Test 1 Flashcards
What are the two categories of cells of the nervous system? What do they do?
Neurons: receive and transmit information
Gila: exchange chemicals with adjacent neurons, do NOT transmit over long distances, Support, protect, and neurish neurons
What is notable about the plasma membrane of nerve cells?
- separate inside and outside of cell
- small uncharged molecules move freely across: H2O, O2, CO2
- charged ions pass through protein channels: Na, K, Ca, Cl
What are the four major structures of a neuron and what do they do?
- Dendrites: branching fibers, information receivers (many)
- Soma: cell body, nucleus, ribosomes, mitochondria
- Axon: thin fiber, information sender (one)
- Presynaptic terminals (end bulbs): swelling at the tip of axon, axon releases chemicals at synaptic gap
What are the four important structures in the neuron soma?
- Nucleus structure that contains chromosomes
- Mitochondria: powerhouse of the cell
- Ribosomes: site of protein synthesis
- Endoplasmic Reticulum: network of thin tubes that transport newly synthesized proteins
What are the important structures, actions, and a disease associated with the axon?
- Mylin sheath: covers the axon: insolates, and increases action potential speed
- Nodes of Ranvier: interruption in myelin sheath/ short unmyelinated sections, facilitates rapid conduction of nerve impulses
- Saltatory conduction: “jumping” of action potential/impulse from node to node along myelinated axon
- Multiple Sclerosis: loss of myelin along axon preventing movement (propagation of APs down an axon
What are the types of neurons?
Sensory
- afferent: brings info to structure
Motor
- efferent: brings info away from structure
Interneurons
What is muscle memory?
A clearer path in the brain made by repitition
What are the facts about glia cells?
(Greek for Glue)
- 10th of the size of a neuron
- 10X more numerous than neurons in the brain
- Takes up same space as neurons
What are Astrocytes?
(Star-shaped) wraps around synaptic terminals
- Synchronize axon activity enabling them to send messages in waves
- Removes waste material created when neurons die
“Stars” star-shaped, are synchronized in the sky
What are Oligondendrocytes?
- Surrounds and insulates certain axons in brain & spinal cord
- Builds myelin sheaths around axons in the brain and spinal cord
“legal”- attorney brain & backbone
What are Schwann cells?
- Surrounds and insulates certain axons in the periphery of the body
- Builds myelin sheaths around axons in the periphery of the body
What are Radial Glia?
During embryonic development
- Type of astrocyte that guides migration of neurons
- Type of astrocyte that guides the growth of axons & dendrites
Radial tires migrate
What are microglia?
- Proliferate in areas of brain damage
- Removes toxic materials
Microfiber towel clean-up
What is the blood-brain barrier?
***
- Endothelial cells in the brain that are so tightly joined that most molecules cannot pass between them
- Keeps most viruses, bacteria and harmful chemicals out of the brain
Why do we need a blood brain barrier?
- Damaged cells do not regenerate
- Need to minimize the risk of brain damage
What molecules can cross the Blood Brain Barrier?
1) Small uncharged molecules:
- O2, CO2, H2O
2) Molecules that dissolve in fats of capillary wall
- psychiatric dugs
- abused/ street drugs (nicotine, heroine, marijuana)
- Vitamin A & D
What is Active Transport?
A protein-mediated process that pumps necessary and useful chemicals from the blood to the brain
What chemicals pass through the blood-brain barrier by active transport?
- Glucose
- Amino acids
- Thiamine/other vitamins/iron
- Certain hormones
Why might alcoholics have a vitamin B1 (thiamine) deficiency?
- Poor diet
- Impaired absorption
What does a vitamin B1 deficiency lead to?
- inability to use glucose
- leading to neuron death
- leading to Korsakoff’s Syndrome
What is Korsakoff’s Syndrome?
Severe memory impairment which might cause the person to confabulate
What does it mean to confabulate?
Making up information to fill in gaps
What is a nerve impulse?
- Electrical message transmitted down the axon
- Exchange of chemicals between the inside and outside of cell
What is electrical polarization?
- Difference in electrical charge between two locations
- Inside of membrane has slightly negative electrical potential with respect to the outside
What is the concentration gradient?
- Na+: 10x more concentrated outside the membrane
- K+: 20x more concentrated inside the membrane
What is selective permeability?
Some molecules pass through the membrane more freely than others
What molecules cross in both directions of the membrane at all time?
