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Mammalian Physiology II > Exam 4: Nervous System > Flashcards

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

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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

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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.

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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

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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

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6
Q

What are the two functional subdivisions of the autonomic NS?

A

Sympathetic
Parasympathetic

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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)

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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

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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

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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)

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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

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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

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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

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14
Q

What are synapses?

A

action potentials are conducted from 1 neuron to the next through synapses, always transmit in one direction

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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

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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

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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

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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

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19
Q

what are the 4 regions of the brain?

A

cerebellum
diencephalon
brain stem
cerebral hemispheres

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20
Q

What is the cerebellum responsible for?

A

subconscious coordination of movement
receives information from:
motor regions, proprioceptor, visual regions, vestibular apparatus (equilibrium)

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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

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22
Q

What is the diencephalon responsible for?

A

Thalamus - receives sensory info, passes to cerebral cortex
Hypothalamus - influences ANS, hormones
Epithalamus - hormones

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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

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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

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25
Q

What are the 5 lobes of the cerebral hemispheres?

A

frontal
parietal
occipital
temporal
insular

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26
Q

Why is the cerebral cortex known as the “executive suite”?

A

40% mass of brain
your conscious mind: awareness, sensory perception, voluntary motor imitation, communication, memory, storage, understanding

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27
Q

What are the 3 functional areas of the cerebral cortex?

A

motor- control voluntary movement
sensory - conscious awareness of sensation
association - integrate diverse information

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28
Q

Hemispheres have ——- control
—— of cortical function can occur in only 1 hemisphere

A

contralateral
lateralization (specialization)

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29
Q

What is contralateral control?

A

sensory information from left side and motor information to left side comes from the right hemisphere (and vice versa)

tracts cross near medulla oblongata

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30
Q

What is lateralization?

A

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

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31
Q

What is each hemisphere responsible for and how do they interact?

A

left - language, math, and logic
right- visual spatial skills, intuition, emotion, and artistic and musical skills

communicate via fiber tracks

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32
Q

Where are the motor areas of the cerebral cortex and what do they do?

A

frontal lobe

control of voluntary movement

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33
Q

Primary motor cortex:

A

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)

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34
Q

Pre motor cortex:

A

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

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35
Q

What do Broca and Wernickes’s areas do?

A

present in 1 hemisphere, (usually left), motor speech area that directs muscles of speech production, active in planning speech, voluntary motor activities

speech comprehension

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36
Q

What are sensory areas in the cerebral cortex?

A

conscious awareness of sensation
occur in parietal, insular, temporal, and occipital lobes
6 main areas:
somtaosensory
visceral sensation
gustatory
olfactory
auditory
visual

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37
Q

Describe the primary somatosensory cortex and the somatosensory association complex:

A

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

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38
Q

Describe the vestibular cortex:

A

part of insula
responsible for conscious awareness of balance
ex. position of head in space

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39
Q

Describe the visual areas:

A

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

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40
Q

Describe the auditory areas:

A

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

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41
Q

Describe the olfactory cortex:

A

primary cortex alone with olfactory bulbs and tracts
involved in conscious awareness of odors

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42
Q

Describe the gustatory cortex:

A

in insula, involved in perception of taste

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43
Q

Describe the visceral sensory area:

A

posterior to gustatory center, conscious perception of visceral sensations, such as upset stomach or full bladder

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44
Q

Explain the homeostatic imbalance

A

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

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45
Q

In general, what does the multimodal association areas do?

A

consists of most of the cortex
receives inputs from multiple sense
send output to multiple areas

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46
Q

What is the overall flow of information?

A

sensory receptors -> primary sensory cortex -> sensory association area -> multimodal association area -> premotor cortex -> motor cortex

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47
Q

More specifically, what does the multimodal association area do?

A

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

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48
Q

What are the 3 parts of multimodal association areas?

A

anterior association area
posterior association area
limbic association area

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49
Q

What is the anterior association area involved with?

A

aka prefrontal cortex
intellect
comlplex learning abilities (cognition)
recall
personality
working memory (abstract ideas, judgment, reasoning, persistence, planning)

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50
Q

What is the posterior association area involved with?

A

recognizing patterns and faces
localizing us and our surroundings in space
connects different sensory outputs into a complete picture

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51
Q

what does the limbic association area?

