John Clappin

Three Qualities

1. Monitors internal & external environments
2. Integrates sensory information
3. coordinates voluntary and involuntary responses of many other organ systems

Central Nervous System (CNS)

• Brain & Spinal Cord

Peripheral Nervous System (PNS) Central (Nerves and Ganglia)

• Sensory- Afferent
  • Exteroreceptors (Touch, Temp, Pressure, Smell, etc)
  • Proprioreceptors (Position and movement of skeletal muscles)
  • Interoreceptors – (monitor digestive, respiratory, cardiovascular, urinary and reproductive systems and taste)
  • Peripheral ganglions
• Processing – Interneuron, then on to the;
  • Somatic motor neurons – skeletal muscles
  • Visceral motor neurons – smooth muscle, glands, cardiac muscles, fat cells
• Motor – Efferent
  • Voluntary – Somatic
  • Involuntary – Autonomic
    • Sympathetic
    • Parasympathetic

Types of Nervous Tissues

• Neurons – basic unit of the nervous system (do not reproduce)
  • Dendrites – afferent – inbound
  • Cell Body
  • Axon Hillock (delta shaped as cell body becomes an axon)
  • Axon – Efferent
  • Axon Collaterals (off side of axons)(branches to different portions of muscles)
  • Axon Terminals
  • Synaptic End Bulbs (Neuromuscular terminal)
  • Synaptic Cleft
  • Dendrite of next neuron or effector organ
• Types of Neurons
  • Multipolar – most common in CNS
  • Unipolar – most sensory neurons of PNS
  • Bipolar – rare in special sense organs (sight smell, hearing)
• 

Saltatory Conduction ( impulses pause at breaks in myelin, draws in sodium)

Neuron

 

• Neuroglia – neuro glial cells – regulate the environment around the neurons providing support for neural tissue (do reproduce)
  • Ependymal Cells -secrete CSF
  • Astrocyte – largest and most numerous, secretes chemicals vital to maintain the blood-bran barrier which isolates CNS from general circulation.
  • Oligodendrocytes – secrete myelin to neural axons (myelin – makes them white, permits and controls movement of ions don the axon and does not go into surrounding tissues – insulation). Some cells are myelinated and some are unmyelinated. Multiple Sclerosis is a degenerative disease affecting myelin production.
  • Schwann Cell – PNS cell similar to Oligodendrocytes  – covers every axon in the PNS
  • Everything white is myelin. Everything gray is accumulated cells.

Neural Communication

• Chemical Neurotransmitters – information transfer at synaptic terminals occur via the release of neurotransmitters.
  • Norepinephrin (primary sympathetic neurotransmitter)
  • ACh (primary parasympathetic neurotransmitter) (AChE breaks it down in the cleft to allow the receptors to open for the next transmission)
  • Dopamine
  • GABA
  • Serotonin
  • Melatonin
  • etc,

Synaptic Cleft

Nerves

Cell bodies are frequently grouped together;

• In CNS – called Nuclei, Nucleus
• Outside CNS – called Ganglion,Ganglia
• Fascicle – groups of neurons bundled together, surrounded by connective tissue. Nerves contains multiple bundles of fascicles(outside CNS, inside CNS called Tracts)

Anatomy of the Spinal Cord

• Starts at Foramen Magnum – runs down to L1
• Cervical region is thicker, called cervical enlargement – same at bottom, called lumbar enlargement
• Conus medullaris – cone like end of SC
• Cuada Equina – after spinal cord ends – threadlike (spinal taps, epidurals, etc. happen here)
• 32 spinal nerves – beneath each of the vertebrae
• Nerves from spinal cord contain both efferent and afferent neurons – split just before spinal cord – dorsal roots(sensory – with dorsal ganglia) and ventral roots (purely motor – cell bodies in are in the spinal cord)
• Grey Horns (anterior and posterior)
• Anterior and Posterior White Columns (contain tracts) (posterior – ascending tracts, anterior – descending tracts)
• Central canal – contains CSF
• Meninges
  • Pia Mater – first protective layer of spinal cord (very tightly wrapped)
  • Subarachnoid space – between pia mater and arachnoid layer – filled with CSF
  • Arachnoid layer – looks like a spider’s web
  • Spinal dura mater
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The Brain

• cerebral cortex -is a structure within the brain that plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness.
• cerebrum
  • divided into cerebral hemispheres
• diencephelon
  • Hollow, largest portion is the thalamus – which contains relay and processing for sensory information. Hypothalamus is connected to the pituitary gland. The hypothalamus contains centers involved with emotions,autonomic function and hormone production. The pituitary gland is the prmary link between the nervous and endocrine systems.
• Brain Stem (responsible for all vegetative function and almost all cranial nerves originate here)
  • midbrain – process visual and auditory information and generate involuntary responses. also has regions that help maintain consciousness.
  • pons – or bridge, connects cerebellum to brain stem. also contains tracts involved in visceral and somatic control. Also connected to the medulla oblongata
  • medulla oblongata – segment of brain attached to the spinal cord. relays information to the thalamus and other parts. regulates lots of autonomic function including heart rate,BP, respiration and digestion.
• cerebellum – adjust voluntary and involuntary motor activities based on sensory information and stored memory of previous movements.
• Ventricles – 1st through 4th – chambers filled with CSF
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The Peripheral Nervous System (PNS)

• 12 Pairs of Cranial Nerves (future post – see table 8-2 on page 297)
• Nerve Plexus – PNS network of intersecting nerves
  • Cervical plexus – serves the head, neck and shoulders
  • Brachial plexus – serves the chest, shoulders, arms and hands
  • Lumbar plexus – serves the back, abdomen, groin, thighs, knees, and calves
  • Sacral plexus – serves the pelvis, buttocks, genitals, thighs, calves, and feet
  • Solar plexus – serves internal organs
  • Coccygeal plexus – Same as Solar Plexus

    Since the Lumbar and Sacral plexus are interconnected, they are sometimes referred to as the Lumbosacral plexus. The nerves that serve the chest are the only ones that do not originate from a plexus

• Dermatomes
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