general organization of nervous system -

n biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes that impact the body, then works in tandem with the endocrine system to respond to such events. Nervous tissue first arose in wormlike organisms about 550 to 600 .
BiologyBiology ArticleNervous System
Top Banner
Human Nervous System
Living organisms adapt to their moves and positions in response to the environmental changes for their protection or to their advantage. When an entity reacts to the changes in its surroundings, it is referred to as stimulus while the reaction to the stimulus is referred to as a response. Common stimuli are sound, light, air, heat, smell, taste, water and gravity.

Think of burning your finger of fracturing your bone without any pain sensation. It may certainly sound like a superpower or an ideal situation, however, when it comes to the standpoint of survival, it can be disastrous.

The characteristic behaviour of living entities is to respond to stimuli with the intervention of the nervous system. It is an organ system ascribed to send signals from the spinal cord and the brain throughout the body and then back from all the body parts to the brain. The neuron acts as the mediator and is the basic signalling unit of the nervous system.

Pain is the body’s way of letting us know that something is not right. It can prevent further injuries or push us to seek medical attention. Moreover, all of this is possible because humans can respond and react to stimuli due to control and coordination among the various organs and organ systems.

Control and Coordination in simple multicellular organisms take place through only the Nervous system which coordinates activities of our body. It is the control system for all our actions, thinking, and behaviour.

he nervous system or the neural system is a complex network of neurons specialized to carry messages. The complexity of the nervous system increases as we move towards higher animals.

For instance, cnidarians such as jellyfish have relatively simple nerve nets spread throughout their body. Crabs have a more complicated nervous system in the form of 2 nerve centers called dorsal ganglion and ventral ganglion.

As we move further up the ladder, higher organisms such as vertebrates have a developed brain. Moreover, it is one of the most complicated structures in the animal kingdom, containing billions of neurons, all intricately connected.

In the human body, the neural system integrates the activities of organs based on the stimuli, which the neurons detect and transmit. They transmit messages in the form of electrical impulses and convey messages to and from the sense organs. Thus, the nervous coordination involves the participation of the sense organs, nerves, spinal cord, and brain.Central Nervous System
Central Nervous System (CNS) is often cal

1. The Nervous System

2. Master controlling and communicating system in the body It controls and coordinates all essential functions of the body Every thought, action and emotion reflects its activity. It signals the body through electrical impulses that communicate with the body cells. Its signaling and responding abilities are highly specific and rapid

3. NEURAL ORGANISATION

4. Structural classification of the Nervous System Central Nervous System (CNS) Made up of brain and spinal cord Acts as body’s control center, coordinates body’s activities Impulses travel through the neurons in your body to reac h the brain Central Nervous System is yellow in this diagram.

5. Peripheral Nervous System(PNS) Made up of all the nerves that carry messages to and from the central nervous system. Similar to telephone wires that connect all of our houses in the community Central Nervous System and Peripheral Nervous System work together to make rapid changes in your body in response to stimuli. Peripheral Nervous System is green in this diagram .

6. PNS can be subdivided into 2 divisions: (1) Autonomic Nervous System -Relay information from central nervous system to organs -Cranial & spinal nerves connecting CNS to heart, stomach, intestines, glands -Controls unconscious activities It can be subdivided into 2 divisions: Parasympathetic (Relaxation response) Decreases heart rate, bronchiole dilation, blood glucose, blood to skeletal muscle Increases digestion, pupil size, urinary output “rest and digest”

7. Sympathetic (Stress Response) Decreases digestion, pupil size, urinary output Increases heart rate, bronchiole dilation, blood glucose, blood to skeletal muscle “fight or flight” (2) Somatic Nervous System Cranial & spinal nerves connecting CNS to skin & skeletal muscles Oversees conscious activities

8. THE NEURON The basic unit of structure and function in the nervous system Cells that conduct impulses. Made up of dendrites, cell body and an axon

9. Dendrites: branch-like extensions that receive impulses and carry them toward cell body. Cell body: The part of a neuron that encloses the nucleus and other organelles necessary to maintain and repair the neuron. Cytoplasm consist of nissl’s granules rich in RNA and concerned with protein synthesis. Axon: single extension of the neuron that carries impulses away from the cell body. Larger axons are enclosed by sheaths of myelin produced by Schwann cells. Myelin sheath increases the speed of impulse transmission along the axon.