A

provides emotional impact that makes a scene important to us (ex. provides a sense of danger”
establishes memories that allow us to remember incidents

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52
Q

What can happen if there is association area damage?

A

anterior -> can cause mental and personality disorders (loss of judgment, attentiivness, and inhibitions)
Posterior -> loss of awareness and recognition of self

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53
Q

What is the functional systems?

A

networks of neurons that work together but are in different brain regions
includes: limbic system and reticular formation

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54
Q

What is the limbic system?

A

group of structures located medially on each cerebral hemisphere
emotional of affective (feelings) brain

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55
Q

Describe the structures of the limbic system:

A

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

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56
Q

How did the limbic system originate?

A

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

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57
Q

How does the limbic system work and why is it important?

A

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)

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58
Q

What is a psychosomatic illness?

A

visceral illnesses due to long term or acute emotional stress

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59
Q

——- and —– play a role in memory (limbic system)

A

hippocampus and amygdaloid body

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60
Q

Explain reticular formation

A

connects to many different regions of the brain
governs arousal (wakefulness) of the brain

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61
Q

What is the reticular activating system (RAS)? What are some regions involved in?

A

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
Q

What is the RAS inhibited by?

A

sleep centers in hypothalamus
alcohol, sleeping drugs, tranquilizers

servers injury results in permeant unconsciousness

63
Q

What is an EEG?

A

measures voltage differences between cortical areas
patterns of neuron activity are called brain waves

64
Q

What are brain waves?

A

different classes based on frequency
frequency - # of peaks in 1s (Hz)
amplitude - higher amplitude = more synchronous neuron activity

65
Q

What are the types of brain waves?

A

gamma - problem solving, concentration
beta- busy, active mind
alpha - reflective, restful
theta - drowsiness
delta - sleep, dreaming

66
Q

What happens if frequency of brain waves is too high or too low?

A

interferes with cerebral function
unconsciousness

67
Q

What is consciousness?

A

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
Q

What does consciousness include and what are the 4 clinical grades?

A

awareness of sensations
voluntary initiation and control of movement

alertness, drowsiness or lethargy, stupor, coma

69
Q

Explain fainting (syncope)
coma
brain death

A

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
Q

What is sleep?

A

state of partial unconsciousness (can be woken with stimulation)
cortical functions are surpassed (brain stem functions continue)
two major types: NREM and REM

71
Q

Explain the stages of sleep:

A

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
Q

How does sleep go into REM and NREM?

A

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
Q

Explain the end of sleep:

A

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
Q

Why is sleep important?
Slow wave (NREM 3/4)
REM

A

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
Q

What is narcolepsy and insomnia?

A

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
Q

What is memory and what are the two stages?

A

the storage and retrieval of information
essential for learning and incorporating exercises into behavior
two stages:
short term and long term

77
Q

short term vs long term memory

A

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
Q

How does memory processing occur?

A

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
Q

What are the two categories of memory?

A

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
Q

How are brain structures involved with memory?

A

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
Q

Explain declarative memory circuits:

A

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
Q

What is Alzheimers disease?
What is Parkinsons disease?

A

Loss of Act input
disrupts formation and retrieval of memories -> declarative circuits

loss of dopamine -> interferes with procedural memory

83
Q

Explain procedural memory circuits:

A

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
Q

What is anterograde amnesia?
Retrograde amnesia?

A

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
Q

What are some other memory circuits?

A

Motor memory - involves cerebellum
Emotional memory - involved amygdaloid body

86
Q

What molecular changes occur for memory formation to happen?

A

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
Q

What are endocannabinoids?

A

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
Q

Explain detection of stimuli and forms of stimuli:

A

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
Q

Explain detection of stimuli in terms of size:

A

size of receptive field varies:
large- location of stimulus is hard to determine (ex. skin on back and hip)

small- very specific (fingers)

90
Q

What is a nociceptor?

A

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
Q

What are thermoreceptors?

A

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
Q

What are chemoreceptors?

A

specialized to detect concentrations of specific chemicals dissolved in body fluids
H+, CO2, O2
sent to brain stem

93
Q

What are mechanoreceptors?

A

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
Q

What is a reflex?
simple

A

quick, involuntary, stereotyped reactions of glands and muscles to stimulation
stereotyped - occur the same way every time
involve a reflection arc

95
Q

What are the 5 components of a reflex arc?

