- I learned that neurons play a crucial role in the nervous system by serving as messengers and receivers of electrical impulses, with different types such as sensory, motor, and interneurons carrying specific signals throughout the body.
- The central nervous system, comprised of the brain and spinal cord, is protected by various structures, including the vertebrae and cranial bones, and is responsible for processing information and coordinating body functions.
- The brain is complex and is divided into several parts, with the cerebrum handling conscious activities and higher functions, while the cerebellum is key for balance and coordination, and the brainstem manages basic life functions like breathing and heartbeat.
- The peripheral nervous system extends from the central nervous system to various body parts and is divided into the autonomic nervous system, which controls involuntary actions, and the somatic nervous system, which manages voluntary movements.
- I also learned about various injuries and disorders of the nervous system, such as concussions and multiple sclerosis, which can lead to significant impairments, underscoring the importance of care and protection for the nervous system.
Write 5 sentences about what you learned from the information sheet.
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Learning Targets
After studying this lesson, I will be able to
explain the functions and characteristics of neurons.
describe the central nervous system and the peripheral nervous system
discuss the functions of the parts of the brain.
discuss care of the nervous system
identify symptoms, causes, and treatment of various injuries, diseases, and disorders of the nervous system
Function of the Nervous System
It is your body’s communication network and control center. It coordinates all of your body’s actions and functions. It
senses changes not only within the body, but also outside of it in your environment and enables you to respond within
fractions of a second. This information is transmitted throughout your body by means of electrical charges (impulses) at
speeds of up to 280mph
Neurons (Nerve Cells)
Neurons are the messengers and receivers of electrical impulses. They have the memory capability of a thousand CD-
ROMs, each containing the Encyclopedia Britannica.
1. Sensory Neurons – carry signals from sense receptors into the central nervous system.
2. Motor Neurons – carry signals from the central nervous system to muscles or glands.
3. Interneurons – form all the electrical connections within the central nervous system itself.
The Central Nervous System
1. The Spinal Cord –
a downward extension of the brain, it is a cylinder of nerve tissue about 18 inches long and about as thick as
your index finger.
It is protected by the vertebrae, cerebrospinal fluid, and three layers of connective tissue called meninges.
2. The Brain
The largest, most complex part of the nervous system which helps you receive and process messages and
coordinate muscular movements. It is also involved with your emotions and everything you sense.
It weighs approximately three pounds and contains almost 100 billion neurons.
It reaches full size by age 6, and uses more than 20% of the oxygen you inhale.
It doesn’t fully mature until your approximately 25 years of age.
It is protected by eight cranial bones, three layers of the cranial meninges, and cerebrospinal fluid.
The brain cells produce electrical signals and send them along pathways called circuits which receive, process,
store, and retrieve information.
The brain creates its electrical signals by chemical means and depends on the many complicated chemical
substances the brain cells produce.
A. The Cerebrum
The largest, most complex part of the brain which is the site of most conscious and intelligent activities
It is divided into two halves called the cerebral hemispheres. The right hemisphere controls the muscular
activity of and receives sensory input from the left side of the body. The left hemisphere does the same for
the right half of the body
The left hemisphere is responsible for language, logic, arithmetic calculation, analysis, and critical thinking.
The right hemisphere is concerned with imagination and visual thinking (spatial relationships, form, artistic
activities, and emotional responses
1. Frontal Lobe – controls voluntary movements and language. The prefrontal areas of this lobe are
believed to be involved with intellect and personality.
2. Parietal Lobe – involved with sensory information such as heat, cold, pain, touch, and body position in
space.
3. Occipital Lobe – involved with sense of vision
4. Temporal Lobe – contains the senses of hearing and smell, as well as being involved with memory,
thought, and judgement.
B. The Cerebellum
The second largest part of the brain located below the occipital lobes of the cerebrum.
Concerned with maintaining posture and balance, and coordinating muscle movement. It receives impulses
from the balance organs of the inner ear and from muscles, then refines the orders sent to muscles to
coordinate movement and balance
C. The Brain Stem
A three inch long stalk of nerve cells and fibers that connects the spinal cord to the rest of the brain.
Controls involuntary basic functions of breathing, heart beat, and eye reflexes
1. Medulla Oblongata – the lowest part of the brain stem containing vital control centers that regulate
heartbeat, breathing, blood pressure, and digestion. It also controls swallowing, vomiting, sneezing and
coughing; receives and relays taste sensations from the tongue; and is involved with speech and tongue
movement.
2. Pons – the middle portion of the brain stem serving mainly as a pathway for nerve impulses passing to
and from the cerebrum. It also relays sensory information from the ear, face, and teeth as well as
signals that control jaw movement and facial expressions.
3. Midbrain – highest part of the brain stem which controls eye movement and the size and reaction of the
pupils
4. Thalamus – two egg-shaped lobes about the size of walnuts located above the midbrain which are
involved with receiving information from the eyes and ears, and also the touch and pressure receptors
of the skin.
5. Hypothalamus – located behind the eyes and under the thalamus, which controls various body
processes (metabolism, sexual development, and emotional responses) and keep the body conditions
balanced (body temperature, stimulate appetite, and regulate sleep)
The Peripheral Nervous System
Composed of the Autonomic Nervous System and the Somatic Nervous System
Consists of nerves that fan out from the central nervous system to the muscles, skin, internal organs, and glands
Consists of 12 cranial nerves that branch from the brain and 31 pairs of spinal nerves that branch from the spinal
cord.
