Exam 2 Flashcards
Stimulus
A change in the internal or external environment that triggers a respons
Sensation
- a conscious awareness of sensory information and the resulting NS activity
- ex. Ouch! Pain! (after capsacin binds to the tongue)
perception
- awareness of a sensation, a higher level of understanding
- understanding the meaning, location and conswequences of a sensation.
- Stimuli activate receptors, trigger AP, eventually the signal reaches the brain and is perceived.
- ex. pain on tongue, kind of spicy, maybe i should stop eating these jalepenos, or drink some milk (After capsacin binds to tongue
- Ex. I’m cold, should I put on a sweater? Should I go inside? etc
receptors
structures that detect stimuli, on a neuron or associated with a neuron. Receptors are transducers
transducers
change one form of energy (a stimulus) into electrical ATP
reception
- stimulus reaches the receptor
- ex. capsacin binds to the tongue
Sensory transduction
- Receptor is stimulated
- Receptod triggers an AP
- Impulse sent to the brain for interpretation
Types of receptors
- Mechanoreceptors
- Thermoreceptors
- Nociceptors
- Chemoreceptors
- Photoreceptors
- Baroreceptors
mechanoreceptors
include propriorecpetors, detect changes in teh membrane
nociceptors
detect pain (both somatic and visceral
What does magnitude of sensory graded potentials influence?
the frequency of action potentials
How is intesity perceived by the brain?
by how many AP are fired
Adaptation
- a decrease in receptor sensitivity despte constant strength of a stimulus
- ex. sitting on a seat– touch receptors on butt adapt so that you don’t constantly feel it there
- Degrees of adaptation can vary:
- Rapid adaptation: sensory receptors in the skin, on, then off until a change
- Slow adaptation: sensory receptors that need constant monitoring such as muscle tenseness
What info does the brain need to understand what is occuring?
- Stimulus type: heat, cold, sound, pressure, etc
- Stimulus intensity: determined by frequency of AP
- Stimulus location: determined by brain location of the ed of the afferent pathway, aka it is based on what portion of the brain is stimulated
sensory unit
a single sensory neuron with all its receptor endings OR a sensory neuron and its receptor cell
recpetive field
Typically a sesory neuron has many receptor endings, the entire area they encompass is called the receptive field
Small receptive field
precise and very sensitive, ex. the lips
large receptive field
hard to tell exactly where the touch occured, not very sensitive
Acuity
the degree of accurate perception.
ex. discerning touch in one location from another, or discerning two related images
Lateral inhibition
- Ex. if 3 sensory neurons all receive stimuli, the one with the strongest stimulus wins
*
Afferent sensory pathways
- Get the signal to the brain.
- Chains of 3+ neurons
- Sensory neurons–> intereurons–>more interneurons
- Chain is specific
- The location is the brain is also specific
Factors that affect perception
- Adaptation
- Emotion, personality, stress, social background.
- CNS has mechanisms to turn down sensityive reception by the PNS–thalamus can amplify, diminish or edit what you are perceiving
- Lack receptors for some stimuli–radio waves, infrared light
- Have receptors but no mechanism forconscious perception– blood vessel stretch receptors
- Drugs– hallucinations
- Mental illness– schizophrenia can produce untrue perceptions of sensory stimuli
- Damaged neural pathways
Phantom limb
sensation associated with a body part that has been amputated. The intact portion of the sensory pathway continues to send signals to the CNS
Referred pain
pain impulses from viscera are perceived as originating from the skin. This often occurs with heart attack patients. Percieve arm pain, but actually it is something deeper
Reflexes
Neural circuits that operate without conscious control– involuntary. They usually work to maintain homeostasis. You can’t stop it, and can’t always perceive it
Monosynaptic reflexes
- One synapse
- Simple relfex where the afferent neurons synapse onto the effferent axon
- No interneuron
- There is a very minor delay between the stimulus and response
- ex. knee jerk reaction
polysynaptic reflexes
- Many synapses
- involve a large numvber of synapses and interneurons
- there is a longer delay between stimulus and response
- ex. shifting weight to pull legg away from stimulus
Ipsilateral reflexes
same side reflexes
ex. pummling your arm away from a hot object
contralateral reflex
opposite side reflex
ex. stepping on something sharp an pulling one leg away while shifting weight to the other leg
A reflex arc that includes hand and brain will be:
Polysynaptic
Does an area with a large receptor field have a high, or low acuity?
