Nervous Tissue Lecture 2

Question 1

Neuroglia

Answer 1

• Support, nourish, and protect neurons
• Smaller but more numerous than neurons
• Neuroglia make up about half the volume of CNS

Question 2

Astrocytes

Answer 2

• Largest and most numerous of neuroglia
• Star-shaped cells that support neurons
• Form the blood-brain barrier (BBB)
• BBB maintains selective permeability of capillaries, preventing harmful substances from entering CNS

Question 3

Oligodendrocytes

Answer 3

• Form myelin sheath around CNS axons
• Important for speed of AP conduction

Question 4

Microglia

Answer 4

• Phagocytes of the CNS
• Remove microbes and cellular debris during tissue repair

Question 5

Ependymal Cells

Answer 5

• Arranged in single layer along brain ventricles and spinal cord central canal
• Produce and circulate cerebrospinal fluid (CSF)

Question 6

Gliomas

Answer 6

• Brain tumors arising from glial cells
• Highly malignant and usually fatal
• Most common types: astrocytomas and oligodendrogliomas

Question 7

Satellite Cells

Answer 7

• Surround cell bodies of neurons in PNS
• Provide structural support
• Regulate material exchange between neuron and interstitial fluid

Question 8

Schwann Cells

Answer 8

• Form myelin sheaths of PNS neurons
• Similar function to oligodendrocytes in CNS

Question 9

Myelination of Neurons

Answer 9

• Myelination = insulation of axons by neuroglia
• Oligodendrocytes in CNS, Schwann cells in PNS
• Increases rate and efficiency of electrical impulse transmission
• Saltatory conduction

Question 10

CNS vs. PNS

Answer 10

• CNS: Oligodendrocytes myelinate multiple neurons via branches
• PNS: Schwann cells found on one neuron, wrapping around it

Question 11

Neurolemma

Answer 11

• Outermost layer of axons in PNS
• Made of Schwann cells
• Absent in CNS

Question 12

Nodes of Ranvier

Answer 12

• Gaps in myelination with high ion channel concentrations
• Allow action potentials to “skip” along axon, increasing speed
• Facilitate saltatory conduction

Question 13

Unmyelinated Neurons

Answer 13

• Often found in Schwann cells
• No myelin sheath formed
• Neuron exposed to extracellular environment
• Lack saltatory conduction, slower continuous conduction

Question 14

Grey and White Matter

Answer 14

Some regions in brain and spinal cord appear white or grey

Question 15

Grey Matter

Answer 15

Contains: cell bodies, dendrites, axon terminals, unmyelinated axons, neuroglia cells

Question 16

White Matter

Answer 16

Composed mainly of myelinated axons (appearing white)

Question 17

Difference in Grey and White Matter:

Answer 17

• In the brain, grey matter is superficial and white matter is deep
• Grey matter in cerebrum called cortex
• In spinal cord, white matter is superficial and grey matter is deep

Question 18

Collections of Nervous Tissue

Answer 18

• Cell bodies and axons typically grouped together in the body
• Different names based on location (CNS or PNS)

Question 19

Ganglia

Answer 19

Clusters of neuronal cell bodies in PNS

Question 20

Nuclei

Answer 20

Collection of neuronal cell bodies within CNS

Question 21

Nerves

Answer 21

• Bundles of axons in PNS
• Can be motor, sensory, or mixed

Question 22

Tracts

Answer 22

• Bundles of axons in CNS
• In spinal cord, ascending tracts carry sensory info to brain, descending tracts carry motor info from brain
• In brain, carry information between different brain areas

Question 23

Reflexes

Answer 23

• Fast, automatic responses to specific stimuli involving peripheral nerves and spinal cord
• Maintain homeostasis through rapid adjustments in organ/system function

Question 24

5 Components of a Reflex Arc:

Answer 24

• Stimulation of receptor
• Activation of sensory neuron
• Information processing in CNS via interneurons
• Activation of motor neuron
• Response of peripheral effector

Question 25

Stretch Reflex

Answer 25

• Monosynaptic reflex involving muscle spindles
• Regulates skeletal muscle length

Question 26

Postural Reflexes

Answer 26

Subset of stretch reflexes maintaining upright position

Question 27

Withdrawal Reflexes

Answer 27

• Polysynaptic reflex moving away from stimulus
• Strongest with painful stimuli
• Versatile due to involvement of interneurons

Question 28

Flexor Reflex

Answer 28

• Type of withdrawal reflex affecting limb muscles
  Example: Grabbing hot pan

Question 29

Crossed Extensor Reflexes

Answer 29

• Contralateral reflex coordinated with flexor reflex
• Accompanies flexion with extension of opposite side
• Example: Step on sharp object

Question 30

General Sensation

Concious Sensation

Answer 30

• Complex response involving sensation, integration, and response
• Example: Feeling spider on arm
• Response influenced by past experiences, preferences, and knowledge

Question 31

Integration of Sensation

Concious Sensation

Answer 31

Dissemination of sensory information to brain regions for decision-making
Response varies based on factors such as past experiences and preferences

Question 32

Voluntary Efferent Signals

Concious Sensation

Answer 32

Sent to skeletal muscles for response (e.g., shaking off spider)
Involves activation of sympathetic nervous system for fight or flight response (if scared of spiders)

Question 33

Multiple Sclerosis (MS)

Answer 33

Autoimmune disease causing degeneration of myelin sheath around CNS neurons

Question 34

Cause and Symptoms:

(MS)

Answer 34

• Idiopathic cause, likely genetic link
• Symptoms include fatigue, visual disturbances, paresthesia, muscle weakness, other neurological deficits

Question 35

Prognosis and Epidemiology

(MS)

Answer 35

Lower life expectancy (5 to 10 years)
High rates in Canada (over 90,000 affected, 1 in 400 people)
Possibly linked to vitamin D deficiencies
More common in females (~4x) and risk doubles with relatives