PSYC104 Chapter Notes - Chapter 3: Synaptic Vesicle, Axon Terminal, Behavioral Neuroscience
13 Jun 2018
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Biopsyhology
Chapter Three – Biopsychological Psychology
Nerve Cells: Communication Portals:
Neuros: The rai’s ouiators:
Neurons:
- Nerve cells specialised for communication
- Our brain contains about 85 billion neurons
The Cell Body:
- Neuronal membrane – separates the inside from the outside of the cell
- The cell body is the central region of the neuron that manufactures new cell
components, consist of large and small molecules
Dendrites:
- Portions of neurons that receive signals
- Synaptic contacts mostly occur directly onto dendrites
Axons:
- Portions of neurons that send signals
Synaptic Vesicles:
- Spherical sacs containing neurotransmitters
Neurotransmitters:
- Chemical messengers specialised for communication and released at the synapse
Axons and Axon Terminals:
- Synaptic vesicles travel the length of an axon -> to the axon terminal -> when it
reaches the end -> it bursts -> releases neurotransmitters (neurons used to
communicate)
Synapse:
- Space between two connecting neurons through which messages are transmitted
Synaptic Cleft:
- Space between two connecting neurons were neurotransmitters are released
Glial Cells: Supporting Roles
Glial Cells:
- Support cells in the nervous system that play a role in the formation of myelin and
the blood-brain barrier, respond to injury and remove debris.
- The most abundant glial cell is the astrocytes – they interact with as many as
300,000-1,000,000 neurons.
Astrocytes:
- Can be found in the blood brain barrier – a protective shield that insulates the brain
from infection by bacteria and other intruders.
Oligodendrocyte:
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- Another type of Glial cell – promotes new connections among nerve cells and
releases chemicals to aid in healing.
- This cell produces an insulating wrapper around axons called the myelin sheath.
Myelin sheath:
- Glial cell-rappers aroud aos that at as isulators of the euros sigal.
Electrical Responses of Neurons
- The basis of all electrical responses in neurons depends on an uneven distribution of
charged particles across the membrane.
- Some particles are either positively or negatively charged, when there are no inputs,
it is at resting potential.
Resting Potential:
- Electrical charge difference across the neuronal membrane, when the neuron is not
being stimulated or inhibited.
Graded Potentials:
- They are postsynaptic potentials that can be excitatory or inhibitory, depending on
the charge (+ or -)
- During an action potential, positive particles rapidly flow into the axon
- When the axon accumulates maximal levels of positive charge, positive particles
begin to flow back out of the axon
- Excitatory inputs and inhibitory inputs add together or cancel out – when excitation
prevails and reaches a high enough level, called the threshold, an action potential
occurs.
Threshold:
- Membrane potential necessary to trigger an action potential
Action Potentials:
- Electrical impulses that travel down the axon and allow neurons to communicate
- They are regenerative, the action potential continues all the down to the axon
terminal
- After each potential there is an absolute refractory period
Absolute refractory period:
- Time during which another action potential is impossible; limits maximal firing rate
Chemical Neurotransmission
They orchestrate intercellular communication among neurons – they bind to specific
receptor sites that uniquely recognise a specific neurotransmitter.
Receptor Sites:
- Locations that uniquely recognise a neurotransmitter
Three steps in neurotransmission:
1. Release of the neurotransmitter from the axon terminal into synaptic cleft
2. Binding of the neurotransmitter to its receptor site
3. Halting neurotransmission by either the chemical breakdown of the
neurotransmitter or by reuptake of the neurotransmitter back into the axon terminal
– a process by which the synaptic vesicle engulfs the neurotransmitter.
Reuptake:
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- Means of recycling neurotransmitters
Neurotransmitters:
- Different ones communicate different messages.
- Some excite the nervous system – increases activity
- Some inhibit the nervous system – decreases activity
- Some play a role in movement, pain perception, thinking, emotion
• Glutamate and GABA:
o Most common neurotransmitters in the CNS
o Glutamate excites neurons – associated with enhanced learning and memory
o If it is abnormally elevated, the glutamate may contribute to schizophrenia
and other mental disorders because in high doses it can be toxic
o GABA inhibits neurons – most anxiety drugs will bind to GABA receptors and
suppress the overactive brain areas linked to worry
• Acetylcholine:
o Plays a role in arousal, selective attention, sleep and memory
o I Alzheiers these are graduall destroed, leadig to eor loss.
• Monoamine Neurotransmitters:
o Norepinephrine, dopamine and serotonin are monoamine neurotransmitters
o They contain a building block of proteins
o Dopamine – role in reward experiences, (sex, food, gambling jackpot)
o Norepinephrine – can activate or deactivate
o Serotonin – can activate or deactivate
• Neuropeptides:
o Strings of amino acids in the nervous system.
o Act like neurotransmitters, but they are typically specialised.
o Endorphins – pain reduction
• Anandamide:
o Cells such as neurons make this, binds to the same receptors as THC – plays a
role in eating, motivation, memory and sleep
• Psychoactive drugs:
o Drugs interacting with neurotransmitter systems are called psychoactive –
they affect mood, arousal or behaviour in some way
o Knowing the interaction can help predict how they affect mental state, mood
or behaviour
Neural Plasticity: How and When the Brain Changes
Plasticity:
- Ability of the nervous system to change
Nervous system is most capable of change during early development – brains do not fully
mature until late adolescence or early adulthood.
The network of neurons in the brain changes over the course of development in four
primary ways:
1. Growth of dendrites and axons
2. Synaptogenesis, or the formation of new synapses
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Document Summary
Our brain contains about 85 billion neurons. Neuronal membrane separates the inside from the outside of the cell. The cell body is the central region of the neuron that manufactures new cell components, consist of large and small molecules. Synaptic contacts mostly occur directly onto dendrites. Chemical messengers specialised for communication and released at the synapse. Synaptic vesicles travel the length of an axon -> to the axon terminal -> when it reaches the end -> it bursts -> releases neurotransmitters (neurons used to communicate) Space between two connecting neurons through which messages are transmitted. Space between two connecting neurons were neurotransmitters are released. Support cells in the nervous system that play a role in the formation of myelin and the blood-brain barrier, respond to injury and remove debris. The most abundant glial cell is the astrocytes they interact with as many as.