Low touch acuity
Which reflexes are maintained even after spinal cord injury?
Erection, defecation, stretch/tendon reflexes, urination
Somatic senses
pain, temperature, touch, stretch and pressure
all over the body
special senses
gustation (taste), olfaction (smell), vision, equilibrium and hearing
limited to the head
Recepector classification: distribution
- Where in the body
- Somatic: receptors in skeletal muscle or skin
- Visceral- guts
Receptor classifications: where the stimulus comes from
- Extteroreceptors
- Interorecptors
- Proprioreceptors
Exteroreceptors
Detect change from the external environmentm touch thermal
Interoceptors
Detect stimuli in internal organs, like [O2] chemicals from cell damage
proprioceptors
detect changes in limb position, located in muscles, tendons and joints. Where our body is relative to the world.
Proprioceptors
mechanoreceptors that detect the stretch of muscles and ligaments to determine body position
Tactile sensation
touch, heat, cold, pressure, detected though skin. Different types of receptors specialize in types of touch.
Pain reception
somatic and visceral nociceptors respond to tissue damage
Tactile receptors
- perceive touch
- are mechanreceptors that react to touch, pressure and vibration
- Have specialized structure for different functions
- Have Small receptive fields
- Pathways of neurons bring touch sensation to the brain
Temperature
- Is sensed by dendritic endings of unmylenated sensory neurons
- Contain ion channels that open at specific temps
- Some chemical stimulus can override this, like capsacin and menthol. These don’t actually change temperature, but it gives the same sensation
Pain
- Protect us from tissue damage
-
Stimuli- mechanical deformation of tissue, extremes in temp, chemicals
- Acids and bases can directly trigger nociceptors
- Chemicals like histamines, cytokines and prostaglandins are all released when cells are damaged
- Neurons that have ligand dated channels for these stimuli are called nociceptors
Nociceptors
Have ligand gated channels for pain stimuli (chmicals, deformation of tissue, extremes of temp)
Mostly unmylenated
Mostly use substance P or glutamate as NT
can be inhibited by other receptors, lateral inhibition and CNS inhibiiton
photoreceptors
- in the eyes, detect light, color and movement
- Light is filtered, bent and absorbed by other parts of they eye before it reaches the photoreceptors
- Information from the photoreceptors is sent to the visual region of the brain for interpretation.
Sclera
- tough outer portion of the eyeball
- the anterior surface of the sclera is the clear cornea
cornea
the clear anterior surface of the sclera
Choroid
the dark middle portion of the eyeball
anterior choroid is iris, lens and ciliary muscle
most of the blood vessels are found here
retina
reflective inner portion of the eyeball
formed as an extension of the brain
contains photoreceptors clustered in the macula lutea and fovea centralis
macula lutea and fovea centralis
area where photoreceptors are clustered in the retina
the curved surfave of the cornea bends light onto these spots
macula lutea is a larger area, and fovea centralis is a small part within that area
is an area so the photoreceptors are not covered by blood vessels
ciliary muscles
shape the lens to bend light waves
in the choroid- ventral part of eye
accommodation
bend lens to change the path of light.
sight acuity
bending light to focus it on the fovea centralis
presbyopia
lens get tougher- happens when you get old
nearsighted
eyeball is too long (oval) can’t bend light to the right place
far sighted
eyeball is to short- can’t bend light to the righ place
Müller cells
- type of glial cells
- make up 20% of the volume of the retina
- work like fiber-optic cables
- channel light to the location of photoreceptors
Pigment layer behind retina
absorbs any light photons that are not caught by photoreceptors. This works to protect structures and adds to the clarity of vision
helps with acuity, like reading.
Rods
extremely sensitive.
