Page 36 - Demo 1

Nervous ssue also consists of neuroglia, cells that supply the neurons
with nutrients, support and insulaon. Schwann cells are a type of neuroglial
cells that encircle long nerve fibers within nerves, forming a protecve coang on
the axons. This protecve coang is called the myelin sheath. The myelin sheath
enables nerve impulses to travel much more quickly down the axon.

Cell Modificaons
In both plants and animals, some cells become modified to perform
special funcons that promote survival of the organisms. These cell modificaons
include trichomes and root hairs in plants; flagella, cilia, and microvilli in
animals.
Trichomes are outgrowths of the epidermal layer that occur on the
plant shoot and on the surfaces of stems and leaves. They play an important
role in regulang the heat and water balance of the leaves, similar to how a hairy
coang offers insulaon to an animal. Trichomes vary greatly in form, from
rounded-p to globular-p forms. The presence of trichomes makes plants feel
prickly or hairy and discourage insects from eang the leaves or stems. Other
trichomes secrete a scky or toxic substance that may ward off potenal
herbivores.

Figure 21. Sample of trichome types
Source: http://botany.csdl.tamu.edu/FLORA/Wilson/tfp/veg/trichomes.gif

Root hairs are p-growing extensions of root epidermal cells that
promote the nutrient uptake ability of the plant because they keep the root in

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