O2, CO2, Urea (NH4), H20
What molecules cross through protein channels?
K, Na, Ca Cl
What occurs at the resting potential?
K+, Cl+ channels open so they pass slowly
Na channels closed
What is the sodium-potassium pump?
- Actively pumps 3 Na+ out & 2 K in (PumpKin)
What is hyperpolarization?
Increased polarization caused by the negative change inside the axon increasing (-70mV becomes -80mV)
What is depolarization?
Reduced polarization toward zero. This occurs when the negative charge inside the axon increases.
What is the threshold of excitation?
Any stimulation beyond a certain level produces a sudden, massive depolarization which must be reached for an action potential to occur
What is action potential?
Rapid depolarization and slight reversal of the usual membrane polarization. Occurs when depolarization meets or goes beyond the threshold of excitation
What is the all or none law?
Amplitude and velocity of action potential is in depended of the intensity of the stimulus which is indicated by the frequency of the signal
- The action potential will go if the threshold is reached, going way over the threshold will not make a difference
What is the refractory period?
At the peak of the action potential the sodium channels shut so no new action potential can generate for about a millisecond “absolute refractory period”
- Then sodium channels relax and cell is hyperpolarized for 2-4ms “relative refractory period”
- depends on Na and K channels
- prevents action potential moving in opposite direction
What is the propagation of action potential?
- begins at the axon hillock of a motor neuron
- regenerated due to sodium ions moving down the axon depolarizing adjacent areas of the membrane (moving like a wave)
- temporarily positively charged compared to other areas
- Thicker axons (more myelin) –> faster velocities
What is the sequence of chemical events at a synapse?
1) The neuron synthesizes chemicals that serve as neurotransmitters
2) AP travels down the axon. At the presynaptic terminal, an AP enables calcium to enter the cell, releasing neurotransmitters into the synaptic cleft.
3) The neurotransmitters attach (bind) to receptors altering the activity of the postsynaptic neuron
4) The neurotransmitters separate from their receptors
5) Reuptake of the neurotransmitter–meaning that the NT may be taken back into the presynaptic neuron to be recycled–or just diffuse away
6) Some postsynaptic cells release retrograde transmitters to control the release (slow it down) from presynaptic cell
What condition does deficient acetylcholine cause?
Alzheimer disease
Symptoms: Memory loss, depression, disorientation, dementia, hallucinations, death
What condition does deficient norepinephrine and/or serotonin cause?
clinical depression
Symptoms: debilitating, inexplicable sadness
What condition does excess GABA leading to excess norepinephrine and dopamine cause?
epilepsy
Symptoms: seizures, loss of consciousness
What condition does deficient GABA cause?
Huntington disease
Symptoms: personality changes, loss of coordination, uncontrollable dancelike movements, death
What condition does Excess serotonin cause?
Hypersomnia
Symptoms: excessive sleeping
What condition does deficient serotonin cause?
insomnia
Symptoms: Inability to sleep
What condition does excess norepinephrine cause?
mania
Symptoms: Elation, irritability, overtalkativeness, increased movements
What condition does deficient acetylcholine receptors at neuromuscular junctions cause?
myasthenia gravis
Symptoms: progressive muscular weakness
What condition does deficient dopamine cause?
Parkinson disease
Symptoms: Tremors of hands, slowed movements, muscle rigidity
tardive dyskinesia
Symptoms: uncontrollable movements of facial muscles
What condition does deficient GABA leading to excess dopamine cause?
schizophrenia
Symptoms: Inappropriate emotional responses, hallucinations
What condition does excess dopamine cause?
sudden infant death syndrome
Symptoms: baby stops breathing, dies if unassisted
What is the synapse?
The gap between the two neurons where a specialized type of communication occurs
What did Sherrington do?
- Labeled the synapse
- Did experiments on reflexes
What is a reflex?
Automatic muscular responses to stimuli
What is a reflex arc?
The circuit from sensory neuron to muscle response
- Sensory neuron excites interneuron/intrinsic neuron which excites motor neuron
What is temporal summation?
Several impulses from one neuron over time can have a cumulative effect
What is spatial summation?
Impulse from several neurons at separate locations at the same time can have a cumulative effect
What is inhibition?
“break” that can suppress excitatory response
What is EPSP?
Excitatory Post Synaptic Potential
- Sodium gates open making AP more likely
What is IPSP?
