Bowman- Physiology of CNS Flashcards
What is general functions of CNS
Patterns of action potentials encode information leading to:
- Sensory perception
- Information processing, integration and storage
- Motor and behavior
What is white matter?
High density of myelin covering axon pathways (few neurons)
What is gray matter?
High density of neurons and denddrites (axons are present)
What is a nucleus?
Cluster of neurons within CNS
What is ganglion?
Cluster of neurons outside of CNS
What is a tract
Axons within CNS that travel as a group (name based on region of origin and termination)
What is a pathway?
Similar to tract but relates more to synaptically connected neurons performing a function
What is neuroglia?
“Glue” that holds CNS together.
What do astrocytes do?
Help to maintain extracellular environment in CNS, in normal conditions and in response to damage.
- Cell body with several main branches
- Astrocyte processes contact neurons and surround synaptic endings
- Contact capillaries and connective tissue at surface of CNS, the pia mater.
- Take up K and neurotransmitter substances, which they metabolize, degrade or recycle.
What do oligodendroglia do?
- Produce myelin in CNS; increase speed of conduction
- single oligodendrocyte will myelinate multiple axons in CNS
What do microglia DO?
latent phagocytes in CNS
What do ependymal cells do?
Line ventricles and CSF production (CNS)
What are satellite cells/
Similar to astrocytes but in PNS
What are schwann cells?
Slimilar to oligodendrocytes but in PNS. Will only myelinate single axon in PNA
Inhibitory inputs to neuron tend to be more on the ___ ____
Cell body
Excitatory neurons tend to be more on ____
dendrites
The axon hillock has a high concentration of which type of channel?
VG Na channel
Types of neuron cell types?
Unipolar
Pseudounipolar (sensory neurons)
Bipolar (interneuron)
Multipolar (classic neuron)
What is point of axonal transport?
Transport substances up or down neuron. Like a guidewire in axon.
What is kinesin?
Performs anterograde axonal transport, powered by ATP. (transport from soma toward axonal terminals)
What is dynein?
Axonal transport in retrograde direction. Takes synaptic vesicle membrane to soma for lysosomal degradation
What does myelination do?
- Greater conduction velocity
- increases effective membrane resistance (lenght constant)
- Decreases capacitance
- Restricts AP generation to nodes of ranvier
What are benefits of myelination?
- Fast reflexes
- Complex mental processing
- Metabolic advantage
Relative size a fibers?
Largest type. Largest to smallest subtype: alpha, beta, gamma, delta
Relative size b fibers
Myelinated 1-3 um
Relative size C fibers
unmyelinated fibers 0.1-2.5 um
What are a-alpha fibers responsible for?
motor, proprioception
What are a-beta fibers for?
motor, touch, pressure
What are a-gamma fibers for?
motor, muscle tone
What are a-delta fibers for?
Pain, temperature, touch
What are b-fibers for?
Preganglionic autonomic
What are c-fibers for?
Dull pain, temperature, touch, POSTganglionic autonomic NO MYELIN
What is a type of electrical synaptic signaling?
Gap junctions
What is example of chemical synaptic signaling?
Neurotransmitter mediated
Types of synaptic signaling?
- Neuron-neuron (classic)
- Neuron-Glial
- Extra synaptic (NT can have action at locations distal to original synapse)
What are gap junctions
- Low resistance pathway between cells that allows current to flow directly form one cell to another
- Allows ecahnge of small molecules b/w cells
- Fast and BIDIRECTIONAL
- Regulated by voltage, intracellular pH, Ca_, and G protein-coupled receptors
3 Types chemical synapses?
1) Small molecule neurotransmitters
2) neuropepties
3) gaseous tranmitter
How does small-molecule neurotransmitters work?
Ach, glutamate, GABA
- Vesicle transporter concnetrates neurotransmitter into vesicles, fuse with presynaptic cleft and exocytosed to synaptic cleft.
- NT binds to postsynaptic receptor
How to neuropeptides function?
- Neuropeptide is packaged in cell body and transported to nerve terminal by fast axonal transport
- Active peptide formed when cleaved from larger polypeptide that contains several neuropepties
- Present in large, electron-dense vesicles
- Transported to axonal terminal by axonal streaming, VERY SLOW RATE
- Relased at neuronal terminals in response to action potentials in same manner as neurotransmitter
What is a neurotransmitter?
- Must be present in presynaptic terminal
- cell must be able to synthesize the substance
- -released upon delorazation of presynaptic embmrane
- Specific receptor on post synaptic membrane (+/- extrasynaptic locations)
Where are non-peptide transmitters/classic NT synthesized?
