Communication – The nervous system transmits signals between different body parts.
Control & Coordination – It regulates body activities by responding to internal and external stimuli.
Sensory Input – Detects changes in the environment (e.g., touching a hot stove).
Integration – Processes and interprets sensory input (e.g., recognizing the heat as dangerous).
Motor Output – Responds by activating muscles or glands (e.g., pulling the hand away).
Central Nervous System (CNS)
Function: Processes information and coordinates responses.
Structures: Brain and spinal cord.
Peripheral Nervous System (PNS)
Function: Connects the CNS to limbs and organs.
Structures: Cranial nerves, spinal nerves, and ganglia.
Subdivisions:
Sensory (Afferent) Division – Transmits signals to the CNS.
Motor (Efferent) Division – Sends responses from CNS to muscles/glands.
Somatic Nervous System (Voluntary) – Controls skeletal muscles.
Autonomic Nervous System (Involuntary) – Regulates internal organs.
Sympathetic (Fight or Flight) – Increases heart rate, dilates pupils.
Parasympathetic (Rest and Digest) – Slows heart rate, stimulates digestion.
CNS Glial Cells:
Astrocytes – Provide structural support, regulate the blood-brain barrier.
Microglia – Act as immune cells, removing debris and pathogens.
Ependymal Cells – Line brain ventricles, produce cerebrospinal fluid (CSF).
Oligodendrocytes – Form myelin sheaths in the CNS.
PNS Glial Cells:
Schwann Cells – Produce myelin sheath in the PNS.
Satellite Cells – Support neuron cell bodies in ganglia.
Diagram Labels & Functions of Each Part:
Dendrites – Receive signals from other neurons.
Cell Body (Soma) – Contains the nucleus and organelles.
Axon – Conducts electrical impulses away from the cell body.
Axon Terminals – Release neurotransmitters to signal other neurons or muscles.
Overall Function: Insulates axons and speeds up electrical impulses.
Difference in CNS vs. PNS:
CNS: Myelin is produced by oligodendrocytes.
PNS: Myelin is produced by Schwann cells.
Resting Potential (-70mV):
Na⁺/K⁺ pump maintains resting state (Na⁺ out, K⁺ in).
Depolarization:
Voltage-gated Na⁺ channels open → Na⁺ rushes into the neuron.
Membrane potential becomes positive (+30mV).
Repolarization:
Na⁺ channels close, K⁺ channels open → K⁺ rushes out of the neuron.
Membrane potential returns to negative.
Hyperpolarization:
Too much K⁺ exits, making the membrane briefly more negative than resting potential.
Return to Resting Potential:
Na⁺/K⁺ pump restores ion balance.
Neurotransmitter Release:
Action potential reaches the axon terminal → triggers Ca²⁺ influx.
Vesicles release neurotransmitters into the synaptic cleft.
Neurotransmitters bind to receptors on the next neuron or muscle.