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HUMAN NERVOUS SYSTEM
Human nervous system is a typical centralized nervous system
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DIVISIONS OF HUMAN NERVOUS SYSTEM:
Human nervous system is primarily divided into central nervous system(CNS) and peripheral
nervous system (PNS) CNS acts as a coordinating center while PNS provides communication
among receptors, CNS, and effectors
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Main division of nervous system

1
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Brain
Cerebrum: The cerebrum, divided into two hemispheres, is the largest and most evolved part of
the human brain
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Different regions of the cerebral

cortex specialize in specific functions
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Cerebellum: Situated below the cerebrum, the cerebellum coordinates voluntary movements,
balance, and posture
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It receives input from the sensory systems and the
cerebral cortex, allowing for smooth and coordinated movements
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Brainstem: The brainstem is located at the base of the brain and connects the cerebrum with
the spinal cord
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The brainstem regulates
essential functions such as breathing, heart rate, blood pressure, and consciousness
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Damage to the brainstem can be life-threatening due to its critical role in controlling vital
functions
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Spinal Cord
The spinal cord is a long, cylindrical bundle of nerve fibers that extends from the base of the
brain to the lumbar region of the vertebral column
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The spinal cord is protected by the vertebrae of the spinal column and surrounded by
cerebrospinal fluid, which cushions and nourishes the delicate nerve tissue
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For example, the withdrawal reflex involves the
quick withdrawal of a body part from a painful stimulus, such as touching a hot object
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Peripheral Nervous System (PNS)

a
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It consists of
sensory neurons that transmit information from sensory receptors in the skin, muscles, and joints
to the CNS, as well as motor neurons that convey signals from the CNS to skeletal muscles,
enabling voluntary movements
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b
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It operates autonomously, without conscious
control, and is divided into two branches:
Sympathetic Nervous System (SNS): The sympathetic nervous system activates the body's
fight-or-flight response in response to stress or danger
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The release of adrenaline and noradrenaline from the adrenal glands amplifies the
body's physiological response to stressors
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It
conserves energy, lowers heart rate and blood pressure, stimulates digestion, and enhances
immune function
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3
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They consist of a cell body (soma), dendrites, and an axon
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Neurons communicate with one another through
synapses, specialized junctions where neurotransmitters are released from the presynaptic neuron
and received by the postsynaptic neuron
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They outnumber neurons in
the nervous system and perform various functions, including:





Astrocytes: Astrocytes regulate the chemical environment around neurons, maintain the bloodbrain barrier, and provide nutrients and structural support
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Microglia: Microglia act as the immune cells of the nervous system, monitoring for pathogens
and cellular debris and removing them through phagocytosis
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Neuron and glial cells

4
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Sensory input includes
touch, pain, temperature, pressure, vision, hearing, taste, and smell
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Integration occurs primarily in the brain, where complex neural
networks analyze sensory data, form perceptions, and make decisions
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Motor output involves both voluntary actions, controlled by the somatic
nervous system, and involuntary actions, regulated by the autonomic nervous system
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Homeostatic mechanisms ensure that physiological variables remain within narrow ranges
compatible with life
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Long-term potentiation, a form of synaptic plasticity, strengthens connections
between neurons, enhancing memory storage and retrieval
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Emotional
processing involves complex interactions between the limbic system, prefrontal cortex, and other
brain regions, shaping our subjective experiences and social interactions
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Disorders of the Nervous System
Disruptions in the structure or function of the nervous system can lead to a variety of disorders,
ranging from mild to severe
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Alzheimer's disease is associated with the
accumulation of abnormal proteins, such as beta-amyloid plaques and tau tangles, in the brain
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Parkinson's disease is characterized by tremors,
rigidity, bradykinesia (slowness of movement), and postural instability
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Multiple sclerosis can cause a wide range of
symptoms, including weakness, numbness, tingling, fatigue, vision problems, and difficulties
with coordination and balance
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Strokes can be ischemic, caused by a blockage in a blood
vessel, or hemorrhagic, caused by bleeding into the brain
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The Future of Neuroscience
Advances in neuroscience continue to expand our understanding of the nervous system and its
role in human health and disease
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High-resolution imaging techniques, such as
diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS), allow researchers
to study the structural and biochemical properties of the nervous system in unprecedented detail
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Neuro rehabilitation strategies, including physical therapy, occupational therapy, speech
therapy, and cognitive rehabilitation, aim to restore lost function and improve quality of life for
individuals with neurological conditions
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By unraveling its
mysteries and harnessing its potential, we can unlock new frontiers in medicine, technology, and
our understanding of what it means to be human
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