Biology

• The human brain consists of different parts including the cerebral hemispheres, diencephalon, cerebellum, and brain stem, which is further divided into the midbrain, pons, and medulla oblongata

  
• The central nervous system is composed of the brain and spinal cord, while the peripheral nervous system is made up of the nerves branching out from the brain and spinal cord to the rest of the body

  
• Neurons are the basic functional units of the nervous system, responsible for receiving and transmitting signals in the form of action potentials, which are electrical impulses caused by the opening and closing of ion channels in the neuron's membrane

  
• Action potentials cause the release of neurotransmitters, chemical messengers that cross the synapse (the gap between two neurons) and bind to receptors on the next neuron, generating a new action potential in the next neuron, thus transmitting signals throughout the nervous system
• The brainstem includes the diencephalon, which consists of the thalamus and hypothalamus, and the brainstem itself, which comprises the midbrain, pons, and medulla oblongata, responsible for vital functions like heart rate, breathing, and sensory regulation
• The spinal cord, known as the nervous system's "superhighway," contains gray matter with cell bodies of neurons and white matter with long fibers of interneurons, organized into afferent tracts carrying information to the brain and efferent tracts carrying information down from the brain
• The peripheral nervous system, made up of nerves that carry messages to and from the central nervous system, includes the somatic nervous system for voluntary control over muscle movement and the autonomic nervous system for involuntary functions like stress response and relaxation
• Neurons, the basic units of the nervous system, relay and receive messages between the brain and body, with different types like motor neurons, sensory neurons, and interneurons, each playing a specific role in processing and signaling information
• The central nervous system is made up of the brain and spinal cord, while the peripheral nervous system consists of the nerves branching out from the brain and spinal cord to the rest of the body

  
• Neurons are the basic functional unit of the nervous system, responsible for receiving and transmitting signals through action potentials, which are electrical impulses caused by the opening and closing of ion channels in the neuron's membrane

  
• Action potentials cause the release of neurotransmitters, chemical messengers that cross the synapse and bind to receptors on the next neuron, generating a new action potential in the next neuron, thus transmitting signals throughout the nervous system
• The nervous system is the body's processing system, responsible for contact with the outside world, acting as the body’s control center and a communication network
• The nervous system is involved in movement, response to environmental stimuli, intelligence, self-awareness, thought, emotion, and has nerve cells called neurons
• The central nervous system is composed of the brain and spinal cord, serving as the body's control center where neurons transmit impulses
• The brain, with an average weight of 1.35kg, has parts for movement, sensing, consciousness, and involuntary functions, composed mainly of neurons
• The cerebellum, below the cerebrum, controls posture, balance, and coordination, and regulates skeletal muscle movement
• The cerebrum, the largest and most developed part of the brain, is responsible for consciousness, intellect, learning, memory, and sensations
• The brainstem includes the diencephalon, consisting of the thalamus and hypothalamus, which are key regulators of homeostasis and sensory information processing
• The brainstem also includes the pons, linking the medulla and cerebrum, regulating sensory info, facial expressions, and containing motor pathways between the cerebral cortex and cerebral hemisphere
• The medulla oblongata or spinal bulb, extending from the central brain to the spinal cord, manages vital functions like heart rate, breathing, and digestion
• The corpus callosum links the brain's two hemispheres, facilitating communication between them
• The spinal cord, the nervous system’s “superhighway,” contains central canal with cerebrospinal fluid, gray matter, and white matter with afferent and efferent tracts
• The spinal nerves are involved in reflexes and the spinal cord, with reflex being an involuntary reaction to a stimulus
• The peripheral nervous system is made up of all nerves that carry messages to/from the central nervous system, with two main parts: somatic nervous system and autonomic nervous system
• Neurons are the basic units of the nervous system, responsible for processing and signaling information, with types including motor neurons, sensory neurons, and interneurons
• Neurons have parts like dendrites, soma, and axon, with dendrites carrying impulses towards the cell body, soma joining and passing on signals, and axon carrying impulses away from the cell body
• A nerve impulse is a combination of an electrical charge and chemical reaction, moving along a neuron and transmitted by neurotransmitters across synapses between neurons
• Stimulus refers to any factor in the environment that may trigger a nerve impulse, leading to a response, which is a reaction to a stimulus
• Neurotransmitters like acetylcholine, amines (serotonin, epinephrine, dopamine, norepinephrine), amino acids (glutamate, GABA, glycine), and neuropeptides (endorphins) transmit nerve impulses across synapses between neurons
• For every postsynaptic cell, there are usually 1k-100k synaptic knobs, releasing both excitatory and inhibitory neurotransmitters that cause postsynaptic potentials
• Neurons are specialized to initiate and conduct signals known as nerve impulses
• Gray Matter consists of unmyelinated nerve fibers and cell bodies, while White Matter is composed of myelinated nerve fibers
• Endoneurium surrounds each nerve fiber, Perineurium surrounds fascicles, and Epineurium surrounds a complete nerve in the PNS or tract in the CNS
• Nerves are bundles of parallel neurons held together by fibrous connective tissue in the PNS, while tracts are bundles of parallel neurons in the CNS
• Functional Classification of Neurons:

  • Afferent (sensory)
  • Efferent (motor)
  • Interneurons (connects both)
• Structural Classification of Neurons:

  • Multipolar: one axon, several dendrites
  • Bipolar: one axon, one dendrite
  • Unipolar: dendrites at the distal end of the peripheral process
• Neuron Anatomy:

  • Myelin Sheaths: areas of insulation produced by Schwann cells to increase the speed of nerve impulses
  • Nodes of Ranvier: breaks in the myelin sheath between Schwann cells
  • Synapse: junction between two neurons or between a neuron and an effector
• Schwann Cells are only found in the PNS, support nerve fibers, and form myelin sheaths
• Multiple Sclerosis (MS) is characterized by myelin loss and destruction, plaque-like lesions, and is most common in women aged 20-40 with no known cure
• Oligodendrocytes hold nerve fibers together and produce myelin sheaths in the CNS