Summary of Neurons and Neural Signalling
Neurons and Neural Signalling
Neurons & Glia: Neurons transmit information; glial cells support neural function. Human brains have ~86 million neurons.
Types of Neurons:
Sensory Neurons: Bring afferent sensory information into the nervous system.
Motor Neurons: Carry efferent signals to muscles for action.
Interneurons: Connect sensory and motor neurons.
Neuron Structure:
Surrounded by a semipermeable membrane.
Cell Body: Contains genetic information and synthesizes proteins.
Dendrites: Receive messages from other neurons.
Axon Hillock: Integration point for incoming signals; if strong enough, triggers action potential.
Axon Terminals: Release neurotransmitters to stimulate other neurons.
Neural Signals:
Signals move via membrane potential changes driven by Na+ and K+ ions.
Resting Potential: Inside neuron at -70 mV; high K+ inside and high Na+ outside.
Action Potential: Triggered at -55 mV; Na+ influx increases potential to +35 mV, followed by K+ efflux returning to resting potential.
Propagation of Action Potentials:
All-or-nothing response; action potentials maintain the same strength and vary only in firing rate.
Synapse:
Space between neurons where neurotransmitters are released.
EPSPs and IPSPs:
EPSPs increase likelihood of postsynaptic action potentials.
IPSPs decrease this likelihood.
Neurotransmitter Types:
Glutamate: Mainly excitatory; causes EPSPs.
GABA: Mainly inhibitory; causes IPSPs.
Acetylcholine: Involved in muscle contraction at neuromuscular junction.
Norepinephrine: Modulates stress response, arousal, and attention.
Dopamine: Involved in mood, reward, and motor control.
Serotonin: Regulates mood and is targeted by antidepressants.
Neurotransmitter Recycling:
Unused neurotransmitters are broken down or reabsorbed (reuptake).
Drug Interactions:
Agonists: Enhance neurotransmitter action (e.g., SSRIs).
Antagonists: Block neurotransmitter effects (e.g., Naloxone).