Lecture 3 : Neuronal Excitability Flashcards
Few statistical notes abt brain
- 100bn neurons
- 22.8bn in neocortex (males)
- 19.8bn in females
- 150,000-180,000km of nerve fibres
- 0.15 quadrillion synapses in cortex
- 1 neuron lost every second.
The Nervous System Breakdown
What are dendrites
Dendrites are branched extensions of a neuron that receive signals from other neurons and convey them toward the cell body
What is the soma?
Cell body, contains nucleus, integrates incoming signals and produces the necessary proteins and neurotransmitters
What is the axon?
The axon is a long, slender projection that transmits electrical impulses (action potentials) away from the cell body to other neurons or muscles
There are golgi type I neurons and type II.
Type I :
- Long axons
- Extend far from cell body
- Mostly motor neurons
- Pyramidal cells, purkinje cells
Type II :
- Short axons
- Close to cell body
- Mainly relay neurones
- Spinal cord or cerebral cortex (mainly found)
What is the role of the axon hillock?
The axon hillock is the cone-shaped region where the axon originates. Where action potential is initiated
What are synaptic boutons?
Synaptic boutons (axon terminals) are the bulb-like structures at the end of an axon where neurotransmitters are stored and released into the synaptic cleft.
What are the three main types of neurons?
Sensory (afferent) neurons – transmit sensory information to the CNS.
Motor (efferent) neurons – transmit signals from the CNS to muscles and glands.
Relay Neurones– connect sensory and motor neurons within the CNS
What are chemical synapses?
Chemical synapses use neurotransmitters to transmit signals across a synaptic cleft, allowing for modulation and integration.
What are electrical synapses?
Electrical synapses use gap junctions to allow direct passage of ions between neurons, enabling rapid signal transmission.
It is the fastest synapse, allows bi-direction transfer of info
What is the sodium-potassium pump?
The sodium-potassium pump actively transports 3 Na⁺ out of and 2 K⁺ into the neuron, maintaining the resting potential.
What are voltage-gated sodium channels?
These channels open during depolarization, allowing Na⁺ to rush into the neuron, propagating the action potential.
What are voltage-gated potassium channels?
These channels open during repolarization, allowing K⁺ to exit the neuron, restoring the resting potential.
What is neuroplasticity?
Neuroplasticity is the ability of the nervous system to adapt and reorganize by forming new synaptic connections in response to learning or injury.
What is multiple sclerosis (MS)?
MS is a neurological disorder where the immune system attacks myelin sheaths, impairing action potential conduction.
What causes synaptic fatigue?
Synaptic fatigue occurs when neurotransmitter supplies are temporarily depleted due to excessive stimulation.
What are multipolar cells
Neurons with one axon and multiple dendrites extending from the cell body.
Most common in CNS, lots of dendrites allow for integration of lots of signals
What are Pseudo-unipolar Cells?
Neurons with a single process that splits into two branches—one acting as a dendrite (peripheral branch) and the other as an axon (central branch)
Common in sensory neurones in peripheral nervous system, transmits sensory info from periphery to CNS
