Wolff’s law
Bone: every change in form and/or function of bone is followed by a definite change in the internal architecture and external conformation, as it aligns with mathematical laws
this type of bone growth (app or inter) can only occur whil the epiphyseal plate is growing
interstitial
interstitial growth bone occurs in
occurs at hyaline cartilage of epiphyseal plate, increases length
appositional bone growth occurs in
endosteum and `periosteum, puts down new bone, for width
Nerve def
bundle of axons, conduct electricity
receptor def
special sensory cells that detect stimulus
Nervous system subdivisions
CNS: brain, spinal cord PNS: nerves, receptors -> sensory ->motor --> Somatic -->Autonomic --->Parasympathetic --->sympathetic
Neuroblastoma (what is)
most common neural cancer in childhood, <2yo. Endocrine and neural tissue, adrenal gland
describe what these do:
- soma (perikaryon) of neuron
- Dendrite
- Axon
- Schwann cell
- Axon hillock
- telodentrites (axon terminals)
- soma (perikaryon) of neuron: integration center
- Dendrite: receptor
- Axon: transmit AP
- Schwann cell: insulate axon (myelin) speed up AP
- Axon hillock: where electrical current begins
- Telodendrites (axon terminals): transmits signal to next cell at the synapse
interneurons are only located in
the CNS
list the neuron structural classifications, what are they are base on?
Based on the # processes the neuron has
unipolar: 1 attachment to body (sensory neurons)
multipolar: 3 or more attachmt (typical neuron image) 99% of neurons, includes interneurons (anaxonic)
bipolar: to attachment (rare in adults, eyes have)
all sensory neurons are multi, uni or bi polar?
unipolar
List the glial cells in the CNS (4)
- astrocytes: blood-brian barrier
- oligodendrites: form myelin sheaths, speed up AP
- ependymal cells: produce CSF
- microgial: immunity, produce Tcells
List the glial cells in the PNS (2)
- satellite cells: many roles, mainly with nutrient flow and waste removal
- schwann cells: make myelin, speed up AP
ganglion is a
collection of cell bodies
Plexus (plexi) def
net-like structures formed by interconnecting nerves
any barrier between particles (- and +) that attract each other builds what
Potential (energy or the ability to do work)
voltage def
difference in charge between two sides
measure of potential energy ( (electrical potential)
electromagnetic gradient (electrical current) def
the movement of electrons essentially.
the difference in voltage across membrane (or two other sides), affecting the rate of particles diffusing
Ohms law states that
current is directly proportional to the gradient (more difference between two sides, faster the diffusion)
V=IR
voltage=current x resistance
the gradients pulling on a particle are (2)
electromagnetic
concentration
if both of these go in the same direction, diffusion happens faster
how do we ensure that AP only travels in one direction?
because of hyperpolarization, even if stimulus there, not goint to initiate another AP
Stimulus>depolarization> AP (axon hillock down- down the axon)> efferent neuron (ie: contraction of muscle)
membrane potential definition
electrical potential maintained by a plasma membrane
what maintain the resting membrane potential?
Na/K pump
RMP: ~ -70mV (K responsible for this)
membrane is somewhat leaky, the Na/K pump compensates for this and maintains the resting potential
Why is RMP measured in negative numbers?
because we are measuring the comparison between the inside and the outside (rmp -70mv becuase it is 70mv “less”)
how do we change the polarity of neurons (depolarization)
by lowering the resistance of the membrane- by opening the ion channels
open ion channels>dec resistance, inc ion flux> cause electrical current
What are ligand-gated ion channels?
channels that open/close when a chemical (NT) binds to it
during depolarization, towards what is the polarity moving?
towards 0
gradients tend to want to reach”equilibrium”
how do we repolarize the neurons?