Synthesized and packaged in nerve terminal
Neurotransmitters are synthesized in ___ form while peptide is _____ from larger polypeptide in order to form active peptide.
active; cleaved
How are neurotransmitters packaged vs neuropeptides?
Neurotransmitters are in smalll, clear vesicles
Neuropeptides in large, elctron-dense vesicles
Where are neurotransmitters released? Neuropeptides?
Neurotransmitters released into synaptic cleft
Neuropeptides released some distance form postsynaptic cleft. There may be no well-defined synaptic structure
How are neurotranmitters actions terminated? Neuropeptides?
Neurotransmitters are terminated because of uptake by presynaptic terminals via Na powered active transport
Neuropeptides terminated by proteolysis or diffusing away
Comparative lenght of action of neurotransmitters vs neuropeptides
Neurotransmitters have short latency and short DOA (msec)
Neuropeptides have longer latency and persist for many seconds
What are examples of class I neurotransmitter
Acetylcholine
What are class II neurotransmitters? (biogenic)
Norepi
Epi
Dopamine
Serotonin
Histamine
Class III neurotransmitters (Amino acids)?
GAMA
Glycine
Glutamate
Aspartate
What is substance P?
Neuropeptide that sends pain stimulation up to brain from spinal cord
What is methionine enkephalin
AKA (opioid peptide). Endogenous opioid that binds to opioid receptor and decreases substance P, and decreases opioid modulation, decreasing pain perceived
What is gaseous neurotransmitters?
Not released from vesicles
Nitric oxide
Carbon monoxide
What does nitric oxide do in cells
Ca/CAM complex goes to eNOS (endothelial nitric oxide), where it binds with arginine to make nitrous oxide
This causes vasodilation
Occurs in brain and blood vessel
What does glutamate stimulate?
NMDA, AMPA and metabotropic (Gcoupled protein) receptors
EXCITATORY
What is signal for neurotransmitter release?
Ca
What receptor brings glutamate into vesicles?
V-Glut
Why is it important to remove glutamate from synaptic cleft?
- Potent neurotoxin that can cause excitotoxicity
- Can cause lots of Ca into cells signaling apoptosis (cells to die)
How is glutamate recycled?
- Speicifc glutamate transporters exist on presynaptic and postsynaptic cell membranes fro reuptake
- Transport 3 Na, H, and glutamate into cell. K tranported to ECF
- glial cells can also take up glutamate and convert it to glutamine
*
What does ion flow depend on?
Electrochemical gradient of permeant ions
Ix= Gx x (Vm-Ex)
What is result of excitatory response?
- Increased Na influx
- Decreased Cl influx of K efflux
- Change in receptor exprsesion/enzymatic/metabolic activity (delayed effect)
What creates inhibitory response?
- Increased Cl influx or K efflux
- pre/post synaptic
- Change in receptor expression or enzymatic/metabolic activity
How much does each EPSP change membrane potential? What consequenc does this have?
0.5-1 mV
Need multiple excitatory responses in order to elicit action potential
How long does each individual EPSP change threshold?
<15 ms
What is facilitation?
Sub-threshold stimulation
What is divergence of neuronal circuits?
One axon has amplified response downstream
- One axon can “amplify” signal in same tract
- Also can diverge into multiple tracts to transmit signal to separate area
What is convergence?
Gathering of multiple neuron terminals onto a single source
This allows enough spatial and temporal summation so that action potentials can fire
What is reciprocal inhibition?
- Type of circuit where excitatory fiber also has limb to inhibit the antagonist muscle
- i.e- when extend leg, quads need to fire while hamstrings need to relax
What is a reverberatory circuit?
Output neuron sends collateral nerve fiber back to own dendrites/soma to restimulate itself.
Alkalosis ____neuronal excitability
increases
Acidosis greatly _____ neuronal activity
depresses
Hypoxia greatly _____ neuronal excitability
Decreases
What are associated nerves with cerebral cortex?
Cranial Nerve I
The cerebral cortex is dependent on lower brain regions for what?
Wakefulness
What are primary functions of cerebral corex?
- Cognition
- Large memory storehouse
- Essential for higher level thought (bold= ones mentioned in class)
- Fine tune lower brain function
- sensory perception
- Learning
- Motor planning and voluntary movement
- language
The 2 hemispheres of cerebral cortex are connected by the __ ___
corpus callosum
What is function of frontal lobe responsible?