A

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
Q

How can reflexes be classified?

A

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
Q

Explain reflex testing

A

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
Q

Explain monosynaptic reflexes:

A

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
Q

What is a muscle spindle?

A

muscle fibers wrapped in a sensory nerve that is excited by stretch

100
Q

Explain polysynaptic reflexes:

A

more than one synapse; > 2 neurons
more common than monosynaptic
interneuron is present
ex. withdrawn reflex

101
Q

Describe the reflex arc types:

A

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
Q

What are the 3 types of responses?

A

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
Q

reflexes can be —– and —–

A

somatic -> involve skeletal muscle

visceral -> involve glands, smooth muscle, cardiac muscle (salivary reflex baroreflex)

104
Q

What is sensory reception?

A

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
Q

What are the steps of sensory reception?
PUT ON NOTECARD

A

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
Q

Explain stimuli in smell and taste:

A

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
Q

What is the olfactory epithelium?

A

located in superior portion of nasal cavity, contains olfactory neurons

108
Q

Cell types in smell:

A

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
Q

Explain olfactory receptors:

A

~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
Q

Explain transduction in smell:

A

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
Q

Describe the olfactory pathway:
glomerulus and mitral cells

A

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
Q

Explain perception of smell:

A

mitral cells send impulses through olfactory tracts
2 destinations:
1. olfactory cortex (interprets and identifies smells)
2. Limbic system (emotion response to odors)

113
Q

How are some smells due to pain receptors?

A

located in nasal cavities, impulses travel through trigeminal nerve
ex. ammonia, chili peppers, menthol

114
Q

What is anosmia?
What is ucinate fits?

A

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
Q

What are pheromones?

A

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
Q

What are taste buds?

A

most found in papillae on tongue
contain:
gustatory cells - have taste hairs with receptors
basal cells- produce new gustatory cells

117
Q

What are the 5 taste sensations?

A

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
Q

What is a super taster?

A

people with an elevated sense of taste -> increased density of tased buds
ability to taste PTC (has genetic component)

119
Q

What is flavor tripping?

A

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
Q

What are the steps of reception of taste?

A

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
Q

How does transduction of taste occur?

A

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
Q

Explain the gustatory pathway:

A

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
Q

What is the influence of other senses on taste?

A

taste is strongly associated strongly with smell
o Mouth contains:
 Thermoreceptors – temperature of food
 Mechanoreceptors – texture of food
 Nociceptors – pain from “hot” foods

124
Q

What is ageusia?
How does COVID affect taste?

A

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
Q

explain the human eye and its 3 layers:

A

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
Q

What is myopia, cataracts, and cephalopod eyes:

A

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
Q

Explain the internal chambers an fluids in the vascular layer of the eye:

A

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
Q

What is the optic disc?

A

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
Q

What are photoreceptors in the eyes?

A

– 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

130
Q

What is the difference between rods and cones?

A

 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

131
Q

How does phototransduction occur in the eyes?

A

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

132
Q

What is color blindness?

A

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

133
Q

What is an additional retinal feature?

A

o Macula lutea
 Fovea centralis
* Sharp, detailed vision, high cone density

134
Q

Describe the visual pathway:

A

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

135
Q

Describe sensation vs. perception

A

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

136
Q

How does the brain help perceive visual information?

A

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

137
Q

What is auditory stimuli?

A

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

138
Q

Explain frequencies in sound waves:

A

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

139
Q

Explain the outer ear, middle ear and inner ear:

A

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

140
Q

What does the basilar membrane do in terms of hearing?

A

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

141
Q

What are the categories of deafness?

A

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

142
Q

What devices are available for hearing loss?

A

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

143
Q

What is ANSD?
What is Tinnitus?

A
  • 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
144
Q

Explain transmission of sounds:

A

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

145
Q

How does the brain aid in transmission of sounds?

A

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

146
Q

What is the vestibular system?

A

o Stimuli – gravity, angular acceleration and deceleration
o Involves –
 utricle and saccule
 Semicircular canals
o Signals sent through vestibular branch of vestibulocochlear nerve

147
Q

What is the utricle and saccule?

A
  • 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
148
Q

what are the semicircular canals?

A

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

149
Q

How does processing of sound occur in the brain?

A

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

150
Q

What is vertigo?

A

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

Mammalian Physiology II (3 decks)

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