Ch 48-49 Nervous System Flashcards
Neurons
Nerve cells
Where do neurons receive signals?
Their dendrites
What structure do signals received by neurons travel down?
The axon
This allows for rapid communication
Afferent nerves (sensory nerves)
Carry signals to the brain or central nervous system
Efferent nerves (motor nerves)
Carry signals out from the central nervous system
Resting membrane potential (-70 mV)
When a nerve is at rest it has a negative charge internally and positive charge externally
Action potential
An electrical signal that moves along the axon
What causes depolarization?
A stimulus at the dendrite end of the cell opening sodium channels
Depolarization
A change in the direction of the membrane potential
What does depolarization trigger?
Repolarization
Repolarization
Potassium ion movement out of the neuron
What does repolarization trigger?
Depolarization of the adjacent region
Why is an action potential considered an “all or nothing” response?
All action potentials are identical and, once triggered, go to completion
Synapses
Transmit action potentials between nerve cells
Neurotransmitters
Communicate transmission across synapses (electrical or chemical)
What is triggered when one neurotransmitter is released by one nerve?
The opening of ion channels on the next nerve
If enough channels open, the nerve will depolarize and pass along its own action potential
Central nervous system (CNS)
Possessed by bilateral animals
The central nervous system (CNS) communicates with what?
A peripheral nervous system (PNS)
Reflex arc
A response acting through a sensory nerve and a motor nerve in the central nervous system (CNS)
Autonomic nervous system
Governs involuntary body functions
Do sympathetic and parasympathetic nerves have opposite or equal reactions?
Opposite
Sensory pathways have four functions in common
1) Reception
2) Transduction
3) Transmission
4) Perception
Reception
Sensory receptors interact directly with stimuli, both inside and outside the body
Sensory transduction (transduction)
The conversion of stimulus energy into receptor potential
Receptor potential
A change in the membrane potential of a sensory receptor
What does it mean that receptor potentials are “graded” potentials?
Their magnitude varies with the strength of the stimulus
What occurs after energy has been transduced into a receptior potential?
Some sensory cells generate the transmission of action potentials to the central nervous system (CNS)
Are all action potentials equal signals?
Yes
What is encoded by the frequency of action potentials?
Information about the strength of the sensory stimulation
Perceptions
The presentations of stimuli constructed in the brain
How does the brain distinguish stimuli from different receptors?
The area of the brain where the action potential arrives tells the brain this information
What can affect perception?
The amplification of and the adaptation to stimuli from receptors
