies)
22
Q

What are the two types of neuron processes?

What are the bundles of these processes called?

A

Two types of processes: Dendrites & axons

Bundles of processe sare called: Tracts in CNS and Nerves in PNS

23
Q

What are Dendrites

A
  • motor neurons contains 100s of dendries (short tapering diffusely bracnhes processes)

*contain same organelles as in cell body

  • Receptive (input) region of neuron

– Convey incoming messages toward cell body as graded potentials (short distance signals)

– Finer dendrites are highly specialized to collect information

24
Q

What are structures on finer dendries

A

contain dendritic spines, appendages with bulbous or spiky ends

25
Q

Describe the axon/ its structure

A
  • one per neuron, starts at axon hillock
  • some axons can be over 1m long
  • branches are called axon collaterals

Axons branch profusely at their end (terminus)

• Can number as many as 10,000 terminal branches (telodendria)

– Distal endings are called axon terminals or terminal boutons

26
Q

What is the function of the axon?

A
  1. generates & transmits nerve impulses (action potentials) away from cell body
  2. Trafficking along axons by motor molecules in two directions:
    • Anterograde: away from cell body (twds axon term)
      • can move: mitochondria, cytoskeletal elements, membrane components, enzymes
    • Retrograde: toward cell body
      • organelles to be degraded, signal molecules, viruses, and bacterial toxins
27
Q

what are the 3 structural classifications of neurons

A

multipolar, bipolar and unipolar

28
Q

what are multipolar neurons?

A

three or more processes with one axon and rest dendrites,

most abundant (>99% CNS neurons are multipolar) includes motor neurons and interneurons

29
Q

What are bipolar neurons

A

two processes with one axon + one dendrite

(Rare) found in retina and olfactory mucosa

*found in sensory organs (olfactory, mucosa, eye and ear)

30
Q

what are unipolar neurons

A

(pseudounipolar): single, short process that has 2 branches.

Cell bodies typically are found in ganglia in the PNS where they function as sensory neurons

* Peripheral process: more distal branch, often associated with a sensory receptor

* Central process: branch entering CNS

*common only in dorsal root ganglia of spinal chord and sensory ganglia of cranial nerves

31
Q

What are the functoinal classifications of neurons

A
  1. Sensory(afferent):Transmitimpulsesfromsensoryreceptors toward CNS
  2. Interneurons (association neurons): Shuttle signals through CNS pathways; most within CNS
  3. Motor(efferent):CarryimpulsesfromCNStoeffectors
32
Q

What is white matter and gray matter?

A

White matter: Dense collections of myelinated fibers

Gray matter: Mostly neuronal cell bodies & unmyelinated fibers

33
Q

Basic principles of electricity for potentials

what is voltage, current and resistance?

A
  • Voltage (V) = measure of potential energygenerated by separated electrical charges
  • measured between two points -> potential difference
  • Flow of electrical charges (electrons and ions) from one point to another = current (I)

• Resistance (R) = hindrance to charge flow

* Insulator: substance with high electrical resistance

*Conductor: substance with low electrical resistance

34
Q

What is Ohms law

A

Current (I) = voltage (V)/resistance (R)

Current directly proportional to voltage
• Greater the voltage (potential difference) = greater current
*No net current flow between points with same potential

– Current = inversely proportional to resistance

* The greater the resistance, the smaller the current

35
Q

What are the two main types of ion channels when dealing w/ electricity in cell

A
  1. Leakage (nongated) channels * always open
  2. Gated channels, in which part of the protein changes shape to open/close the channel
    • Three main gated channels: chemically gated, voltage- gated, or mechanically gated
36
Q

compare the 3 types of electical gated channels

A

chemically gates; open with bidnign of specific neurotransmitter *assist w/ graded potential

Voltage: open and close in response to changes in membrane potential * assist with active

Mechanically gated: open and close in response to physical deformation of receptors (assist w/ graded pot

37
Q

What is resting membrane potential and what is it influenced by?

A

RMP of neuron ~70 mV

  • cytoplasmic side of neutron is neg charged rel to outside

RMP influenced by:

  • Impermeable to negatively charged proteins
    – Slightly permeable to Na+ (Na+ leakage channels)
    – 25-100 times more permeable to K+ (K+ leakage channels)

– Freely permeable to Cl–
– Differences in ionic composition of ICF and ECF
– Differences in plasma membrane permeability

38
Q

Sodium and potassium conc on either side of memrbane at rest

A

Na conc higher outside cell

K conc hgiher inside cell

*Na+-K+ ATPases (pumps) maintain concentration gradients of Na+ & K+ across membrane.

39
Q

How is resting membrane potential generated?

A

*ranges from -20 to -200 mV

  • Requirements:

 Na+ /K+ pump: pumps more cations out

 The concentration gradient of K+

 Higher permeability to K+

 Membrane impermeable anionic proteins

40
Q

What signals cause changes in membrane potential?

A
  • Membrane potential changes when: Concentrations of ions across membrane change & Membrane permeability to ions changes

Graded potentials; incoming signals operating over short distances

Action potentials; long distance signals of axons

* Changes in membrane potential are used as signals to receive, integrate, and send information

41
Q

Depolarization vs hyperpolarization

A

Depolarization

  • reduction in membrane potential
  • Inside of membrane becomes less negative than resting potential
  • ↑ probability of producing a nerve impulse

Hyperpolarization

  • increase in membrane potential
  • Inside of membrane becomes more negative than resting potential
  • ↓ probability of producing a nerve impulse
42
Q

What are graded potentials?

What are the two types?

A

Short-lived, localized changes in membrane potential

– stronger the stimulus = more voltage changes -> farther current flows

  • Triggered by stimulus that opens gated ion channels -> depolarization or hyperpolarization

Named according to location and function

– Receptor potential (generator potential): graded potentials in receptors of sensory neurons excited by some form of energy (e.g. heat, light or other)

– Postsynaptic potential: neuron graded potential

43
Q

How do graded potentials travel? what happens w/ distance

A

Depoalrization causes small patch of membrane to depolarize

  • spreads -> opposite charges attract each other creating local currents that depoalrize adjactent areas
  • membrane potential decays w/ distance bc current is last thru leaky plasma membrane

*graded potentials are short distance signals

Anatomy (Pharm 110) (41 decks)

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