PNS CNS Neuron Conduction Disease Nervous System Role

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PNS & CNS Neuron Conduction Disease Nervous System

PNS & CNS Neuron Conduction Disease Nervous System

Role of nervous system • To transmit information rapidly • The brain receives information

Role of nervous system • To transmit information rapidly • The brain receives information about the environment and responds accordingly

How the nervous system works 1. Detection of stimulus Sensory neurons 2. Processing in

How the nervous system works 1. Detection of stimulus Sensory neurons 2. Processing in brain 3. Response in other part of body Motor neurons Fig. 48. 1

The Basic Nerve Circuit 2. Processing Central Nervous System Brain and Spinal Cord Sensory

The Basic Nerve Circuit 2. Processing Central Nervous System Brain and Spinal Cord Sensory Neurons Motor Neurons Peripheral Nervous System Sensory receptors External Senses Internal Senses 1. Sensory Input Effector cells Voluntary muscle Involuntary muscle 3. Motor Output

Components of the Nerve Circuit Function Description Components Sensory Input Detect stimulus Sensory receptors

Components of the Nerve Circuit Function Description Components Sensory Input Detect stimulus Sensory receptors Sensory neurons Processing Analyze information Brain & spinal cord (CNS) Motor Output Response in body Motor neurons Effector cells

Simplest type of nerve circuit • Reflex: rapid, involuntary responses to stimuli • Processing

Simplest type of nerve circuit • Reflex: rapid, involuntary responses to stimuli • Processing of the stimulus doesn’t happen in the brain • Processing occurs in the spinal cord • The electrical impulse is sent faster so the body responds automatically without “thinking”

Examples of reflexes • Pupillary reflex: occurs when light shines in eyes • Knee-jerk

Examples of reflexes • Pupillary reflex: occurs when light shines in eyes • Knee-jerk reflex: occurs when tendon below kneecap is tapped

Peripheral Nervous System (PNS) • Composed of all the neurons that communicate between the

Peripheral Nervous System (PNS) • Composed of all the neurons that communicate between the body and the central nervous system (brain & spinal cord) • Relays information about environment to the brain • Relays information from brain to body

Organization of the PNS Peripheral Nervous System Sensory Division Motor Division Sensory receptors Effector

Organization of the PNS Peripheral Nervous System Sensory Division Motor Division Sensory receptors Effector cells External Sensing Internal Sensing Voluntary System Involuntary System Fig. 48. 17

Types of senses • Sensing the external environment – Somatic senses: skin, muscle, joints

Types of senses • Sensing the external environment – Somatic senses: skin, muscle, joints – Special senses: vision, hearing, smell, taste, touch • Sensing the internal environment – Visceral senses – e. g. fullness of stomach, blood pressure

Sensory Receptors • Detect a specific type of stimulus Examples Stimuli Location Mechanoreceptors Pressure,

Sensory Receptors • Detect a specific type of stimulus Examples Stimuli Location Mechanoreceptors Pressure, movement Skin, muscles, ears Photoreceptors Light Eyes Chemoreceptors Chemicals Nose, mouth Thermoreceptors Temperature Skin Nociceptors Pain Skin

Organization of the PNS Peripheral Nervous System Sensory Division Motor Division Sensory receptors Effector

Organization of the PNS Peripheral Nervous System Sensory Division Motor Division Sensory receptors Effector cells External Sensing Internal Sensing Voluntary System Involuntary System Fig. 48. 17

Motor (Effector) Cells • Carries out body’s response to a stimulus • Carry information

Motor (Effector) Cells • Carries out body’s response to a stimulus • Carry information from the CNS to the cells that will carry out instructions • Involuntary system: respond to stimuli by sending signals to smooth muscle, cardiac muscle and organs of the body • Voluntary system: responds to stimuli by sending signals to skeletal muscles

Anatomy of a neuron http: //www. whitney. ufl. edu/images/zacharias-rat. YFP-synapse. jpg

Anatomy of a neuron http: //www. whitney. ufl. edu/images/zacharias-rat. YFP-synapse. jpg

The neuron • Nerve: a group of neurons bundled together • Neuron = nerve

The neuron • Nerve: a group of neurons bundled together • Neuron = nerve cell • Neuron: the structural and functional unit of the nervous system • Mature neurons lose ability to undergo cell division

Components of a neuron Fig. 48. 2 a, c

Components of a neuron Fig. 48. 2 a, c

Components of a neuron Component Cell body Dendrites Axon Myelin Sheath Description Contain nucleus

