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  • Main Idea(s) of This Slide - This slide depicts the synapses between the axon of one neuron and the dendrite of another. Here is a close-up view of the synapse between two adjacent neurons. The axon of the neuron at the top of the slide terminates in what is called an axon bulb. Inside the axon bulb are synaptic vesicles that contain neurotransmitters. The neurotransmitters are responsible for exiting the axon bulb and entering into the synapse. Once inside the synapse (space between the neurons), the neurohormones bind to the adjacent neurons “postsynaptic membrane” and cause a new depolarization wave to begin. This image on the right depicts the neurotransmitter (neurohormone) being released from the synaptic vesicle into the synapse where it can then bind to receptors on the adjacent neuron.
  • Main Idea(s) of This Slide - There are over 50 known neurotransmitters today. This slide lists three commonly discussed neurotransmitters; acetylcholine, dopamine, and serotonin. Acetylcholine is the neurotransmitter that is responsible for carrying a nerve impulse from a motor neuron, across a synapse, to a muscle cell (the effector) and causing the muscle to respond by contracting. Insufficient levels of acetylcholine or disruption in it ’s ability to work can cause neuromuscular problems. Seratonin is a neurotransmitter that is responsible for “filtering” sensory information coming into the brain. Some recreational drugs such as ecstasy create imbalances in the levels of serotonin resulting in hallucinations and mood changes. Other drugs called SSRI’s (selective serotonin re-uptake inhibitors) elevate serotonin levels in the brain resulting in mood elevation and are prescribed as anti-depressants. Dopamine is considered the “master molecule” of addiction. It is a neurotransmitter that is released by brain cells that causes a feeling of “well being” in response to pleasurable activities such as sex and eating. Elevated levels of dopamine cause a euphoric high and are associated with many recreational drugs.
  • Main Idea(s) of This Slide - Neurotransmitters must be cleaned-up from the synapse to ensure that the response to them is short-lived and precise. Most neurotransmitters have enzymes which either break them down or cause them to be taken back into the neuron that released them. Acetylcholine, for example, the neurotransmitter that causes muscle contraction is broken down by an enzyme called acetylcholinesterase. The presence of this enzyme ensures that when a neuron stimulates a muscle cell, the stimulus only lasts a second which allows the muscle to then relax immediately after it was stimulated. This allows precise, coordinated movements. Other neurotransmitters have enzymes of their own that regulate their levels in the synaptic spaces.
  • Main Idea(s) of This Slide - Again, use this opportunity to generate discussion in order to see if students are comprehending the impact that dopamine has on the central nervous system.
  • Main Idea(s) of This Slide - Dopamine is believed to be the primary neurotransmitter responsible for chemical dependency based upon it ’s ability to reward behaviors with pleasurable feelings.
  • Main Idea(s) of This Slide - Some recreational drugs interfere with the ability of the brain to regulate dopamine levels. Cocaine blocks the reabsorption of dopamine back into the neuron that released it. This results in a build-up of dopamine causing a prolonged sense of euphoria. Amphetamines stimulate excessive release of dopamine which overwhelms the ability of the neurons to reabsorb it quickly or MAO to break it down. The net result, again, is an elevated level of dopamine and a “high” feeling. Nicotine stimulates excessive release of dopamine and blocks the ability of MAO to break it down. This leaves the neurons ability to reabsorb the dopamine as the only way to return levels to normal. Again, this results in a short term “high”.
  • Main Idea(s) of This Slide - Because these drugs elevate the levels of dopamine, they result in increased feelings of pleasure. This reinforces the behavior of taking the drug. In response to continued elevated dopamine levels, the brain begins to reduce the number of dopamine receptors on it ’s neurons (this is a kind of negative feedback mechanism where the brain is trying to keep things in balance). As a result of decreased numbers of dopamine receptors, the drug addict must take more and more of the drug and more often in order to maintain the same “high” feeling. This process continues, with number of receptors decreasing to the point that eventually, the drug addict must take high levels of the drug just to feel “O.K.” (in order to not feel bad).
  • The 29 year old man was injured in a car accident. He was showing no signs of conciousness. The doctors were convinced he was in a vegetative stage, until now. To answer yes, he was told to think of playing tennis, a motor activity. To answer no, he was told to think of wandering from room to room in his home, visualising everything he would expect to see there, creating activity in the part of the brain governing spatial awareness. His doctors were amazed when the patient gave the correct answers to a series of questions about his family. The ­experiment will fuel the controversy of when a patient should have life support removed.

