Nervous system

Nervous Nervous SystemSystem

3 Important Functions of 3 Important Functions of the Nervous System:the Nervous System:

► It receives information from the It receives information from the environment and inside the body.environment and inside the body.

► It interprets the information it It interprets the information it receives.receives.

► It makes the body respond to the It makes the body respond to the information.information.

DIVISIONS OF THE DIVISIONS OF THE NERVOUS SYSTEMNERVOUS SYSTEM

2 Main Divisions of the Nervous 2 Main Divisions of the Nervous System:System:

1. Central Nervous System (CNS)1. Central Nervous System (CNS) It consists of the brain and the spinal cord.It consists of the brain and the spinal cord. It receives and sorts out information coming It receives and sorts out information coming

from the environment and from inside the from the environment and from inside the body and determines the appropriate action. body and determines the appropriate action.

2.2. Peripheral Nervous System Peripheral Nervous System (PNS)(PNS)

It is made up of nerves that extend It is made up of nerves that extend throughout the body.throughout the body.

It is through these nerve cells that It is through these nerve cells that communication between the central communication between the central nervous system and the body nervous system and the body tissues take place.tissues take place.

2 Divisions of the Peripheral 2 Divisions of the Peripheral Nervous System:Nervous System:

1.1.Somatic Nervous Somatic Nervous System (SNS)System (SNS)

2.2.Autonomic Nervous Autonomic Nervous System (ANS)System (ANS)

1. Somatic Nervous System (SNS)1. Somatic Nervous System (SNS)► It communicates with the skin and It communicates with the skin and

skeletal muscles.skeletal muscles.►The somatic nervous system is the part The somatic nervous system is the part

of the of the peripheral nervous system associated with the associated with the voluntary control of control of body movements through the action of body movements through the action of skeletal muscles, and with reception of skeletal muscles, and with reception of external stimuli, which helps keep the external stimuli, which helps keep the body in touch with its surroundings (e.g., body in touch with its surroundings (e.g., touch, hearing, and sight).touch, hearing, and sight).

►The system includes all the neurons The system includes all the neurons connected with muscles, skin and sense connected with muscles, skin and sense organs.organs.

2. Autonomic Nervous System (ANS) 2. Autonomic Nervous System (ANS) ► It communicates with smooth muscles, It communicates with smooth muscles,

heart muscles and glands. heart muscles and glands. ► It is the part of the peripheral nervous It is the part of the peripheral nervous

system that acts as a control system, system that acts as a control system, maintaining homeostasis in the body. maintaining homeostasis in the body. These maintenance activities are primarily These maintenance activities are primarily performed without conscious control or performed without conscious control or sensation. The ANS has far reaching sensation. The ANS has far reaching effects, including: heart rate, digestion, effects, including: heart rate, digestion, respiration rate, salivation, perspiration, respiration rate, salivation, perspiration, diameter of the pupils, micturition (the diameter of the pupils, micturition (the discharge of urine), and erection. Most of discharge of urine), and erection. Most of its actions are involuntary. its actions are involuntary.

2 Divisions of Autonomic 2 Divisions of Autonomic DivisionDivision

1. Sympathetic Nervous System1. Sympathetic Nervous System The sympathetic nerves speed The sympathetic nerves speed

up or slow down some body up or slow down some body processes.processes.

It is always active and becomes It is always active and becomes more active during times of more active during times of stress. stress.

2. Parasympathetic Nervous 2. Parasympathetic Nervous SystemSystem

► The parasympathetic nerves have The parasympathetic nerves have the opposite effect on the same the opposite effect on the same body processes. body processes.

““The sympathetic and parasympathetic The sympathetic and parasympathetic divisions typically function in divisions typically function in opposition to each other. But this opposition to each other. But this opposition is better termed opposition is better termed complementary in nature rather than complementary in nature rather than antagonistic. For an analogy, one may antagonistic. For an analogy, one may think of the sympathetic division as think of the sympathetic division as the accelerator and the the accelerator and the parasympathetic division as the parasympathetic division as the brake. The sympathetic division brake. The sympathetic division typically functions in actions requiring typically functions in actions requiring quick responses. The parasympathetic quick responses. The parasympathetic division functions with actions that do division functions with actions that do not require immediate reaction.”not require immediate reaction.”

