1. Selective Permiability: at rest, K+ channels are OPEN, Na+ CLOSED
2. Diffusion along Concentration Gradient: High to Low concentration. K+ flows OUT of cell.
Inside becomes MORE NEGATIVE
K+ stops flowing when outside becomes too negative
3.Sodium/Potassium pump restores charge
Active transport: Na+ leaks INTO cell (Uses lots of energy)
NOW Pumps Na+ out & K+ in
Na+:K+ = 3:2
Neuron membrane AT REST
SALTY BANANA CHIP:
Higher Potassium INSIDE (K+)
Higher Sodium OUTSIDE (Na+)
Voltage-gated sodium channel CLOSED
Inside NEGATIVELY charged =POLARIZED
Neurons get signals & change state - Proportional to stimulus.
(ends when stim ends)
NEGATIVE current = Hyperpolarizing
Larger negative response, goes back to resting.
POSITIVE current = Depolarizing
Action Potential STEPS
(After voltage reaches threshold)
Depolarization above threshold
Initially graded potential
Above threshold = Action potential
Threshold ~ (-50)
1. Voltage-gated sodium channel: Opens at Threshold
2. Sodium rushes in, makes cell MORE POSITIVE
3. Stays open only .5 to 1 msec, slams shut
4. K+ more permiable, so K+ rushes back in & Repolarizes
Messages sent by axons
Always same size/shape
More stimulus = more rapid impulses, NOT larger impulse
DEPOLARIZATION (More +)
Undershoot Phase following Action Potential
Occurs because most voltage-gated Potassium channels are still open
Total Potassium of neuron is greater than when neuron is at resting state
A protein-mediated process that expends energy to enable a molecule to cross a membrane
Sodium-Potassium pump transports Sodium OUT of cell and Potassium IN to maintain Negative charge
examples in the brain:
Axon that brings information INTO a structure.
Every sensory neuron is an afferent TO the rest of the nervous system
(every motorneuron is an efferentFROM the nervous system)
Turn ON or MIMIC effects of Neurotransmitters
ex Drugs that cause neurons to RELEASE dopamine
ex Alcohol, benzodiazapines - INCREASE activity of GABA
Ethanol binds to MANY RECEPTORS:
AC h R(Acetylocholine)
GABA R (main actions)
NMDA R (glutamate receptors)
Alters DA (dopamine) - Increases at receptors in the nucleus accumbens
Binds to GABA receptor (brains's main inhibitory site)
Increases GABA activity
ex like benzodiazepines
Blocks activity at the Glutamate receptors (brain's main excitatory site)
These both lead to DECREASE IN BRAIN ACTIVITY, especially in areas of the brain responsible for inhibiting risky behaviors.
Turn OFF or BLOCK neurotransmitter effects
ex Meloxone (for Heroin overdose)
Stimulant that increases excitement, alertness, activity.
Blocks reuptake of dopamine and other NTs
Stimulates dopamine synapses in the nucleus accumbens & elsewhere by increasing the presence of dopamine in the presynaptic terminal.
Similar effects on serotonin & norepinephrine transporters
Increase accumulation of dopamine in the synaptic cleft
Part of brain associated with fear, anxiety, emotions.
Enhances startle reflex
Important in learning what to fear
Ananda = "Bliss"
Other chemical: (2-AG)
Brain Chemical that binds to cannabinoid receptors
Post-synaptic neuron responds to stimulation by releasing it, to travel back to the presynaptic terminal, where it inhibits further release of neurotransmitter.
Receptors on PREsynaptic neuron. 2-AG tells cell that the POST cell got the message, don't need to send it again
(THC or plant-derived cannibinoids attach to these same receptors & do the same thing)
Anterior: Front/ In front of
Posterior: Back/ Behind
Transporters: Move neurotransmitters (NT) in and out of cell, bring back into PRE-synaptic cell so action stopped & recycled through use
Anterograde Transporters: occurring or performed in the normal or forward direction of conduction or flow
Activates D2 (dopamine2) receptor – it binds & acts like DA
Heroin stimulates mu (opioid receptros) R for analgesia, results in euphoria
It has been tried for a variety of uses including psychiatric treatment of homosexuality in the early 20th century, and more recently in treating erectile dysfunction. Currently, apomorphine is used in the treatment of Parkinson's disease. It is a potent emetic (i.e., it induces vomiting)
PROGRAMMED Cell death.
Period where neurons die
ex Spinal Motorneurons
Cell in spinal chord → muscles in chicks & humans count how many motorneurons in each development stage
in incubation, goes way down after hatching (20k -12k)
Humans: 175k at birth to 125k at 30 weeks
Make lots of motorneurons – live when they make it to target
Other chemicals which are secreted by other neurons/types of cells.