10. Narrow gaps in the myelin sheath between Schwann cells are called nodes of Ranvier Neurons do not touch; there is a gap between them called a synapse Messages are sent across the synapses by special chemicals called neurotransmitters

11. Structural & functional classification of neuron

12. Neuron Communication Nerve cells convert electrical signal (action potential) to a chemical signal (neurotransmitter (NT) molecules). Dozens of neurotransmitters have been identified, with different functions .

13. NTs are released by one nerve cell and bind to receptors on the post-synaptic membrane of the next nerve cell. The chemical signal is then converted back into an electrical signal.

14. the signal is transmitted to another neurone across a junction called a synapse by chemicals called neurotransmitters . Smarter UK cell body axon myelin sheath dendrites nerve endings nucleus synapse signals cross between neurons at the synapse neurotransmitter vesicle synaptic cleft receptor electrical impulse triggers vesicles to move to the synapse membrane 1 vesicles fuse with the membrane and release neurotransmitter into the synaptic cleft 2 neurotransmitter diffuses across the cleft and binds to receptors on the other side 3 Once enough receptors have neurotransmitters bound to them, the signal is transmitted… 4

15. Types of neuron Sensory Neuron : responsible for receiving stimuli from the external environment and converting it to an impulse that it sends towards the brain via more sensory neuron Interneuron: found within brain and spinal cord, process incoming impulses and pass them on to motor neurons. Motor neuron: sends the impulse away from the CNS toward the muscle or nerve that will respond to the stimulus

16. Central Nervous System(CNS) Consists of brain and spine Functions: Receives sensory signals and determines appropriate response Stores memory Carries out thought

17. BRAIN The brain is the largest, most complex portion of the nervous system, containing 100 billion multipolar neurons. The brain can be divided into cerebrum (largest portion and associated with higher mental functions) diencephalon (processes sensory input) cerebellum (coordinates muscular activity) brainstem ( coordinates and regulate visceral activities).

18. Cerebrum

19. Largest part of the brain Consists of right and left hemisphere connected by the corpus callosum Each cerebral hemisphere is composed of different lobes -Frontal -Temporal -Parietal -Occipital Embedded in the cerebrum is the basal ganglia

20. Lobes of the Cerebrum Frontal Lobe : Influences the personality of the person and also responsible for judgment ,abstract reasoning, social behavior, language expression and motor movement Temporal lobe : It controls the hearing, language comprehension, storage and recall of memories. Limbic system is deeply located in the temporal lobe. This controls the basic drives such as hunger,anger,emotion and sexual drive Parietal lobe : principal center for the reception and interpretation of sensation and it interprets and integrates the sensory inputs like touch, temperature and pain

21. d)Occipital lobe : This function mainly to interpret visual stimuli Cerebral Cortex

22. Functional Regions of the Cerebral Cortex a. The functional areas of the brain overlap, but the cortex can generally be divided into motor, sensory, and association areas. b.The primary motor areas lie in the frontal lobes, anterior to the central sulcus and in its anterior wall. c. Broca’s area , anterior to the primary motor cortex, coordinates muscular activity to make speech possible. Above Broca’s area is the frontal eye field that controls the voluntary movements of the eyes and eyelids.

23. e.The sensory areas are located in several areas of the cerebrum and interpret sensory input, producing feelings or sensations.eg,olfaction in the frontal lobe,cutaneus sensation in parietal lobe, visual sensation in occipital lobe i. Association areas of the frontal lobe control a number of higher intellectual processes. j. A general interpretive area is found at the junction of the parietal, temporal, and occipital lobes, and plays the primary role in complex thought processing.

24. Language Figure 9-23: Cerebral processing of spoken and visual language Primary areas of cortical specialization for language Broca’s area g overns speaking ability Wernicke’s area Concerned with language comprehension Responsible for formulating coherent patterns of speech

25. Cerebral Cortex Schematic Linking of Various Regions of the Cortex