Unit 2: CNS Sensory Flashcards
what does structure determine
function
what symmetry do humans have
bilateral
organization of the nervous system
anterior or rostral
front part of a structure
posterior or caudal
back part of a structure
dorsal
pointing out of the back
ventral
pointing towards the ground
lateral
towards the side
medial
towards the middle
ipsilateral
same side of the body
contralateral
opposite side of the body
horizontal
a slice parallel to the ground
coronal (transverse)
a slice vertical from front to back
sagittal
- a slice perpendicular to the ground
- parallel to the neuraxis
hindbrain parts
- myelencephalon
- metencephalon
myelencephalon
- contains medulla oblongata
- contains nuclei that control vital functions (breathing and skeletal muscle tone)
metencephalon
- the cerebellum: receives information from sensory systems, muscles, and vestibular system; produce smooth movement
- pons: a large bulge on the brain stem involved in sleep and arousal
mesencephalon
- one of the 3 divisions of the brainstem
- basic physiological function (breathing, swallowing, heart beat)
- gates sensory and motor information
red nucleus
coordinates sensorimotor information
substantia nigra
cells make dopamine and project to basal ganglia
periaqueductal grey matter
involved in pain suppression due to high concentration of endorphins
forebrain parts
- diencephalon
- telencephalon (cerebrum)
diencephalon
- thalamus: interconnected nuclei receive information from the sensory systems (except olfactory) and relay information to sensory processing area in the cortex; learning and memory; slow sleep waves generated
- hypothalamus: 22 nuclei and pituitary gland, control the ANS and endocrine system; key aspects of behavior (feeding, sex, sleep, temp. regulation, emotional behavior)
telencephalon
- hemispheres separated by the longitudinal fissure
- hemispheres connected by the corpus callosum
- grey matter and white matter
how much of the cerebrum is hidden in the gyri and sulci
2/3
spinal cord function
- neuronal link between PNS and brain
- spinal reflex integration center
how many pairs of spinal nerves are there
31
dorsal root meaning
afferent sensory
ventral root mening
efferent motor
phrenology definition
- skull mimicks personality
- larger brain area (ex. forehead) indicates a greater tendency toward the faculty of that area
- not valid as a scientific theory
- first time a specific function was associated with a specific brain region
electrical stimulation
- Luigi Rolando (1809)
- provided proof that the CNS was electrically excitable and that brain functions are anatomically localized
case of Phineas Gage
- spike went through his skull
- profound personality changes after the accident
- personality improvement in Chile (using social and complex cognitive-motor skills)
case of Patient Tan
- diagnosed with epilepsy early in childhood
- admitted to hospital at 21, could only say “tan” twice in a row
- broca coined this disorder aphasia
- good comprehension
- broca reported softening in what would become known as broca’s area in a brain examination postmortem
who coined the term aphasia
paul broca
aphasi
absence of overt speech
paul broca patients
- patient tan
- patient lelong
case of patient lelong
- reduced productive speech at 84 after a stroke
- could only say 5 words (oui, non, tois, toujours, and lelo)
- lelong had a lesion in the same region as patient tan
broca’s area
the frontal lobe of the dominant sphere (left for most of righthanded people and half of left handed people)
who first described receptive aphasia
carl wernicke
receptive aphasia
- impaired comprehension of their own speech
- don’t realize their errors
- associated with stroke, trauma, tumor, infections, and degenerative brain disorders
wernicke’s area
a region of superior temporal gyrus in the dominant cerebral hemisphere
types of aphasia
- broca’s aphasia
- wernicke’s aphasia
- conduction aphasia
broca’s aphasia
difficulty in production of language
receptive aphasia
difficulty in comprehension of language
conduction aphasia
- due to damage of arcuate fasciculus
- patients are aware of their mistakes and try to fix them
arcuate fasciculus
the bundle of axons that connect broca’s area to wernicke’s area
case of patient h.m.
