Nervous System Notes

Cellular Functions of the Nervous System

Coordinates cellular functions in three steps: senses information, processes responses, issues commands to muscles and organs.

Central Nervous System (CNS)

Composed of the brain and spinal cord, responsible for processing sensory inputs and coordinating responses.

Peripheral Nervous System (PNS)

Composed of nerves leading to and from the CNS, enabling sensory input and motor output.

Sensory Division (PNS)

Carries signals from receptors to the CNS regarding environmental changes.

Motor Division (PNS)

Carries signals from the CNS to muscles and glands.

Somatic Motor Division

Controls voluntary movements of skeletal muscles.

Autonomic Nervous System (ANS)

Controls involuntary responses (to smooth muscles, cardiac muscles, and glands).

Sympathetic Division (ANS)

Prepares the body for action (fight or flight response).

Parasympathetic Division (ANS)

Calms the body, promoting rest and digestion.

Neurons

Main communication cells of the nervous system. Approximately 1 trillion neurons present.

Neurosoma (Cell Body)

Contains the nucleus and organelles; lacks centrioles, does not undergo mitosis.

Dendrites

Receive input from neighboring neurons and increase connectivity and information processing.

Axon

Transmits signals to other cells, forming synapses at the axon terminal.

Multipolar Neurons

Neurons characterized by one axon and multiple dendrites; most common type.

Bipolar Neurons

Consist of one axon and one dendrite; commonly associated with sense organs.

Unipolar Neurons

Feature one process leading away from the soma, branching into a T-shape; primarily sensory.

Sensory (Afferent) Neurons

Relay sensory information to the CNS; usually classified as unipolar or bipolar.

Interneurons

Process, store, and retrieve information within the CNS; typically multipolar.

Motor (Efferent) Neurons

Conduct signals from the CNS to effectors (muscles and glands); generally multipolar.

Neuroglial Cells

Support and protect neurons, outnumbering them at least 10 to 1.

Oligodendrocytes

Form the myelin sheath around CNS axons.

Ependymal Cells

Line brain cavities and produce cerebrospinal fluid (CSF).

Microglia

Function as immune cells that clear debris and pathogens from the CNS.

Astrocytes

Support neurons, maintain the blood-brain barrier (BBB), and regulate blood flow.

Satellite Cells (PNS)

Provide support and protection for neuron cell bodies.

Schwann Cells (PNS)

Form the myelin sheath for PNS axons and facilitate regeneration after injury.

Myelin Sheath

Insulates axons, increasing the speed of signal conduction; formed by oligodendrocytes and Schwann cells.

White Matter

Composed of myelinated axons; primarily involved in signal transmission.

Gray Matter

Contains neuron cell bodies, dendrites, and unmyelinated axons; involved in processing information.

Resting Membrane Potential (RMP)

Charge difference across the neuronal membrane when not stimulated; maintained by the sodium-potassium pump.

Sodium-Potassium Pump

Transports 3 Na+ ions out and 2 K+ ions in per cycle to maintain resting membrane potential.

Ligand-Gated Channels

Open in response to the binding of a specific molecule.

Voltage-Gated Channels

Open in response to changes in membrane potential.

Local Potential

Initial change in membrane potential that can initiate an action potential if strong enough.

Action Potential

Rapid, all-or-nothing response that propagates along the axon involving depolarization and repolarization.

Continuous Conduction

Propagation of action potentials typically occurring in unmyelinated axons.

Saltatory Conduction

Takes place in myelinated axons, facilitating quicker signal transmission.

Transmitting Nerve Signals

Action potentials trigger the release of neurotransmitters into the synaptic cleft, influencing postsynaptic activity.

Parkinson's Disease

Disease characterized by progressive loss of motor control due to degeneration of dopamine-releasing neurons