Module 10: Special Senses Flashcards
1
Q
• Form of mechanical energy
• Waves of particle displacement
*Longitudinal vibrations of molecules in alternating phases of compression and rarefaction
• Produced by pressure changes (sound pressure) which is picked up by the ear and translated into audible sound
A
Sound
2
Q
PHYSICAL CHARACTERISTICS OF SOUND:
A
- Frequency
- Intensity
- Phase
3
Q
• Determines pitch
• Expressed in Hertz (Hz)
- Number of cycles per second
A
Frequency
4
Q
Audible range, Greatest sensitivity and Speech
A
Audible range: 20 – 20,000 Hz
Greatest sensitivity: 1000 – 4000 Hz
Speech: 300 – 3500 Hz
5
Q
• frequency at which a mass vibrates with the least amount of external force
A
Resonant frequency
6
Q
- Determines loudness
- Expressed in decibels (dB)
- Decidbel: unit of sound
- expressed in terms of the logarithm of their intensity
- a 10 fold increase in energy is 1 bel
- 0.1 bel is a decibel
- 1 decibel is an increase in sound energy of 1.26 times
A
Intensity
7
Q
• Prolonged exposure to how many db SPL can cause deafness?
A
more than 80 dB SPL
8
Q
Sound and dB SPL
A
- Jet plane, Gunshot blast: 140 dB SPL
- Automobile horn: 120
- Motor cycle engine: 100
- Average factory: 80-90
- Noisy restaurant, busy traffic, shouting: 80
- Conversational speech: 65
- Quiet office: 40
- Soft whisper: 30
9
Q
dB SPL
A
- approx 140 dB SPL: threshold for pain
- approx 120 dB SPL: damage to cochlear hair cells
- approx 110 dB SPL: threshold for discomfort
- long exposue to >90 dB SPL may harm the hearing
- > 80 dB SPL: “loud sound”
10
Q
The Tympanic Membrane and the Ossicular System
A
• Tympanic membrane functions to transmit vibrations in the air to the cochlea
• Amplifies the signal because the area of the tympanic membrane is 17 times larger than the oval window
• Tympanic membrane connected to the ossicles
- malleus
- incus
- stapes
11
Q
• can be damaged by loud sound (120 dB) or some drugs especially those for treatment of Tuberculosis (Pyrazinamide, Ethambutol)
A
Tympanic Membrane
12
Q
• equalizes the pressure between the ear and the atmosphere around us
A
Eustachian Tube
13
Q
• two muscles attach to the ossicles
- stapedius
- tensor tympani
• a loud noise initiates reflex contraction after 40 - 80 milliseconds
• attenuates vibration going to cochlea
• serves to protect cochlea and damps low frequency sounds i.e., your own voice
A
Attenuation of Sound by Muscle Contraction
Attenuation Reflex
14
Q
• smallest muscle in our body; it contracts if a loud noise is initiated
A
Stapedius
15
Q
Sound Conduction to the Cochlea
A
- Bone conduction - Plays a role only in transmission of extremely loud sound
- Air (ossicular) conduction - Main pathway for normal hearing; most common form of hearing
16
Q
Amplification of Sound Pressure:
A
- Sound collection
2. Impedance matching
17
Q
• Resonator
• Cause minor increase in sound intensity
- By 10 – 20 dB between 2000 – 5500 Hz
- EAC resonant frequency: ~3000 Hz
A
The External Ear
18
Q
• Displacement of TM and ossicular chain varies with frequency and intensity
- Most efficient: 500 – 3000 Hz
A
The Middle Ear
19
Q
- increase sound pressure from Tympanic Membrane to oval window: 10 – 35 dB (22-fold)
- the louder the sound, the lower the ossicular displacement (the movement of the ossicular bones get lower when the sound is louder.