Components of a neuron Component Cell body Dendrites Axon Myelin Sheath Description Contain nucleus & organelles Function Carries out basic cell functions Multiple short, Receives input from branched extensions other neurons Sends information to Single long extension other neurons Lipid layer found only Insulates the axon on axon

Myelin Sheath • Myelin sheath (lipid) insulates the axon • Analogy: insulation around wires

Myelin Sheath • Myelin sheath (lipid) insulates the axon • Analogy: insulation around wires

Myelin Sheath • Only wrapped around axons • not found on other parts of

Myelin Sheath • Only wrapped around axons • not found on other parts of the neuron

Neuron Function • Conducts electrical signals called impulses from one area of the body

Neuron Function • Conducts electrical signals called impulses from one area of the body to another • Electrical impulse is the way neuron communicate information

Direction of impulse conduction Dendrites Cell body Axon terminal Fig. 48. 2 a

Direction of impulse conduction Dendrites Cell body Axon terminal Fig. 48. 2 a

Direction of impulse conduction Electrical impulse is sent from the axon of the transmitting

Direction of impulse conduction Electrical impulse is sent from the axon of the transmitting neuron to the dendrite of the receiving neuron

Central Nervous System (CNS) • Composed of the brain and spinal cord • Protected

Central Nervous System (CNS) • Composed of the brain and spinal cord • Protected by bone: skull and spine • Surrounded by cerebrospinal fluid (CSF): – Shock absorber (cushioning) – Transports chemicals – Removes waste produced in the brain

Spinal Cord

Spinal Cord

Anatomy of the Brain

Anatomy of the Brain

Brainstem Fig. 48. 20

Brainstem Fig. 48. 20

Brainstem Function • Data conduction – Relay information from higher brain regions • Large-scale

Brainstem Function • Data conduction – Relay information from higher brain regions • Large-scale coordination – body movement (e. g. walking)

Cerebellum “little cerebrum” Not part of the brainstem Fig. 48. 20

Cerebellum “little cerebrum” Not part of the brainstem Fig. 48. 20

Cerebellum Function • Coordination of movement and balance – Example: hand-eye coordination • Sensory

Cerebellum Function • Coordination of movement and balance – Example: hand-eye coordination • Sensory perception: – Receives sensory information about joints, muscles, sight, and sound and relays to motor pathways

Anatomy of the Brain Fig. 48. 20

Anatomy of the Brain Fig. 48. 20

Cerebrum • Most highly evolved structure of mammalian brain • Divided into 2 hemispheres

Cerebrum • Most highly evolved structure of mammalian brain • Divided into 2 hemispheres Fig. 48. 24 a

Regions of the Cerebrum Fig. 48. 24 b

Regions of the Cerebrum Fig. 48. 24 b

Primary Cortex Fig. 48. 25

Primary Cortex Fig. 48. 25

Primary Cortex • Motor cortex – sends signals to skeletal muscles • Somatosensory cortex

Primary Cortex • Motor cortex – sends signals to skeletal muscles • Somatosensory cortex – receives and integrates sensory information

Neurological Disorders • Parkinson’s Disease (PD) • Alzheimer’s Disease (AD) • Multiple Sclerosis (MS)

Neurological Disorders • Parkinson’s Disease (PD) • Alzheimer’s Disease (AD) • Multiple Sclerosis (MS)

What is Parkinson’s Disease? • A progressive degenerative disorder of the CNS • Recognized

What is Parkinson’s Disease? • A progressive degenerative disorder of the CNS • Recognized by a person’s impaired movement, speech and coordination of the body • Usually begins on one side of the brain and progresses until both sides are affected.

Cause • Certain neurons that produce dopamine die or become impaired. • Dopamine: a

Cause • Certain neurons that produce dopamine die or become impaired. • Dopamine: a chemical in the brainstem that is needed for voluntary movement, attention, learning, cognition, sleep and mood.

Symptoms • • • Tremor Muscle rigidity / Stiffness Slowness of involuntary movements Poor

Symptoms • • • Tremor Muscle rigidity / Stiffness Slowness of involuntary movements Poor balance and coordination Stooped posture

Manifestation • Age of onset: 60 years • Prevalence: 1 in every 100 persons

Manifestation • Age of onset: 60 years • Prevalence: 1 in every 100 persons over 60

Treatments • Chronic disorder with no known cure • Main goal of treatments is

Treatments • Chronic disorder with no known cure • Main goal of treatments is to control symptoms • Medications are mainly used to increase dopamine levels in the brain – Severe side effects such as hallucination, nausea, vomiting • Living a healthy lifestyle is crucial to managing PD