The Nerve ImpulseThe Nerve Impulse

Each neuron is like a tiny biological Each neuron is like a tiny biological battery. Electrically charged molecules battery. Electrically charged molecules called called ionsions are found in varying are found in varying numbers inside and outside of each numbers inside and outside of each neuron. Two types of ions, positive and neuron. Two types of ions, positive and negative, can be found. The most negative, can be found. The most important important negative ion negative ion is chloride (Cl). is chloride (Cl). The most important The most important positive ions positive ions are are potassium (K) and sodium (Na).potassium (K) and sodium (Na).

When the neuron is not sending or When the neuron is not sending or receiving a signal, it is in a resting state. receiving a signal, it is in a resting state. The inside of the neuron is about -70 The inside of the neuron is about -70 millivolts. This electrical charge of a millivolts. This electrical charge of a neuron at rest is itsneuron at rest is its resting potential resting potential..

Message arriving from other Message arriving from other neurons changes the resting potential neurons changes the resting potential until it reaches a threshold, the point at until it reaches a threshold, the point at which a nerve impulse is fired or which a nerve impulse is fired or triggered. When a neuron reaches this triggered. When a neuron reaches this point (-50 millivolts), a nerve impulse or point (-50 millivolts), a nerve impulse or action potential action potential sweeps down the axon. sweeps down the axon.

Similar to a game of dominoes, Similar to a game of dominoes, when once the first domino drops, a when once the first domino drops, a rapid wave of falling dominoes zips rapid wave of falling dominoes zips through the end of the line, when a through the end of the line, when a nerve impulse is triggered near the nerve impulse is triggered near the soma, a wave of activity travels down soma, a wave of activity travels down the axon to the axon terminals.the axon to the axon terminals.

Parts of the Parts of the Nervous SystemNervous System

►Neurons or nerve cellsNeurons or nerve cells►Spinal cordSpinal cord►BrainBrain

NeuronsNeurons

Parts of NeuronsParts of Neurons

►DendritesDendrites receive nerve impulses and send them to receive nerve impulses and send them to

cell body cell body

►Cell bodyCell body contains the nucleus of the cellcontains the nucleus of the cell

►AxonsAxons send impulses from the cell body to other send impulses from the cell body to other

neuronsneurons

►Synapse - a very tiny space between Synapse - a very tiny space between the axon of a neuron and a dendrite of the axon of a neuron and a dendrite of another neuron, across which a another neuron, across which a message is transmitted. message is transmitted.

►myelin sheath - fatty layer of cells that myelin sheath - fatty layer of cells that covers the axons in the brain and covers the axons in the brain and spinal cord and acts as an insulator spinal cord and acts as an insulator and aids in the conduction of impulsesand aids in the conduction of impulses

►terminal buttons - small knobs at the terminal buttons - small knobs at the ends of the branched axon which are ends of the branched axon which are directly involved in transmitting a directly involved in transmitting a signal from one neuron to the next.signal from one neuron to the next.

Types of NeuronsTypes of Neurons►Sensory (afferent) neuronsSensory (afferent) neurons

receive stimuli from the environment and receive stimuli from the environment and carry them to the brain for interpretationcarry them to the brain for interpretation

►Motor (efferent) neuronsMotor (efferent) neurons relay messages from the brain to the relay messages from the brain to the

muscles or glandsmuscles or glands

► Interneurons/association neuronsInterneurons/association neurons connect the impulse from the axon of the connect the impulse from the axon of the

sensory neuron to the dendrite of the sensory neuron to the dendrite of the motor neuronmotor neuron

Neurons are similar to other Neurons are similar to other body cells because:body cells because:

►neurons are surrounded by a cell neurons are surrounded by a cell membrane;membrane;

►neurons have a nucleus that neurons have a nucleus that contains genes;contains genes;

►neurons contain cytoplasm, neurons contain cytoplasm, mitochondria and other organelles; mitochondria and other organelles; andand

►neurons carry out basic cellular neurons carry out basic cellular processes such as energy production.processes such as energy production.

