CNS 1 (in person)

Function

• Main regulator of body
• Able to take in information from all over, integrate the information together, and make decisions based off of it
• There are functional changes of the CNS over lifespan

Brain and Spinal Cord protection

• Skin, muscle, bone, meninges
• Cranial bones cover brain, vertebrae encase spinal cord
• Inner covering is 3 layers of connective tissue called meninges that cover brain and spinal cord

Meninges(external to deep)

Dura Mater

• Strong white fibrous tissue (2 layers that come together as one, periosteal and meningeal)

Arachnoid mater

• Delicate, spiderweb like layer

Pia mater

• Transparent layer, sticks to outer surface of brain and spinal cord, has blood vessels

Spaces

• Epidural space: on top of dura mater of spinal cord and vertebrae, has fat
• Subdural space: beneath dura mater and above arachnoid mater, has lubricating serous fluid
• Subarachnoid space:below arachnoid mater, above pia mater, has cerebrospinal fluid (TEST QUESTION: what is found in subarachnoid space→ cerebrospinal fluid)

Extensions of Meninges

Dural Sinuses

• Extension of dura mater, function as veins, returns blood from brain to hear, eg. superior sagittal sinus

Falx Cerebri

• Extenison of dura mater, sperates two cerebral hemispheres

Falx Cerebelli

• Extension of dura mater, separates two cerebellar hemispheres

Tentorium Cerebelli

• Extension of dura mater, Separates cerebellum from cerebrum

Filum terminale

• Extension of pia mater: anchors end of spinal cord to coccyx

Denticulate ligament

• Extension of pia mater: anchors spinal cord transverely to vertebrae

Cerebrospinal Fluid (CSF)

Function

• Supportive, protective cushion
• Fluid is constantly circulating, as it passes by certain sensors the sensors can determine health of person, detects internal cahnges

Formation

• Occurs in choroid plexus, network of capillaries/blood vessels projects from pia mater into ventricles
• Each plexus lined with Ependymal cells which take out things from the blood to make CSF
• Choroid plexuses continue to make CSF, and old stuff is disposed uf
• Old CSF goes through extensions called arachnoid villi from subarachnoid space into superior sagittal sinus to leave our head

Locations

• Subarachnoid space, brian and central space of spinal cord
• Ventricles: fluid filled spaces
  • Lateral ventricle: first and second, one in each hemisphere
  • Third ventricle: thin, vertical pocket of fluid, below lateral ventricles
  • Fourth ventricle: tiny, diamond shaped space, cerebellum attaches to brainstem
• Also in central canal of spinal cord

Lumbar Puncture (spinal tap)

• Withdraw of CSF from subarachnoid space for testing purposes to diagnose infection, etc
• Around L4 inline with iliac crest of hip
• 2cm below end of spinal cord because there are few spinal nerve so minimize damage
• Patient has to be on side and knees drawn to chest to expose intervertebral space

Epidural

• Injection of pain med into epidural space, injects into fatty space, eg. in labour

Basic structure of spinal cord

• Oval shaped cylinder, gets smaller/tapers as it descends
• Runs from foramen magnum to lower border of L1 vertebrae then stops
  • Conus Medullaris: inferior end of spinal cord
  • Cauda Equina: bundle of nerve roots coming off of conus medullaris
  • FIlum terminale: extension of pia mater from end of spinal cord to coccyx
  • Cervical enlargement: contain neurons of upper limb
  • Lumbar enlargment: contain neurons of lower limb
• Sensory (afferent) neurons: send infor from periphery to CNS, dorsal
• Interneurons: within CNS, integrate information from afferent neurons
• Motor (efferent) neurons: exits CNS/spinal cord, projects to periphery to effector cells, ventral/anterior
• Grey Matter
  • Gets colour due to different things that make it up, inner butterfly looking structure of spinal cord
  • Interneurons located here
• White matter
  • External part of cord
  • Anterior median fissure signals Front/anterior part of spinal cord
• Nerve roots: bundles of nerve fibers(axons) that project from each side of spinal cord
  • Dorsal nerve root (posterior): contains unipolar sensory neurons only (no myelin sheath)
    • Dorsal root ganglion: a swelling in the dorsal nerve root, has cell bodies of sensory neurons only
  • Ventral nerve root (anterior): contains axons of multipolar motor neurons only, cell body of these motor neurons is in the grey matter
• Spinal Nerve: both dorsal and ventral roots come of the spine and come together to form spinal nerve, conatins both sensory and motor which is part of the PNS

CNS 11A (online)