Chapter 17 Chapter 17 Presentation Transcript

  • CHAPTER 17 Nervous System
  • Nervous System
      • The nervous system
        • Forms a communication and coordination network throughout an animal ’s body.
      • Neurons
        • Are nerve cells specialized for carrying electrical signals from one part of the body to another.
  • Organization of Nervous Systems
    • The nervous systems of most animals have 2 main divisions:
      • The central nervous system (CNS)
        • Consists of the brain and, in vertebrates , the spinal cord .
      • The peripheral nervous system (PNS)
        • Is made up mostly of nerves that carry signals into and out of the CNS .
    A nerve is a communication line made from cable-like bundles of neuron fibers .
  • Central Nervous System Brain Spinal Cord Peripheral Nervous System Peripheral Nerve
  • The 3 interconnected functions of the nervous system are carried out by 3 types of neurons:
    • Sensory neurons
      • Convey sensory input.
    • Interneurons
      • Perform integration, the interpretation of the sensory signals.
    • Motor neurons
      • Carry out motor input.
  • You hit the ball
  • Why are athletes so good at what they are doing? Researchers found that the brain of athletes is “quieter” than non-athletes when asked to perform a task. This suggests that their brain would be more efficient , and need less neurons to perform a task. Some neurons strenghten their connections to other neurons and weakens connections to others. (ex: soccer players and screen) Practice also changes the brain Athletes can analyze a situation and make a decision in a split second.
  • NEURONS The Functional units of the Nervous System
  • Neurons
    • Vary widely in shape but share some common features:
    • The cell body houses the nucleus and other organelles.
    • 2 types of extensions project from the cell body:
      • DENTRITES receive incoming messages from other cells and convey the information toward the cell body.
      • The AXON conducts signals toward another neuron or an effector.
  • 5 AXON : Transmits the action potential. 2 DENDRITES: Receive signals from other neurons. 4 Action potential starts here. 1 Synaptic terminals: Bring signals from other neurons. 3 CELL BODY Integrates signals; coordinates metabolic activities. 6 Myelin: Insulates axon, speeds conduction. 8 DENDRITES (of other neurons) 7 Synaptic terminals: Transmit signals to other neurons.
  • How Do Neurons Communicate?
    • Action Potential
    • Synapses
    • Neurotransmitters
  • Neuron 1 Neuron 2 1. Action Potential 2. Synapse 3. Neurotransmitters 4. Action Potential
  • 1. The Action Potential
  • How Is Neural Activity Produced and Transmitted?
    • Neurons Create Electrical Signals Across Their Membranes
    • A resting neuron contains potential energy that resides in an electrical charge difference across its plasma membrane.
    • The voltage (potential difference) is called the resting potential .
  • The Action Potential
    • a STIMULUS is any factor that causes a nerve signal to be generated.
    • Action potential is the technical name for a nerve signal.
  •  
  • Propagation
    • An action potential is a localized electrical event.
    • To function as a nerve signal, this local event must be passed along the neuron.
    • Action potential propagation is like a “domino effect” along a neuron.
  •  
  • 2. SYNAPSES
  • Neurons Communicate at Synapses Synapses a re the relay points between 2 neurons or between a neuron and an effector cell
  • Based on Harvard Medical School Family Health Guide SYNAPSES Synapses rely on neurotransmitters to carry information from one nerve cell to another kind of cell that will react.
  • So, how is the message carried from one neuron to the other? Or What happens in the Synapse?
  • Synaptic cleft Neuron 2 Neuron 1 Synapse Vesicles containing neurotransmitters Receptors The neurotransmitters binds there
  • Synaptic cleft
    • Action potential arrives
    • Vesicles containing the neurotransmitter fuses with membrane
  • 3. Neurotransmitter released into the synaptic cleft
  • 4. Neurotransmitter binds to the receptor and opens up the ion Channel
  • a new action potential starts Na + 5. Na+ enters ,
  • A neuron may receive input from hundreds of other neurons via thousands of synaptic terminals.
  • 3. Neurotransmitters
  • 50 Known Neurotransmitters
    • Examples include:
      • Acetylcholine
      • Dopamine
      • Serotonin
      • Endorphins
  • Example of Neurotransmitter DOPAMINE
  • DOPAMINE
    • Human behavior is controlled by natural chemical reward systems in the body
    • For example , we like to eat fatty foods because it make us feel good
    • It is the release of DOPAMINE that is the chemical reward system responsible for the good feeling
    • Dopamine “reinforces behaviors essential to our survival.”
