Neurology Week 10 Flashcards
How is the nervous system organized
CNS and PNS
- Central Nervous System
- Peripheral Nervous System
How many pairs of spinal nerve are in the PNS
31
How many pairs of cranial nerves are in PNS
12
How can the peripheral nervous system be subdivided
Into 2 divisions
- Afferent
- Efferent
What is the afferent division
Carries info to CNS
“A in afferent is advancing to CNS”
Consists of (1) sensory & (2) visceral stimuli
What is efferent division
Transmits info from CNS to effector organs
What can the efferent nervous system be divided into
Somatic nervous system
Autonomic nervous system
What is the somatic nervous system
Fibers of motor neurons that supply skeletal muscles
Subjected to voluntary control
What is autonomic nervous system
Fibers that innervate smooth muscle, cardiac muscle and glands
Involuntary
What can the autonomic nervous system be subdivided into
Sympathetic and Parasympathetic nervous system
What does an autonomic nerve pathway consists of
2 Neuron chain which are
(1) Preganglionic neuron
(2) Postganglionic neuron
What are Preganglionic neurons
Synapses with cell body of postganglionic fiber in a ganglion outside CNS
What is postganglionic neuron
Sends axons that end on effector organ
How are most visceral organs innervated
Dually innervated by sympathetic and parasympathetic nervous systems
What is dual innervation
Innervation of single organ by both branches of autonomic nervous system
When does sympathetic dominance occurs
Fight or flight
When does parasympathetic dominance occurs
Rest and digest
Where can preganglionic neurons be found with regards to sympathetic innervation
Located between segments T1 & L2 of spinal cord
What is unique of preganglionic fibers for sympathetic innervation
Can synapse with >1 ganglionic neurons
What is the distribution of parasympathetic innervation like
Innervates organs of 3 main regions
- Cranial
- Trunk
- Pelvic
What is the type of fibers of parasympathetic innervation like
Long preganglionic
Short postganglionic
What is gray matter
generic term for collection of cell bodies (soma) in the CNS
What is white matter
generic term for collection of CNS axons
What are the major features that protect CNS from injury
Cranium & Vertebral column
Meninges
Cerebrospinal fluid
Blood Brain Barrier
What does Meninges consist of
3 meningeal membranes that wrap, protect and nourish CNS
Continuous with spinal meninges
What are the different mater found in Meninges
Dura (outer layer)
Arachnoid (middle layer)
Pia (inner layer)
Does the brain float in its own special CSF
Yes
What is Cerebrospinal Fluid
Shock absorbing liquid
- Surrounds & cushions brain & spinal cord
- Formed by choroid plexuses in ventricles (brain)
What is the function of CSF
Cushion delicate neural structures
Support brain
Transport nutrients, chemical messengers & waste products
How many ventricles can be found in the brain
4
Where can the 4th ventricle be found
Near the central canal of spinal cord
What produced meninges & CSF
Ependymal cells of choroid plexuses
Where does meninges & CSF circulate
Throughout ventricles
Where does meninges & CSF exit
4th ventricle
What happens to the meninges & CSF after flowing out of 4th ventricle
Flow in subarachnoid space and is reabsorbed into venous blood
How is CSF extracted
Through lumbar puncture from the subarachnoid space
Local anaesthesia is done prior to procedure
Patient can be either lying down to the side or sitting
What is the function of BBB
Isolates CNS neural tissue from general circulation
How is BBB formed
Formed by network of tight junctions between endothelial cells of CNS capillaries
What is BBB
Highly selective BBB that regulates exchanges between blood & brain
- Allows chemical composition of blood and CSF to differ
- Selectively isolate brain from chemicals that could disrupt neural function
How is the brain nourished
Dependent on constant delivery of O2 & Glucose by blood
Does the brain utilize and store glucose
No. Only uses glucose but cannot store it
Does the brain need O2 for energy production
Yes
What is the weight of the brain relative to body weight
2%
How much CO goes into the brain
13 - 15%
What happens if the brain is deprived of O2
Brain damage occurs
What are the general functions of CNS
Subconsciously regulate homeostatic responses
Emotions
Voluntary Movement
Perception
Engage in higher cognitive processes
What are the componentsof the brain
Brain stem
Cerebellum
Forebrain
- Diencephalon
- hypothalamus
- thalamus
- Cerebrum
- basal nuclei (basal ganglia)
- cerebral cortex
What makes up the brain stem
Midbrain, pons, medulla
Where can thalamus be found
Medially above hypothalamus
Where can basal nuclei be found relative to thalamus
Lateral to thalamus
What is the function of cerebral cortex
Sensory perception
Voluntary control of movement
Language
Personality trait
Sophisticated mental events
- thinking
- creativity
What is basal nuclei function
Inhibition of muscle tone
coordinating slow sustained movements
suppress useless patterns of movement
Where can the central sulcus be found
Between frontal and parietal lobe
What are the general functions of nervous system
Sensory
Communicative
Integrative
Motor
Respond to both internal & external stimuli
What does the CNS consists of
Brain and spinal cord
What does PNS consists of
Nerve fibers
Where do most of the cranial nerves originate from
Brain stem
How can the spinal cord be divided into from top to bottom
Cervical cord > thoracic cord > lumbar cord > sacral cord
Where can coccygeal nerve be found
At the tip of the end of spinal cord
How many nerves are found in each of the different spinal cord segments
Cervical - 8
Thoracic - 12
Lumbar - 5
Sacral - 5
Coccygeal - 1
Where do the rest of the nerves attached to after the spinal cord
Cauda equina (Horse tail?)
