#1Lecture Exam Flashcards
“Competition” between different sensory stimuli received by PNS neurons
Leads to different processing and “selection” in CNS by interneurons in brain and spinal card
- cause dif. Motor responses be generated for dif. Needs and contexts
CNS
Interneurons that integrate and process signals, and then select an appropriate response
- brain and spinal cord
PNS
Carries info. From sensory neurons towards the CNS for processing and relays processed signal from CNS to motor neurons to appropriate response can be executed
- nerves and ganglia
Efferent neurons
Transmit motor responses away from CNS
- signals sent to targets ( muscle, glands, organs) that will produce action for response
Afferent neurons
Transmit sensory signals toward CNS
- sensory receptors generate graded potential> action potential in response to external/ internal stimuli
Motor division is divided into 2 efferent systems
① somatic system,② autonomic system
- further divided into: parasympathetic/ sympathetic
① sensory input
Sensory neurons will detect stimuli ( external and internal) and transmit signal towards CNS
② integration
Signal relayed to interneurons n brain or spinal cord for analysis and/ or processing, so an appropriate response can be “selected”
③ motor response
. Processed signal is then relayed to motor neurons to trigger needed response in muscles, glands, organs
Ganglia ( PNS )
Group of cell bodies
Nerves (PNS)
Bundles of neuron fibers
- dendrite or axons
Nerves
Groups of neurons w/ similar functions w/ axons bundled together
What can nerves have?
Both sensory/ motor neuron axons moving opposite directions in fiber
Where do dendrites receive info?
Dendrites of sensory neurons receive info at distal ands of cranial nerves
Sensory neurons (PNS)
Detect/ receive dif. Stimuli
Somatic afferents
Typically deal w/ external stimuli
-Deal w / stimuli that we are aware/ conscious
- voluntary responses
Visceral afferents
Deal w/ internal stimuli
- stimuli that we are unaware/not conscious
- involuntary
Where do voluntary responses occur?
Brain
Where do involuntary reflexes occur?
Brain + spinal cord
Nuclei (CNS)
Group of cell bodies
-Where processing occurs
Tracts (CNS)
Bundles of neuron fibers
- dendrite or axons
Where do axons of motor neurons trigger responses?
Synapses w/ targets
Somatic nervous system
Carries signals from CNS and relays info.to skeletal muscles, perform voluntary control
Autonomic system is divided into:
Parasympathetic and sympathetic
Sensory efferent receives stimuli from:
Both inside and outs, de body
Inside-to - outside order of nerve
Axon, myelin, epineurium, perineurium, endoneuriam
Endoneurium
Delicate cover of single axon
Perineurium
Coarser wrap of many axons into fascicle
Epineurium
Thick/rough wrap of entire nerve, blood vessel
Nervous system development
Everything starts out as neural tube
- forms along the length of entire embryo
Where do precursor cells originate?
During neural tube formation
What do neurons start as during nerve development?
Start as cell bodies and grow their axons projections to targets
Border between neural tube
Neural crest
- cells that delaminate(separate) and migrate to different parts of body
Precursors for efferent sensory neurons
Neural crest cells
- send axons back to CNS
CNS neurons cannot undergo…
Regeneration and repair
What proteins. do oligodendrogtes have?
Growth inhibitor proteins on membranes
What do astrocytes form?
Scar tissue can block axon regeneration
PNS con undergo…
Regeneration repair
- Schwann cells help
If neurophysiology is the same, then what makes sensory receptor neurons different?
① dif. Stimulus
② dif. Dendrite and neuron morphologies
dif. Types sensory neurons have…
Dif stimulus - gated con channels
- graded potential process is dif for dif sensory neurons
3 ways to classify sensory receptors
① location (gross anatomy)
② structural complexity (cell anatomy)
③ stimulus type “physiology”
Simple, non-encapsulated nerve endings
- modified and exposed dendrites
- general senses
Simple, encapsulated nerve endings
- dendrites enclosed in CT
- general senses
Complex, specialized nerve endings
Mouthed structure and support cells
- special senses
Exteroreceptors
Outside stimuli
- detect chemicals in special organs
Interoreceptors
Internal stimuli
Chemoreceptors (exteroreceptors)
Respond to stimuli when specific chemical binds to gated-channels, opening and depolarize membranes
- dissolved in solutions
- special senses
General senses detect…
Change in internal environment
Exteroreceptors detect?
