COM 1 Cytology week 3

Question 1

What is the PNS composed of

Answer 1

• Nerves
  -Gnaglia
  -Nerve endings

Question 2

What are peripheral nerves

Answer 2

Bundles of nerves wrapped in schwaan cells + connective tissue

Question 3

What do Schwann cells surround

Answer 3

Axons

Question 4

Schwann cells may or may not from myelin depending on what

Answer 4

• Axon diameter

Question 5

Explain the process how axons get myelinated by schwann cells

Answer 5

Schwann cell membrane wraps around axon many times

Forms thick myelin sheath made of lipid bilayers and membrane proteins

Each Schwann cell only myelinates one segment of one axon

Question 6

What is Myelin sheaths seen in the TEM as

Answer 6

• Major dense lines
• Intraperiod lines

Question 7

What are Schmidt-Lanterman clefts

Answer 7

Gaps in dense lines where cytoplasm can flow for maintenance

Question 8

What are the 3 functions of myelin

Answer 8

• Insulates axon
• Mainatins ionic environment
• Enables saltory conduction

Question 9

What are nodes or ranvier

Answer 9

Gaps between schwann cells

Question 10

What is Internodal Segment

Answer 10

Portion of axon wrapped by one Schwann cell

Question 11

Are the smallest axons unmyelinated or myelinated

Answer 11

unmyelinated

Question 12

Name all the differnces that Unmyelinated fibers dont have compared to myelinated fibers

Answer 12

• No myelin sheath
  -No nodes of ranvier
  -No saltory conduction
  -Slower conduction speed

Question 13

Why do unmyelinated fibers have no saltory conduction and slower conduction speed

Answer 13

• As the ions are evenly distrributed

Question 14

Name the 3 different connectve tissue layers in the PNS

Answer 14

• Endoneurium
  -Perineurium
  -Epineurium

Question 14

What does the Endoneurium connective tissue contain

Answer 14

• Reticular fibers, fibroblasts, capillaries

Question 14

What does the Endoneurium connectove tissue surround

Answer 14

• Axons and schwann cells

Question 15

What does perineurium wrap around

Answer 15

Fascicles

Question 15

What is perineurium made out of+ what does it form and why

Answer 15

• Flat fibrocytes joined by tight junctions
• Blood nerve barrier to regulate environemnt

Question 16

What does epineurium surround + additioanl function

Answer 16

-Entire nerves
+ fill spaces between fasciciles

Question 17

What is the structure of Epineurium -

Answer 17

• Outer dense irregular connective tissue

Question 18

What are nerves made out of

Answer 18

Bundles of axon

Question 19

What tyoe of apperance does myelinated fibers give nerves

Answer 19

• Whitish, shiny apperance

Question 20

What is the function of peripheral nerves

Answer 20

• Connect CNS to sensory organs and effector organs

Question 21

Name the types of peripheral nerves

Answer 21

• Afferent fibers
• Efferent fibers
  -Sensory nerves
  -Motor nerves
  -Mixed nerves

Question 22

What do mixed nerves contain

Answer 22

- Both afferent and effeent fibers

Question 23

What does motor nerves contain

Answer 23

only efferent fibers

Question 24

What does sensory nerves contsin

Answer 24

Only afferent fibers

Question 25

What is the function of efferent fibers

Answer 25

- Carry commands from the CNS to the effectors

Question 26

What is the function of the afferent fibers

Answer 26

- Carry signals to the CNS

Question 27

What is ganglia

Answer 27

Ovoid structures with neuronal cell bodies

Question 28

What do ganglia surround

Answer 28

Glial satellite cells

Question 29

Where is ganglia enclosed

Answer 29

Dense capsule

Question 30

Name the 2 types of ganglia

Answer 30

- Sensory Ganglia -Autonomic Ganglia

Question 31

Where is sensory ganglia found

Answer 31

- Cranial nerves -Dorsal roots of spinal nerves

Question 32

What does sensory ganglia recieve

Answer 32

- Afferent (sensory) impulses headign to the CNS

Question 33

What does sensory ganglia contain

Answer 33

- Contains pseudounipolar neurons

Question 34

What is the function of sensory ganglia

Answer 34

- Relay sensory info to the spinal cord grey mater

Question 35

What is the functions of the neurons in sensory ganglia

Answer 35

They relay info to the spinal cord gray matter

Question 36

What is the function of autonomic ganglia

Answer 36

- Regulate involuntary functions such as smooth muscle activity, glandular secretion, heart rate etc

Question 37

Name the 2 structures that can be found along autonomic nerves

Answer 37

- Peripheral ganglia -Intramural ganglia

Question 38

Name the 2 neuron chains that Autonomic nerves use

Answer 38

-Preganglionic neuron -Postganglionic neuron

Question 39

What does the neuron chain- preganglionic neuron use and where is it located

Answer 39

acetylcholine CNS

Question 40

Name the 2 divisions of the Autonomic Nervous system

Answer 40

- Sympathetic -Parasympathetic

Question 41

Where is the neuronal cell bodies of the preganglionic SYMPATHETIC nerves located

Answer 41

The thoracic and lumbar spinal cord

Question 42

Where is the neuronal cell bodies of the preganglionic PARASYMPATHETIC nerves

Answer 42

in the medulla, midbrain and sacral spinal ord

Question 43

Where is ganglia found in Sympathetic nervous system

Answer 43

Aling vertebral column

Question 44

Where is ganglia found in the parasympathetic nervous system

Answer 44

- Near or inside effector organs

Question 45

What is neural plasticity

Answer 45

The brains ability to re organize by forming new synapses

Question 46

Explain what happens during embryonic development in relation to neural plasticity

Answer 46

Excess neurons are produces and the neurons that dont form proper synapses undergo apoptosis

Question 47

What can injured neurons do in Adults

Answer 47

- They may grow new processes and form new synapses for functional recovery

Question 48

What is neural plastiticy and reformation controlled by

Answer 48

Neurotrophins which are growth factors from neurons and glial cells

Question 49

Where are neural stem cells present+ arounf

Answer 49

- Presnt in Adult CNS and around ependymal cells

Question 50

What can neuronal stem cells generate

Answer 50

- Neurons, astrocytes, and oligodendorcytes

Question 51

Can mature CNS neurons divide

Answer 51

- No

Question 52

Where do astrocytes poliferate + function

Answer 52

- At injury sites but can block axon regeneration

Question 53

When can the PNS axons regenerate

Answer 53

- If the cell body remains intact

Question 54

What happens to Distal Axon after injury

Answer 54

- Distal axon segments degenerate

Question 55

What happens to Schwann cells after injury

Answer 55

Schwann cells differentiate, loose myelin and proliferate

Question 56

What happens to macrophages after injury

Answer 56

- Clear debris and release neurotrophins

Question 57

Explain what happens to axons after injury

Answer 57

- Axon regowth begins , which is guided by schwann cells

Question 58

After injury Chromatolysis occurs, explain what happens in chromatolysis

Answer 58

- Cell body swells, Nucles moves peripherally and Nissl substance fades

Question 59

When does chromatolysis occur

Answer 59

After injury

Question 60

What are neuromas

Answer 60

Painfull swellings of nerve tissue

Question 61

What does a succesful regeneration depend on

Answer 61

Correct alignment of axons and schwann cell columns

Question 62

What causes neuromas

Answer 62

When the regeneration pathway is lost