Overview and Evaluation of the Nervous System Flashcards
In humans, most of the brain’s neurons are present ____________.
At birth.
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.
- 10,000
- 2%
The creation of new neurons is referred to as neurogenesis, and - in the human brain - has been observed in the ________________ and ______________.
- Hippocampus
- Caudate nucleus
Most neurons consist of 3 structures:
- Dendrites
- Cell body (soma)
- Axon
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.
- Mitochondria
- Ribosomes
- 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
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
- Repolarization
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.
All-or-none.
Acetylcholine (ACh) is found throughout the peripheral and central nervous systems and acts on two different types of receptors - ______________ and ______________.
- Muscarinic
- Nicotinic
ACh is released into the neuromuscular junction, where it causes muscles to _____________.
Contract.
______________________ is an autoimmune disorder that attacks ACh receptors at neuromuscular junctions, resulting in profound weakness of the skeletal muscles.
Myasthenia Gravis.
In the CNS, ACh is involved in REM sleep, the regulation of the _____________ cycle, and learning/memory.
Sleep-wake.
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
- Alzheimer’s
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 __________________.
Catecholamines.
The research suggests that oversensitivity to or excessive dopamine in the caudate nucleus contributes to __________________.
Tourette’s Disorder.
Degeneration of dopamine receptors in the substantia nigra and nearby areas underlies the tremors, muscle rigidity, and other motor symptoms of __________________.
Parkinson’s disease.
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.
- Opiates
- Alcohol
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.
- Attention
- Learning
The ____________________ predicts that some forms of depression are due to lower-than-normal levels of norepinephrine.
Catecholamine hypothesis.
______________ 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.
- Elevated
- Lower
_____________________ 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.
- Low
- Enhancing
Degeneration of cells that secrete GABA in the basal ganglia contributes to the motor symptoms of _________________.
Huntington’s disease.
Glutamate acts as an ________________ neurotransmitter in many areas of the brain.
Excitatory.
Glutamate plays a role in _____________________, a brain mechanism that is believed to be responsible for the formation of long-term memories.
Long-term potentiation.
__________________ 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.
- Excessive
- “Excitotoxicity”
___________________ 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.
Substance P.
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.
Autonomic.
Fill in the blanks for the Central Nervous System:
- ________________
- Brain
- Hindbrain
- _____________
- Forebrain
- Spinal Cord
- Midbrain
What are the 3 structures that form the Hindbrain?
- Pons
- Medulla
- Cerebellum
What are the 3 structures that form the Midbrain?
- Superior and Inferior Colliculi
- Substantia Nigra
- Reticular Formation (RAS)
The Forebrain is comprised of the ________________ Structures and the ___________________.
- Subcortical Structures
- Cerebral Cortex
What are the 5 subcortical structures?
- Thalamus
- Hypothalamus
- Basal Ganglia
- Amygdala
- Hippocampus
What are the 4 Cortices?
- Frontal Lobes
- Parietal Lobes
- Temporal Lobes
- Occipital Lobes
Nerve fibers in the superior portion of the spinal cord - the _____________ - carry sensory (afferent) messages, while fibers in the inferior portion - the ________________ - transmit motor (efferent) messages.
- Dorsal horns
- Ventral horns
The spinal cord is segmented into five groups (top to bottom):
- Cervical
- _______________
- Lumbar
- _______________
- Coccygeal
- Thoracic
- Sacral
Damage at the cervical level of the spine is likely to result in _______________.
Quadriplegia (also known as tetraplegia).
Damage to the spine at the thoracic level causes _____________.
Paraplegia.
What are the three membranes (meninges) encasing the brain and spinal cord (innermost to outermost)?
- Pia Mater
- Arachnoid
- Dura Mater
The Cerebrospinal Fluid (CSF) fills the _________________, or space between the arachnoid and pia mater, the central canal of the spinal cord, and the four _________________.
- Subarachnoid space
- Cerebral ventricles
__________________ is caused by an obstruction of the flow of CSF that leads to a build-up of fluid and enlargement in the ventricles.
Hydrocephalus.
The Peripheral Nervous System (PNS) consists of ___ pairs of cranial nerves and ___ sets of sensory and motor nerves.
- 12
- 31
The development of the human brain involves ___ main stages.
5.
- ______________________: New cells are produced inside the neural tube beginning when the embryo is about 2.5 weeks old.
Proliferation.
- ___________________: Immature neurons migrate to their final destination in the brain beginning at about 8 weeks. Once these cells reach their destination, they begin to aggregate with other cells to form the structures of the brain.
Migration.
- ______________________: Neurons initially look very much like other cells of the body but, following migration, develop axons and dendrites.
Differentiation.
- ____________________: The axons of some neurons myelinate, which occurs when glial cells form an insulating sheath around the cell’s axons. Much myelination occurs postnatally.
Myelination.
- ____________________: The timing of this stage (formation of synapses) depends on the specific area of the brain, but most occurs postnatally. This process appears to be influenced by both endogenous (e.g., genetic) and exogenous (e.g., experience) factors.
Synaptogenesis.
______________________: The process of pruning over-produced neurons during prenatal development and for several years following birth; this form of cell death is thought to “fine-tune” brain development.
Apoptosis.
Computed tomography (CT) and magnetic resonance imaging (MRI) are ________________________ that provide information on the physical structure of the brain.
Structural neuroimaging techniques.
A ____________ is useful for diagnosing various pathological conditions such as tumors, blood clots, and multiple sclerosis.
CT scan (also known as a CAT scan - Computerized Axial Tomography).
An _____________ has several advantages over a _______________: It has better resolution and provides more detailed images, provides images at any angle, and generates 3D pictures of the brain.
- MRI
- CT
Positron-emission tomography (PET), single proton emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI) are ______________________ that provide information on brain activity.
Functional Neuroimaging Techniques.
The images produced by a _________________, in which the individual is injected with a radioactive tracer substance that is taken up by active brain cells, provide information on regional cerebral blood flow, glucose metabolism, and oxygen consumption, which are presumed to correlate with level of neural activity. These scans are used to assess cerebrovascular disease, Alzheimer’s disease and other forms of dementia, Schizophrenia, and other disorders, and to identify brain areas that are active during the performance of ordinary tasks and the experience of ordinary emotions.
PET scan.
In comparison to ___________ and ____________, _____________ provides information on brain activity (blood oxygenation) and provides images that have better temporal and spatial resolution.
- PET
- SPECT
- fMRI
