Chapter 13 - The Nervous System. Flashcards
What are the 2 main parts of the nervous system?
- CNS, brain and spinal cord.
- PNS, somatic and autonomic nervous system.
What is a stimulus and what does it produce?
It is a detectable change in the internal/external environment of an organism that produces a response.
What are the elements of a reflex arc?
- Stimulus.
- Receptor.
- Sensory neurones.
- Relay neurone in CNS.
- Motor neurone.
- Effector.
- Response.
What are the 3 types of neurone?
- Sensory.
- Motor.
- Relay.
What is happening when the axon membrane is at resting potential and what value is this?
Sodium and potassium gated channels are closed and the Sodium Potassium co-transporter protein is actively transporting sodium out and Potassium in. Some K+ channels are open so some K+ diffuses back out. The resting potential is -70mV.
How is an action potential initiated?
By depolarising the membrane. The energy of the stimulus causes the voltage gated sodium channels to open allowing to rapidly diffuse into the axon, down their concentration gradient. Axon becomes 40mV.
What happens after the axon is depolarised?
Its repolarised. The sodium channels close and the Potassium voltage gated channels open and Potassium diffuse down their concentration gradient. However, more diffuse out than Na+ diffused in which makes the membrane hyperpolarised.
How is the axon membrane restored to resting potential after hyperpolarisation?
The potassium channels close, the sodium-potassium pump pump K+ ions back in and Na+ ions back out, restoring the ion balance.
How does the action potential travel along an axon?
As Na+ ions move laterally through the axon, they depolarise the adjacent section of the membrane, opening more voltage gated channels.
What is the absolute refractory period and what does it ensure?
It is the period during which no new action potential may be initiated. It prevents the action potential being propagated back in the direction from which it came.
What is the all or nothing law?
Where a nervous impulse is either initiated or not and its always the same size. It prevents minor stimuli from setting up nervous impulses, so the brain isn’t overloaded with information.
How does the brain detect how strong a stimulus is all the action potentials are the same size?
Due to the frequency of them.
What factors affect the speed of conduction of the nerve impulse?
- Temperature.
- The diameter of the axon.
- Myelination.
What is saltatory conduction?
Transmission of a nerve impulse along a mylelinated axon, in which the action potential jumps from one node of ranvier to the adjacent node.
In a chemical synapse, what is the impulse transmitted by?
Neurotransmitter.
