The Nervous System 1 Flashcards
What is a neuron?
A nerve cell that transfers information within the body.
Electrical signals (long distance) & Chemical signals (short distance)
What are the 3 different types of neurons?
- Sensory Neurons: transmit information about external stimuli and internal conditions
- Interneurons: form local circuits connecting neurons in the brain or ganglia (responsible for integration of sensory input) MORE COMPLEX, FOUND IN BRAIN
- Motorneurons: transmit signals to muscle cells
Where does processing of information (of nerves) take place?
Clusters of neurons called ganglia
or complex organizations of neurons called brain
WHat are the 3 stages that occur when nervous systems process information?
- Sensory input
- Integration
- Motor output
Use the words: axon, synapse, synaptic terminal, neurotransmitters
How does a neuron transmit information?
What is a synapse?
- A neuron receives information from its dendrites
- Information is transmitted along the axon towards a synapse
- Neurotransmitters are sent across the synapse from the presynaptic cell’s synaptic terminal
Synapse: a junction between an axon and another cell
What are the five types of glia and what do they do?
- Astrocytes: support neurons and form blood-brain barrier
- Ependymal cells: promote circulation of cerebrospinal fluid (CSF)
- Microglia: protect nervous system from microorganisms (white blood cells of brain
- Oligodendrocytes/Schwann cells: form myelin sheaths around axons
What is a cell’s membrane potential and resting potential?
Membrane potential: a cell’s difference in electrical charge across its plasma membrane
Resting potential: the membrane potential of a neuron not sending signals
Messages are transmitted as changes in membrane potential
In mammalian neuron K+ is greater inside a cell & Na+ is greater outside
How is the potassium and sodium gradient across the plasma membrane maintained? What are the steps?
Sodium-potassium pumps use the energy of ATP to maintain the K+ and Na+ gradient.
1. Na+ binds to the pump with high affinity
2. When 3 Na+ binds to the pump, phosphorylation is stimulated by a kinase using ATP
3. Phosphorylation leads to a change in protein shape, reducing affinity for Na+, releasing them
4. The new shape has high affinity for K+, 2 K+ bind and release the phosphate group
5. Loss of the phosphate group restores the original shape, low K+ affinity
6. 2 K+ are released, affinity for Na+ is high again and cycle is repeated
SODIUM GOES OUT POTASSIUM GOES IN
Potassium leak channel
When is it active (when others arent)?
The potassium leak channel allows K+ ions to leak out of the cell. It is active when a neuron is not transmitting a signal, which is why resting neurons are most permeable to K+ ions.
helps set the resting potential
Voltage gated potassium channel
Opens slowly causing delayed efflux of potassium. Important for restoring membrane potential after depolarization.
Voltage gated sodium channel
Opens rapidly allowing influx of sodium. Important for depolarizing membrane during action potentials.
Voltage gated calcium channel
Opens when membrane depolarizes and lets calcium flow into cell. Important for synaptic release.
Graded (potential) depolarizations
Graded depolarizations are a (more positive) shift in membrane potential in response to a stimuli
Because they don’t break the threshold, they decay overtime with distance from their source.
Action potential
What is the threshold? Why is it considered all or none?
The depolarization reaches the threshold (about -55 mV) because the stimulus is strong enough. The action potential is a nerve impulse that carries info along an axon.
- Action potentials either occur fully or not at all, making them all or none
