Brain As Controller Flashcards
List examples of exteroreceptors and interorecepotrs
exteroreceptors = sensors for the external environment
1. classical senses
- eyes (see)
- cochlea (hear)
- vestibular apparatus (balance)
- olfactory epithelium (smell)
- cutaneous senses
- touch
- temperature,
- pressure
- nociceptors (pain)
- skin stretch
interoreceptors = sensors for the internal environment
1. chemical state
- chemosensors
- pH sensors
- osmoreceptors
- physical state
- stretch
- nociceptors
- muscle length
- muscle tension
- proprioceptors
- temperature
Define adequate stimulus, modality and perception
stimulus –> external / internal factor that is to be sensed
(adequate stimulus is smt that exceeds a certain threshold which enables body to recognize it)
modality –> types of sensation
sensation –> process by which smt becomes aware of stimulus
perception –> awareness of stimulus
Describe how the nervous system codes quality and intensity of sensation
Labeled line coding
- AP along distingct neral pathways are attributed with the “label” of that modality
(stimulus of the same type are picked up by the same receptor, sent down the same neural pathway, and synapse at the same region of the brain)
Synesthesia:
- impairments in labeling of sensory imformation
Describe psychophysical laws of measuring intensity of sensation
Stimulus intensity encoded by population and frequency
- Freq coding
- excites downstream CNS interneurons via temporal summation
(intense stimuli excite neurons more often) - Population coding
- excites CNS interneurons by spatial summation (intense stimuli excite more sensory neurons)
define receptive field
Areas of body surface / sensory organ that can excite a sensory neuron
- used to describe the area of input that influences activity of higher-order inter neurons / brain region
ex. 2 point discrimination
- allows us to distinguish closely spaced stimuli on finger tips but not on back
describe adaptation
ability of body to adapt to constant sensation via desensitization
- decreases sensation upon continued stimulation
- allows sensory signals to encode position, velocity (change in stimulus intensity) , and acceleration (change in change in stimulus intensity)
ex. allows us to wear clothes w/o us always feeling it
list the 4 mechanoreceptors in the skin and distinguish them on the basis of their frequency response and rate of adaptation
Classifications
- Depth
I: superficial
II: deep - rate of adaptation
SA = slowly adapting = tonic
RA = rapidly adapting = phasic
Types:
- Merkel (SA I)
Shape = disk
Location = near border between epidermis + dermis
Freq = 0.3 - 3 Hz
Stimulus = pressure
Function
- form and texture perception, low freq vibrations - Ruffini (SA II)
Shape = many-branched fibers inside cylindrical capsule
Location = dermis
Freq = 15 - 400 Hz
Stimulus = skin stretch + jt mvmt
Function
- static / dynamic skin deformation + skin stretch - Meissner (RA I)
Shape = stack of flattened cells w/ nerve fiber winding through
Location = in dermis but just below epidermis
Freq = 3 - 40 Hz
Stimulus = taps on skin
Function
- motion, slip/grip
- dynamic skin deformation - Pacinian Corpuscle (RA II)
Shape = layered capsule surrounding nerve fiber
Location = deep in skin
Freq = (10 to > 500 Hz)
Stimulus = rapid vibration
Function
- high freq vibration
- gross pressure changes
describe hot and cold sensors
Both hot and cold
- possess RA and SA characeristics (depends on T and dT/dt)
- allows for material identification (perception depends on body temperature and surface of skin)
Cold:
- free nerve endings w/ thin myelinated fibers
warm:
- free nerve endings w/ unmyelinated axons (low conduction speed)
distinguish between first and second pain
Both
- sensed by nociceptors (free nerve endings) w/ high threshold for mechanical, chemical and thermal stimuli)
First pain
- immediate, sharp and highly localized
Second pain
- after ~1s, diffuses, dull, aching
list types and locations of kinesthetic receptors
Kinesthetic sensing: Perception of limb movement, position, and force
- muscle recptors
- in muscle spindles and golgi tendon organs - joint receptors
- in capsules and ligaments of joints - skin receptors
- SA cutaneous mechanoreceptors (Ruffini, Merkel Cells in hairy skin)
define proprioception
perception of position and mvmt of body segments in relation to each other
- w/o vision, tough, or organs of equilibrium
analyze why the brain is positioned as the controller of the body
- Takes input from sensory systems
BRAIN + CNS
- Outputs signal to motor systems
- Motor system impacts environment which is sensed by sensory systems
identify the semicircular canals and distinguish them from the utricle and saccule
Semicirculuar canals (look like loop-de-loops)
- anterior, postierior, hortizontal loop
- filled with endolymph
- surrounded by perilymph
Utricle –> large fluid-filled cavity that directly connects to the semicircular canals
Saccule –> small fluid-filled cavity
identify the information provided by the semicircular canals, utricle, and saccule
Vestibular system
- gauge linear acceleration
Semicircular canals
- gauge rotational acceleration
hair cells in:
1. canals respond to:
- dynamic mvmt (velocity and acceleration) –> phasic info
2. utricle and saccule resond to:
- gravity (mvmt of tiny calcium carbonate crystals) –> tonic information
describe the circuit that results in vestibulo-ocular reflex (both in anatomical and control theoretic terms)
A: Control theoretic terms
vestibulo-ocular reflex –> stabilizing gase during head mvmt –> (steadicam of nervous system)
- provides translational + rotational stabilizaiton
- head moves to right, eye moves to left
B: anatomical terms
Contralateral projection to abducens nucleus:
2 pathways
1. lateral rectus muscle of the ipistaleral eye
2. medial rectus muscle of the contralateral eye
Supressed during active visual feedback
Describe how galvanic vestibular stimulation can be applied to parkinson’s disease
Parkinson disease
–> impaired motor function, tremors, slowness of mvmt, posture instability
Galvanic Vestibular stimulation (GVS)
- stimulate the vestibular system to improve motor function, posture stability, and tremors
Describe “Just Noticeable difference” and its applications in biomedical engineering
JND = amt of change in stimulus that creates perceptible increment in sensation
(smallest change in stimulus until observe notices a change)
- this threhold changes depending on velocity and if muscles are pre-contracted
Applications:
- JND used to design systems that provide subtle but perceptible feedback to users
(ex. robotic arms for precise control)
Explain how dizziness works
Move around –> liquids in semicircular canals move
Stop spinning BUT liquids keep moving
Hair in canals are still stimulated
Brain receives info from muscles that body has stopped moving BUT the vestibular system is still simulated (confusion on the position of the head)
Explain how vestibular sensing works
- canal forms ampulla –> enlarged region in junction w/ utricle
–> contains hair cells embedded in cupola - mvmt of endolymp relative to hair cells –> deformation of cells –> depolarization (inward K+)
- membrane potential changes –> transmition to afferent nerve fibers
