Neuroscience (L1-4) Flashcards
Multiple sclerosis
- Neurological condition caused by demyelination of axons, causing slower transmission
- Symptoms include fatigue, vision problems and difficulty walking
Propogation of an AP
- Initiated at the axon hillock
- Move down an axon using saltatory conduction (jumps between unmyelinated nodes of Ranvier)
- Myelin prevents any charge leakage through the axon
Blood-brain barrier
- Semi-permeable barrier between blood and brain
- Produced by tightly packed cells in the capillary walls of the brain
- Protects and helps to regulate the chemical balance of the brain
- Small uncharged, lipophilic molecules can cross
- Other substances access the brain via active transport
What is the…
- Central nervous system
- Peripheral nervous system
CNS - brain and spinal cord
PNS - connects CNS to the organs and muscle
What is the neuron doctrine?
- The idea that the brain consists of individual neurons
- Shown by Santiago Ramon y Cajal using staining techniques
Glial cells
- Astrocytes provide structure, supply neurons with nutrients and oxygen and modulate neurotransmission
- Microglia remove dead neuronal tissue and provide immune defence
- Oligodendrocytes (CNS) and Schwann cells (PNS) insulate nerve cells with myelin sheaths
Rett Syndrome
- Affects young females
- Caused by mutations in the MECP2 protein
- Symptoms include loss of speech and motor control, seizures, orthopedic and digestive problems, anxiety, etc.
Neurons
- Perform information processing tasks
- Specialised depending on their location
- Soma contains nucleus, mitochondria, ribosomes and ER
- Dendrites are branching fibres that receive info from other neurons via synaptic receptors
- Axons are thin fibres that transmit info to other neurons
Membrane potential
- Resting membrane potential = -70mV
- Penetrable for small uncharged molecules
Action potentials
- If stimulation exceeds the threshold of -55mV, an AP is triggered (all-or-none)
1. Na+ channels open = Na+ flows in = inside more positive = depolarisation to +40mV
2. K+ channels open = K+ flows out = repolarisation
3. Refractory period occurs where an action potential cannot be initiated
4. Na+/K+ pump restores resting potential by moving 3 Na+ out and 2 K+ in
Synapses
- Junctions at which signal is passed from one neuron to another
- Delay transmission (Charles Sherrington showed reflexes are slower than conduction along axon)
- Synaptic transmission is chemical (shown by Otto Loewi)
Neurotransmitters
- Synthesised by presynaptic neuron
- Stored in vesicles in axon terminal
- Released in synaptic cleft via Ca2+-dependent mechanism
- Bind to receptors on postsynpatic neuron
How do neurons work?
- Act as an information integrator and a decision maker
- Combine excitatory and inhibitory inputs to determine whether to fire
Receptors
- Protein embedded in the membrane that matches molecular shape of a neurotransmitter
- Ionotropic receptors are ligand-gated (fast and short-lived effect)
- Metabotropic receptors are GPCRs (slow and longer-lasting effect)
Excitatory postsynaptic potential (EPSP)
Depolarisation of the neuron that increases the rate of APs in the postsynaptic neuron
Inhibitory postsynaptic potential (IPSP)
Hyperpolarisation of the neuron that decreases the rate of APs in the postsynaptic neuron
Temporal summation
When rapid repeated sub-threshold stimulations of a presynaptic neuron accumulate
Spatial summation
When postsynaptic inputs arriving simultaneously at different locations on the dendrites are combined
What are the neurotransmitter differences between species?
- Variations in the number of synapses
- Amount of neurotransmitter release
- Sensitivity of receptors on postsynaptic cells
Acetylcholine (ACh)
- Involed in motor control
- Regulates attention, learning, memory and sleeping
- Involved in Alzheimer’s disease
Dopamine
- Influences movement, motivation, emotional pleasure and arousal
- High levels linked with schizophrenia
- Low levels linked with Parkinson’s disease
Glutamate
- Excitatory NT involved in learning and memory
- High levels linked with migraines and seizures
GABA
- Inhibitory NT
- Low levels linked to seizures, tremors and insomnia
Noradrenaline
- Controls mood and arousal
- Low levels linked to depression
Serotonin
- Regulates hunger, sleep, arousal and aggression
- Low levels linked to depression
Endorphins
- Act within pain pathways and emotion centres of the brain
- Low levels can lower pain threshold
How is the action of neurotransmitters terminated?
- Re-uptaken
- Degraded
- Reabsorption
Psychoactive drugs
- Drugs facilitate or inhibit transmission at synapses
- Agonists mimic and increase the effects of a NT
- Antagonists block the effects of a NT