Exam 2: Neurophysiology Part 4 - Hearing and the Visual System Flashcards
What are sound waves
Longitudinal vibrations of gas particles in an external medium (air)
Phases of compression and rarefaction alternate
Intensity, frequency, and wavelength
Intensity - base of wave to top of wave (amplitude)
Frequency - distance from one wave to the next (peak to peak or valley to valley)
Wavelength - length of whole wave; one whole peak and one whole valley; distance between two areas of maximal pressure
Outer ear parts and what is does
Ear pinna and ear canal
Funnels sound to the tympanic membrane
Middle ear parts and what is does
Contains 3 ossicles (bones) - malleus, incus, stapes (AKA hammer, anvil, stirrup)
Air filled cavity connected to nasopharynx by eustachian tube
skeletal muscles in ear
2 small skeletal muscles attached to malleus and stapes
Stapedius muscle and tensor tympani muscle
what do stapedius and tensor tympani muscles do
work together in order to regulate vibration
react when there is sound
can control how much structures in ear move to act as a bit of a buffer
Chambers of the ear and what they contain
Scala vestibule (dorsal) - contains perilymph
Scala tympani (ventral) - contains perilymph
Scala media - contains endolymph
endolymph vs perilymph
endolymph - intercellular fluid; high in potassium
perilymph - extracellular fluid; high in sodium
organ of corti and tectorial membrane and basilar membrane
Organ of corti - functional unit
Tectorial membrane - on top of organ of corti; gelatinous texture; hair cells are sustained here (this lies on top of hair cells)
Basilar membrane - contains hair cells; structure that moves as a wave
hearing sequence of events (4)
- Sound waves are collected by the outer ear and produce vibrations on the tympanic membrane (eardrum)
- Movements of the ossicles in the middle ear
- Vibrations on the oval window are transferred to the basilar membrane (through perilymph and endolymph) causing it to move up and down
- Hair cells cilia shear along the tectorial membrane causing changes in transmitter release
difference between low and high frequency vibrations
Low frequency causes vibrations of almost all cells and travels far in cochlea
High frequency causes vibrations in few cells and does not travel far in cochlea
is glutamate excitatory or inhibitory in regards to hearing
Excitatory
Components of the auditory pathway
Hair cell Spiral ganglion (in periphery) cranial nerve VII Cochlear nuclei (in medulla) trapezoid body Superior olivary complex (in medulla-pons) lateral lemniscus Inferior colliculus (in mesencephalon) brachium of the inferior colliculus Medial geniculate nucleus (in diencephalon) auditory radiations Auditory complex (in telencephalon)
where are receptor cells located in eye
retina
parts of the retina
Temporal - closer to temporal region of brain, lateral
Nasal - closer to nasal area, incudes where optic nerve is, medial
Chambers of the eye
Anterior chamber
Posterior chamber
Vitreous chamber
What is aqueous humor and where is it
Nutrients for cornea and lens
located in anterior and posterior chambers
what is vitreous humor and where is it
composed by gelatinous fluid and phagocytic cells
located in vitreous chamber
Lens ligaments and muscles
Lens is suspended by ligaments (zonular fibers) that are attached to the ciliary body (muscles)
Tears:
What do they do (4)
What immunoglobulin do they contain
Contains Immunoglobulin A (IgA)
Lubricates eye
Prevents frost damage of cornea
Moistens nasal cavity
Helps combat bacteria
tapetum
Reflective patch for nocturnal seeing
how does eye change for near and far vision
Ciliary muscles change tension on suspensor ligaments thereby altering the shape of the lens
Shape of lens in near vs far vision
Near vision - ciliary muscles contract –> decreased tension of suspensory ligaments –> lens round
Far vision - ciliary muscles relaxed –> increased tension of suspensory ligaments –> lens flattened
Cells of the retina and functions (6)
Retinal pigmented cells - nourishment and protection of photoreceptors –> 1st layer
Photoreceptors - rods and cones –> 2nd layer
Horizontal cells - lateral interactions among photoreceptors and bipolar cells
Bipolar cells - connect photoreceptors with ganglion cells –> 3rd layer
Amacrine cells - lateral interactions among bipolar cells and ganglion cells
Ganglion cells - axons from the optic nerve –> 4th layer
Rods characteristics (5)
Most sensitive to light Night vision (low light) Low acuity Achromatic Peripheral retina
Cones characteristics (5)
Less sensitive to light Day vision (normal indoor and daylight) High acuity Color vision Central retina (fovea)
Define acuity
Good at discerning image detail
Parts of the rod/cone
Outer segment - plasma membrane; discs; cytoplasmic space; cilium
Inner segment - mitochondria and nucleus
Synaptic terminal - releases transmitters
What do discs of outer segments contain
Visual photopigment:
Opsin - a GPCR
Retinal - an aldehyde of Vitamin A (retinol)
Depolarization and hyperpolarization in photoreceptors
Depolarize when not stimulated by light
Hyperpolarize when stimulated by light –> cell becomes more negative
Mechanism in darkness (2 steps) and in light (4 steps)
Darkness:
- 11-cis-retinol and opsin bound together
- cGMP produced
Light:
- 11-cis-retinol configuration changed to all-trans which is split away from opsin
- Opsin binds to and activates a G-protein (transducin)
- Transducin activates phosphodiesterase that hydrolyzes cGMP
- Decreased cGMP levels cause a closure of Na+ channels –> hyperpolarization –> less glutamate release (glutamate is the activating transmitter)
types of cones
Cones differentiate colors
Blue cones - sensitive to smaller wavelength light
Green cones - sensitive to medium wavelength light
