Unit A Part 1: Nervous System Flashcards
3 nerve types from stimuli to response:
Sensory Neurone
Interneuron
Motor Neurone
PNS
Peripheral Neurvous System.
Includes all nerves not in the Brain or Spinal Cord.
All motor and sensory neurones.
Myelinated Neurones
CNS
Central Nervous System.
All nerves in brain and spinal cord.
Unmyelinated neurones.
Peripheral Nervous System nerve types:
Somatic Nerves: voluntary nerves (sensory/motor).
Autonomic Nerves: involuntary (Sympathetic [stress] and Parasympathetic [return from stress]).
Examples of Sympathetic and Parasympathetic nervous reactions:
- pupils (dilates->constricts)
- bronchioles (dilates->constricts)
- heartrate (increase->decrease)
- digestion (increase->stop epinephrine release)
The Reflex Arc:
- Receptor
- Sensory neurone
- Spinal cord interneuron
- Motor neurone
- Effector
Axon:
Extended arm of neurone that carries nerve impulse away from body.
Dendrites:
Smaller arms of neurones that receives a nerve impulse.
End plates:
Ends of axons that transmits signals to other neurones.
Neurilemma:
Delicate membrane that surrounds axon of PNS nerves. Promotes regeneration.
Schwann Cells:
A type of glial cell that produces myelin. Only on PNS neurones.
Myelin Sheath
An insulating covering over the axon of a neurone produced by Schwann Cells.
Node of Ranvier:
Gaps in the myelin sheath where action potentials are performed on myelinated neurones.
Why do neurones only send signals one way?
Because Dendrites can only receive signals and End plates can only send.
Synapse:
Gap between neurones (post and pre) where a chemical signal is sent. A neurotransmitter is sent to the other neurone into the synapse through an ion channel, which means the impulse is sent.
Action Potential:
Electrochemical impulse created by movement of jobs through the nerve cell membrane (signal is being sent).
Resting potential:
Step 1 of Action Potential:
Neurone is not sending a signal.
K+ is inside Neurone and more Na+ is outside, meaning neurone is negative.
Depolarization:
Step 2 of Action Potential.
Na+ gate is opened and Na+ diffuses across membrane into Neurone. Neurone is now net positive.
Repolarization:
Step 3 of Action Potential.
K+ gate opens and it diffuses out of neurone. Pump also turns on, forcing Na+ out and K+ in at a 3/1 ratio.
At some point it’s so effective that it negativity goes below normal, but soon returns (hyperpolarization).
Neurone returns to net negative.
Refractory Period:
Recovery time before a nerve can fire again.
Threshold:
Charge a Neurone must pass for it to fire (all or nothing).
Stimulus must be greater or equal to threshold.
Why are reflexes fast?
They are fast because the PNS, which is what most of reflexes travel through, are myelinated which allow signals to move faster.
Neurotransmitters:
Chemicals sent between neurones in synapse to cause change in postsynaptic membrane.
Two types of Neurotransmitters:
- Excitatory: open Na+ channels and bring membrane potential towards threshold (activates).
- Inhibitory: makes membrane more permeable to K+ and moves membrane potential further form threshold (deactivates).
Summation:
The sum of multiple excitatory potentials produced together may be enough to produce an Action Potential in the postsynaptic neurone if one is not.
Another word for sensory and motor nerves is:
Afferent and efferent.