K ions flow out of the membrane, repolarizing
however since K is lower to move across, we cause hyperpolarization(NA/K pump reestablishes)
what is the original stimulus for depolarization (causing the AP)?
the LIGAND on the channel
the Neurotransmitters
ACh is most common
most comon NT is…
Acetylcholine (ACh)
impulse def
electrical flow in a cell
what are esterases?
molecule that deactivates a NT via hydrolysis (to keep it from keeping ion channels open and destroying the cell)
how do voltage gated ion channels work?
they open/close in response to the nearby potential– the threshold
threshold for AP
-50mv, all or nothing
does more NT mean more ion channels are opened?
yes, increased stimulus keep the channels open long enough for the signal to cause the AP
the peak after depolarization means that
the sodium that has flowed into the membrane caused a flip in the polarity, making he inside more positive and the outside more negative
continuous propagation def
Voltage-gated channels are ligned up along axon, Na diffuses into the next channel, causing an increase until threshold reached- starting the next voltage-gated channel
together along with hyperpolariz, ensures that the AP only travels in one direction
“All or none” rule
if you stimulate an axon to threshold, you will have an AP
What is the Refractory Period?
time during which the membrane cannot be depolarized (becuase of hyperpolarization) no matter how big the simulus is, no AP can occur
def:
depolarization
repolarization
hyperpolarization
depolarization: Na ions in, causing a decrease in polarity inc in potential
repolarizat: Na channels close, K ions open, K out inc polarity
hyperpolarization: caused by K flowing out, polarity switches, more + inside, - outside (AP cannot occur)
Saltatory conduction def
APs all-or-nothing, to make them faster, myelin (nonconducting) insulates parts of axon, allowing AP to “jump” areas (nodes of ranvier). essentially keeps all the charge insulated within the axon so it can travel faster.
myelinated neural tissue is ___
white matter
grey matter is non-myelinated neural tissue in the CNS
classification of synapses:
- Interneuronal: neuron to neuron
-pre and post synaptic
AxodendriticL most common- between axon terminal and dendrite - Neuromuscular: neuron to muscle
what is the synaptic cleft
the fluid filled space between pre and post synaptic neurosn
Parts of the synapse (5)
- Axon terminal of the presynaptic neuron
- synaptic end bulb
- synaptic cleft
- vesicles of ACh
- Post synaptic neuron (postsynaptic membrane with ligand gated channels)
Two types of synapses
Chemical synapse: controlled by NT, unidirectional, most common
Electrical synapse: bridge junctions, no control, if one fires they all do, communication in both directions
Steps in chemical synapse (7)
- AP in presynaptic opens Na in presyn bulb
- Na ions flow in causing exocytosis of NT
- NT diffuses across cleft
- NT binds to ligand-gated receptors on postsynaptic membrane
- Opens the Na + K channels on postsyn
- Na in, K out, depolarizing the mebrane
- Depolariz big enough= AP
what do inhibitory synapses do differently?
they only open K channels, so they hyperpolarize the membranes
steps in electrical synapse (4)
- protein channels interconnect the membranes on neurons
- AP on 1st membrane brings Na in
- Na diffuses through the channels and depolarizes the other cell
- K moves out
Only seen in neurons controlling jerk movements of eye or hormone release by pituitary gland
strength of a stimulus measured by (2)
- wave summation (faster stim interpreted as more)
2. recruitment: stimulate a bigger area= more receptors recruited
what is a generator potential
a stimulus in an area that lacks voltage-gated channels= no AP there but can generate one (body of neurons)
what is a graded potential
below threshold stimulus, doesn’t open channels until reaches threshold
in chemically-gated channels at synapse this is called a receptor potential
After the synapse (NT released) is a postsynaptic potential
EPSP
exitatory post synaptic potentials
NT opens Na + K channels at once-> AP is generated
IPSP
inhibitory post synaptic potential
NT (binding ot receptor proteins) reduces the neurosn ability to cause AP at postsyn neuron (NT affects permeability of K only)
what does synaptic facilitation mean (or entail)
neurons receive stimulus from EPSP and IPSP all the time, most kept near threshold so that if needed AP can be generated by only increasing stimulus from E or I by a little
presynaptic inhibition is
when the release of an excitatory NT is reduced by the activity of another neuron
Response pathways (3 kinds) ratio of stimulus to outputs
- Divergent: one stimulus, multiple outputs (tripping, hands out)
- Convergent: multiple stimulus, one output (skin, heat reflex)
- Reverberating: one stimulus, leading to continued output (can be amplified, positive loop)
these can be serial: for speed
or parallel: slower, but for many things
Types of processing for our neural pathways (2)
Serial: for speed (few synapses)
Parallel: lots of divergence, can take on many things, slow (why a smell can bring memories)
name the common NT classifications overall (3)
- Amino Acids
- monoamines
- Peptides (opioids)
List the Amino Acid NT (2)
- glutamate: in fast excitatory synapses (most common 75%) msg: umami flavor
- GABA: in inhibitory synapses,, virtually all cells, sedatives enhance inhib effects of GABA
what were the first man-made molecules that enhance the effects of GABA?
