Exam 4: Nervous System Flashcards
1
Q
What are the 2 divisions of the nervous system?
A
CNS - brain and spinal cord, interprets sensory input and dictates motor output
PNS - the portion of NS outside CNS, spinal nerves to and from spinal cord, cranial nerves to and from brain, ganglia
2
Q
What are the 2 functional divisions of the PNS?
A
Afferent (sensory) - conveys impulses from periphery to CNS
Efferent (motor) - transmits impulses from CNS to effector organs
3
Q
What does the afferent division of the PNS do?
A
sensory information is transmitted from receptors to CNS
Types of receptors: pain, pressure, touch, stretch, chemoreceptors, baroreceptors, photoreceptors, etc.
4
Q
What does the efferent division of the PNS do?
A
signals sent to effectors from CNS
effectors can be muscles or glands
-smooth and skeletal muscle
-exocrine and endocrine glands
5
Q
What are the 2 regional differences of the PNS?
A
Somatic NS - conduct impulses from CNS -> skeletal muscle, voluntary
Autonomic NS - visceral motor nerve fibers regulate smooth muscle, cardiac muscle, and glands. involuntary
2 functional subdivisions
6
Q
What are the two functional subdivisions of the autonomic NS?
A
Sympathetic
Parasympathetic
7
Q
What are the two types of nervous system cells?
A
Neuroglia - small cells that surround and wrap (glue) delicate neurons, outnumber neurons 50:1
Neurons - (nerve cells) excitable cells that conduct electrical signals (action potentials)
8
Q
What are the special characteristics of neurons?
A
extreme longevity (last a lifetime)
no mitosis, few exceptions
high metabolic rate -> require continuous supply of oxygen and glucose
all have similar structure
9
Q
Explain the structure of a neuron:
Cell body
Dendrites
Axons
A
Cell body (soma) - rough ER and ribosomes (nissl bodies) -> synthesizes proteins and nucleus with nucleolus
Dendrites - receptive (input) region, convey incoming messages toward soma
Axons - (nerve fiber) of variable length -> conduct APs
10
Q
What are the functional characteristics of axons?
A
Conducting region of neuron
generates nerve impulses
transmits to axon terminal (terminal: region that secretes neurotransmitters into extracellular space)
can excite or inhibit neurons it contacts
communication with different neurons at same time (pre vs. postsynaptic)
axons rely on cell bodies to renown proteins and membranes (quickly decay if cut/damaged)
11
Q
How are neurons grouped?
What are the 3 groups?
A
grouped by direction in which nerve impulse travels relative to CNS
Sensory- transmit impulses from sensory receptors -> CNS, almost all are unipolar, cell bodies are located in ganglia (PNS)
Motor- carry impulses from CNS to effectors, multipolar, most cell bodies located in CNS (some autonomic neurons)
Interneurons- lie between motor and sensory neurons, most are entirely within CNS
12
Q
Action potentials:
why
where
what
A
principle means of neuron signaling
occur only in muscle cells and axons of neurons
brief reversal of membrane potential with change in voltage ~100mV
13
Q
Characteristics of action potentials:
A
do not decay over time (unlike graded potentials)
aka nerve impulse
involves opening an closing of specific voltage gated channels
14
Q
What are synapses?
A
action potentials are conducted from 1 neuron to the next through synapses, always transmit in one direction
15
Q
What are the 2 types of synapses?
A
chemical - 1st neuron secretes neurotransmitters that act on receptors in the next neuron, most synapses in CNS
electrical- gap junctions allow for ions to flow from 1 cell to the next, conduction of APs in smooth and cardiac muscle cells
16
Q
Explain integration of synapses:
A
synapses are involved in processing incoming information in the CNS
99% of info is discarded
important info is channeled
17
Q
Synapses transmit info between neurons but also…
A
amplify and inhibit signals
synapses can block weak signals or amplify them, and channel signals to the appropriate places
18
Q
How are synapses involved in storage (memory)?
A
each time certain sensory signals pass through a sequence of synapses, they get better at transmitting the same type of signal
after the sensory signals have passed through many times, the brain itself can also cause transmission of impulses even when sensory input is not excited
gives the perception of experiencing the original sensations although they are only memories of the sensations
19
Q
what are the 4 regions of the brain?
A
cerebellum
diencephalon
brain stem
cerebral hemispheres
20
Q
What is the cerebellum responsible for?
