Download An introduction to the Nervous system

An introduction to the Nervous
system
From: http://www.hiogolffitness.com/?p=262
The importance of the nervous system
• Nervous systems reponse to stimuli
(external or internal) by controling the
actions of the body through
electrochemical messages
• Allows us to: detect light, odour,
temperature or pressure… just to name a
few
What is the nervous system?
• Elaborate communication system (>100 billion
nerve cells in the brain alone!)
• 2 main divisions (flow chart, p412):
– central nervous system (CNS)
• Brain and spinal cord
• Coordinating system
– peripheral nervous system (PNS)
• Nerves that carry info between organs and CNS
• Subdivided into somatic (skeletal muscle, bones
and skin- relays info about environment) and
autonomic (internal organs like the heart)
Anatomy of a nerve cell
• 2 types of cells
– Glial: non-conducting cells important for
structural support and metabolism
– Neurons: functional units of the nervous
system
• Can be sensory- sense and relay info from the
environment to CNS for processing
(photoreceptors for light, chemoreceptors for
chemicals etc…) and are located in clusters called
ganglia
• Or motor – relay information to the effectors
(muscles, organs, glands)
• Or Interneurons – link neurons in the body
(integrate sensory and motor neurons)
Motor neuron
Sensory neuron
From:
http://www.dmacc.edu/instructors/rbwollaston/Chapter_8_Nervous_System.h
tm
From: http://www.daviddarling.info/encyclopedia/N/neuron.html
Parts of the neurons
• Dendrites: receive info from sensory receptors by
conducting nerve impulses toward the cell body
• Axon: projects nerve impulses from the cell body
• Myelin sheath: covers many axons, insulates the
neurons, preventing loss of charged ions from nerve cell.
Formed by special glial cells called schwann cells.
• Nodes of Ranvier: areas between sections of myelin
sheath, nerve impulses jump from one node to another
(speeding up process)… so nerve impulses are quicker
in mylelinated axons.
• Neurilemma: surrounds the axon and promotes regeneration of a damaged axon
Neural circuits
• Simplest nerve pathway is called a reflex
arc
• Occurs without brain coordination
• 5 components: receptor, sensory neuron,
interneuron, spinal cord, motor neuron and
effector.
From: http://www.biologie.uni-hamburg.de/b-online/library/cat-removed/u3aos22.html