Diazepam and Librium
List the Monoamines NT (+ biogenic amines) (4)
- dopamine: beh, cognintion, voluntary movement, imp in reward process
- norepinephrine: adrenaline, inhib and excitatory
- histamine: small molec, but responsible for 23 physiological fn
- serotonin: appetite, sleep, learning, memory, temp, cardio and endocrine system…etc. LSD mimics its effects
What mimics the effects of serotonin?
LSD
too little serotonin in thought to be one cause for ___?
depression
serotonin reuptake inhib: zoloft, prozac
List the NT peptides (4)
- Morphine: most abundant, from poppy seedpods Friedrich Serturner (1817)
- Endorphins: second wind, prevent nerve cessl from releasing more pain signals
- codeine
- hydrocodone
Acetylcholine (ACh)
most common NT, excitatory on skeletal muscle, inhib on cardiac muscle
Novel messengers (other NT’s)
Nitric oxide: blood vessel health
ATP and ADP
ions ie ZInc
addiction is described in these 2 ways
physiological addiction: ie nicotine
emotional-based (likely tied to dopamine release)
Physiological addiction of nicotine: basics
crosses blood-brain barrier 10-20 s after inhalation, inc levels of several other NT, esp dopamine leading to pleasure and relaxation
2 types of NT receptors
Channel-linked: fast acting
depending on excitatory or inhibitory, it opens channels allowing the ions to flow
G-protein linked: indirect and slow, long lasting.
use secondary messengers (cAMP) to open ion channels
ie dopamine
Neuropathy def
damage to the nerves of the peripheral nervous system
Botulinium is what
a neurotoxin produced by Clostridium botulinum- it stops the exocytosis of ACh vesicles
Botox has this toxin
what is retrograde axonal transport?
shuttles molec away from the axon to cell body, the awy that some virus hide from the immune system (hide in neuron bodies)
ex: polio, herpes, tetanus, rabies
Multiple Sclerosis short descriptopn
autoimmune disease in young adults, destroys myelin sheath. loss of muscle control, visual problems, etc
tumors in the CNS are typically in
glial cells (as neurons don’t doo mitosis after certain age)
grey matter vs white matter in terms of components
grey: neuronal cell bodies, mainly in CNS, dendrites, unmyelinated axons, glial cells
white: glial cells with myelinated axons, signals from cerebrum to lower brain centers, fast
structures that protect the CNS (3)
- meninges: cover and protect agains infection- dura, arachnoid, pia
- blood-brain barrier: barrier between circulatory system and the brain, very selective
- CSF: jelly-like, cushion and nourishes
What is meningitis and what is it called if caused by bacteria or virus?
inflammation of meninges,
called encephalitis if caused by bacteria virus
what makes up the blood-brain barrier BBB?