- Area disparity between the resonating TM and stapes footplate
- Lever action of the ossicular chain
• Requires equal pressure between the atmosphere and the middle ear cavity
- Maintained by the periodic opening of the eustachian tubes
A
Impedance Matching
20
Q
- system of three coiled tubes separated by membranes into the scala tympani, scala media, scala vestibuli
- sound waves cause back and forth movement of the tympanic membrane which moves the stapes back and forth
- this causes displacement of fluid in the cochlea and induces vibration in the basilar membrane
A
Cochlea
21
Q
- contains about 30,000 fibers which project from the bony center of the cochlea, the modiolus
- fibers are stiff reed-like structures fixed to the modiolus and embedded in the loose basilar membrane
- because they are stiff and free at one end they can vibrate like a musical reed
- the length of the fibers increase and the diameter of the fibers decrease from base to the helicotrema, overall stiffness decreases 100 X, high freq. resonance occurs near base, low near apex
A
Basement Membrane
22
Q
Displacement of fluid in the cochlea depends on the frequency
A
High frequency - will displace fluid at the base
Middle frequency - will displace fluid in the middle
Lower frequency - will displaced fluid towards the end near the helicotrema
23
Q
2 Types of Fluid inside the Cochlea
A
- Endolymph - fluid in the middle; near the organ of Corti
* Perilymph - fluid inside the scala vestibuli and scala tympani
24
Q
- similar to CSF (high sodium, low potassium)
* Voltage: 0 mV
A
Perilymph
25
* similar to ICF (low sodium, high potassium)
| * Voltage: +80 mV
Endolymph
26
* receptor organ that generates nerve impulses
* lies on the surface of the basilar membrane, contains rows of cells with stereocilia called hair cells
* the tectorial membrane lies above the stereocilia of the hair cells
* movement of the basilar membrane causes the stereocilia of the hair cells to shear back and forth against the tectorial membrane
Organ of Corti
27
Sensory Transduction of Sound
1. Hair cell depolarization
2. Voltage-gated Ca+ channels open
3. Release of neurotransmitter (glutamate/aspartate?)
4. Generation of action potentials in the afferent cochlear nerve fibers
28
Nerve Impulse Origination
• The stereocilia, when bent in one direction cause the hair cells to depolarize, and when bent in the opposite direction hyperpolarize.
- this is what begins the neural transduction of the auditory signal
• Auditory signals are transmitted by the inner hair cells.
- 3-4 X as many outer hair cells than inner hair cells
- outer hair cells may control the sensitivity of the inner hair cells for different sound pitches
29
Determination of Sound Frequency and Amplitude
• Place principle determines the frequency of sound perceived.
- Different frequencies of sound will cause the basilar membrane to oscillate at different positions.
- Position along the basilar membrane where hair cells are being stimulated determines the pitch of the sound being perceived.
• Amplitude is determined by how much the basilar membrane is displaced.
30
Central Auditory Pathway
fibers enter dorsal and ventral cochlear nuclei of the medulla —> 2nd order neurons project through trapezoid body to the contralateral superior olivary nucleus —> some fibers pass through the ipsilateral olivary nucleus —> from superior olivary nucleus to via lateral lemniscus —> from inferior colliculus to medial geniculate —> from medial geniculate to auditory cortex
31
Determining the Direction of Sound
* superior olivary nucleus divided into lateral and medial nuclei
* LATERAL NUCLEI detects direction by the difference in sound intensities between the 2 ears
* MEDIAL NUCLEI detects direction by the time lag between acoustic signals entering the ears
32
Deafness
* nerve deafness - impairment of the cochlea or the auditory nerve
* conduction deafness - impairment of tympanic membrane or ossicles
33
Functions of the Vestibular System
* Maintains of posture and equilibrium
| * Fixation of the visual horizon during rapid head movements
34
Maintaining Balance
• The vestibular system determines the position and motion of your head in space.
35
There are two components to monitoring motion:
1. Detecting rotation
- what happens when you shake or nod your head.
- This is called angular acceleration.
2. Detecting motion along a line
- what happens when the elevator drops beneath you or when your body begins to lean to one side
- This is called linear acceleration.
