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Physiology exam 2

Terms in this set (194)

physically supports neurons in proper spatial relationships (glue)
astrocytes
serve as scaffold during fetal brain development
astrocytes
Induce formation of blood brain barrier by changing the capillaries
astrocytes
Help transfer nutrients to neurons
astrocytes
Form neural scar tissue ( to repair the brain)
astrocytes
Take up and degrade released neurotransmitters
astrocytes
take up excess K+ to help maintain proper brain-ECF ion concentration and normal neural excitability
astrocytes
enhance synapse formation and strengthen synaptic transmission via chemical signaling with neurons
astrocytes
communicate by chemical means with neurons and among themselves (with glutamate- can also trigger release of ATP)
astrocytes
Form myelin sheaths in the CNS
oligodendrocytes
Play a role in defense of brain as phagocytic scavengers (immune defense)
migroglia
What do microglia do during embryonic development
migrate to CNS and then remain stationary until activated by infection or injury.
Release nerve growth factor (help neurons survive and thrive)
microglia
release destructive chemicals for assault against their target

if this is excessive, what can it lead to?
active microglia

attack of neurons that need to be there- neurodegenerative diseases will occur if this continues
Line internal, fluid filled cavities of brain and spinal cord
ependymal cells
contribute to formation of cerebrospinal fluid (line the ventricles of the brain)
ependymal cells
contains cilia- the beating of the cilia contributes to the flow of cerebrospinal fluid through the ventricles
ependymal cells
Serve as neural stem cells with the potential to form new neurons and glial cells (precursors)
ependymal cells (dormant)
what makes up 99% of all neurons
interneurons
what makes up 90% of the cells in the brain
glial cells
How do neurons communicate?
-across gap junctions
-chemical signals
what does binding of glutamate or detection of extracellular ATP at astrocytes receptors lead to?
Ca2+ influx into the glial cell- then there is a release of ATP by that glial cell-which activates adjacent glial cells
Gliotransmitters
-chemicals released by glial cells and affect the receptor responses
-effect neuronal excitability and strengthen synaptic activity
Thrombospondin
trigger synapse formation
what structure contains a specific region in which new neurons are made?
hippocampus
can glial cells and neurons generate?
only glial cells can

that is why gliomas are the most common brain tumors
Besides gliomas, what are other ways brain tumors can form?
-metastasize to the brain from other parts of the body
-meningiomas (meninges is the protective membranes covering the CNS
dura mater- contains two layers- but these layers separate to form:

what is the purpose of these?
dural sinuses (blood-filled cavities
and
venous sinuses (larger cavities)

allows venous brain to drain and return to heart; cerebrospinal fluid reenters the blood here
arachnoid mater
weblike middle layer of the three meninges
subarachnoid space
a space in the meninges beneath the arachnoid membrane and above the pia mater that contains the cerebrospinal fluid
arachoid villi
penetrate through the gaps in the overlying dura and project into the dural sinuses
where does the CSF reabsorbed across into the blood
arachoid villi
pia mater
thin, delicate inner membrane of the meninges

highly vascular and closely adheres to the brain and spinal cord
major function of CSF
ask as a shock absorber, exchange of materials between the neural cells and the interstitial fluid (not the blood or CSF)
How is CSF formed?
choroid plexus (cauliflower like masses)
composition of CSF
highly regulated

lower in K+ and higher in Na+ compared to the blood. There are no proteins

it influences the interestial fluid of the brain (an ideal environment for ions to move down their concentration gradient)
what is the flow of CSF?
- Produced by the choroid plexus lining the ventricles
- Flows from the lateral ventricles into the 3rd ventricle via the inter ventricular
- Flows from the 3rd ventricle to the 4th ventricle via the cerebral aqueduct
- Flows from the 4th ventricle into the subarachnoid space
-then reabsorbed from the subarachnoid space into the venous blood across the arachnoid villi
reduction of pressure of the CSF can result in
headaches (but the volume is replaced about 3 times a day)
hydrocephalus
abnormal accumulation of fluid (CSF) in the brain (increase in pressure)
what can pass through the capillaries within the brain
the capillaries within the brain are less permeable than capillaries in other parts of the body