Neurons differ from other body Neurons differ from other body cells because:cells because:

► neurons have specialized neurons have specialized extensions called dendrites extensions called dendrites and axons; andand axons; and

► neurons communicate with neurons communicate with each other through nerve each other through nerve impulse.impulse.

NeurotransmittersNeurotransmitters

If there is a gap between the If there is a gap between the neurons, why doesn’t the signal stop neurons, why doesn’t the signal stop when it reaches the terminal button? The when it reaches the terminal button? The answer involves special chemicals called answer involves special chemicals called neurotransmittersneurotransmitters, which are stored in , which are stored in tiny pockets called tiny pockets called synaptic vesiclessynaptic vesicles that that are located in the terminal buttons. These are located in the terminal buttons. These are substances that facilitate are substances that facilitate transmission of information from one transmission of information from one neuron to another.neuron to another.

Spinal CordSpinal Cord

►The spinal cord is a cylinder of nerve The spinal cord is a cylinder of nerve tissue as thick as a finger and about tissue as thick as a finger and about 45 centimeters long. It begins at the 45 centimeters long. It begins at the base of the skull and extends base of the skull and extends throughout most of the backbone. throughout most of the backbone.

► It is the link between the peripheral It is the link between the peripheral nervous system and the brain.nervous system and the brain.

►The spinal cord can also handle some The spinal cord can also handle some information coming from the senses information coming from the senses and provide motor responses that do and provide motor responses that do not come from the brain. This is called not come from the brain. This is called a a reflex actionreflex action. .

Components of the Spinal Components of the Spinal CordCord

►At the center of the cord is the At the center of the cord is the gray gray mattermatter. The gray matter contains the . The gray matter contains the cell bodies and dendrites of neurons. cell bodies and dendrites of neurons.

►Surrounding the gray matter is the Surrounding the gray matter is the white matterwhite matter. It contains the axons . It contains the axons of neurons that run lengthwise through of neurons that run lengthwise through the spinal cord. the spinal cord.

► It is also made up of bundle of It is also made up of bundle of interneuronal axons (interneuronal axons (tractstracts). Some ). Some tracts are tracts are ascendingascending (carrying (carrying messages to the brain); others are messages to the brain); others are descendingdescending (carrying messages from (carrying messages from the brain). the brain).

►The spinal cord is surrounded by The spinal cord is surrounded by membranes called membranes called meningesmeninges. .

BrainBrain

BrainBrain

►The brain is the body’s control center. The brain is the body’s control center. It receives messages from and sends It receives messages from and sends messages to all organs and tissues of messages to all organs and tissues of the body. It controls both voluntary the body. It controls both voluntary and involuntary activities. The brain and involuntary activities. The brain gives us the ability to learn, to reason, gives us the ability to learn, to reason, and to feel.and to feel.

►The brain is a mass of billions of The brain is a mass of billions of neurons. These neurons are neurons. These neurons are surrounded by cells called surrounded by cells called gliaglia, or , or glial cellsglial cells, which support (hold the , which support (hold the neurons in place) and supply them neurons in place) and supply them with nutrients. with nutrients.

►The brain is protected by the skull. It is The brain is protected by the skull. It is also protected by three layers of also protected by three layers of tissues called meninges. The inner tissues called meninges. The inner layer acts as a wall that prevents layer acts as a wall that prevents bacteria fro reaching the brain. The bacteria fro reaching the brain. The middle layer supplies it with nutrients middle layer supplies it with nutrients and oxygen. The outer layer lines the and oxygen. The outer layer lines the inner surface of the skull.inner surface of the skull.

3 Main Parts of the Brain3 Main Parts of the Brain

Brain StemBrain Stem► It is the lowest section of the It is the lowest section of the

brain which connects it to the brain which connects it to the spinal cord. It acts as a spinal cord. It acts as a pathway for messages pathway for messages traveling between some parts traveling between some parts of the brain and the spinal of the brain and the spinal cord. cord.