36
Vestibular System: Function
• Detects angular and linear acceleration
- Important in maintaining balance, posture, and vision
• Connections with brainstem, cerebellum, and somatic sensory cortices to provide info about the motions and position of the head and body
37
Elements of the Vestibular Labyrinth
* Continuous with the cochlea
* Three semicircular canals - Detect angular acceleration
* Two otolith organs:
- Utricle and saccule
- Detect linear acceleration
• Vestibular nerve fibers
- synapse with hair cells
- have cell bodies in Scarpa's ganglion
38
Semicircular canals: Structure
• each semicircular canal contains an ampulla
- Contains hair cells embedded in sensory epithelium called crista ampullaris
- Cilia of hair cells project into gelatinous cap called cupula (sensitive to the movement of the fluid)
39
Semicircular canals: Function
♦ Specialized for responding to rotational acceleration of the head
- Head rotation results in intertial movement of endolymph in opposite direction
♦ Bends cupula which bends hair cells
- Same mechanical/electrical coupling as in auditory hair cells
♦ Excites/suppresses release of NTs from hair cells depending on direction of movement
40
Semicircular canals: Function 2
♦ Stereocilia maintain directionality on both sides of the head
- Bending towards kinocilium >> opens mechanically gated cation channels >> K+ influx
>> depolarization
- Bending away from kinocilium >> closes channels that are open during resting state >> hyperpolarization
♦ Paired canals work together to signal head movement
- With turning of the head, hair cells on one side of the body send excitatory signals to the brain while hair cells on the opposite side are inhibited
41
Otolith Organs: Structure
♦ Two otolith organs; utricle and saccule
- Each contains a sensory epithleium called the macula
* Horizontally oriented in utricle
* Vertically oriented in saccule
♦ cilia of hair cells embedded in gelatinous otolithic membrane
- Embedded on surface are calcium carbonate crystals called the otoliths
42
Otolith Organs: Function
• Specialized to respond to gravity and linear acceleration
- Otoliths have a higher density than endolymph
* Shift when angle of head changes
* Causes otolithic membrane to shift in same direction
* Cilia of certain hair cells deflected (Excites/suppresses release of NTs from hair cells depending on orientation of cilia)
43
Otolith Organs: Function
• kinocilia of each hair cell are oriented in different directions in relation to striola
- Utricle: towards striola
- Saccule: away from striola
• Same sensory transduction as semicircular canals
- Bending of cilia towards kinocilium depolarizes the hair cell
44
Vestibular Pathways
• vestibular afferents synapse on vestibular nuclei located in medulla and pons
45
Vestibular Nuclei integrate information from vestibular, visual, and somatic receptors and send collaterals to
1. Cerebellum - Sends corrective adjustments to motor cortex: maintenance of balance and posture
2. nuclei of cranial nerves - Control coupled movements of the eyes, maintain focus and visual field
3. nuclei of accessory nerves - Control head movement and assist with equilibrium
4. ventral posterior nucleus of thalamus and vestibular area in cerebral cortex (part of primary somatosensory cortex)
- Conscious awareness of the position and movement of head
46
• Senses falling/tipping (contracts limb muscles for postural support )
Vestibulospinal Reflexes
47
• acts on the neck musculature to stabilize the head if body moves
Vestibulocollic Reflexes
48
• stabilizes visual image during head movement (causes eyes to move simultaneously in the opposite direction and in equal magnitude to head movement)
Vestibulo-ocular Reflexes
49
Vestibulo-Ocular Reflex (VOR)
Example: head movement to the LEFT
1. inertia of endolymph movement to the right in horizontal vestibular canals causes:
a) increased firing of left vestibular afferent
b) decreased firing of right vestibular afferent
2. Excitatory connections with contralateral abducens nuclei (lateral rectus) and inhibitory connections to ispilateral side
3. Excitatory connection to inhibitory interneuron in contralateral vestibular nuclei
4. Movement of the eyes to the right
50
Core Temperature vs Skin Temperature
• Core temperature
- More constant
- Temperature of internal organs
• Skin temperature
- Affected by temperature of environment
- Surface temperature of the body
51
What’s in between the core and skin temperature?
• We have insulators present in our body in the form of Fats (subcutaneous tissue)
52
How does heat transfer occur from the core of the body to the skin?
