Excitable cells Flashcards
What is the Law of Dynamic Polarisation?
Preferred direction for cell-to-cell communication
Name the specialised glial cells
Astrocytes
Schwann
Describe astrocytes
- most numerous cells in the brain
- fill spaces between neurons
- regulate the chemical content of the extracellular space
- sequester neurotransmitter to restrict communication
Describe Schwann cells
- Oligodendroglial cells
- provide myelination of axons
Describe afferent axons
sensory (afferent) axons take information from the periphery to the C.N.S
Afferent axons from skin send info to grain and spinal cord
Dorsal root of spinal cord
Present in spinal nerves
Describe efferent axons
motor efferent axons convey information from CNS to muscles
Innervate muscles
Ventral root of spinal cord
Present in spinal nerves
Role of the brain
cognition, motivation, emotion, learning & memory, volitional movement
Role of spinal cord
Automatic reflexive action, short-latency responses to stimuli
How are electrical currents generated?
movements of ions in solution
What are ion channels?
Proteins that make pore or gates to allow movement of ions
What can ion channels be?
Selective- for particular ions
Switched- to be open or closed (voltage)
What is the ratio of out to in for Na and K ions in the axon?
Na- 10:1
K- 1:20
Concentration gradient
What are two-pore domain potassium channels?
Open at rest when the cells are not excited, help set the resting membrane potential and are regulated by pH, oxygen tension and stretch
What is the electrochemical gradient?
No net movement because K+ ions diffuse down concentration gradient but also is attracted by the negative charge so both forces act together
What is resting potential?
-65mV, Nernst equation to predict but has to allow for presence of other ions