CerebellumCerebellum► It is at the back of the brain It is at the back of the brain

stem. It is concerned with the stem. It is concerned with the maintenance of posture and maintenance of posture and balance, and the coordination balance, and the coordination of movements.of movements.

CerebrumCerebrum► It is the largest part of the It is the largest part of the

brain. brain. ► It is the seat of human It is the seat of human

intelligence. intelligence.

Brain StemBrain Stem►It has three main It has three main parts:parts: MedullaMedulla PonsPons MidbrainMidbrain

Parts of the Brain StemParts of the Brain StemMedullaMedulla ► It controls It controls

involuntary involuntary activities such as activities such as breathing and breathing and heart rate.heart rate.

► It also controls It also controls some reflexes some reflexes that help the that help the organism organism maintain an maintain an upright posture.upright posture.

Parts of the Brain StemParts of the Brain Stem

PonsPons

► The pons, which The pons, which means bridge, means bridge, serves as a serves as a pathway, pathway, connecting the connecting the various parts of the various parts of the brain with each brain with each other.other.

Parts of the Brain StemParts of the Brain Stem

MidbrainMidbrain

► It controls the eye movements. It also It controls the eye movements. It also coordinates head movement with sight coordinates head movement with sight and sound.and sound.

CerebellumCerebellum

► It is at the back of It is at the back of the brain stem. It the brain stem. It is concerned with is concerned with the maintenance the maintenance of posture and of posture and balance, and the balance, and the coordination of coordination of movements.movements.

CerebrumCerebrumTwo Divisions of CerebrumTwo Divisions of Cerebrum

1. Left Hemisphere1. Left Hemisphere► It controls the right side of the body. It is the center for It controls the right side of the body. It is the center for

mathematical skills, speech, writing, and logical mathematical skills, speech, writing, and logical thinking. (language, speech, writing, calculation, time thinking. (language, speech, writing, calculation, time sense, rhythm, ordering of complex movements)sense, rhythm, ordering of complex movements)

2. Right Hemisphere2. Right Hemisphere► It controls the left side of the body. It is the center for It controls the left side of the body. It is the center for

creativity, artistic talent, and musical talent. (non-creativity, artistic talent, and musical talent. (non-verbal, perceptual skills, visualization, recognition of verbal, perceptual skills, visualization, recognition of patters, faces, melodies, recognition and expression of patters, faces, melodies, recognition and expression of emotion, spatial skills, simple language comprehension)emotion, spatial skills, simple language comprehension)

4 Lobes or Sections of the 4 Lobes or Sections of the BrainBrain

LobeLobe ConcernConcern

FrontalFrontal Speech and Speech and movement movement

TemporalTemporal Hearing and smell Hearing and smell

ParietalParietal Taste and touch Taste and touch

OccipitalOccipital Sight Sight

►The cerebrum is responsible for The cerebrum is responsible for thought, memory, sensation and thought, memory, sensation and action.action.

► It also regulates our higher intellectual It also regulates our higher intellectual processes.processes.

THE ORGANIZATION OF THE ORGANIZATION OF THE BRAINTHE BRAIN

► CerebrumCerebrum► Central CoreCentral Core► Limbic SystemLimbic System

Central CoreCentral Core

It is also known as the brainstem.It is also known as the brainstem. It regulates our primitive It regulates our primitive

behaviors (breathing, vomiting, behaviors (breathing, vomiting, sleeping, drinking, and sleeping, drinking, and temperature regulation)temperature regulation)

It also controls the involuntary It also controls the involuntary behaviors like sneezing and behaviors like sneezing and coughing.coughing.

Brain Structures of the Central Brain Structures of the Central CoreCore

►MedullaMedulla► CerebellumCerebellum► ThalamusThalamus

It plays a role in the It plays a role in the control of sleep and control of sleep and wakefulness.wakefulness.