What is the 3rd system that ANS can influence
Enteric nervous system which affects digestive organs only
The mini brain of intestines and stomach
What is ganglion
Cluster of neuron cell bodies
What is the sympathetic division called
Thoracolumbar division
What do adrenal medulla only have
preganglionic neuron
What is the parasympathetic division called
craniosacral division
What is the difference in pre/post-ganglionic neurons between thoracolumbar and craniosacral divisions
Craniosacral divisions have longer pre-ganglionic neurons and shorter post-ganglionic neurons compared to thoracolumbar
What does the vagus nerve innervate
Innervates and supplies majority (75%) to the thoracic and abdominal organs
What are ventricles in the brain
Fluid filled cavities in the brain
What does the thalamus do
Relay sensory inputs to CNS except smell
Motor control function
Degree of consciousness
What does hypothalamus do
Homeostatic function
What does cerebellum do
Balance & coordination of muscle activity
Enhances muscle tone
What does brain stem do
Respiratory function
Vital for survival. If its dead, u dead
What does the frontal lobe consists of
Prefrontal cortex & motor cortex
What is the purpose of prefrontal cortex
Complex cognitive decision making
Personality
Social behavior
What is the parietal lobe used for
Somatosensory processing
What is the occipital lobe used for
Visual
What is the temporal lobe used for
Memory formation
What is the somatotopic map
Relative proportion of somatosensory cortex devoted to reception of sensory input from each area
Distribution of motor output from primary motor cortex to different parts of body
How is the distribution of somatotopic map like
Precise distribution is unique to individual
It is use-dependent modification
What is somatotopic map also known as
motor and sensory homunculus
What is the spinal cord
Long slender cylinder of nerve tissue
What does the spinal cord extends to
Extends from the brain stem > vertebral canal > spinal nerves
How is the spinal cord protected
Enclosed by protective vertebral column
How are the white matter organized
Into tracts to form bundles of nerve fibers with similar function
How to differentiate between white and gray matter
H symbol is gray matter, Surrounding is white matter
What are dermatomes
Area of skin supplied by single spinal cord level or one side by a single spinal level
What can dermatomes be used for
Localizing lesions to specific spinal nerve or level for neurological examination
What are myotomes
Portion of skeletal muscle innervated by single spinal cord level or one side by single spinal nerve
Are each skeletal muscle usually innervated by nerves from >1 spinal cord level
Yes
How are myotomes used
Likewise to dermatomes, used to test movements at successive joints to help localize nerve or spinal cord lesions
How does the afferent sensory nerves enter the spinal nerves
Through posterior ramus to dorsal root
How does the efferent sensory nerves leave the spinal nerves
Through the ventral root to anterior ramus
What does the posterior and anterior rami supply
Supplies spinal nerves T1 - L2
What are nerve plexuses
Network of nerves that come together and then redistribute themselves out with different distribution of nerves into limbs
Is nerve plexuses somatic or visceral
Both
What is an advantage of using nerve plexuses instead of single spinal nerve
Less likely to cause total paralysis of muscle innervated by nerves from that plexus
What are the nerves like when it exists the plexus
Contains fibers from different spinal nerves
Does the plexus affect dermatomes sensing
No. It will eventually branch out to its respective areas
The BBB is formed by network of tight junctions between endothelial cells of CNS arterioles. True or False
False
The dorsal root of spinal cord carry ___ signal while ventral root carry ___ signal
Sensory; motor
What are neurons
basic functional units / conducting cells of nervous system
What do neurons do
Processes and transmits info in electrical & chemical form
What is the structure of neurons
Cell body (soma)
Short, branched dendrites
Long, single axon
What is the soma
contains organelles essential for survival (nucleus, mitochondria, RER)
What are the short branched dendrites
highly branched and receives info from other neurons
What is the long single axon
Carries electrical signal (action potential) to target