A
subconscious coordination of movement
receives information from:
motor regions, proprioceptor, visual regions, vestibular apparatus (equilibrium)
21
Q
What is the brain stem responsible for?
A
midbrain, pons, medulla oblongata
controls autonomic behaviors necessary for survival
cardiovascular and respiratory centers
contains fiber tracts that connect higher an lower neural centers
22
Q
What is the diencephalon responsible for?
A
Thalamus - receives sensory info, passes to cerebral cortex
Hypothalamus - influences ANS, hormones
Epithalamus - hormones
23
Q
What are the 3 regions of the cerebral cortex?
A
cortex - many higher brain functions
white matter - connects parts of hemispheres, different hemispheres, and hemispheres and the spinal cord
Basal nuclei: influences motor movements from cerebral cortex
reinforces purposeful motor activity
surpasses unwanted movement
24
Q
What are the two disorders associated with the not normal function of the basal nuclei?
A
Parkinsons - decrease in dopamine -> basal nuclei neurotransmitter -> tremors
Huntington’s - inherited, destruction of basal nuclei, increases involuntary movements, fidigtness
25
What are the 5 lobes of the cerebral hemispheres?
frontal
parietal
occipital
temporal
insular
26
Why is the cerebral cortex known as the "executive suite"?
40% mass of brain
your conscious mind: awareness, sensory perception, voluntary motor imitation, communication, memory, storage, understanding
27
What are the 3 functional areas of the cerebral cortex?
motor- control voluntary movement
sensory - conscious awareness of sensation
association - integrate diverse information
28
Hemispheres have ------- control
------ of cortical function can occur in only 1 hemisphere
contralateral
lateralization (specialization)
29
What is contralateral control?
sensory information from left side and motor information to left side comes from the right hemisphere (and vice versa)
tracts cross near medulla oblongata
30
What is lateralization?
division of labor between hemispheres
cerebral dominance - refers to hemisphere that is dominant for language - usually left side dominance in 90% of humans -> right handedness
31
What is each hemisphere responsible for and how do they interact?
left - language, math, and logic
right- visual spatial skills, intuition, emotion, and artistic and musical skills
communicate via fiber tracks
32
Where are the motor areas of the cerebral cortex and what do they do?
frontal lobe
control of voluntary movement
33
Primary motor cortex:
Pyramidial cells - large neurons, conscious control of precise, skilled, skeletal muscle movement
Pyramidal (corticospinal) tracts - long axons that project down spinal cord
synapse in brain stem or spinal cord, voluntary motor function
Somatotopy - all muscles mapped to area on primary motor cortex (motor homunculi - caricature)
34
Pre motor cortex:
helps plan movements - staging area for skilled motor activities
controls learned, repetitions, or patterned motor skills
coordinates simultaneous or sequential actions
controls voluntary actions that depend on sensory feedback
35
What do Broca and Wernickes's areas do?
present in 1 hemisphere, (usually left), motor speech area that directs muscles of speech production, active in planning speech, voluntary motor activities
speech comprehension
36
What are sensory areas in the cerebral cortex?
conscious awareness of sensation
occur in parietal, insular, temporal, and occipital lobes
6 main areas:
somtaosensory
visceral sensation
gustatory
olfactory
auditory
visual
37
Describe the primary somatosensory cortex and the somatosensory association complex:
receives sensory info from skin and proprioceptors of skeletal muscle, joints, and tendons
spatial discrimination - identification of body region being stimulated
Integrates sensory info from ^^ for understanding of object
determines size, texture, and relationship of parts of objects been felt
38
Describe the vestibular cortex:
part of insula
responsible for conscious awareness of balance
ex. position of head in space
39
Describe the visual areas:
Primary visual cortex- located on posterior tip of occipital lobe, receives visual information from retinas
Visual association area- uses past visual experiences to interpret visual stimuli (color, form, or movement) es, recognize faces
40
Describe the auditory areas:
Primary auditory cortex- interprets info form inner ear as pitch, loudness, and location
Auditory association area: located posterior to ^^, stores memories of sounds and permits perception of sound stimulus
41
Describe the olfactory cortex:
primary cortex alone with olfactory bulbs and tracts
involved in conscious awareness of odors
42
Describe the gustatory cortex:
in insula, involved in perception of taste
43
Describe the visceral sensory area:
posterior to gustatory center, conscious perception of visceral sensations, such as upset stomach or full bladder
44
Explain the homeostatic imbalance
damage to primary visual cortex results in functional blindness
by contrast, individuals with a damaged visual association are can see, bit they do not comprehend what they are looking at
45
In general, what does the multimodal association areas do?
