PSYC 200 Lecture Notes - Lecture 2: Axon Terminal, Neuron, Resting Potential
14 Jun 2018
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Lecture 2 January 15, 2018 Chapter 2
• Neuron: individual nerve cell
o Dendrites: Receive incoming messages from other neurons
o Soma: Cell body; contains nucleus & carries genetic material (DNA),
send/receives nerve impulses
o Axon: Carries info AWAY from the cell body (can have more than 1)
o Axon Terminal: Branches that LINK to the dendrites & somas of the other
neurons
The Nerve Impulse
• Electrically charged ions are found inside/outside the nerve cell
• Neuron @ rest (inactive neuron):
o (+) outside, (-) inside
o resting potential of -70mV
• Messages from other neurons change charge (starts going from axon & then goes to
axon terminal)
• If charge rises to -50mV (threshold), neuron will FIRE to dendrite (up a bit)
• Initiation of ACTION POTENTIAL
o Charge goes up to +30mV (shoots way up)
o Ion channels open
o Sodium ions rush in (+), travel down axon
o All-or-nothing event (travels or not at all)
• Negative After-Potential
o When charge of cell returning to action potential
o Overshoots to -90mV before returning to resting potential -70mV
1. Resting State [(+) outside, (-) inside]
2. Action potential → (+) atoms enter axon
a. Change axon charge to (+) inside, (-) outside
3. Action Potential advances as (+) & (-) charges reverse in moving zone down axon
4. After Action Potential → ions flow out of ion (back to resting state)
find more resources at oneclass.com
find more resources at oneclass.com
The Synapse
• Electrical signal passes thru axon/to axon terminal
o switch focus from electrical impulse → chemicals
• Vesicles fuse and release neurotransmitters into synaptic cleft
• Receptor sites are diff shapes → IF neurotransmitter fits, then will fire in new firing
• Pre-synaptic neuron: giving the info (axon terminal)
• Post-synaptic neuron: receiving info (dendrite)
• After: neurotransmitter released back into synaptic gap where either
o Degradation into other chemicals
o Reuptake thru vesicles in original axon terminal
Neurotransmitters
• Chemicals that alter activity in neurons; brain chemicals; transported across synapse
o Acetylcholine: activates muscles
o Dopamine: muscle control
▪ Too much = schizophrenia
▪ Too little = Parkiso’s
o Norepinephrine: adrenal; relation to learning, memory, anxiety
▪ Too much: manic/anger
▪ Too little: depression
o Serotonin: mood/appetite control
• Messages from 1 neuron to another pass over microscopic gap called a synapse
• Receptor Site: Areas on the surface of neurons & other cells sensitive (typically
accepting) to neurotransmitters/hormones
• Possible cases:
o Cause neurotransmitter to be destroyed, so less done in the process
o Prevent reuptake → more neurotransmitters in cleft → more chances of firing
Nerves & Neurons
• Nerves: Large bundles of axons & dendrites
• Myelin sheath: Fatty layer of tissue that coats axons
o Allows conduction of nerve impulse/facilitates conduction
o Multiple Sclerosis (MS) occurs when myelin layer is destroyed; numbness,
weakness & paralysis occur
find more resources at oneclass.com
find more resources at oneclass.com
Brain Plasticity
: the rai’s apaity to create new synaptic connections
• Do not necessarily form new neurons, but new connections
• The brain can continue to change throughout our lifetime
o Requires exposure to stimulating & complex environments
• Video: Little girl had right hemisphere removed, difficulty w/ left side body, able to
recover
Video:
• A lot of work at brain is if u damage/excite a brain area, what will happen to behaviour?
BUT if need to really understand a disorder need to get down to the level of the neuron
January 17, 2018
Subparts of the Nervous System
• Central Nervous System (CNS): Brain and Spinal cord
• Peripheral Nervous System (PNS): All parts of the nervous system outside of the brain
and spinal cord
o Somatic System: Links spinal cord with body and sense organs; controls
voluntary behaviour
o Autonomic System: Serves internal organs and glands; controls automatic
functions such as heart rate and blood pressure
▪ Sympathetic: ACTIVATES the ody; eergey fight or flight syste
▪ Parasympathetic: QUIETS the body; move used AFTER an emotional
event
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
If charge rises to -50mv (threshold), neuron will fire to dendrite (up a bit) Initiation of action potential: charge goes up to +30mv (shoots way up) But if need to really understand a disorder need to get down to the level of the neuron. Ho(cid:449) (cid:272)a(cid:374) (cid:449)e (cid:862)get i(cid:374)to(cid:863) the (cid:271)rai(cid:374) research methods: ablation: surgical removal of parts of the brain, deep lesioning: a thin wire electrode is lowered into a specific area inside the brain. Images/structure: computed tomographic scanning (ct): computer-enhanced x-ray of the brain or body (image/structure not activity, magnetic resonance imaging (mri): uses a strong magnetic field, not an x-ray, to produce an image/structure. Brain activity: functional mri (fmri): mri that also records brain activity uses blood oxygenation, positron emission tomography (pet): computer-generated colour image of brain activity, based on glucose consumption (or activity) in the brain most recent. : back of brain; vision center: parietal.
