Neuro Flashcards
central nervous system (CNS)
brain and spinal cord
hydrocephalus
abnormal accumulation of cerebrospinal fluid in the ventricles;
due to genetic defect, tumor, traumatic injury, or other factors;
infants and young children: abnormal enlargement of the head;
adults: headaches, loss of balance, impaired cognitive skills, and bladder control problems
spinal cord
carries information between the brain and peripheral nervous system;
consists of 31 segments that are divided into 5 groups;
damage depends on its location and severity - may produce a complete or incomplete injury
5 groups of the spinal cord
from top to bottom: cervical, thoracic, lumbar, sacral, coccygeal
CTLSC
damage to spinal cord at various locations
cervical: quadriplegia (AKA tetraplegia) - loss of sensory and/or motor functions in the trunk, upper limbs, and lower limbs;
thoracic, lumbar, or sacral: paraplegia - loss of sensory and/or motor functions in the lower limbs
complete injury
total loss of sensation and voluntary movement (paralysis)
incomplete injury
loss of sensation but no loss of movement or vice versa or a limited loss of sensation and/or movement
peripheral nervous system (PNS)
afferent nerves (AKA sensory or receptor nerves) that carry information from the sense organs to the CNS;
efferent nerves (AKA motor or effector nerves) that carry information from the CNS to the muscles and glands;
divided into the somatic nervous system and the autonomic nervous system
somatic nervous system
controls the actions of the skeletal muscles;
responsible for voluntary movement;
relays signals from the senses of sight, hearing, smell, taste, and touch
autonomic nervous system
contains nerve fibers that innervate (supply with nerves) the smooth muscles, cardiac muscle, and glands;
regulates primarily involuntary activity (digestive processes, respiration, heartbeat);
changes in level of autonomic arousal are associated with changes in emotionality;
divided into the sympathetic and parasympathetic nervous systems
sympathetic nervous system
mobilizes the body’s resources and prepares the organism for “fight-or-flight” by causing increased heart rate, pupil dilation, increased blood flow to the extremities, inhibition of digestive processes, and conversion of energy stores (fat and glycogen) to glucose
parasympathetic nervous system
deactivates responses that the sympathetic nervous system activates and is active during states of relaxation;
decreased heart rate, activation of digestive and elimination processes, and conversion of glucose to glycogen and fat
neuron
nerve cell;
information processing unit of the nervous system;
brain consists of about 100 billion neurons and about 10 times as many glial cells (also called glia), which provide physical support, nutrients, and a means of cleaning debris in the nervous system
3 main parts of neuron
1) cell body (soma): contains the neuron’s nucleus, mitochondria, and other specialized structures - responsible for most of the cell’s protein synthesis
2) dendrites: short fibers that project outward from the cell body - respond to stimulation from other neurons and carry this information toward the cell body. most neurons have many dendrites.
3) axon: fiber, sometimes quite long, that carries information away from the cell body. most neurons have only one axon, but it usually has several branches (collaterals) with each branch ending in a terminal button
conduction
the electrochemical process by which information is received and processed within a nerve cell
action potential
an electrical impulse that travels quickly through the cell;
operates on the all-or-none principle
all-or-none principle
whenever the stimulation received by a neuron from adjacent cells exceeds a minimum threshold, the resulting action potential is always of the same magnitude;
additional stimulation beyond the minimum threshold does not increase the magnitude of the action potential
Conduction Within Neurons
1) at resting potential: inside of cell is negatively charged while outside is positively charged
2) when cell receives sufficient stimulation from other cells, the electrical balance between the interior and exterior of the cell changes, and the interior of the cell becomes less negative (depolarized)
3) depolarization triggers an action potential
4) speed of conduction within a cell is affected by:
the larger the diameter of the axon, the greater the speed of the nerve impulse
the thicker the myelin, the greater the speed
multiple sclerosis (MS)
muscular weakness, impaired coordination and balance, sensory loss, and blurred or double vision;
loss of myelin
synaptic transmission
transmission of information from one neuron to an adjacent neuron
Transmission Between Neurons
release of a neurotransmitter from the presynaptic cell’s terminal button into the synapse (synaptic cleft), which is the small space between the presynaptic and postsynaptic (adjacent cell that receives neurotransmitter) cells;
the neurotransmitter is released into the synapse when the action potential arrives at the axon’s terminal button where the neurotransmitter is stored;
the released neurotransmitter then spreads across the synapse and binds to receptor sites on the dendrites or cell body of the postsynaptic neuron;
the binding of a neurotransmitter to receptors initiates the electrochemical process that may result in an action potential in the postsynaptic cell
reuptake
occurs when terminal buttons take up the excess neurotransmitter and store it for future use
