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Module 2: MSK > Nervous tissue > Flashcards

Nervous tissue Flashcards

1
Q

What are the two classes of cells in nervous tissue?

A

Neurons and glia

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2
Q

What is the CNS?

A

Central nervous system is contained within the spinal column and skull: 1. Brain 2. Spinal chord

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3
Q

What is the PNS?

A

Peripheral nervous system is primarily outside of spinal columns and skull: 1. nerves 2. ganglia

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4
Q

What is the difference between afferent and efferent?

A

Afferent = sensory = incoming – from receptor to CNS Efferent = motor = outgoing – from CNS to effector

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5
Q

What is the difference between somatic and autonomic divisions?

A

Based on targets of efferent information and sources of afferent information: Somatic = part of the nervous system having to do with the body (soma = body) Autonomic = monitors and controls functions that are internal (i.e. blood pressure, heart rate, gut motility, oxygenation, etc)

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6
Q

What do somatic efferent fibers do?

A

ALWAYS and ONLY innervate skeletal muscle (AKA: General Somatic Efferent)

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7
Q

What do Autonomic efferent fibers do?

A

Innervate: Cardiac muscle, smooth muscle, glands, and fat NEVER innervate: skeletal muscle (AKA General Visceral Efferent)

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8
Q

What do Somatic afferent fibers do?

A

Collect information regarding the body. Includes: - Pain - Temperature - Touch - Pressure - joint position - information from golgi tendon organs and muscle spindles Most of which we can be concious of and can pinpoint (AKA General Somatic Afferent)

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9
Q

What do Autonomic afferent fibers do?

A

Collect information such as degree of stretch and chemical composition from internal organs and blood vessels (AKA General Visceral Afferent)

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10
Q

What is the embryonic origin of the cells int he CNS?

A

Both neuronal and non-neuronal CNS cells are derived from the neural tube. - The neural tube originates from epithelial cells in the ectoderm.

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11
Q

What characteristics do epithelial tissue and nervous tissue share?

A

Because nervous tissue originates from epithelial tissue in the neural tube, it has: - No connective tissue except that which surrounds the CNS and the blood vessels that penetrate the CNS - Entire CNS is surrounded by basal lamina (that began as basal lamina of neural tube) - Brain and spinal cord have fluid filled cavities lined by ependyma (epithelial cells)

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12
Q

Describe the two sections shown

A
  1. White matter: contains oligodendrocytes, nerve processes
  2. Gray matter: Made up of dorsal and ventral horns; contain neuron cell bodies and microglial cells
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13
Q

Where would you find spinal nerves?

A

They are formed where the dorsal and ventral roots meet.

  • less than an inch long
  • extend distally only to the point where the nerve divides into dorsal and ventral rami
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14
Q

What type of nerve fibers exist in spinal nerves?

A

Spinal nerves are mixed nerves

  • contain both afferent and efferent fibers
  • also contain elements of both the somatic and autonomic systems
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15
Q

How many spinal nerves are there in a human?

A

31

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16
Q

What would result from cutting a dorsal root?

A

Dorsal roots are completely sensory

  • cutting root results in loss of sensation, both somatic and visceral
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17
Q

What is the dorsal root ganglion?

A

Near the distal end of the dorsal root, right where it exits an intervertebral foramen, is the DRG

  • contains the cell bodies of the dorsal root neurons
  • Each cell body has a peripheral process that receives information from receptors and a central process taht enters the spinal cord
  • There are no synapses in the dorsal root ganglion
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18
Q

What would result from cutting a ventral root?

A

Ventral roots are completely motor

  • cutting this root results in paralysis
  • both somatic and autonomic fibers are involved
  • there are no ganglion along the ventral root; cell bodies are located in spinal cord
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19
Q

What is the general principal of Autonomic Efferents? What makes them differnt from Somatic Efferents?

A
  • All Autonomic pathways from CNS to target organ (heart, smooth muscle, glands) have TWO neurons (somatic have one)
  • Preganglionic neuron = cell body in CNS
  • Postganglionic neuron = cell body in ganglion
  • Autonomic ganglia have synapses; somatic do not
  • Autonomic ganglion = ALWAYS motor/efferent; Somatic = ALWAYS sensory/afferent
20
Q

Fill in the chart:

A
21
Q

What can be found in the gray matter of the spinal cord?

A

neuronal cell bodies and their dendrites, along with axons and central microglia

  • synapses occur here
22
Q

What can be found in the white matter of the spinal cord?

A
  • Myelinated and unmyelinated axons
  • Oligodendrocytes
23
Q

Explain the connective tissue of the CNS

A

Three sequential connective tissue membranes, called the meninges, cover the brain and spinal cord:

  • Dura mater = outermost layer
  • arachnoid mater = layer beneath the dura
  • pia mater = delicate layer resting directly on surface of brain and spinal cord
24
Q

What is a Nissl body?

A

Prominent in neuron cell bodies with toluidine blue stain, Nissl bodies are stacks of rER.

