Basic principles of neural and glial structure* Flashcards
What are the 3 factors that membrane potential in cells are determined by?
- The concentration of ions on the inside and outside of the cells.
- The permeability of the cell membrane to those ions through specific ion channels.
- By the activity of electrogenic pumps that maintain the ion concentrations across the membrane.
Explain action potential.
At rest sodium/potassium, pumps move sodium ions out of the cell.
This creates an imbalance so the inside of the neuron is negatively charged.
Na channels are closed so sodium cannot re-enter.
When a neuron is stimulated sufficiently, sodium channels are opened and ions rush into the neuron creating a positive charge inside the cell.
Explain the all or none rule.
A neuron will either conduct an action potential or it will not.
If the stimulus < threshold = no impulse.
If the stimulus > threshold = action potential.
Explain the structure of synapses.
When the axon meets the dendrites of another neuron or an effector the axon bulges to form a synaptic bouton.
What are glial cells?
They make up 10% of cells in the nervous system. They are involved in nutrition and insulation of neurons.
What glial cells are found in the PNS?
Schwann Cells.
Explain the insulation of neurons.
Neurons are insulated from each other by layers of specialized fat in the membranes of the glial cells, which wrap around the axons.
Neurons with an insulated layer are myelinated, they conduct impulses faster than non-myelinated nerves.
What are the gaps on the axons called?
Nodes of Ranvier, which is where all the ion channels are located.
What are astrocytes?
They are a type of glial cell which is involved in the nutrition of neurons in the CNS
What are Microglia?
They are a type of Glial cell which are defensive in the CNS and remove debris.
What are the two types of peripheral nerves?
Cranial nerves and spinal nerves.
How many spinal nerves are there and explain their role?
31 Pairs. They are a mixed nerve (motor and sensory). They Carry sensory axons from receptors in the skin to the spinal cord. Carry motor axons from the spinal cord to the muscles.
What do spinal nerves segregate into?
It segregates into a dorsal root which contains sensory axons and a ventral root containing motor axons. They segregate before entering the spinal cord.