What are the different neurons
bipolar, unipolar and mulitpolar
What is the bipolar neuron
bipolar neuron with 2 processes separated by cell body
what is unipolar neuron
unipolar neuron have single elongated process with cell body located off to the side
what is multipolar neuron
multipolar neurons have >2 processes - single axon & multiple dendrites
What does the neuroglia do
Supports neuronal function
What % of the NS is neuroglia
50%
What are the different neuroglia
Astrocytes
Myelinating glia
Microglia
Ependymal cells
MAME
What do ependymal cells do
produces CSF
what does microglia do
phagocytic role to remove cell debris, wastes
modified immune cells
What are the 2 sub-types of myelinating glia
oligodendocytes (CNS)
schwann cells (PNS)
What do astrocytes do
regulates chemical content of extracellular space
Are neurons and muscle cells excitable tissues
yes
What happens when neurons and muscle cells are excited
Produced electrical signals
neurons - receive, process, initiate and transmit messages
muscles - initiate contraction
Are electrical signals important to function of NS
yes
What are the different stages of neural comms
polarization
depolarization
repolarization
hyperpolarization
How are electrical signals produced
By changes in ion movement across plasma membrane
- event triggers membrane potential change
- alters membrane permeability = alters ion flow across membrane
What are the gated channels in neurons
voltage gated
chemically gated
mechanically gated
thermally gated
what are graded potentials
local changes in membrane potential
- occurs in varying degrees of magnitude
- stronger trigger = larger resultant graded potential
How are graded potentials spread
By passive current flow
- current = flow of electrical charges
- resistance = resistance to electrical charge movement
How do graded potentials die out
Over short distances
What are action potentials
Brief, rapid, large changes in membrane potential
Is it possible for the action potential to reverse
only if it is graded potential
What happens inside excitable cells during action potential
Inside of cell transiently becomes more positive than outside
What conditions lead to an action potential
marked changes in membrane permeability & ion movement
What channels are involved for action potential
Voltage gated Na+ & K+ channels
How are action potentials relayed through neuron
1) Dendrites receives incoming signals from other neurons (Input)
2) Soma initiates action potential through axon hillock (Trigger)
3) Axon conducts AP in undiminishing fashion over long distances (Conducting)
4) Axon terminals releases neurotransmitters that influences other cells (Output)
What is the purpose of refractory period
Ensures one way propagation of AP
Limits frequency of AP
Can an AP be initiated in region that has just undergone an AP
No
How is the fashion in which an AP occurs
All or nothing
What is the advantage of an AP acting in ‘all or nothing’ fashion
Allows discrimination of stimuli & weak stimuli do not initiate AP (No hypersensitivity)
How does one measure the strength of a stimulus
Frequency of AP (magnitude of AP is the same each time)
What does myelination do
Increase speed of conduction of AP
What does the fiber diameter do
Influences velocity of AP propagation
What is myelin
Thick layer of lipids
What is the function of myelin
Insulates electrical transmission across axon
What are the 2 forms of conduction
Contiguous & Saltatory conduction
What are synapses
junction between neurons
what are electrical synapses
neurons connected directly by gap junctions
what are chemical synapses
chemical messenger transmits info 1 way across space between 2 neurons
What makes the majority of synapses in human NS
chemical synapses
What is the process of synaptic transmission
Depolarization
Influx of Ca2+
Docking
Release of neurotransmitter
Binding of neurotransmitter to receptor
What do drugs & diseases do to synapses
modify synaptic transmission by altering its mechanism
How are neurons linked
converging and diverging pathways
what are converging pathways of a neuron
given neuron may have many other neurons synapsing on it
what are diverging pathways of a neuron
branching axon terminals so 1 cell synapse influences other cells
What are the different neurotransmitters
Acetylcholine
Dopamine
Glutamate
Gamma-aminobutyric acid (GABA)
