Exam 1 Flashcards
Nervous System
- CNS (brain & spinal cord)
- Peripheral NS:
– (ANS) Sympathetic NS & Parasympathetic NS - Somatic NS
– Muscle, skin, organs - Enteric NS
–Gastrointestinal tract
–“Gut-brain”
• Neurotransmitters and neurons that help coordinate the digestion of food
• Muscle coordinated movements to move digested food to the small intestine for absorption and then moves into large intestine/ movement has to be coordinated by neurons
• Serotonin – 80-90% is in Enteric Nervous System
o Reason why people who experience anxiety often have stomach aches
Brainstem: parts and function
o Consists of: Medulla –> Pons –> Midbrain
Ascending and descending tracts* between spinal cord and thalamus, cerebellum, cortex
o Reticular activating system* (RAS)
Neurons located throughout brainstem
Activates thalamus, hypothalamus, neocortex for arousal* from sleep
Help keeps one alert* during day
The midbrain* portion is particularly critical* for cortical activation^
Injury* leads to problems* with arousal, alertness, coma*
oAxons* from specialized clusters of cell bodies* project to the brain, spinal cord, and autonomic nervous system (ANS)
Release neurotransmitters* to regulate respiration, ANS (e.g. cardiovascular activity) consciousness, alertness
o Some axons from cell bodies throughout the brainstem release serotonin^ (5-HT)
o Other axons from cell bodies in the mesencephalon (midbrain) release dopamine^ (DA)
o Other axons from cell bodies in the pons release norepinephrine^ (NE)
o Other axons from cell bodies in the upper brainstem release acetylcholine^ (ACh)
Cerebellum
Cerebellum’s function?
o Nonconscious modulation of complex movements, posture, muscle tone, gait, visuomotor coordination*
o Performs error correction* of movements
o Speeds up* movements, prepares motor systems
o Acquiring/maintain smooth, coordinated motor skills
ANS: Viscera (internal organs) are influenced by two interdependent systems
Neural: uses neurotransmitters, synapses
- Responses are faster to develop, shorter-term, reach limited* number of cells
Endocrine: uses hormones via bloodstream
- Responses are slower to develop, more prolonged, reach greater number of cells
- Responses travel through hormones which is why
responses are slower and travels to a greater amount of cells/ bloodstream can go to every cell in the body
ANS: Endocrine and Neural systems
o Neural and Endocrine system both involved in neuro-conscious “automatic” and homeostatic* processes, including:
Cardiovascular* - heart beats, blood pressure, exc.
Respiratory- how fast and deeply we breathe
Digestive
Urinary*
Reproductive*
o Neural and Endocrine both controlled by the CNS (primarily hypothalamus) also amygdala
o Neural and Endocrine both are affected by emotional factors and sensory input* from inside and outside the body
ANS* is the neural* system
• Innervates smooth muscle, cardiac muscle, glandular epithelium
Sympathetic Nervous System (SNS)*
• “Fight or flight” – extreme excitement, exertion, stress* causes global* activation of SNS*
o Increase* release of NE* (stress hormone) in tissues
• Increases:
o Rate ND STRENGTH of heart beating*
Pt may feel this (palpitations* )
o Blood pressure*
o Blood flow to skeletal muscles*
o Blood glucose level*
o Sweating*
o Pupil size*
• Concurrently decreases*
- Gut mobility
- Digestive gland selection
- Blood flow to abdominal viscera, skin
- SNS acts in a global manner (all aroused at once)
Parasympathetic Nervous System
• “Rest and digest”
• Increase* release of ACh* in tissues
• Increases* food digestion* by increasing gut
mobility and digestive gland secretion
• Slows heart rate*
- PNS works in a localized (the entire system does not need to work all at once/ at the same time)
SNS and PNS
the SNS and PNS have opposite* effects
o Overall balance* is critical
o Each must become temporarily dominant* for a specific situation
• Emotional dysfunction* may cause/worsen disease* if SNS* is hyperactive and chronic*
Neurons
• Neurons*: basic signaling unit, information processors, computation devices, CPUs
Gila (gilal cells)
Support cells (structural, functional support) for neurons
Neurotransmitters* (NTs)
Made inside neurons
o Neurons make NTs and release at a proper time
o NT does not cross the membrane that surrounds cells
• A neuron is named after the main NT of that neuron
o i.e. dopaminergic neuron makes and releases dopamine (NT)
Steps in NT function:
- NT is synthesized* and stored in synaptic vesicles* until needed
- NT is released* when an action potential reaches the terminal
