Neurophysiology Flashcards
what is anatomy
nervous system structure
what is physiology
nervous system function
brain and spinal cords are apart of:
the CNS
peripheral nerves and ganglia are apart of:
PNS
what is the minimal functional “unit” of the nervous system
neuron
neurons do 2 things:
- conduct “electrical” signals - action potentials
- release “chemical” signals - neurotransmitters
what nerves are responsible for the control on movement and some functions?
motor nerves
what nerves are responsible for the detection of external stimuli
sensory nerves
what are responsible for the neuronal activity and connections (circuitry)
association neurons
what are association neurons important for and where are they located?
- within the CNS
- responsible for behavior, thought and emotions
neuron
basic functional unit of the nervous system
dendrites
receive information from sensory receptors and send it to the cell body
axons
deliver electric signals from the cell body to another neuron or an effector organ (muscle)
how do neurons transmit information
- through electrical impulses called “action potentials”
what do neurons do with action potentials
they convert the electrical impulse to a chemical signal called a synapse
what do sensory or afferent neurons do?
they conduct impulses from sensory receptors INTO the CNS
what do association or interneurons do?
they are located entirely within the CNS and help integrate CNS functions
what do motor or efferent neurons do?
they conduct impulses from sensory receptors OUT OF the CNS - to effector organs like muscles or glands
somatic muscle neurons
reflex and voluntary control of skeletal muscles
autonomic motor neurons
Involuntary control of smooth muscle, cardiac muscle and glands
what are the subclasses of autonomic neurons
- sympathetic
- parasympathetic
what is the simple neural circuit
- the neuron receives a stimulus and the sensory/afferent neurons send the information to the CNS
- interneurons send signals from one neuron to another
- the motor/efferent neurons send commands from the CNS to the muscles or glands to produce a response
what are the 4 types of neurons
- Pseudopolar (unipolar) - sensory, 1 process that splits
- bipolar - retinal and cochlear, 2 processes
- multipolar - most common, motor & association, many dendrites but one axon
- anaxonic, some CNS neurons, no obvious axon
what are the supporting cells in the PNS
- schwann cells - form myelin sheaths around PNS neuron axons
- satellite cells - support neuron cell bodies within ganglia of the PNS
supporting cells on the CNS
- oligodendrocytes- form myelin sheaths around CNS neuron axons
- microglia - migrate through CNS & phagocytose debris
- astrocytes - help regulate external environment of the neurons in CNS
- ependymal cells - line the ventricles (cavities) of the brain and spinal cord
schwann cells look like:
successive wrapping of schwann cell membrane around one axon, cytoplasm on outside
astrocytes
- most abundant cell in the CNS
- contains up to 90% of the nervous tissue in some areas of the brain
- star-like shapes with many branching processes that reach out to capillaries and neurons
- play an important role in blood-brain barrier function
step 1 of the CNS supporting cells
- Take up K+ from ECF (diffuses from neurons during
nerve impulses), may help maintain proper ionic
environment for neurons
step 2 of the CNS supporting cells
- Can take up neurotransmitter glutamate and
transform it to glutamine, which can be released back
into neurons, which can use it to reform the
neurotransmitter glutamate.
step 3 of the CNS supporting cells
- The “end-feet” surrounding blood capillaries take up
glucose from blood, metabolize it to lactate, then
release it for use as an energy source by neurons, which metabolize it aerobically into CO2 & H2O for production of ATP
step 4 of the CNS supporting cells
Astrocytes are needed for the formation of synapses
in the CNS
step 5 of the CNS supporting cells
Astrocytes regulate neurogenesis in the adult brain
(needed for stem cells to differentiate into both glial
cells and neurons)
step 6 of the CNS supporting cells
Help with the formation of the blood-brain barrier
step 7 of the CNS supporting cells
Release neurotransmitters (glutamate, ATP,
adenosine, D-serine, others) that can stimulate or
inhibit activity of neurons.
