Human nervous system


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Human nervous system

  2. 2. Human NERVOUS system  Nervous system controls and regulates the work of all body parts, from simple finger movement till very complex heartbeat  The nervous system contains a complex network of nerve cells, or neurons.  Neurons are specialized cells that transmit information throughout the body.
  3. 3. Structure of a neuron  Dendrites which extend from the cell body of the neuron, are the “antennae” of the neuron. Dendrites receive information from other cells.  An axon is a long membrane- covered extension of the cytoplasm that conducts nerve impulses.  Its membrane is called as myelin sheath  Bundles of axons are called nerves.
  4. 4. Neuron structure
  5. 5. Types of neurons  Neurons can be classified according to their projections and functions: a. Unipolar – sensory neuron, They transmit information from sensory organs (eyes, ears, skin, etc) to the central nervous system. b. Bipolar - interneurons are generally found in the central nervous system. Their main function is interpretation of information. c. Multipolar - motor neurons carry impulses from central nervous system to muscles or glands.
  6. 6. Neuron function  Neurons receive and transmit signals as weak electrical impulses  These signals are called as nerve impulses and they travel like wave from dendrite to axon  Na+ and K+ ions take role in carrying impulse.
  7. 7. Communication between neurons  Neurons communicate by means of synapse, where signals are transmitted from axon of one neuron to dendrite of another  Synapse is a space between neurons and there is no direct connection
  8. 8. Neurotransmitters  Impulse passes from axon of one neuron to dendrite of another by means of special neurotransmitters  Neurotransmitters diffuse across the synapse and carry impulse from a nerve cell to another.  They are released by 1st cell axon end and received by 2nd cell dendrite  Examples: adrenaline, histamine, acetylcholine etc.
  9. 9. Parts of human nervous system  Human nervous system includes 2 parts: a. Central Nervous System (CNS): includes brain and spinal cord, control center of body b. Peripheral nervous system (PNS): contains sensory neurons, receive information (eye, skin, ear …) and transmit it to CNS; and motor neurons which send commands from CNS to muscles and organs
  10. 10. CNS: brain  Brain, body’s main processing and controlling center which is protected by skull and includes about 100 billion neurons  All body activities, emotions, thought, memories are controlled by brain  Its size in males about 1200-1350 grams and in females 1000-1250 grams
  11. 11.  The brain consists of three main parts: 1. Forebrain 2. Midbrain 3. Hindbrain
  12. 12. BRAIN: 1. Forebrain (передний мозг)  Largest portion of brain, composed of 2 main parts: a. Cerebrum (конечный мозг)  Upper covering part, has many folds, divided into 2 hemispheres  Responsible for thought, skeletal muscles movement, skin feel, vision, hearing and smell and etc. b. Diencephalon (промежуточный мозг)  Regulates body temperature, responsible for anger, pain, pleasure, hunger, thirst, also maintains homeostasis and etc.
  13. 13. BRAIN: 2. Midbrain  Coordinates head and eye movement, eye focus, helps for hearing
  14. 14. BRAIN: 3. Hindbrain (задний мозг)  Composed of medulla oblongata (продолговатый мозг), cerebellum (мозжечок) and pons (мост)
  15. 15. a. Medulla oblongata:  Located in the border of spinal cord and brain  Regulates respiratory, circulatory and excretory activities, swallowing, sneezing, vomiting and etc. b. Cerebellum:  Located in posterior end of brain  Regulates balance, posture and movement c. Pons:  Bridge-like structure  Controls certain respiratory functions
  16. 16. CNS: spinal cord  Spinal cord is a dense cable coming out from brain and protected by vertebral column  Spinal cord transmits signals from brain and to brain and functions in reflexes  A reflex is a sudden, involuntary contraction of muscles in response to a stimulus.  Spinal cord contains a core of grey matter covered by white matter, grey matter mainly neuron bodies and interneurons, white matter axons
  17. 17. Peripheral nervous system PNS  PNS connects CNS to the rest of the body  From brain 12 pair of nerves projected, from spinal cord 31 pairs that go to all body parts Body is controlled by 2 ways of PNS: a. Somatic nervous system (soma means body) b. Autonomic nervous system
  18. 18. 1. Somatic nervous system  Most motor neurons that stimulate skeletal muscles are UNDER OUR CONSCIOUS CONTROL, like running, writing, swimming …  They coordinate the voluntary action of our body  Some activity such as reflexes are involuntary, because they are to protect our body and very fast
  19. 19. 2. Autonomic nervous system  Motor neurons that regulate smooth muscles and NOT UNDER OUR CONSCIOUS CONTROL, like heartbeat, peristalsis, blood vessels contraction …  They action involuntarily  It is divided to PARASYMPATHETIC and SYMPATHETIC nervous systems which maintain stability in our body
  20. 20.  The effects of parasympathetic and sympathetic nervous system are opposite.  Generally sympathetic system helps the body deal with emergency situations by accelerating some body activities.  Parasympathetic system promotes normal relaxed body functioning.