enzymatic degradation
occurs when enzymes in and around the synapse break down the neurotransmitter into inactive metabolites that are ultimately removed as waste
neurotransmitters
released by neurons and transmit information to other neurons and organ and muscle cells;
can have an excitatory (increase likelihood) or inhibitory (decrease likelihood) effect on postsynaptic cells that an action potential will occur
neuromodulators
increase or decrease the sensitivity of neurons to the effects of other neurotransmitters
types of neurotransmitters
acetylcholine (ACh), dopamine, norepinephrine, serotonin, GABA, glutamate
ANDSGG
acetylcholine (ACh)
cholinergic neurons;
found in the CNS and PNS;
involved in the control of voluntary movement, learning and memory, sexual behavior, and sleep;
acts as an excitatory or inhibitory neurotransmitter depending on the location:
* excitatory effect: junctions between neurons and muscle fibers - causes muscles to contract - defect in ACh transmission to muscle receptors impairs voluntary movement
* inhibitory effect: heart, respiratory muscles - accumulation of ACh paralyzes respiratory muscles;
brain: ACh important in learning and memory - degeneration of ACh in hippocampus and certain areas of the cortex contribute to the memory loss associated with normal aging and Alzheimer’s disease
dopamine
found in several areas of the brain: basal ganglia, limbic system, frontal lobes of the cortex;
involved in movement, learning, mood, and the reinforcing effects of stimulants, opiates, and nicotine;
abnormal levels linked to: depression, Schizophrenia, Tourette’s Disorder, ADHD, Huntington’s disease, and Parkinson’s disease
norepinephrine
plays a role in mood, dreaming, learning, and autonomic responses;
abnormal levels: depression, mania, panic disorder
Serotonin (5-HT)
regulation of anxiety, mood, memory, aggression, pain, sleep, appetite, and sexuality;
low levels: depression, aggression, PTSD, OCD, bulimia;
higher-than-normal levels: Schizophrenia, ASD, decreased appetite associated with anorexia
Gamma-Amino Butyric Acid (GABA)
main inhibitory neurotransmitter in the CNS;
contributes to motor control and regulates anxiety;
abnormal levels: sleep, eating, anxiety, seizure disorders, Parkinson’s disease, and Huntington’s disease;
anti-anxiety drugs work by increasing GABA activity
glutamate
major excitatory neurotransmitter in the CNS;
involved in long-term potentiation (LTP), which is essential for the formation of memories;
abnormal levels: anxiety disorders, mood disorders, Schizophrenia;
overactivity at glutamate synapses (“excitotoxicity”): seizures, stroke, TBI, Alzheimer’s disease, Huntington’s disease, and Parkinson’s disease
endorphins (“endogenous morphine”)
act as neuromodulators;
involved in reducing feelings of pain and producing feelings of pleasure;
believed to contribute to “runner’s high” and the pain-relieving effects of acupuncture and placebos
hormones
endocrine system is comprised of endocrine (ductless) glands that secrete hormones which travel through the bloodstream and influence the functioning of organs
thyroxin
released by thyroid gland;
controls metabolism;
undersecretion: hypothyroidism (slows metabolism, causes reduced appetite), weight gain, lowered heart rate, cold intolerance, decreased sex drive, fatigue, depression, and impaired memory;
oversecretion: hyperthyroidism (AKA Grave’s Disease) - speeds up metabolism and causes increased appetite, weight loss, accelerated heart rate, nervousness and agitation, heat intolerance, insomnia, and decreased attention span
insulin
released by pancreas;
stimulates the uptake of glucose and amino acids into cells
undersecretion: diabetes, if untreated with injections of insulin, leads to high blood glucose levels (hyperglycemia) and causes increased appetite with weight loss, frequent urination, increased thirst, frequent infections, fatigue, apathy, sexual dysfunction, and, eventually, kidney failure, strokes, and heart attacks;
oversecretion: hypoglycemia - intense hunger, weakness, headaches, visual disturbances, palpitations, anxiety, depression, confusion
cortisol
secreted by the adrenal cortex (the outer layer of the adrenal gland);
helps regulate blood glucose levels;
undersecretion: Addison’s disease - muscle weakness, fatigue, low blood pressure, decreased appetite and weight loss, irritability, depression, and darkening of skin pigmentation;
oversecretion: Cushing’s disease - obesity, hypertension, impaired concentration and memory, depression, anxiety, and decreased libido
b/c cortisol is elevated by psychological stress, a cortisol blood, urine, or saliva test is sometimes used to monitor stress level
3 areas of the brain
hindbrain, midbrain, and forebrain
hindbrain
referred to as the brainstem;
contains the medulla oblongata, pons, and cerebellum
midbrain
referred to as the brainstem;
contains the reticular activating system and the substantia nigra
medulla oblongata
contains vital centers that control breathing, heart rate, blood pressure, and digestion;
stimulate coughing, swallowing, salivating, and other reflexive actions;
damage to the medulla is often fatal
pons
connects the two halves of the cerebellum;
involved in relaying sensory and motor information;
plays an important role in arousal, sleep, and respiration
cerebellum
maintains balance, coordinates movements, and controls posture;
damage can produce ataxia (slurred speech, severe tremors, loss of balance)