Red cones - sensitive to larger wavelength light
Differences between species - number of cones/colors they can see
Birds, insects - different types of cones; good color vision
Humans, apes, old world monkeys - 3 cones (blue, green-yellow, orange-red) –> trichromatic vision
Dogs, cats, cattle - 2 cones –> dichromic vision
Dogs see mostly in blue and yellow
carnivore vs herbivore field of vision
Carnivore - eyes are frontal, restricted monocular lateral vision, large central binocular field
Herbivore - eyes lateral, wide monocular lateral vision, narrow central binocular field
Reticulo-geniculo-striate pathway
pathway to cerebral cortex
crosses at optic chiasm
lateral geniculate nucleus is located in thalamus
primary visual cortex is located in occipital lobe
Reticulo-geniculo-striate pathway direction of travel
Right visual field projects to left (nasal) retina and axons travel to the left lateral geniculate nucleus and to the left primary visual cortex
- axons from right vision goes to left side of brain
Left visual field projects to the right (temporal) retina and axons travel to the right lateral geniculate nucleus and to the right primary visual cortex
- axons from left vision goes to right side of brain
Where do axons from nasal and temporal retinas go
Axons from nasal retina of both eyes goes to contralateral part of brain
- left nasal goes to right side of brain and right nasal goes to left side of brain
Axons from temporal retina of both eyes stay on same side of brain
- left temporal goes to left side of brain and right temporal goes to right side of brain
Pupillary light reflex and consensual response - circular vs radial muscle
Circular muscle –> constrictor –> parasympathetic innervation
Radial muscle –> dilation –> sympathetic innervation
Which part of the brain is the olfactory brain
Rhinecephalon
Why is olfaction important
Sense of smell important for seeking food; orientation; marking territory; choosing mate; recognition of danger
Differences in passage of air through nasal cavity: sniffing vs breathing
Sniffing: air passes above heat exchanger reaching olfactory epithelium directly
Dogs sniff quickly to push air to olfactory
Breathing: air passes through the heat exchanger
Olfactory cells discription
Primary receptor cells
Dendrite extending towards surface of epithelium
Mucus layer keeps epithelium moist and clean
Mucus layer contains cilia
Olfactory cell cilia
Embedded in mucus layer of epithelium
Contain odor receptors
Glomerulus of olfactory cell
Group of synapses between olfactory cell terminals and mitral cell terminals
Several unmyelinated axons of olfactory cells synapse with a mitral cell in the glomerulus (olfactory bulb) –> signal amplification
Odor molecules and odorant receptors
Odor molecules dissolved in gas or water (aerosols)
Odorant receptors (OR) are GPCRs
Olfactory cells are extremely sensitive - single odor molecule can open several thousand ion channels
Olfactory pathway to cerebral cortex
Olfactory epithelium
- olfactory nerve
Olfactory bulb
Olfactory cortex anterior olfactory nucleus piriform cortex amygdala entorhinal cortex
Thalamus or Hippocampus
From thalamus to frontal cortex or caudate nucleus
Parts of the olfactory cortex and what they do and where the signal goes after
Anterior olfactory nucleus:
Create and store olfactory gestalts
Goes to thalamus
Piriform cortex:
Behavioral, cognitive, and contextual info
Goes to thalamus
Amygdala:
Emotional processing of olfactory info
Goes to thalamus
Entorhinal cortex:
Working memory
Goes to Hippocampus
Vomeronasal organ location
Paired, cylindrical organ located ventrally and medially in anterior portion of nasal septum
Connected to oral cavity
Vomeronasal organ function
Sexual behavior
Recognition of odor molecules dissolved in fluids such as urine and vaginal secretions
Flehmen response
What is the Flehmen response
“to curl upper lip”
Observed in males (ungulates and felidae)
Direct the fluids in the vomeronasal organ
Species differences in distribution of taste buds
Ruminants
Dogs
Birds
Ruminants - mostly in basis of tongue
Dogs - mostly in tip
Birds - poorly developed
What kind of receptors (primary or secondary) are taste receptor cells
Secondary receptor cells
How flavor particles get to receptors
- Mastication
- Flavor particles suspended in fluid
- Fluid with flavor particles enter into the pores and bind to their receptors
Differences in intensity of recognition of different gustatory stimuli based on location of tongue
Tip - more salty
Sides - more bitter and sour
Back - more bitter and sweet
Different gustatory stimuli (5)
Sweet - glucose, saccharose
Sour - citric acid, H+
Salty - NaCl, Na+
Bitter - caffeine, nicotine
Umami - from Japanese “umai” = delicious and tasty –> tomatoes, meat, cheese, soja sauce, flavor enhancers
Ionotropic gustation receptors
Salty, sour
- Na channels at apical membrane of cell
- When Na or H approaches it goes through Na channel
- Leads to membrane potential
- Depolarization of cell, Ca influx
- Synaptic vesicles fuse with basal membrane then release transmitters
- Activates neuron and info travels to CNS
Metabotropic gustation receptors
Sweet, bitter, Umami
- Glucose, glutamic acid, caffeine etc. bind to GPCR at apical membrane of cell
- Signal goes farther with 2nd messenger DAG and IP3
- Ca release from ER
- Opens channels, like Na channels
- Induces release of atypical transmitter (ATP)
- Info travels to CNS
What activates heat sensitive channels in the oral cavity
Capsaicin - in spicy foods
Capsaicin binds to heat sensitive channels
What is a use of Capsaicin
Medicinal use in cremes for muscle pain and strains
Central pathway for gustation
Afferent fibers in cranial nerves VII (facial) of nucleus of solitary tract that reach the thalamus and project to the cerebral cortex
