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Anatomy > Nervous Tissue - Chapter 13 > Flashcards

Nervous Tissue - Chapter 13 Flashcards

1
Q

What is the difference in the endocrine and nervous systems? How are they similar?

A

Differences:

  • Endocrine sends chemical messages int he form of hormones secreted into the bloodstream
  • Nervous sends electrical and chemical messages from cell to cells, more focused signaling

Similarities:

  • Both maintain internal coordination
  • Both send messages to other parts of the body
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2
Q

What three jobs of the nervous system fall into these categories?

  1. Sensory
  2. Integrative
  3. Motor
A
  1. Sensory - collect info (about changes in body and external environment, sends those messages to brain and spinal cord)
  2. Integrative - process and evaluate (CNS processes info and relates it to past experiences and determines response)
  3. Motor - initiate response (CNS issues commands to muscles and glands to carry out response)
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3
Q

What are the two subdivisions of the nervous system?

A
  1. Central Nervous System (CNS) - brain and spinal cord

2. Peripheral Nervous System (PNS) - everything else

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4
Q

What is the difference in a nerve and a ganglion?

A
  1. Nerve - bundle of nerve fibers (axons) wrapped in fibrous CT
  2. Ganglion - knot-like sweeping in a nerve where neuron cell bodies are concentrated
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5
Q

What are the 2 divisions of the PNS?

A
  1. Sensory (afferent) Division - carries signals from receptors to CNS
  2. Motor (efferent) Division - carries signals from CNS to effectors (glands and muscles)
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6
Q

What are the subdivisions of the Sensory Division of the PNS and what do they do?

A
  1. Somatic sensory division - carry signals from receptors in skin, muscles, bones, and joints
  2. Visceral sensory division - carry signals to guts, organs, etc.
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7
Q

What are the two subdivisions fo the Motor Division

A
  1. Somatic motor division - sends signals to skeletal muscles for contraction and reflexes (voluntary responses)
  2. Visceral motor division - signals to glands, cardiac and smooth muscles (involuntary responses)
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8
Q

The visceral motor division of the PNS is further divided into 2 more subparts. What are those and what do they do?

A
  1. Sympathetic division - action (accelerates heart rate and respirations, inhibits digestive and urinary systems)
  2. Parasympathetic division - calming (slows heart rate and breathing, stimulates digestive and urinary systems)
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9
Q

What are 3 universal properties of neurons?

A
  1. Excitability/irritability - response to environmental changes/stimuli
  2. Conductivity - response to stimuli by producing, quickly conducted to other cells at distant locations
  3. Secretion - electives signal reaches the end of nerve fiber, the cell secretes a chemical neurotransmitter which influences the next cell
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10
Q

How long to nerve cells live? How often do they reproduce?

A

Live a very long time
Don’t make new nerve cells after maturity
Non-mitotic (mostly)

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11
Q

What are the three functional classes of neurons?

A
  1. Sensory (afferent) neurons - detect stimuli and transmit information TOWARD the CNS (light, heat, pressure, chemicals, etc)
  2. Interneurons - entirely within the CNS, connect motor and sensory pathways, receive signals from many neurons and carry out integrative functions, ~90% of all neurons
  3. Motor (efferent) neurons - send signals AWAY from CNS (to muscle and gland cells, aka the effectors)
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12
Q

What is the job of the neurosoma in the structure of a neuron? What’s another name for it?

A

Aka cell body or soma
Control center
Single, centrally located nucleus, typical organelles (lots of mitochondria, no centrioles cause no mitosis)

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13
Q

What are the axoplasm and axolemma?

A

Axoplasm - cytoplasm of axon

Axolemma - plasma membrane of axon

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14
Q

What are dendrites?

A

Branches from neurosoma, receive signals

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15
Q

What is the effect of a neuron having more dendrites?

A

It can receive more information, more precise pathways for reception and processing

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16
Q

What is an axon? What does it do? What are some key features of an axon?

A

Nerve fiber
Transmits nerve impulses AWAY from the cell body
Key features: axon hillock (mound on neurosoma), Axon collaterals (major beaches of axon), branch (telodendria), synaptic terminal (tip of branch), Myelin sheath (may enclose axon)

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17
Q

What are the four different classes of neurons?

A
  1. Multipolar (one axon, multiple dendrites)
  2. Bipolar (one axon, one dendrite)
  3. Unipolar (single process)
  4. Anaxonic (no axon, many dendrites)
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18
Q

What is a multipolar neuron and what does it do?

A 
One axon, multiple dendrites
Most common (most neurons in CNS)
Motor neurons (muscles/glands)
19
Q

What is a bipolar neuron and what does it do?

A

One axon, one dendrite

Sensory (olfactory cells, retina, inner ear [rare])

20
Q

What is a unipolar neuron and what does it do?

A

Single process leading away from neurosoma (branches like a T)
Sensory cells from skin and organs to spinal cord

21
Q

What is an anaxonic neuron and what does it do?

A

Many dendrites but no axon

Retina, brain, and adrenal gland

22
Q

Do you have more neurons or glial cells? Why/how?

