Central Nervous System

Brain

• receives information - receptors

  • interoceptors - internal (organs)

  • exteroceptors - external (various senses)

  • proprioceptors - body position/limbs

• processes information - memory

• returns instructions for body’s response - somatosensory system

Spinal cord

Transmits stimuli to/from brain to peripheral nervous system

Meninges

• specialized linings of CNS

• neural crest

• layers

  • dura mater - tough, fibrous, thick, outermost layer

  • arachnoid - middle layer

  • pia mater - single/few cells on the surface of the brain

Ventricles

• chambers within the brain

  • lateral (left and right)

  • third

  • fourth

• filled with cerebrospinal fluid (CSF)

• choroid plexus - makes CSF and located in the lateral ventricles

Choroid plexus

• tufts of blood vessels

• ependymal cells

• generates CSF

  • protects the brain

  • has no RBCs/WBCs

  • eventually absorbed back into the circulatory system

Blood brain barrier

space between the blood vessels and CSF that protects the brain from pathogens

Fish meninges phylogeny

primitive meninx

Amphibians, reptiles, and birds meninges phylogeny

• dura mater

• secondary meninx

Mammals meninges phylogeny

• all three layers

  • dura mater

  • arachnoid

  • pia mater

Where is CSF initially at before it moved throughout the ventricles?

the sub-arachnoid space

Brain embryology

• arises from the ectoderm

• neural plate → neural crest → neural tube → 3 regions

  1. Rhombencephalon

  2. Mesencephalon

  3. Prosencephalon

Rhombencephalon

embryologic hindbrain that further develops into the metencephalon and myelencephalon

Mesencephalon (embryology)

the embryologic midbrain, undergoes no further folding

Prosencephalon

embryologic forebrain that further develops into the telencephalon and diencephalon

Brain segementation

• size on complexity of regions vary based on evolution of species

• related to function of organisms

  • ex.

    • Rhombencephalon - ubiquitous across many species

    • Olfactory bulbs - enlarged in sharks, rays, and mammals

    • Forebrain/cortex - enlarged in tetrapods

Medulla oblongata

• part of the myelencephalon

• distal portion of the brain/superior part of the spinal cord

• function

  • contains cranial nerves 6-12 cells bodies

  • visceral, autonomic reflexes - respiration and heartbeat

  • pathway for ascending stimuli to “higher” brain centers and descending stimuli to spinal cord

• VITAL TO LIFE (relation to heartbeat and respiration)

Pons

• part of the metencephalon

• aka Pontine nuclei

• transmits information between cerebellum and cerebral cortex

  • proprioception

  • compensatory movements

  • balance

• cranial nerve nuclei/cell bodies

• arousal, respiration, autonomic functions

Cerebellum

• “little brain”

• maintains equilibrium/balance

• processes sensory input - sight, touch, vision, hearing

• motor action - fine tune motor stimulus

• motor learning - walking, reaching, pointing

• well developed organisms that must survive in currents and stay upright (fish) have a well developed cerebellum

Mesencephalon

• receives/processes sensory stimuli

• tectum - superior portion

  • optic tectum - visual stimuli

  • toris simicularis - auditory stimuli

• tegmentum - inferior portion

  • motor output - third and fourth cranial nerves (eye movement)

• fine tuning of motor movements

• well developed in fish, amphibians - sensory input from eyes

• includes the cerebral peduncles, corpora quadrigemina, and cerebral aqueduct

• substantial nigra - “black-colored” cell bodies

Tectum

• superior portion of the mesencephalon

• optic tectum - visual stimuli

• toris simicularis - auditory stimuli

Tegementum

• tegmentum - inferior portion of the mesencephalon

• motor output - third and fourth cranial nerves (eye movement)

What clinical relevance do nigra bodies have in humans?

People with Parkinson’s Disease tend to have an absence of substantia nigra

Thalamus

• part of the diencephalon

• bi-lobed, sensory/motor info

Hypothalamus

• part of the diencephalon

• endocrine functions

Pituitary gland

• part of the diencephalon

• endocrine function

Pineal gland

• part of the diencephalon

• circadian rhythym

Mammillary bodies

• part of the diencephalon

• emotion, behavior, memory

Cerebrum

• generally a large portion of the brain

• sulci/sulcus - grooves on brain surface

• gyri/gyrus - ridges/folds on cerebral surface of brain

• proprioceptors - sensory receptors that detect position and movement

Phylogeny of the brain

• matches demand for information processing

• forebrain - olfaction, behaviors, muscle control

• midbrain - visual, lateral line systems

Grey matter

• includes neurons - cell bodies

• outermost area of the brain

• innermost area of the spinal cord

  • dorsal horn - receiving incoming afferent sensory stimuli, sends to brain

  • ventral horn - motor neurons, effector neurons

White matter

• the axons/nerve tracts - myelin sheaths

• innermost area of brain

• outermost area of spinal cord