Topic 3: Neuroanatomy Foundations Flashcards
How was the brain historically studied
Using dissection and staining after death
What are the two types of structural imaging technologies
- Computed tomography (CT or CAT)
- Magnetic resonance imaging (MRI)
What are the two types of functional imaging technologies
- Positron emission tomography (PET)
- Functional MRI (fMRI)
New imaging techniques and advancements
- Diffusion tensor imaging
- Improving MRIs
Computed Tomopraghy
- Digitally reconstruction x-ray images
-360 degrees to provide slices of the object
Pros of CT
- Can see bone, brain, organs
- great for bleeding and tumors
- quick scan
- lower cost and shorter wait times than MRI
Cons of CT
- Low doses of radiation
- Images may not be as detailed as other techniques
Magnetic Resonance Imaging
- No radiation, just large magnetic field
- Different atoms interact differently within the magnetic field
- build a “map” based on this
- stronger magnet = clearer images (rated in telsa units - 0.5T-3T+)
Pros of MRI
- No radiation
- Great view of soft tissues
- Can highlight different types of tissues (based on type of sequencing T1 vs T2)
Cons of MRI
- Longer scan times
- can be very noisy
- metal implants may cause issues
- longer wait times and more expensive
- magnet can be dangerous (always on)
Application of MRI use with Multiple Sclerosis
- MRI is the best way to see lesions
- preferred diagnosis technique includes symptoms + imaging and other tests
- Can identify previous damage, new inflammation and even atrophy over time
Open MRI
Doesn’t require a full tube
- allows weight-bearing scans
- lower resolution images (0.5T)
Positron Emission Tomography
Imaging with radioactive tracer
- can be used with CT or MRI
- IV with tracer and compounds used by the body (eg. glucose)
- Measures metabolic activity of the cells of body tissues
-used to diagnose brain disorders, cancers, etc.
Fluorodopa
- used to detect damaged or lost dopaminergic neurons
- support the diagnosis and evaluating progression and treatment
- less highlight indicates less active neurons (more cell death)
Functional MRI
MRI to measure changes in blood flow
- Increased blood flow means increased neural activity
- No injection required and better resolution than PET
- Used to map brains for surgery, diagnose diseases, and provides many research opportunities
Diffusion Tensor Imaging
Visualizes large bundles of axons in the brain
- uses an MRI to compare the diffusion of water that occurs along axons
- direction of traces are represented with different colors
- Understand and track the changes in the structure of the brain with aging/disease
Improving MRIs
- improving scan times (2-3 minutes -> seconds)
- improving resolution of images (10T)
- segmentation of images
- Measuring different things (fluid levels, tissue stiffness, etc.)
Anatomical planes
- Sagittal: split into left and right sides
- Frontal (coronal): Splits into front and back
- Transverse (horizontal): Splits into above and below
Spinal cord function and organization
- Conduit of information (brain-body)
- Dorsal roots - sensory
- Ventral roots - motor
Peripheral Nervous System
Nervous system outside the brain and spinal cord
- Somatic PNS: innervates skin, joints, muscles
- Visceral PNS: innervates internal organs, blood vessels, glands
Dorsal Root ganglia
cluster of neuronal cell bodies outside the spinal cord that contain somatic sensory axons
Afferent vs efferent nerves
- Afferent nerves carry information toward CNS
- Efferent nerves carry information away for CNS
Def: Grey matter
neuronal bodies in the CNS
Def: Nucleus (in terms of somas)
mass of neuronal bodies in the CNS
Def: ganglion
collection of neuronal bodies in the PNS
Def: White matter
Collection of axons in the CNS
Def: Nerve
bundle of axons in the PNS
Def: Tract
Collection of axons with a common origin and destination in the CNS
Cerebrospinal Fluid
- Produced by choroid plexus found within the brain
- Circulates throughout CNS
- Absorbed into venous system
Functions of Cerebrospinal Fluid
- Protection
- Buoyancy
- Excrete waste products
- endocrine medium
Ventricles of the Brain
Lateral ventricles (1st and 2nd)
- Largest
- Filled with CSF
3rd ventricle
- between two halves of diencephalon
- filled with CSF
4th ventricle
- connected to 3rd ventricle by cerebral aqueduct
- posterior to pons and medulla, but anterior to cerebellum
- continues with central canal of spinal cord
Regions of the Forebrain
- Telencephalon
- Diencephalon
Regions of the hindbrain
- Cerebellum
- Pons
- Medulla oblongata
anatomy of Telencephalon
- largest part of human brain
Two cerebral hemispheres - Cerebral cortex (outer layer)
- White Matter
- basal ganglia
- amygdala
- hippocampus
Functions of Telencephalon
- Higher order thinking/reasoning
- Analyze sensory input and command motor output
- memory and emotion
3 Major white matter systems in the telencephalon
- Cortical white matter: axons of cerebral cortex
- Corpus Callosum: Bridge between left/right hemispheres
- Internal Capsule: Links brain to brain stem
Parts of the Diencephalon
Thalamus
- Gateway to cerebral cortex
- Via the internal capsule
Hypothalamus
- Roles in a variety of autonomic functions and hormone release
The midbrain
- Contains ascending/descending pathways between cortex, brain stem and spinal cord
- Cerebral aqueduct in center
- TECTUM: Receive sensory information for eye/ear
- TEGMENTUM: contains the substantia nigra (black substance) and red nucleus which help to control voluntary movement
The hindbrain
- Cerebellum
- most posterior
- movement control center - Pons
- Most superior/rostral
- Switchboard connecting cerebellum and cerebral cortex - medulla oblongata
- most inferior/caudal
- autonomic processes (breathing, blood pressure etc.