Gray Matter

• Columns of gray matter extend length of spinal cord
• Contains cell bodies of interneurons and motor neurons (sensory cell bodies in ganglion)
• Anterior horns, posterior horns, and lateral horns of gray matter, gray commissure
• Central conal: contains cerebral spinal fluid
• Contains unmyelinated axons, cell bodies, synapse, and neuroglia
• Spinal reflex centers are in grey matter, quick responses that just go to spinal cord and not brian

White matter

• Bundles of axons are found divided into tracts (colums)
• Highways that run up and down spinal cord and communicate to brain, conduction routes
• Gets its colour from myelin on axons, has myelinated axons
• One tract with a bunch of different axons will originate and terminate in the same structure, they can originate from one area of the spine, and terminate in the brain
• All axons of one tract serve the same general function
• Names of tracts indicate location, where axons originate and where they terminate
  • Eg. Spinocerebellar tracts: originate in spine and terminate in cerebellum
• Ascending tracts: axons of sensory neurons, conduct impulses upwards towards brain
• Descending tracts: axons of motor neurons, conduct impulses down the spinal cord from brain

Somatic Sensory Pathways in CNS

• For cerebral cortex to perform sensory functions, impulses have to be conducted to sensory areas by sensory pathways

Primary Sensroy Neurons

• Signal omes from periphery and travels to spinal cord or brain stem on this neuron

Secondary Sensory Neurons

• From primary once it reaches spinal cord or brainstem, travels to brain, more specifically thalamus
• Spinothalamic tract: spine, running along tract to thalamus

Tertiary Sensory neurons

• From the brain, traveling from thalamus to cortex of the brain (postcentral gyrus of parietal lobe)
• Thalamorcortical tract: thalamus to cortex

CNS 11B (online)

Brain

• One of largest organs, about 3 pounds
• Alost 100 billion neurons and glia
• Most ne neurons are produced before and shortly after birth
• After birth, neurons grow in size, many synapses can form and become broken
• Brainstem: medulla oblongata, pons, midbrain
• Cerebellum: second largest part of brain
• Diencephalon: thalamus, hypothalumus, pineal gland
• Cerebrum: largest part of brain

Gray Matter

• Contains cell bodies, synapses, and neuroglia
• External cortex of cerebrum and cerebellum
• Integrate and processes information before response is initiated (reflex, conscious or unconscious)

White matter

• Contains bundles of axons/tracts which are myelinated
• Ascending or descending tracts
• More inside of brain, conduction routes to and from brain

Cerebrum

• Largest uppermost part of brain
• Has two halves, right and left cerebral hemispheres divided by longitudinal fissure (falx cerebri)
• Each hemisphere divided into 5 lobes: frontal, parietal, temporal, occipital, insula

Cerebral cortex

• Outer surface made up of 6 layers of gray matter
• Millions of axon terminals

External features

Gyri: convolutions or bumps that you can see

• Precentral gyrus, postcentral gyrus, cingulate gyrus, hippocampal gyrus

Sulci and Fissures: grooves inbetween gyri

• Longitudinal fissure: deepest, divides cerebrum to two hemispheres
• Lateral fissure: between temporal and parietal lobes
• Central sulcus: between frontal and parietal lobes
• Parietooccipital sulcus: between occipital and parietal lobes

Function

Postcentral gyrus

• General somatic sensory area
• Receives impulses from receptors activated by heat, cold, and touch

Precentral gyrus

• Somatic motor area, controls individual muscles
• Neurons found juste before precentral gyrus are referred to as secondary motor area to coordinate groups of muscles simultaneously for controlled movement
• Sends info through descending tracts to stimulate skeletal muscles

Transverse gyrus

• Found within temporal lobe, primary auditory area

Occipital lobe

• Primary visual areas

Basla Nuclei, Internal Capsule, Corpus Striatum

• Regulation of voluntary motor control related with posture, walking, other repetitive movements, emotions, thinking and learning
• There needs to be coordination with all muscles involved in process

Basal Nuceli(ganglia)

• Islands of gray matter deep inside white matter of each hemisphere
• Include lentiform nucleus: putamen and pallidum, amygdaloid and caudate nucleus

Internal capsule

• associated with basal ganglia, mass of white matter

Corpus striatum

• Includes caudate nucleus, internal capsule, and lentiform nucleus

Cerebral Tracts: Cerebrum’s white matter

Association tracts

• Most numerous in cerebrum, extend from gyrus to gyrus

Commissural tracts

• Extend from 1 gyrus to corresponding gyrus in other hemisphere
• Eg. corpus callosum; connects right and left hemispheres, anterior and posterior commissure

Projection tracts

• Project away from brain, sensory and motor tracts, connect brain to other parts of nervous system

