The Central Nervous System (CNS)

• Brain+spinal cord = CNS

  • Housed in cranium

  • Sulci (Sulcus) - Valleys

    • Deeper ones are called fissures

      • Between the hemispheres is Corpus callosum: helps send messages from one side of the brain to another if there is contralateral signaling

      • Hemisphere called Longitudinal fissure

  • Gyri (Gyrus)- Mountains

    • Bumps

What is the basic development of the CNS?

• CNS begins to form in 3rd week of fertilization

• Day 18 the neural plate emerges from the ectoderm layer of tissue

• Day 20 neural plate develops and expands giving rise to neural folds

• Day 21 neural folds invaginate(go in) & form the neural tube & heartbeat begins

  • Neural tube has head ( rostral neuropore) and a tail ( caudal neuropore)

  • Rostoral goes with top -> anterior & caudal -> spinal cord

Neuropores

What is the rostral neuropore?

• related to the encephalon (brain)

• Function: gives rise to the cerebral hemispheres, to the brain stem, and to the cerebellum

  • Cerebral hemispheres, brain stem, and cerebellum develop from the rostral neuropore

What is the caudal neuropore?

• Function: gives rise to the spinal cord

Failed Neural Tube Development

What does failed rostral neuropore failure cause?

• Anencephaly (absence of the brain)

• Microcephaly (underdeveloped brain)

What does failed caudal neuropore failure cause?

• Failure to close -> Spina bifida

Early CNS development

What happens in early CNS development?

• 16 weeks (4 mo post fertilization)- basic CNS structures in place & ready for further development

  • 4 mo in utero- muscles spontaneously move

    • Ex.pregnant women feeling flutters in belly (popcorn in belly= baby moving)

• 21 weeks- imagination of neural folds to create neural tube

  • 6 mo in utero- fetus responding to outside noise of the uterus

    • Ex. recognizing mothers voice

• Ears develop before vision

  • Ex. No vision between eyeball and brain

  • We are all born with natural auditory abilities, we should have strength in auditory system

    • Ex. if a parent says there child is a visual learner, their is breakdown in the auditory system, if they are relying on visual system for learning later.

  • We all become multisensory learners over time

• @ birth brain requires 3x amount of oxygen

  • NICU baby need much more oxygen to make sure brain is developing well

  • Neurons will proliferate at 250,000 / min ->creating 10 billion interconnecting neural circuits

• @ birth newborn demonstrates archetype reflexes ( sucking, rooting, gasping) -> mediated by medulla & cerebellum

  • What kind of cells are in the cerebellum?

    • Purkinjie cells

  • What do the cells do?

    • Responsible for archetype reflexes

• @5 posterior brain (senses) more developed than anterior of the brain (motor speech)

  • Ex. moves back to the front , C shaped, sensory before motor before the language

• @9-11 convolutions appear

• @14 brain growth begins to slow down

Embryological Phenomena that occur

What would happen if the neural pore does not fuse?

• Lead to spina bifida

What would happen if something disrupts the rostral neuropore development?

• Anencephaly (absence of the brain)

@ 4wks post fertilization what is the encephalon (brain) composed of/ What are the 3 subdivisions that develop from the neural tube?

• Prosencephalon -> becomes forebrain

  • Function: give rise to telecephalon& diancephalon

• Mesencephalon ->midbrain

  • Function: give rise to some midbrain/brainstem components

• Rhombencephalon -> hindbrain

  • Function: gives rise to medulla in cerebellum +spinal cord

Encephalon further divided

What is a brain infection called?

• Encephalitis

  • encephalon= brain overall

At 4th week of gestation the neural folds expand and fuse to form 3 primary brain vesicles. What are they, and what do they further develop into?

1. Prosencephalon is subdivided into:

   1. Telencephalon: cerebral hemisphere, white matter, basal ganglia, olfactory tract “big daddy”- most of the cerebrum

      1. Rhinencephalon is located within the telencephalon, contains the parts for olfaction

         1. Rhinencephalon means nose

         2. Cranial nerve 1 &2 are cortical

            1. CN 1 = olfactory nerve

   2. Diencephalon: thalmus, hypothalamus, pituitary gland & optic track

      1. Later becomes thalmic complex & 3rd ventricle

2. Mesencephalon: midbrain does not divide

3. Rhombencephalon is subdivided into:

   1. Metencephalon

      1. Later becomes the pons and cerebellum

   2. Myelencephalon

      1. Later becomes the medulla oblongata

   3. Rest of the rhombencephalon becomes the spinal cord

Study tip:

Prosencephalon- “Preceding present -before everything else” “Before brain and the telecephalon

Mesosephalon- “middle, medial, mid brain”

Rhombencephalon- “ apart of caudal area, rear of the brain”

Mid brain = pigSTY

• Mesencephalon

• Metencephalon

• Myelencephalon

How is embryological development, list the pieces and parts and the functions.