reticular activating system (RAS)
part of the reticular formation, which is a complex network of interconnected neurons that extends from the spinal cord to the midbrain to relay vital info;
regulates the sleep-wake transition and screens incoming sensory information, especially during sleep;
arouses higher centers in the brain when important information should be paid attention to
substantia nigra
helps control movement;
degeneration of dopamine-producing neurons in this structure contributes to Parkinson’s disease;
plays a role in reward-seeking and addictive behaviors
Forebrain – Subcortical Structures
hypothalamus, thalamus, basal ganglia, and limbic system
hypothalamus
exerts control over the autonomic nervous system and endocrine system via its influence on the pituitary gland;
.(a) maintains the body’s homeostasis by monitoring the body’s internal states and controlling temperature, metabolism, and other functions;
(b) plays a role in the control of many motivated behaviors such as drinking, feeding, sex, aggression, and maternal behavior;
(c) involved in the physical expression of strong emotions, especially rage, fear, and excitement;
contains the suprachiasmatic nucleus and the mammillary bodies
suprachiasmatic nucleus (SCN)
regulates the body’s circadian rhythms primarily through its sensitivity to light and dark;
at night, signals the pineal gland to release melatonin which induces sleepiness; then, at the first sign of daylight, it signals the pineal gland to stop secreting melatonin which alerts the body to wake up
mammillary bodies
play a role in memory;
damage to them and certain areas of the thalamus (often as the result of a thiamine deficiency caused by chronic alcoholism) causes Korsakoff’s syndrome
thalamus
acts as a “central relay station” by relaying incoming sensory information to the cortex for all of the senses except olfaction;
processes information sent between different cortical regions and between the cortex and subcortical regions;
involved in language, memory, and motor activity
basal ganglia
includes the caudate nucleus, globus pallidus, and putamen;
help make up the extrapyramidal motor system - control of posture and gross muscle movements and the coordination of movement on the right and left sides of the body;
process and relay information necessary for the control of voluntary movement, the motor (outward) expression of emotion, and sensorimotor learning;
abnormalities linked to Tourette’s Disorder, Huntington’s disease, Parkinson’s disease, Schizophrenia, mood disorders, OCD, ADHD.
limbic system
“emotional brain”;
mediates the emotional component of behavior;
contains the amygdala, septum, cingulate cortex, and hippocampus
amygdala
integrates and directs emotional reactions, attaches emotion to information it receives from the senses, and mediates defensive/aggressive behavior;
in humans, damage may cause a lack of emotional response (especially fear) to environmental stimuli and an inability to recognize facial and vocal expressions of emotion;
in monkeys, bilateral lesions in the amygdala and anterior temporal lobe produce hypersexuality and Kluver-Bucy Syndrome (reduced fear and aggression, increased docility, altered dietary habits, “psychic blindness”- inability to recognize the significance of objects or situations)
septum
inhibits emotionality;
septal lesions in rats produce septal rage syndrome (hyper-emotionality and vicious behaviors)
cingulate cortex
plays a role in the regulation of emotional responses and pain perception;
believed to play an excitatory role in emotions and in motivating behaviors;
acts as a “satisfaction center” and mediates the feelings of satisfaction that follow eating and sex
hippocampus
memory and learning;
responsible for memory consolidation (the transfer of information from short- to long-term memory);
bilateral destruction of hippocampus, amygdala, and medial temporal lobes produces severe permanent anterograde amnesia;
normal age-related declines in memory and memory loss associated with Alzheimer’s disease have been linked to a degeneration of neurons in the hippocampus
cerebral cortex
involved in a variety of higher-order cognitive, emotional, sensory, and motor functions;
more developed in humans than other animals;
divided into the right and left hemispheres, which look very similar but serve different functions
contralateral representation
the right hemisphere controls the functions of the left side of the body and the left hemisphere controls the functions of the right side of the body;
2 exceptions: olfaction and vision: olfactory information from the right nostril goes directly to the right hemisphere and vice-versa, for each eye, information from the right visual field is transmitted to the left hemisphere, while information from the left visual field is transmitted to the right hemisphere
lateralization of function
for over 90% of right-handers and over 60% of left-handers, the left hemisphere is responsible for written and spoken language, logical and analytical thinking, and the expression of positive emotions (e.g., cheerfulness, euphoria);
the right hemisphere is responsible for understanding spatial relationships, creative and holistic thinking, and the expression of negative emotions (fearfulness, sadness);
(The hemisphere that is responsible for language is referred to as the “dominant hemisphere,” while the other hemisphere is referred to as the “nondominant hemisphere.”)