Good for dark, good for perceiving motion
photopigment=Rhodpsin + retinal
Cones
only respond to bright light, responsible for color vision
photopigment=opsins +retinal
pigments
are in photoreceptors, they absorb different wavelengths of light (those that are notabsrobed are reflected)
retinal
derived from vit A
opsins
differ based on different types of cones, each absorb a different spectrum
photoreceptor depolarization
photreceptors are constantly depolarized, and always have their channels open
Stimulation closes these channels and polarizes the cell
What type of receptors are nociceptors
Chemoreceptors
Color vision
Retina has 3 types of cones:
Long wavelengths (red cones)
Medium wavelengths (green cones)
Short wavelengths (blue cones)
there is some overlap
Perception of shade is determined by relative outputs of the 3 types
Color blindness
when one or more cone pigments are not made properly
Red-green colorblindness is most common (1:12 males, 1:200 females)
Genes for red and green are on X chromosome, blue is on chrom 7
Volume (hearing)
as molecules radiate outward, the difference between the waves of compessed molecules, and the compression of molecules between them determines volume. This is why
Pitch (hearing)
the frequency of vibration determines pitch
faster vibration=higher pitch
Auricle
is the external ear
funnels sound in toward the midle ear
sound passes through a bony tube
tympanic membrane
an epithelial sheet found inside the ear canal that vibrates when the sound wabes hit it
aka war drum
Middle ear
- is internal to the tympanic membrane
- is an air filled space containing 3 bones
- maintains a connection to the atmosphere by way of the eustacian tube–connects middle ear to throat
- the 3 bones magnify the vibrations from the tympanic membrane and transmit them to the inner ear by pounding on the oval window
eustacian tube
a connection between the middle ear and the throat
is what get clogged with changes to altitude etc.
Inner ear
- fluid filled
- Sectioned into 3 regions
- Vestibule-detects tilt of head
- Semicircular canals
- cochlea-hearing
Vestibule
in inner ear, detects the tilted position of the head. Especially due to acceleration or decelleration
semicircular canals
in inner ear- detect the rotation of the head
Cochlea
in inner ear– hearing
Basilar membrane
suspended within the cochlea, bounces with the vibrations (that are passed from the 3bones to the oval window)
Hair cells
in cochlea, are sandwiched between the basilar membrane and a stationart membrane located above it. As the basilar membrane bounces, the cilia hit the tectorial membrane, cilia bending depolarizes the hair cells.
Hearing sensory reception
All 3 regions of the inner ear use the same sensory receptors for three different things.
- Hair cell
- Bend cilia in one direction=depolarization
- Bend cilia in other direction=repolarization
Vestibulochlear nerce
carries action potentials in toward the brain
IN terms of action potentials, what is volume (hearing)
The frequency of action potential=volume
Sense of balance
Hair cells with their cilia
2 locations
- rotational equilibrium in the semicircular canals
- gravitational equilibrium in the vestibule
Equilibrium and alcohol
alcohol changes the viscosity of the endolymph, leading to misperception of balance, vertigo and movement.
Frequent and persistent use of alcohol can make the inner ear vulnerable to permanent changes in endolymph viscosity– leading to long lasting vertigo
Vertigo
dizziness and sense of rotation
-inflammation in brain or inner ear
unusual fluid movement/viscocity
Motion sickness
innerear senses a movement, but the visual stimuli doesnt match
Taste
aka gustation or chemoreception
taste buds
structures on the tongue, mouth and throat that hose taste cells
They are found within papillae, ~100 taste cells/papillae
Contain taste cells, supporting cells and basal cells
Basal cells replace gustatory cells every 7-10 days
is determined by genetics
toleration of spicy foods=fewer taste buds
The 5 different tastes
Salty, sweet, sour, bitter, umami
Salty taste sensation
Salt on tongue dissociates, Na enters and depolarizes the receptor–>opens ion channels
sour taste sensation
H+ in the acidic food blocks K+ channels. Loss of hyperpolarizing K+ allows the cells to come to threshold
Sweet, bitter, umami taste sensation
all signal through G-coupled protein receptors
Olfaction
- uses chemoreceptors
- 80% of flavor of food comes from smell
- olefactory neurons are replaced by stem cells every 2 months
- female sex hormones increase olfactory eurogenesis
olfactory epithelium
in nasal cavity, is location of cell bodies and dendrites of olfactory receptor cells.
Olfactory bulb
the acons of receptor cells extend through the base of the skill in into the olfactory bulb.
In the olfactory bulb, they synapse with neurons of the olfactory nerve