►Reticular Reticular FormationFormation It plays a role It plays a role

in our ability to in our ability to focus attention focus attention on particular on particular stimuli.stimuli.

►HypothalamusHypothalamus It mediates It mediates

eating and eating and drinking. drinking.

It also regulates It also regulates endocrine endocrine activity.activity.

It plays a role in It plays a role in emotion and emotion and response to response to stress (it is stress (it is considered as considered as the stress the stress center).center).

Limbic SystemLimbic System

► This area controls our This area controls our emotions.emotions.

► The other brain structures of The other brain structures of the limbic system are:the limbic system are:

HypothalamusHypothalamus HippocampusHippocampus

► It has a special role in memory (storing It has a special role in memory (storing new events, but not for the retrieval of new events, but not for the retrieval of older memories).older memories).

HOW THE HOW THE NERVOUS SYSTEM NERVOUS SYSTEM

WORKSWORKS

From the Sense Organs to From the Sense Organs to the Sensory Neuronsthe Sensory Neurons

► The organs (eyes, ears, nose, The organs (eyes, ears, nose, tongue tongue and skin) contain special and skin) contain special cells called cells called sensory receptorssensory receptors. . Sensory Sensory receptors receive receptors receive information from information from the environment the environment in the form of light, in the form of light, sound, sound, chemical, heat, cold or chemical, heat, cold or pressure. pressure.

From the Sensory Neurons to From the Sensory Neurons to the Central Nervous System the Central Nervous System

► The sensory receptors in the The sensory receptors in the sense sense organs transmit messages organs transmit messages to to sensory sensory neuronsneurons. A message . A message may be relayed may be relayed from one neuron to from one neuron to another until it another until it reaches the reaches the brainbrain. . It is the brain that It is the brain that tells what a tells what a person sees, hears, person sees, hears, smells, tastes, smells, tastes, or feels.or feels.

From the Central Nervous From the Central Nervous System to the Motor System to the Motor

NeuronsNeurons► Within the Within the brainbrain, interneurons , interneurons

integrate and interpret the integrate and interpret the information received from one or information received from one or

more more sensory neuronssensory neurons..

From the Motor Neurons to From the Motor Neurons to the Body Organsthe Body Organs

► The The brainbrain relays the relays the appropriate appropriate response message response message to the to the motor motor neuronsneurons leading to leading to the different body the different body organs.organs.

AILMENTS OF THE AILMENTS OF THE NERVOUS SYSTEMNERVOUS SYSTEM

Multiple Sclerosis Multiple Sclerosis SymptomsSymptoms Characteristics/ Characteristics/

CausesCausesTreatmentTreatment

►Tingling Tingling sensationsensation►NumbneNumbnessss►Muscle Muscle weaknessweakness►Slurred Slurred speech speech

►Caused by virus, decreased Caused by virus, decreased sunlight exposure, low sunlight exposure, low Vitamin D, smoking, or Vitamin D, smoking, or genes.genes.►The fatty material covering The fatty material covering the axons of neurons in the the axons of neurons in the brain and spinal cord are brain and spinal cord are destroyed.destroyed.►In this case, the axons can In this case, the axons can no longer transmit no longer transmit messages. This results in the messages. This results in the weakening of the muscles weakening of the muscles and uncoordinated and uncoordinated movements. movements.

►Drugs to Drugs to lessen lessen pain pain ►Physical Physical therapytherapy

Polio (Poliomyelitis) Polio (Poliomyelitis) SymptomsSymptoms Characteristics/ Characteristics/


►FeverFever►Sore Sore throatthroat►VomitingVomiting►HeadacheHeadache

►It is an It is an infectious infectious disease caused disease caused by a virus, which by a virus, which destroys the destroys the motor neurons in motor neurons in the gray matter the gray matter of the spinal cord of the spinal cord or the brain. or the brain. ►This results in This results in the paralysis of the paralysis of the skeletal the skeletal muscles. muscles.

►There is no There is no drug treatment. drug treatment. Physical Physical therapy should therapy should be given.be given.►It can be It can be prevented by prevented by vaccination vaccination given during given during infancy. infancy.