A 
Glial cells (by at least 10 to 1)
They're capable of mitosis
23
Q

What are the (4) functions of glial cells?

A
  1. Protect neurons and help them function
  2. Bind neurons together and form framework for nervous tissue
  3. Guide migrating neurons to their destinations (in vitro)
  4. Insulation - prevents neurons from touching each other, gives precision to conduction pathways
24
Q

What types of neuroglia can be found in the CNS?

A
  1. Oligodendrocytes
  2. Ependymal cells
  3. Microglia (least abundant)
  4. Astrocytes (most abundant)
25
Q

What are oligodendrocytes and where are they found?

A

Neuroglia cells of CNS
Large, bulbous cells
Form myelin sheath - speeds up signal conduction
Arm-like processes wrap around nerve fibers

26
Q

What are ependymal cells and where are they found?

A

Neuroglia cells of CNS
Line internal cavities of the brain (and central canal of SC)
Secrete and circulate CSF (choroid plexus, resemble cuboidal epithelium with cilia on apical surface)

27
Q

What are microglia cells and where are they found?

A

Neuroglia cells of CNS - least abundant
Phagocytic cells (develop from WBC)
Wander the CNS looking for debris and damage (replicate in response to infection, become concentrated in areas of damage, influential during development)

28
Q

What are astrocytes and where are they found?

A

Neuroglia cells of CNS - most abundant
Covers brain surface and most non-synaptic regions of neurons in the gray matter
Functions: supportive framework, blood brain barrier, monitor neuron activity, regulate blood flow, secrete nerve growth factors, stabilize chemical environment, add/eliminate synapses, form scar tissue and fill space of nerve damage

29
Q

What types of neuroglia can be found in the PNS?

A
  1. Schwann cells

2. Satellite cells

30
Q

What are Schwann cells and where are they found?

A

Neuroglia cells of PNS
Wrap around nerve fibers to form myelin sheath (provides insulation, increases speed of impulse)
Assist in regeneration of damaged fibers

31
Q

What are Satellite cells and where are they found?

A

Neuroglia cells of PNS
Surround the neurosomas in ganglia
Provide electrical insulation
Regular the chemical environment

32
Q

What is the job of the myelin sheath?

A

Insulates the nerve fiber

33
Q

What is the myelin sheath made of?

A

Oligodendrocytes in CNS, Schwann cells in PNS
Essentially an extension fo the plasma membrane of glial cells
Primarily made of lipids
White coloration fo myelinated parts of NS

34
Q

What is myelination? When does it happen?

A

Production of myelin sheath
Begins during fetal development
Proceeds rapidly during infancy

35
Q

What is the neurilemma?

A

Thick, outermost coil of myelin sheath
Contains nucleus and most of its cytoplasm
Basal lamina and a thin layer of fibrous CT (endoneurium) lie external to the neurilemma

36
Q

Describe the myelin sheath of the PNS

A

Schwann cells spirals repeatedly around a single nerve fiber
Up to 100 layers of membrane
No cytoplasm between layers
Neurilemma is outermost layer w/ nucleus

37
Q

Describe the myelin sheath of the CNS

A

Oligodendrocytes myelinated several nerve fibers
Cannot migrate around any one of them like Schwann cells
Myelination spirals inward
No neurilemma or endoneurium

38
Q

The axon hillock has two important “zones” or “segments.” What are they and what do they do?

A
  1. Trigger Zone - important in initiating a nerve signal

2. Initial segment - short section of nerve fiber between axon hillock and first glial cell

39
Q

Why is the myelin sheath segmented? What are the segments called?

A

To allow for signal transduction - signal “jumps” from node to node

  1. Myelin sheath caps (aka nodes of Ranvier) - gap between segments
  2. Internodes - myelin-covered segments from one gap to the next
40
Q

Describe the use of ion channels in a nerve signal

A

Nodes of Ranvier are violated-gated ion channels. As Na+ enters the cell at a node, the electrical field repels positive ions inside, transferring energy down the axon rapidly (the signal)

Then, the next node is reached with a signal strong enough to open the voltage gated ion channels, and it starts all over

41
Q

What is the job of myelin in reference to voltage gated ion channels?

A

It speeds up conduction
Minimized leakage of Na+ out of cell
Lower attraction between ions inside/outside cell

42
Q

Do unmyelinateud axons exist? If yes, where?

A

Yes:
PNS - unmyelinateud axons propagate impulses by continuous conduction (implies travels entire length of axon), partially enveloped by Schwann cells, but does not wrap around each axon

CNS - unmyelinateud axons are anchored together by astrocytes

43
Q

What determines the speed at which a nerve signal travels along the surface of a nerve fiber?

A
  1. Diameter of fiber (larger fibers conduct more rapidly)

2. Presence or absence of myelin (speeds signal conduction)

44
Q

Where do you find slow conduction speeds? Fast?

A

Slow - gastrointestinal tract

Fast - Skeletal muscles (improves balance and coordinated body movement)

Anatomy (14 decks)

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