Section 6: Chapter 15: Nervous Coordination and Muscles Flashcards
What are 5 key features of the hormonal / endocrine system?
- Communication via chemicals called hormones.
- Transmission via blood flow.
- Slow.
- Widespread response.
- Long-lasting.
What are 5 key features of the nervous system?
- Communication via nerve impulses.
- Transmission by neurones.
- Fast.
- Localised response.
- Short-lived / temporary.
What is the role of a neurone?
To carry nerve impulses around the body.
What is the main difference between the structure of a motor and sensory neurone?
Motor neurone has a cell body on the end of it’s axon, sensory neurone’s cell body is in the middle of the axon.
What are Schwann cells? (in neurones)
- Surrounds the axon.
- Provides electrical insulation.
- Involved in nerve regeneration.
What is the myelin sheath? (in neurones)
- Covers axon.
- Rich in the lipid myelin.
- Increases speed on action potential.
What is the node of Ranvier? (in neurones)
- Gaps between myelin sheath.
- Increases speed of action potential.
What are dendrons and dendrites? (in neurones)
Small branches that carry nerve impulses to the body.
What is a resting potential?
- Charge of a resting axon. -70mV because more positive ions are actively transported out than in (3 NA+ out, 3 K+ in).
What is the charge of a resting potential?
-70mV.
Why is a resting potential negative?
More positive ions actively transported out than in.
3 Na+ out, 3 K+ in.
How are the movements of ions across an axon membrane controlled?
1) Phospholipid bilayer - NA+ and K+ ions can’t diffuse across.
2) Channel proteins - some always open, some have gates (eg/ voltage).
3) Sodium-potassium pump - active transport.
Where do sodium ions go when they are actively transported out of an axon?
Surrounded tissue fluid.
During a resting potential, is an axon polarised or depolarised?
Polarised.
What causes an action potential?
Stimulus detected by a receptor, causing a temporary reversal of charge.
What is the charge of an action potential?
+40mV.
During an action potential, is an axon polarised or depolarised?
Depolarised.
Draw out the graph of an action potential?
https://www.moleculardevices.com/applications/patch-clamp-electrophysiology/what-action-potential#gref
Label a graph of an action potential with 6 key words.
Polarised. Threshold. Depolarised. Repolarised. Hyperpolarised. Resting potential.
Describe the process of an action potential.
1) Resting potential -70mV.
2) Once impulse reaches threshold, some Na+ VG channels open. Na+ move in down chemiosmotic gradient.
3) Na+ enters until action potential / depolarisation has happened (+40mV).
4) Na+ VG channels shut. K+ VG channels open - K+ leave down chemiosmotic gradient.
5) Repolarisation - K+ leaving.
6) Hyperpolarisation - more negative than resting potential.
7) Resting potential reestablished using Na+/K+ pump and leak channels.
Does an action potential travel faster in a myelinated to an unmylinated axon? why?
Myelinated because action potential jumps along nodes of Ranvier (saltatory conduction).
What is saltatory conduction? (action potential)
Action potential can jump along nodes of Ranvier in a myelinated axon. Faster.
What 3 factors affect the speed of an action potential?
1) Myelin sheath - increases speed due to saltatory conduction.
2) Axon diameter - Increased diameter = increased speed.
3) Temperature - increased temp = increased speed because increased ion diffusion.
What is the all or nothing principle? (action potential)
Stimulus has to reach threshold to cause action potential.
Threshold not reached = nothing.