- Activation* occurs when an NT binds to a specific binding site on a specific receptor* (protein in postsynaptic membrane)
This causes one of two events:
• 1. Excitation
• 2. Inhibition
Deactivation*
o Primarily by two mechanisms- Reuptake* is the most common* type
– NT * is taken by a presynaptic transporter*
(“reuptake pump”)
– Most is stored in vesicles for reuse and to protect
from enzymatic degradation - Enzymatic degradation* (monoamine oxidase)
- Reuptake* is the most common* type
Resting Potential
• At rest* a neuron has an electrical potential (charge across its membrane) of -70 mV (inside negative relative to outside) due to unequal distribution of charged particles (ions, proteins)
• It is said to be polarized*
• Resting potential* created by semipermeable
membrane
o Hard for Na+* (sodium) to pass into neuron (but some
leak)
o Proteins (mostly with a negative charge) are kept
inside due to size and charge
o K* (potassium) can pass freely through channels
o Na-K pump exchanges three Na* from inside for
every two K* from outside
o Result is 10 times more Na* outside than inside
Synapse
Synapse^: site of functional contact Consists of: presynaptic membrane with active zone Synaptic cleft – space between neurons Postsynaptic membrane with receptors
NTs influence neurons via …
receptors
Two of the most common families of receptors are…
ionotropic receptors (ligand-gated ions) and Metabotropic (G-protein linked receptors)
Ionotropic (ligand-gated ion channels) receptors
o Allow ions* to move across the membrane through a channel that opens when NT binds
Rapid change in membrane potential (msecs)
o Mediate fast* behavior
o May be excitatory* or inhibitory*
Graded potentials
- is a gradual change in the resting potential membrane
EPSP
•Excitatory^ postsynaptic^ potential^ (EPSP*)
- Neuron becomes depolarized; Excited and closer to firing threshold of -50mV
Graded potential: excited
Gradual change in the resting potential membrane
When excited…
Charge becomes less^ negative^ or depolarized^; is excited^
• Why excited? Because now closer* to firing threshold* of -50 mV^
Graded potential: inhibited
If CI- or K+ channels open, CI-enters or K+ exists…
Change becomes more^ negative^, or hyperpolarized^; is inhibited^
Now further from firing threshold -50 mV^
o Graded potentials occur in msecs for fast changes
IPSP
Inhibitory^ postsynaptic^ potential
- Neuron becomes hyperpolarized; Inhibited and further from firing potential -50 mV
Action Potential
Action Potential^; “firing” of the neuron
• If summation* at the axon hillock (where axon begins) reaches the firing threshold* (-50 mV), it fires^ (action potential occurs)
• At firing threshold, voltage sensitive Na+ channel* (VSSC) opens – even more Na+ enters
o Changes potential to +30 mV
o Voltage-sensitive K+ channel opens slowly
• When potential reaches +30 mV, Na+ channel
closes and K+ channel is fully opened
o Let K+ exit, which reverses potential—causes slight
hyperpolarization
o Then back to resting potential
- The amplitude^ (distance from bottom to peak) is constant^ for all action potentials (all-or-none)
- Occurs quickly and lasts about 5 msecs
Propagation
• Na+ that came into the neuron during action potential depolarizes the adjacent area
o Triggers its channels to open
- The action potential is then propagated* (action signals travels down; “domino effect”) along entire axon
- When the impulse reaches its terminal, it releases NT, and the whole process may be continued in the next neuron
Saltatory conduction
- When action potential “jumps” from node to node/ faster propagation
o Is possible because myelin prevents ions from crossing membrane – so no action potential
o Through myelinated portions, “current” (flow of Na+) is passively transmitted extremely fast
o At nodes of Ranvier, there is no myelin but rich in voltage sensitive channels
Where action potential is regenerated
o Greatly increases speed
Action Potential - Amplitude and Intensity
• Amplitude* of action potential is constant* and cannot provide information about intensity
Intensity^ is provided by…
Frequency^ of action potentials because a more intense stimulus increases the probability that firing thresholds will be reached and that action potentials will be generated
Duration of stimulus is reflected in the period over which action potentials occur (total number)
o The brain* processes patterns* of these action potentials*
True or False: Intensity is detected in the CNS by the magnitude of action potentials (e.g., a louder noise is detected by larger action potentials).