- Endothelium of capillaries- very selective- doesn’t let many things through
- thick basal lamina of the capillairies
- astrocytes - form protective barrier with their shape
when in development does the neural tube form?
by 4th week. neural plate pinches and forms into a groove until eventually a tube
tube potions
anterior: brain
posterior: spinal cord
list the three germ layers of embryo anatomy (out>in)
ectoderm
mesoderm
endoderm
Adult vesicles include the (4)
Telencephalon Diencephalon Mesencephalon (midbrain) Metencephalon Myelencephalon Spinal cord
4 adult brain regions
- cerebrum: sensory input, analysis and command
- diencephalon: sensory from lower regions
- midbrain + brainstem: control habitual, timed events, alert and consciousness
- cerebellum: coordinate muscle activities
brain VENTRICLES (list)
lateral ventricles foramen monro 3rd ventricle aqueduct of sylius 4th ventrical spinal cord
Lateral ventricles also connect to the ____ ____, between brain and connective tissue (produces and fills CSF
subarachnoid space
tract vs nuclei vs commisure
tract: similar to nerve, bundle of cells
nuclei: ganglion, collection of cell bodies
commisure: chunk of white matter, info bridge
frontal lobe fn
control motor output, perceive, communicate and understand
posterior lobes fn (occipital, parietal temporal)
sensory inputs and other associtns
primary motor cortex is the
precentral gyrus
motor speech cortes is the
brocas area on left cerebral hemisphere (speech production)
premotor cotex is the
right in front of primary motor cortex (right infront of precent gyrus)
primary somatosensory cortex is the
postcentral gyrus
censations from cutanous and muscular receptors (large areas are lips and hands homunculus man)
primary visual cortex is the
occipital lobe
does vision
primary auditory cortex is the
temporal lobe
sound
primary olfactory cortex is the
temporal lobe
smell
primary gustatory cortex
parietal lobe (close to temporal) taste
Prefrontal cortex fn
personality, decision making, social behavior, abstract though, learning
(anterior part of frontal lobe)
Wernickes area fn
complex speech and language (in frontal lobe)
sensory association areas fn
perpections, knows whether sound is noise, music or other, associates words with what they are
Gnostic area fn
forms thought (in parietal lobe)
what is agnostia
clinical inability to process sensory information, cant recog person, sound shapes etc
what is aphasia
damage to brain in brocas or wernickes, communication problems
corpus callosum fn
communication between hemispheres
basal ganglia (cerebral nuclei) fn
control subconcious movement of skeletal muscle, ie moving hands while speaking
amygdala fn
memory and emotional reactions (part of lymbic system) in temporal lobes
short description of Parkinsons
reduced dopamine secretion, basal ganglia in cerebellum most affected, leading to tremors, rigidity slow and instablity
Pallidotomy: destroy the globus pallidus (a basal nucleus)
short description of epilepsy
cerebral cortical nerurons misfire= seizures, prevent brain form interpreting and processing incoming sensory signals and from controlling muscles- instablity
epithalamus fn
connect to emotioanl brain, secrete melatonin: sleep/wake cycle
pinneal gland
thalamus fn
mediates sensory and motor input, communicates with amygdala
hypothalamus fn
makes hormones for homeostasis, visual relay (optic chiasm), olfactory relay (mammillary body)
Midbrain fn
sirual and auditory reflexes
corpora quadrigemina
pons fn
relay for higher brain centers and spinal cord
medulla oblongata fn
- cardiovascular center: heart rate
- respiratory center: rate and depth of breath
- other centers: coughing, sneezing, swallowing
Cerebellum major fn
responsible for timing and coordination of body’s response of sensory input
Limbic system where and what does it do
emotional (affective) brain
parts of cerebral hemispheres + diencephalon
fn: how we feel about things (anger, pleasure, sorrow, etc. ) some memory esp associated with emotional response which is why high emotional states cause physical problems
Hippocampus fn
convert short term to long term memory, spatial navifation
short description of Alzheimer’s
60-70% of demential cases (3million cases per year)
chronic neurodegenerative disease, slow then progressing
Reticular formation what and where
filters sensory input, has fibers that arouse brain as a whole
this is why we can filter out most things (ie noise, unconsiously records)
LSD takes away this “filter” why people have hallucinations , they are simply seeing ALL sensory inputs
concussion vs contusion
concussion: shaking,
contusion: bruising, more pronounced damage
Short description of
- Stroke
- cerebral palsy
Stroke: CVA blocked blood flow, leads to tissue damage death (irreversible as neurons cant do mitosis)
cerebral palsy: neuromuscular disability (motor impariment), paralysis as result of brain damage caues infections, teratogens
CVA kinds ischemic vs hemorrhagic
ischemic: narrow of vesicles, blood clot
hemorrhagic: ruptured vessels, bleeding into brain
What portion of the spinal cord does Polio affect?
