Neurophysiology Flashcards
(68 cards)
1
Q
Peripheral nervous system
A
- somatic (SNS) sensory neurons (from skin, muscles, and joint receptors) innervate skeletal muscles that are under voluntary control and regulate special senses (taste, smell, vision)
- autonomic (ANS)-control of internal organs (blood pressure, heart rate, hormone secretion, etc), influence over digestion
- enteric digestive functions
2
Q
Neuroglial Cells
A
supportive fuctions, found in CNS and PNS because neurons cannot reproduce
- astrocytes, microglia, ependymal cells, and oligodendrocytes in CNS
- schwann cells and satellite cells in PNS
3
Q
Central Nervous system
A
brain and spinal chord
4
Q
types of neurons
A
- multipolar (most common)-cell body @ one end, dendrites @ other
- bipolar-mediates special senses (found in inner ear and retina) cell body in middle, trigger zone below. dendrites and axon terminal at ends
- unipolar=mediate touch, pain, cell body off to the side, trigger zone below dendrites
5
Q
Nerve
A
group of axons+connective tissue wrapping and blood vessels
- epineurium (cell)
- perineurium (fasicle)
- endoneurium (individual axons)
6
Q
astrocytes
A
- found in CNS, star-shaped
- structural support and part of blood-brain barrier
- during development, important in guiding axonal growth
7
Q
microglia
A
- found in CNS
- immune system, ingest cells/particles after injury or disease and remove cellular debris/dying cells
8
Q
ependymal cells
A
found in CNS
produce and circulate CSF throughout ventricles
9
Q
oligodendrocytes
A
- forms myelin around CNS axons
- makes sheaths of myelin that spiral around axons
- neurolemma not present because they do not wrap around axon
10
Q
Schwann cells
A
FOR A AND B FIBERS
-found in PNS
-form 1 big sheath by wrapping around axon many times (this becomes myelin)
-outer part of Schwann cell=neurolemma
-nodes of Ranvier=gaps in myelin
FOR C FIBERS
-unmyelinated axons lie within Schwann cells but Schwann cells don’t wrap membrane continuously around, instead holds axons in place and prevents them from touching eachother (cross-firing)
11
Q
Grey matter vs. white matter
A
grey=cell bodies and dendrites
white=myelinated portions
12
Q
Satellite cells
A
flat cells that provide structural support and regulate the exchange of materials in PNS
13
Q
Multiple Sclerosis
A
autoimmune disease that attacks myelin–>demyelination–>firing is not effective–>weakness, loss of vision
14
Q
Na-K pump
A
- pumps Na OUT of and K INTO the cell (3 for 2) and establishes an electrochemical gradient
1. Na binds to protein/ATPase is split into ADP, phosphate, and energy. phosphate binds to pump and triggers change in shape
2. change shape pump releases 3 Na ions
3. K binds to pump and triggers detachment of phosphate –>pump returns to original shape and K is released
15
Q
Leak channels
A
- passive transport, move small charged particles selectively
- more K than Na leak channels and K channels are leakier–>contributes to resting membrane potential
16
Q
resting membrane potential
A
separation of electrical charges-excitable tissues (nerves and mm) can change their membrane potential
maintained by
1. Na/K pump
2. Na/K leak channels
3. large, charged molecules in the cell bind to ATP/cannot leave
changed by
-concentration and electrical gradients
-relative permeability of Na vs. K can change
17
Q
graded potentials
A
- initial increase in potential (below -55mV) in dendrites of interneurons and motor neurons and on motor end plates
- caused by small, local influxes of Na–>charge diminishes before cell reaches -55 mV because current leaks (no myelin on dendrites)
- mediated by ligand-gate ion channels
1. glutamate mediates Ca channels (excitatory)
2. GABA mediates Cl channels (inhibitory)
18
Q
Action Potentials: rising phase
A
- critical threshold for opening of Na channels (open rapidly)=-55mV
- permiability of Na becomes much higher than that of K and Na floods the cell +30mV (channels open for half a ms-inactivation gate begins to close slowly when activation gate opens quickly)
19
Q
Action Potentials: falling phase
A
- at -55 mV, K channels are triggered to open, but they open slowly
- K flows out of cell aiming to reach it’s equilibrium (when the cell is at -90mV)
20
Q
Action Potentials: After-hyperpolarization
A
- K channels close slowly, allowing the membrane potential to drop to -80mV
- Na/K pump returns cell to normal
21
Q
absolute refractory period
relative refractory period
A
- when action potentials cannot be generated because Na channels are busy and must return to normal (larger axons have shorter refractory periods)
