Chapter 1 - Intro/Basic Neuroanatomy

Neuron Doctrine

Neuron Doctrine

-The brain is composed of independent cells

-Signals are transmitted from cell to cell across gaps (synapses)

Who proposed the neuron doctrine?

Santiago Ramon y Cajal

Unipolar neurons

a single extension branches in two directions, forming an input zone and an output zone

Bipolar neurons

one axon, one dendrite - usually sensory

Multipolar Neurons

one axon, many dendrites - most common type

What are the 4 functional zones of the neuron?

input zone, integration zone, conduction zone, output zone

Input Zone

where neurons collect and integrate information, either from the environment or from other cells

Integration Zone

where the decision to produce a neural signal is made

Conduction Zone

where information can be transmitted over great distances

Output Zone

where the neuron transfers information to other cells

What are the three functional kinds of neurons?

Sensory, Motor, and Interneurons

Sensory Neurons

respond to environmental stimuli, such as light, odor, or touch

Motoneurons

stimulate muscles or glands

Interneurons

receive input from and send input to other neurons (most neurons in CNS)

What are the four kinds of glial cells?

Astrocytes, Oligodendrocytes, Ependymal Cells, and Microglia

Astrocytes

-Most numerous glial cells in brain

-Fill spaces between neurons for support

-Provide the blood-brain barrier

-Regulate composition of the extracellular space

Astrocytoma

malignant tumor of astrocytes

Alexander Disease

astrocytes fill with GFAP (a protein), then fail

Oligodendrocytes

Wrap axons with myelin sheaths inside brain and spinal cord

Nodes of Ranvier

gaps in the myelin sheath

Multiple Sclerosis

oligodendrocyte injury from autoimmune attack, usually triggered by a viral infection

Microglia

cells that move around cleaning up debris from dying neurons and ganglia

Ependymal Cells

Line ventricles, secrete and absorb CSF

AIDS Encephalitis

brain damage in patients from neurotoxins glutamate and NO produced by viral-activated microglia

What is meant by neural plasticity?

Dendritic spines' number and structure are rapidly altered by experience

In what order does information flow through a synapse?

Presynaptic Terminal - Mitochondria - Synaptic Vesicles - Synaptic Cleft - Presynaptic Membrane - Postsynaptic Membrane - Dendritic Spine

Autonomic Nervous System

automatic arousal control

Preganglionic Neurons

run from CNS to autonomic ganglia

Postganglionic Neurons

run from the autonomic ganglia to targets in the body

Sympathetic Activation

prepares body for action

Parasympathetic activation

rests and digests

Afferent

carries impulses into a region of interest (sensory)

Efferent

carries impulses away from a region of interest (motor)

Coronal

separates brain from front to back

Sagittal/Midsagittal

slices the brain down the midline so you can see what's on each half

Horizontal

Separates brain from top to bottom

White Matter

composed of axon bundles. White because myelin sheaths (white fatty tissue) cover the axons

Gray matter

composed of clusters of neuron cell bodies, have dark gray appearance

What are the four cortical lobes?

frontal, parietal, temporal, occipital

Basal Ganglia

movement control

Limbic System

emotional memory, regulation (surrounds the basal ganglia)

Diencephalon

Our 'first brain' in human evolution, powers reflexive control of our behavior

Midbrain

includes reticular formation which controls sleep and arousal, body temperature

Brainstem

medulla, pons, midbrain

Pons

contains motor and sensory nuclei to face

Medulla

transition of brain to spinal cord, heart rate, breathing

Cerebellum

motor coordination and learning

Meninges

brain wrappings; includes dura mater, subdural space, arachnoid membrane, subarachnoid space, and pia meter

Subdural hematoma

pertaining to below the dura mater, tumor of blood

Cerebral Ventricles

make CSF which surrounds and cushions the brain

CSF Flow

produces inside the brain, circulates, then exits the brain

Hydrocephalus

accumulation of fluid in the spaces of the brain due to circulation failure

How many layers does the cerebral cortex have?

six

White matter tracts (axons)

connect brain areas

Denser the tissue...

the whiter the image

Asymmetry is abnormal in a CT scan of the brain

True

Positron Emission Tomography (PET)

identifies which brain regions contribute to specific functions by injecting radioactive chemicals to map their destination by their emissions; few clinic uses

Functional MRI

revolutionized study of the human brain; shows how networks of brain structures collaborate

Soma

Cell body

Nucleus

DNA in chromosomes, mRNA transcribed from DNA, gene expression

Rough ER

Arrays of membranes with ribosomes, site of protein synthesis for membrane associated proteins

Smooth ER

regulates cytoplasm

Golgi Apparatus

Stacks of flat membrane compartments, packages products for shipment in the cell

Lowe Syndrome

Low quality vesicles made in the Golgi apparatus lead to mental retardation, facial deformities, seizures, kidney function, etc.

Microtubules

spirals of tubulin, rail tracks inside neuron

Neurofilaments

static support structures, twisted cables

Anterograde transport

material is moved from soma to axon terminals using kinesin

Retrograde transport

material is moved from terminals to soma using dynein

Lissencephaly

smooth brain

MELAS Syndrome

mitochondrial energy failure; Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke

Larger Neurons

-Have more complex inputs and outputs

-Cover greater distances

-Convey information more rapidly