False
The term propagation instead of travels down is preferred to describe the movement of action potentials down the axon because…
It conveys that the action potential is being continually regenerated at points along the axon
“Saltatory conduction” refers to
Faster propagation of an action potential, as it seems to “jump” from one node to the next
True or False: Action potentials vary according to sensory modality or motor output (e.g., visual stimuli cause different types of action potentials vs. auditory stimuli).
False
NTs that bind to Ionotropic Receptors
• NTs that generally bind to ionotropic* RECEPTORS Are fast acting*
o Amino-acids
- Glutamate (glutamic acid): Glu
- Gamma-aminobutyric acid: GABA
o Acetylcholine (via nicotinic receptors): ACh
• Glutamate^ (Glu^) generally excites^ neurons
Most common excitatory* NT
- Gamma-aminobutyric acid (GABA) generally inhibits^
neurons
- Most common inhibitory* NT
• Acetycholine* (ACh)
- Used for neuromuscular* transmission
When ACh is released at the neuromuscular junction, it binds to nicotinic receptors on muscle cells, leading to muscular contraction
Hormones
Chemicals produced by endocrine glands that travel to target cells via the bloodstream
Hierarchical control of hormones
- Hypothalamus – main part of the brain that is in charge of all of our hormones ( full control of endocrine system)
- Pituitary gland
- Endocrine glands
- Target cells affected by hormones
Fun Fact: Almost every cell in the body can be controlled by various hormones
Hypothalamus – Controls* over hypothalamic-hormone activity
• Feedback* (negative feedback loop - brain detects hormone to stop overproduction of hormone)
• Limbic system, frontal lobes also control hypothalamic hormone activity
o Sight, sound, thought of baby can trigger
oxytocin release, milk ejection; but anxiety can
inhibit release
• Experience* (i.e. neurons that release oxytocin increase in size in mother)
Pituitary Gland
The pituitary gland* (“master gland”) releases hormones that causes other glands to release hormones.
Hormones such as:
• Adrenocorticotropic hormone (ACTH)* causes adrenal glands to release hormones. Like cortisol.
