Nervous coordination Flashcards
What is a stimulus?
Any change in the external environment such as light or pressure
What is taxis?
When a whole organism moves towards (positive) or away from (negative) a stimulus
What is the function of the nervous system?
- Detection of stimuli by receptors.
- Transmission of nerve impulses by neurones.
- Response by effectors
What is the function of neurones and what types are there?
They carry electrical impulses from one part of the body to another. There are three types:
- Sensory
- Bipolar/Intermediate/Relay
- Motor
What is the order of a reflex arc?
- Receptor neurone
- Sensory neurone
- Bipolar neurone in spinal cord
- Motor neurone
- Effector
Explain the importance of reflex actions.
- Automatic/involuntary
- Reduces/avoids damage to tissues/prevents injury
- Role in homeostasis
- Posture/balance
- Finding food/mate/suitable conditions
- Escaping from predators
What’s the function of dendrites?
They carry nerve impulses towards the body
What’s the function of the neurone cell body?
It produces proteins and neurotransmitters.
What’s the function of the myelin sheath?
Its a lipid covering that insulates the axon, speeding up nerve impulses.
What’s the function of schwann cells?
They produce myelin
What’s the function of node of ranviers?
They are the gap between schwann cells / areas without a myelin sheath
What’s the function of the axon?
Carries nerve impulses away from the cell body.
What’s the function of terminal end branches?
They connect the neurone to the effector
What happens to neurones as they age?
They lose dendrites and synapses.
What is multiple sclerosis?
It is an autoimmune disease where your body attacks the myelin sheath in the brain and/or spinal cord.
Inflammation and scarring can disrupt the messages travelling along the nerves.
What causes nerve impulses?
They are caused by electrochemical signals meaning chemicals cause an electrical signal. These chemicals are ions such as sodium ions.
What are the 4 basic steps of generating a nerve impulse?
- Resting potential
- Depolarisation
- Repolarisation
- Resting potential
What happens during resting potential?
K+ gates closed
Na+ gates closed
K+ channel permanently open
What happens just before depolarisation?
K+ gates closed
Some Na+ gates open, Na+ diffuses in and Na+ diffuses in, triggering the reversal of potential difference across the membrane
K+ channel permanently open
What happens during depolarisation?
K+ gates closed
Most Na+ gates open and cause an influx of Na+ diffusing into the axon
K+ channel permanently open
What happens at the action potential?
K+ gates closed
After action potential is reached, Na+ gates close
K+ channel permanently open
What happens at repolarisation?
K+ gates open, the gradient preventing further movement of K+ is reversed. More K+ diffuse out.
Na+ gates closed
K+ channel permanently open
What happens in hyperpolarisation?
The diffusion pf K+ causes a temporary overshoot of the gradient inside the axon, making it more negative than the outside.
K+ gates closed
Na+ gates closed
K+ channel permanently open and restores resting potential
How does myelination effect the speed of action potentials?
The myelin sheath is an electrical insulator.
In a myelinated neurone, depolarisation can only happen at the nodes of Ranvier where sodium ions can get through the membrane.
