Overview of Nervous Tissue and CNS/PNS Functions

Dendrites

Receive signals (like tree branches catching rain)

Cell Body

Contains nucleus, integrates signals (city hall)

Axon Hillock

Where action potentials start (hill where trigger is pulled)

Axon

Carries signals away (highway)

Presynaptic Terminal

Releases neurotransmitters (shipping dock)

Nerve

Bundle of axons in PNS (like rope made of threads)

Tract

Bundle of axons in CNS

Bipolar Neuron

ONE dendrite, ONE axon (retina, olfactory)

Multipolar Neuron

MANY dendrites, ONE axon (most common, 99%)

Unipolar Neuron

ONE process that splits (sensory neurons)

Afferent Neurons

ARRIVING at CNS (sensory)

Efferent Neurons

EXITING from CNS (motor)

Resting Membrane Potential

-70mV (inside negative)

Na+/K+ Pump

3 Na+ out, 2 K+ in

Depolarization

Makes membrane less negative, closer to threshold (-55mV)

Schwann Cells

Make myelin (one cell = one internode)

Satellite Cells

Surround cell bodies in ganglia (like satellites orbiting)

Oligodendrocytes

Make myelin (one cell myelinates multiple axons)

Astrocytes

Blood-brain barrier, support (star-shaped stars of support)

Microglia

Immune defense (micro-warriors)

Ependymal Cells

Line ventricles, make CSF

Synaptic Transmission Steps

"Action Calcium Fuses Binds Opens Clears"

Temporal Summation

Same synapse, rapid succession (TIME-based)

Spatial Summation

Different synapses, same time (SPACE-based)

Convergence

Many → One (roads to city)

Divergence

One → Many (river delta)

CNS Components

Brain + Spinal cord (command center)

PNS Components

Cranial nerves + Spinal nerves + Ganglia + Receptors

Dura Mater

Tough outer (durable leather)

Arachnoid Mater

Web-like middle (spider web)

Pia Mater

Delicate inner (tissue paper)

CSF Flow Pathway

"Lateral Third Aqueduct Fourth Canal Space"

Sensory Neurons

ENTER: Dorsal root (back where you receive back rubs)

Motor Neurons

EXIT: Ventral root (front where you act with front limbs)

Reflex Arc Components

"Real Sensory Integration Makes Effects"

Knee-jerk Reflex

Monosynaptic, stretch reflex, fastest

Withdrawal Reflex

Polysynaptic, protective, slower, uses interneurons

Ascending Tracts

Sensory going UP to brain

Descending Tracts

Motor coming DOWN from brain

Left Hemisphere Functions

Language, Logic, Analysis (LEFT = LANGUAGE)

Right Hemisphere Functions

aRtistic, sPATial, intuitive (RIGHT = aRtistic)

Thalamus Function

Relay station for sensory info (train station)

Hypothalamus Function

Homeostasis control (temperature, hunger, hormones)