Neuroanatomy
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ALS (Amyotrophic Lateral Sclerosis) – neurodegenerative disease that starts with progressive symptoms, which involve muscle weakness and eventual paralysis o Is idiopathic, which means that the cause of the disease is unknown o What happens to the nervous system?
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Motor neurons in the spinal cord degenerate and die, which is what causes motor weakness and paralysis
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Upper and lower motor neurons in the cortex both degenerate and die
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The motor neurons in the brain stem has motor neurons that control breathing muscles, which degenerate and die, and it causes breathing problems o What is preserved in ALS?
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Autonomic nervous system
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Conscious perception and sensation (touch, sight, etc)
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Language
 “higher order cognition”
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Divisions of nervous system: o Central nervous system consists of the brain and spinal cord o Peripheral nervous system consists of o Nerves are bundles of axons o Stimulating a motor nerve causes a muscle to contract o Motor nerves arise from cells in the spinal cord and are called motor neurons o In the spinal cord you see two matters, which are gray and white
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Gray matter contains cell bodies
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White matter consists of axons o Command from the cortex and brain stem goes to the spinal cord then motor nerve, which makes the muscle move
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Human Brain o The cerebral hemisphere/cortex includes four lobes:
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Frontal lobe is the most anterior region
 Parietal lobe is behind the frontal lobe and is divided from the frontal lobe by the central sulcus
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Occipital lobe is the back of the brain
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Temporal lobe is on the side, below the parietal and frontal divided by the sylvian fissure o Brain surface has two types of surfaces
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Gyrus is a ridged or raised portion of the convoluted brain surface, which is at the top
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Sulcus is a furrow of the convoluted brain surface, which is at the bottom
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Central sulcus is the boundary between the frontal and parietal lobes o What does the cortex do?
 Conscious perception, voluntary motor control, language, and “higher order cognition”
 Motor cortex is part of the parietal lobe and contains neurons that project to the spinal cord

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Is responsible for motor control and have very long axons that go from the cortex and brain stem, which projects to the spinal cord
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Lower motor neurons go from the spinal cord to the muscle
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Upper motor neurons go from the cortex to the spinal cord o Has two hemispheres:
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Right processes information from the left side of the body
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Controls muscles on the left side of body
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Left processes information from the right side of the body
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Controls muscles on the right side of body
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Corpus callosum is a bundle of axons that connects the right and left hemispheres o Brain stem is involved with:
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Digestion, breathing, sleep, arousal, temperature control, and motor control
 Damage to the brain stem would have dire consequences since it’s a small structure
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It controls the autonomic nervous system, which controls glands and muscles o Nervous system is divided into two parts:
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Central nervous system
 Peripheral nervous system consists of:
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Somatic nervous system
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Autonomic nervous system o Spinal cord carries sensory information from skin to brain
Neural Activity & Synapses
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Changes in the electrical potential (voltage) of a single neuron
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Santiago Ramon y Cajal o Spanish scientist and first neuroscientist o Made the first drawings of neurons
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Neurons have four parts/zones: o Input zone – receives information from other cells through dendrites o Integration zone – cell body (soma) where inputs are summed o Conduction zone – single axon leads away from the cell body and transmits the electrical impulse o Output zone – axon terminals at the end of the axon communicate activity to other cells
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Neurons can have many dendrites but always only have one axon, which may have multiple terminals
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Luigi Galvani o An Italian scientist who studied physiology o When dissecting a frog realized there was some sort of electrical signal, which made the frog move o He stimulated a nerve with electricity which made the muscle contract
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Ions

o Charged particles, for example Na+ while Cl- o The inside of a cell is negative relative to the outside because the cell tries to keep
Na+ outside o The membrane acts as a barrier between the inside and outside o Semi-permeable membrane is when the cell allows some Na+ to come through, which makes the inside of the cell positively charged relative to the outside o However, then the Na+ leaves and the cell is once again negative relative to the outside o There are multiple sodium channels which will allow for the ions to enter the cell; however, it is normally closed and only occasionally opens (opens for a short period of time) o Action potential
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When the Na+ has entered, which forces an action
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Originates in the axon hillock
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Propagated along the axon
 Hillock is full of Na+ channels
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Axons are myelinated
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Has an all-or-none property, which means that the neuron fires at full amplitude or not at all o Resting potential is when cell is not active o Threshold voltage is when the cell has to get to a certain voltage for there to be an action potential (low or high and it effects how easy it is to get a reaction)
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What determines the threshold is when the channels in the cell (voltage gated channels) recognizes the voltage changing o Voltage is the measure of electrical potential o Nodes of Ranvier
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Little gaps in the myelin sheath (acts as insulation) and contain the Na+ channels o Dendrites contain receptors which open in response to neurotransmitters and these receptors allow the passage of Na+
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Some channels known as ligand channels open up when a neurotransmitter
(from other cells) attaches itself to it
 Influx of Na+ causes change in voltage in dendrite
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Excitatory post-synaptic potential are light changes in voltage
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If a whole bunch of neurotransmitters start firing (activity and input in the dendrites) then there will be an influx of Na+ in the cell, which will cause the voltage to reach the threshold and eventually generate the action potential
 Neurons generate action potential when EPSP’s push neuron past threshold o The differences between action potential and EPSP
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Location – action potential starts in the axon whereas the EPSP’s are in the dendrites
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Channels – the action potential is caused by a voltage gated channel whereas the EPSP is caused by the ligand gated channel