Inhibitory Post Synaptic Potential
- Potassium or Chloride gates open making an AP less likely
What did Elliott do?
Studies adrenaline
What did Loewi do?
Discovered that synapse operates by releasing chemicals (frog heart)
What are Neurotransmitters? What are the four types?
Chemicals released by one neuron at the synapse affecting other neurons
- Acetylcholine
- Amino Acids
- Monoamines
- Peptides
What is the acetylcholine neurotransmitter?
- One member family
- Synthesized from choline found in eggs, milk, cauliflower, and peanuts
What are the amino acid neurotransmitters?
- Glutamate (excitatory)
- GABA (inhibitory
– chemical brothers - Others: glycine, aspartate
- Tryptophan: Found in turkey and the carbs increases entry to the brain making you tired
What are the monoamine neurotransmitters?
- Indolamines: serotonin
- Catecholamines
– Dopamine
– Norepinephrine
– Epinephrine
What are the Peptide neurotransmitters?
- Endorphins
- Substance P
- Neuropeptide Y
- Others
What is the effect of cannabinoids at the synapse?
(marijuana)
Excites negative feedback receptors on presynaptic cells
- altered sensory experiences dec pain, inc appetite
What is the effect of opiates at the synapse?
(methadone, heroine, morphine)
- stimulates endorphin (provides relief from pain + even euphoria) receptors
- relaxation, dec pain, euphoria
What is the effects of nicotine at the synapse?
- Stimulates nicotine-type acetylcholine receptor which increases dopamine release
- Stimulate (initial kick of adrenaline) & sedative (calming)
What is the effect of methylphenidate at the synapse?
(Ritalin)
- Blocks reuptake of dopamine (prolonging dopamine effects)
- Stimulant excitation, termination (sensation of bugs crawling on skin), facial flushing
What is the effect of cocaine at the synapse?
- Blocks reuptake of dopamine (prolonging dopamine effects)
- Stimulant: restless, irritability anxiety
What is the effect of MDMA at the synapse?
(Ecstasy)
- releases dopamine & serotonin (prolonging dopamine effects)
- dec dose = stimulant
- inc dose = sensory distortion
What is the effect of hallucinogens at the synapse?
(LSD)
- stimulates serotonin receptors (prolonging dopamine effects)
- distors perception
What is the effect of amphetamine at the synapse?
(Adderall, methamphetamine)
- blocks reuptake of dopamine (prolonging dopamine effects)
- stimulant: excitement, alertness, inc mood, dec fatigue
What happens with a caffeine withdrawal?
Headaches, irritability, sleepiness, constipation, lack of concentration
What are the effects of caffeine?
1) Increase heart rate, but constricts blood vessels in brain - decreasing blood supply
2) Interferes with effects of adenosine (neurotransmitter) [acts as special receptor on the presynaptic terminal - inhibiting the release of dopamine & acetylcholine]
3) Thus, by blocking the inhibitory effects of adenosine, caffeine increases the release of dopamine & acetylcholine
What is the meaning of the neurotransmitter?
It depends on the receptor: excitatory, inhibitory, or no effect
What are the two major effects of neurotransmitters attaching to the receptors?
- Ionotropic: Attachment causes immediate opening of an ion gate (e.g. glutamate opens Na gate)
- Metabotropic: relies on 2nd messenger
– 1st messenger (neurotransmitter) carries the message to the post synaptic cell
– 2nd messenger: carries messages to areas within the cell - Metabotropic slower, lasts longer than ionotropic
What is the difference between a neurotransmitter and a hormone?
- Neurotransmitters: conveys messages an exclusive receiver Phone call
- Hormone: conveys message to any receiver tuned in (travel further) Radio Station
What do neuromodulators do?
An intermediate between neurotransmitters & hormones
- Alters (modulates) the effects of the neurotransmitter
- Affects only the closest cell, closest to target cell (like hormone)
- Released in smaller volumes
What is an antagonist?
A chemical that blocks (inhibits) the effects of a neurotransmitter
What is an agonist?
A chemical that increases (mimics) the effects of a neurotransmitter
What is affinity?
How strongly the drug binds or attaches to the receptor
What is efficacy?
The tendency of a drug to activate a receptor
What is acetylcholinesterase?
An enzyme that breaks down acetylcholine into acetate & choline
* inactivating it