- when an action potential can be created, but it requires a larger stimulus because the cell is more negative than usual during hyper-polarization
22
Q
speed of conduction
A
- axon diameter-greater diameter means less resistance
- Saltutory conduction-current jumps down axon because of myelin-Na and K pumps in high concentration at Nodes of Ranvier (AP replenished)
23
Q
A fibers
B fibers
C fibers
A
- 5-20 um, myelinated, fastest conductors
- 2-3 um, myelinated
- 0.5-1.5 um, unmyelinated
24
Q
tetradoxin
A
blocks Na channels and therefore action potentials
25
EPSP
| IPSP
- excitatory post-synaptic potential-a graded potential that causes depolarization
- inhibitory post-synaptic potential-a graded potential that causes hyperpolarization
26
temporal summation
- summation of graded potentials that occur close to each other in time
- summation of graded potentials that occur at the same time in the same space
27
neurons connect to
muscles
glands
other neurons (electrical and chemical synapses)
28
Glutaminergic receptor
- glutamate cause depolarization
- glutamate opens Ca ligand-gated channels in post-synaptic cell
- removed by reuptake
29
GABA-ergic receptors
- GABA causes hyperpolarization-opens ligand-gated Cl- channels
- removed by reuptake
30
sensation
pain, temperature, proprioception, tactile, and special senses
31
pacinion corpuscles
- vibration, poking, quick changes in stimuli
| - large receptor field, quick to adapt
32
ruffini corpuscles
- skin stretch, sustained pressure
- large receptor field, slow to adapt
- mediate stereogenosis because they fire based on how much the skin is stretched
33
Meissner's corpuscles
- sensitive to shape and textural changes and vibration
| - small receptor field, quick to adapt
34
Merkel disks
- two point discrimination
- deep static touch like edges and sharp things
- small receptor field, slow to adapt
35
Muscle spindles
- spiral ending, located in muscle belly
- signal changes in length of muscle
- main mediator for proprioception
36
golgi tendon organs
- free nerve endings intertwined among connective tissue in tendon
- sense force muscle exerts (proprioception)
37
free nerve endings
bare dendrites, detect pain
38
intensity of stimulus
- frequency coding-smaller stimulation activates a smaller number of ion channels
- population coding-number of neurons activated (not all receptors have the same threshold)
39
conus medullaris
filum terminale
cauda equina
- structure at end of spinal chord (near medulla @ top)
- pia matter extension
- lumbar, sacral, and coccygeal nerve roots
40
what structures are involved in spinal reflexes?
sensory neuron, interneuron, motor neuron, sensory receptor and effector
called reflex arc
41
stretch reflex
- -muscle stretch/lengthening from blow to patellar tendon
- receptor: muscle spindles
- effect: muscle contracts to maintain length, muscle=effector
42
flexor (withdrawal) and crossed extensor reflex
- stimulus-pain (stepping on a tack)
receptor: nociceptor
- effects: coordinated ipsilateral limb flexion and contralateral limb extension for protection against harmful stimuli
43
- dermatomes
| - myotomes
- areas of skin supplied by a given spinal segment
| - areas of mm supplied
44
brachial plexus
lumbar plexus
sacral plexus
-supplies upper arm-from C5-T1 spinal segments (ex. C5/C6 innervates biceps brachii, C7 triceps)
-supplies lower limbs from L1-L5 (ex. femoral nerve from L3/L4 supplies quadriceps)
sacral plexus-supplies lower limbs from L4-L5, contains sciatic nerve (biggest peripheral nerve)
45
Meninges
thin membranes between bone and nervous tissue protecting brain and spinal chord
1. dura matter-splits for sagital sinus
2. arachnoid matter
3. pia matter
46
superior sagittal sinus
- large vein that takes blood away from the brain and drains CSF from CNS
- runs along sagittal plane between dural layers
47
falx cerebri
falx cerabelli
tentorium cerabelli
- separates right and left hemispheres of brain
- separates left and right hemispheres of the cerebellum
- separates brain from cerebellum
48
Cerebrospinal Fluid
- clear, colorless liquid containing water and ions (Na, Cl, Ca, K)
- bathes brain, provides shock absorption, and supports chemical environment for neural function
49
CSF Production
- secreted and contained in vesicles, sub-arachnoid space (between pia matter and arachnoid matter), and central canal in spinal chord
- Choroid plexus-ependymal cells (pump out Na and other solutes into ventricles -->concentration gradient draws plasma into vetricles by osmosis) and capillaries
