In humans, most of the brain's neurons are present ____________.
Although neurons die at a rate of about ______________ per day, because of their enormous initial quantity, less than ___% of the original supply is lost by the age of 70.
The creation of new neurons is referred to as neurogenesis, and - in the human brain - has been observed in the ________________ and ______________.
- Caudate nucleus
Most neurons consist of 3 structures:
- Cell body (soma)
Additional neuronal structures/components:
- _______________: Sites where the cell performs its metabolic activities
- _______________: Sites at which the cell synthesizes new protein molecules
- _______________: Consists of channels that transport proteins to other locations in the cell; ribosomes are embedded here and also float freely.
- _______________: System of membranes that prepare neurotransmitters and other substances for secretion
- _______________: Covers the axon and collaterals, acts as an insulator and speeds up the conduction of nerve impulses
- _______________: Hold neurons together, provide neurons with nutrients, remove cellular debris.
- Endoplasmic Reticulum
- Golgi Body
- Myelin sheath
- Glial cells (make up the myelin sheath)
In its resting state, the inside of the neuron is ____________ charged relative to the outside of the cell. When the dendrites receive sufficient stimulation from other cells, this balance is altered; sodioum channels open, which allows ___________ charged ions to enter the cell and create a state of ________________.
- Negatively charged
- Positively charged
Depolarization results in an _________________, which is an electrical impulse that travels quickly through the cell. This is followed by __________________, in which sodium channels close and potassium channels open, which allows positively charged potassium ions to leave the cell.
- Action potential
Action potential operates on the _________________ principle, which means that, whenever the stimulation received by a neuron exceeds a given threshold, the resulting action potential will always be of the same intensity.
Acetylcholine (ACh) is found throughout the peripheral and central nervous systems and acts on two different types of receptors - ______________ and ______________.
ACh is released into the neuromuscular junction, where it causes muscles to _____________.
______________________ is an autoimmune disorder that attacks ACh receptors at neuromuscular junctions, resulting in profound weakness of the skeletal muscles.
In the CNS, ACh is involved in REM sleep, the regulation of the _____________ cycle, and learning/memory.
Degeneration of cholinergic (ACh) cells in the _____________ and other areas that communicate directly with the hippocampus is believed to underlie the the memory deficits associated with _____________ disease.
- Entorhinal cortex
Bonus: Recognition of the impact of ACh on memory led to the use of cholinesterase inhibitors to slow memory declines in patients with this disorder. They reduce the breakdown of ACh and include:
- Tacrine (Cognex)
- Donepezil (Aricept)
- Galantamine (Reminyl)
- Rivastigmine (Exelon)
Dopamine, epinephrine, and norepinephrine are classified as __________________.
The research suggests that oversensitivity to or excessive dopamine in the caudate nucleus contributes to __________________.
Degeneration of dopamine receptors in the substantia nigra and nearby areas underlies the tremors, muscle rigidity, and other motor symptoms of __________________.
Elevated levels of dopamine in the mesolimbic system (areas in the midbrain and limbic system) ahve been implicated in the reinforcing action of stimulants, _________, ___________, and nicotine.
Bonus: Cocaine blocks the reuptake of dopamine at synapses in this area of the brain, while nicotine stimulates its release.
Norepinephrine plays an important role in mood, _____________, dreaming, _____________, and certain autonomic functions.
The ____________________ predicts that some forms of depression are due to lower-than-normal levels of norepinephrine.
______________ levels of Serotonin (5-HT) contribute to Schizophrenia, Autistic Disorder, and food restriction associated with Anorexia Nervosa, while __________ levels play a role in aggression, depression, suicide, Bulimia Nervosa, PTSD, and OCD.
_____________________ is an inhibitory neurotransmitter and plays a role in eating, seizure, and anxeity disorders, motor control, vision, and sleep.
Gamma-Aminobutyric Acid (GABA).
______________ levels of GABA ahve been linked to anxiety disorders; benzodiazepines and other CNS depressants reduce anxiety by ______________ the effects of GABA.
Degeneration of cells that secrete GABA in the basal ganglia contributes to the motor symptoms of _________________.
Glutamate acts as an ________________ neurotransmitter in many areas of the brain.
Glutamate plays a role in _____________________, a brain mechanism that is believed to be responsible for the formation of long-term memories.
__________________ glutamate receptor activity ("_____________") can lead to seizures and may contribute to stroke-related brain damage, Huntington's disease, Alzheimer's disease, and other neurodegenerative disorders.
___________________ are inhibitory neuromodulators that lower the sensitivity of postsynaptic neurons to neurotransmitters.
Endorphins (endogenous morphines).
One theory is that endorphins' analgesic properties are due to their ability to prevent the release of _____________, which is involved in the transmission of pain impulses.
The Peripheral Nervous System is comprised of 3 components:
- Somatic Nervous System
- Parasympathetic Nervous System
- Sympathetic Nervous System
The Parasympathetic Nervous System and Sympathetic Nervous System together comprise the __________________ Nervous System.