Capillaries in the Brain vs. Other Organs
-capillaries in the brain don’t have pores between adjacent endothelial cells and are instead joined by tight junctions
- these tight junctions prevent large molecules and pathogens from easily crossing into the brain
Nicotine and Acetylcholine Receptors
- nicotine is a major component in tobacco smoke and it can cross the blood brain barrier
- once in the brain nicotine binds to acetylcholine receptors
- acetylcholine is a neurotransmitter that plays a key role in processes like muscle movement and cognitive function
- when nicotine binds, it mimics acetylcholine effects and stimulates the release of several neurotransmitters, including dopamine (why its addicting)
what are the effects of CNS depressant
- directly affects brain cells
- affects areas involved in inhibiting behaviours (more animated, talkative and social)
- alters speech, slowed reaction time, foggy memory
- reactions depend on dose, weight, gender, genetics, etc
rabies and the BBB
- virus infects the brain
- immune cells and antibodies can’t enter the brain
- no treatment after symptoms, but before, rapid treatment with anti-rabies antibodies can help
BBB and drug treatments
- the BBB is a protective layer around the brain that limits what substances can pass from the blood to the brain
- this makes treating neurological disorders tricky because many drugs can’t easily cross the BBB to reach the brain
somatic nervous system
have cell bodies in the CNS and send axons to skeletal muscles - usually those under voluntary control
autonomic nervous system
involves 2 neurons in the efferent pathway
1. The first neuron (preganglionic) comes from the CNS and connects to the second neuron in the autonomic ganglion through a synapse.
2. The second neuron (postganglionic) extends from the ganglion to the effector organ (like your heart or intestines), where it releases neurotransmitters to regulate the organ’s activity.
parasympathetic nervous system saying
rest and digest
sympathetic nervous system saying
fight or flight
do PSNS and SNS oppose or agree with each other
oppose
Organs without dual innervation
- adrenal medulla
- arrector pili muscles in the skin
- sweat glands in the skin
- most blood vessels
cholinergic neurons
release ACh (acetylcholine)
adrenergic neurons
release NE (or E) - norepinephrine
cholinergic
refers to neurotransmission involving acetylcholine (ACh)
adrenergic
refers to neurotransmission involving norepinephrine (NE)
neurotransmitter for all preganglionic fibers
- ACh
- since they use ACh, transmission is said to be cholinergic
transmitter released by most parasympthetic postganglionic fibers at their synapses with effector cells
- ACh
- transmission is cholinergic
neurotransmitter released by most sympathetic nerve fibers is
- NE
- transmission is said to be adrenergic
simple diffusion (passive)
- small uncharged molecules can diffuse through the lipid bilayer
- small charges molecules (ions) can diffuse through water-filled pores
simple diffusion (passive) - ion channels
- some are “leaky” and ions flow in or out as needed
- others are voltage gated and can only be opened or closed by gates
active transport
requires metabolic energy (ATP)
- moves Na out of the cell
- moves K into the cell
endocytosis
the process where the cell engulfs substances from the outside by folding its membrane around them to form a vesicle
phagocytosis
a type of endocytosis where the cell engulfs large particles like debris, pathogens or dead cells
exocytosis
is the process by which a cell expels substances to the outside by merging a vesicle with the cell membrane
why is the active transport of Na/K important
for establishing the electrochemical gradient
why are ion channels important in the nervous system
they help produce electrical impulses that transmit information rapidly
what is the resting membrane potential
all cells in the body have a potential difference - or voltage - across the membrane
is the inside or outside of the cell more negatively charged
the inside of the cell is more negatively charged compared to the outside
what is the charge of neurons
-70mV
why are voltage gated ion channels important
- for electrical activity in axons because when the channels open they can change the membrane potential of the cell
- we need this to happen to conduct an electrical signal in neurons
ion channels: intial state
- ion channels are intially closed
- they prevent the movement of ions across the membrane
ion channels: opening and ion movement
- when ion channels open, they allow specific ions (Na, K, Ca) to move across the membrane
- this movement of ions is crucial for processes like action potentials and signal transmission in neurons
primary function of nerve cells is
to receive, conduct, and transmit signals
how do neurons propagate signals
they do this in the form of action potentials
what are action potentials
they are momentary discharges of the resting membrane potential caused by a rapid influx of Na causes by the opening of sodium ion channels
what do action potentials do once intiated
they move along the axon membrane toward the synapse
why do signals need to use voltage-gated ion channels
- signals have to go a long way without weakening, so the signals have to be continuously reamplified using these channels along the way
ion gating in axons
- channel closed at resting membrane potential
- gated channel opens in response to depolarization (action potential)
- gated channel closes (ball & chain) to block channel while it takes time to close
depolarization or (hypopolarization)
when stimulation causes positive charges to flow into the cell, so the cell becomes more positive than the resting potential
What happens when Na+ permeability increases during an action potential?
The explosive increase in Na+ permeability causes a rapid reversal of membrane potential, from -70 mV to +30 mV. This is the depolarization phase. At this point, the Na+ channels close, and Na+ permeability decreases rapidly.