What is Alzheimer’s Disease? • • progressive degenerative brain disease Neurons deteriorate Brain atrophy:

What is Alzheimer’s Disease? • • progressive degenerative brain disease Neurons deteriorate Brain atrophy: lose mass A form of dementia that causes problems with memory, thinking and behaviour

Cause: Plaques and Tangles A plaque is the build up of a protein in

Cause: Plaques and Tangles A plaque is the build up of a protein in the spaces between nerve cells

Cause: Plaques and Tangles A tangle is a twisted strand of protein that build

Cause: Plaques and Tangles A tangle is a twisted strand of protein that build up on nerve cells

Cause: Plaques and Tangles • Plaques and tangles somehow play a critical role in

Cause: Plaques and Tangles • Plaques and tangles somehow play a critical role in blocking communication among nerve cells and disrupting processes that cells need to survive. • The destruction and death of nerve cells is what causes the problems / symptoms associated with AD

Brain components affected

Brain components affected

Brain components affected • Cortex: – Motor skills – Ability to control the five

Brain components affected • Cortex: – Motor skills – Ability to control the five senses – Ability to retain information & solve problems • Hippocampus – formation of new memories (amnesia)

Cortex

Cortex

Hippocampus

Hippocampus

Ventricles Due to large number of brain cell death, ventricles grow

Ventricles Due to large number of brain cell death, ventricles grow

Symptoms Difficulty forming new memories Disorientation mood and behavior changes deepening confusion about events,

Symptoms Difficulty forming new memories Disorientation mood and behavior changes deepening confusion about events, time and place • unfounded suspicions about family, friends and professional caregivers • •

Manifestation • 75% are mostly women • Early-Onset Alzheimer’s – under the age of

Manifestation • 75% are mostly women • Early-Onset Alzheimer’s – under the age of 65 – Usually mild conditions – Forgetfulness – Retains the ability to do tasks • Alzheimer’s – above the age of 65 – Early symptoms can be mistaken for old age

Treatment • Current medication can not cure AD nor stop it from progressing but

Treatment • Current medication can not cure AD nor stop it from progressing but can lessens symptoms of memory loss and confusion

What is Multiple Sclerosis? • Neurological disease affecting the CNS • non-contagious • Axons

What is Multiple Sclerosis? • Neurological disease affecting the CNS • non-contagious • Axons become demyelinated • Lost myelin can be replaced with scar tissue: – can block formation of new myelin – slows down electrical signals (transmission of AP) – Multiple = many, sclerosis = scars • Axons can become withered: – no impulse can be transmitted http: //static. howstuffworks. com/gif/multiple-sclerosis-demyelinization. gif

Cause • Idiopathic (no definite cause) • Suspected to be an autoimmune disease –

Cause • Idiopathic (no definite cause) • Suspected to be an autoimmune disease – Immune system views myelin sheath as foreign and attacks. – Myelin sheath becomes inflamed and damaged. – Occurs in small patches over the CNS • Other suspected theories – May be triggered by virus or bacteria – May be genetic although MS gene has not yet been found

Symptoms • Unpredictable, affects each • Muscular: person in different ways – stiffness /

Symptoms • Unpredictable, affects each • Muscular: person in different ways – stiffness / spasms – Different symptoms – Numbness / weakness / fatigue – Varying severities – Awkward gait / difficulty – Depends on location of damage walking – Loss of coordination – Uncontrollable tremors – Paralysis • Body functions: – Bladder & bowel problems – Difficulty with swallowing • Cognitive: – Mental health problems / – Slurred speech depression – Hearing / vision loss – Memory problems – Dizziness, headaches • Pain, seizures

Symptoms http: //upload. wikimedia. org/wikipedia/commons/archive/a/a 3/20090203184723!Symptoms_of_multiple_sclerosis. png

Symptoms http: //upload. wikimedia. org/wikipedia/commons/archive/a/a 3/20090203184723!Symptoms_of_multiple_sclerosis. png

Manifestation • Women are 2 -3 times more likely to get MS than men.

Manifestation • Women are 2 -3 times more likely to get MS than men. • Affects Caucasians more than other races.

Treatment • Treatment to reduce number of relapses / lessen severity (anti-inflammatory steroids) •

Treatment • Treatment to reduce number of relapses / lessen severity (anti-inflammatory steroids) • Medications to help manage symptoms • Rehabilitation programs • Reducing burden of symptoms: – Flu shot – Avoid stress – Avoid heat – Regular exercise, muscle-stretching exercise