PHYSIOLOGY
Hall, J. E. (2016). Guyton and Hall Textbook of Medical Physiology (13th ed.). Elsevier.
Organization of the Nervous System, Basic
Functions of Synapses, and Neurotransmitters
GENERAL DESIGN OF THE NERVOUS SYSTEM o The skeletal motor nerve axis controls
skeletal muscle movement
CENTRAL NERVOUS SYSTEM NEURON: THE BASIC o Autonomic nervous system regulates smooth
FUNCTIONAL UNIT muscle, glands, and internal functions.
• The central nervous system (CNS) has over 100 billion • Motor control comes from different CNS levels,
neurons. A typical neuron, like those found in the including:
brain’s motor cortex, receives incoming signals 1. The spinal cord
through synapses, mostly on its dendrites and cell 2. The reticular substance in the medulla, pons,
body. Depending on the neuron type, it can have from and mesencephalon
a few hundred to 200,000 synaptic connections. 3. The basal ganglia
• The output signal travels through a single axon, which 4. The cerebellum
may branch out to different parts of the nervous 5. The motor cortex
system or the body. A key feature of synapses is that • Lower CNS regions handle automatic, reflexive
signals usually move in one direction— from the axon muscle responses, while higher regions manage
of one neuron to the dendrites of another. This ensures complex movements through thought processes.
signals follow the correct pathways for proper nervous
system functions. PROCESSING OF INFORMATION – “INTEGRATIVE”
FUNCTION OF THE NERVOUS SYSTEM
SENSORY PART OF THE NERVOUS SYSTEM – SENSORY
• The nervous system processes incoming information
RECEPTORS
to generate appropriate responses. Over 99% of
• The nervous system begins functioning when sensory
sensory information is ignored because it is
receptors detect stimuli. These receptors include
unimportant — such as the feeling of clothes on the
visual receptors in the eyes, auditory receptors in the
skin or background noise.
ears, and tactile receptors in the skin. Sensory
• However, when important sensory information is
experiences can trigger immediate reactions or be
detected, it is processed and directed to the right brain
stored as memories for future responses.
areas for integration and motor response. For
• The somatic sensory system transmits signals from
example, touching a hot stove triggers an immediate
the body’s surface and deeper structures to the CNS
reaction to pull the hand away, along with additional
through peripheral nerves. These signals are sent to
responses like moving the body and expressing pain.
multiple sensory areas, including:
1. The spinal cord ROLE OF SYNAPSES IN PROCESSING INFORMATION
2. The reticular substance in the medulla, pons, • Synapses are junctions between neurons where
and mesencephalon signals pass. They control how signals spread through
3. The cerebellum the nervous system. Some synapses allow signals to
4. The thalamus pass easily, while others are more restrictive.
5. The cerebral cortex
• Synaptic transmission can be influenced by
facilitatory and inhibitory signals, either enhancing or
MOTOR PART OF THE NARVOUS SYSTEM – EFFECTORS
blocking signal flow. Some neurons produce many
• The nervous system’s main role is to control body output impulses, while others generate only a few.
functions by regulating: Synapses selectively filter signals, blocking weak
1. Skeletal muscle contraction ones, amplifying certain ones, and directing them to
2. Smooth muscle contraction in internal organs different pathways.
3. Glandular secretions (both exocrine and
endocrine)
• These actions are called motor functions, and the
structures performing them are effectors.
Prepared by: Yam Flynge Ferrer
Email:
, STORAGE OF INFROMATION – MEMORY LOWER BRAIN OR SUBCORTICAL LEVEL
• Not all sensory information causes immediate action, • Most subconscious body activities are controlled by
but much of it is stored for future use. Memory storage lower brain structures, including the medulla, pons,
mainly occurs in the cerebral cortex, though smaller mesencephalon, hypothalamus, thalamus,
amounts are stored in the basal brain regions and cerebellum, and basal ganglia.