• Thyroid stimulating hormone (TSH, thyrotropin) causes thyroid gland to release thyroid hormone
- Critical for general body metabolism
• Folicle stimulating hormone (FSH) and luteinizing hormone (LH) causes gonads to release androgens and estrogens
- Important for release of reproductive hormones
Oxytocin
Growth hormone:
- Uterine contractions during labor, milk letdown, during breastfeeding
- Bonding during coitus (in females and in males) and between mother and infant
- Prolactin for milk production
- Antidiuretic hormone (ADH, vasopressin) to conserve water to prevent dehydration while breastfeeding
Human Growth Hormone
Hormone that promotes growth
Testosterone*
Reproductive hormone:
• Produces male* body and brain
• May increase aggressive* behavior
• Increases libido* in males, females
Estrogens*
• “Estrogen” usually refers to estradiol or loosely to
estrogens as a group
• Cause female body changes at puberty
• Control menstrual cycles; regulate many aspects of
pregnancy, birth; stimulate lactation
Estrogen Changes
Estrogen level shift* significantly during a female’s life
• Rise and cycle from puberty until menopause
• Rise dramatically during pregnancy
• Plummet postpartum
• Erratic during perimenopause (37-55)
• Minimal during menopause
Estrogen and Emotions
Depression* mirror these changes in estrogen*
• Depression increases significantly during puberty
•.May worsen during luteal phase of cycle
o Luteal phase – second half of a woman’s menstrual cycle. 15th day of a 28 – 30 day cycle
o Just before menses particularly estrogen drops significantly
• Major risk during postpartum after abrupt fall in estrogen
o Risk for depression, psychosis, mania
• Risk during perimenopause
• Frequency in depression is 2 – 3 times higher in females vs. males in childbearing years
- But is same before puberty and after menopause
Hormone Effects
Estrogen* profoundly affects the body* and brain*
• Activates genes* to synthesize trophic factors* (molecules that help neurons grow/ nurture neurons) , receptors* (protein receptors), and enzymes* (also protiens)– that synthesize and metabolize NTs in females
• Affects neurotransmitters: 5-HT, NE, DA – all involved in depression*
• Females do better on…
- Spatial tasks when estradiol and progesterone are at a lower level (just before and during menses)
- Better on verbal and motor tasks when these hormones are at highest level (from ovulation until menses)
• Males with low levels of testosterone have impaired verbal memory and attention
- But males with very low levels are comparatively less impaired
• Hormones affect mood, cognition, and behavior* in both sexes
- Ultimately, determined by complex interaction•, hormones, and experience
Female hormones, especially estradiol/estrogen…
May affect cognition
May cause depression or mania in females when levels change abruptly
May modulate the effects of monoamines
Reproductive hormones may affect emotions but not cognition or behaviors.
False
Electroencephalography( EEG)
Measures summed graded potentials of cortical dendrites (excitory/inhibitory changes).
- shows function, not structure
Advantages*
- Excellent temporal* resolution (msecs-secs)
- Can be performed in office or a clinic*, relatively less expensive
- Very useful for diagnosing seizures, sleep disorders, depth of anesthesia, attention deficits, brain injury, coma, brain death
Disadvantages*
- Much less* spatial resolution* (knowing source of various waves)
- Mostly assesses cortical* activity (although not all cortical activity)
Neuroimaging: Nomenclature*
o Currently, left side of image = left side of pt
Hypointensity= darker
Hyperintensity= lighter
Neuroimaging: Computed^ tomography^ (CT*)
Static/structural^ neuroimaging
– Photographs structure / not function
Denser tissues absorb more x-rays
o Bone is white, brain tissue is gray, fluid and blood (ventricles sulci - cerebral spinal fluid) are dark
o Yields 2-D images, but computational reconstruction can yield 3-D images
CT Advantages*
o Good resolution (1 mm in diameter)
o Used mainly in ER (done quickly)
o Good for imaging bone, TBI, stroke
CT Disadvantages*
o X-ray* exposure (moderate-high)
o Less contrast* between gray and white matter than MRI
MAGNETIC RESONANCE IMAGING (MRI)
Assess structure of brain:
Different tissues (CSF, myelin, neurons) have different water content (proton density) and respond differently to a magnetic field and a radiofrequency pulse
- cause different electrical signals, which are used to create images
- yields 2-D images, but computational reconstruction can yield 3-D
- Manipulates various parameters of a scanner that allows for different protocols* that can optimally address different referral questions and hypotheses
- different protocols create different images
Advantages:
- different protocols create different images
- Better contrast than CT
- Good Spatial resolution* (1mm in diameter)