How does the cell repolarize after depolarization during an action potential?
To repolarize, K+ (which is positively charged) diffuses out of the cell. This loss of positive charge makes the inside of the cell less positive (or more negative), restoring the original resting membrane potential.
What role do the Na+/K+ pumps play in maintaining the resting membrane potential?
The Na+/K+ pumps are constantly working in the plasma membrane to restore balance. They pump out the Na+ that entered the axon during the action potential and pump in the K+ that left the cell during repolarization. This helps maintain the resting membrane potential.
action potential steps
- Na+ is pumped into the cell, causing a positive charge (depolarization)
- K+ is then pumped out of the cell, to gain back negative charge (repolarization)
What are voltage-gated channels, and how are they involved in the action potential?
Voltage-gated channels are ion channels that open in response to changes in membrane potential (depolarization). In the axon, the Na+ and K+ channels are voltage-gated, meaning they open when the membrane potential reaches a certain threshold, allowing Na+ to enter and K+ to exit during the action potential.
Why doesn’t the membrane potential normally become more positive than +30 mV during an action potential?
The membrane potential doesn’t become more positive than +30 mV because the Na+ channels close quickly after depolarization, and the K+ channels open to restore the balance.
What is the “all-or-none” principle in action potentials?
The “all-or-none” principle means that once depolarization reaches the threshold, the action potential is fully triggered, and the maximum change in membrane potential is reached. If the threshold isn’t met, no action potential occurs.
How does the action potential travel in non-myelinated axons?
In non-myelinated axons, the action potential passes smoothly along the axon, and all parts of the membrane are depolarized as the wave of depolarization moves along the axon.
How does the action potential travel in myelinated axons?
In myelinated axons, the action potential jumps between the non-insulated nodes of Ranvier through a process called saltatory conduction.
What are the benefits of saltatory conduction in myelinated axons?
Saltatory conduction allows for more rapid movement of action potentials and requires less energy to restore the membrane after the action potential has been transmitted.
what happens when action potentials reach the end of the axon
they stimulate the next cell, transmitting the signal to it
what happens at then presynaptic nerve ending during neurotransmission
neurotransmitters are released that stimulate action potentials in the postsynaptic cell
what separates the presynaptic neuron from the postsynaptic cell
the presynaptic neuron ends in a terminal button, and it is separated from the postsynaptic cell by a tiny gap called the synaptic cleft, which is about 10nm in size
steps of the synapse
- action potentials reach axon terminals
- voltage gated Ca2+ channels open
- Ca2+ binds to sensor protein in cytoplasm
- Ca2+-protein complex stimulated fusion and exocytosis of neurotransmitter
what happens in the presynaptic neuron
in the axon terminals
1. action potentials conducted by axon
2. opens voltage gated Ca2+ channels.
3. release of excitatory neurotransmitter
what happens in the postsynaptic neuron
in the dendrites and cell bodies
1. opens chemically (ligand) gated channels
2. inward diffusion of Na+ causes depolarization (EPSP)
3. Localized, decremental conduction of EPSP
in the axon hillock
4. opens voltage gated Na+ and then K+ channels
in the axon
5. conduction of action potential
EPSP
excitatory postsynaptic potential (depolarization in the post-synaptic neuron)
myotonia
is a neuromuscular disorder characterized by delayed relaxation of skeletal muscle after voluntary contraction of electrical stimulation
what can cause myotonia
- mutations in muscle Cl- channel
- channel gates do not open properly
- repolarization delayed, several APs fire instead of just one
dendrites - cell body - axon
dendrites: collect electrical signals
cell body: integrates incoming signals and generates outgoing signal to axon
axon: passes electrical signals to dendrites of another cell or to an effector cell
grey matter
- contains neuron cell bodies and dendrites
- found in the cortex (surface layer) of the brain and deeper within the brain in aggregations known as nuclei
white matter
- consists of axon tracts (myelin sheaths) that underlie the cortex, and that surround the nuclei
layers of the head
scalp
skull
dura mater
arachnoid mater
pia mater
think PADS
then the brain
what is the brain encased in and protected by
the brain is encased in the skull
it is protected by several tough layers of connective tissue (the meninges - PADS)
what meningeal layers protect the spinal cord
- the same layers as the brain
- PADS!!!
what additional protections does the brain have against head trauma
in addition to the skull and the meninges, the brain is protected by 2 fluid cushions that help protect it from head trauma
- inner and outer fluid cushions
SSS and where is it located
the outer cavity is the superior sagittal sinus
- sits under the dura mater
SAS and where it is located
the inner cavity is the subarachnoid space
- space between arachnoid and pia mater
the composition of the cerebrospinal fluid is similar to…
blood plasma
how many pairs of spinal nerves
31
spinal nerves are composed of?