    • After neurotransmitter stimulates the postsynaptic membrane, it is removed by an enzyme or transported out of synapse.
      • REMOVAL prevents repeated stimulation of postsynaptic membrane
    • For example, acetylcholine is removed from synapses by an enzyme called acetylcholinesterase
    Synapses must be cleaned up
    • Mood, pleasure, pain , and other mental states are determined by particular groups of neurons in the brain that use special sets of neurotransmitters and neuromodulators.
    • Mood , for example, is strongly influenced by the neurotransmitter serotonin .
      • Many researchers think that depression results from a shortage of serotonin.
      • Prozac , inhibits the reabsorption of serotonin, thus increasing the amount in the synapse
  • HOW DRUG ADDICTION WORKS?
    • Many drugs affect the nervous system by interfering with or potentiating neurotransmitters:
      • Can enhance or block their release
      • Can interfere with removal from synaptic cleft
    DRUG ADDICTION
    • These drugs include:
        • caffeine,
        • nicotine,
        • alcohol,
        • cocaine,
        • LSD,
        • marijuana,
        • various prescription drugs,
        • Etc………………
    • Drug Actions at a Synapse
      • Cause the release of a neurotransmitter (NT) from a synaptic vesicle into the axon terminal
      • Prevent the release of a NT
      • Promote the release of a NT
      • Prevent the reuptake of a NT
      • Block enzymatic breakdown of a NT
      • Mimic the action of a NT by binding to a receptor
    Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. enzyme Axon terminal neurotransmitter synaptic vesicle Synaptic cleft Postsynaptic neuron 2 1 3 6 4 5 receptor
  • According to scientists: DOPAMINE . It is thought to be the master molecule of addiction.
    • what is the master molecule of addiction?
    • where is it produced?
  • It is made in the brain and affects primitive parts of the brain Based on Time , May 5, 1997
    • After being released into the synapse, dopamine binds to receptors on the next neuron
    • Dopamine is then reabsorbed by the Synapse
    • Dopamine is reabsorbed by the Synapse
    MAO
    • It can be stored in the vesicle or broken down by an enzyme called M ono A mine O xidase ( MAO )
    • Cocaine blocks the normal absorption of dopamine.
    • Dopamine accumulates in the synapse
    • It keeps stimulating the receiver cell.
    • Amphetamines stimulate excess release of dopamine
    • Overwhelm the processes of reuptake and enzyme breakdown.
    Nicotine stimulates the release of dopamine, while another substance in cigarette smoke blocks the action of MAO. How Drug Affect Dopamine Levels Based on Time , May 5, 1997
  • When a cell has been exposed to a chemical signal for a long time, it tends to get used to it and looses its sensibility to the stimulus. (ex: sitting on a chair). Drug Addiction: If a cell is exposed to high levels of neurotransmitter, it will adapt by having less receptors (homeostasis)
  • Physiology of Addiction
    • Drug  amount of dopamine in the synapses
    • Increased dopamine results in  feelings of pleasure
    • Nervous system responds by  the number of dopamine receptor sites.
        • When a cell has been exposed to a chemical signal for a long time, it tends to get used to it and looses its sensibility to the stimulus (ex: sitting on a chair). Homeostasis
    • Addict must take more drug to produce the same “high”
    • “ So while addicts begin by taking drugs to feel high, they end up taking them in order not to feel low.”
  • Do you know a good addiction?
    • Exercise, such as cardiovascular exercise, releases a neurotransmitter called Endorphins (as well as serotonin, dopamine)
    • Endorphins function as the body natural pain killer.
    • Exercise correlates with good mental health as people age
    Runner’s high
  • The Human Nervous System
    • Consists of:
    • the central nervous system (CNS)
    • a peripheral nervous system (PNS).
  • The Central Nervous System: CNS is made up of the spinal cord and the brain
    • The spinal cord acts as the central communication conduit between the brain and the rest of the body.
    • The brain is the master control center of the nervous system.
  • The Central Nervous System
    • The Spinal Cord
      • Extends from base of brain into vertebral canal
      • Protected by vertebrae
    Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. spinal cord spinal nerve vertebra Intervertebral disk
    • Functions of Spinal Cord
      • Communication between brain and body
      • Center for many reflex arcs
        • Sensory receptors generate an action potential
        • Sensory neurons transmit impulse to the spinal cord
        • Sensory neurons synapse with interneurons in the spinal cord
        • Interneurons synapse with motor neurons
        • Motor neurons carry impulse to effectors
        • Brain not involved, when your hand touch a hot oven, you don ’t have the time to think about removing your hand or not!
