നാഡീവ്യൂഹം: ന്യൂറോണുകളും ഗ്ലിയൽ കോശങ്ങളും

• The nervous system is a complex network of cells that transmits electrical and chemical signals throughout the body.
• It is responsible for coordinating and regulating bodily functions, as well as enabling sensation, movement, and cognition.

Cells of the Nervous System

• Neurons are the fundamental units of the nervous system, specialized for transmitting information. Glial cells provide support and protection for neurons.

Neurons

• Neurons transmit signals via electrical impulses called action potentials.
• They have a cell body (soma), dendrites (which receive signals), and an axon (which transmits signals).
• Communication between neurons occurs at synapses through the release of neurotransmitters.

Glial Cells

• Astrocytes provide nutrients and support to neurons, regulate the chemical environment, and contribute to the blood-brain barrier.
• Oligodendrocytes (in the central nervous system) and Schwann cells (in the peripheral nervous system) form myelin sheaths around axons, increasing the speed of signal transmission.
• Microglia act as immune cells in the brain, removing debris and protecting against pathogens.

Organization of the Nervous System

• The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).

Central Nervous System (CNS)

• The CNS includes the brain and the spinal cord.
• The brain is the control center of the body, responsible for higher-level functions such as thought, memory, emotion, and language.
• The spinal cord transmits signals between the brain and the rest of the body and mediates reflexes.

Peripheral Nervous System (PNS)

• The PNS consists of nerves and ganglia outside of the brain and spinal cord.
• It is divided into the somatic nervous system (controls voluntary movements) and the autonomic nervous system (controls involuntary functions).
• The autonomic nervous system is further divided into the sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) divisions.

Brain Structure and Function

• The brain is a complex organ with distinct regions, each responsible for specific functions.
• Key brain regions include the cerebrum, diencephalon, brainstem, and cerebellum.

Cerebrum

• The cerebrum is the largest part of the brain, divided into two hemispheres (left and right).
• Each hemisphere is further divided into four lobes: frontal, parietal, temporal, and occipital.

Frontal Lobe

• Responsible for higher cognitive functions such as planning, decision-making, working memory, and language (Broca's area).
• It also controls voluntary movements (motor cortex).

Parietal Lobe

• Processes sensory information such as touch, temperature, pain, and spatial awareness.
• It is involved in integrating sensory and motor information.

Temporal Lobe

• Involved in auditory processing, memory formation, and language comprehension (Wernicke's area).
• It also plays a role in object recognition and emotional responses.

Occipital Lobe

• Primarily responsible for visual processing.
• It receives and interprets information from the eyes.

Diencephalon

• Located beneath the cerebrum.
• Contains the thalamus and hypothalamus.

Thalamus

• Acts as a relay station for sensory information, transmitting signals to the cerebral cortex.
• It also plays a role in regulating sleep, alertness, and consciousness.

Hypothalamus

• Regulates body temperature, hunger, thirst, sleep-wake cycles, and hormone release.
• It connects the nervous system to the endocrine system via the pituitary gland.

Brainstem

• Connects the brain to the spinal cord.
• Consists of the midbrain, pons, and medulla oblongata.

Midbrain

• Involved in motor control, vision, hearing, and sleep-wake cycles.

Pons

• Relays signals between the cerebrum and cerebellum.
• It is involved in regulating sleep, respiration, and swallowing.

Medulla Oblongata

• Controls vital functions such as heart rate, blood pressure, and breathing.
• It also mediates reflexes such as vomiting, coughing, and sneezing.

Cerebellum

• Located at the back of the brain.
• Coordinates movement, balance, and posture.
• It also plays a role in motor learning and cognitive functions.

Neural Communication

• Neurons communicate with each other through electrical and chemical signals.

Action Potentials

• Action potentials are rapid changes in the electrical potential across the neuron's membrane.
• They are triggered when the neuron reaches a threshold potential.
• Action potentials travel down the axon to the synapse.

Synaptic Transmission

• At the synapse, the action potential triggers the release of neurotransmitters from the presynaptic neuron.
• Neurotransmitters bind to receptors on the postsynaptic neuron, causing a change in its membrane potential.
• This can either excite (depolarize) or inhibit (hyperpolarize) the postsynaptic neuron.

Neurotransmitters

• Neurotransmitters are chemical messengers that transmit signals between neurons.
• Examples include acetylcholine, dopamine, serotonin, norepinephrine, glutamate, and GABA.
• Each neurotransmitter has specific receptors and effects on the postsynaptic neuron.

Neuroplasticity

• Neuroplasticity is the brain's ability to change and adapt in response to experience.
• It involves changes in the strength of synaptic connections, as well as the formation of new synapses and neurons.
• Neuroplasticity is essential for learning, memory, and recovery from brain injury.

Development of the Nervous System

• The nervous system develops in a series of stages, starting with the formation of the neural tube in the embryo.

Neural Tube Formation

• The neural tube gives rise to the brain and spinal cord.
• Neurons and glial cells proliferate, migrate, and differentiate into specialized cell types.

Synaptogenesis

• Synapses form between neurons, and neural circuits are established.
• Synaptic connections are refined through activity-dependent mechanisms.

Myelination

• Myelin sheaths form around axons, increasing the speed of signal transmission.
• Myelination continues throughout childhood and adolescence.

Disorders of the Nervous System

• Many disorders can affect the nervous system, including neurological disorders, psychiatric disorders, and neurodevelopmental disorders.

Neurological Disorders

• Examples include stroke, epilepsy, Parkinson's disease, Alzheimer's disease, and multiple sclerosis.
• These disorders can result from genetic factors, environmental factors, or injury to the brain or spinal cord.

Psychiatric Disorders

• Examples include depression, anxiety disorders, schizophrenia, and bipolar disorder.
• These disorders are thought to involve imbalances in neurotransmitter systems or abnormalities in brain structure or function.

Neurodevelopmental Disorders

• Examples include autism spectrum disorder, attention-deficit/hyperactivity disorder (ADHD), and intellectual disability.
• These disorders result from abnormalities in brain development that can affect cognition, behavior, and social functioning.