2.3: Overview of the Nervous System and the Neuron Flashcards
What is the Nervous System Made Up of?
Central Nervous System (CNS) and Peripheral Nervous System (PNS).
Central Nervous System (CNS)
Composed of just the brain and spinal cord.
Reflex
An automatic response often created by a signal neural pathway in our spinal cord.
Reflexes are so quick and automatic because the message is received and responded to before our brain even has time to respond.
The interneurons in the spinal cord enable this reflexive response.
Peripheral Nervous System (PNS)
Can be broken down further into the autonomic and somatic systems: Somatic Nervous System & Autonomic Nervous System.
Somatic Nervous system
In charge of controlling voluntary movements of our skeletal muscles - like covering your eye during an eye exam at the doctor.
Autonomic Nervous System
Controls all automatic functions of our internal organs - like your heart beating and your lungs breathing.
The automatic nervous system comes into play especially in fight-or-flight responses. It can increase your heart rate or blood pressure in such situations.
What Can The Autonomic Nervous System Break Down Further Into?
Two other systems: Sympathetic Nervous System and Parasympathetic Nervous System.
Sympathetic Nervous System
Our arousal system.
When you get nervous before an exam your heart may race, and your breathing may become more rapid - this is thanks to the autonomic nervous system, which prepares us for action.
“Fight or Flight.”
Parasympathetic Nervous System
Returns us to a calm and neutral state once the stimuli that triggered our original arousal has subsided.
“Rest and Digest.”
Sensory Neurons/Afferent Neurons
What carry incoming sensory information into the brain and spinal cord (CNS).
Interneurons
Where the sensory information is then processed in the brain and spinal cord.
Motor Neurons/Efferent Neurons
A message or response is carried back out through our motor in our muscles and glands.
How do signals occur? How does our brain know what to do?
Basically, action potential must occur for a message to continue to travel down the axon of a neuron, which is the messenger. This only occurs if the neuron’s threshold has been met - meaning it has received enough stimulation from the original sending neuron. If this threshold is met, the action potential occurs and the message travels down the axon via a process of depolarization. If the threshold is not met, nothing happens. Neurons have an all-or-none response.