Brain Tumor Brain Tumor SymptomsSymptoms Characteristics/ Characteristics/


►Muscle Muscle weaknessweakness►Loss of Loss of visionvision►Speech Speech difficultiesdifficulties

►It is an It is an abnormal growth abnormal growth in or on the in or on the brain. brain. ►It may arise It may arise from tissues from tissues within the skull within the skull or spread or spread through the through the bloodstream bloodstream from tumors in from tumors in some parts of the some parts of the body. body.

►Stereotactic Stereotactic radiosurgery radiosurgery (a surgical (a surgical technique technique involving the use involving the use of narrow beams of narrow beams of radiation, that of radiation, that are precisely are precisely targeted by targeted by stereotactic stereotactic methods to methods to destroy tumors)destroy tumors)

Meningitis Meningitis SymptomsSymptoms Characteristics/ Characteristics/


►HeadachHeadachee►FeverFever►NauseaNausea►VomitingVomiting►In some In some cases, cases, rashes rashes develop on develop on the skin the skin

►It is an It is an inflammation of the inflammation of the meninges that cover meninges that cover the brain and the the brain and the spinal cord.spinal cord.►It is caused by a It is caused by a virus or a bacterium.virus or a bacterium.►Viral meningitis is Viral meningitis is not serious but not serious but bacterial meningitis bacterial meningitis is. is.

►Treatment for Treatment for bacterial bacterial meningitis meningitis includes large includes large doses of doses of antibiotics.antibiotics.►Treatment for Treatment for viral meningitis viral meningitis are antiviral are antiviral drugs, drugs, analgesics for analgesics for pain and fever, pain and fever, and bed restand bed rest

Rabies Rabies SymptomsSymptoms Characteristics/ Characteristics/


►Low feverLow fever►HeadacheHeadache►Loss of Loss of appetiteappetite►RestlessnesRestlessnesss►Fear of Fear of waterwater

►It is a disease of It is a disease of mammals such as mammals such as dogs, cats, monkeys dogs, cats, monkeys and bats.and bats.►The virus is The virus is present in the present in the animal’s saliva and animal’s saliva and is transmitted to a is transmitted to a human being by a human being by a bite or by a lick over bite or by a lick over a break in the skin.a break in the skin.

►If a person is If a person is bitten by a dog, bitten by a dog, the wound should the wound should be thoroughly be thoroughly cleansed with cleansed with soap and water. soap and water. If a person has If a person has not been not been vaccinated vaccinated before, antirabies before, antirabies treatment is treatment is given given immediately.immediately.

StrokeStrokeSymptomsSymptoms Characteristics/ Characteristics/


►Altered smell, taste, Altered smell, taste, hearing, or vision (total hearing, or vision (total or partial) or partial) ►Decreased reflexes: Decreased reflexes: swallow, pupil reactivity swallow, pupil reactivity to light to light ►Decreased sensation Decreased sensation and muscle weakness of and muscle weakness of the face the face ►Balance problemsBalance problems►Altered breathing and Altered breathing and heart rateheart rate►Aphasia Aphasia ►Apraxia Apraxia ►Memory deficits Memory deficits

►A stroke occurs A stroke occurs when the blood when the blood supply to a part of supply to a part of the brain is cut off. the brain is cut off. ►The nerve cells in The nerve cells in the affected area the affected area die. When this die. When this happens, the victim happens, the victim may lose the ability may lose the ability to carry out to carry out functions controlled functions controlled by the affected part by the affected part of the brain.of the brain.

►RehabilitatioRehabilitationn

Encephalitis Encephalitis SymptomsSymptoms Characteristics/ Characteristics/


►HeadachHeadachee►FeverFever►DisturbeDisturbed d behavior, behavior, speech speech and and memory memory

►It is the It is the inflammation of the inflammation of the brain caused by a brain caused by a virus transmitted virus transmitted by mosquito bite. by mosquito bite.

►Antiviral Antiviral drugs drugs

Health & Medicine

Nervous system