dendrites - specialized branch-like structures used to receive information from other neurons. The more dendrites a cell has the more neurons it can communicate with.
the neuron’s message that travels through the cell is electrical, and they can short each other out if a neuron touches one in the wrong area – so the glial cell is insulation.
(oligodendrocytes produce them in the Central Nervous system and Schwann cells produce them in the neurons of the body).
Multiple sclerosis Is ainflammatorydisease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms. Disease onset usually occurs in young adults, and it is more common in women.
The gaps (approximately 1 micrometer wide) formed between myelin sheath cells long the axons are called Nodes of Ranvier. Since fat serves as a good insulator, the myelin sheaths speed the rate of transmission of an electrical impulse along the axon. The electrical impulse jumps from one node to the next at a rate as fast as 120 meters/second. This rapid rate of conduction is called saltatory conduction. Myelinated axons are rare in the autonomic nervous system. Invertebrates do not have myelinated sheaths.
THEY MUST TALK! Which is why there are neural impulses!
Think of it like a baseball game; sodium ions on the outside are the fans and the wanna see the game. When the cell is at rest (a state called resting potential), the ions are stuck outside because despite all the gates that the cells have, the specific gates that will allow these ions to pass through aren’t open yet.
Action potential because the electrical potential is now in action instead of at rest
Reaction will start at the part closest to the soma; and then proceed down the axon in a kind of chain reaction.
Neurons receive many signals all around/ some signals tell the neuron to fire, and others tell it not to, so it’s constantly adds the fire and don’t fire messages together, and if the fire messages cross the threshold, the neuron will fire.Threshold - a dividing line that determines if a stimulus is strong enough to warrant action. If the threshold is reached, an action potential will occur.
And starts the active potential of the next cell
Paralysis - The result of curare, a South American drug. It is thus an antagonist of acetylcholine.On the other hand, if too much of this is released (just like the black widow spider’s venom), convulsions and maybe death can occur. It’s an agonist for acetylcholine.
Psychology a voluntary or involuntary restraint on the direct expression of an instinct.
Psychology a voluntary or involuntary restraint on the direct expression of an instinct.In some people, the normal process of adjustment of moods is not working properly; serotonin is either not produced or not released in enough amounts. It can’t fully activate the receptors on the next neurons. This leads to a state of depression.
Ach isn’t taken back ‘cause it’s responsbile for muscle activity, and this whole reaction needs to happen rapidly and continuouslyAcetylcholine is taken back by an enzyme cells manufacture that breaks it down and cleans the synapses of it
The story is taught in medical schools to emphasize that you do not need to lose consciousness to suffer a severe brain injury and that a brain injury can cause profound behavior changes in the individual.
Biological Perspective Aurelio | Lopez | Pablo |Rodas |Yao
Nervous SystemA Network of cells that carries information to and from all parts of the body
NeuroscienceLife science concerned with the structure and the functioning of the brain, neurons, nerves, and nerve tissues (All part of the nervous system)Special focus on the relationship of behavior and learning Santiago ramón y cajal (1887): Doctor who studied about brain tissue; theorized that the nervous system is made up of individual cells
Neuron It Receives and sends messages within the Nervous System “Messenger of the body” Makes up only 10% of the brain but there are millions of them!
Parts of the neuronDendrite (“Branch”) – receives messages from other cellsSOMA; cell body – dendrites attach to this, contains the nucleus and keeps the neuron alive and functioning
Parts of the neuronAxon – fiber attached to the soma/Cell body that carries out messages to other cells • Does most of the travelling through the body• Coated by myelin sheaths and neurillema (aka schwann’s membrane)
Parts of the neuron neurillema – surrounds both the axon and the myelin sheath • Serves as a tunnel where damaged nerve fibers can repair themselves• Axons in the brain and spinal cord don’t have this.