O2, CO2, alcohol, and steroid hormones
(all other molecules are passed into the brain through membrane-bound carriers)
benefits and detriments of BBB
- it keeps harmful changes of the blood (concentration of ions, diseases, etc)
-but this makes it harder to use drugs to treat brain and spinal cord damage and illnesses
what are the three roles that astrocytes have on the BBB
1) they signal cells forming the brain capillaries to "get tight" (capillary cells do not form tight junctions on their own)
2) promote the production of specific carrier proteins and ion channels that regulate the transport of selected substances through these capillary cells
3)participate in the cross-cellular transport of some substances (K+)
what does the brain depend on
constant O2 and glucose (does not store any glucose)

unlike other parts of the body the brain cannot make ATP without O2
neuroglobin
O2 carrying molecule in the brain
during starvation what does the brain use instead of glucose?
ketone bodies made from the liver
do any parts of the brain act in isolation
no, all regions of the brain are part of a neural network- but different regions accomplish different things
what are the three parts of the brain stem
midbrain, pons, medulla
functions of the brain stem
1) cardiovascular, respiratory, digestive control centers
2) regulation of muscle reflexes for balance and posture
3) reception and integration of all synaptic input from the spinal cord; arousal and activation of cerebral cortex
4) role in sleep-wake cycle
where is the origin of peripheral cranial nerves
brainstem
functions of the cerebellum
- Maintenance of balance and posture
- Coordination of voluntary movements
- Motor learning- like dance routine
- Cognitive functions
-enhancement of muscle tone
what are the two components of diencephalon
thalamus and hypothalamus
functions of hypothalamus
-Master control of autonomic nervous system (influences heart rate, blood pressure, digestive activities, and respiration)
-Master control of the endocrine system (secretes hormones that control secretory activities in the anterior pituitary gland)
-Regulation of body temperature (shivering and sweating)
-Control of emotional behavior (Pleasure, aggression, fear, rage, contentment, and the sex drive)
involvement with emotion
-Control of food intake (Monitors nutrients and produces sensations of hunger)
-Control of water intake (Monitor blood solute concentrations)
-Regulation of sleep-wake (circadian) rhythms
- link between nervous and endocrine systems
functions of the thalamus
Relay station ("triage center") for sensory impulses; crude awareness and some degree of consciousness (primitive sensory processing)
and a role in motor control
what are the two components of the cerebrum?
basal nuclei and cerebral cortex
functions of basal nuclei
inhibition of muscle tone, coordination of slow, sustained movements
suppression of useless patterns of movement
functions of cerebral cortex
sensory perception, voluntary control of movement, language, personality traits,
sophisticated mental events (thinking, memory, decision making, creativity, and self consciousness
what are the two cerebral hemispheres connected by?
corpus callosum (contains 300 million neural axons)
corpus callosum
information highway- there information exchange is constant
What kind of matter is the cerebral cortex?
gray matter (surrounds the white matter of the core)
gray matter
a portion of the CNS consisting of cytons (cell bodies), their dendrites and synaptic connections. Most glial cells

integration and initiation
white matter
bundles or tracts of myelinated nerve fibers (axons)

transmit signals among the different regions of the brain
Positron Emission Tomography (PET)
a method of brain imaging that assesses metabolic activity by using a radioactive substance injected into the bloodstream- release in tiny burst of gamma-ray energy (increased gamma activity is increased neural activity)
functional magnetic resonance imaging (fMRI)
A noninvasive imaging technique that uses magnetic fields to map brain activity by measuring changes in the brain's blood flow and oxygen levels
Optogenetics
Transgenic technique that combines genetics and light to control targeted cells in living tissue

