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mine > WEEK 4: Nervous System - TISSUE > Flashcards

WEEK 4: Nervous System - TISSUE Flashcards

1
Q

What is the function of the NS?

A

Sensory function: receptors in the PNS detect stimuli. Sensory information is transmitted to CNS.

Integrative function: CNS processes sensory information via integration and analysis. An appropriate outcome is decided.

Motor function: CNS transmits motor information to peripheral NS. Action carried out by effectors.

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2
Q

What is the organisation of the NS?

A

CNS:
- Brain
- Spinal cord

PNS:
* Cranial nerves
* Spinal nerves
* Ganglia
* Enteric plexuses in the small intestine
* Sensory receptors in skin

THREE FURTHER DIVISIONS OF THE PNS

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3
Q

What are the three divisons of the PNS?

A

Somatic NS:
- voluntary movement
- skeletal muscle

Autonomic NS:
- involuntary movement
- smooth muscle, cardiac muscle, glands

TWO DIVISIONS: sympathetic parasympathetic (associated with flight or fight response)

Enteric NS:
- new discovery
- involuntary movement
- smooth muscle, glands and endocrine cells in GI tract

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4
Q

What is a neuron?

A

= the fundamental units of the brain and nervous system.

Consist of =
- soma
- dendrites
- axon
- axon terminal
- synaptic end bulbs
- axon hillock
- schwann cells
- node of ranvier

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5
Q

What is a cell body (soma)?

A
  • contains nuclei and organelles.
  • Receives information from other neurons.
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6
Q

What are dendrites?

A
  • extensions from the cell body
  • site of input for neuron
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7
Q

What is an axon?

A
  • projection from cell body
  • impulses are conducted along here
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8
Q

What is an axon terminal?

A
  • the area where the electrical impulse is transferred to another cell
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9
Q

What is a synaptic end bulb?

A
  • The area that synapses with other cells
  • They don’t touch but come close to touching
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10
Q

What is an axon hillock?

A

= area between the cell body and the axon.

  • It integrates all information that the cell receives from the dendrite. It must determine a response.
  • Determines if it is positive and stimulatory or if it’s negative and inhibitory; essentially should the impulse continue.
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11
Q

What is a schwann cell?

A
  • cells that wrap around the axon
  • produce the myelin sheath
  • is a glial cell
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12
Q

What are nodes of ranvier?

A

= specialized axonal segments that lack myelin, allowing the saltatory conduction (skipping of the impulse) of action potentials.

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13
Q

What is the myelin sheath?

A

= an insulating layer, or sheath that forms around nerves, including those in the brain and spinal cord.

  • is a lipid and protein cover around axons
  • only in CNS
  • increases the speed of electrical impulse transfer
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14
Q

Structural classification of neurons

A

MULTIPOLAR:
- several dendrites, one axon
- all motor neurons

BIPOLAR:
- one main dendrite and one axon
- eye, ear and olfactory area

UNIPOLAR:
- a continuous process with a cell process of the side.
- most sensory neurons

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15
Q

Functional classification of neurons

A

SENSORY =
- From receptor to the CNS
- AFFERENT NEURONS (ARRIVE)

MOTOR =
- From CNS to effectors
- EFFERENT NEURONS (EXIT)

INTERNEURONS =
- In the CNS
- Process and integrate the information from the electrical impulse

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16
Q

What are neurogila?

A
  • All non-neuronal cells in the NS
  • Not electrically excitable
  • Able to multiply and divide (neurons can’t)
  • Make up half of the NS.
17
Q

Types of neuroglia?

A

6 TYPES:

CNS HAS 4:
- astrocytes
- oligodendrocytes
- microglia
- ependymal cells

PNS HAS 2:
- schwann cells
-satellite cells

18
Q

What do astrocytes cells do?

A
  • star shaped
  • Most numerous neuroglia
  • Provide support to neurons (contain fibers that make them strong)
  • Maintain blood-brain-barrier (they wrap around capillaries around blood vessels in brain to protect them)
  • Maintain local chemical environment (they store glucose because the brain can’t or struggles to)
19
Q

What do oligodendrocytes do?

A
  • Octopus-like and extensions wrap around the axons.
  • Fewer processes than an astrocyte
  • Form and maintain myelin sheath (Schwann cells produce myelin in PNS and these cells produce myelin in the CNS)
  • Can wrap around multiple axons (up to 50 from one cell)
20
Q

What are microglia?

A
  • Small cells with thin, spine like projections.
  • Function as phagocytes.
  • Remove cellular debris, microbes, damaged NS.
21
Q

What are ependymal cells?

A
  • Cuboidal cells with microvilli and cilia
  • Line ventricles and the central canal (the brain)
  • Produce and circulate CSF (cerebral spinal fluid)
22
Q

What are schwann cells?

A
  • Form and maintain myelin sheath.
  • Each Schwann cell myelin one axon and one specification
  • Involved in axon regeneration.
23
Q

What are satellite cells?

A
  • Surround cell bodies of neurons of PNS ganglia.
  • Provide structural support (cushion cell body)
  • Exchange material between cell bodies and interstitial fluid (fluid that surrounds the cells).
24
Q

What is neurogeneration?

A

= regrowth or repair of the NS or cells (neurons, axons, myelin, synapses)

25
Q

Difference between CNS and PNS nerve repair

A

CNS = little to no repair due to inhibitory influences from neuroglia, absence of growth-stimulating cues, and rapid formation of scar tissue.

PNS = repair possible if the cell body is intact; if Schwann cells are functional, and if the scare tissue formation doesn’t occur too rapidly.

26
Q

Steps of PNS regeneration steps

A
  • Chromatolysis
  • Wallerian degeneration
  • Formation or a regeneration tube
27
Q

PNS regeneration: chromatolysis

A
  • 24/48 hours after injury, Nissl bodies in cell body break up into different pieces
  • Are essentially rough endoplasmic reticulum which produce proteins (chromatolysis)
28
Q

PNS regeneration: wallerian degeneration

A
  • Day 3-5, the distal axon with swell and break up. The myelin will also begin to break.
  • The degeneration of the axon sheath = Wallerian degeneration.
29
Q

PNS regeneration: formation or regeneration tube

A
  • Macrophages phagocytize the damaged tissue.
  • Synthesis of RNA and protein accelerates, and this allows for the rebuilding of the axon.
  • Schwan cells divide and grow to form regeneration tube = this tube will guide the formation of the axon from proximal to distal side.
30
Q

Various collections of nervous tissue:

A
  • clusters of neuronal cell bodies
  • bundles of axons
  • white and grey matter
31
Q

What are CLUSTERS OF NEURONAL CELL BODIES?

A

PNS = ganglion

CNS = Nucleus

32
Q

What are BUNDLES OF AXONS?

A

PNS = nerve

CNS = tract

33
Q

What are WHITE AND GREY MATTER?

A

WHITE (only myelinated axons) AND GREY MATTER (everything by myelinated axon):

BRAIN AND WHITE = inner layers

SPINAL AND WHITE = outer layers

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