1. The Autonomic Nervous System
Responsible for controlling the involuntary functions of the body (sweating, digestion, and heart rate)
Consists of the sympathetic and parasympathetic nervous systems which have opposing effects on the same
organ and act in conjunction and normally balance each other
a. Sympathetic Nervous System
Responds to the body’s needs during increased activity and in emergencies (“fight or flight response”) It
quickens the heartbeat and breathing rate and increases blood flow to the muscles.
Leads to all the body’s vital organs and glands
b. Parasympathetic Nervous System
Opposes the action of the sympathetic nervous system by slowing body functions
2. The Somatic Nervous System
Consists of sensory neurons that relay messages from receptors in the ears, eyes, nose, tongue and skin to the
Central Nervous System and motor neurons that transmit impulses from the central nervous system to
skeletal muscles which involves voluntary responses
Problems of the Nervous System
Possible Causes
Damage to nerve cells or injury to the head or spinal cord
Nerve tissue damaged by degenerative diseases
Use of drugs and alcohol, which destroys brain cells and cause nervous system disorders.
* In the US each year, over one million people sustain head injuries and an estimated 11,000 new cases of spinal
cord injury occur. These injuries may result from falls, sports or recreational activities, motor vehicle crashes,
physical assaults, or gunshot wounds.
Head Injuries
1. Concussion: The immediate and short-lived impairment of neurological function due to either direct trauma (a
blow to the head), or indirect trauma (a fall where vibrations travel up the spinal column to the brain).
Because the brain is suspended in fluid, a blow to the head can create an injury either at the point of contact
or on the opposite side to it (contracoup).
Depending on the force of the blow and the person’s tolerance to withstand such a blow, varying degrees of
cerebral hemorrhage (bleeding), swelling and tissue laceration may occur which causes pathological changes
to occur
Concussions are cumulative, with each successive concussion causing more severe damage
Post concussion syndrome may develop with symptoms including impairment of short-term memory and
problem solving ability, attention and concentration difficulties, anxiety, frequent headaches, seizures,
muscle weakness, and alteration of emotions and personality. These symptoms may last for weeks, months,
or even years.
If a person receives a second concussion while still recovering from the initial concussion, a condition known
as “Second Impact Syndrome” may occur, which results in a failure of the autonomic nervous system, diffuse
swelling of the brain, and death.
2. Cerebral contusions: bruising of the brain following a blow to the head, which causes internal bleeding from
injured blood vessels.
Epidural Hematoma – a hematoma in the space between the skull and the meninges which is caused by a
rupture of an artery resulting in rapid deterioration of neurological function.
Subdural Hematoma – a hematoma in the space between the meninges and the brain caused by a ruptured
vein. Since bleeding is slower, a person may not show symptoms until hours, days or even weeks later
Spinal Cord Injuries
Trauma or swelling of the spinal cord or the tissue surrounding it can result in temporary loss of nerve function.
If the spinal cord has been severed or damaged beyond repair, paralysis usually occurs.
An injury to the upper part of the spinal cord may result in quadriplegia, or paralysis of both upper and lower
limbs.
An injury to the lower part of the spinal cord may result in paraplegia or paralysis of both lower limbs.
Degenerative Diseases
Parkinson’s Disease – results in the destruction of nerve cells in an area of the brain that helps coordinate skeletal
muscle movement. It is a progressive disorder, meaning that it gradually involves more and more nerve cells. As the
nerve cells are destroyed, muscle function is impaired. Symptoms include uncontrolled muscle tremors and increased
muscle rigidity. There is no known cause or cure at present.
Multiple Sclerosis – involves the destruction of the myelin sheath that surrounds the axons of neurons in the Central
Nervous System. The scar tissue that remains on the neuron interferes with the conduction of nerve impulses, and
voluntary control of muscles decreases. With each new attack, loss of nerve function increases. Multiple Sclerosis is an
autoimmune disease in which the body attacks its own tissue.
Alzheimer’s Disease – results when neurons in the brain are destroyed. If neurons become clogged with protein
deposits, they are unable to transmit impulses. The result is confusion, loss of memory, and gradual mental
deterioration. There is no known cause or cure for Alzheimer’s disease at the present time.
Other Disorders and Problems
Epilepsy – a disorder of the nervous system that is characterized by recurrent seizures - sudden episodes of
uncontrolled electrical activity in the brain. Seizures may be slight and brief, involving little body movement; or they
may be quite severe, involving muscle contractions throughout the entire body. It can be caused by brain damage
before or during birth, infections, head injury, withdrawal from drugs or alcohol, or exposure to toxins. Medications
can help control seizures so that a person with epilepsy can lead a normal, healthy life.
Cerebral Palsy – refers to a group of non-progressive neurological disorders that are the result of damage to the brain
before, during, or just after birth or in early childhood. Causes may include infections such as encephalitis or
meningitis, head injury, or exposure to radiation before birth. Physical therapy, braces to enable walking, and
medication can help cerebral palsy patients be independent and participate in everyday activities.
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