- sensory and motor fibers packed together
- separate near the attachment of the nerve to the spinal cord
where does the spinal cord extend to and from
from the brain stem to the pelvic region, ending just before the end of the vertebral column
where do nerves enter or leave the spinal cord
nerves enter of leave the spinal cord between the vertebrae
How do interneurons communicate within the spinal cord?
Interneurons communicate with one another along the length of the spinal cord.
How is an afferent sensory stimulus processed in the spinal cord?
can be translated up or down the spinal cord by the interneurons.
upwards to the brain - pain
downwards to muscle - reflex
What happens during the withdrawal reflex in response to a painful stimulus?
The withdrawal reflex involves the contraction of several muscles, the relaxation of other muscles, and may also trigger responses initiated in the brain.
lover motor neuron damage reflex will be
diminshed
upper motor neuron damage reflex will be
exaggerated and sometimes slightly normal
When do distinct swellings appear in the neural tube during brain development?
By the middle of the 4th week after conception, 3 distinct swellings appear at the anterior end of the neural tube, which will eventually form the brain.
What does the neural tube form during development?
The neural tube forms the brain at its anterior end, with 3 distinct swellings evident by the middle of the 4th week after conception.
What roles do the midbrain and hindbrain play in the brain?
The midbrain and hindbrain contain many relay centers for sensory and motor pathways and are particularly important in the brain’s control of skeletal movements.
What is the cerebrum, and how is it structured?
The cerebrum consists of left and right hemispheres, connected internally by the corpus callosum. It performs most of the brain’s higher functions and is divided into five regions.
frontal lobe
motor control
occipital lobe
vision and coordination of eye movements
parietal lobe
perception of somesthetic sensation
- sensation arising from cutaneous, muscle, tendon, and joint receptors
temporal lobe
interpretation and association of auditory and visual information
the insula
a region buried deep within the lateral sulcus - the division between the frontal and temporal lobes
the insula function
- Encoding memory: It helps you store and recall memories.
- Sensory and body responses: It connects what you feel (like taste, smell, sound, touch) with how your body reacts (like feeling hungry or getting chills).
- It processes information related to smell, taste, sound, and touch.
cerebral lateralization
each cerebral hemisphere receives different input. but the two hemispheres communicate with each other via the corpus callosum
damage to the right brain
difficulty with spacial concepts, maps
damage to the left brain
severe speech problems, though interestingly may leave the ability to sing unaffected
thalmaus
relay center through which all sensory information (except smell) passes on the way to the cerebrum
promotes alertness
causes arousal from sleep in response to any sufficiently strong sensory stimulus
epithalamus
- dorsal segment
- contains the pineal gland which secretes melatonin
hypothalamus location
sits above the optic chiasm
most inferior portion of the diencephalon
functions of the hypothalamus
Regulates “DAILY” body
processes
- hunger, thirst, regulation of body
temperature
- hormone secretion from the pituitary gland
- contributes to the regulation of sleep and
wake
2 systems of dopaminergic neurons of the midbrain
1- nigrostriatal dopamine system, involved in motor control
2- mesolimbic dopamine system, involved in emotional reward
what is Parkinson’s diseases caused by
the degeneration of the dopaminergic neurons in the substantia nigra
what promotes the activity of these dopaminergic neurons?
alcohol, amphetamines, cocaine, marijuana and morphine
overactivity in what region may contribute to schizophrenia
overactivity in the mesolimbic dopamine system
the cerebellum _______ and ______ motor activity initiated elsewhere
monitors and refines
what is the role of the medulla in the brain
the medulla is required for regulating breathing and cardiovascular responses. it serves as the passage for all ascending and descending fiber tracts that provide communication between the spinal cord and the brain
what vital center are located in the medulla
The medulla contains respiratory centers, which are important for regulating breathing and other cardiovascular responses. These centers are part of the brain stem and play a critical role in vital functions.
what is synesthesia
Stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway
- letters or numbers are perceived as colours
hemorrhagic stroke
blood leaks into the brain tissue
ischemic stroke
clot stops blood supply to an area of the brain