spinal cord. • Examples of lower brain functions:
• Memory formation relies on synapses. When o Blood pressure and respiration are regulated in
sensory signals repeatedly pass through certain the medulla and pons
synaptic pathways, those pathways become stronger o Balance and posture involve the cerebellum
— a process called facilitation. With repeated use, and reticular substance
these pathways can transmit impulses even without o Feeding reflexes, like salivation and lip licking,
new sensory input, allowing a person to recall past are controlled by the medulla, pons,
experiences as memories. mesencephalon, amygdala, and
• The exact mechanisms of long-term synaptic hypothalamus
facilitation are not fully understood, but they are o Emotions such as anger, excitement, pleasure,
crucial to memory. Stored memories help the brain and pain reactions can still occur even if much
process new information by comparing it with past of the cerebral cortex is damaged
experiences, allowing the nervous system to react
appropriately. HIGHER BRAIN OR CORTICAL LEVEL
• The cerebral cortex is:
MAJOR LEVELS OF CENTRAL o A large memory storehouse
NERVOUS SYTEM FUNCTION o Essential for precise and complex control of
• The human nervous system has inherited special lower brain functions
functions from different stages of evolution. These o Responsible for thought processes
functions are divided into three major levels in the • The cortex does not work alone—it always functions
central nervous system: together with lower brain centers. In fact, the lower
1. Spinal cord level brain centers initiate wakefulness in the cortex,
2. Lower brain (subcortical) level allowing access to stored memories and enabling
3. Higher brain (cortical) level thinking.
• Each part of the nervous system has its own role, but
SPINAL CORD LEVEL the cerebral cortex gives us the ability to use stored
• Many people think the spinal cord only carries signals knowledge and process complex thoughts.
between the brain and the body, but it does much
more. Even if the spinal cord is severed at the neck, COMPARISON OF THE NERVOUS
many important functions still occur. SYSTEM TO A COMPUTER
• Neuronal circuits in the spinal cord can: • When computers were first invented, scientists noticed
1. Produce walking movements that they share many similarities with the nervous
2. Trigger reflexes that pull the body away from pain system.
3. Activate postural reflexes that help support the o Computers have input circuits, similar to the
body against gravity sensory portion of the nervous system.
4. Control local blood vessels, digestion, and o Computers have output circuits, which function
urination like the motor portion of the nervous system.
• Instead of directly controlling the body, higher brain • In simple computers, output signals respond directly
levels often send commands to the spinal cord, which to input signals, just like spinal cord reflexes. However,
then carries out the necessary actions. in more complex computers, the output depends on
both new input signals and stored memory, similar to
how the higher nervous system processes
information.
• As computers become more advanced, they require a
central processing unit (CPU) to control the order of
Prepared by: Yam Flynge Ferrer
Email:
Hall, J. E. (2016). Guyton and Hall Textbook of Medical Physiology (13th ed.). Elsevier.
Organization of the Nervous System, Basic
Functions of Synapses, and Neurotransmitters
GENERAL DESIGN OF THE NERVOUS SYSTEM o The skeletal motor nerve axis controls
skeletal muscle movement
CENTRAL NERVOUS SYSTEM NEURON: THE BASIC o Autonomic nervous system regulates smooth
FUNCTIONAL UNIT muscle, glands, and internal functions.
• The central nervous system (CNS) has over 100 billion • Motor control comes from different CNS levels,
neurons. A typical neuron, like those found in the including:
brain’s motor cortex, receives incoming signals 1. The spinal cord
through synapses, mostly on its dendrites and cell 2. The reticular substance in the medulla, pons,
body. Depending on the neuron type, it can have from and mesencephalon
a few hundred to 200,000 synaptic connections. 3. The basal ganglia
• The output signal travels through a single axon, which 4. The cerebellum
may branch out to different parts of the nervous 5. The motor cortex
system or the body. A key feature of synapses is that • Lower CNS regions handle automatic, reflexive
signals usually move in one direction— from the axon muscle responses, while higher regions manage
of one neuron to the dendrites of another. This ensures complex movements through thought processes.
signals follow the correct pathways for proper nervous
system functions. PROCESSING OF INFORMATION – “INTEGRATIVE”
FUNCTION OF THE NERVOUS SYSTEM
SENSORY PART OF THE NERVOUS SYSTEM – SENSORY
• The nervous system processes incoming information
RECEPTORS
to generate appropriate responses. Over 99% of
• The nervous system begins functioning when sensory
sensory information is ignored because it is
receptors detect stimuli. These receptors include
unimportant — such as the feeling of clothes on the
visual receptors in the eyes, auditory receptors in the
skin or background noise.
ears, and tactile receptors in the skin. Sensory
• However, when important sensory information is
experiences can trigger immediate reactions or be
detected, it is processed and directed to the right brain
stored as memories for future responses.
areas for integration and motor response. For
• The somatic sensory system transmits signals from
example, touching a hot stove triggers an immediate
the body’s surface and deeper structures to the CNS
reaction to pull the hand away, along with additional
through peripheral nerves. These signals are sent to
responses like moving the body and expressing pain.
