5.3 - Neuronal Communication Flashcards
What is the role of a neuron?
Transmit electrical impulses
Describe the structure and function of the cell body
- Contains nucleus surrounded by cytoplasm
- Lots of endoplasmic reticulum and mitochondria for production of neurotransmitters.
What is the function of the dendrites?
Responsible for transmitting electrical impulses towards cell body
Describe the structure and function of the axon
- Single elongated nerve fibre
- Transmit impulses away from cell body
What is the role of the myelin sheath?
Insulates the nerve.
Allows electrical impulses to travel faster.
What is the myelin sheath made of?
Schwann cells
Outline the pathway of most nervous responses
receptor → sensory neurone → relay neurone → motor neurone → effector
Describe the function of a sensory neurone
Transmit impulses from sensory receptor to relay neurone, motor neurone or brain
Describe the function of a relay neurone
Transmit impulses between sensory and motor neurones
Describe the function of a motor neurone
Transmit impulses from relay neurone to an effector (e.g. muscle, gland)
Outline differences between sensory and motor neurone
Sensory neurons have the cell body in the middle of neurone, but motor neurons have the cell body at end of neurone.
Sensory neurons have shorter axons, motor neurons have longer axons.
Sensory neurons have cell body in peripheral nervous system, but motor neurons have cell body in central nervous system.
What are sensory receptors?
- Specialised cells
- Detect changes in environment
- Specific to a single type of stimulus
- Often located in sense organs e.g. ear, eye
Define transducer
Something that converts one form of energy to another
How do sensory receptors act as a transducer?
Converts stimulus (e.g. chemical energy) into a nerve impulse (generator potential)
What does the Pacinian corpuscle detect?
Change in pressure
Where are Pacinian corpuscles located?
In the skin and in joints
Describe the structure of the Pacinian corpuscle
- End of sensory neurone in centre
- Layers separated by layer of gel
- Stretch-mediated sodium ion channels in membrane of neurone
Explain how the Pacinian corpuscle converts mechanical pressure into a nerve impulse
- Pacinian corpuscle found within skin detects pressure
- Pressure changes shape of Pacinian corpuscle
- Stretch-mediated sodium channels in neuronal membrane stretch
- Channels widen
- Sodium ions diffuse into membrane
- Membrane is depolarised and generator potential created
- Generator potential creates an action potential
- Action potential transmitted along neurones to CNS
Define resting potential
- Electrical potential of a neurone relative to its surroundings when not stimulated
- -70mV
Describe and explain how the resting potential is established and how it is maintained
- Sodium-potassium pump uses ATP
- Actively transport 3 sodium ions out of cell and 2 potassium ions in
- K+ ions also diffuse freely back out of cell
- Voltage-gated Na+ channels closed
- Membrane less permeable to Na+ so fewer Na+ diffuse back in