Glial Cells Gray fatty cells that compose 90% of the brainIt keeps neurons in place + lets them develop and work Provides structural support – insulation • A Neuron’s message = electrical
Functions of the Glial Cells Some Get nutrients to the neuronsOthers are in charge of Cleaning up dead neurons The Communication with neurons and other glial cells Act as insulatorsSome affect the functioning of neurons and their structure, and “give birth” to new neurons during prenatal development
What else do they do? They create myelin!• Myelin: layer of fatty substance created by 2 types of glial cells
So, what does Myelin do? It Creates a sheath around the axon which Protects it from damageMultiple sclerosis: damages the myelin sheath; leads to a loss of function
So, what does Myelin do? it Speeds up the neural message travelling down the axon • HOW? Nodes of ranvier – they’re the periodic gap in the myelin sheaths of the axon; facilitate the rapid conduction of nerve impulses
NervesA “cable” of bundled-up myelin-coated axons (The nerves are the ones in green)
Axon TerminalArea at the end of the neuron where it meets another neuron
Ions We have both positively (+) and negatively (-) charged particlesHowever, we’re only concerned withthe sodium (na+) and Potassium (K+) ions for the neural impulseIons inside are mostly negative, while ions on the outside are mostly positive
Selectively Permeable MembraneOuter membrane of the neuron is not impermeable It Selectively allows some ions to pass through HOW? It has pores that are only largeenough for small ions to pass through; the gates
Charge of the Neuron When the cell is at rest (not firing a neural impulse) it’s primarily negativeThere are lots of positive sodium ions outside the membrane, while the ions inside are negative They cluster around the membrane Difference in electrical charges = electrical potential
StimulusEventually, when the cell receives some stimulation from another cell Dendrites activateThe particular gates are now open which allow the sodium ions on the outside to rush into the cell
Action Potential Causes the inside of the cell tobecome mostly positive; the outside, mostly negativeThe Reversal of electrical charge = action potential
Action PotentialWhen action potential gets to the end of the axon, the message is transmitted to another cell
RepolarizationThe neuron will now try to restore its charge by pumping out the positively charged ions and bringing back the negative ones
All-or-noneNeurons are either firing at full strength, or does not fire at allA strong message = fire more quickly
The SynapseEnd of the axon has several short fibers(axon terminals) with Calcium ions nearby At the end of each terminal, there is a synaptic knobIt has a number of saclike structures in it called synaptic vesicles that contain neurotransmitters (chemical inside a neuron that transmits messages)
The Synapse Next to the synaptic knob, there’s a dendrite of another neuronThey don’t connect, but there’s a gap in between them called the synaptic gap
The SynapseThe dendrite of the neighboring neuron contains locks called receptor sites Shaped in a certain way that only aparticular molecule of a neurotransmitter can fit into itThe calcium stimulates the vesicles tomove to the end of the knob wherein theyrelease neurotransmitters to the synapseThey’ll fit themselves into the receptor sites, which activates the next cell
The SynapseNeurons can also be turned on or off, depending on exactly what synapse is being affected Turn cells on (excitatory effect) Turn cells off (inhibitory effect)
Agonists Chemical substances that can mimic/enhance the effects of aneurotransmitter on the receptor sites of the next cell
Antagonists Chemical substance thatblocks/reduces a cell’s response to the action of other chemicals/neurotransmittersBETA BLOCKERS: drugs used to control blood pressure by blockingheart contractions which lowers the
Acetylcholine Found at the synapses between neurons and muscle cellsStimulates the contraction of skeletal muscles Also found in hippocampus (brain area responsible for new memory) If receptor sites are blocked = paralysis
Glutamate It’s a Major excitatory neurotransmitter of the nervous systemImportant role in learning and memory formation
GABA (Gamma-aminobutyric acid) Most common inhibiting neurotransmitter of the brainHelps calm anxiety; it’s agonized by alcoholCauses the general inhibition of the nervous system associated with drunkness
SerotoninFound in the lower part of the brainCan either be excitatory or inhibitory; depends on what synapses are affected Associated with sleep, mood and appetite Low levels of serotonin have been linked to depression
Dopamine Also found in the brain; likeserotonin, it can have different effects depending on the locationControl of movement, sensations of pleasure Too little released = parkinson’s disease
Endorphin (Endogenous Morphine) – Neural regulator or neural peptide (a neurotransmitter that directly controls the release of other neurotransmitters) that controls pain in the body.– The body halts production of this if people take morphine or heroin, leaving them with no protection against pain when the drug wears off (withdrawal). • Leads to addiction
Cleaning up the synapse – Neurotransmitters have to get out ofreceptor sites before the next stimulation occurs – Reuptake: process whereneurotransmitters are taken back into the synaptic vessels – Acetylcholine is not taken back
Cleaning up the synapse – SSRI (Selective serotonin reuptake inhibitors) – Blocks the reuptake of serotonin– Leaves more in the synapse to bond with receptor sites – Elevates mood and lifts depression
Central Nervous System • Consists of the brain and spinal cord- Both are composed of neurons and glial cells that control life-sustaining functions, thought, emotion, behavior.
Brain• Makes sense of information received from the senses, makes decisions, sends commands out to muscles and the rest of the body
Spinal Cord • A long bundle of neurons that serves 2 vital functions for NS. • Divided into two areas.– Outer section is composed of axons and nerves (which appear white). Carries messages from the body to brain and vice-versa; a message pipeline. – Inner section is composed of somas (which appear gray). It is a primitive “brain” that is responsible for very fast, lifesaving reflexes.
