Anatomy and Physiology of the Nervous System- 2 Flashcards
What is the function of the myelin sheath
Protects and insulates impulses to increase speed.
What cells produce myelin.
Shwann Cells (PNS)
Oligodendrocytes (CNS)
What type of channels are found at the node of ranvier.
A very high density of Na+ channels.
Where does an action potential begin.
Axon Hillock
How does a neuronal membrane potential develop.
- Membrane is more permeable to K+ than Na+ (Potential Develops)
- Electrical force opposes K+ outflow and favours Na+ inflow.
- Resting membrane potential develops.
- Sodium/Potassium pumps maintain gradients
A membrane potential starts to form when an equilibrium starts to form between the two.
What happens in the rising phase in a neuronal action potential.
Depolarisation (Sodium channels open)
Na+ influx via voltage gated channels
Na+ channels inactivate
Refractory period (Absolute/Relative)
What is the refractory period and what does absolute and relative mean.
The refractory period is the time after repolarisation when the action potential goes below resting potential, becoming hyperpolarised.
Absolute refractory (first half) means no matter how much stimulus is applied another action potential will not happen.
Relative refractory (last half) means if a high stimulus is applied there can be another action potential.
What happens during the falling phase of action potential.
Repolarisation(sodium channels inactivate, potassium stays open)
K+ efflux via voltage gated K+ channels.
How does a message follow through the system.
Sensory Receptors-> Afferent Neurons-> CNS -> Efferent Neurons-> Effector
What is another word for sympathetic innervation
Thoracolumbar
What is another word for parasympathetic innervation
Craniosacral
Where are ganglia located in the sympathetic nervous system.
Close to spinal cord
Where are ganglia located in parasympathetic nervous system
Close or within target organs.
What is bethanechol used for and how does it work.
A muscarinic agonist
P only medicine
Used to treat urinary retention
What are the two muscle components of the ENS.
Myenteric Plexus- Largely motor in function
Submucosal Plexus- largely sensory in function.