consists of most of the cortex
receives inputs from multiple sense
send output to multiple areas
46
What is the overall flow of information?
sensory receptors -> primary sensory cortex -> sensory association area -> multimodal association area -> premotor cortex -> motor cortex
47
More specifically, what does the multimodal association area do?
takes information and
gives it meaning
stores it in memory
ties it with perviously experience and knowledge
decides what action to take
where sensations, thoughts, and emotions become conscious
48
What are the 3 parts of multimodal association areas?
anterior association area
posterior association area
limbic association area
49
What is the anterior association area involved with?
aka prefrontal cortex
intellect
comlplex learning abilities (cognition)
recall
personality
working memory (abstract ideas, judgment, reasoning, persistence, planning)
50
What is the posterior association area involved with?
recognizing patterns and faces
localizing us and our surroundings in space
connects different sensory outputs into a complete picture
51
what does the limbic association area?
provides emotional impact that makes a scene important to us (ex. provides a sense of danger"
establishes memories that allow us to remember incidents
52
What can happen if there is association area damage?
anterior -> can cause mental and personality disorders (loss of judgment, attentiivness, and inhibitions)
Posterior -> loss of awareness and recognition of self
53
What is the functional systems?
networks of neurons that work together but are in different brain regions
includes: limbic system and reticular formation
54
What is the limbic system?
group of structures located medially on each cerebral hemisphere
emotional of affective (feelings) brain
55
Describe the structures of the limbic system:
Amygdaloid body - responding to perceived threats with fear or agression (angry or fearful facial expression)
Cingulate gyrus - expression emotions through gestures, resolving mental conflicts when frustrated
56
How did the limbic system originate?
Originated as "rhinencephalon"
-smell brain
-over evolutionary history has taken on new functions having to do with emotions and memory
Parts still devoted to smell: olfactory bulbs and tracts, olfactory cortices
57
How does the limbic system work and why is it important?
connected to higher and lower brain regions
output relayed through hypothalamus (along with ANS)
interacts with prefrontal lobes
relationship between feelings and thoughts (react emotionally to things we understand to be happening, consciously aware of our emotions)
58
What is a psychosomatic illness?
visceral illnesses due to long term or acute emotional stress
59
------- and ----- play a role in memory (limbic system)
hippocampus and amygdaloid body
60
Explain reticular formation
connects to many different regions of the brain
governs arousal (wakefulness) of the brain
61
What is the reticular activating system (RAS)? What are some regions involved in?
sends continuous stream of impulses to cerebral cortex (keeps cortex alert and conscious, enhances excitability)
filters sensory inputs (repetitive, familiar, or weak signals are filtered out, unusual, significant, or strong impulses reach consciousness)
Some regions are involved in sleep, control of skeletal muscles, visceral motor functions (vasomotor, respiratory, cardiac)
62
What is the RAS inhibited by?
sleep centers in hypothalamus
alcohol, sleeping drugs, tranquilizers
servers injury results in permeant unconsciousness
63
What is an EEG?
measures voltage differences between cortical areas
patterns of neuron activity are called brain waves
64
What are brain waves?
different classes based on frequency
frequency - # of peaks in 1s (Hz)
amplitude - higher amplitude = more synchronous neuron activity
65
What are the types of brain waves?
gamma - problem solving, concentration
beta- busy, active mind
alpha - reflective, restful
theta - drowsiness
delta - sleep, dreaming
66
What happens if frequency of brain waves is too high or too low?
interferes with cerebral function
unconsciousness
67
What is consciousness?
involves simultaneous activity of large areas of the cerebral cortex
is superimposed on other types of neural activity
is holistic and interconnect
*difficult to define*
68
What does consciousness include and what are the 4 clinical grades?
awareness of sensations
voluntary initiation and control of movement
alertness, drowsiness or lethargy, stupor, coma
69
Explain fainting (syncope)
coma
brain death
brief loss of consciousness, often indicates inadequate food flow to obtain due to low blood pressure
total unresponsiveness to stimuli for extended time (differs from sleep as during sleep, brain is active and O2 consumption is higher) can occur due to brain trauma, tumors/infections or brain stem, hypoglycemia, drug OD, liver of kidney failure
brain waves occur spontaneously, even when unconscious or in a coma
-absence is evidence of brain death, irreparable brain damage
70
What is sleep?