Spinal Cord• Damage to it was once thought permanent. Healthy brain cells only took over the damaged ones. – It is now known that they can actually be repaired by the body systems. – Scientists can implant nerve fibers from outside the spinal cord into a damaged area and coax the damaged spinal nerves – The brain can also change itself by adapting neurons to serve new functions when older ones die or become damaged. – Dendrites grow and new synapses are formed in
Reflex ARC: 3 types neurons • Afferent/Sensory Neurons (“Afferent Accesses Spinal Cord”) – Carries messages from senses to spinal cord • Efferent/Motor Neurons (“Efferent Exits”) – Carries messages from spinal cord to muscles and glands • Interneurons – Connects Sensory and Motor Neurons – Makes up the inside of the spinal cord and brain• This all happens very quickly. It allows for very fast
Neuroplasticity• Lifelong ability of the brain to reorganize neural pathways based on new experiences • Ability of the brain to change with learning • Has a clear age-dependent determinant (the younger the more plastic) • Occurs in the brain under 2 conditions: – Developmental plasticity and plasticity of learning and memory – Compensation for lost function and maximizing what is left
Stem Cells • Repairs brain damage/disease. • Controversial as it comes from embryos • Recently, scientists have tried turning mice bone marrow cells into stem cells.• It is possible too that adult bone marrow can be used.
Peripheral Nervous System• Compromised of the nerves and neurons not contained in the brain and spinal cord• Transmits information to and from the central nervous system
Somatic Nervous System• Controls the voluntary muscles of the body • Carries sensory information and controls movement of the skeletal muscles
Autonomic Nervous System• Controls automatic functions of the body • Automatically regulates glands, internal organs, blood vessels, pupil dilation, digestion, and blood pressure
Parasympathetic Division• Maintains body functions under ordinary conditions; saves energy Sympathetic Division • Prepares the body to react and expand energy in times of stress
Parasympathetic Division• GLANDS are organs in the body that secrete chemicals, some affect functioning of the body but not all behavior, others have widespread influence on the body and behavior. • ENDOCRINE GLANDS secrete chemicals called hormones into bloodstream; affect behavior and emotions by influencing the activity of the brain and by controlling
Peeking Inside the Brain • It is impossible to tell the function of a brain structure if it is dead.• A scientist can’t even be sure what the brain tissue looks like in the skull.
Clinical Studies• Study animals or people with brain damage- Animals: May damage deliberately, then are tested. Or the area can be electrically stimulated• Deep lesioning: insertion of a thin, insulated wire into the brain, then a current is sent that destroys the brain cells at the tip of the wire • ESB (Electrical Stimulation of the Brain): stimulation of brain tissue with milder current; causes neurons to react as if they’ve received a message
EEG (Electroencephalograph) • Record electrical activity of neurons below skull with EEG machine• Small metal disks (electrodes) are placed on the skin covering the skull using a jelly-like substance to help conduct. The electrodes are wired to a computer (older ones connected to graphing machines)
EEG (Electroencephalograph) • Output: Waves that indicate sleep, seizures, tumors, etc. It also determines which areas of the brain are active during reading, writing, speaking, etc. • Alpha waves: Regular, slower waves - relaxation • Beta waves: Irregular, fast waves - waking activity • Theta waves: Drowsiness and sleep• Delta waves: Large, slow waves - Deep stage
EEG (Electroencephalograph) • ICA (Independent Component Analysis): Allows identification of individual signals• ERP (Event-Related Potential): Results of multiple presentations of a stimulus are measures and averaged; hence an electric potential – May be used to follow Alzheimer’s, and lie detection
CT Scan (Computed Tomography Scan) • X-ray of the brain that maps “slices” of the brain by computer • Can show stroke damage, tumors, injuries, abnormal structure• Good for imaging brain structure especially if there is metal in the body
MRI Scan (Magnetic Resonance Imaging)• Magnetic field that can create a 3D image of the brain and display “slices” of it • More detailed than CT Scan• Strongly not recommended if the person has metal in their body
PET Scan (Positron Emission Tomography) • Sees brain in action• A radioactive glucose is injected in the brain, and the computer detects which parts of the brain are using them up. It projects it on a monitor. – Why glucose? It is the “fuel” of the brain. • Uses colors - lighter areas are active and darker ones inactive
FMRI (Functional Magnetic Resonance Imaging) • A form of MRI where the computer tracks changes in oxygen levels of blood. It is placed on top of the picture of the brain• By combining images, a “movie” can be made • More detailed than PET Scans
• Case: (1861) a Man lost ability to speak after a head injury • Later, after the post mortem autopsy, broca was able to demonstrate that the cause of the man’s deficit lay in the damage to a specific point in the brain • Proof of this localization of function (connecting a specific behavior to a specific brain area)
Henry Molaison -Removal of Both Medial Temporal Lobes (Loss of hippocampus, amygdala, and perirhinal cortex) - Severe anteroggrade amnesia
Phineas Gage The Accidental Neuroscience Pioneer
John Martyn Harlow • Phineas Gage’s Doctor • Arrived an hour after Gage was brought to the hospital • Did all he could to find out what caused Gage’s changes in behavior. • “No Longer Gage” • Continued to study Gage’s skull long after he died.
Biological Perspective • The tamping iron hit the frontal lobe of Gage’s brain causing changes in personality. • From a mild mannered man, Gage turned into “fitful, irreverent, indulging at times in the grossest profanity (which was not previously his