Organization of the Nervous System

Dorsal

upper side/Back

ventral

bottom side/stomach side

anterior/rostral

towards head

posterior/caudal

towards tail

medial

closer to middles

lateral

closer to side

sagittal plane

down middle

axial plane

top and bottom

coronal plane

front and back

ipsilateral

same side

contralateral

opposite side

Spinal cord components

• dorsal root

  • somatic and visceral sensory afferents

• Dorsal root ganglia

  • somas of sensory afferents

• ventral roots

  • somatic and visceral motor (efferents)

• spinal nerves

  • mixed

Cranial nerves

• 12

• mostly innervate the head

• axons from CNS, somatic PNS, visceral PNS

meninges

• 3 membranes that surround the brain and spinal cord

  • dura mater

  • arachnoid trabeculae

  • pia mater

subarachnoid space

• CSF circulates in after coming from ventricles

• blood vessels

ventricular system

ventricles and CSF

ventricles

cerebrospinal fluid-filled caverns and canals inside brain

Cerebrospinal fluid (CSF)

• produced by choroid plexus in ventricles

• protects brain by cushioning it

• conduit for hypothalamic peptide hormones

• circulates through ventricles → subarachnoid space → reabsorbed in arachnoid villi and arachnoid granulations into venous sinuses

dura mater

• tough outermost membrane enveloping the brain and spinal cord

• periosteal layer

• meningeal layer

superior sagittal sinus

on the outer surface of the brain that collects blood from the brain's superficial veins and drains it into the transverse sinuses

choroid plexus

specialized ependymal cells surrounding capillaries in ventricles that produce CSF

subdural hematoma

• trauma damages tiny veins within the meninges

• Blood accumulates rapidly, causing pressure to rise within the brain

• Results in loss of consciousness, paralysis or death

subarachnoid hemorrhage

• sudden bleeding into the subarachnoid space (csf mixes with blood)

• Symptoms include sudden, severe headache, usually with loss or impairment of consciousness.

• frequently a sign of a ruptured aneurysm

MRI over CT

• more detail

• doesn’t require x rays

  • uses info on how hydrogen atoms respond in the brain to perturbations of a strong magnetic field

Functional MRI

• active neurons have increased blood flow

• detect changes in regional blood flow and blood O₂ in the brain

CNS development

• forms from walls of a fluid filled neural tube

• inside of the tube becomes ventricular system

• rostral → prosencephalon of forebrain

• mesencephalon/midbrain

• caudal → rhombencephalon of hind brain

neural tube development

5 major divisions of brain, development

differentiation

process by which structures become complex and specialized

ex. retina derived from forebrain

Brain derivation chart

Forebrain structural features

• telencephalon

• diencephalon

telencephalon

• cerebral hemispheres

• olfactory bulbs

• basal telencephalon (forebrain)

  • hippocampus

  • basal ganglia

  • amygdala

• lateral ventricles

diencephalon

• thalamus

• hypothalamus

• third ventricle

cerebral cortex

• analyze sensory input and command motor output

thalamus

• gateway to the cortex

• axons from thalamus to cortex pass through the internal capsule

• carry info from contralateral (opposite) side of the body

hypothalamus

• controls

  • autonomic nervous system

  • endocrine system

  • homeostatic behaviors (Eating, drinking)

midbrain structure-function relationships

descending axons

• descending from cortex to brain stem and spinal cord, motor systems

• ex. corticospinal tract: motor cortex to spinal motor neurons

ascending axons

• info conduit from spinal cord and brainstem to forebrain, sensory system

tectum

• superior colliculus (sensory info from eye)

• inferior colliculus (sensory info from ear)

tegmentum

• substantia nigra - part of basal ganglia

• red nucleus - control voluntary movement

  • origin of rubrospinal tract

pons

pontine nuclei receive inputs from corticospinal tract axons

relays info to contralateral cerebellum

cerebellum

coordination of movements

corticospinal fibers

continue toward the spinal cord in medullary pyramids

spinal cord

ascending (sensory) and descending (motor) spinal tracts

types of cerebral cortex

neocortex

archicortex

paleocortex

neocortex

• frontal, parietal, occipital, temporal lobes

• in mammals

  • 6 layers

• brodmann’s areas: 52 areas that differ in cytoarchitecture

• evolution:

  • amount of cortex has changed but not the structure

  • primary sensory areas, primary motor area

  • expansion of secondary (association) areas

archicortex

hippocampus

paleocortex

olfactory cortex/piriform lobe

separated from neocortex by rhinal fissure

Primary motor cortex

M1, area 4

• initiation of complex voluntary movement

Supplementary motor area (SMA) and premotor area (PMA)

area 6

motor planning

Parietal-Temporal-Occipital association cortex

• analysis of sensory inputs

• constructs representation of our sensory world

prefrontal association cortex

• executive function

• abstract thought

• decision making

• anticipating consequences of action