Acidity in mucosa, like nasal cavity
Interoreceptors detect?
Blood acidity, blood glucose, ion balance
Mechanoreceptors
Stimuli of mechanical force, (vibration) “
- nerve endings w/ hairs in tubes w/fluid
- vibration move through fluid-hairs trigger depolarization
Proprioceptors
Sensitive to stimuli inside body,
- mechanical sensing (stretching)
- general senses
Thermoreceptars
Stimuli of temp. Change
- heat cause shape conformation n gated channels, depolarizing membrane
- general senses
- include exterbreceptors and interoreceptors
Nociceptors
Stimuli that is potential damage, painful response
- thermos. Mechano, chemo
Photoreceptors
Stimuli of light photons, cause reactions of proteins of retina of eye
- opsins change their conformational shape
- open “stimulus” gated ion channels, cause neuron depolarization
- special sense
-Extercoreceptons
_ Of the bodys sensory receptors are in the eye
70%
_ Cranial nerves deal w/ the eye
4
Photoreceptors
Respond to stimuli of light photons, cause reactions in proteins of retina
- light impact proteins called opsins, change conformational shape
- open stimulus gated channels, causing neuron depolarization
Lens
Adjustable focusing apparatus needed for vision, get light to retina
Retina
Inner layer of eyeball, house photoreceptors
2 layers of Reina
① outer pigmented layer
② inner neural layer
Inner neural layer of retina
House light receiving photoreceptors
- extend to margin of ciliary body
- stops short at ora errata
Cross section of inner neural layer
Photoreceptors at bottom
- light travel through layers to reach dendrites of photoreceptors
- ganglion, axons, are transparent to let light through
Rods (sensory cells )
Numerous, very sensitive
- detect dim light
- one type of visual pigment
- shades of grey
- peripheral vision receptors
Cones( sensory cells )
Bright light
- 3 pigments: red, blue, green
- non -converging pathways w/ detail
- high resolution color vision
Outer segment
Light receiving region, which has visual pigment embedded in discs, which will then change shape when they absorb light
Inner segment
. Connects to the cell body
Axon which link via acetic terminal next to cell in sensory relay
Rods and cones have
Cell body synaptic terminal, outer segment and inner segment
Generate their own other segment every 24 hours due to intense light exposure A.
Visual pigments
. Absorb light.
Op sin protein+ retinal = visual pigments
What is retinal synthesized from?
Vitamin A
Ops in proteins
vary. depending on cell
-rhodspin found In rods (dim blue/green)
Cone opsin only cones (red, blue,green)
Photo transduction
Opsin protein absorbs certain wavelength of light, then transfers absorbed energy to retinal
Polarization of retinal
Renal changes shape triggering sensory signal relay to brain
What makes photoreceptors work?
Rhodopsin protein+retinal molecules
What does phototransduction depend on?
Depend on retinal changing shape
Light detection(phototransduction) uses these steps in photo receptors
① pigment synthesis
② pigment bleaching
③ pigment regeneration
① pigment synthesis (prototransducion)
Il-cis-retinal is made from vitamin A and bonds rhodopsin, series of synthetic steps
- rhodopsin + “bent” 11-cis- retinal accumulate high levels in dark
② pigment bleaching (phototransduchos)
Light absorption by the rhodopsin causes ll-cis-retinal to convert into straight all trans retinal
- cause transcducin protein to start a neural circuit that makes electrical signal
③ pigment regeneration (phototransduction)
Enzymes will slowly convert straight all-trans- retinal back into the bent il-cis-retinal
-If levels aren’t too ↑ regeneration keep up w/ bleaching
So how does transducing lead to electrical signal?
In a literal signal relay starting inside the cell
What does transducer cause?
Transducing induced signal cascade causes a stimulus iron channels to close
-change his memory potential polarizes a photo receptor which alters neurotransmitter release at neural synapse
What does neural circuit send to brain? (Phototransduction)
Visual information
Three types of neurons in neural circuit
Photo receptors, bipolar cells gangling on cells
When is neural circuit activated?(phototransducton)
Once photoreceptors absorb light
Where does color blindness occur?
Occurs in photo receptors, not brains perception
Color blindness
One or more of the cone opsins is absent
-inherited as an X linked condition
-Red cone green cone absence is the most common
Where is sensory information relayed?
