Intro + CNS

CNS FCNS

• controls + coordinates other organs and systems in body

• sense environment, move, make descions based on info

• controls = coordinates muscle movements

Homeostasis → need food → energy

Taxa used to Study Animal Brains

• Cnidaria

• Annelida

• Mollusca

• Nematoda

• Arthropods

• Craniata

• Echinodermata

NS Trends

1. Central nervous System

2. Bilateral Symmetry

3. Specialized functions of individual neurons

4. cephalization

Why is the brain in the head?

move forward in one direction → sensory organs are concentration

Schwann Cells

• Located in periphery

• form the myelin sheath around a single neuron

Where are synaptic proteins and ion channels present?

• fungi

• single-celled organisms

Arthropod Ventral Nerve Cord

• each segment houses one ganglion

• cns is bilaterally symmetrical

Ganglions Comprise?

• Tract

• Commissure

• Neuropile

• Neuron Cell Bodies

3 Major Brain Parts

• Forebrain

• midbrain

• hindbrain

= 5 subdivisions

What does brain develop from (vertebrates)?

• develops as tube from the neural plate

Ectoderm→ neural plate → neural tube

Ectoderm & Notochord function

• produce molecules that act as inductive signals for dorsoventral axis

BMP

Bone Morphogenic Hormone

• in ectoderm

SHH

Sonic Hedgehog Protein

• in notochord

Anterior Neural Tube

differentiates into vesicles that give rise to main subdivisions of the brain

Anteroposterior Pattern

driven by the expression of different inductive signals

What Causes Further Subdivisions

• complex expression of inductive signals

• Ex hindbrain divided into 8 rhombomeres

Cerebral Cortex Features

1. Cell bodies of cortical neurons are arranged in layers or sheets

2. layer of neurons closet to the surface is separated from the pia mater by a zone that lacks neurons

3. At least one cell layer contains pyramidal cells that emit large dendrites that extend up to layer 1

4. diff types of cortex based on architecture

Peripheral Nervous System

• PNS

  • Somatic and Visceral

Somatic PNS

• all spinal nerves that innervate the skin, joints, and muscle

• under voluntary control

• motor neurons cell bodies are in the spinal cord

• sensory neurons cell bodies in dorsal root ganglia

Visceral PNS

• autonomic

• neurons innervate internal organs, blood vessels, glands

• control smooth muscle in blood vessels, intestines, cardiac muscles

Glial Cells

1. serve supporting elements

2. remove debris, scavengers

3. Buffer and maintain [K+] in extracell space

4. guide migration of neurons and growth cones

5. form BBB

   1. can signal and communicate within NS

Types of Glial Cells

1. Schwann Cells (PNS)

2. Oligodendrocytes (CNS)

3. Astrocytes

Schwann Cells

• PNS

  • produce myelin sheath that surrounds axon in periphery

• 1 cell furnishes one small axon segment

Oligodendrocytes

• CNS

• produces myelin sheath that surrounds axons in CNS

  • 1 cell can furnish axons of many neurons

Astrocytes

• most numerous glia

• irregular star-shaped bodies with long processes called end feet

• contact the surface of neurons, blood vessels and endothelial cells in BBB