- hit his head while biking
- intractable epilepsy after the accident (blocking out often, convulsions, could no longer work)
- dr. scoville removed two finger-shaped slivers of tissue from his brain (anterior 2/3 of hippocampi, parahippocampal cortices, entorhinal cortices, piriform cortices, and amygdala)
- seizers stopped but developed severe anterograde amnesia (short term memory intact, no new long-term memories) and retrograde amnesia (could not remember events from 3-4 days before surgery and some events up to 11 years before)
- ability to form long-term procedural memories was intact (could learn new motor skills but not remember learning them)
unit of structure of the CNS
neurons
neuron - cell membrane
neuron - dendrites
neuron - cell body (soma)
neuron - axon
neuron - axon hillock
neuron - myelin sheath
neuron - node of ranvier
neuron - synaptic end bulbs
neuron - axon terminal
pre- and postsynaptic neurons - presynaptic neuron
pre- and postsynaptic neurons - neurotransmitters
pre- and postsynaptic neurons - receptors
pre- and postsynaptic neurons - postsynaptic neuron
pre- and postsynaptic neurons - synaptic cleft
pre- and postsynaptic neurons - synaptic vesicles
pre- and postsynaptic neurons - axon terminal
action potential
electrical signals sent over a long distance
a plasma membrane is a ________________ ______________ that is composed of:
- phospholipid bilayer
- phospholipids
- glycolipids
- cholesterol
- membrane protein
plasma membrane - extracellular matrix fibers
plasma membrane - glycoproteins
plasma membrane - carbohydrates
plasma membrane - glycolipid
plasma membrane - cytoplasm
plasma membrane - proteins
plasma membrane - cholesterol
plasma membrane - phospholipid
plasma membrane - cytoskeleton microfilaments
plasma membrane - intercellular space
phospholipid - hydrophobic tail
phospholipid - hydrophilic head
is the plasma membrane highly permeable?
no, it is selectively permeable
what do plasma membranes allow directly through
- gas (COs, O2, N2, etc.)
- small uncharged polar molecules (ethanol, etc.)
what do plasma membranes sometimes allow directly through
water (only in specific conditions)
what plasma membranes never allow directly through
- ions (K+, Ca2+, etc.)
- charged polar molecules (amino acids, ATP, etc.)
how do ions and charged polar molecules go across a plasma membrane
- simple diffusion
- facilitated diffusion (protein-mediated)
- active transport
which channel/carrier proteins are passive and which require energy
passive:
- facilitated diffusion
energy:
- active transport
passive transport
down concentration gradient
why does active transport require energy
it goes against the concentration gradient
electrochemical gradient
combination of concentration and charge differences across the membrane
facilitated diffusion
passive, down gradient using a protein channel or carrier
channel proteins
selective pore
carrier proteins
bind solutes tightly, undergo conformational changes
which transport maintains chemical imbalance necessary for life
active transport
charge (Q)
net imbalance in the number of positively and negatively charged particles
current (I)
- flow of electrically charged particles
- charged particles = ions
voltage (V)
- difference in charge between inside and outside of the cell
- represents an electrical potential energy gradient down which particles want to move
electrical gradient
- influenced by the overall electrical charge
- positive ions would flow toward negative charge
chemical gradient
- influenced by the individual concentration of a particular ion
- all ions move from high to low concentration
the direction that an ion moves depends on:
- overall net effect of electrical and chemical (electrochemical) gradients
- membrane permeability to ions (no channels = no movement)
how is the electrochemical gradient maintained
Na+-K+ pump
Na+-K+ pump
- maintains Na+ and K+ gradients across the plasma membrane
- abundant
- P-type transport ATPase
- phosphorylation changes the conformation of the pump, exposing binding side on the extracellular membrane
- ionic imbalance
ionic imbalance importance
- intracellular pH control
- osmotic control
- transport
- excitability
how much of a cell’s energy foes to powering the Na+-K+ pump
1/3
Na+-K+ pump step 1
binding cytoplasmic Na+ stimulates ATP
Na+-K+ pump step 2
phosphorylation causes conformational change
Na+-K+ pump step 3
Na+ is liberated outside and K+ binding sites are exposed inside
Na+-K+ pump step 4
binding K+ triggers the release of the phosphate
Na+-K+ pump step 5
release of phosphate restores original conformation
Na+-K+ pump step 6
K+ is released and Na+ binding sites are exposed in the cytoplasm
equilibrium potential
the electrical potential difference that exactly counterbalances diffusion due to the concentration difference
nernst equation
- electrical potential required to oppose the movement of an ion across a permeable membrane
- provides a measure of the chemical driving potential established by the concentration gradient for ion
gating definition
transition between conducting and non-conducting (open and closed) states of an ion channel
goldman equation
- defines membrane potential
- accounts for relative permeability of the ions
which axon was used to determine resting membrane potentials
squid giant axon
absolute refractory period
- a period of complete resistance to stimulation
- Na+ channel inactivation means after an action potential there is a brief period when no other action potentials can be generated
relative refractory period
- a period of partial resistance to stimulation
- lasts as long as K channels are open
- strong stimulus can trigger a new action potential
contiguous conduction
conduction of action potentials in unmyelinated axons
conduction speed definition
nerve impulse speed
conduction speed number
nerve impulse travels 1 meter in 0.1 seconds
c fibers job
carry sensory information
are c fibers myelinated
no
c fiber damage causes what
neuropathic pain
axon potential propagation speed depends on ….