state of partial unconsciousness (can be woken with stimulation)
cortical functions are surpassed (brain stem functions continue)
two major types: NREM and REM
71
Explain the stages of sleep:
awake
REM: skeletal muscle (except ocular and diaphragm) are inhibited; most dreaming occurs
NREM 1: relaxation begins, EEG shows alpha waves; arousal is easy
NREM 2: irregular EEG with sleep spindles; arousal more difficult
NREM 3: sleep deepens, theta and delta waves appear, vital signs decline
NREM 4: EEG is dominated by delta waves, arousal is difficult; bed wetting, night terrors, sleepwalking may occur
72
How does sleep go into REM and NREM?
we slip deeper and deeper into sleep and then:
EEG activity changes abruptly, becomes more typical of awake state, cycles over and over
During REM: oxygen use is higher than awake state, muscles are inhibited
73
Explain the end of sleep:
first REM lasts 5-10 mins
Final REM lasts 20-50 mins
longest dreams are at end of sleep period
before waking: neurons release orexins
act as wake up chemicals, cause neurons of reticular formation to fire at maximal rates
74
Why is sleep important?
Slow wave (NREM 3/4)
REM
sleep requirements decline with age
restorative, neural activity is greatly reduced, when deprived of sleep, will spend more time in slow wave sleep next time
may give brain time to work through emotional problems in dream imagery, reverse learning (accidental, repetitive, meaningless input eliminated from neural networks "we dream to forget"), surpassed by alcohol
75
What is narcolepsy and insomnia?
abrupt lapses into REM sleep (from awake state), last ~15 mins, fewer cells that secrete orexin
inability to sleep enough, can be related to age, stress, depression
76
What is memory and what are the two stages?
the storage and retrieval of information
essential for learning and incorporating exercises into behavior
two stages:
short term and long term
77
short term vs long term memory
STM - working memory, limited to ~7-8 chunks of information
LTM - much greater capacity, "memory bank" is continually changing, ability to store and retrieve information declines with age
78
How does memory processing occur?
transfer from STM -> LTM infulenced by:
emotions (learn best when alert, motivated, surprised, and aroused)
rehearsal / repetition (enhances memory)
association (tying "new" info to info stored in LTM)
automatic memory (memories not consciously formed)
79
What are the two categories of memory?
distinguishes between factual knowledge and skills
declarative (fact) memory:
learning information such as names, faces, words, and dates
memories stores with the contact in which they were learned
Nondeclarative memory:
acquired through experiences and usually repetition, difficult to unlearn
includes: procedural (skills) memory like piano playing, motor memory like riding a bike, and emotional memory like reacting to a rattlesnake rattle
80
How are brain structures involved with memory?
pieces of memories are stored near regions of the brain that need them. New inputs can be quickly associated with old (visual memories are stored in the occipital cortex, memories of music stored in temporal cortex, etc)
memories are retrieved when the same sets of neurons that were involved in memory formation are stimulated
81
Explain declarative memory circuits:
sensory info processed in association cortices
impulses sent to medial temporal lobe (communicates with prefrontal cortex and thalamus, involved in memory consolidation and access)
basal forebain neurons inout to medial temporal lobe and prefrontal cortex (release Ach-> primes them to form new memories)
82
What is Alzheimers disease?
What is Parkinsons disease?
Loss of Act input
disrupts formation and retrieval of memories -> declarative circuits
loss of dopamine -> interferes with procedural memory
83
Explain procedural memory circuits:
sensory and motor inputs processed in association cortices
impulses sent to basal nuclei (relay inputs to premotor cortex via thalamus)
basal nuclei receive input from neurons of substantial nigra (midbrain) -> dopamine release -> necessary for procedural memory circuits
84
What is anterograde amnesia?
Retrograde amnesia?
damage to hippocampus and medial temporal lobe on one side (results in slight memory loss)
bilateral destruction - widespread amnesia
affects declarative memory (consolidated memories are not lost, new sensory inputs cannot be associated with old, person is stuck in the "here and now")
procedural memory involved a different circuit (person can still learn skills such as drawing)
Retrograde - loss of memories from past, caused by damage to memory storage areas
85
What are some other memory circuits?
