Knee jerk reflex and action potentials SEM1 Flashcards
what is the typical path of a neuron
sensory receptor => CNS => effector
what are the components of the monosynaptic reflex arc
spinal cord
muscle spindle (sensory receptor)
skeletal muscle (effector)
what is a reflex
stereotypical motor response due to a stimulus - independent of conscious thought
when does the spindle signal to the CNS
when muscle length changes via changes in action potential frequency (defines length of muscle)
at resting membrane potential what is the charge inside compared to outside the cell
-ive inside the cell compared to outside
what is the volume of potassium (K+) inside and outside the cell
intracellularly = 140nM
extracellularly = 5nM
what is the volume of sodium (Na+) inside and outside the cell
intracellularly = 15nM
extracellularly = 150nM
what is the volume of calcium (Ca2+) inside and outside the cell
intracellularly = 0.0001nM
extracellularly = 2nM
what is the underlying mechanism of the chemical electrochemical gradient
ions flow from high to low conc.
what is the underlying mechanism of the electrical electrochemical gradient
ions flow towards regions of opposite charge
what is typically resting potential for K+ at equlibrium
typically -70 to -90mV
how does the m gate work in voltage gated Na+ channel
m gate opens rapidly with depolarisation
how does the h gate work in voltage gated Na+ channel
h gate blocks open channel (inactivation)
how does the n gate work in voltage gated K+ channel
n gate opens slowly with depolarisation and closes slowly repolarisation
what does depolarisation cause
influx of +ive ions = cell becomes more +ive
what does repolarisation cause
efflux of +ive ions = cell becomes less +ive
what does hyperpolarisation cause
greater efflux of +ive ions than at rest = cell more -ive than rest
what are characteristics of slow conduction in fiber diameter
small diameter axon (D1)
higher resistance of cytoplasm (Ri1)
harder for ions to flow through axon
depolarisation decays more rapidly
what are characteristics of fast conduction in fiber diameter
large diameter axon (D2)
low resistance for cytoplasm (Ri2)
easier for ions to flow through axon
depolarisation maintained for longer
what are characteristics of slow conduction in membrane resistance
low resistance of membrane (Rm1)
easier for ions to flow out of axon
depolarisation decays more rapidly
what are characteristics of fast conduction in membrane resistance
high resistance of membrane (Rm3)
easier for ions to flow along axon
depolarisation maintained for longer
what is the effect of myelin sheath on conduction velocity
myelin sheath increases membrane resistance, increases length constant
what is demyelination a result of
slowing nerve conduction
what diseases can occur from demyelination
multiple sclerosis
guillan barre syndrome