- No exposure to radioisotopes or x-rays
Functional/dynamic^ neuroimaging
- Measures changes in activity^ throughout the brain
* Neuronal activity is inferred from changes in various physiologic parameters*
Positron Emission Tomography (PET)
Radioactive molecules are injected into the body
- Radioactive molecules decay, emitting positrons
- Positrons collide with electrons, thereby emitting
photons (light particles)
Create an image
• When radioactive oxygen is injected, the process is an indirect measure of increased blood flow* and, therefore, neuronal activity*
- In other words, increased blood flow goes to areas where there is an increase in neuronal activity
Advantages* of PET
o Good spatial resolution (2mm)
fMRI is better (1mm)
o Used extensively in research* to study specialization of brain areas
o Useful for diagnosing early neurodegenerative diseases, changes* after lesions or treatments
Disadvantages*
o Must be near a cyclotron* since radioactive isotope decays rapidly (2-110mins)
o Expensive (about $2 million), requires special preparation/handling of radioactive material
o Repeated imaging over short periods is not practical
fMRI
- Indirectly measures increased blood flow* and, therefore, increased neuronal activity*
- Measures changes in blood oxygen level-dependent (BOLD) signal—a differential measure of oxyhemoglobin vs. deoxyhemoglobin
o Hemoglobin is a molecule inside our red blood cells, erythrocytes, that actually carry oxygen – then called oxyhemoglobin (carry oxygen to tissues) –
When it gets to the tissues it picks up carbon
dioxide and carries it back to the lungs – then
called deoxyhemoglobin (meaning no oxygen)
Releases carbon dioxide at lungs – we exhale carbon dioxide – and then inhale more oxygen – constant
o Active neurons uses O2 which increases blood flow and an increase in oxyhemoglobin
Advantages
o No radioactive isotopes or cyclotron required
o Excellent spatial resolution* (1mm)
o Same individual can be repeatedly scanned since no radioactive isotope is injected
Disadvantages*
o Both PET and fMRI relatively simple tasks compared with complexity of everyday task
o But subjects must still be able to pay attention and
not move during procedure
o Neuropsychological* tests and knowledge* are
critical* for good experiments using these techniques
Magnetic Resonance Spectroscopy
Can image chemical composition of brain not imaged by standard MRI (about 20% of brain)
- it can image DNA, RNA, most proteins (receptors), organelles, glutamate, ACh, membranes, exc.
PET and fMRI
Both “Can assess brain function by indirectly measuring blood flow” and “Can assess many different molecules, such as beta-amyloid plaques”
A1
PRIMARY AUDITORY CORTEX
Heschl’s gyrus, tucked within Sylvian fissure
Wernicke’s area
Area in the left temporal lobe
- Specialized in words and rapid sequences (temporal order) of sounds
- Good for language comprehension
- Responsible for comprehending content of language
Prosody
Right temporal lobe is specialized for *prosody^
• Emotion, intonation, inflection* in language (pitch, timbre; relations between the pitch of sounds)
• Critical for interpreting subtle inflections and cues from others
- The area in the right hemisphere that is responsible for comprehending prosody in others’ speech
Somatosensory area* (S-1)
- Also called the “sensorimotor cortex”
- Conscious perception of touch proprioception (joint/muscle position), temperature, pain, itch
Somatosensory in the Parietal Lobe
In details vary according to experience
• Can be modified through neuroplasticity by
experience
- i.e. soccer player has more sensory neurons devoted to feet and a pianist has more neurons devoted to fingers
- More you practice the more neurons have to specialize in a specific area
Sensory Integration
• Sensory integration* of somatosensory, auditory, and visual information allows for a single, coherent percept*
o The binding mechanism*
Synchrony*
Generates knowledge* - understanding the meaning and relationships among sensory inputs; the beginning of abstraction*
• Sends* highly integrated* sensory information to frontal lobes, which are responsible for “final” integration with limbic input
• Reading and writing* are preformed here; they require orthographic and phonological processing.
parieto-temporo-occipital* cortex
(tertiary association area) is particularly important in overlap and binding of all three lobes:
o Contains polymodal* neurons
o But there are numerous anatomical* connections among areas for multimodal* processing
- helps area talk to other area, all connected
Polymodal* neurons
Neurons that can respond whether someone has heard something, seen something, or felt something.
- Respond to multi stimuli at the same time
- Integrates information/ specialist in integrating info
Which area is most responsible for sensory integration and generating knowledge?
