Nervous Tissue Lecture 2 Flashcards
1
Q
Neuroglia
A
- Support, nourish, and protect neurons
- Smaller but more numerous than neurons
- Neuroglia make up about half the volume of CNS
2
Q
Astrocytes
A
- 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
3
Q
Oligodendrocytes
A
- Form myelin sheath around CNS axons
- Important for speed of AP conduction
4
Q
Microglia
A
- Phagocytes of the CNS
- Remove microbes and cellular debris during tissue repair
5
Q
Ependymal Cells
A
- Arranged in single layer along brain ventricles and spinal cord central canal
- Produce and circulate cerebrospinal fluid (CSF)
6
Q
Gliomas
A
- Brain tumors arising from glial cells
- Highly malignant and usually fatal
- Most common types: astrocytomas and oligodendrogliomas
7
Q
Satellite Cells
A
- Surround cell bodies of neurons in PNS
- Provide structural support
- Regulate material exchange between neuron and interstitial fluid
8
Q
Schwann Cells
A
- Form myelin sheaths of PNS neurons
- Similar function to oligodendrocytes in CNS
9
Q
Myelination of Neurons
A
- Myelination = insulation of axons by neuroglia
- Oligodendrocytes in CNS, Schwann cells in PNS
- Increases rate and efficiency of electrical impulse transmission
- Saltatory conduction
10
Q
CNS vs. PNS
A
- CNS: Oligodendrocytes myelinate multiple neurons via branches
- PNS: Schwann cells found on one neuron, wrapping around it
11
Q
Neurolemma
A
- Outermost layer of axons in PNS
- Made of Schwann cells
- Absent in CNS
12
Q
Nodes of Ranvier
A
- Gaps in myelination with high ion channel concentrations
- Allow action potentials to “skip” along axon, increasing speed
- Facilitate saltatory conduction
13
Q
Unmyelinated Neurons
A
- Often found in Schwann cells
- No myelin sheath formed
- Neuron exposed to extracellular environment
- Lack saltatory conduction, slower continuous conduction
14
Q
Grey and White Matter
A
Some regions in brain and spinal cord appear white or grey
15
Q
Grey Matter
A
Contains: cell bodies, dendrites, axon terminals, unmyelinated axons, neuroglia cells
16
Q
White Matter
A
Composed mainly of myelinated axons (appearing white)
17
Q
Difference in Grey and White Matter:
A
- 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
18
Q
Collections of Nervous Tissue
A
- Cell bodies and axons typically grouped together in the body
- Different names based on location (CNS or PNS)
19
Q
Ganglia
A
Clusters of neuronal cell bodies in PNS
20
Q
Nuclei
A
Collection of neuronal cell bodies within CNS
21
Q
Nerves
A
- Bundles of axons in PNS
- Can be motor, sensory, or mixed
22
Q
Tracts
A
- 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
23
Q
Reflexes
A
- Fast, automatic responses to specific stimuli involving peripheral nerves and spinal cord
- Maintain homeostasis through rapid adjustments in organ/system function
24
Q
5 Components of a Reflex Arc:
A
- Stimulation of receptor
- Activation of sensory neuron
- Information processing in CNS via interneurons
- Activation of motor neuron
- Response of peripheral effector
25
Stretch Reflex
* Monosynaptic reflex involving muscle spindles
* Regulates skeletal muscle length
26
Postural Reflexes
Subset of stretch reflexes maintaining upright position
27
Withdrawal Reflexes
* Polysynaptic reflex moving away from stimulus
* Strongest with painful stimuli
* Versatile due to involvement of interneurons
28
Flexor Reflex
* Type of withdrawal reflex affecting limb muscles
Example: Grabbing hot pan
29
Crossed Extensor Reflexes
* Contralateral reflex coordinated with flexor reflex
* Accompanies flexion with extension of opposite side
* Example: Step on sharp object
30
General Sensation
## Footnote
Concious Sensation
* Complex response involving sensation, integration, and response
* Example: Feeling spider on arm
* Response influenced by past experiences, preferences, and knowledge
31
Integration of Sensation
## Footnote
Concious Sensation
Dissemination of sensory information to brain regions for decision-making
Response varies based on factors such as past experiences and preferences
32
Voluntary Efferent Signals
## Footnote
Concious Sensation
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)
33
Multiple Sclerosis (MS)
Autoimmune disease causing degeneration of myelin sheath around CNS neurons
34
Cause and Symptoms:
## Footnote
(MS)
* Idiopathic cause, likely genetic link
* Symptoms include fatigue, visual disturbances, paresthesia, muscle weakness, other neurological deficits
35
Prognosis and Epidemiology
## Footnote
(MS)
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