- Planning and carrying out motor behavior
- Speech (broca’s area, inferior frontal gyus of dominant hemisphere)
- “Intellectual activities”
- Personality and emotional behavior
What is function parietal lobe?
- Sensory perception and processing (somatosensory cortex/parietal association cortex)
- Projections to frontal lobe carrying somatosensory information modulates voluntary motor behavoir
- Parietal association cortex processes info from occipital lobe to frontal lobe to influence motor heavior
- Sends somatosensory information fo wernicke’s area
- Establishment of spatial context
What is function of occipital lob?
- Visual perception and processing
- Projection to frontal eye fields influence motor behavior of eyes
- Projection to midbrain modulates convergent eye mvmt, pupillary constriction and accommodation
What is function of temporal lobe?
- Processing and perception of sound and vestibular info
- facial recognition
- optic pathways transverse temporal lobe
- emotional behavior
- ANS regulation
- Learning and memory (hippocampus)
What is the supplementary motor area?
Cortical motor area in brain. Coordinates bilateral movement
What is premotor area?
Coordination of multiple muscle groups working to accomplish something (i.e. stabilize arm/shoulder while working with hands)
High concnetration of mirror neurons. Important when watching a new task and then performing task yourself.
What is the cingulate motor area?
Evoke similar motor cortex stimulation but higher stimulus needed
Which region of brian contains highest region of neurons?
Cerebellum
What cranial nerve is the cerebellum associated with?
VIII- vestibulocochlear (hearing/balance)
What is primary function of cerebellum?
- Coordination and equilibrium
- adjust when load changes/door releases when pulling so we don’t fall over
- Sensory association/language
- Essential for highly coordinated muscular movement (tennis, talking, typing)
- motor learning/muscle memory
What are basal ganglia primary functions?
- Influences thalamocortical motor inhibition
- Control of fine motor movements and relative intensity, direction and sequencing of complex movement patterns
Where does basal ganglia receive input?
Direct input from cerebral cortex and subthalamic nucleus
No input from spinal cord
What is lost in basal ganglia with parkinson’s disease?
Dopaminergic neurons in substantia nigra degenerate. All we have is ACh released unopposed, so lots of involuntary motor movmeents
What are primary functions of brainstem?
- Sensation motor control head, nekc, faces
- input of special senses
- mediate ANS function (CO, BP, Peristalsis, pupillary constriction)
- Conduit for ascending and descending motor pathways that carry sensory and motor info
- Reticular formation receives summary of infothat enters SC and brain stem, filters info
- is a “light switch” required for upper level brain centers
What does the brainstem consist of?
Medulla
Pons
Midbrain
Which cranial nerves are associated with medulla?
CN VIII-XII
Vesibulocochlear (VIII)
Glossopharngeal (IX)
Vagus (X)
Spinal accessory (XI)
Hypoglossal nerve (XII)
Primary functions of medulla
- Subconscious CV and respiratoyr control
- Early relay nuclei in auditory, balance/equilibrium, gustation, head and neck control input
- Brainstem reflexes
What are fucntions of pons?
- Respiratory control
- Urinary control
- Motor control
- sensation motor control face
- Vental: pontine nuclei relay movement and sensation info from cortex to cerebellum
- Dorsal: tast and sleep
What is cranial nerves associated with pons?
V-VIII
Trigeminal, abducens, facial, vestibulotrochlear
What are cranial nerves associated with midbrain?
III-IV
oculomotor, trochlear
What are functions of the midbrain?
- Acoustic relay and mapping
- eye movement, lens and pupillary reflex
- pain modulation (descending pain pathway)
- Contains nuclei and relay pathways critical for motor coordination (substantia negra)
Which cranial nerves are associated with thalamus?
II
What are functions of thalamus?
- Important “gating” area
- regulation of cortical activation (Attention and consciousness)
- Filters what information we want to send to our consciousness
- Visual input
- sensory and motor relay/coordination b/w cerebral hemispheres and lower CNS regions
What are functions of the hypothalamus?
- Autonomic/endocrine contorl
- Superchiasmatic nucleus
- circadian rhythms
- Motivated behavior
- reward centers
WILL HEAR LOTS ABOUT IN ENDOCRINE
What are primary functions of amygdala
Social behvaior
Expression of emotion
What is primary function of hippocampus
Memory
Which nerves are conducted in dorsal root?
Sensory
Afferent
What nerves travel in ventral root?
Motor neurons (efferent)
What are functions of spinal cord?
Sensory input
reflex circuits
somatic and autonomic motor output
