The nervous system controls and coordinates functions throughout the body and responds to internal and external stimuli
Impulses are electrical signals that carry messages through the nervous system
Neurons are nerve cells that transport impulses
Neurons are classified according to the direction in which an impulse travels
Slide 2
Types of Neurons
Sensory Neurons:They carry impulses from the sense organs to the spinal cord and brain
Motor Neurons:They carry impulses from the brain and spinal cord to muscles and glands
Slide 3
Types of Neurons Cont.
Interneurons:Connect sensory and motor neurons and carry impulses between them
Dendrites: extending from the cell body, they carry impulses from the environment to the cell bodyAxon: long fiber that carries impulses away from the body, they end with the axon terminalMyelin Sheath: insulating membrane that surrounds the axonSchwan Cells: wrap around the axon
Slide 5
Saltatory Conduction
Saltatory Conduction: Impulses "Jump" from one node to the nextThis process speeds the transition of the impulse along the neuron
Outside of the resting neuron is a net positive charge
Inside the Neuron is a net negative charge
Resting potential:Difference in electrical charge across the cell membrane of a neuron at rest It's maintained by the sodium potassium pump (Na + K)
Slide 7
Action Potential
The action potential (aka nerve impulse) is the reversal or charge along a nerve cell membrane An impulse begins when a neuron stimulates another neuron or the enviornment
There is a reversal of changes, also known as the Action potential.As it passes, the negative charge is restored, and returns to the resting potential.The inside of the neuron temporarily becomes more positive then the outside
Slide 9
Threshold
The strength of an impulse is always the same
Either there is an impulse, or their is not
The minimum level of a stimulus that is required to activate a neuron is called the threshold
Any stimulus stronger than the threshold will produce an impulse
It is a ALL OR NONE principle
Slide 10
Synapse
The Synapse is the location when a neuron transfers an impulse to another cell
Synaptic Cleft: Space between the axon terminal of one neuron and the dendrites of an adjacent cell
Neurotransmitters: chemicals that are contained in vesicles at axon terminals
They are used to transmit the impulse across a synapse
As the two meet, the neurotransmitters are diffused across into the synaptic cleft to send the message
Sodium ions rush across the membrane, stimulating the next cell
Slide 11
Synapse: Simple Overview
1. Impulse is sent across the neuron: called the action potential (aka nerve impulse)
2. Ends at the axon terminal, where it will meet at the next neurons dendrites
3. When they meet, a chemical is released called neurotransmitters that sends the message from the axon to the dendrite
4. Sodium ions rush across the membrane, and will stimulate the next cell
5. If this stimulation exceeds the threshold, a new impulse will begin until the message is sent6. After all of this, the neurotransmitters are broken down by enzymes or recycled
Slide 12
Organization of the Nervous System
Central Nervous System
relays message, process info, and analyzes information
consists of the Brain and Spinal Cord
The Brain: has meninges, a layer that surrounds the brain and spinal cord
In-between the brain and the meninges is cerebrospinal fluid, which fills the space and acts as a shock absorber
Slide 13
Somatic Nervous System (Part of PNS)
Regulates actions under conscious control
Some are involved with reflexes, like quick automatic responses to stimulus
Reflex Arc: include sensory receptors - sensory neuron - interneuron - motor neuron - and effecter (all of which are involved in a quick response to stimulus
The effector is the muscle or organ that responds to the command of the nervous system
Slide 14
Autonomic Nervous System (Part of PNS)
Regulates involuntary activities
Subdivided into to parts: Sympathetic and Parasympathetic
Sympathetic: heart speeds up, digestive system slows down
Parasympathetic: slows down heart, speeds up digestive system
Both of these systems help maintain homeostasis