Parieto-temporo-occipital cortex
Prefrontal Cortex
• Receive sensory information from posterior lobes
• Receives input from limbic system
• Integrates that information
• Plans, organizes most appropriate response
o Executive^ roles
Prefrontal Cortex: Executive functions
self-control* of attention, behavior, and emotion*
Prefrontal cortex: Dysfunction
o Problems with attention o Difficulty planning*, carrying out plans* o Impulsivity* o Emotional lability* o Apathy*
Neurotransmitters* (NTs) in the prefrontal cortex
o Glutamate (Glu) excitation
- Sensory data reach entire cortex via Glu - Cortical areas communicate with other cortical areas and lower CNS structures via Glu
o Gamma-aminobutyric acid
- (GABA): inhibition
o Histamine (HA): “wakes” cortex
Neurons in Prefrontal cortex are modulated by:
Dopamine (DA)
Norepinephrine* (NE)
Serotonin* (5-HT)
Acetylcholine (Ach) in Prefrontal cortex
Cell bodies located in upper brainstem, ventral (lowest portion of the forebrain/ cerebral hemispheres) portion of frontal lobes (“basal forebrain”)
Affects prefrontal function, memory in hippocampus, medial temporal lobe
o DLPFC
Dorsolateral prefrontal cortex (DLPFC)
Conceptualizing* , maintaining* goals; allocating attentional* resources accordingly
• Helps one focus* on task at hand according to an internal plan
• Not being distracted by stimuli, not* being Pulled to the stimulus
• Planning overall sequences, contingency planning
• Learning* from experience*
Adapting* to novelty and cognitive flexibility* (shifting set)
• Regulating* behavior based on current environmental stimuli
• Suppressing* routine* responses in favor of a novel* response that is required or more appropriate for a given situation
DLPFC: Problem-solving, Abstraction, Working Memory
• Developing strategies* for solving complex problems*
• Abstract thinking*
• Executive* component of working memory*
- Frees one from immediate demands of environment by holding information in memory long enough to store, manipulate, or act on it
i.e. “Digits Backwards Test”
Allows one to act based on: o Internally generated rules*, plans* o Reflection*, judgment* o Historical information* o Abstract themes* common to different situations
o Orbitofrontal Cortex (OFC)
Inhibiting^ inappropriate impulses, drives
Dysfunction* MAY CAUSE DISINHIBITON^
• Impulsivity^: failure to stop initiating*
• Inappropriate behavior
o Failure* to resist starting drugs of abuse*
o Hyperactivity/impulsivity* during ADHD, suicide* speech* during mania
o Obsessions
Compulsivity^: failure to stop ongoing actions
o Compulsions* are associated with dysfunctional circuit involving OFC, Bansal Ganglia, thalamus
o Compulsive aspect of substance use* disorders
OFC – personal reasoning, dysfunction
Personal* and social* reasoning; maintaining employment* and stable relationships*
Involved in making decisions based on evaluating degrees of uncertainty* in the world
Dysfunction* may cause:
Risk taking*
Less* responsiveness to punishment
Decreased empathy* and concern for social rules*
Difficulty* holding jobs, social relationships
Changes* in personality, social interactions
• Especially with dysfunctions of right* OFC
Ventromedial Prefrontal Cortex (VMPFC)
Regulation* of motivation, emotions including the extinction* of conditioned fear
Inefficient processing*- Hypoactivity OR hyperactivity may produce symptoms:
- Depression* - Depressed mood, excessive guilt, feelings of worthlessness, apathy, decreased social interaction, psychomotor retardation - Mania* (elevated/irritable mood)
Involved in:
Correctly recognizing emotion* from facial* expressions
Selecting behaviors based on context* and self-knowledge*
o Autobiographical* memory, in conjuction with OFC, basal forebrain, and hippocampus
Autonoetic awareness: awareness of self with a past and future
Dysfunction makes it difficult to put one’s life in context, maintain relationships, be flexible