corpus callosum
fibers that transfer information between the right and left hemispheres, which allows information that is available to the left hemisphere to also be available to the right hemisphere and vice-versa;
if cut, the two hemispheres seem to operate as independent brains
split-brain patients
corpus callosum had been cut to relieve severe epileptic seizures;
surgery didn’t cause noticeable changes in personality or intelligence, but did produce some unusual behaviors:
when a pic of an object was presented to a patient’s left visual field only (so that information was transmitted to the right hemisphere), the patient could not verbally identify the object or pick out the object from several objects with his/her right hand, but the patient could pick out the object with his/her left hand;
in contrast, when a picture of an object was projected to a patient’s right visual field only (so that information was transmitted to the left hemisphere), the patient could verbally identify the object and pick out the object with his/her right hand but was unable to do so with his/her left hand
Forebrain – Lobes of the Cerebral Cortex
4 lobes – frontal, temporal, parietal, occipital
frontal lobe
motor behavior, expressive language, and higher-level cognitive functions;
includes: primary motor cortex, premotor cortex, Broca’s area, prefrontal cortex
primary motor cortex
part of the pyramidal motor system;
involved in the control of voluntary movement;
lesions may produce contralateral motor weakness, paralysis, and/or apraxia
pyramidal motor system
pathway of neurons descending from the motor cortex to the brain stem and spinal cord;
mediates fine, intricate movements and the speed and strength of movement
premotor cortex
anterior to the primary motor cortex;
active during the performance of motor actions as well as during observations of others performing familiar motor actions
Broca’s area
one of the primary language areas of the brain;
in most people, is located in the left frontal lobe;
damage produces Broca’s (expressive) aphasia: deficits in the production of written and spoken language - speak slowly and with great difficulty, can use only a few words (mostly nouns and verbs), have poorly articulated speech, have difficulty repeating phrases, may have anomia (an inability to name familiar objects), and are aware of their deficits
anomia
inability to name familiar objects
prefrontal cortex
essential for higher-order cognitive functions (planning, judgment, problem-solving), certain aspects of memory (working memory and prospective memory), the regulation of emotion, and motor responses;
damage depends on location:
* dorsolateral prefrontal area: “dysexecutive syndrome” - impaired problem-solving, planning, and abstract thinking, distractibility, motor perseveration, and apathy
* medial frontal area: “pseudodepression” - apathy, lack of motivation and spontaneous movement, reduced verbal output
* orbitofrontal area: “pseudopsychopathy” - sexual disinhibition, coarse language, peculiar and facetious sense of humor, inappropriate social behavior, and a lack of concern for others;
abnormal functioning: Schizophrenia, Bipolar Disorder, and ADHD
temporal lobe
auditory processing (including receptive language) and long-term memory;
contains the auditory cortex and Wernicke’s area
auditory cortex
involved in the mediation of auditory input;
damage: auditory agnosia (an inability to distinguish sounds), auditory hallucinations, and other auditory abnormalities
Wernicke’s area
located in the left temporal lobe;
involved in the comprehension of language;
damage: Wernicke’s (receptive) aphasia - trouble understanding language, produce fluent speech that is normal sounding in terms of rate, rhythm, and articulation but makes little or no sense, display anomia and difficulties with repetition, and they are usually unaware of their deficits
H.M.
had a bilateral medial temporal lobectomy;
STM and memory for information acquired long before the operation were intact but unable to acquire new information or recall information that was acquired shortly before the surgery
parietal lobe
contains the somatosensory cortex - processes somatosensory input (touch-pressure, kinesthesia, pain, and temperature) and integrates somatosensory information with other sensory information
somatosensory agnosia
tactile agnosia (an inability to identify objects by touch), asomatognosia (an inability to recognize one’s own body parts), and/or anosognosia (an inability to recognize one’s own symptoms)
apraxia
inability to execute purposeful movements despite normal motor and sensory functions