hypopolarizing and hyperpolarizing these cells via light-induced changes in ion channels
stellate cells
neurons responsible for initial processing of sensory input to the cortex
pyrimidial cells
nerve cells send fibers down the spinal cord from the cortex to terminate on motor neurons
What are the four lobes of the brain?
frontal, parietal, occipital, temporal
occipital lobe
visual processing
temporal lobe
A region of the cerebral cortex responsible for hearing and language.
central sulcus
separates frontal and parietal lobes
parietal lobe
responsible for receiving and processing sensory input (somatosensory processing)
frontal lobe
1) voluntary motor activity
2) speaking ability
3) elaboration of thought
somatosensory cortex
A brain area at the front of the parietal lobes that processing and perception of both somesthetic and proprioceptive input (from opposite side of the body)
Proprioception
our sense of body position
primary motor cortex
the section of the frontal lobe responsible for voluntary movement- skeletal muscles on the opposite side of the body
where is readiness potential detected
motor cortex
what higher areas command the primary motor cortex
supplementary motor area, premotor cortex, and posterior parietal cortex (cerebellum sends motor input to these
supplementary motor area
preparatory role in programming of complex movements
what happens when there is a lesion in the supplementary motor area
there is not paralysis- but it does interfere with performance of complex movements
premotor cortex
important in orienting the body and arms toward a specific target (must be informed about the momentary position)
posterior parietal cortex
integration of somatosensory and visual input; important for complex movements
what happens when one area of the brain is destroyed?
other areas nat gradually assume some or all of the functions of the damaged region
which hemisphere is responsible for language ability
left in most people

if this damaged early in life- the ability can be reassigned to the right hemisphere (after adolescence- damage to the ability is permanent)
Broca's area
Controls language expression - an area of the frontal lobe, usually in the left hemisphere, that directs the muscle movements involved in speech.
Wernicke's area
controls language reception - a brain area involved in language comprehension and plans the content of spoken or written words; usually in the left temporal lobe
angular gyrus
receive sensory inputs and integrates the; then the information is transferred to Wernicke's area
aphasias
Language disorders, which are associated with Broca's and Wernicke's areas in the brain.
speech impediment
a physical defect in the mechanical aspect of speech that prevents a person from speaking normally
dyslexia
language disorder that makes it difficult to decode and read- deficit in phonological processing
prefrontal association cortex
brainstorms or thinks

1)planning voluntary movement
2) decision making
2)creativity
4) personality traits
where is the site of working memory
prefrontal association cortex
parietal-temporal-occipital association cortex
- Integrates somatic, auditory and visual sensations
- Picture relationship of body to external environment
- involved in the language pathway connecting Wernicke's area to the visual and auditory cortices
limbic association cortex
mostly on inner and bottom surface of temporal lobe; motivation and emotion; memory
left cerebral hemisphere
Dominates in speech sounds & in understanding sequential, rational & analytical concepts

fine-detail
right cerebral hemisphere
Controls left body,

Creative, Visual, facial recognition, visual, and musical traits

big picture
Electrocephalogram (EEG)
An amplified recording of the waves of electrical activity (collective postsynaptic potential activity- EPSP's and IPSP's) that sweep across the brain's surface. These waves are measured by electrodes placed on the scalp.
what are the three major uses of EEG
1) clinical tool in the diagnosis of cerebral dysfunction (damage gives rise to EEG)
2) used in the legal determination of brain death
3) distinguish various stages of sleep
Default Mode Network (DMN)
Structures active during unconscious, background activity or "mind wandering"

- prepare brain for conscious activity, creativity, thoughts, and retrieving or manipulating memories
subcortical regions include
basal nuclei in the cerebrum- and the thalamus and hypothalamus
basal nuclei function in fine more control
1) play an important inhibitory muscle tone
2) role in selecting and maintaining purposeful motor activity while suppressing useless or wanted patterns of movement
3)helping monitor and coordinate contractions (they do not directly influence the motor neurons)
Parkinson's disease
gradual destruction of neurons that release dopamine in the basal nuclei

1)increased muscle tone
2)resting tremors (unwanted actions)
3) slowness in initiating and carrying out certain motor activity
Diencephalon
"Middle of brain"- in between Cerebrum & Brain Stem

Consists of:
1. Hypothalamus
2. Thalamus
thalamus sensory relay station
screens out significant information and forms pathways for important information

