Neuro exam week 3

CNS protection

The skull protects and supports the brain. The vertebrae protects and supports the spinal cord/the delicate nervous system.

Meninges

3 protective membranes that cover and protect the brain. PAD - Pia, Arachnoid, Dura

Dura mater

• The outermost, dense, fibrous meningeal layer

• Consists of two layers periosteal and meningeal

• Periosteal is attached to the inner surface of the skull while meningeal is closer to the brain

• The separation of these 2 layers in some areas create sinus spaces which are important for blood and CSF drainage

2 potential spaces of Dura mater if injury occurs

• Epidural - between skull and dura

• Subdural - between dura and arachnoid

Extensions of Dura Mater

these extensions go inward and help support/separate certain parts of the brain + add more cushion and support

Falx cerebri - separates left and right hem of the brain, sits in the longitudinal fissure

Tentorium cerebelli - separates the cerebrum above from the cerebellum below, divider between temporal/occipital lobes and the cerebellum

Falx cerebelli - separates left and right hem of the CEREBELLUM

Arachnoid mater

• thin membrane between the dura and the pia

Subarachnoid space

• between arachnoid and pia mater, CSF flows and floats around in this space

• Arachnoid trabeculae - made of fibrous and elastic tissue, helps connect arachnoid mater to pia mater (spider web like)

Pia mater

• innermost thin layer that sticks directly to the surface of the brain and follows it’s contours

• highly vascular - carries arteries and veins to the neural tissue

Cerebral Spinal Fluid (CSF)

• colorless fluid that is generated by the choroid plexus located in the ventricles

• circulates in the ventricles and subarachnoid space

• mechanical cushion for the CNS, brain floats in CSF, CSF protects the brain and spinal cord from injury from sudden and violent movements

• Reduces brain weight by 95%

• removes harmful substances and metabolic waste and delivers nutrients

• CSF is replaced 3 times within 24 hours

3 major divisions of the brain

cerebrum, cerebellum, brainstem

Cerebrum

• largest part of the brain

• covered by 3 membranes (PAD), floats in fluid (CSF) and encased in bony skull

• mostly involved in sensation, reasoning, planning, abstract thinking, and higher mental processes like language

Cerebral hemispheres

• separated into right and left by the longitudinal fissure

• the two hems r connected by commissural fibers known as the corpus callosum

• the two hems look approx the same but are different in function (bilateral anatomic symmetry, unilateral functional symmetry)

• left brain func: science, math, knowledge, language, analytical thought

• right brain func: holistic thinking, reading, art, creativity, intuition

Gray matter

grayish/brownish cell bodies of neurons that process information

Cerebral cortex

• made out of gray matter, covers the cerebrum

• 3-5mm thick layer of neurons

• Convoluted surface:

  • Gyri - ridges/elevations of the cerebral cortex on surface of cerebrum

  • Sulci - groove like depressions on surface of cerebrum

  • these ridges and grooves allow for more cellular volume by increasing surface area

White matter

• groups of myelinated axons (nerve fibers) transmit information

• they are white because of the myelin sheath

• Association fibers. - moving from one region to another in the same hem

• Commissural fibers - from one hem to the other (corpus callosum)

• Projection fibers - runs from cortex to brainstem/spinal cord and vice versa

Frontal lobe

• executive functioning and motor production

Parietal lobe

• sensory integration

Occipital lobe

• visual processing

Temporal lobe

• auditory processing and comprehension

Longitudinal fissure

separates right and left hem

Central sulcus

separates frontal and parietal lobes

Lateral sulcus/sylvian fissure

• anterior/front part separates frontal and temporal lobes

• posterior/back part separated parietal and temporal lobes

Parieto-occipital sulcus

separates parietal and occipital lobes

Subcortical structures

structures underneath the cerebral cortex

Telencephalon

• basal ganglia - motor coordination

• amygdala and hippocampus - limbic system, emotion and memory

Diencephalon

• Thalamus- sensory + motor relay center (traffic director)

• Hypothalamus - temp, hunger, thirst, sleep, emotion (body regulator)

Cerebellum

• metencephalon

• “little brain”

• crucial connections to cortical and subcortical structures, brainstem, and spinal cord

• responsible for balance and smooth motor coordination, movement learning

Brainstem

• Mes-, Met-, and Myelencephalon

• Connects diencephalon and spinal cord

• Monitors all outputs and inputs in the brain

• Automatic control system (ex: breathing, swallowing, heart rate)

  • prewired/genetically acquired

• Structures: midbrain, pons, medulla

  • Pons and medulla are 2 structures where cranial nerves usually emerge

Embryonic neural development of the -ecephalons

• Telencephalon → Cerebrum - Cerebral Cortex, Basal Ganglia, Hippocampus, Amygdala

• Diencephalon → Thalamus, Hypothalamus, and Epithalamus

• Mesencephalon → midbrain - Tectum and Tegmentum

• Metencephalon → pons and cerebellum

• Myelencephalon → Medulla