Chapter 11: Your Neurons and their Electrical Activity

1. What do parenchyma cells do?

2. What do stroma cells do?

3. What are the parenchyma cells of the nervous system?

4. Describe the neuron cell body:

Perform the function of an organ

Other parts of the cell extend outward from here

Contains single large nucleus

No centrioles—therefore it cannot divide

Rough ER is abundant – “chromatophilic substance” or “Nissl bodies”

Intermediate filament is neurofilament

Mitochondria in large numbers

Support the parenchyma

Neurons

5. Describe the dendritesCytoplasmic extensions from the cell body

Term dendrite means “branches” –very numerous and highly branched (several hundred per cell)

Contain organelles

Large amounts of intermediate filaments give strength

6. Describe the axon:Only one per neuron

Can be long

Plasma membrane is “axolemma”

Cytoplasm is “axoplasm”

7. What does a nerve fiber consist of?Axon or dendrites and the myelin surrounding them

8. What is the difference between CNS and PNS?CNS – central nervous system – brain and spinal cord

PNS – peripheral nervous system – all other nervous tissue

9. What are two types of stroma cells in the nervous system and what do they do?

Oligodendrocytes – provide support to axon or dendrite of CNS

Neurolemmocytes – provides support to axon or dendrite of PNS “Schwann cell”

10. How does the neurolemmocyte work?Wraps layers of its membrane around the axon or dendrite until 20-30 layers have built up. Then it wraps its cell body around the myelin sheath, this is called a neurolemma.

11. How does the oligodendrocyte work differently than the neurolemmocyte?

They do not wrap their cell body around the myelin sheath Each oligodendrocyte wraps portions of its membrane around several nerve fibers, not one

12. How does the above effect nerve damage?Axon can regrow if protected by neurolemma

Axon cannot regrow if protected by oligodendrocyte (damage to CNS cannot be repaired

13. Compare continuous conduction to saltatory conduction.Continuous – conduction in nonmyelinated fiber, action potential travels like a wave

Saltatory – conduction in myelinated fiber, action potential skips along fiber (gaps in myelin every mm or so). This is faster

14. Why does using an ice pack reduce pain?Pain travels along sensory nerve fibers. When cooled, the message travels slower, and therefore the brain receives fewer impuses

Type of neuron Type of fiber Direction of travel

Sensory Afferent fibersFrom receptor to CNS for interpretation

Motor Efferent fibersCarry impulses away from CNS to effector

Interneuron --------------------Interconnect with other neurons in CNS (brain)

15.

Make sure you saw the slides

Labeling of different neuron structures:

a. Bipolar B. Unipolar C. Multipolar

“Nerves” – bundles of axons

Nodes of Ranvier – short region of exposed axon between Schwann cells on neurons of the peripheral nervous system

Bipolar Neurons – cell body has 2 processes (1 axon, 1 dendrite) found in eyes, nose, ears

Unipolar Neurons – cell body has 1 process extending from it, which divides. One branch associated with dendrites near peripheral body part, other branch is entering brain or spinal cord

Multipolar Neurons – many processes from cell body (1 axon, others are dendrites) found in brain, spinal cord

Astrocytes – star shaped, found between neurons and blood vessels, provide support and aid metabolism, responds to injury of the brain, makes scar tissue

Ependymal cell – cuboidal or columnar, have cilia, form inner lining of spinal cord and form membrane covering inside of spaces within brain

Microglia – scattered through the CNS, phagocytize bacterial cells and cell debris, increase in number if brain or spinal cord is injured