What does GABA do
primary inhibitory neurotransmitter in CNS (IPSP)
What does glutamate do
primary exhibitory neurotransmitter in CNS (EPSP)
What does dopamine do
Involved in many pathways in CNS
- muscle movement
- reward pathway
What is the effect of ANS on lungs
sympathetic
- Dilates bronchioles
- inhibits mucus secretion
parasympathetic
- constricts bronchioles
- stimulates mucus secretion
What is the effect of ANS on digestive tract
sympathetic
- contracts sphincters to prevent forward movement of contents
- decreased motility
- inhibits digestive secretions
vice versa for parasympathetic
What is the effect of ANS on urinary bladder
sympathetic = relaxes
parasympathetic = contracts (emptying)
What is the effect of ANS on eyes
sympathetic = dilates eye and adjust for far vision
parasympathetic = constricts and adjust for near vision
What is the effect of ANS on sweat glands
sympathetic = increased secretion by sweat glands for cooling body
parasympathetic = none
What is the effect of ANS on salivary glands
sympathetic = small volume of thick salvia rich in mucus
parasympathetic = large volume of watery saliva rich in enzymes
What is the effect of ANS on adrenal medulla
sympathetic = stimulates epinephrine & norepinephrine
parasympathetic = none
What are the neurotransmitters produced by ANS
Sympathetic
- preganglionic = ACh
- postganglionic = NE
Parasympathetic
- preganglionic = ACh
- postganglionic = ACh
What are the origin of ganglionic fibers in sympathetic system
preganglionic = thoracic & lumbar region of spinal cord
postganglionic = sympathetic ganglion chain / collateral ganglia
Where can collateral ganglia be found
Halfway between spinal cord & effector organs
What are the origin of ganglionic fibers in parasympathetic system
preganglionic = brain & sacral region of spinal cord
postganglionic = terminal ganglia (in or near effector organs)
What is EPSPs
Excitatory Post-Synaptic Potentials
What is IPSPs
Inhibitory Post-Synaptic Potentials
What happens when voltage in neuron exceeds threshold at -55mV
Action potential occurs
WWhat are the stages of an action potential
1) Resting - Na+ & K+ channels closed
2) Stimulus - Na+ channels open & Na+ flows in
3) Threshold - Goes past -55mV, more Na+ channels open (Depolarization)
4) Peak - Na+ channels close, K+ channels open (30mV)
5) Repolarization - K+ rush out
6) Overshoot - membrane potential goes down to -90mV, K+ channels close, Na+ K+ pump restores initial conditions & resting potential
What ion is the main driver of membrane potential
K+
What is the difference between contiguous & saltatory conduction
Saltatory conduction occurs at axon with myelin sheaths whereas contiguous conduction does not
where is AP initiated
axon hillock
What do EPSPs and IPSPs do
EPSP = brings graded potential closer to threshold
vice versa for IPSPs
what channel is responsible for refractory period
Na+ channels
outward movement of ___ ions rapidly restores negative resting potential
K+
what ion is the resting membrane most permeable to
K+
what is the life cycle of CSF
- produced by ependymal cells of choroid plexuses
- circulate throughout ventricles
- exit 4th ventricle
- flow in subarachnoid space
- reabsorbed into venous blood
what organ only has preganglionic nerve
adrenal gland
where does spinal cord end
L1 vertebrae
What does sympathetic & parasympathetic ganglionic fibers originate from
sympathetic = thoracic & lumbar regions of spinal cord
parasympathetic = brain & sacral region of spinal cord
what does the grey and white matter contain
grey = soma collection
white = axon axon collection
how are graded potentials spread
passive current flow
visceral motor nuclei in the brainstem & spinal cord are known as
preganglionic neurons
bundles of axons in peripheral NS are known as
nerve fibers
which neural cell has phagocytotic properties
microglia
excitatory neurotransmitters cause ____, inhibitory neurotransmitters cause ___
depolarization; hyperpolarization
gray matter of the spinal cord consist of
neuronal cell bodies & unmyelinated axons
what does damage to basal nuclei lead to
difficulty starting voluntary movement & decreased muscle tone
which area acts as a filter for sensory info coming into sensory cortex
pons
all ___ pathways send info to the ___ when motor commands are issued
motor / cerebellum
translation of a stimulus into AP is known as
transduction
