Structure of the nervous system @ Macroscopic level Brain & nerves @ Microscopic level Neurons & Glial Cells

Macroscopic: Divisions of the Nervous System Central (inside skull & spine) Brain Spinal Cord Peripheral (outside skull & spine) Nerves

Central Nervous System Brain

Divisions of the human brain

Specialization of function Different regions of the brain are associated with different function

Spinal Cord Reflex Group activity Spinal cord lesion Ouch! That hurts, dude! Spinal cord lesion Here is where spinal cord lives. Nerves leave spinal cord from between vertebrae (thus if discus moves, or pinch) there is pain (similar to facia paralysis following inflamation of facial nerve, or oppression of optic nerve by pituitary tumor). Would sensation be abolished by: a spinal cord lesion? polio? - Would the reflex be abolished by: - a spinal cord lesion? - polio?

Peripheral Nervous System Somatic System: - controls voluntary muscle Autonomic System: - controls glands & internal organs - has two subcomponents - Sympathetic (adrenaline): arousal - Parasympathetic: calm

Figure 3.28 The Autonomic Nervous System

Levels of Investigation Brain Areas (visual system) Cells (neurons) Molecules (neurotransmitters)

Microscopic level: Neurons

Neurons: Its many shapes & sizes

Neuron: basic parts Cell Body football field Dendrite Campus Axon wide a street Axon long as Philly - Ohio Cell membrane thick as pinky finger Synaptic cleft thick as thumb # synapses 10.000 (same number as Villanova students) axon terminals Some axons are wrapped burrito-style by fatty cells (glial cells) - increases speed at which neurons communicate) - white in color (white matter vs gray matter - is destroyed by multiple sclerosis

Neuron: its physiology What makes neurons different from other cells? Neurons process and transmit electrical impulses Neuron’s cell membrane is electrically charged (interior is more negative) Neurons influence each other’s charge (‘communicate’) Soma or “cell body”: The cell body of a neuron, which contains the nucleus. Dendrite: A branched treelike structure attached to the soma of a neuron; receives information from the terminal button of other neurons Synapse: A junction between the terminal button of an axon and the membrane of another neuron. Axon: The long, thin cylindrical structure that conveys information from the soma of a neuron to its terminal button. Terminal button: The bud at the end of a branch of an axon; forms synapses with another neuron; sends information to that neuron. Neurotransmitter: A chemical that is released by a terminal button; has an excitatory or inhibitory effect on another neuron

How do neurons process and transmit electrical impulses? A. dendrites receive input from other neurons B. axon sends neural impulse to axon terminal C. a neurotransmitter (NT) is release and makes contact with another neuron (synapse) Soma or “cell body”: The cell body of a neuron, which contains the nucleus. Dendrite: A branched treelike structure attached to the soma of a neuron; receives information from the terminal button of other neurons Synapse: A junction between the terminal button of an axon and the membrane of another neuron. Axon: The long, thin cylindrical structure that conveys information from the soma of a neuron to its terminal button. Terminal button: The bud at the end of a branch of an axon; forms synapses with another neuron; sends information to that neuron. Neurotransmitter: A chemical that is released by a terminal button; has an excitatory or inhibitory effect on another neuron

Synapse Communication Steps NT is released from pre-synaptic neuron NT binds to receptors in post-synaptic neuron Opens Na+ channels Sodium rushes in (activation) If enough Na+ rushes in => depolarization (action potential) NT released by post-synaptic neuron Pre-synaptic neuron Presynaptic membrane: The membrane of a terminal button that lies adjacent to the postsynaptic membrane and through which the neurotransmitter is released. Synaptic cleft: The space between the presynaptic membrane and the postsynaptic membrane. Synaptic vesicle: A small, hollow, beadlike structure found in the terminal buttons; contains molecules of a neurotransmitter. Postsynaptic receptor: A receptor molecule in the postsynaptic membrane of a synapse that contains a binding site for a neurotransmitter. Neurotransmitter-dependent ion channel: An ion channel that opens when a molecule of a neurotransmitter binds with a postsynaptic receptor Excitatory postsynaptic potential (EPSP): An excitatory depolarization of the postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by the terminal button. Inhibitory postsynaptic potential (IPSP): An inhibitory hyperpolarization of the postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by the terminal button. Neuromodulator: A naturally secreted substance that acts like a neurotransmitter except that it is not restricted to the synaptic cleft but diffuses through the extracellular fluid. Post-synaptic neuron

Other important facts Various Neurotransmitters (NT): Dopamine Adrenaline Serotonin Acetylcholine For each NT,various receptors - nicotine & muscarine Drugs can act by - modifying amount of NT, or - binding to receptor (nicotine) The net effect on neuron could be: - activation (action potential) - inhibition

Cells of the Nervous System Glia (Greek=glue) Many types (oligodendrocites, schwann cells, astrocytes, and microglia) More prevalent than neurons (10:1)

Complexity of CNS 1011 (100 billion) neurons each neuron interacts with 1,000 -7000 others => 100 -500 trillion connections (that’s a big #) Many other factors: Neurotransmitters Receptors Genes, Glial cells etc.

Glial Cells Functions: support, immunology (defense), nutrition for neurons, guide migration of neurons during development, maintain ion balance, etc. Form myelin which helps the speed of the action potential. In Multiple Sclerosis, the myelin is broken down and axons become less efficient. Myelin sheath: A sheath that surrounds axons and insulates them, preventing messages from spreading between adjacent axons. Node of Ranvier: A naked portion of a myelinated axon, between adjacent oligodendroglia or Schwann cells.

Copyright © Allyn & Bacon 2004

Copyright © Allyn & Bacon 2004

Blood-brain barrier Basal ganglia lesion (hiperdensities) due to increased bilirubin in newborn (kernicterus) Movement disorder Blood-brain barrier: A semipermeable barrier between the blood and the brain produced by cells in the walls of the brain’s capillaries. Area postrema: A region of the medulla where the blood-brain barrier is weak; poisons can be detected there and can initiate vomiting

Spared images

Figure 3.3 The Nervous System

Figure 3.24 Spinal Column, Ventral View

Vertebra of Spinal column Here is where spinal cord lives. Nerves leave spinal cord from between vertebrae (thus if discus moves, or pinch) there is pain (similar to facia paralysis following inflamation of facial nerve, or oppression of optic nerve by pituitary tumor).

Figure 3.26: Spinal Cord Cross Section

Figure 3.25 The Spinal Cord