  • A Somatic Reflex Arc Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. pin Dorsal sensory receptor (in skin) cell body of sensory neuron cell body of interneuron axon of motor neuron cell body of motor neuron effector (muscle) Ventral side Dorsal side
  • The Human Brain
    • 4 major areas:
      • The Cerebrum
      • The Diencephalon
      • The Cerebellum
      • The Brain Stem
  • Cerebrum
  • Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. skull meninges Diencephalon pons spinal cord Cerebellum fourth ventricle pineal gland hypothalamus thalamus (surrounds the third ventricle) third ventricle lateral ventricle Cerebrum corpus callosum pituitary gland Brain stem midbrain medulla oblongata a. Parts of brain
  • 1. The Cerebrum
  • The cerebrum is involved in several functions of the body including:
    • Intelligence
    • Personality
    • Thinking
    • Perceiving
    • Producing and Understanding Language
    • Interpretation of Sensory Impulses
    • Motor Function
    • Planning and Organization
    • Touch Sensation
  • THE CEREBRUM largest portion of human brain
    • 2 cerebral hemispheres
      • Divided by longitudinal fissure but connected by the corpus callosum
      • Covered by a convoluted layer of gray matter:
        • gray matter contains neuronal bodies
        • white matter contains mainly axons
    • The cerebral cortex is the region that accounts for sensation , voluntary movement , and conscious thought (itch) “ An infestation that begins in the mind” Morgellon’s Disease LA Times May 17, 2011
  • Gray Matter White Matter
        • UCLA researchers found that meditation increases gray matter
  • Cerebrum
    • Primary Motor Area
      • All voluntary motor movements originate here
        • Each body part is controlled by a specific section
    • Primary Somatosensory Area
      • Receives sensory information from skin and skeletal muscles
      • Primary areas for vision, hearing, taste, and smell
    • Association Areas
      • Integration of function (walking and talking)
      • http://www.latimes.com/health/boostershots/la-heb-foreign-accent-20110505,0,7374634.story?track=rss&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+latimes%2Fmostviewed+%28L.A.+Times+-+Most+Viewed+Stories%29
  • Size of the body part reflects the amount of cerebral cortex devoted to that body part Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Toes Ankle Knee Hip Trunk Shoulder A r m Ring finger Index finger Thumb Neck Eyelid and eyeball Lips and jaw Face Tongue Genitals Hip Trunk Neck Shoulder Little finger Ring finger Middle finger Index finger Face Lips, teeth, gums, and jaw Tongue Pharynx a. Prima ry motor area b . Primary somatosensory area Intra-abdominal Nose Eye Thump Leg Foot Toes Elbow Arm Forearm wrist Hand Pharynx Middle finger Little finger Hand Wrist Foreman Elbow
    • Processing Centers
      • Receive information from the other association areas and perform higher-level analytical functions
      • Wernicke ’s Area - Understanding of written and spoken words
      • Broca ’s Area - Directs motor actions for speech
    • Central White Matter
      • Composes most of cerebrum deep to cortex
      • Composed of tracts of axons that take information between different sensory, motor, and association areas
    • Basal Nuclei
      • Masses of gray matter deep within cerebrum
      • Integrate motor commands
    Cerebrum
  • Language and Speech Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. motor speech (Broca ’ s area) Ability to speech primary motor area primary visual area primary auditory area sensory speech (Wernicke ’ s area) Ability to comprehend speech Example : writer who, one morning, couldn ’t read/recognizes words anymore, but it could write flawlessly.
  • 2. The diencephalon
  • DIENCEPHALON
  • Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Diencephalon hypothalamus thalamus pituitary gland
    • homeostatic control center
      • Body temperature, water balance, hunger and thirst, sleep
      • manufactures hormones and controls the pituitary gland (Link between nervous and endocrine system)
    • sensory relay center
    • Receives incoming information and sends it to appropriate area
    • Memory, emotional responses
  • 3. The cerebellum
  • CEREBELLUM
  • The Cerebellum
    • Receives both sensory and motor input
    • Integrates information and sends impulses to skeletal muscle s by way of the brain stem
    • Can compare actual movements with intended movements
    • Functions to assure smooth, coordinated motor movements
  • 4. The Brain Stem The most ancient, sometimes called the Reptilian Brain
  • BRAIN STEM
  • The Brain Stem
    • Midbrain
      • Relay center for tracts passing between cerebrum and cerebellum
    • Medulla oblongata
      • Control center for heartbeat, breathing, blood pressure, swallowing, coughing, vomiting
    • Pons (bridge)
      • Contains bundles of axons traveling between the cerebellum and the rest of the CNS
  • DISORDERS OF THE BRAIN
    • a bit of history
    • New experiment on brain damaged patient
    • Alzheimer’s Disease
    • Parkinson’s Disease
    • Multiple Sclerosis
    • Stroke
    • Meningitis
    • Mad Cow Disease
  • 1. The case of Phineas Gage
  • Phineas Gage was the 1st patient from whom we learned about the link between personality and decision making and the function of the front parts of the brain (frontal lobes) . In 1848, a 3 foot steel rod was blown through his head by an explosion. He survived but his personality changed. He became rude, impatient, fitful. He died at 37 after experiencing severe seizures.