50
CSF Function
1. physical
- buoyancy--reduces weight of brain and puts lets pressure on blood vessels and nerves
- shock absorption-padding
2. chemical-regulates extracellular environment for neurons, maintains increased Na and decreased K levels for choroid plexus
51
hydrocephalus
condition where rate of production of CSF is greater that rate of drainage-->leads to swelling of the brain (and skull in infants)
52
blood-brain barrier
- required for oxygen and glucose
- protects brain from chemical changes in the blood
- Oxygen moves by diffusion, glucose by facilitated diffusion
53
Blood-brain barrier: blood supplies
- internal caroted artery
| 2. vertebral arteries joined at brain stem to form basilar artery
54
role of astrocytes
-star-shaped with tentacles that attach to endothelial cells in the brain and release paracrines (proteins that form tight junctions between cells)
55
Blood-brain barrier function
- chemical protection from fluctuations in blood contents
- protects from changes in hormones, ions, and neurotransmitters
- contains some selective carrier proteins
56
- association tracts
- commissural tracts
- projection tracts
- axons that connect the same hemisphere
- axons that connect opposite regions (ex. corpus colosum)
- myelinated axons that connect brain areas with regions of the CNS
57
functions of
- frontal lobe
- parietal lobe
- occipital lobe
- temporal lobe
- insula lobe
- anteriorly: executive functions (decision making, personality), posteriorly: muscles and movement control
- sensation processing
- vision
- hearing and memory acquisition
- taste and smell
58
- primary motor area
- primary somatosensory are
- secondary/association areas
- where neurons most directly connect to mm
- where peripheral info is most directly received
- where meaning is applied to this information
59
Posterior column-medial lemniscus (PMCL)
- carries sensations for vibration (pacinion), proprioception (mm spindles and GTO's), stereogenesis (ruffini) and fine touch (Meissner's and Merkel)
- impulse travels up 1st order sensory neuron-->2nd order interneuron and crosses at medulla-->travels up medial lemniscus tract to thalamus-->terminates in ventral posterior lateral nucleus-->3rd order neuron sends axon to primary somatosensory cortex @ appropriate area
60
antereolateral spinothalamic tract
- impulses for tickle and itch, crude touch/pressure (anterior) and pain/temperature (lateral)
- 1st order sensory neuron enters posterior root ganglion-->2nd order crosses spinal chord and sends axon up to thalamus-->3rd order neurons extend to appropriate area of cerebral cortex
61
lateral corticospinal tract
- neurons descend through internal capsule and cerebral peduncle of midbrain
- descending neurons cross at medulla and cross at medulla-->exit through anterior grey horn in spinal chord to muscle
- distal muscles-precise, agaile, and skilled movements of hands/feet
62
anterior corticospinal tract
- descending neurons do not cross (some at spinal chord level) and exit through anterior grey horn
- muscles of axial skeleton
63
corticobulbar tract
- neurons descend through internal capsule and cerebral peduncle of midbrain, some decussate, some do not
- controls mm of the head
64
basal nucleii
-select movement patterns, stopping and starting movements, inhibiting extraneous movements and subconscious movement control (arm swing while walking)
65
medulla
- cardiovascular center, dorsal and ventral respiratory rate, heartbeat, blood vessel diameter, vomiting, swallowing (deglutition), sneezing, coughing, hiccuping
- consists of nucleii and all the white matter tracts
- vagus nerve (parasympathetic innervation of internal organs)
66
pons
-pontine respiratory group-increases respiration rate
-apneustic center-apnea-temporary cessation of breathing
-trigeminal nerve (V)-opthalmic branch (forehead, eyes, nose), maxillary branch (cheeks and top lip), and mandicular branch (chin, ears up to skull)
facial nerve (VII)-motor innervation of facial muscles, taste
67
Midbrain
- red nucleus-important for movement control in infants (no direct pathways to brain, thought to control crawling)
- substantia nigra-dopamine center
- superior and inferior colliculi-important for processing visual input and reflexes like pupil dilation (superior) and auditory input and reflexes like startle reflex (inferior)
68
reticular formation
- neurons that span brain stem
- mediates us being awake, conscious, and alert
- regulates muscle tone
- sensory filtering (filters out unimportant stimuli)