- reinforces voluntary motor behavior
-there is some consciousness in this area.
Hypothalamus
a neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion and behaviors

also participate sin the sleep-wake cycle
limbic system includes
cerebral cortex, basal nuclei, thalamus, hypothalamus
limbic system key roles
emotions, basic survival, sociosexual behavioral patterns, motivation, and learning
Amygdala
processing inputs that give rise to the sensation of fear
memory trace
physical neural change in the brain that occurs when a memory is formed
consolidation
changing short-term memories into long-term memories
working memory
a newer understanding of short-term memory that focuses on conscious, active processing of incoming auditory and visual-spatial information, and of information retrieved from long-term memory
habituation
decreasing responsiveness with repeated stimulation of an indifferent stimulus. As infants gain familiarity with repeated exposure to a visual stimulus, their interest wanes and they look away sooner.

depresses synaptic activity
Sensitization
an increase in behavioral response after exposure to a strong or threatening stimulus

enhances synaptic activity
long-term potentiation
gradual strengthening of the connections among neurons from repetitive stimulation
AMPA receptor
chemically mediated receptor-channel that opens on binding of glutamate and permits net entry of Na+ ions- leading to formation of EPSP because it is hypopolarized to threshold
NMDA receptor
a specialized ionotropic glutamate receptor that controls a calcium channel that is normally blocked by Mg2+ ions; involved in long-term potentiation

both chemically gated and voltage dependent
what is needed in order for an NMDA receptor to open?
presynaptic release of glutamate and postsynaptic hypopolarization occurring simultaneously.
what is the retrograde messenger for long-term potentiation
nitric oxide
short term memory involves what
transcient changes in synaptic activity
long term memory involves what
formation of new permanent synaptic connections in the gray matter and white matter
cAMP responsive element-binding protein
acts on DNA to ultimately influence synthesis of new proteins important for maintaining long-term memory
immediate early genes (IEGs)
govern synthesis of the proteins that encode long-term memory
Neuregulin
regulate the extent to which myelin forming cells wrap themselves around the axon (the more action potentials, the more of this is released)
Where are memory traces stored?
well there are multiple regions in the brain
what kind of memories are stored in the hippocampus
declarative memories
Hippocampus in regards of declarative memories
crucial for consolidation; stores long-term memories for a short time and to other cortical sites
semantic memories
memories of facts
episodic memory
memory for one's personal past experiences
which memories are first to go
declaritive
alzheimer's disease results from damage in what region of the brain
damage in the hippocampus
what memories are stored in the cerebellum
procedural memories
What memories are stored in the prefrontal cortex?
working memory
characteristic of brain lesions in Alzheimers
neuritic plaque, beta amyloid, neurofibrillary tangles (some areas are deficit in acetylcholine)
Amyloid Precursor Protein (APP)
a membrane protein found mainly in neurons that gives rise to the material in amyloid plaques
tau
a protein associated with neurofibrillary tangles in Alzheimer's disease
What is the cerebellum responsible for?
balance and planning and executing voluntary movement
vestibulocerebellum
maintenance of balance, control of eye movements
spinocerrebellum
enhances muscle tone and coordinates skilled voluntary movement.

corrects any orders from higher up about these movements and will predict the position of a body part and will makes adjustments
cerebrocerebellum
role i planning and initiating voluntary activity by providing input to the cortical motor areas

stores procedural memories
cerebellar disease
drunken state; reduced muscle tone but not paralysis difficulty in complex motor activity

intention tremor and does not directly influence motor neurons
brain stem is a vital link for?
the spinal cord and the higher brain regions
vagus nerve (X)
This nerve innervates most of the viscera in the thoracic and abdominopelvic cavities.
reticular formation
a nerve network that travels through the brainstem and thalamus and receives and integrates all incoming sensory synaptic input. Important for arousal and activation of the cerebral cortex
Reticular Activating System (RAS)
a dense network of neurons found in the core of the brain stem; it arouses the cortex and screens incoming information
what kind of process is sleep
it is an active process consisting of alternating periods of slow-wave and paradoxical sleep
Global Workspace Theory
conscious experience arises from coordinating the activity of functionally specialized brain areas