destroys the anterior horn motor neurons
can lead to paralysis
what integration occurs in the spinal cord?
reflexes
ascending vs descending tracts of the spinal cord
ascending: sensory input
descending: motor output
Ascending spinal tracts (3)
- lateral and anterior spinothalamic: pain, pressure temp
- anterior and posterior spinocerebellar: bodyparts location, movent coordination
- dorsal column: sensory kinesthetic ie fine touch, two point discrimmincation
Descending spinal tracts (2)
- corticospinal (pyramidal) voluntary movement, primary somatic control
- extrapyramidal: many fn
flaccid paralysis is
damate to ventral root on spinal cord
loss of neural input to muscles (control and tone lost)
includes para and quadriplegia
spastic quadriplegia
associated with severe cerebral palsy
spasticity (continuous contraction)
ALS (amyotrophyc lateral sclerosis) is
progressive destruction of anterior horn and pyramidal tracts
loss of speech, swallowing, breathing
genetic base
Spina bifida
incomplete formation of spinal arches, bulging of meninges
linked to maternal intake of folic acid
sensory receptors:
transduction
sensation
perception
transduction: stimulus generating AP
sensation: is the awaress of stimuli (ie touch)
perception: CNS’s interpretation of meaning of stimulus (ie pain)
Receptor locations:
- exteroceptors
- interoceptors
- propioceptors
- exteroceptors: stimuli near body surface, touch, pain, pressure, temp
- interoceptors: w/in body, monitor internal envrmt blood vessels, pH, glucose levels, etc
- proprioceptors: monitor position of body parts, skeletal muscle, ligaments
Stimulus types: mechanoreceptors thermoreceptors photoreceptors chemoreceptors nociceptors
- mechanoreceptors: touch, pressure ie hair cells
- thermoreceptors: change in temp
- photoreceptors: impulse generated by light energy stimuli
- chemoreceptors: change in chemical concentration (taste, smell)
- nociceptors: by stimuli that can potentially cause harm (Pain)
too much of any=pain
Prostaglandins are
inflammation hormones
why do people having a heart attach feel pain in left arm?
bc fibers share track in left arm, referred pain, misinterpreted as coming from the arm
light touch receptors in deep layer of the epidermis called
Merkel’s disks (free simple receptor)
receptors that detect hair bending
Root hair plexus (intertwined in hair follicles)
Tonic receptors vs phasic receptors
tonic: slow adaptors, Pain receptors (joint capsule, muscles)
phasic: fast acting, look for rapid change in stimulus
Meissner’s corpuscle is
tactile disks, rapid (epidermis) mechanoreceptor
Light touch
Ruffini corpuscle is
mechanoreceprtor (in cutaneous tissue)
deep pressure
Pancinian corpuscle is
mechanoreceptor (dermis, deeper)
vibration and pressure
simple receptor are
modified dendritic endings
free: unencapsulated (merkel’s disks)
complex: encapsulated (ruffini and pancinian)
CNS gives us a thought based on 4 things:
- modality: type of stimulus
- location
- duration
4 intensity
which type of receptors do not adapt?
