Transcript Supporting cells

Chapter 7 – Part 1
The Nervous System
Functions of the Nervous System
1. Sensory input – gathering information
 To monitor changes occurring inside and
outside the body
 Changes = stimuli
2. Integration
 To process and interpret sensory input and
decide if action is needed
Functions of the Nervous System
3. Motor output
 A response to integrated stimuli
 The response activates muscles or glands
Structural Classification of the
Nervous System
1. Central nervous system (CNS)
 Consist of the brain and spinal cord
 Act as the integrating and command center
 Interpret incoming sensory information and
issue instructions
Structural Classification of the
Nervous System
2. Peripheral nervous system (PNS)
 Nerves outside the brain and spinal cord
 These nerves serve as communication
lines.
 They link all parts of the body by carrying
impulses from the sensory receptors to the
CNS and from the CNS to the appropriate
glands or muscles.
Functional Classification of the
Peripheral Nervous System
 Sensory (afferent) division
 Nerve fibers that carry information to the
central nervous system
 Keeps the CNS
constantly informed
of events going on
both inside and
outside the body.
Functional Classification of the
Peripheral Nervous System
 Motor (efferent) division
 Nerve fibers that carry impulses away from
the central nervous system
 These impulses
activate muscles
and glands; that is,
they effect (bring
about) a motor
response.
Functional Classification of the
Peripheral Nervous System
 Motor (efferent) division
 Two subdivisions
1. Somatic nervous system = voluntary
 Allows us to consciously control our skeletal
muscles.
2. Autonomic nervous system = involuntary
 Regulates the activity of the smooth and
cardiac muscles and glands.
 The ANC has two parts: The sympathetic
and parasympathetic (Each typically brings
about opposite effects)
Organization of the Nervous System
Nervous Tissue
 Made up of two principal types of cells:
1. Supporting cells
 Functions: support, insulate, and protect
 Not able to transmit nerve impulses
 Never lose their ability to divide, whereas
most neurons do.
 Most brain tumors are formed by neuroglia
cells.
2. Neurons
• Are able to transmit nerve impulses
Supporting Cells
 Supporting cells of the CNS:
1.
2.
3.
4.
Astrocytes
Microglia
Ependymal
Oligodendrocytes
Supporting cells of the PNS:
1. Schwann cells
2. Satellite cells
Nervous Tissue: Support Cells of
the CNS (Neuroglia)
 Astrocytes
 Abundant, starshaped cells
 Brace neurons
 Form a living barrier
between capillaries
and neurons
 Help protect the neurons from harmful substances
that might be in the blood.
 Control the chemical environment of
the brain
 Pick up excess ions and recapture released
neurotransmitters
Nervous Tissue: Support Cells of
the CNS
 Microglia
 Spider-like phagocytes
 Dispose of debris (such
as dead brain cells and
bacteria)
 Ependymal cells
 Line cavities of the
brain and spinal
cord
 Circulate
cerebrospinal
fluid
Nervous Tissue: Support Cells of
the CNS
 Oligodendrocytes
 Wrap their flat
extensions tightly
around the nerve
fibers.
 Produce myelin
sheath (fatty insulating
coverings) around
nerve fibers in the
CNS
Nervous Tissue: Support Cells of
the PNS
 Satellite cells
 Protect and cushion neuron cell bodies
 Schwann cells
 Form myelin sheath around nerve fibers in
the PNS
Nervous Tissue: Neurons
 Neurons = nerve cells
 Cells specialized to transmit messages
 Major regions of neurons
 Cell body – nucleus and metabolic
center of the cell
 Processes – fibers that extend from the
cell body
Neuron Anatomy
 Cell body
 Nissl substance
– specialized
rough ER
 Neurofibrils –
intermediate
cytoskeleton
(filaments) that
maintains cell
shape
Neuron Anatomy
 Cell body
 Nucleus
 Large nucleolus
 Contains the
usual organelles
except for
centrioles
Neuron Anatomy
 Extensions
(processes)
outside the cell
body
 Dendrites –
conduct
impulses toward
the cell body
 Axons – conduct
impulses away
from the cell
body
Processes or Extensions
 Processes vary in length from
microscopic to 3-4 feet
 The longest one in humans reach
from the lumbar region of the spine to
the big toe.
 Neurons may have hundreds of the
branching dendrites, depending on the
neuron type.
 Each neuron only has one axon.