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Amplitude – action potential is always all or nothing, but require the same voltage whereas EPSPs depend on the amount of stimulus and their sizes vary o Epilepsy
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A chronic condition where an individual has seizures
 A seizure is uncontrollable neural activity in the brain and can be either:
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Generalized – when a person is catatonic, may cause death
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Partial – when a certain location is affected
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Neural activity is measured by the EEG
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There needs to be a balance between excitatory and inhibitory, but when having a seizure, the excitatory part wins
Neurotransmitters
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Neurotransmitters are inside vesicles o A chemical that has to be synthesized in a neuron, sent to the axon and all the way down to the axon terminal (pre-synaptic); released at axon terminal and released by action potential (post-synaptic) o It then travels across the synaptic cleft and the neurotransmitter will stimulate the post-synaptic receptor (only glutamate), which creates a transient signal
(neurotransmitter will bind to the receptor briefly and then decouples from the receptor)
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Most neurotransmission in the brain involves two neurotransmitters o Glutamate
 Main excitatory neurotransmitter in brain
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When glutamate channel opens it stimulates glutamate receptors
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Causes Excitatory Post Synaptic Potential (EPSP)
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Allows the passage of Na+, which allows activity o GABA
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Main inhibitory neurotransmitter in brain
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Stimulates GABA receptors
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Causes Inhibitory Post Synaptic Potential (IPSP)
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Allows the passage of Cl-, which inhibits activity
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Drugs o Anti-seizure drugs stimulate GABA receptors as well as alcohol o All neurotransmitters are endogenous and agonist o Some drugs exist in nature that act like neurotransmitters
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Ex. Muscimol is derived from mushrooms and acts on GABA receptors o Endogenous – chemicals naturally created/present within the body o Exogenous – chemicals introduced from outside the body o Agonist – a chemical that will bind to/stimulate a receptor
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All neurotransmitters are agonists as well as some natural compounds o Antagonist – a chemical that binds to a receptor but blocks it from stimulating
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Ex. Ketamine is a sedative that blocks glutamate receptors o Two types of neurotransmitters:
 Directly change voltage like Glutamate and GABA

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Neuromodulators have indirect effects on cell activity:
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Dopamine o Activated when one receives an award, released during
“salient events” o Involved in mood, decision making and movement
(Parkinson’s disease) o Cocaine and amphetamine affect dopamine o DAT (dopamine transporter) o Drugs that block DAT (stays in cleft) increases dopamine signal o Neuroleptics block dopamine receptors and act as antipsychotics o Psychostimulant drugs affect two processes at synapse/regulate neurotransmitter release: o Reuptake
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Transporters in pre-synaptic site picks up the neurotransmitter and gets it back in the terminal o Autoreceptors
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Located on the axon terminal
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Detects the amount of dopamine
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Serotonin o Involved in sleep, mood & anxiety, as well as digestion o SSRI’s (Selective serotonin reuptake inhibitor) increase serotonin activity and improves mood o The serotonin transporter removes serotonin from synapse o Degradation is when the neurotransmitter is transformed, which breaks it down; the degradation of serotonin by enzymes (MAO) o Drugs that block MAO prolong serotonin signal
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Cannabinoids o Affects cognition, mood, appetite, and pain o Transmission that goes from the dendrite to the axon terminal is called retrograde signaling
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An endocannabinoid inhibits further release of cannabinoid o Drugs that block cannabinoid receptors improves memory o Drugs that simulate cannabinoid receptors alters cognition o released and then inhibits further dopamine release
 Caffeine blocks adenosine receptors, which prevents negative-feedback
 loop and prolong dopamine signal