neuroanatomy

dorsoventral

dorsum (back) → entrum (belly)

rostrocaudal/anterioposterior

longitudinal axis that runs from rostrum (beak) to caudal (tail)

mediolateral

horizontal axis that runs from the midline (medial) to the lateral margin of the animal

dorsoventral in human brain

top (head) to bottom (chin)

rostrocaudal/anteroposterior in human brain

front (eyes) to back

mediolateral in human brain

horizontal axis that runs from midline (medial) to the lateral margin of the animal

horizontal plane

coronal plane

sagittal plane

spinal cord has which regions

cervical, thoracic, lumbar, sacral

brain stem

• necessary passage for all ascending and descending tracts between forebrain and spinal cord

• modulates sensory, motor, and reflex behaviors (feeding, drinking, and respiration)

• modulation of arousal; CNS activity

medulla

• regulates autonomic functions like respiration, heart rate, and blood pressure

• PreBotzinger complex: generates respiratory rhythm

pons

• cranial nerve nuclei

• mediates sensory and motor control of the head and neck

midbrain

• voluntary motor control (substantia nigra)

• processing of auditory and visual information (superior and inferior colliculi)

brainstem is the site of 

cranial nerve nuclei

nucleus refers to

collection of neurons within a brain region

cells within a given nucleus share

the same projections, or inputs

cerebellum & motor control

modifies motor commands to adapt to desired output, accuracy of movement

cerebellum maintains

posture

cerebellum receives

sensory information from the spinal cord, balance from vestibular organs in the inner ear, and sensory information from the cortex

cerebellum is involved in certain forms of 

learning

diencephalon is comprised of

thalamus, hypothalamus

thalamus

• sensory relay center

• information from visual, auditory, and somatosensory pathways relay here on their way to sensory cortices

hypothalamus

• integrates physiology and behavior

• regulates homeostatic behaviors including feeding, thirst, regulation of sleep-wake cycle, reproduction

cerebrum is comprised of

cerebral cortex, hippocampus, amygdala

cerebral cortex

• higher order cognitive processing

• sulci and gyri increase the SA of the cortex

hippocampus

learning and memory

amygdala

formation and storage of memories associated with emotion

sulci and gyri properties

• defined by anatomical features

• not random outgrowths

• consistent across individuals

• serve as anatomical landmarks demarcating specific brain regions

sulci and gyri

sulci = in

gyri = out

central sulcus and pre/post-central gyrus importance

• precentral gyrus has motor cortex (control voluntary movement on the opposite side of the body)

• postcentral gyrus has primary somatosensory cortex (processes sensations like touch, temperature, and pain from the opposite side of the body)

frontal lobe

short-term memory, planning, control of movement

temporal lobe

auditory information, learning and memory, emotion

parietal lobe

sensory processing, language processing

occipital lobe

visual processing

white matter has ___, but gray matter has ___

axon tracts (myelin)

cell bodies 

what happens at the corpus callosum?

axons cross over so the sides can communicate with each other

true/false: in the human cortex, gray matter takes more more space than the white matter

FALSE

gray matter take up significantly less space than the white matter

ventricles contain

CSF

how does the ventricles having CSF help?

• provides protection by buffering the brain

• “floats” the CNS, reduces weight of the brain and pressure at the base of the brain (brain is about 1300g, but in CSF is 25g)

  • important because bones are very stiff and thick, so floating the tissue helps to protect it from damage during movement

ventricles remove

waste from CNS to bloodstream

waste produced by

choroid plexus - epithelial cells found inside lateral ventricles

which ventricles are the most prominent?

lateral ventricles

meninges

• protect the CNS

• cells are fibroblasts

• has 3 layers

3 layers of the meninges

dura → pia → arachnoid

bacterial meningitis

results from bacterial infection and inflammation of meninges

cervical spine

sends/receives information to/from arms/upper body

lumbar spinal cord

sends/receives information to/from legs/lower body

purple is gray matter (cell bodies)

white is axonal tracts

cervical innervates

arms

lumbar innervates

legs

thoracic innervates

core of our body

number of cells required to innervate arms/legs (and processes) is ____ than cells innervating our trunk

greater

what does it mean that the brain and spinal cord are bilaterally symmetrical?

whatever is on one side is mirrored on the other side

decussation

many projections cross to the opposite hemisphere in the brain stem

retrograde tracers

• travel from axon to cell body

• axon terminal takes up the dye, and travels back to the soma

anterograde tracers

• travel from cell body to axon terminal

• cell body takes up due, travels down axon, crosses synapse and the connected cells will take up the due

retina tracing

goes from cell body (retina), which sends projections into thalamus → send into visual cortex (occipital lobe)

rodent whisker-barrel pathway

• barrel processes whisker information

• each whisker is mapped onto the somatosensory cortex (info from each whisker goes to corresponding barrel in cortex)

• each dark structure = input from a specific whisker

• there is a topographic organization to sensory input AND motor output

true/false: neurons projecting to specific muscle groups are organized and localized to specific regions

TRUE

inject tracers into muscle groups →

• the cells there are more lateral compared to other group

• can guess that the location of the muscle is more lateral relative to other one with more medial labelling

• also look at shape of SC

motor neurons and the muscles that they innervate are ___ organized

topographically

distal muscles have cell bodies in which region?

lateral

proximal muscles have cell bodies in which segment?

medial

dorsal horn

receives and processes sensory information

ventral horn

contains motor neuron cell bodies; receive input from higher brain centers and from sensory neurons (via interneurons) to coordinate muscle contractions

lateral horn

contains neurons that control autonomic functions like heart rate, digestion, and blood vessel constriction

motor neurons innervating a single muscle distributed in

columns

medial motor column

innervates axial musculature; mediates posture

spinal accessory column

innervates neck muscles

phrenic motor column

innervates diaphragm, mediates respiration; rhythmic activity

pre-ganglionic motor column

spinal visceral motor neurons; innervate smooth muscle

hypaxial motor column

innervates musculature of the body wall (intercostal and abdominal muscles)

lateral motor column

innervates limb muscles

spatial arrangement and density of sensory receptors is mapped onto ___

the primary sensory cortex

spatial arrangement and density of sensory receptors reflects

degree of sensory sensitivity

primary motor cortex

motor maps reflect density of neuronal innervation, correlated with degree of fine motor control

primary somatosensory cortex

abundance of neurons receiving input from specific region is associated with degree of sensory sensitivity

more sensitive the area → (more/less) sensory receptors/neurons needed to innervate it

MORE

Patient presents with difficulty controlling movement of their left arm and hand. You suspect a stroke and order an MRI. In which region of the brain would you expect to observe the lesion?

• You would expect a lesion in the right motor cortex (since the right side of the brain controls the left side of the body, and the motor cortex governs movement)

• More specifically, you could see this in the pre-central gyrus of right frontal lobe

• It is the pre-central gyrus because this houses the primary motor cortex

Consider an experiment in which you inject retrograde tracers into the gastrocnemius and soleus muscles. Where in the spinal cord would you expect to observe labeled cells? Draw your answer.

• Retrograde tracer: travels from axon to cell body (the axon terminal takes up the dye and travels back to the soma)

• You would expect to observe the labelled cells (motor neurons) in the ventral horn of the spinal cord’s gray matter, since this houses cell bodies

• Specifically, they would be in the lumbar segments, since this is what innervates lower leg muscles

• Labelled cells would be on the same side as the injected muscles