Motor memory - involves cerebellum
Emotional memory - involved amygdaloid body
86
What molecular changes occur for memory formation to happen?
neuron RNA content is altered (new mRNAs delivered to axons and dendrites) -> dendritic spines change (dendritic spines receive input from other axons) -> unique proteins are deposited at synapses involved in long-term memory
# and size of presynaptic terminals may increase, presynaptic neurons release more neurotransmitters
molecular changes are part of LTP (increase in synaptic strength)
NMDA receptors can initate changes (receptor for the neurotransmitter glutamate, when activated, cause calcium to flow into postsynaptic cell (activated by arrival for action potential at synapse), calcium influx activates enzymes that: modify pre and post synaptic proteins (use messengers like NO and endocannabinoids) and activate genes that lead to synthesis of synaptic proteins)
These changes lead to long lasting increases in synaptic strength (though to underlie memory, drugs that enhance this process are being tested)
87
What are endocannabinoids?
ECS - influences synaptic communication, affects a variety of processes throughout the nervous system (includes memory and learning)
high does of THC can temporarily disrupt short-term memory
88
Explain detection of stimuli and forms of stimuli:
receptors (dendrites of sensory neurons) detect stimuli
specificity caused by: structure of receptor cell and accessory cells that shield receptor cells from other stimuli
sharp objects, temperature, pH, O2: CO2 levels, pressure: stretch, light:energy, sound
89
Explain detection of stimuli in terms of size:
size of receptive field varies:
large- location of stimulus is hard to determine (ex. skin on back and hip)
small- very specific (fingers)
90
What is a nociceptor?
pain receptor
locations: skin, joint capsules, blood vessel walls
free nerve endings stimulated by depolarization
not very specific (detect changes in temp, mechanical damage, dissolved chemicals)
different types of fibers (myelinated - fast pain, prickling -> conscious awareness, nonmyelinated - slow pain slow pain, ache -> nonspecific location)
91
What are thermoreceptors?
temperature receptors
locations: free nerve endings in dermis, sk. muscle, hypothalamus, liver
cold receptors are more common than heat receptors
sent to thalamus, sometimes primary sensory cortex
92
What are chemoreceptors?
specialized to detect concentrations of specific chemicals dissolved in body fluids
H+, CO2, O2
sent to brain stem
93
What are mechanoreceptors?
stimulated by distortion of plasma membrane
3 classes:
1. tactile: touch, pressure and vibration
2. baroreceptors: pressure
3. proprioceptors: position of joints and muscles in space
94
What is a reflex?
simple
quick, involuntary, stereotyped reactions of glands and muscles to stimulation
stereotyped - occur the same way every time
involve a reflection arc
95
What are the 5 components of a reflex arc?
PUT ON NOTE CARD ->
* 5 components of a Reflex arc:
o 1. Arrival of stimulus and activation of receptor
1. Receptors: sensory receptor detects a stimulus
o 2. Activation of sensory neuron
2. Sensory neuron: transmits afferent impulses to the CNS
o 3. Integration-connection between neurons
3. Integration center: point of synaptic contact between neurons, may include one or more interneurons
o 4. Activation of motor neuron
4. Motor neuron: conducts efferent impulses from the integration center to an effector organ
o 5. Response by effector
5. Effector: muscle or glands responds to the efferent impulses
96
How can reflexes be classified?
length of delay between stimulus and action corresponds to number of synapses
can be classified as:
development
response
complexity
processing iste
some examples: monosynaptic (stretch) polysnaptic (withdrawal)
PUT CHART ON NOTECARD
97
Explain reflex testing
many reflexes can be easily tested
allows for assessment of NS
abnormal, exaggerated, or absent responses can indicate issues with nervous system before other symptoms are present
if spinal cord is damaged, tests can help identify region injured
98
Explain monosynaptic reflexes:
simplest reflex arc (very fast) 1 synapse
no interneuron
ex. stretch reflex
->
receptor: muscle spindle
stimulus: muscle stretch
effector: skeletal muscle
result: muscle contraction
functions: resist gravity, maintain muscle tone and postureW
99
What is a muscle spindle?
muscle fibers wrapped in a sensory nerve that is excited by stretch
100
Explain polysynaptic reflexes:
more than one synapse; > 2 neurons
more common than monosynaptic
interneuron is present
ex. withdrawn reflex
101
Describe the reflex arc types:
intrinsic (inborn) - rapid predictable motor response to stimuli, knee jerk, withdrawal from pain
acquired (learned) - results from practice or repetition, emergency stop while driving
cranial - processing in brain, cranial nerves
spinal - processing in spine, spinal nerves
102
What are the 3 types of responses?
consensual - response occurs on both sides, regardless of side stimulated
contralateral - response occurs on opposite side of the body as stimulus
ipsilateral - response occurs on same side of the body as stimulus
103
reflexes can be ----- and -----
somatic -> involve skeletal muscle
visceral -> involve glands, smooth muscle, cardiac muscle (salivary reflex baroreflex)
104
What is sensory reception?
senses provide information about an organism and its environment (detected by sensory receptors)
o General senses: temperature, pain, pressure, vibration
o Special senses: vision, hearing, smell, taste, equilibrium (balance and body position)
105
What are the steps of sensory reception?