multiple sensory areas, including:
1. The spinal cord ROLE OF SYNAPSES IN PROCESSING INFORMATION
2. The reticular substance in the medulla, pons, • Synapses are junctions between neurons where
and mesencephalon signals pass. They control how signals spread through
3. The cerebellum the nervous system. Some synapses allow signals to
4. The thalamus pass easily, while others are more restrictive.
5. The cerebral cortex
• Synaptic transmission can be influenced by
facilitatory and inhibitory signals, either enhancing or
MOTOR PART OF THE NARVOUS SYSTEM – EFFECTORS
blocking signal flow. Some neurons produce many
• The nervous system’s main role is to control body output impulses, while others generate only a few.
functions by regulating: Synapses selectively filter signals, blocking weak
1. Skeletal muscle contraction ones, amplifying certain ones, and directing them to
2. Smooth muscle contraction in internal organs different pathways.
3. Glandular secretions (both exocrine and
endocrine)
• These actions are called motor functions, and the
structures performing them are effectors.
Prepared by: Yam Flynge Ferrer
Email:
, STORAGE OF INFROMATION – MEMORY LOWER BRAIN OR SUBCORTICAL LEVEL
• Not all sensory information causes immediate action, • Most subconscious body activities are controlled by
but much of it is stored for future use. Memory storage lower brain structures, including the medulla, pons,
mainly occurs in the cerebral cortex, though smaller mesencephalon, hypothalamus, thalamus,
amounts are stored in the basal brain regions and cerebellum, and basal ganglia.
spinal cord. • Examples of lower brain functions:
• Memory formation relies on synapses. When o Blood pressure and respiration are regulated in
sensory signals repeatedly pass through certain the medulla and pons
synaptic pathways, those pathways become stronger o Balance and posture involve the cerebellum
— a process called facilitation. With repeated use, and reticular substance
these pathways can transmit impulses even without o Feeding reflexes, like salivation and lip licking,
new sensory input, allowing a person to recall past are controlled by the medulla, pons,
experiences as memories. mesencephalon, amygdala, and
• The exact mechanisms of long-term synaptic hypothalamus
facilitation are not fully understood, but they are o Emotions such as anger, excitement, pleasure,
crucial to memory. Stored memories help the brain and pain reactions can still occur even if much
process new information by comparing it with past of the cerebral cortex is damaged
experiences, allowing the nervous system to react
appropriately. HIGHER BRAIN OR CORTICAL LEVEL
• The cerebral cortex is:
MAJOR LEVELS OF CENTRAL o A large memory storehouse
NERVOUS SYTEM FUNCTION o Essential for precise and complex control of
• The human nervous system has inherited special lower brain functions
functions from different stages of evolution. These o Responsible for thought processes
functions are divided into three major levels in the • The cortex does not work alone—it always functions
central nervous system: together with lower brain centers. In fact, the lower
1. Spinal cord level brain centers initiate wakefulness in the cortex,
2. Lower brain (subcortical) level allowing access to stored memories and enabling
3. Higher brain (cortical) level thinking.
• Each part of the nervous system has its own role, but
SPINAL CORD LEVEL the cerebral cortex gives us the ability to use stored
• Many people think the spinal cord only carries signals knowledge and process complex thoughts.
between the brain and the body, but it does much
more. Even if the spinal cord is severed at the neck, COMPARISON OF THE NERVOUS
many important functions still occur. SYSTEM TO A COMPUTER
• Neuronal circuits in the spinal cord can: • When computers were first invented, scientists noticed
1. Produce walking movements that they share many similarities with the nervous
2. Trigger reflexes that pull the body away from pain system.
3. Activate postural reflexes that help support the o Computers have input circuits, similar to the
body against gravity sensory portion of the nervous system.
4. Control local blood vessels, digestion, and o Computers have output circuits, which function
urination like the motor portion of the nervous system.
• Instead of directly controlling the body, higher brain • In simple computers, output signals respond directly
levels often send commands to the spinal cord, which to input signals, just like spinal cord reflexes. However,
then carries out the necessary actions. in more complex computers, the output depends on
both new input signals and stored memory, similar to
how the higher nervous system processes
information.
• As computers become more advanced, they require a
central processing unit (CPU) to control the order of
Prepared by: Yam Flynge Ferrer
Email:
