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Chapter 37
Nervous System
Nervous System-receives and relays information about activities within the body and monitors and
responds to internal and external changes
http://www.biologymad.com/nervoussystem/nervoussystemintro.htm
Three main functions of the nervous system
• 1. Sensory Input
• 2. Integration
• 3. Motor Output
Three main functions of the nervous system
http://cafe.daum.net/beautyskinbody/GY8n/196?docid=16FM2%7CGY8n%7C196%7C20080718134405
Structures of the central Nervous system (CNS)
• 1. brain
• 2. spinal nerve cord
in vertebrates
http://factsabouthumanbodyanditsorgans.blogspot.com/2011/11/central-nervous-system.html
Motor output is the conduction of signals from the CNS to the effector
cells such as muscles
http://mycozynook.com/102RGCh28OH.htm
How are signals conducted
• Signals are conducted by nerves
• Nerves are bundles of neurons which are wrapped in connective tissue
Sensory and motor neurons are collectively called the peripheral
nervous system
http://generalknowledgeupdates.blogspot.com/2012/10/peripheral-nervous-system.html
Neuron-structural and functional unit of the nervous system
http://www.enchantedlearning.com/subjects/anatomy/brain/Neuron.shtml
Four main parts of a neuron
• 1. Cell body
• 2. Dendrites
• 3. Axon (action potential is generated here number 20)
• 4. Axon terminals
Neuron
http://www.enchantedlearning.com/subjects/anatomy/brain/Neuron.shtml
Synapse-The site of contact between a synaptic terminal of a neuron and a target, such as another
neuron, a muscle cell, or a gland, is called a
http://scienceblogs.com/purepedantry/2007/03/06/neuron-to-glia-synapse-on-axon/
Pre-synaptic cell and post-synaptic cells of a synapse
http://www.nature.com/nature/journal/v423/n6943/fig_tab/423931a_F1.html
Reflex arc-the simplest type of nerve circuit
http://www.docstoc.com/docs/115358232/Reflex-Arc-Reflex-Arc
Has to be at least one sensory neuron and one motor neuron
Ganglia and nuclei
• Collections of cell bodies of neurons.
• Ganglia are found in the peripheral nervous system
• Nuclei are found within the brain.
Schwann Cells
• Cells that form the insulating sheaths around axons
• Located outside the Central Nervous System
• It is made of myelin
http://207.204.17.60/schwann-cell-transplants-human-clinical-trials
Membrane potential• All cells have an electrical charge difference
across their plasma membrane called the membrane potential
• It exists because the different concentration of certain ions across the cell membrane
• The membrane potential of an unstimulated neuron is called the resting membrane potential
• These ions move across the membrane either by being pumped by membrane proteins or by simple diffusion through ion channels.
Membrane potential
http://en.wikipedia.org/wiki/Membrane_potential
Resting membrane potential
http://humanbiologylab.pbworks.com/w/page/45302491/Resting%20Cellular%20Membrane%20Potential
• All cells have a membrane potential
• However, only certain cells such as neurons and muscle cells have the ability to generate large changes in their membrane potential
• These cells are called excitable
Action Potential
• If a sufficiently strong stimulus causes depolarization to reach “threshold potential” it triggers a different type of response called an action potential
http://www.answers.com/topic/action-potential
Two factors that affect the speed at which an action potential travels
down an axon • The diameter of the axon, the larger the
diameter the faster the action potential
• The presence of myelin around the axon, myelin insulates the axon and allows the action potential to travel quicker
The “motor division” of the peripheral nervous system is divided into two functional divisions, called the somatic and
autonomic nervous systems
http://ultramindtechniques.blogspot.com/2011/04/know-hardware-iii-nervous-system.html
What do they do?
• The somatic nervous system carries signals to skeletal muscle
• The autonomic nervous system carries signals to cardiac muscle, smooth muscle, and glands
http://www.docstoc.com/docs/105365259/Comparison-of-Somatic-and-Autonomic-Systems
Sympathetic and Parasympathetic of the Autonomic nervous system
• The autonomic nervous system consists of two divisions that act on body organs with opposite affects
• The Sympathetic Division correlates with an activation of the fight or flight response
• The Parasympathetic Division causes a calming effect and a return to an emphasis on self-maintenance functions
http://emsbasics.com/2011/03/31/drug-families-stimulants-and-depressants/sympathetic-parasympathetic/