PUT ON NOTECARD
o 1. Reception – sensory receptors are activated by stimuli (can be mechanical, chemical, light, etc.)
o 2. Transduction – sensory signal is translated to an electrical signal in nervous system
o 3. Encoding and transmission – encoding gives information about the stimulus (type, location, duration, strength), Transmission: signal is sent through nervous system
o 4. Perception – interpretation of a sensation (in animals with complex NS, this can involve processing of information), may result in a specific response
106
Explain stimuli in smell and taste:
both smell and taste molecules binding to chemoreceptors -> neurons are activated
for a substance to smell -> must release molecule into the air, we must have the chemoreceptors for those molecules
107
What is the olfactory epithelium?
located in superior portion of nasal cavity, contains olfactory neurons
108
Cell types in smell:
olfactory neurons - dendrites have 5-20 olfactory cilia which have receptors, axons travel towards olfactory bulbs
supporting cells - cushion olfactory receptors
basal cells - give rise to new olfactory receptors
Bowmans gland - secrete mucus
109
Explain olfactory receptors:
~12 million on olfactory cilia
~1000 genes encoding unique receptor proteins -> each olfactory neuron has only one type of receptor protein
odor molecule bind to several different receptor types -> different combinations of detection creates patterns that let us distinguish ~10,000 odors
110
Explain transduction in smell:
odorant bind to receptor protein -> a series of molecule are activated, eventually opening a gated-ion channel -> Na+ and Ca2+ enter -> Na+ causes depolarization (AP) and Ca2+ decreases response to sustained stimulus ("nose blindness")
111
Describe the olfactory pathway:
glomerulus and mitral cells
action potential travels through axon (synapses with mitral cells) -> glomeruli (site of olfactory neuron/mitral cell synapse, axons from neurons with same type of receptor converge on same type of glomerulus, different odors activate specific sets of glomeruli)
mitral cells (amplify and transmit impulses, suppress weak stimuli)
112
Explain perception of smell:
mitral cells send impulses through olfactory tracts
2 destinations:
1. olfactory cortex (interprets and identifies smells)
2. Limbic system (emotion response to odors)
113
How are some smells due to pain receptors?
located in nasal cavities, impulses travel through trigeminal nerve
ex. ammonia, chili peppers, menthol
114
What is anosmia?
What is ucinate fits?
Inability to smell, caused by damage to olfactory nerves, inflammation, aging, congenital asnomia
olfactory hallucinations - usually and unpleasant odor, may result from irritation of olfactory pathway of head trauma
olfactory auras - transient ucinate fits, epileptics before a seizure
115
What are pheromones?
chemicals released by an animal that affects the behavior and physiology of others in the same species
VNO -> contains pheromone receptor cells, secretes gonadotropin releasing hormone, present in many mammal species, present in ~1/3 of human population
116
What are taste buds?
most found in papillae on tongue
contain:
gustatory cells - have taste hairs with receptors
basal cells- produce new gustatory cells
117
What are the 5 taste sensations?
o 1. Sweet – elicited by sugars, alcohols, amino acids
o 2. Sour – elicited by H+ ions
o 3. Salty – elicited by metal ions (Na+)
o 4. Bitter – elicited by alkaloids
o 5. Umami – elicited by glutamate and aspartate
Taste buds respond to all 5 qualities, each taste cell has receptors for one taste quality
118
What is a super taster?
people with an elevated sense of taste -> increased density of tased buds
ability to taste PTC (has genetic component)
119
What is flavor tripping?
miracle fruit (Synsepalum dulcificum)
o Contains proteins that bind to tase buds (suppresses sour receptors, activates sweet receptors)
o Sour foods taste sweet (lasts ~1hr)
120
What are the steps of reception of taste?
o 1. Tastant molecule dissolve in salvia and bind receptors on gustatory hairs
o 2. Depolarization (graded potential) -> neurotransmitter release
Depolarization can occur in different ways
o 3. Neurotransmitters bind to dendrites, triggering action potentials in afferent nerves
121
How does transduction of taste occur?