information that is being processed locally are broadcasted throughout the brain
when do nightmares occur
stage 3 and 4 of slow-wave sleep
arousal system
Neurons in hypothalamus; stimulate RAS
slow-wave sleep center
hypothalamus containing sleep ON neurons
paradoxical sleep center
brainstem containing REM sleep ON neurons
hypocretin/orexin
Chemical in your brain that causes you to feel awake
what neurotransmitter inhibits arousal
GABA
adenosine
the longer we are awake the more buildup we have of this

it inhibits the arousal center
caffeine
blocks adenosine receptors
synaptic homeostasis hypothesis
downscaling off the active synapses, only the strongest ones are kept in memory
Narcolepsy
A sleep disorder characterized by uncontrollable sleep attacks. The sufferer may lapse directly into REM sleep, often at inopportune times.

hypocretin deficit
spinal taps
obtain CSF are performed by inserting a needle into the vertebral canal below the second lumbar
How is white matter organized?
By ascending and descending tracts

each tract begins or ends in a specific region of the brain and transmits a specific type of info
Ascending tracts of the spinal cord
carry sensory information to the brain
Descending tracts of the spinal cord
carry impulses for transmission to muscles and glands
dorsal horn of spinal cord
cell bodies synapsed by afferent neurons (sensory)
ventral horn of spinal cord
contains cell bodies of MOTOR neurons
lateral horn of spinal cord
Contains the cell bodies of the preganglionic ANS neurons
dorsal root of spinal nerve
carries afferent (sensory) information
dorsal root ganglion
contains cell bodies of sensory neurons
ventral root of spinal nerve
This structure contains the cell bodies of the somatic motor neurons that innervate the skeletal muscles.
nerve
bundle of axons in PNS, does not contain a complete nerve cell

there are no nerves in CNS- those are called tracts
do individual nerve fibers interact with each other?
no they do not have a direct influence on each other
dermatome
surface region of a nerve
referred pain
pain that is felt in a location other than where the pain originates
dorsal columns of spinal cord
ascending

conscious muscle sense concerned with awareness of body position; crossed touch, pressure, vibration
dorsal spinocerebellar tract
ascending

unconscious muscle sense- important in muscle tone and posture
ventral spinocerebellar tract
ascending

unconscious muscle sense
lateral spinothalamic tract
ascending

pain and temperature
ventral spinothalamic tract
ascending

touch
lateral corticospinal tract
descending

voluntary control of skeletal muscles
rubrospinal tract
descending

involuntary control of skeletal muscle concerned with muscle tone and posture
ventral corticospinal tract
descending

voluntary control of skeletal muscles
vestibulospinal tract
descending

involuntary control of muscle tone to maintain balance and equilibrium
stretch reflex
involuntary contraction of a muscle due to rapid stretching of that muscle
spinal reflex arc
simplest motor function, provides an efferent response to basic changes in the length of muscles
reciprocal innervation
when a reflex stimulates one muscle to contract and inhibits the antagonistic muscle
crossed extensor reflex
when a withdrawal reflex is initiated in one lower limb, the crossed extensor reflex causes extension of opposite lower limb
modalities
various forms of energy (have to be transformed into electrical for CNS to understand)
tonic receptors
adapt slowly or not at all
phasic receptors
display adaptation and decrease frequency of action potentials
Pacinian corpuscles
respond to deep pressure and vibration- respond with a slight hypo-polarization called the off-response when the stimulus is removed
Merkel's disks
respond to light pressure
Ruffini endings
respond to stretch (fire to constant pressure)
Meissner's corpuscles
sensitive to light touch
somatosensory pathways
convey conscious somatic sensations
labeled lines
consist of discrete chains of neurons

synaptically interconnected in a particular sequence to accomplish progressively more sophisticated processing of the sensory information
Second-order sensory neurons
synapse (on the medulla or spinal cord) then it synapsed on the third-order sensory neuron in the thalamus
type of fibers and receptors for fast pain
A-delta fibers and mechanical and thermal receptors
slow pain fibers and receptors
polymodal and C-fibers (unmyelinated
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