Week 4: Primary vesicles

Prosencephalon-> form the cerebrum

Mesencephalon-> midbrain

Rhombencephalon-> brainstem and cerebellum

End of neural tube will form spinal cord

Brain continues to develop-> 2 of the primary vesicles subdivide to form secondary vesicles

• Prosencephalon

  • telencephalon

    • Cerebral hemispheres

    • Will grow more rapidly than other parts of the tube

  • Diencephalon

    • Thalmus, hypothalamus,

• Mesencephalon= mid brain

• Rhombencephalon

  • Metencephalon

    • Pons & cerebellum

  • Myelencephalon

    • Medulla

• End of neural tube=spinal cord

Diencephalon Structures

What are the structures of the diencephalon and what are their functions?

• Subthalamus: located in subthalamic nuclei (bundles of fibers in the brain)

  • Function: receives input from globus pallidus and motor cortex &controls striated muscle

• Hypothalamus

  • Nuclei / ganglia (many neurons)

  • Structure of limbic system

  • Function: regulation of certain behaviors &metabolic function ; reproductive behavior, desire for food

• Thalamus

  • Function: relay sensory information from peripheral nervous system to the cerebral cortex

    • “Takes in sensory feeling from outside world and its a relay station before it gets to the brain”

  • Reticular activating system- arousing the cortex

    • “Alerting cortex that info is coming in”

    • Ex. ADHD studies with level of arousal that brain experiences

• Epithalamus:

  • Pineal body is responsible for glands that help develop our gonads (sex organ structures)

  • Habenular nuclei (band of fibers)

  • Habenular commissure (gap)

  • Striae medularis

  • Posterior commissure

What happens if the reticular activation system is damaged?

• You will die, because if we arent arousing the cortex to any stimuli then there is no stimuli for the brain to process, theres a lack of awareness and you will likely pass

Brain (Encephalon)

• Precentral gyrus - motor strip

• Postcentral gyrus-sensory strip

• Lateral fissure - separates frontal lobe from temporal lobe

• Longitudinal fissure- seperates the hemisphere

• Sylivian fissure

• Fissure of Rolando - separates the parietal lobe from the frontal lobe

• Super marginal gyrus- important for reading

• Angular gyrus - important for reading

• Hessels gyrus

• Brochas area

• Wernicke's area

• Broadmans

The Cerebrum

Test tip:

The cerebrum is going to be all the structures related to the telencephalon ( where we talk about different lobes)

What are the parts of the cerebrum and whats its function?

• Its the control center & holds billions of neurons / glial cells

• 1. Hemispheres

  • Left & Right and they are connected by (fibers) colled the corpus callosum

• 2. Limbic system: subcortical system

• 3. Basal nuclei (basal ganglia): subcortical

• Function: controls thinking functions

What are the 3 meningeal linings wrapped around the brain?

• Dura mater (outside)

• Arachnoid mater “lacy spider web appearance”

• Pia mater

What kind of fluid is in the brain?

• Cerebral spinal fluid

Cortical Divisions

What is similar and what is different between right and left hemispheres?

Meningeal linings of the cerebrum

What are the meningeal linings of the cerebrum?

• Dura mater - tough, most superficial “duracel battery- tough”

  • Epidural space- superficial to dura mater

• Arachnoid mater- lacey spiderlike blood vessels “spider sucking blood vessels”

• Pia mater - thin covering contours (on top) of brain

  • Supports neural vascular tissue

  • Protects and nurtures central nervous system (CNS)

  • Supports brain

• Megingeal linings of spinal cord

  • Protec from shocks due to movement trauma

Ventricles and cerebrospinal fluid (CSF)

Layers of Cerebrum

Corticobular Tract

Corticospinal tract

Upper Motor Neurons (UMN)

Lower Motor Neurons (LMN)

+/- signs of UMN

Signs of LMN lesions

Landmarks of cerebrum

The motor homonculus & sensory homonculus

The frontal lobe

The parietal lobe

The temporal lobe

The insula

The occipital lobe

The perisylvian zone

Surface of cerebral cortex

Types of Fibers

White matter association pathways

The limbic system

Anatomy of subcortex

Diencephalon Structures

The association cortex

The cerebellum

The cerebellar feedback loop

The brainstem

The spinal cord