How does depolarization occur?
o Salty taste – Na+ influx depolarizes gustatory cells
o Sour taste – H+ opens gated ion channels
o Bitter, sweet, umami taste – receptor is coupled with G protein, activation releases Ca2+ which then opens ion channels
122
Explain the gustatory pathway:
o Afferent nerves travel through:
Facial nerve VII
Glossopharyngeal nerve IX
Vagus nerve X
o Impulse pathway:
Solitary nucleus (medulla oblongata) -> triggers reflexes (salivation, gastric juices, gaging, vomiting)
Thalamus -> gustatory cortex (interpretation of smells)
123
What is the influence of other senses on taste?
taste is strongly associated strongly with smell
o Mouth contains:
Thermoreceptors – temperature of food
Mechanoreceptors – texture of food
Nociceptors – pain from “hot” foods
124
What is ageusia?
How does COVID affect taste?
loss of taste, less common than anosmia
Can occur due to: trauma, head and neck radiation for cancer treatment
one symptom is temporary loss of taste and smell
Possible causes: damage to support cells around nerves, swelling and nasal congestion
Treatments: smell training therapy
125
explain the human eye and its 3 layers:
70% of our sensory receptors are in the eyes (detect light, allows us to form images, see movement, etc.)
o Layers of the eye:
1. Fibrous layer –
* Sclera: white / protective, shape / anchoring site
* Cornea: transparent, allows light to enter the eye, well supplied with nerve endings, transplant potential
2. Vascular layer (uvea) –
* Choroid: highly vascularized, darkly pigmented
* Ciliary body: lens- transparent, biconvex
* Iris: pupil, sphincter pupillae (Parasympathetic stimulation, decrease pupil size), dilator pupillae (sympathetic stimulation, increase pupil size)
Inner layer –
* Retina: pigmented layer, neural layer (sensory)
* Photoreceptors: rods and cones
126
What is myopia, cataracts, and cephalopod eyes:
cornea and lens focus light onto retina, in myopia, the eye is too long – light focused in front of retina
lens or surrounding membranes become cloudy, one or both eyes (develops slowly), especially common in the elderly, caused by aging, injury, surgery, diabetes, treatments depend on severity, age, health, and how problematic it is
In human eyes: nerve fibers travel in front of retina, creates blind spot where nerve fibers pass through retina
In cephalopod eyes: nerve fibers travel behind retina, no blind spot
127
Explain the internal chambers an fluids in the vascular layer of the eye:
o Lens and ciliary zonule
o Posterior segment – vitreous humor, forms in embryo (risk of floaters)
o Anterior segment – anterior/posterior chambers, aqueous humor (drains, filters)
128
What is the optic disc?
optic nerve
o Where the optic nerve and arteries and veins enter the eye
No photoreceptors here, creates blind spot
Visual filling – brain fills in gaps of visual field
129
What are photoreceptors in the eyes?
– the retina contains millions of them
o Send signals to the brain in response to light
o Two types: rods and cones
o Signal travels through optic nerve
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What is the difference between rods and cones?
Rods – low light levels, night and peripheral vision
Cones – low sensitivity, high light levels: day vision, 3 types: color (trichromatic) vision
Retinal dispersion –
* Rods – peripheral
* Cones – center
* Averted vision
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How does phototransduction occur in the eyes?
light energy -> graded potential
Rods and cones – outer segments (photopigments), inner segments
Bipolar cells – 1st order neuron
Ganglion cells – 2nd order neuron
Rods and cones are “wired” differently
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What is color blindness?
o Color deficiency (not always vision in black and white), varying degress of severity
o Abnormal photopigments on cone cells
Red-green color blindness:
* Deuteranomaly (most common) – green cone photo-pigment is abnormal, yellow/green appear redder, violet and blue difficult to decipher
* Protanopia (rare) – no working red cone cells
Achromatopia (rare): total color blindness, more common among men than women
o 8% of males, 0.5% of females – X chromosome linked
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What is an additional retinal feature?
o Macula lutea
Fovea centralis
* Sharp, detailed vision, high cone density
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Describe the visual pathway:
o Optic nerves -> optic chiasma -> optic tracts
o Each eye has a visual field – what we see in each eye, information from left side of each visual field travels to right side of brain and vice versa
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Describe sensation vs. perception
o Sensation – sensory fibers responding to stimulus by producing action potentials
o Perception – what our brains make of that information, light -> color, the image received by the retina is flipped (brain perceives it as right side up)
o Sensory processing is complex – integrating multiple senses, perceiving stimuli as meaningful whole
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How does the brain help perceive visual information?