Connectome

• Map of all neural connections in brain

Diancephelon

• • Between cerebrum and midbrain, around third ventricle
  • includes thalamus, hypothalamus, pineal gland, and optic chiasma

Thalamus

• Dumbbell shaped mass of gray matter, has many nuclei, surrounds third ventricle on lateral sides
• Large number of axons that conduct inputs into thalamus, major relay station for sensory impulses on way to cerebral cortex
• Involve in emotions, arousal mechanism, producing complex reflex movements

Hypothalamus

• Beneath thalamus
• Forms floor of third ventricle
• Consists of several structures, connected to pituitary gland through infundibulum; a stalk
• Important for survival and enjoyment, links mind and body, links nervous and endocrine system
• Major regulator and coordinator of autonomic activities
• Relay station between cerebral cortex and lower autonomic cneters
• Expressing emotions, maintaining water balance, synthesizes hormones from posterior pituitary, arousal, regulating appetite, major role in homeostasis of body temperature

Pineal Gland

• Just above midbrain
• Regulates bodies biological clock (circadian rythem), produces melatonin as timekeeping/sleep hormone
• As sunglight disapears melatonin levels increase

Structure of Brainstem

• Sensory, motor, and reflex function
• Made of white matter (projection tracts) and reticular formation (network of white and gray matter)

Medulla Oblongata

• Lowest part, attaches to spinal cord right above foramen magnum
• Pyramids: 2 bulges of white matter on ventral side, formed by fibers/axons of pyramidal tracts
• Nuclei: clusters of neuron cell bodies locatied in reticular formation
• Responsible for autonomic reflexes: cardiac, vasomoto, and respiratory centers, eg. vomiting, coughing, sneezing, etc

Pons

• Above medulla, below midbrain
• Involved with cranial nerve reflexes and pneumotaxic centers that regulate respiration

Midbrain

• Above pons, below diacephalon/cerebrum, midsection of the brain
• Has a red nucleus and substantia nigra: clusters of cell bodies of neurons for muscle control
• Involved with cranial nerve reflexes and communication with midbrain and cerebrum, has auditory and visual centers

Tracts

• Columns of white matter passing through brainstem
• Spinoreticular, spinothalamic, cotrcospinal, reticulospinal tracts

Structure of Cerebellum

• Just below posterior part of cerebrum, separated by transvers fissure (tentorium cerebelli)
• Second largest part of brain
• More neurons than rest of nervous system combined, a lot of computing power
• Has numerous sulci and gyri, gyri are more slender and less prominent, run parallel to each other: folia
• 2 cerebellar hemispheres, separated by menigeal extension; falx cerebelli
• Vermis: central part wormlike appearance

Cerebellar Cortex

• Made of gray matter; cell bodies, synapses, neuroglia

Arbor vitae

• White matter of internal part of cerebellum, short and long tracts
• Shorter tracts: conducts impulses from neurons in cerebellar cortex to neurons inside cerebellum
• Long tracts: conucts impulses to and from cerebellum,
  • Nerve impulses are conducted along peduncles

Peduncles

• Each peduncle allows for passage of different long tracts

Inferior cerebellar

• Spinocerebellar, vestibulocerebellar, and reticulocerebellar

Middle cerebellar

• Pontocerebellar tracts

Superior Cerebellar

• Tracts from dentate nuclei through midbrain (red nucleus) to thalamus

Dentate Nuclei

• Cerebellar nuclei in each hemisphere
• Tracts connect these nuclei with thalamus and motor areas in cerebral cortex
• Allows for cerebellum and motor cortex to influence one another

Functions

• Achievement of coordinated movements is from combined effects of cerebrum and cerebellum
• Produces skilled coordinated movement of groups of muscles
• Maintains balance, controls posture, processes sensory information in environment

Consciousness

• State of awareness of ones self, environment and other humans
• Dependent on excitation of cortical neurons (neurons in cortex) by impulses that are conducted to them by network of neurons called reticular activating system (RAS)
• Without continual excitation of cortical neurons someone cannot be conscious or aroused

Language

• Ability to speak and write words, ability to understand spoken and written words
• Speech centers Located in frontal parietal and temporal lobes
• Language centers located in left cerebral hemispher in 90%, right in 10%

Emotions

• The limbic system: Subjective experiencing and objective expressing of emotions
  • Includes cingulate gyrus and hippocampus: on media surface of cerebrum
  • Have primary connections with various other parts of brain

Memory

• Major mental activity
• Cerebral cortex is capable of sotring and retrieving short and long term memory
• Functions of many parts of cortex, especially temporal, parietal and occipital lobes
• Structural changes of neural pathways are what allows long term memory to be stored
• Limbic system is a key role in memory