- Relays information to thalamus
- MEDULLARY PYRAMIDS: point of decussation (axon crossover)
The spinal cord
- White matter in outer layer
- Grey matter inside
- Spinal canal is an extension of the 4th ventricle
Def: Gyri
Bumps on cerebral Cortex
Def: Sulci
Grooves on cerebral cortex
Def: Fissures
Deep grooves in cerebral cortex
Central Sulcus
Divides Frontal lobe and parietal lobe
- Precentral gyrus: voluntary movement
- Postcentral gyrus: somatic sensation
Lateral fissure
Runs transvers seperating temporal lobe from parietal and frontal lobe
- Superior temporal gyrus (hearing) just inferior to lateral fissure
Areas of the frontal lobe
- Prefrontal cortex
- Premotor & supplementary motor area
- Primary motor cortex
Prefrontal cortex functions
- Executive function: higher cognitive processes for planning and organizing thoughts, speech, and behaviours
- Attention: can directly or indirectly influence movement
- Personality and social behaviour
Premotor & supplementary motor area functions
preparation of the body for movement
Primary motor cortex
- located in the precentral gyrus
- generates neural impulses for movement
- Somatotopic motor map
Somatotopic Motor Map
Larger area designated for areas requiring fine motor control
Areas of the parietal lobe
- Somatosensory cortex
- Posterior parietal cortex
Somatosensory cortex
- located in postcentral gyrus
- Primary area for processing somatic sensations
- Somatotropic sensory map
Posterior Parietal cortex
- Integrating sensory information
- object recognition, spatial relationships
- contributes to planning and organizing action
Occipital Lobe
- Visual cortex
- processes visual information
Temporal Lobe
- Auditory cortex
- Inferotemporal cortex: visual processing and object recognition ( quickly and easily identify objects
Thalamus
- Part of the diencephalon
- 3rd ventricle is between 2 halves
- link between sensory info and cerebrum
- Processes and directs info to specific areas
- Highly integrated with cerebellum and basal ganglia with cortex
- Axons travel through internal capsule
- Divided into sperate nuclei that project to different areas in the cortex (ventral posterior nucleus and ventral lateral nucleus)
Ventral posterior nucleus of thalamus
Projects to the postcentral gyrus
Ventral lateral nucleus of the thalamus
- Projects to precentral gyrus
- Receives input from basal ganglia
Basal Ganglia
Group of subcortical nuclei which supports the selection and initiation of movements, while preventing unwanted movements
- 4 main nuclei:
STRIATUM: receives input from cortex
- Caudate nucleus
- Putamen
GLOBUS PALLIDUS: output to thalamus
- Internal & external segment
SUBTHALAMIC NUCLEUS
- Helps regulate movement
SUBSTANTIA NIGRA
- Helps regulate movement (dopaminergic neurons)
- Degeneration in Parkinson’s disease
Pons
- Ventral to 4th ventricle
- Many ascending and descending tracts carrying sensory and motor information
PONTINE NUCLEI: most ventral aspect - relays cortical information to cerebellum
PONTINE RETICULAR FORMATION - important for respiration, taste, and sleep; as well as postural control
Cerebellum
- Most dorsal aspect of the hindbrain
- made up of folia and lobules
- vermis seperates left and right hemispheres
- deep cerebellar nuclei relay information out
- Most notable cells - purkinje cells
Purkinje cells
- Vast network of dendrites and one axons
- loss of or damage leads to movement disorders and/or coordination problems
Ataxia
Damage to the cerebellum leads to uncoordinated movements
- can use finger-to-nose test to assess
Medulla
- Most caudal portion of the hindbrain
MEDULLARY PYRAMIDS - bundles of motor axons
- primary point of motor decussation
MEDIAL LEMNISCUS - bundles of sensory axons
VESTIBULAR NUCLEUS
-Integrates information necessary for balance
DORSAL COLUMN NUCLEI - Primary point of sensory decussation
- joins up with medial lemniscus to create the dorsal column-medial lemniscus (DCML) pathway
Alcoholic Cerebellar degeneration
- heavy consumption of alcohol can cause degeneration of the cerebellum
- lead to postural instability, ataxic gait, bilateral gaze-evoked nystagmus and cerebellar tremor in both arms in case study
- Result of lose of purkinje cells
Vertebral column: vertebrae and nerves
7 Cervical - 8 nerve
12 Thoracic - 12 nerves
5 Lumbar - 5 Nerves
5 Sacral - 5 Nerves
4 Coccyx - 1 nerve
33/31
Divisions of the Spinal cord
Spinal nerve splits into 2 roots
- Dorsal= sensory
- Ventral = motor
Grey matter
- Split into dorsal, ventral and lateral horns
White matter
- split into dorsa, ventral, and lateral columns
Ascending sensory pathways
Dorsal Column: touch, proprioception
Spinothalamic tract: pain, temperature
Descending Motor Pathways
Lateral motor pathways: commands for voluntary movements
- Corticospinal tract
- Rubrospinal tract
Ventromedial motor pathways: posture and reflex movements
- Medullary reticulospinal tract
- Tectospinal tract
- Pontine reticulospinal tract
- vestibulospinal tract