propioreceptors. you always know where your body parts are
nerve bodies forming the DRG are
afferent neurons
I. olfactory tract fn
smell
II. optic nerve fn
vision
III. oculomotor nerve fn
eyelid and eyeball movement
IV. trochelar nerve fn
eyeball movement
V. trigeminal nerve fn
face + mouth senses pain and touch
chewing
VI. abducens
lateral movement
VII. facial
facial expressions and taste
VIII. vestibulocochlear
hearing, equilibrium sensation
IX. glossoppharyngeal
sense blood pressure, taste
X. vagus
slows heart rate, peristalsis, respiratory rate
XI. accessory
swallowing
XII. hypoglossal
tongue movements
how many nerves in each? (31 total) cervical thoracic lumbar sacral coccygeal
- cervical: 8
- thoracic: 12
- lumbar: 5
- sacral: 5
- coccygeal: 1
Cervical plexus nerves
Phrenic: control breading innervates diaphragm
brachial plexus nerves (5)
- axillary: innervate deltoid, shoulder sensation and adduction
- musculocutaneous: innervate at biceps, forearm sensation, flex and supinate elbow
- Median: move thumb, flex everything below elbow
- radial: extend joints below shoulder, supination
- unlar: flex everything below elbow
lumbar plexus nerves (2)
- femoral: flex hip extend knee
- obturator: thigh sensation, through os coxae
sacral plexus nerves (4)
- sciatic: flex knee, plantar flexion
- common peroneal
- saphenous
- tibial
two common causes of sciatica
spinal stenosis: narrowing of space between spine
piriformis syndrome: from compression on sciatic nerve around piriformis muscle
what are dermatomes?
the areas of skin innervated by cutaneous branches of individual spinal nerves.
all spinal nerves except C1 have dermatomes.
Define a reflex
rapid, predictable motor response to stimulus (involuntary) can be learned
monosynaptic vs polysynaptic reflex
mono: direct synapse afferent and efferent
poly: cascade, involving interneurons
contralateral vs ipsilateral reflex
contra: reflex occurs opposite side of the stimulus
ipsi: reflex on the same side as stimulus
Somatic reflexes 7 (the list we learned for lab)
spinal: patellar, biceps, triceps, achilles, plantar (babinski sign)
cranial: corneal, gag
pupillary (autonomic)
what maintains muscle tone, to prevent overstretching?
propioreceptors (also in tendons and ligaments)
to know where your limbs are at all times
stretch reflex is
a muscle contraction in response to a muscle stretching (monosynaptic)
an example of a deep tendon reflex is
the knee jerk
golgi tendon reflex is
protecting a tendon from tearing, opposite stretch reflex, muscle relaxes in response to stretching
flexor reflec is
withdrawal reflex, the most common used to protect the body from damage (hot stove hand withdrawal)
polysynaptic, ipsilateral
cross extensor reflexes are
where the motor neurons are activated along with flexor reflex to stabilize the body after a stimulus. ie step on a nail, your hand goes out to grasp to a wall, you step back with the other foot.
neuralgia vs neuritis
neueralgia: sharp, spasm-like pain on nerve(s)
neuritis: inflamm of nerve
these viruses infect the dorsal root of spinal nerves
shingles, herpes, chicken pox
Motor neurons use which NT?
only ACh
Cholinergic receptors:
nicotinic
muscarinic
adrenergic
- nicotinic: nicotine binds
- muscarinic: Ach binding, exitatory in most cases (inhib to cardiac muscle)
- adrenergic: bind norepineph or eponephrine (alpa and beta) inhib and exitat
contains about 90% preganglionic parasympathetic fibers, affect almost all visceral organs in thorax and abdominal cavities
the vagus nerve
hypertension is often caused by an oversitmulation the ___ nervous sytem
sympathetic
