Week 2 Flashcards
(161 cards)
List the basic structures of a neuron
anatomical components:
Dendrites
Soma (cell body)
node of ranvier (comes before axon hillock in a sensory neuron)
axon hillock (comes before NoR in a motor neuron)
Axon
Axon terminal
Is the strength and connection of the synapse modifiable?
yes
Each neuron makes and receives up to 10,000 synaptic connections with others
Neuroplasticity: its the brain’s ability to adapt and reorganize by forming new neural connections in response to learning, experiences, injuries, or environmental changes. It involves structural changes, such as the growth or remodeling of synapses, and functional adaptations, like shifting tasks from damaged to healthy brain areas. Neuroplasticity is crucial for learning, memory, habit formation, and recovery from injuries like strokes, highlighting the brain’s remarkable capacity to change and adapt throughout life.
Define synapse
a specialized “zone” of contact at which one neuron communicates with another
Information transfers at a synapse
Plays role in all the operations of the nervous system
What is the role of presynaptic and postsynaptic neurons?
Presynaptic neuron
– conducts impulses
toward the synapse
(1 of these can connect to many postsynaptic neurons)
Postsynaptic neuron
– transmits impulses
away from the synapse
What are the types of synapses?
A) electrical synapses (No gap. not as common in humans, ex: SA node): signal transported by current through gap junction
No signal delay
B) chemical synapse (has a gap): signal transported by neurotransmitters in the synaptic cleft to go bind to receptors
what type of synapse is this?
electrical synapse
What type of synapse is this?
chemical synapse: The complex process of synaptic transmission accounts for the delay between an action potential in presynaptic cell and synaptic potential in the post synaptic cells compared to the virtually instantaneous transmission of signals at electrical synapses.
What are the characteristics of an electrical synapses?
- Distance between pre- and post- cell membrane: 3.5 nm
- Cytoplasmic continuity between pre- to post- synaptic cell: YES (physical touch)
- Gap junction (specialized ion channels)
- Agent of transmission: Ion current
- Synaptic delay: virtually absent
- Direction of transmission: bi-directional
What are the characteristics of a chemical synapse?
- Distance between pre- and post- cell membrane: 20-40 nm
- Cytoplasmic continuity between pre- to post- synaptic cell: NO (physical touch)
- Synaptic cleft
- Agent of transmission: Chemical neurotransmitter
- Synaptic delay: at least 0.3 ms, usually ranged from 1-5 ms or longer
- Direction of transmission: uni-directional
What are the advantages of a synapse through neurotransmitter (chemical)?
- The advantage of using neurotransmitter is that the nerve impulse can be given some more specificity
Neurotransmitters can also control the operation of the nervous system by inhibition or excitation
Signal can be modulated (i.e. amplified or degraded) based on a specific type of synaptic connections (ex. Presynaptic inhibition)
- Many drugs that try to cure problems in the nervous system operate at synapses
What are the steps of synaptic transmission?
A.Voltage-gated Ca2+ channels at the active zone open
B.Neurotransmitters released to the synaptic cleft
C.Neurotransmitters bonded to membrane receptors of post-synaptic cells and triggered changes in membrane potentials at post-synaptic sites
Explain these steps
Voltage-gated Ca2+ channels at the active zone open
1) Action potential arrives at the terminal
2) The membrane of pre-synaptic terminal depolarized
3) Voltage-gated Ca2+ channels at the active zone open cause influx of Ca2+
Neurotransmitters released to the synaptic cleft
4) Influx of Ca2+ triggers synaptic vesicles moving toward the release sites
5) Vesicles fuse with the membrane and release neurotransmitters
6) Neurotransmitters then diffuse across the synaptic cleft
Neurotransmitters bind to membrane receptors
7) Neurotransmitters bind to membrane receptors of post-synaptic cells
8) Open ion channels associated with the membrane receptor or activate intracellular messengers
Explain post-synaptic potentials
- Local changes in ion concentration across the postsynaptic membrane
Excitatory post synaptic potential (EPSP) – local depolarization, allowing flow of Na+ or Ca2+ into the neuron (ex. Ach in muscle)
Inhibitory post synaptic potential (IPSP) – local hyperpolarization, allowing flow of Cl- into the cell or K+ out of the cell
What is the state of postsynaptic membrane in EPSP?
Transient postsynaptic membrane
depolarization
What is the state of postsynaptic membrane in IPSP?
Transient postsynaptic membrane
hyperpolarization
Explain the process
Knee jerk:
Sensory muscle spindle
Inhibitory interneuron inhibiting flexor motor neuron (hamstring)
Synapse with alpha motor neuron within spinal cord
Excites motor nerve within quad to activate it
How do multiple inputs combine to determine the output firing pattern of the neuron?
Synaptic Integration - Spatial and temporal summation
Explain neurotransmitters and neuromodulators
both are chemicals that convey information among neurons
1) Neurotransmitters
−released at specific synapses
−act directly on postsynaptic ion channels (iontropic) of a neuron or activate proteins (metabotropic) inside the postsynaptic neuron
Ex: ACh (excitatory neurotransmitter)
2) Neuromodulators
−released into extracellular space
−affect a group of neurons
−manifest more slowly and last longer than neurotransmitters
List types of neurotransmitters
- Acetylcholine
- Glutamate
- Serotonin
- GABA
- Dopamine
- Norepinephrine
- Substance P
describe the function of ACh and what happens when it is disrupted?
- All neurons that synapse with skeletal muscles use Ach to elicit fast-acting effects on muscle membrane
- Excitatory neurotransmitter found in neuromuscular junctions involves in muscle contractions
- Blocking ACh receptors results in paralysis
- In the brain, Ach acts as a slow neuromodulator in control of movement and attention
Disruption:
Alzheimer’s Disease:
* Deterioration of memory, reasoning, and language skills
* Low levels of Ach found in those with Alzheimer’s disease
* Symptoms may be due to loss of ACh neurons
Describe glutamate
- Major fast, excitatory neurotransmitter of CNS (most common in CNS)
- Too much glutamate (and too little GABA) associated with epileptic seizures
- Involve with learning and development
Describe serotonin
- Involved in mood, perception of pain, general arousal level, and can suppress sensory information
- Highest levels occur with alertness and lowest levels are associated with rapid eye movement sleep.
- Low levels involved in depression
– Prozac works by keeping serotonin in the synapse longer, giving it more time to exert an effect (re-uptake inhibitor)
Describe function of GABA and what happens when it is disrupted?
Gamma-aminobutyric acid (GABA)
- Inhibition (slows down) of brain activity and spinal neuronal activity
- Cause neural over-activity (i.e. seizures and unwanted skeletal muscle contractions) and anxiety when in low supply.
- Alcohol mimics GABA
Disruption:
Huntington’s disease involves loss of neurons in striatum that utilize GABA
Symptoms:
* jerky involuntary movements
* mental deterioration
Describe function of dopamine and what happens when it is disrupted?
- Affects motor activity, cognition, and behavior.
- Involved in movement, attention and learning. Also pleasure & rewarding sensations.
- Too much Dopamine involved in schizophrenia.
- Drugs like cocaine and nicotine mimic dopamine, interfering dopamine reuptake into the presynaptic neuron.
Disruption:
* Parkinson’s disease: Loss of dopamine-producing neurons in the substantia nigra