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/