CNS: higher function, protections and spinal cord

Pyramidal cells

• output cells of the neocortex excitatory (glutamatergic)

• integrating information and sending it to a different location

There are also many local interneurons

• mostly inhibitory-basket cells and chandeliers cells (GABAergic-peptidergic)

• some excitatory- stellate cells(layer 4, glutamatergic)

Layer lll of cerebral cortex

• external pyramidal cell layer

• small pyramidal cells and local interneurons

• information flow to other cortical areas

Layer lV of cerebral cortex

• internal granule cells

• granule cells-local interneurons

• information flow to other cortical areas and Thalamus

Layer V of cerebral cortex

• internal pyramidal cell

• mostly large pyramidal cells

• Information flows to other cortical areas and oppostie hemisphere

EEG

• electrical recordings from the surface of the scalp-larger amplitude=more synchronization of many APs from many neurons

Alpha

• low amplitude, regular: alert relaxed state

Beta

• more rapid and more irregular: alert and concentrating

Theta

• larger and slower: unusual in adults

Delta

• high amplitude, slower: seen when reticular system is suppressed during sleep or under anesthesia

Sleep

• common patterning of health sleep progression

REM

• skeletal muscles (except ocular and diaphragm) are actively inhibited; most dreaming occurs

State N1

• relaxation begins; EEG shows low-amplitude mixed-frequency and alpha waves; arousal is easy

Stage N2

• irregular EEG with sleep spindles(short high-amplitude bursts); arousal is more difficult

Stage N3

• EEG has high-amplitude theta and delta waves; vital signs decline; arousal is difficult; bed-wetting, night terrors, and sleepwalking may occur

Spinal cord

• extends from foramen magnum (medulla oblongata) to 2nd lumbar vertebra

• 16-18 inches long

• cervical and lumbar enlargements-more info being processed and usage\

Conus medullaris

• tapered end of spinal cord

Filum terminale

• connects meninges to coccyx

Cauda equina

• (horse tail): bundle of descending spinal nerves

Dorsal root

• sensory(afferent) axons

Dorsal root ganglion

• contains afferent cell bodies

ventral root

• Motor (efferent) axons

Spinal nerve

• mixed sensory and motor nerve fibers

Local flow of information

1. Peripheral stimulation activates sensory neuron

2. Signal propagates down sensory neuron to dorsal horn

3. Synapse onto inter neuron or directly to motor neuron

4. Activation of motor neuron

5. Activation of muscle

Ascending tracts of spinal cord

• conduct sensory impulses to the brain

Descending tracts

• conduct motor impulses from the brain to motor neurons reaching muscles and glands

Fasciculus gracilis and cuneatus of ascending tracts

• touch, pressure vibration and proprioception of upper and lower limbs and chest

• They cross over information in the medulla oblongata

Spinothalamic of ascending tract

• the anterolateral or spinothalamic pathways carry mainly pain and temperature impulses

• Lateral spinothalamic tract carries pain, temperature

• Anterior(ventral) tract carries touch and pressure

• Axon in the spinothalamic tract cross over information in the spinal cord

Corticospinal

• lateral and anterior

• Control of skeletal muscles

Reticulospinal

• lateral, anterior, medial

• Control muscle tone and sweat glands

Corticospinal tracts

• carry motor commands

• Fibers originate in the cerebral cortex

• Most information crosses over in the medulla, some in the spinal cord

• Synapse either directly onto motor neurons or onto an interneuron that synapses onto a motor neuron

Dura mater: meninges of the brain

• periosteal layer: fused to periosteum

• Meningeal layer

• Dural sinus between layers(some areas)

Arachnoid mater

• attaches to dura mater

• May be separated by subdural space

Subarachnoid space

• filled with CSF, trabeculae

Pia mater

• attached to the surface of the brain, astrocyte interaction

Dural folds

• extensions of the meningeal cranial dura into cranial cavity

• Theses folds stabilize and support the brain

• Contain collecting veins(Dural venous sinuses)

• Three largest Dural folds: flax cerebri, tentorium cerebelli, falx cerebelli

Cerebrospinal fluid

• mechanical and metabolic protection

Choroid plexus

• many infoldings-villi

• Extract water from blood and transport to CSF

Blood brain barrier- highly distributed structure

• Primary: tight junctions between capillary endothelial cells. Some role for end feet of astrocytes-molecular uptake, induction

• BBB not present in choroid plexus, arachnoid villi and regions of the brain responsible for monitoring blood quality or neuro-hormonal secretory areas(hypothalamus, pituitary gland, pineal gland)