Chapter 8-Nervous System
Functions: Autonomic nervous system
1. Receiving sensory input ● transmits action potentials from the CNS to
● Sensory receptors monitor numerous cardiac muscle, smooth muscle, and glands.
external and internal stimuli. ● involuntary (unconscious) control of internal
2. Integrating information
organs, blood vessels, and smooth and cardiac
● The brain and spinal cord are the major
muscles
organs for processing sensory input and
initiating responses. ● Can be influenced by thought and emotion.
3. Controlling muscles and glands ● Control involuntary functions
● The nervous system controls the major o Heartbeat
movements of the body. o blood pressure
4. Maintaining homeostasis o respiration
● The nervous system can stimulate or inhibit o perspiration
the activities of other systems to help
o digestion
maintain a constant internal environment.
● Two divisions
5. Establishing and maintaining mental activity
● The brain is the center of mental activity, o Sympathetic
including consciousness, memory, and o Parasympathetic
thinking.
Sympathetic Nervous System
Major Divisions of Nervous System
● Referred to as the ‘Fight or flight’
1. Central Nervous System (CNS) ● Prepares the individual for physical activity.
• consists of the brain and spinal cord ● Release adrenaline and noradrenaline
2. Peripheral Nervous System (PNS)
▪ Increases heart rate and blood pressure.
• consists of all the nervous tissue outside
the CNS ▪ Dilates respiratory passageways to
• nerves and ganglia increase airflow.
Peripheral Nervous System ▪ Inhibits digestive functions.
2 divisions:
Parasympathetic Nervous System
1. sensory (afferent)
● Referred to as the ‘Rest and digest’ system.
• includes nerves leading toward the CNS.
● Calms body to conserve and maintain energy.
• sensory nerves
2. motor (efferent) ▪ Activates digestion.
• includes nerves leading away from the
▪ Lowers heart rate, which lowers blood
CNS.
• motor nerves pressure.
a. somatic (somatomotor) ▪ Constricts air passageways, which
b. autonomic
decreases airflow.
Efferent Division
Enteric Nervous System
Somatic (somatomotor) nervous system
● a unique subdivision of the peripheral nervous
● transmits action potentials from the CNS to system.
skeletal muscles. ● has both sensory and motor neurons contained
● voluntary (conscious) control of our movements wholly within the digestive tract.
via skeletal muscle. ● can function without input from the CNS or
other parts of the PNS, although it is normally
, integrated with the CNS by sensory neurons and ● myelination of axon increases speed &
ANS motor neurons. efficiency of action potential generation
along axon.
Cells of the Nervous System
● The two types of cells that make up the nervous Unmyelinated axons
system.
● axons lack myelin sheaths.
o Neurons
● these axons rest in indentations of the
o glial cells (neuroglia)
oligodendrocytes in the CNS and the
NEURONS (nerve cells) Schwann cells in the PNS
● receive stimuli, conduct impulses, or action Multiple sclerosis
potentials, and transmit signals to other ● disease of myelin sheath that causes loss of
neurons or effector organs. muscle function.
● Three parts: ● Autoimmune condition
o Cell body (soma) ● may be initiated by viral infection.
o Dendrites (process) ● inflammation in brain and spinal cord with
o Axons (process) demyelination and sclerotic (hard) sheaths
● Cell body – contains a single nucleus that is the results in poor conduction of action potentials.
source of information for gene expression. ● symptoms include exaggerated reflexes, tremor,
● Dendrites – short, branching cytoplasmic and speech defects.
extensions; receive information from other
neurons or from sensory receptors and transmit Types of Neurons
the information toward the neuron cell body. ● Multipolar
● Axon – single long cell process extending from o has many projections: many
the neuron cell body.
dendrites and a single axon.
● Nissl bodies – organelles contained in the cell
o e.g., most CNS neurons and most
body.
motor neurons
● Axon hillock – a cone shaped projection, where
● Bipolar
the axon leaves the neuron cell body.
o has 2 processes: one dendrite and
● Myelin sheath (sheath of Schwann) - highly
one axon.
specialized insulating layer of cells surrounding
o e.g., Found in some special sensory
axons; formed by the cell processes of
organs (retina of eye & in nasal
oligodendrocytes in the CNS and Schwann cells
cavity)
in the PNS.
● Pseudo-unipolar
● Schwann cells – a series of neuroglial cells
o has a single process extending from
wrapping around the axons of some peripheral
cell body: one axon and no
nerves like tape, each spiraling around a fiber to
dendrites.
form a multilayered coating.
o e.g., Sensory neurons
● Nodes of Ranvier – gaps in the myelin sheath;
the area where ion movement can occur. Glial Cells (Neuroglia)
Myelinated axons ● primarily supportive cells of the CNS and PNS
● these cells do not conduct action potentials.
● axons with myelin sheaths
● far more numerous than neurons
● conduct action potentials more quickly
● most neuroglia retains the ability to divide.