  • 2. Recent findings More recently, doctors were able to communicate with a brain-injured patient. They could read is thoughts using a scanner.
  • 3. Alzheimer Disease (AD)
      • Most common cause of dementia
      • Signs may appear before 50, usually seen in people past 65
      • Loss of memory (of recent events) is an early symptom
      • Abnormal neurons especially in the hippocampus and amygdala
        • Plaques : abnormal clusters of protein fragments, build up between nerve cells.
        • Neurofibrillary tangles found in dead or dying neurons
      • Several genes have been identified that predispose a person to AD
      • No prevention or cure
  • Alzheimer Disease Presence of plaques in different regions of the brain from an Alzheimer patient.
      • Gradual loss of motor control
        • Typically begins between 50 and 60 years of age
      • Later characteristics include tremors and
      • muscle rigidity, speaking may be difficult
      • Caused by a degeneration of dopamine producing neurons in basal nuclei
      • Dopamine (as a drug) cannot be administered because it cannot cross the blood-brain barrier
      • L-dopa is a drug that the body can convert to dopamine, at least for a while
      • Pesticide exposure found to increase risk of Parkinson's disease (UCLA research)
    4. Parkinson Disease (PD)
      • Most common neurological disease that afflicts young adults
      • Affects the myelin sheath of white matter in the brain
      • Autoimmune disease
    5. Multiple Sclerosis (MS)
      • Symptoms include: Fatigue, limb weakness, vision problems, tingling or numbness
      • MS can take several forms (mild to severe)
      • No treatment is available, but the progression can be slowed
      • A disruption to the blood supply in the brain
      • Symptoms depend on the amount and area of the brain tissue that is affected
      • Factors such as age and race influence the likelihood of having a stroke
    6. Stroke
      • An infection of the meninges that surround the brain and spinal cord
      • Caused by bacteria or viruses
      • Infection may spread into the brain tissue
      • A diagnoses is usually confirmed by sampling cerebrospinal fluid
      • A vaccine is available for protection against some types of the disease
    7. Meningitis
      • Caused by Prions (infectious proteins)
      • Replicate and accumulate in brain tissue
      • No treatment available
      • Fatal
    8. Mad Cow Disease
  • The Peripheral Nervous System The vertebrate peripheral nervous system is divided into 2 components:
    • 1. The somatic nervous system
      • Carries signals to and from skeletal muscles , mainly in response to external stimuli. Serves skin
      • Voluntary as unvoluntary movements
    • 2. The autonomic nervous system
      • Regulates the internal environment by controlling smooth and cardiac muscles and the organs and glands of the digestive, cardiovascular, excretory, and endocrine systems.
      • 2 divisions:
    • The parasympathetic division primes the body for digesting food and resting.
    • The sympathetic division prepares the body for intense, energy-consuming activities “Flight or fight”
  •  
  • Disorders of the Spinal Cord
    • Spinal cord injuries may stop impulses from traveling along neurons in the spinal cord.
      • This can result in paralysis of the areas located below the site of injury
    • Amyotrophic Lateral Sclerosis (ALS)
      • Also called Lou Gehrig ’s disease
      • Steven Hawking has ALS
      • Affects the motor nerves of the spinal cord
      • Incurable, people usually die within five years of diagnosis
      • There may be multiple causes of nerve cell death
  • Disorders of the Peripheral Nerves
    • Guillain-Barre Syndrome (GBS)
      • Demyelination of peripheral nerve axons
      • Hypothesized to result from abnormal immune reactions to one of several types of infections
      • Muscle weakness begins in the lower limbs then ascends to the upper limbs
      • Patients usually recover within a year