Nervous Coordination Flashcards
What are the key features of neurones?
-cell body
-dendrons/dendrites
-axon
-myelin sheath
-Schwann cells
-Nodes of Ranvier
What is the direction of impulse for a motor neurone?
cell body to axon terminal
What is the myelin sheath?
an electrical insulator, increases transmission speed
-a lipid
What are the nodes of Ranvier?
gaps between adjacent Schwann cells
-no myelin sheath
What is in the cell body?
-nucleus
-lots of rER
-to produce lots of proteins (especially neurotransmitters)
What is the basic structure of a sensory neurone?
cell body on the side of the axon
What are the two types of nervous system regarding motor neurones?
somatic (voluntary responses)
autonomic (involuntary responses)
What are the two divisions the autonomic nervous system?
sympathetic - fight or flight
parasympathetic - rest or digest
What is the resting potential?
-overall more negative inside the neurone than outside
-around -70mV
How is the resting potential maintained? (names of the proteins)
sodium-potassium pump
potassium ion channels
What does the sodium-potassium pump do?
-they use active transport
-to move three Na⁺ out
-2 K⁺ moves in
-using ATP
What do the potassium ion channels do ?
(maintaining resting potential)
-allow facilitated diffusion of K⁺ out of neurone
Describe the permeability of the neurone membrane to Na⁺ and K ⁺ ions
(resting potential)
permeable to K⁺ ions (through K⁺ channels- most of these are open at resting potential)
impermeable to Na⁺ ions
What type of protein channels are the sodium channels?
voltage-gated
What happens when the neurone is stimulated?
-sodium ion channels open
-Na⁺ moves into neurone down the electrochemical gradient
-makes the inside of the neurone less negative
When does depolarisation occur?
-ONLY if the threshold potential is reached
What happens when the threshold potential is reached?
-depolarisation occurs
-more Na⁺ channels open
-more Na⁺ ions diffuse in
What happens during repolarisation?
-at 30mV
-Na⁺ close
-K⁺ opens
-K⁺ ions diffuse out of the neurone down gradient
-lowers the p.d
What happens during hyperpolarisation?
-K⁺ channels are slow to close
-too many K⁺ ions diffuse out of the neurone
-cell becomes more negative than the resting potential
What is the definition of refractory period?
the period following an action potential in which a neurone cell membrane cannot be excited
How does an action potential travel through the axon?
wave of depolarisation
(propagates)
What is the benefit of the all-or-nothing principle?
-stops the brain from getting over stimulated by not responding to very small stimuli
What is the all-or-nothing principle?
-once the threshold potential is reached
-an action potential will always fire in the same change in voltage
-if the threshold potential is not reached , the action potential won’t fire
What does a bigger stimulus cause?
it will cause action potentials to fire more frequently
What are the three factors affecting the speed of conduction?
-myelination
-axon diameter
-temperature
What is the myelin sheath?
-it is made up of a Schwann cell
-electrical insulator
In a myelinated neurone, where does depolarisation occur?
at the nodes of Ranvier
What is saltatory conduction?
-process in myelinated neurones
-action potential travels (‘jumps’) between nodes of Ranvier
