What does the nervous system do?
Action Potentials- rapid transmission of messages
Reflex arc-simple somatic function and autonomic function
Sensory input- brings information in
Processing information- brain and spinal cord
Motor output- initiates responsemuscles- movement glands- secretion
Action Potentials:
*ability to sense environment, processing information rapidly and resonce requires rapid transmission of messages within the body
*ability to transmit messages rapidly unique to animals
*accomplished by cell membrane changes called action potentials
*happens in nervous tissue cells called neurons and in cell muscle
Neurons:
*main cells of nervous system
*transmit rapid messages-action potentials
*axon carries messages
*dendrite connect to other cells, usually neurons or muscle cells
*cell body contains nucleus, maintain cell function
*single neurons nerver die or divide after initial nervous system development
Myelin Sheath:
*single nerve contains hundreds or thousands of axons, each axon surrounded by sheath
*myelin is fat based insulated substance that isolates neurons and helps speed of action potential propagation
*myelin is contained with in cells that wrap around axon called schwann cells
Types of neurons:
sensory- bundled in nerves bring information in from virtually every tissue, structure,a dn organ of the body except brain and spinal cord
motor- bundled in nerves, to every muscle and gland including blood vessels.
How do neurons carry messages?
Action potentials- unique to animal nerve and muscle tissue, ability to rapidly carry an ion diffusion mediated change voltage along cell membrane, only neurons and muscle cells can do it.
What happens when action potential arrives at end of axon?
neurotransmitter is secreted to stimulate connecting neurons or muscle cells
Autonomic function- spinal cord reflex example voluntary or somatin funtion
most visceral organs , digestive system, glands, blood flow heart and blood vessels have autonomic involuntary control same principles and action potential control is sub concious
sympathetic-speed up innervation
parasypathetic- slow down response
How does sensation happen? sensory receptors respond to stimulus from body or environment
These receptor cells trigger action potentials in connecting sensory neurons
spinal cord and brain interpret and analyze info.
sensory cortex maps touch sensation from entire skin surface
cutaneous receptors of skin bring touch pressure, pain, heat and cold
Proprioception- gives body position by sending muscle tension (allows you to touch your nose with your eyes closed)
special senses is head- taste, smell, vision, hearing, equilibrium
Cool Facts:
Average number of neurons in a human brain 100 billion
octopus brain-300 billion
rate of neuron growth during fetal development 250,000 neuron/min
longest axon of neuron around 15 feet giraffe primary afferent axon from toe to neck
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