A+P TEST 3

Sensory input

Information gathered by sensory receptors about
internal and external changes

Integration

Processing and interpretation of sensory input

Motor output

Activation of effector organs (muscles and glands)
produces a response

Somatic sensory fibers

convey impulses from
skin, skeletal muscles, and joints to CNS

Visceral sensory fibers

convey impulses from
visceral organs to CNS

Motor (efferent) division

Transmits impulses from CNS to effector organs
– Muscles and glands

Two divisions

– Somatic nervous system
– Autonomic nervous system

Neuroglia (glial cells)

small cells that surround and
wrap delicate neurons

Four main neuroglia support CNS neurons

• Astrocytes
  ▪ Microglial cells
  ▪ Ependymal cells
  ▪ Oligodendrocytes

Astrocytes

Most abundant,
versatile, and highly
branched of glial
cells
– Cling to neurons,
synaptic endings,
and capillaries
– Create blood-brain
barrier

Microglial cells

Small, ovoid cells with thorny processes that touch and
monitor neurons
– Migrate toward injured neurons
– Can transform to phagocytize microorganisms and
neuronal debris

Ependymal cells

– Range in shape from squamous to columnar
– May be ciliated

Oligodendrocytes

– Branched cells
– Processes wrap CNS nerve fibers, forming insulating myelin
sheaths in thicker nerve fibers

Satellite cells

– Surround neuron cell bodies in PNS
– Function similar to astrocytes of CNS

Schwann cells (neurolemmocytes)

– Surround all peripheral nerve fibers and form myelin sheaths
in thicker nerve fibers
▪ Similar function as oligodendrocytes
– Vital to regeneration of damaged peripheral nerve fibers

Neurons

(nerve cells) are structural units of nervous system

Large, highly specialized cells that conduct impulses

Special characteristics of neuron

– Extreme longevity (lasts a person’s lifetime)
– Amitotic, with few exceptions
– High metabolic rate: requires continuous supply of oxygen
and glucose
- All have cell body and one or more processes

retrograde axonal transport

Example: polio, rabies, and herpes simplex viruses, and
tetanus toxin

Myelin sheath

Protect and electrically insulate axon
▪ Increase speed of nerve impulse transmission

Myelinated fibers:

segmented sheath surrounds most long
or large-diameter axons

Nonmyelinated fibers:

do not contain sheath
▪ Conduct impulses more slowly

White matter

regions of the brain and spinal cord with
dense collections of myelinated fibers

Gray matter:

mostly neuron cell bodies and
nonmyelinated fibers

Interneurons

Lie between motor and sensory neurons

Multiple sclerosis (MS)

Myelin sheaths in CNS are destroyed when immune system attacks
myelin

Symptoms: visual disturbances, weakness, loss of muscular control,
speech disturbances, incontinence
• Treatment: drugs that modify immune system activity

synapses

functionally connects neurons

mediate information transfer

neuron—→neuron

neuron —→ effector

Presynaptic neuron

neuron conducting impulses toward
synapse (sends information)

Postsynaptic neuron

neuron transmitting electrical signal
away from synapse (receives information)

what is the most common type of synapse

chemical

2 separate parts of chemical synapse

Axon terminal of presynaptic neuron: contains
synaptic vesicles filled with neurotransmitter
– Receptor region on postsynaptic neuron’s membrane:
receives neurotransmitter

what are the 2 parts of a chemical synapse separated by

fluid-filled synaptic cleft