PCOL-Chapter 6

• Two anatomical subdivisions of the brain

  Central Nervous System

  Peripheral Nervous System
• contains brain and

  spinal cord

  Central Nervous System
• contains neuronal

  tissues outside the CNS

  Peripheral Nervous System
• Two major subdivisions of the brain:

  Autonomic Nervous System

  Somatic Nervous System
• Sympathetic division prepares body to respond to stressors (fight or flight response)
• Controls involuntary functions such as heart rate, digestion, breathing, blood pressure, etc.
• The somatic nervous system controls voluntary movements, such as walking, talking, and writing.
• Parasympathetic division restores homeostasis when stress is over.
• The autonomic nervous system regulates involuntary functions like heart rate, digestion, breathing, and blood pressure.
• Controls voluntary movements of skeletal muscles
• Parasympathetic division restores homeostasis when stressor is removed
• overseec activities that are not under direct conscious control such as functions like cardiac output, blood flow distribution,

  and digestion

  Autonomic Nervous System
• branch largely concerned with activities under direct conscious control such as movement, respiration, and posture.

  Somatic Nervous System
• Common properties shared by the nervous

  system and the endocrine system:

  ° High-level integration in the brain

  ○ Influence processes in distant regions of

  the body

  ○ Extensive use of negative feedback
• Both organ systems utilize chemicals in

  transmitting information, the nervous system

  additionally uses electrical signaling. In the

  nervous system, chemical signaling is either

  between nerve cells or nerve cells and their

  effector cells. The released neurotransmitters

  travel from the terminals to the cleft by

  diffusion. The transmitter may either activate or

  inhibit the postsynaptic cell upon binding to its

  receptor.

  nervous system and the endocrine system
• yields a modified

  subsequent activity, when transmission occurs

  from postsynaptic cell to presynaptic neuron

  terminal

  Retrograde transmission
• The ANS is further subdivided into two major

  portions with motor neurons both originating in

  nuclei within the CNS branching out into

  preganglionic efferent fibers that exit from the

  brain stem/spinal cord terminating in motor

  ganglia. These two are:

  Sympathetic (Thoracolumbar)

  Parasympathetic (Craniosacral)
• Preganglionic fibers leaving the CNs

  through the thoracic, lumbar, and (acc.

  To new info) sacral spinal nerves

  Sympathetic (Thoracolumbar)
• preganglionic fibers leaving through the

  cranial nerves (especially III, VII, IX, and

  X)

  Parasympathetic (Craniosacral)
• The

  predominant neurotransmitter for

  parasympathetic is

  acetylcholine
• predominant neurotransmitter for sympathetic is

  norepinephrine
• some sympathetic fibers such as those

  innervating the sweat glands release

  acetylcholine rather than norepinephrine.
• During stress, the sympathetic nerve innervating

  the renal vasculature and kidneys may release


  dopamine and norepinephrine.
• releases norepinephrine and epinephrine

  directly into the bloodstream.

  adrenal medulla
• are innervated by sacral

  preganglionic nerves, ontogenetically similar to

  sympathetic preganglionic fibers.

  Pelvic ganglia
• Considered as a third division of the ANS, consisting of a large and highly organized collection of neurons innervating the walls of the GI system.

  ENTERIC NERVOUS SYSTEM
• Covers both motor and secretory activities of the

  gut, particularly the motor activity of the colon.

  ENTERIC NERVOUS SYSTEM
• Both plexuses receive preganglionic

  parasympathetic fibers and postganglionic

  sympathetic axons, as well as sensory input in

  the wall of the gut.

  Myenteric plexus (Plexus of Auerbach) -

  Submucous plexus (Plexus of Meissner)
• epithelial cells in the mucosa

  synapse with vagal and sensory fibers to send

  information regarding gut chemical contents to

  the CNS.

  Enteroendocrine
• rapid transmission

  Glutamate
• slower, longer-lasting

  transmission

  Cholecystokinin
• Deprivation of input from both ANS divisions

  does not abolish what activity?

  GI activity
• selective denervation may even result in greatly enhanced in?

  motor activity
• have nerve terminals that

  end with small boutons close to the tissue

  innervated resulting in rapid diffusion path (effect

  is rapid and localized).

  Classic synapses