neuronal communication Flashcards
Sensory receptor
Nerve ending that respond to a stimulus to generate action potential
Transducer
Converts energy from one form to another
stimulus
Change in the internal or external environement
Effectors
cells that bring around a response to a stimulus
effectors/glands
What is the route of transmission in the nervous system
Stimulus - receptors - CNS (brain + spinal chord) - Effectors - Response
What is the Pacinian corpuscle
Pressure detector in the skin
How does the Pacinian Corpuscle generate action potential
Plasma membrane stretch causes there to be gaps between the phospholipids
Sodium ion channels then open
sodium rushes down the electrochemical gradient
creates cation potential
Hows resting potential established and maintained
2k+ move out & 3Na+ move in the membrane actively pumped via ATP
K+ diffuse and leak out
Na+ doesn’t , the membrane is less permeable to it.
Sodium-voltage gated channel is closed.
Explain the all or nothing principle
if the stimulus isn’t strong enough then the threshold value wont be reached
depolarisation isn’t of sufficient levels to generate action potential
How does the synapse work
Action potential travels down the neurone - Acetylcholine
Ca 2+ channels open
Ca 2+ diffuses in
Pushes neurotransmitters into vesicles
Vesicles to presynaptic membrane
Vesicles fuse with the membrane and are released by exocytosis into the synaptic cleft
Neurotransmitters bind to the receptor site and sodium channels open Sodium diffuses in and causes depolarisation
Action potential threshold is reached
Neurotransmitter in a synapse
Acetylcholine
What’s the threshold value
- 55 mV
How is action potential generated
Na+ channels open - Na+ diffuses inside the membrane - causing other Na+ channels to open (positive feedback) K+ channels close . (+40mv)
+40mV = K+ voltage gates to open and they diffuse out by facilitated diffusion Sodium-Potassium pump opens -> inside of the membrane becomes -ve –> 2K+ in and 3 Na+ out
Hyperpolarisation - K+ channels are slow to close :there’s an overshoot of K+ and its more -ve , -70mV –> channels restore (repolarisation)
Refractory period–> restores resting potential and redistributes Na+ and K+. Na+ voltage gates close –> no new impulses can be generated
What happens when pressure is exerted on the sensory neurones
Pascillian corpuscle becomes distorted. Phospholipid heads gets squished and have gaps.
Na+ ions move in
making the membrane more negative - depolarisation
This causes the threshold to be reached and action potential to occur
Why can impulse transmission only occur in one direction
neuro-transmitters are only present in pre synaptic neurones
the receptors for these are only present on postynaptic neurones
