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Nervous System

Explore the workings of the nervous system, from detecting stimuli to motor responses. Learn about the central and peripheral nervous systems, neuron function, sensory receptors, and motor cells. Discover the anatomy of a neuron, nerve circuits, and neurological disorders like Parkinson's and Alzheimer's disease.

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Nervous System

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  1. Nervous System PNS & CNS Neuron Conduction Disease

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

  3. 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

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

  5. Components of the Nerve Circuit

  6. 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”

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

  8. 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

  9. Peripheral Nervous System Sensory Division Motor Division Sensory receptors Effector cells External Sensing Internal Sensing Voluntary System Involuntary System Organization of the PNS Fig. 48.17

  10. 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

  11. Sensory Receptors • Detect a specific type of stimulus

  12. Peripheral Nervous System Sensory Division Motor Division Sensory receptors Effector cells External Sensing Internal Sensing Voluntary System Involuntary System Organization of the PNS Fig. 48.17

  13. 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 smoothmuscle, cardiacmuscle and organs of the body • Voluntary system: responds to stimuli by sending signals to skeletalmuscles

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

  15. 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

  16. Components of a neuron Fig. 48.2a,c

  17. Components of a neuron

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

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

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

  21. Direction of impulse conduction Dendrites Cell body Axon Axon terminal Fig. 48.2a

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

  23. 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

  24. Spinal Cord

  25. Anatomy of the Brain

  26. Brainstem Fig. 48.20

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

  28. “little cerebrum” Cerebellum Not part of the brainstem Fig. 48.20

  29. 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

  30. Anatomy of the Brain Fig. 48.20

  31. Cerebrum • Most highly evolved structure of mammalian brain • Divided into 2 hemispheres Fig. 48.24a

  32. Regions of the Cerebrum Fig. 48.24b

  33. Primary Cortex Fig. 48.25

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

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

  36. 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.

  37. 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.

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

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

  40. 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

  41. 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

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

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

  44. 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

  45. Brain components affected

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

  47. Cortex

  48. Hippocampus

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

  50. 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

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