Overview of the Nervous System Structure and Function

Dendrites

Branched projections that receive signals from other neurons

Cell body

Contains the nucleus and integrates incoming signals

Axon hillock

Where action potentials are initiated (start point)

Axon

Long projection that carries signals away from the cell body

Nerve

Bundle of axons in the PNS

Ganglion

Collection of neuron cell bodies in the PNS

Bipolar neuron

Has ONE dendrite and ONE axon

Multipolar neuron

Has MANY dendrites and ONE axon (most common type)

Unipolar neuron

Has ONE process that splits into two branches

Sensory (afferent) neuron

Carries signals TO the CNS

Motor (efferent) neuron

Carries signals FROM the CNS

Resting membrane potential

-70mV (inside of cell is negative)

Causes resting potential

Na+/K+ pump moves 3 Na+ out and 2 K+ in

Depolarization

Membrane becomes less negative (more positive)

Hyperpolarization

Membrane becomes more negative

Action potential trigger

Depolarization

Depolarization process

Na+ channels open and Na+ rushes INTO the cell

Repolarization process

K+ channels open and K+ flows OUT of the cell

Schwann cells function

Form myelin sheaths around PNS axons

Satellite cells function

Surround neuron cell bodies in PNS ganglia

Oligodendrocytes function

Form myelin sheaths in the CNS

Astrocytes function

Most abundant glial cells, form blood-brain barrier

Microglia function

Immune cells that clean up debris in CNS

Ependymal cells function

Line ventricles and produce CSF

Synapse

Gap between two neurons where communication occurs

Presynaptic terminal

Releases neurotransmitters

Postsynaptic terminal

Receives neurotransmitters

Neurotransmitter release trigger

Calcium enters the presynaptic terminal

Temporal summation

Multiple signals from the SAME synapse add up

Spatial summation

Signals from DIFFERENT synapses add up

Convergence

Multiple neurons connect to ONE target neuron

Divergence

ONE neuron connects to multiple target neurons

CNS

Brain and spinal cord

PNS

All nervous tissue outside the brain and spinal cord

Three meninges

Dura mater, arachnoid mater, pia mater

Four ventricles

Two lateral ventricles, third ventricle, fourth ventricle

CSF

Cerebrospinal fluid - cushions and protects the brain

CSF production location

Choroid plexus in the ventricles

Cranial nerves count

12 pairs

Olfactory nerve (I)

Smell

Optic nerve (II)

Vision

Oculomotor nerve (III)

Eye movement

Facial nerve (VII)

Facial muscles and taste

Vagus nerve (X)

Parasympathetic control of organs

Sensory neurons entry point

Dorsal (posterior) root

Motor neurons exit point

Ventral (anterior) root

Parts of a reflex arc

Receptor, sensory neuron, integration center, motor neuron, effector

Knee-jerk reflex type

Monosynaptic stretch reflex (fastest)

Withdrawal reflex type

Polysynaptic protective reflex

Ascending tracts

Carry sensory information UP to the brain

Descending tracts

Carry motor commands DOWN from the brain

Cerebrum function

Higher functions: thinking, memory, consciousness

Brainstem function

Vital functions: breathing, heart rate, blood pressure

Cerebellum function

Balance and coordination

Corpus callosum function

Connects left and right brain hemispheres

Left hemisphere specialization

Language and logic

Right hemisphere specialization

Spatial processing and creativity

Thalamus function

Relay station for sensory information

Hypothalamus function

Controls homeostasis (temperature, hunger, hormones)

Primary motor cortex location

Frontal lobe

Primary somatosensory cortex location

Parietal lobe

Visual cortex location

Occipital lobe

Auditory cortex location

Temporal lobe

Hemispheres connection

Corpus callosum

Sympathetic nervous system

"Fight or flight" response

Parasympathetic nervous system

"Rest and digest" response