explain the steps of chemical synaptic transmission
- Action potential arrives at1. Action potential arrives at presynaptic terminal
- Voltage gated Ca2+ channels open
- Ca enters terminal
- Synaptic vesicles release neurotransmitters (exocytosis)
- Neurotransmitter diffuses across synaptic cleft
- Binds to receptors on postynaptic membrane
- Chemically gated Na channels open
- Postynaptic cell depolarizes → graded potential
- Threshold reach means new action potential
- The neurotransmitter is broken down for example AchE breaks down acetylcholine or its reabsorbed
what are electrical synapses connected by?
theyre connected thru gap junctions
what are postsynaptic potentials? whats EPSP? IPSP?
Postynaptic potentials AKA information processing is graded potentials in postynaptic neuron in response to a neurotransmitter
Theres two types of graded potentials:
1. EPSP (excitatory postynaptic potential)
- this depolarizes membrane and rings neuron closer to threshold. Usually when Na enters
- IPSP (inhibitory postsynaptic potential)
- this hyperpolarizes the membrane which moves neuron away from threshold, so lke K exits or CL- enters
whats the importance of axon hillock? what does it do?
A neuron receives input from THOUSANDS of synapses. Integration happens at the axon hillock
- the axon hillock is special because its closest to the initial segment, has the lowest threshold, and determines if the AP will fire
- it adds up all the IPSP and EPSP, and if the total reaches threshold, an action potential is FIRED!
neurotransmitters vs neuromodulators
- Neurotransmitters vs neuromodulators
Neurotransmitters are chemicals that are released at the synapse and directly affect membrane potential
- examples are ACh, norepinephrine, dopamine, serotonin, GABA, and more than 100 others
Neuromodulators do not directly cause AP, but they modify a neurons response. An example is endorphins (opiods) which change the sensitivity to neurotransmitters
what are the fie ways drugs can act in?
Drugs can act in 5 ways
1. Alter uptake
2. Act as antagonists (block receptors)
3. Act as agonists (mimic neurotransmitter)
4. Increase release
5. Alter breakdown
what is aceytlcholine
Acetylcholine (ACh)
- this is an excitatory and controls skeletal muscle
what does nicotine do? is it an antagonist?
Nicotine is an agonist that acts like a mimic of neurotransmitters to bind and activate to nicotinic receptors
what does caffeine and nerve gas do?
Caffeine increases depolarization
Nerve gas inhibits ACh breakdown by inhibiting acetylcholinesterase
what is GABA? what does it do? what three drugs enhance its effects?
GABA Gamma Aminobutyric acid (major inhibitory neurotransmitter)
- this reduces anxiety and inhibitory in the CNS of vertebrates
Valium (agonist too), alcohol, and xanax enhances GABA
- all increase inhibition to release a calming effect
what are drugs that affect enkephil synapses? what are endorphin/enkephlin?
Endorphins / enkephalins (opiods) are used for pain relief, also inhibitory in the CNS
- drugs like morphine, heroin, and codeine are agonists
white matter vs grey matter
- White matter → myelinated axons and signal transmission
- Grey matter → cell bodies and processing
recall: what are the 31 segments of the spinal cord and naming rules
There are 31 segments in total (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal)
Naming rules:
C1-c7 is above vertebra
C8 is below c7
There’s 31 pairs of spinal nerves which align from 31 spinal cord segments