They keep neurons alive
ONE type of glial cell
Star shaped (Astro - star)
Holds blood vessels in place & structures
Wrap around PREsynaptic terminals. Take up ions realeased by axons, releasing them back to axons
Help synchronize activity of the axon, enabling them to send messages in WAVES
Also remove waste material created when neurons die
Autonomic Nervous System
Part of the Peripheral Nervous System (PNS) that controls the heart, intestines, & other organs
Includes Sympathetic nervous system (expends energy) and Parasympathetic nervous system (conserves energy)
Some cell bodies in brain & spinal cord & some clusters along sides of spinal cord
On PRE-synaptic cell
(receptors for yourself)
Gives cell feedback
NT released – also feeds back on it – tells it to WAIT & not fire
Long structure coming out.
Neuron's information sender.
SENDS NEURAL IMPULSE FOR AP (action
Firing/info goes one direction, while chemicals go back & forth throughout the cell, JUST NOT INFO OR ELECTRICAL FIRING but BOTH
Structure between axon & cell body (soma)
WHERE AP STARTS
aka terminal bouton, button.
Ends of axons
After AP comes down, it releases its own chemical/neurotransmitter that affects the next neuron (dendrites of another neuron)
through. Water passes through special protein channels in wall of
2.Molecules that dissolve the fats of the membrane cross. ex vit A & D and antidepressants & psychiatric drugs
3. Active transport: Protein-mediated process expands energy to pump chemicals from BLOOD INTO BRAIN. Pumps glucose & some amino acids
The portion of the brain associated with LANGUAGE PRODUCTION
Broca's Aphasia = Deficit of language production
Maps of cortical areas
Areas 1, 2 and 3 are the primary somatosensory cortex
Area 4 is the primary motor cortex
Area 17 is the primary visual cortex
Areas 41 and 42 correspond closely to primary auditory cortex.
Among most abundant receptors in mammalian brain (scarce in the medulla, which controls breathing & heartbeat. This is why pot doesn't kill people)
Two brain chemicals that bind: Anandamide (AN) & 2-AG
They are located on PREsynapticneuron
When certain neurons are depolarized, they release AN or 2-AG as RETROGRADE transmitters that travel back to incoming axons & inhibit further release of GLUTAMATE or GABA
Normal: AP comes down, NT released , then NT interacts w/ receptors – metabotrophic or ionotrophic (on POST-synaptic cell)
THEN: marijuana like compounds are made & released from POST cell, go BACKAWARDS, interact w/receptor on PRE cell.
Changes way OTHER synaptic process works
The chemicals in marijuana decrease both excitatory & inhibitorymessages from neurons
Cannabinoid Effects: What makes some of them pleasant?
Cannabinoids increase dopamine in the nucleus accumbens INDIRECTLY.
They inhibit GABA release in the ventraltegmental area of the midbrain; a major source of axons that release dopamine in the NA. By inhibiting GABA there, cannabinoids decrease inhibition (INCREASE ACTIVITY) of the neurons that release dopamine in the NA.
Caudal = Posterior/ Tail plane/ farther from the head. Of, at, or near the tail or the posterior end of the body. In the human
case, toward the bottom of the feet (also the "tail" of the spinal cord,
Rostral = Front of the face. Situated toward the oral or nasal region, or in the case of the brain, toward the tip of the frontal lobe.
Cannabinoid Receptor type 1
Located in Central & Peripheral Nervous Systems (CNS) & (PNS)
Located on PRE-SYNAPTIC neuron
Activated by AN & 2-AG, and THC & synthetic forms
G-Protein coupled receptor (large protein family of receptors that sense molecules outside the cell and activate inside signal transduction pathways then cellular responses. They are called seven-transmembrane receptors because they pass through the cell membrane seven times.)
Cell Adhesion Molecules (CAMs)
Used for migration
Neurons inch along using these, to move along pathways
Sturcture containing the nucleus, robosomes,& mitochondria
Metabolic work of the neuron
Covered w/synapses on its surface, like the dendrites
Glial cells important for this – support structures – non neurons neurons inch along these using cell adhesion molecules, move along pathways
Problems along result in conditions: Kallmann's syndrome
Found: women infertile Couldnt smell
Why? Cells couldnt migrate
Cells born in olfactory, migrate to hypothalamus, connect w/ reproductive system
Found: Orphaned reproductive cells in wrong place
Central Nervous System (CNS)
Brain and spinal cord
Cerebral cortex & areas – BILLIONS of neurons (12-15 billion)
Cerebellum (the little brain) (70 billion neurons)