Unit 5.3- Neuronal Communication Flashcards
(50 cards)
Motor neurones definition:
Neurones that carry an action potential from the CNS to effector
Relay neurones definition:
Join sensory and motor neurones
Sensory neurones definition:
Neurones that carry an action potential from the sensory receptor to CNS
Dendron/ dendrites definition:
The bit before the cell body that’s like the axon
Structure of neurones:
- Many are long
- Plasma membrane has many gated ion channels that control the entry or exit of sodium, potassium or calcium ions
- Sodium potassium pump actively transports sodium ions OUT of the cell and potassium ions INTO the cell
- Neurones maintain a potential difference across their plasma membrane
- The cell body contains the nucleus, and many mitochondria and ribosomes
- Neurone dendrites connect to other neurones and carry impules TOWARDS the cell body
- The axon carries imulses AWAY from the cell body
What is the myelin sheath made of?
Schwann cells
Lengths of dendron and axon in sensory neurone:
- Long dendron
- Cell body just outside of CNS
- Short axon
Lengths of dendron and axon in relay neurone:
- Many short denrites
- Short axon
Lengths of dendron and axon in motor neurone:
- Cell body inside CNS
- Long axon
Why do impulses travel faster in myelinated neurones?
- The myelin sheath is wrapped tightly around the neuron, preventing the movement of ions across the neurone membrane
- The movement of ions can only occur at the node of Ranvier
- This means the action potential jumps from one node to the next
Where are the Schwann cells in non-myelinated neurones?
Several neurones may be enshrouded in one loosely wrapped Schwann cell, meaning that the action potential moves in a wave
What are non -myelinated neurones often used in?
Coordinating body functions such as breathing and the action of the digestive system. They do not need to be so quick for this.
Pacinian corpuscle definition:
A pressure sensor found in the skin
Sensory receptors definition:
Cells/ sensory nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potentials
Structure of a Pacinian corpuscle:
- Oval shaped
- Series of concentric rings of connective tissue wrapped around the end of a nerve cell
What happens to the Pacinian corpuscle when there is pressure on the skin?
It deforms the rings of connective tissue, which push against the nerve ending. When pressure is constant, the corpuscle stops responding because the rings are not being deformed any more
What happens to sodium channels when the membrane of a nerve cell is deformed by changing pressure?
They open
What does the sodium/ potassium pump do on a nerve cell membrane
- Actively pump three sodium ions out of the cell for every two potassium ions actively pumped in
- This is when the channel proteins are closed and the neurone is at rest
Why do some potassium ions leak out of the nerve cell when it is at rest?
The membrane is more permeable to potassium ions
What is the negative charge inside nerve cells enhanced by?
The presence of negatively charged anions inside the cell
What is a nerve impulse created by?
- Altering the permeability of the nerve cell
- Sodium ion channels are opened and sodium ions rush in
- This creates a change in the potential difference and causes depolarisation
- If it is a small stimulus, only a few sodium channels will open, (generator potential)
- If more are open, the potential difference across the cell membrane will change significantly and will cause an action potential
Action potential definition:
A brief reversal of the potential across the membrane of a neurone, causing a peak of +40mV compared to the resting potential of -60mV
Resting potential definition:
The potential difference across the membrane while the neurone is at rest
What is the resting potential of a neurone at rest?
-60mV