Relay along optic nerves to visual processing/integration centers in brain
How does light travel?
Normally travels in straight lies, but this does not create a focused image
Refraction
Light changes speed/direction when it passes through transparent media
Lenses
Transparent interfaces that have different medium, which subsequently can alter the path of light is moving
-convex lenses allow for light to be focused on a point
Steps of light passing through
Go through cornea, aqueous humor, lens, and vitreous humor
Where does life bend on path to retina?
Bends three times
① enterin cornea
② entering lens
③ leaving lens
What can cornea not adjust to?
Although the cornea has most of the refractory power, it is fixed and thus cannot adjust to changes in distances
Is lens flexible?
It is flexible it can be adjusted to change Near or far objects:
Purpose of lens
Change shape to focus light on retina
- transparent-lacks vascularization
- flexible - change shape
Convex on both sides… Focus light
Lens epithelium
Interior region of cuboidal cells that differentiate into lens fiber cells
Lens fibers
Form bulk of lands in are filled with transparent protein crystalline
-continuously added so lens becomes dense convex firm with age
still flexible
Vascular layer/ choroid
Has thicker region called ciliary body
Ciliary body
Circles of the lens
Has smooth muscle
Has ciliary muscles that contract/relax
Ciliary muscles
Tip with extensions called ciliary processes, which in return connect to ciliary zones
Ciliary zones
Ligaments
Connect lens to ciliary muscles
What happens when ciliary muscles contract/relax
Zones tighten, adjusting lens shape
Adjusting lens curvature w/ ciliary muscles + ciliary zones allows?
Allow for light to remain focused on the retina, even as we change viewing distance
Distant vision
- Ciliary muscles are relaxed
- ciliary zones tighten
- flatten lens to point where focuses easily
Far point in vision =
Distance beyond which no change in lens shape is needed to focus
Close vision
Eye need active adjustments
- ciliary muscles contracted
- ciliary zones loosen
- bulge lens n more spherical shape to allow focus
What does close vision require?
. Construction of the pupils via Iris.
convergence of eyes via extrinsic muscles
Cataracts clouding of lens
Crystalline proteins, clump in deep fibers often due to oxidative stress, metabolic changes, excessive vitamin C
-Lens can be replaced surgically with artificial lens
Cranial nerve for hearing
Vestibulocochlear nerve
Mechanoreceptors- special senses
Stimuli of mechanical force (vibration)
- complex specialized nerve endings w / hairs in tubed filled
How do mechano receptors and vibration work?
As vibration moves through fluid, the hairs move and trigger depolarization
- vestibule + semicircular canals = equilibrium
- cochlea = hearing
Where are mechanical receptors present?
Inner ear
What is sound?
Pressure disturbance, where a vibrating object pushes on the surrounding media
Ear has both air and liquid regions
What does high low vibrational energy create?
Create high low pressure pushes on the surrounding medium molecules
-Alternating high low pressure makes waves
Points of highest pressure
Compression and represents crest of soundwave
Point of lowest pressure
Rarefaction and represents trough of sound wave
Wavelength
Distance between each crest
Frequency
passed wavelengths/time
correspondence to pitch
Amplitude
Change between high low pressure
Strength of a wave
Corresponds to loudness/volume
Sound waves progress through three areas
① external ear - soundwaves travel through air
② middle ear - vibrations transferred to bone
③ internal ear - vibrations, fluid waves, cochlea
Soundwave move through external ear
① auricle - funnel
② external acoustic meatus
Tympanic membrane
Boundary between external/middle ear convert sound to vibrations
Parts of tympanic membrane
① skin-covered outer surface receives sound waves via external environment
② thin/ translucent CT vibrate in response to sound
③ mucosa inner surface transfers vibration energy to bones of middle ear
Where is vibration transferred in middle ear
Through bones to oval window and into inner ear
Spiral organ
Coil w/ cochlear duct (scala media)
- contain sensory hairs that detect sound-related vibration
- hair cells between tectorial/ basilar membrane
Scale vestibule
Abuts oval window, contains perilymph
scala tympani
Terminates at round window, perilymph
Perilymph chambers
Continuous w/ each other and bony labyrinth and merge in helicotrema, at apex
scala media
House spiral organ; endolymph
- contam basilar membrane
Basilar membrane
soundwaves will vibrate basilar membrane to stimulate sensory receptors in spiral organ
Inner hair cells (spiral organ)
One row
- detect sound vibrations coming through basilar membrane
- sterocilia “tips” are in tectorial membrane and pivot while basilar membrane vibrates, cause depolarization that relays to cochlea nerve
Outer hair cells (spiral organ)
Contract end stretch, change stiffness of basilar membrane
- help fine tune inner hair cells by amplifying motion of basilar membrane
- protect inner hair cells from loud noises by ↓ motion of basilar membrane
Resonance
Movement of different area of basilar membrane in response to particular frequency
How does basilar membrane affect resonance?