how local currents spread
how local currents spread in axon potential propagation speed depends on
- internal resistance of the axon
- resistance of the axonal membrane
do narrow axons have high or low internal resistance
high
to get a faster axon potential propagation speed the axon could be ….
- wider
- myelinated to increase membrane resistance
myelin
a membrane component from glial cells that surrounds and insulates consecutive axon segments
saltatory conduction
the way an electrical impulse skips from node to node down the full length of an axon, speeding the arrival of the impulse at the nerve terminal
myelinated fibers in the PNS
schwann cells
myelinated fibers in the CNS
oligodendrocytes
consequence of demyelination
multiple sclerosis (MS)
multiple sclerosis
- autoimmune disease
- myelin sheath degenerates and forms hardened scars
- affected axons degenerate
- slowing and block of AP conduction
multiple sclerosis risk factors
- age (20-40 years old)
- sex (women)
- family history
- certain infections (Epstein-Barr infection aka mono)
- race (white)
- temperate climate
- vitamin d deficiency
- other autoimmune diseases (thyroid disease, psoriasis, type 1 disease)
- smoking
peripheral nervous system function
- sensory systems: detect external and internal stimuli
- higher brain regions: process and integrate different information and make decisions
- motor systems: execute decisions
pns
fibers (other than brain and spinal cord) that carry information between CNS and other body parts
PNS divisions
- afferent division
- efferent division
PNS types of afferent divisions
- visceral afferent
- sensory afferent
PNS afferent division
send information from internal and external environment to CNS
PNS visceral afferent
incoming information from internal viscera
PNS sensory afferent
- somatic: sensation from body surface and proprioception
- special senses: vision, hearing, smell, taste
PNS efferent division
send information from the CNS to muscles and glands
perception
conscious interpretation of external world derived from sensory input
does pure sensory input give true reality perception
no
why does pure sensory input not give true reality perception
- human receptors only detect a limited number of stimuli
- limited resolution (information channels are not high-fidelity records)
- information can be enhanced/suppressed when it reaches our brain
- brain interprets and distors information to extract conclusions
- interpretation affected by cultural, social, and personal experiences
stimulus
a change detectable by the body
different modalities of stimuli
heat, light, sound, etc.
stimulus receptors
structures at peripheral endings of afferent neurons
receptors function
convert stimuli into electrical signals
stimulus sequence
sensory system parts
sensory receptors, their axonal pathways, and perception target areas in the brain
modalities
different classes
specialized sensory receptors detect ….
different stimuli classes
exteroceptors
specialized neurons on the outside of the body
interoceptors
specialized neurons on the inside of the body
exteroceptors/interoceptors function
transduction
transduction
the process of converting energy from a stimulus into electrical signals via receptor/generator potential which triggers an action potential if thresholds are reached
photoreceptors sense and stimulus
- vision
- light
mechanoreceptors sense and stimulus
- touch, balance, proprioception, hearing
- mechanical energy (stretching muscle, hair cell movement)
thermoreceptors sense and stimulus
- temperature
- heat and cold
chemoreceptors sense and stimulus
- smell, taste
- specific chemicals (O2, etc.)
nociceptors sense and stimulus
- pain
- excessive pressure, temperature, specific chemicals
where do primary afferent axons enter
the spinal cord through the dorsal roots
where do primary afferent axon somas remain
spinal cord dorsal root ganglia
nerve fiber types
- Aα
- Aβ
- Aδ
- C
efferent motor nerve fibers
- Aγ
- B
which nerve fiber do skin receptors lack
Aα
are C fibers myelinated or unmyelinated
unmyelinated
nerve fiber axon diameter
bigger diameter = lower resistance
unmyelinated voltage regulated channels function
- account for ion leakage across the membrane
- conduct impulses slowly
where is there ion leakage in myelinated axons
Nodes of Ranvier
where is graded potential generated
in a receptor cell or free nerve ending
graded potential is proportional to …
stimulus strength
action potential is ….
all or nothing
receptor cell