Human nervous system

1. HUMAN NERVOUS SYSTEM

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. 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. Neuron structure

5. Types of neurons Neurons can be classified according to their projections and functions: Unipolar – sensory neuron , They transmit information from sensory organs (eyes, ears, skin, etc) to the central nervous system. Bipolar - interneurons are generally found in the central nervous system. Their main function is interpretation of information. Multipolar - motor neurons carry impulses from central nervous system to muscles or glands.

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. 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. 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 1 st cell axon end and received by 2 nd cell dendrite Examples: adrenaline, histamine, acetylcholine etc.

9. Parts of human nervous system Human nervous system includes 2 parts: Central Nervous System (CNS): includes brain and spinal cord, control center of body 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. 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. The brain consists of three main parts: Forebrain Midbrain Hindbrain

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. BRAIN: 2. Midbrain Coordinates head and eye movement , eye focus , helps for hearing

14. BRAIN: 3. Hindbrain ( задний мозг ) Composed of medulla oblongata ( продолговатый мозг ), cerebellum (мозжечок) and pons (мост)

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. 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. 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: Somatic nervous system ( soma means body) Autonomic nervous system

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. 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. 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.