Change along length, vibrational shaking at certain wave frequency
Fibers near oval window
Short and stiff and resonate with waves of î frequency
Fibers near cochlear apex
Longer and floppier and resonate w/ waves of ↓ frequency
Sound reception in cochlea
Sound wavelength enters cochlea, travel until reaches section of basilar membrane that match frequency
Basilar membrane sound reception
Shake, spiral organ at location, stimulating subset of sensory hairs
Sound reception summing
- Vibrations on basilar membrane cause stereo cilia hairs to pivot
- pivoting of stereocilia on sensory hair neurons trigger depolarization
- electrical Sigha’s sent down vestibulocachiear nerve to auditory cortex
Motion sickness
Sensory inputs are mismatched, visual input differs from equilibrium input
Throwing the three steps of neuron processing what types of neurons are present
Sensory neurons - a fferent
Inter neurons - CNS processing
Motor neurons - efferent
During the three steps of neuron processing, what stages are PNS structures involved?
Sensory input -afferent
Motor response - efferent
During the three steps of neuronal processing, which stages are CNS structures involved in?
Integration- interneurons in brain and spinal cord
Are sensory neurons afferent or efferent
Afferent
What are motor neurons?
Carry signals from the CNS to muscles, glands or organs
Efferent
What are interneurons and where are they located?
CNS only neurons that process and relay information between sensory and motor neurons
Does a spinal cord have interneurons?
Yes
What is autonomic nervous system?
Division of the nervous system that controls involuntary functions
- Heart rate digestion
During development where do PNS cell bodies arise from before growing axons?
Motor neurons arise from neural tube
Sensory neurons arise from neural crest
What are neural crest cells? What do they do during development?
Precursor cells that migrate and differentiate into sensory neurons and other cell types
What are some cell types of neural crest cells develop into?
Sensory neurons
Schwan sells
Melanocytes
Smooth muscle cells
Typically can CNS neurons regenerate why
No, because oligodendrocates, inhibit growth and astrocytes form scar tissue
Typically can PNS neurons regenerate and why
Yes, because shwan cells actively assist in regeneration
List the classes of stimuli that sensory receptors can detect
Mechanoreceptos
Thermal receptors
Photoreceptors
Chemo receptors
Nociceptors
Where are sensory receptors for general census found
In skin and internal tissues
Where are sensory receptors for special senses found
. Specialized sensory organs like eyes and ears
Our photoreceptors located at the top or bottom of the neural layer in retina
Bottom
what type of sensory neurons detect hearing/equilibrium
Mechanoreceptors
What is the general order of signal relay after light photons to stimulate photo receptors?
Photoreceptor, bipolar cell, ganglion cell( optic nerve)
What is general cellular anatomy of photoreceptors?
Otter segment: contain visual, pigments, in
Is membrane discs
Inner segment: houses, the cell body and synaptic terminals
How do visual pigments absorb light to open ion channels?
The shape of retinal activating Oisin and triggering a cascade that closes Na channels leading to hyperpolarization
11-cis -retinal
Bent form of retinal, present in dark
All-trans- retinal
Straight form of retinal, after light exposure
How does the depolarization of photo receptor affect bipolar cells?
Depolarization stops the release of an inhibitory neurotransmitter, allowing bipolar cells to become excited
How does depolarization of bipolar cells affect ganglion cells?
Bipolar cells, release, excitatory, neurotransmitter, stimulating, ganglion cells to generate action potentials
What does depolarization of ganglion cells lead to?
. Action potential travel through the optic nerve to the brain
What muscles contract to change the shape of the lens
Ciliary muscles
What is myopia?
Nearsightedness (Eye is too long, light focuses in front of retina)
What is hyperopia
Farsightedness ( light is too short light focuses behind retina )
What is astigmatism?
Uneven curvature of the cornea or lens causing blurred vision
