Neuroanatomy

neuron doctrine

• brain composed of separate neurons and other independent structurally, metabolically, and functionally

• info transmitted from cell to cell across synapses

synapses

tiny gaps

how many layers of the cerebral cortex

6

average adult brain

• 3 lbs

• 15 cm front to back

• cortex 3mm thick

• 86 billion neurons

cortex

outer layer of the brain

number of neurons we are born with

300 billion

soma (cell body)

• main body of a neuron

• houses nucleus and major organelles

dendrites

• composed of a main limb and extensions

• input zone of information

axon hillock

• generates action potential

• “hill” between soma and axon

axon

• singular extension

• allows action potential/nerve impulse to travel to axon terminal

• can split

bifurcating

splitting of an axon

myelin sheath

• fatty substance

• white

• protects axon

• insulates the impulse of an axon

• not continuously covering an axon

• quicker impulse transmission

• exist on SOME, not all axons

multiple sclerosis

• degenerated myelin

Symptoms

• movement issues

• pain

• migranes

• cognitive dysfunction

Source

• reactivated Epstein-Barr virus (mono)

action potential

main electrical signal that a neuron makes

• accumulation of inputs (excitatory & inhibitory)

axon terminal

houses neurotransmitters

ATP

fuel/energy for all cells

mitochondria

an organelle that is responsible for extracting energy nutrients

presynaptic membrane

releases neurotransmitter

postsynaptic membrane

binds neurotransmitters to transmit nerve signals

synaptic cleft

10-20 nanometers

synaptic vescicles

• contain neurotransmitters

• move down axon terminal, fuses with presynaptic membrane, and releases neurotransmitters

• recycled

Nervous System Cells

• sensory neurons

• motor neurons

• interneurons

sensory neurons

• detects changes in external/internal environment

• sends motor neuron signal

motor neuron

located within CNS and controls the contraction of a muscle or secretions from glands

interneuron

• located within the nervous system

• between sensory and motor neurons

Structural Classifications of Neurons

• unipolar/monopolar neurons

• bipolar neurons

• multipolar neurons

unipolar/monopolar

• 1 axon attached to soma

• axon divides (1 branch receives input , 1 branch transmits output)

• found in skin / sensory

• free nerve ending

bipolar neuron

• 1 axon 1 dendrite attached to its soma

• segregated sensory neuron (1 axon 1 dendrite)

• contain cillia

multipolar neuron

1 axon many dendrites

Supporting Cells

• glial cells

• astrocytes

• oligodendrocytes

glial cells

• neuroglia

• neural glue

• supporting cells

• 3-4x more abundant than neurons

astrocyte

• “star cell”

• glial cell

• intermediate between blood supply and neurons

• cleaning mechanism, constant fluid and chemical (waste and recycling)

• modulate neuron function

oligodendrocyte

• glial cells

• produce myelin

nodes of ranvier

• gaps between myelin sheath

• allow speed of action potential to speed up

schwann cell

• in the PNS

• wraps 1 segment of axon with myelin

microtubule

help with structure of an axon

neurofilament

made of actin

anterograde transport

movement of cellular cargo from soma to axon terminal

kinesin

• motor protein that “walk” down microtubules and carry cellular cargo (vesicles, organelles, mRNA)

• anterograde transport

retrograde transport

movement of cellular cargo from axon terminal to soma

dynein

• large cytoskeletal motor proteins that “walk” down microtubules and carry cellular cargo

• retrograde transport

neuraxis

imaginary line down through the center of the length of the nervous system

ipsilateral

same side of the body

contralateral

opposite side of the body

transverse plane

• frontal/coronal

• back from front

sagittal plane

left from right

horizontal plane

top to bottom

transverse plane

slices (like meat)

3 Layers of the Meninges

• dura mater

• arachnoid mater

• pia mater

dura mater

• outermost meninx

• flexible, unstretchable

• tough layer

arachnoid mater

middle meninx

subarachnoid space

• between arachnoid mater and pia mater (under arachnoid mater)

• space supported by trabeculae

• filled with CSF

pia mater

• innermost layer

• soft layer

cerebrospinal fluid

• produced by blood (choroid plexus filters blood)

• liquid layer of protection

• brain / spinal cord suspended

• shock absorber

• lasts ~3 hours, replaced every 6 hours

traumatic brain injury (TBI)

damage not always apparent, can accumulate

ventricles

• “little bellies”

• makes CSF

• lateral ventricles, third ventricle, fourth ventricle

lateral ventricles

ventricles that surround the thalamus

third ventricle

ventricle located in the center of the diencephalon

cerebral aqueduct

circulates CSF from third to fourth ventricle

fourth ventricle

located between cerebellum and dorsal pons

rostral frontal lobe

• forebrain

• areas of executive function (decision making, planning, etc.)

caudal frontal lobe

• motor functions

• contains precentral gyrus

• contains primary motor cortex

temporal lobe

lobe responsible for cognitive function

ex. object recognition, face recognition, language, etc.

primary auditory cortex

located in temporal lobe

central sulcus

transition from frontal to parietal lobe

parietal lobe

lobe responsible for attention and sensory integration

postcentral gyrus

• located in the parietal lobe

• houses the primary somatosensory cortex

primary somatosensory cortex

recieves information from the body

Diseases Pertaining to the Parietal Lobe

stroke causing visual/hemispatial neglect

Capgras Syndrome (imposter syndrome)

occipital lobe

lobe responsible for vision

occipital pertuberance

bump on skull pertaining to the occipital lobe

calcarine fissure

• located in the occipital lobe

• houses primary visual cortex

cerebellum

• responsible for fine motor movement

• creates connection factor when learning motor skills

lateral fissure

fissure under the frontal lobe and above the temporal lobe

grey matter

cell bodies “tucked” in sulci and gyri

white matter

myelin

insular cortex

older part of the brain

pineal gland

• in the epithalamus

• gland that regulates sleep-wake cycle

midbrain & brainstem

pons & medulla oblongata

pons

• attentional awareness

• arousal systems (sleep-wake)

• neurotransmitter systems - modulate brain activity (dopamine, seratonin, etc.) made here

medulla oblongata

• vegetative states (respiratory, cardiac function)

• regulates taste information (gag reflex)

• motor & sensory (head, neck, shoulders)

cingulate gyrus

• limbic cortex

• governs limbic system

limbic system

• controls physiological states & emotions

• hippocampus, amygdala, mamilary body, olfactory bulb, thalamus

hippocampus

• spatial recognition; “internal map”

• memory (short term —> long term, facts, places, autobiographical)

• encodes new information

amygdala

• “almond-shaped”

• regulates emotions and stress response

• sexual arousal

mamilary bodies

• pair of nuclei that regulate memory and emotion (ex. help relate memory to smell and reflexes)

olfactory bulb

• transfer smell information directly into the cingulate cortex, then to the brain

• tightly associated to the amygdala and hippocampus for memory

thalamus

• densely packed

• relays information (sensory info in —> synapse —> part of the brain, except for smell)

microglia

• smallest glial cells

• act as phagocytes and protect brain from invading microorganisms

axoplasmic transport

• active process of motor proteins carrying cellular cargo down the axon

• 2 types: anterograde, retrograde

fornix

• connects hippocampus with mamilary bodies

• above the thalamus