(3-15 meters/sec) -- saltatory conduction via
● Types:
nodes of Ranvier.
o Astrocytes
o Ependymal cells
Functions: Autonomic nervous system
1. Receiving sensory input ● transmits action potentials from the CNS to
● Sensory receptors monitor numerous cardiac muscle, smooth muscle, and glands.
external and internal stimuli. ● involuntary (unconscious) control of internal
2. Integrating information
organs, blood vessels, and smooth and cardiac
● The brain and spinal cord are the major
muscles
organs for processing sensory input and
initiating responses. ● Can be influenced by thought and emotion.
3. Controlling muscles and glands ● Control involuntary functions
● The nervous system controls the major o Heartbeat
movements of the body. o blood pressure
4. Maintaining homeostasis o respiration
● The nervous system can stimulate or inhibit o perspiration
the activities of other systems to help
o digestion
maintain a constant internal environment.
● Two divisions
5. Establishing and maintaining mental activity
● The brain is the center of mental activity, o Sympathetic
including consciousness, memory, and o Parasympathetic
thinking.
Sympathetic Nervous System
Major Divisions of Nervous System
● Referred to as the ‘Fight or flight’
1. Central Nervous System (CNS) ● Prepares the individual for physical activity.
• consists of the brain and spinal cord ● Release adrenaline and noradrenaline
2. Peripheral Nervous System (PNS)
▪ Increases heart rate and blood pressure.
• consists of all the nervous tissue outside
the CNS ▪ Dilates respiratory passageways to
• nerves and ganglia increase airflow.
Peripheral Nervous System ▪ Inhibits digestive functions.
2 divisions:
Parasympathetic Nervous System
1. sensory (afferent)
● Referred to as the ‘Rest and digest’ system.
• includes nerves leading toward the CNS.
● Calms body to conserve and maintain energy.
• sensory nerves
2. motor (efferent) ▪ Activates digestion.
• includes nerves leading away from the
▪ Lowers heart rate, which lowers blood
CNS.
• motor nerves pressure.
a. somatic (somatomotor) ▪ Constricts air passageways, which
b. autonomic
decreases airflow.
Efferent Division
Enteric Nervous System
Somatic (somatomotor) nervous system
● a unique subdivision of the peripheral nervous
● transmits action potentials from the CNS to system.
skeletal muscles. ● has both sensory and motor neurons contained
● voluntary (conscious) control of our movements wholly within the digestive tract.
via skeletal muscle. ● can function without input from the CNS or
other parts of the PNS, although it is normally
, integrated with the CNS by sensory neurons and ● myelination of axon increases speed &
ANS motor neurons. efficiency of action potential generation
along axon.
Cells of the Nervous System
● The two types of cells that make up the nervous Unmyelinated axons
system.
● axons lack myelin sheaths.
o Neurons
● these axons rest in indentations of the
o glial cells (neuroglia)
oligodendrocytes in the CNS and the
NEURONS (nerve cells) Schwann cells in the PNS
● receive stimuli, conduct impulses, or action Multiple sclerosis
potentials, and transmit signals to other ● disease of myelin sheath that causes loss of
neurons or effector organs. muscle function.
● Three parts: ● Autoimmune condition
o Cell body (soma) ● may be initiated by viral infection.
o Dendrites (process) ● inflammation in brain and spinal cord with
o Axons (process) demyelination and sclerotic (hard) sheaths
● Cell body – contains a single nucleus that is the results in poor conduction of action potentials.
source of information for gene expression. ● symptoms include exaggerated reflexes, tremor,
● Dendrites – short, branching cytoplasmic and speech defects.
extensions; receive information from other
neurons or from sensory receptors and transmit Types of Neurons
the information toward the neuron cell body. ● Multipolar
● Axon – single long cell process extending from o has many projections: many
the neuron cell body.
dendrites and a single axon.
● Nissl bodies – organelles contained in the cell
o e.g., most CNS neurons and most
body.
motor neurons
● Axon hillock – a cone shaped projection, where
● Bipolar
the axon leaves the neuron cell body.
o has 2 processes: one dendrite and
● Myelin sheath (sheath of Schwann) - highly
one axon.
specialized insulating layer of cells surrounding
o e.g., Found in some special sensory
axons; formed by the cell processes of
organs (retina of eye & in nasal
oligodendrocytes in the CNS and Schwann cells
cavity)
in the PNS.
● Pseudo-unipolar
● Schwann cells – a series of neuroglial cells
o has a single process extending from
wrapping around the axons of some peripheral
cell body: one axon and no
nerves like tape, each spiraling around a fiber to
dendrites.
form a multilayered coating.
o e.g., Sensory neurons
● Nodes of Ranvier – gaps in the myelin sheath;
the area where ion movement can occur. Glial Cells (Neuroglia)
Myelinated axons ● primarily supportive cells of the CNS and PNS
● these cells do not conduct action potentials.
● axons with myelin sheaths
● far more numerous than neurons
● conduct action potentials more quickly
● most neuroglia retains the ability to divide.
(3-15 meters/sec) -- saltatory conduction via
● Types:
nodes of Ranvier.
o Astrocytes
o Ependymal cells