  • They are so prominent b/c neurons are constantly making large amounts of proteins
25
Q

What is the embryonic origin of the PNS?

A

Both neurons and glia develop from the neural crest

26
Q

Describe the cell body of a neuron

A

large and euchromatic nucleus, prominent nucleolus, stacks of rER (Nissl bodies), visible in light microscope

27
Q

Describe the dendrites of a neuron

A

there are multiple per neuron attached to the cell body

  • they contain ribosomes
28
Q

Describe the axon of a neuron

A
  • One per neuron
  • originating from the axon hillock
  • contains microtubules, neurofilaments for axoplasmic transport and mitochondria
  • generally surrounded by myelin for insulation of action potential
29
Q

Describe the terminals of neuron axons (nerve endings)

A
  • nerve terminals contain neurotransmitters and form the synapses with other cells
  • terminals may be branched to form several synaptic endings attached to different postsynaptic cells

–> lesser branched or non-branched endings are often called boutons

30
Q

What is a neuromuscular junction?

A
  • Elaborate, specialized synaptic endings of neurons on muscle cells
  • axons split into several synaptic endings
  • narrow intercellular gap (synaptic cleft) separates pre- and postsynaptic cells
  • presynaptic axon terminal filled with storage organelles called synaptic vesicles that contain neurotransmitters
  • synapses release vesicles/neurotransmitters by exocytossi into synaptic cleft and they diffuse to postsynaptic cell receptors
31
Q

What are sensory receptors?

A

Cells or complex aggregates of receptive and supportive cells

32
Q

What is a sensory unit?

A

Includes the sensory receptor plus all the cells in the pathway of information transfer up to the point o fthe initial synaptic contact within the CNS

33
Q

What are the connective tissues surrounding neurons?

A

Epineurium = dense irregular connective tissue surrounds a peripheral nerve and fills the spaces between nerve fascicles

Perineurium = specialized connective tissue surrounding each nerve fascicle

Endoneurium = includes loose connective tissue surrounding each individual nerve fiber; contains blood vessels

34
Q

What are exteroceptors?

A

Receptors that react to stimuli from the external environment

i.e. temperature, toch, smell, sound, and vision

35
Q

What are Enteroceptors?

A

Receptors that react to stimuli from within the body

i.e. degree of filling or stretch of the alimentary canal, bladder, and blood vessels

36
Q

What are proprioceptors?

A

Receptors that react to stimuli from within the body, provide sensation of body position and muscle tone and movement

37
Q

What are astrocytes (astroglia)?

A
  1. Largest glia cells with many cytoplasmic processes; many cytoplasmic organelles such as intermediate filaments
  2. many processes contact blood vessels and nearly continuously envelop the vessels with “astroglia feet,” providing the basis of the blood-brain-barrier
  3. Surround most neurons and provide structural support.
    - also provide key metabolic support for ionic environment and uptake of metabolic waste and toxic molecules
38
Q

What occurs when CNS tissue is damaged? (in terms of astrocytes)

A

A specialized form of astroglia appears (reactive or stellar astrocytes).

  • fill the space of killed neurons and eventually form the glia scar
39
Q

What are oligodendrocytes (oligodendroglia)?

A
  1. Most numerous glial cell. Smaller than astrocytes with shorter, fewer processes.
    - nuclei and cytoplasm more condensed than astrocytes, contain ribosomes, mitochondria, microtubules
  2. form myelin sheath for CNS
    - found mostly in white matter, but also abundant in gray
40
Q

Why do neurons need a myelin sheath?

A

Myelin acts as an electrical insulator

  • allows for faster action potential conduction than unmyelinated neurons
41
Q

What are the nodes of Ranvier?

A

Small gaps between adjacent myelin segments (between myelinating cells)

42
Q

What is myelin?

A

Almost pur plasma membrane, is very rich in lipid

  • due to high lipid content (which is extracted during conventional paraffin embedding), myelinated axons in paraffin sections are badly distorted by artifacts
43
Q

What are Schwann Cells?

A

The myelinating cells of the PNS

  1. Main supporting cells of PNS
  2. Even form coating around unmyelinated axons (the smallest axons)
44
Q

What are microglia?

A

Smallest glial cells with highly condensed nuclei and short, thorn-like projections

  • NOT derived from neuroepithelium
  • resident phagocytotic cells of the CNS
  • accumulate at sites of injury andphagocytose debris (called Gitter cells)
45
Q

What are ependymal cells?

A

Cuboidal/columnar cells with apical microvilli and, frequently, one or more cilia that line the central canal of the spinal cord and ventricles of the brain

  • basal lamina has been pushed far away - to the perimeter of the CNS - and so these cells are like the apical cells of very highly stratified epithelium
  • joined by modified junctional complexes (no zonulae occludentes); allows CSF to exchange “freely”
46
Q

What are satellite cells?

A

Originating from neural crest, satellite cells are flattened supporting cells covering peripheral ganglia

  • maintain the environment for the nerve cell bodies, analagous to schwann cells on axons
47
Q
A

Module 2: MSK (11 decks)

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