Organization and Cells of the Nervous System

Electrical and Chemical signals

Fast, efficient and specific methods of communication used by neurons to transmit information.

Sensory input

is the process by which sensory receptors and nerves take in stimuli from the environment and convert them into signals for the nervous system. externally and internally.

Integration

is the process where the nervous system combines sensory information to make decisions or generate responses.

Motor output

is the process by which the nervous system sends signals to muscles or glands in response to integrated sensory information, leading to movement or action.

Central Nervous System (CNS)

Integration/command center, contains brain and spinal cord.

Peripheral Nervous System (PNS)

Messages to and from the brain and spinal cord (spinal and cranial nerves).

Sensory afferent fibers (PNS)

carries impulses from skin/skeletal muscle and joints to brain. These fibers transmit sensory information, allowing the body to perceive touch, pain, temperature, and proprioception.

Visceral afferent fibrers (PNS)

carries impulses from internal organs to the brain, providing information about the internal state of the body.

Motor (PNS)

efferent fibers that carry impulses from the brain and spinal cord to muscles and glands, facilitating movement and physiological responses.

Sensory (PNS)

afferent fibers that transmit sensory information to the brain.

Somatic Nervous System (PNS Motor Dvision)

the part of the peripheral nervous system responsible for voluntary movements, connecting the central nervous system to skeletal muscles and mediating sensory information.

Autonomic Nervous System (PNS Motor Dvision)

the part of the peripheral nervous system that controls involuntary functions, regulating activities of internal organs and glands without conscious control. Has sympathetic and parasympathetic nervous systems.

Neurons

Excitable cells that transmit electrochemical signals and release neurotransmitters to communicate between the nervous system and other body parts.

Supporting Cells

Non-neuronal cells in the nervous system that provide support, protection, and nourishment to neurons, including astrocytes, oligodendrocytes, and Schwann cells.

Astrocytes

Most abundant supporting cells, Anchor neurons to there nutrient supplies and take up glucose from capillaries. They metabolize glucose for neurons to make ATP. They also aid in synapse formation, neurogenesis, proper neuronal formation, nurturing and maintenance. They release gliotransmitters and scavenge K+ from the extracellular environment.

Gliotransmitters

Chemical signals released by glial cells that can modulate neuronal activity and influence synaptic transmission.

Blood Brain Barrier

Separates blood-borne substances from neurons (protective). Contains continuous endothelium with tight junctions, a thick basal laminar membrane and astrocyte foot processes.

BBB ineffective against

Substances that can diffuse through plasma membranes (lipophilic substances, gasses, EtOH)

BBB Absent

in areas that monitor chemical comp of the blood (vomiting centers, hypothalamus)

Substances that require special transporters to cross in BBB

Ions, polar molecule, glucose

Ependymal Cells

Epithelial cells wich line the central brain cavities (ventricles) and produce cerebrospinal fluid (CSF). They help maintain the blood-CSF barrier.

Microglia

Immune cells of the brain/brain macrophages. Monitor health of neurons and phagocytize microorganisms/pathogens and celldebris within the central nervous system.

Overactive microglia

Releases free radicals and can contribute to neuroinflammation and neurodegenerative diseases by excessively responding to injuries or infections in the central nervous system.

Oligodendrocytes

Branched cells that wrap multiple axons within the CNS to form myelin sheaths, which insulate and enhance the speed of nerve impulse transmission.

Myelin sheaths

phospholipid-rich insulated coverings around axons/ speed up nerve conduction.They are formed by oligodendrocytes in the CNS and Schwann cells in the PNS, providing essential support for efficient neuronal communication.

Schwann cells (neurolemmocytes)

Form the myelin sheaths around PNS localized axons and support peripheral nerve regeneration. They play a crucial role in protecting and insulating the nerve fibers in the peripheral nervous system.

Satellite cells (ganglionic gliocytes)

Provide nutrient support around the PNS ganglia. They regulate the microenvironment of neurons and are involved in cell signaling.

Neuron Anatomy

The structural unit of the nervous system, long-lived cells that transmit signals throughout the body. Neurons consist of a cell body, dendrites, and an axon, facilitating communication between the brain, spinal cord, and peripheral organs.

Perikaryon

The cell body of a neuron that contains the nucleus and organelles, supporting the metabolic and synthetic functions of the neuron.

Amitotic

Describes cells that do not undergo mitosis and cannot divide, such as neurons.

Neurofibrils

Bindles of intermediarte filaments that maintains neuronal shape and support intracellular transport, playing a key role in the structural integrity of neurons.

Nissle bodies (rough ER)

Aggregates of rough endoplasmic reticulum and ribosomes found in the cell bodies of neurons, involved in protein synthesis.

Axon hillock

cone shaped area from which axons arise in neurons, responsible for action potential initiation.

Nuclei vs Ganglia

Nuclei are clusters of neuronal cell bodies located within the central nervous system, while ganglia are clusters of neuronal cell bodies found in the peripheral nervous system, primarily serving as relay points.

Axons

long, slender projections of neurons that transmit electrical impulses away from the cell body, facilitating communication with other neurons and muscle cells.

Dendrites

Branch-like extensions of neurons that receive signals from other neurons, transmitting them toward the cell body. Provide a very high surface area to receive signals from other neurons. Always unmyelinated.

Tracts

bundles of neurons in CNS

Nerves

bundles of neurons in PNS

Anterograde

Describes the transport of materials from the cell body of a neuron TO the axon terminals, important for signaling and growth.

Retrograde

Describes the transport of materials from the axon terminals back TO the cell body of a neuron, important for recycling and communication.

Interneurons

Shuttles signals through CNS pathways between sensory and motor neurons.

Nodes of Ranvier

Gaps in the myelin sheath (which contain voltage-regulated Na channels) between adjacent schwann cells, which occur at regular intervals. Alow for fast nerve conduction.

Saltatory Conduction

A form of nerve impulse transmission where action potentials jump from one Node of Ranvier to another, increasing the speed and efficiency of signal propagation along myelinated axons.

Nerve Regeneration

The process by which damaged nerve cells can repair themselves and restore function, primarily seen in peripheral nerves. It involves the regrowth of axons and reconnection with target tissues.

Nerve growth Factor

are proteins that support the growth, survival, and differentiation of developing and mature neurons. They play a critical role in nerve regeneration and maintenance.

Brain-derived Neurotrophic Factor (BDNF)

a neurotrophic factor that promotes the survival and growth of neurons, influencing neuroplasticity and cognitive function.

Glial cell-line Derived Neurotrophic Factor (GDNF)

a neurotrophic factor that supports the survival of specific types of neurons and promotes nerve growth, particularly in the peripheral nervous system.

Neurotrophin-3

a neurotrophic factor involved in the support and maintenance of neurons, especially during development.