o Hypothalamus – regulated day/night cycle (circadian rhythm)
o Thalamus – relays information on movement, depth perception
o Primary visual cortex – images, form, color, motion
o Visual association area – use past experiences to inform new ones
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What is auditory stimuli?
o Sound waves: pressure waves that move through the air
o Characteristics:
Frequency – measured in Hz -> #of waves per second, higher frequency = higher pitch
Wavelength – shorter wavelength = higher pitch
Amplitude – volume, measured in decibels
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Explain frequencies in sound waves:
most people perceive sounds between 30 and 20,000 Hz
o Ability to hear high frequencies decreases with age
o Animals can often hear higher frequencies
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Explain the outer ear, middle ear and inner ear:
o Outer ear -
Auricle: collects soundwaves (angle collects more from front), amplifies sound waves
o Middle ear –
Soundwaves cause tympanum to vibrate, energy transferred through ossicles. Malleus -> incus -> stapes
o Inner ear –
Oval window: first part of inner ear, receives vibrations from stapes and transfers energy to fluid inside cochlea
Cochlea: contains receptors for transduction of mechanical waves into electrical signals, lined with basilar membrane
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What does the basilar membrane do in terms of hearing?
different regions vibrate based on frequency of sound waves
o Hair cells of the basilar membrane contact tectorial membrane above:
When bent, gated ion channels open and hair cell membrane is depolarized
Signal is transmitted to cochlear branch of vestibulocochlear nerve
Volume determined by how many hair cells in a region
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What are the categories of deafness?
o Conductive hearing loss – sounds don’t make it through outer or middle ear, may be due to blockage of ear canal, infection, bone abnormality, or eardrum damage, often treatable by surgery
o Sensorineural hearing loss – issues with inner ear of vestibulocochlear nerve, can be caused by aging, exposure to loud noise, injury, disease, hearing aids often beneficial
o Mixed hearing loss – includes conductive and sensorineural hearing loss
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What devices are available for hearing loss?
o Hearing aids – amplify sounds, can’t help if inner ear or nerves are damaged
o Cochlear implants – picks up sounds and sends them to the auditory nerve, doesn’t restore hearing but can help a person get an idea of sounds in the environment and understand speech
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What is ANSD?
What is Tinnitus?
* ANSD: sounds enter normally, but due to damage to inner ear or nerves, brain cant understand the sound data, speech is often distorted and hard to understand (impairment of speech perception worse than degree of hearing loss), primarily affects children
* Tinnitus – another clinical application
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Explain transmission of sounds:
information is transmitted through the cochlear branch of the vestibulocochlear nerve, brain can send signals back to cochlea (changes length of hair cells, sharpens or dampens response to certain frequencies
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How does the brain aid in transmission of sounds?
o Auditory cortex – processes auditory information
o Auditory association area - stores memories of sound and permits perception of sound stimuli
o Wernicke’s area – involved in speech comprehension
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What is the vestibular system?
o Stimuli – gravity, angular acceleration and deceleration
o Involves –
utricle and saccule
Semicircular canals
o Signals sent through vestibular branch of vestibulocochlear nerve
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What is the utricle and saccule?
- respond in acceleration in a straight line (gravity)
* Both have hair cells lying below a gelatinous layer
o Stereocilia project into gelatin, calcium carbonate crystals (otoliths) embedded in gelatin
* When head is tilted:
o Crystals are pulled down by gravity -> gelatin shifts, bending stereocilia -> neurons signal to the brain that the head is tilted
* Involved in maintenance of balance
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what are the semicircular canals?
3 loops arranged in 3 plans
* Base of each contains hair cells projecting into a gelatinous cap (cupula)
* Monitor angular acceleration and declaration from rotation
o Input from all 3 canals allows detection of acceleration and deceleration in 3D
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How does processing of sound occur in the brain?
o Cerebellum – important for coordinated movements
o Temporal cortex – responsible for feelings of dizziness
o Autonomic NS areas in brainstem – motion sickness
o Somatosensory cortex – monitors movements of external world and self-movement
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What is vertigo?
causes sensation that you or the environment is spinning, attacks can be sudden of last for a while
o Symptoms – loss of balance, motion sickness, dizziness
o Causes – benign paroxysmal position vertigo – crystals in semicircular canals come loose, causes problems when changing head position, migraines