• Through blood flow
53
• important way of heat production; kahit na nakaupo ka lang dyan you are still generating heat
Basal Metabolic Rate
54
Extra metabolism secondary to:
* Muscle activity
* Thyroxine (also GH, Testosterone)
* Sympathetic stimulation of cells
* Increased chemical activity of cell
* Thermogenic effect of food
55
HEAT LOSS
* Radiation (60%)
* Conduction (objects: 3%; air: 15%)
* Convection - conduction to air; air current should be present
* Evaporation (22%) eg insensible water loss(we cannot control it)
56
* Stimulation of the ANTERIOR hypothalamus-preoptic area (thermoregulator center) —> activates sympathetic response —> stimulation of sweat glands
* In lower animals, surface is covered with fur and with no sweat glands, they release excess heat through PANTING mechanism
* Neurotransmitter: Acetylcholine
SWEATING
57
REGULATION OF BODY TEMPERATURE (Peripheral Temperature sensors)
• Skin sensory receptors
- Detects body surface temperature
• Deep body temperature receptors
- Located in the spinal cord, abdominal viscera, around great veins
- Detects core body temperature
* cold receptors > warmth receptors
58
REGULATION OF BODY TEMPERATURE (Central Temperature sensor)
Anterior Hypothalamic - Preoptic Area
59
• integrates the Central and Peripheral Temperature Sensory Signals and determines if body needs heat generating or heat losing mechanism
Posterior Hypothalamic
60
Detected Temperature compared with Set-point Temperature
• Detected Temp Set-Point Temperature: Initiate Heat Loss Mechanisms
61
Heat-Generating Mechanisms when the Body is Too COLD
* Vasoconstriction (PHSC stimulation)
* Piloerection
* Increase in thermogenesis
* Shivering
* Decrease sweating
62
Heat-Losing Mechanisms when the Body is Too HOT
* Vasodilation of skin blood vessels (PSHC [Posterior Hypothalamic Sympathetic Center] inhibition) - increase in diameter of blood vessel causing increase in blood flow thereby more heat release to the skin
* Sweating (1 deg C increase)
* Decrease in heat production
63
(Thermogenesis)
| Shivering
* Shivering center- dorsomedial portion of posterior hypothalamus
* Maximum shivering can increase heat production to 4-5x normal
64
(Thermogenesis)
| Sympathetic chemical excitation
* Epinephrine and Norepinephrin can increase rate of cellular metabolism
* Chemical thermogenesis is affected by amount of brown fat
65
(Thermogenesis)
| Thyroxine effect
• Increase in rate of cellular metabolism
66
What is the role of fat and skin in terms of regulation of body temperature?
• Fat is the insulator and the skin is the radiator system
67
• More powerful system of body temperature control
Behavioral Control of Body Temperature
68
* Secondary to pyrogens increase >> prostaglandins >> increases set point temperature
* May also be secondary to brain lesions
Fever
69
• Increased set point temperature makes the brain think that the body is cold despite presence of fever
Chills
70
* Tissue damage secondary to excessive heat
| * you may have dizziness, loss of consciousness
Heatstroke
71
* May cause frostbite (common in digits and ears)
| * Can be used for preserving body organs
Exposure to cold
72
AT DIFFERENT ALTITUDES… (1)
• Alveolar PO2 decreases as altitude increases
- Carbon dioxide and water vapor dilutes oxygen in the alveoli
• Arterial oxygen saturation decreases as altitude increases
- Depends if you are breathing air or breathing pure oxygen
- When breathing pure oxygen, most of the space in the alveoli formerly occupied by nitrogen becomes occupied by oxygen
73
AT DIFFERENT ALTITUDES… (2)
• Unacclimatized person usually can remain conscious until O2 saturation falls to 50%
- When breathing air, the ceiling is 23 000 feet
- When breathing pure oxygen, the ceiling is about 47 000 ft
74
* Most Important Effect of high altitude
| * judgment, memory, motor movements are affected
Decreased Mental Proficiency
75
Effect of High Altitude (At 12,000 Feet)
- Drowsiness
- Lassitude
- Mental and muscle fatigue
- Headache
- Nausea
- Euphoria
76
Effect of High Altitude (At 18,000 feet and 23,000 Feet)
At 18,000 feet : twitchings/seizures
At 23,000 feet: coma and death after
77
MECHANISMS FOR ACCLIMATIZATION TO LOW PO2
* Increased Pulmonary Ventilation
* Polycythemia
* Increase Diffusing Capacity of Oxygen
* Increased Vascularity of the Peripheral Tissue
* Increased Ability of Cells to Use Oxygen Despite Low PO2
78
Increased Pulmonary Ventilation
* After a few minutes at high altitudes à respiratory rate increases by 1.65x
* After a few days —> respiratory rate increases by 5x
* Respiratory alkalosis develops—> renal compensation occurs to bring plasma pH back to normal
79
* Hematocrit, Blood Volume and HgB increases
| * Increases the enzyme BPG mutase which increases 2,3 BPG (Shift to the Right of the O2-HgB Dissociation Curve)
Polycythemia
80
Increased Diffusing Capacity Of Oxygen
```
• Up to 3x the normal
• Mechanisms
- Increased pulmonary capillary blood volume
- Increased lung volume
- Increased pulmonary arterial BP
```
81
Increased Vascularity Of The Peripheral Tissues
* Cardiac Output increases by 30% immediately but tapers off after Hct increases
* Growth of increased numbers of systemic circulatory capillaries in the nonpulmonary tissues
82
Increased Ability Of Cells To Use Oxygen Despite Low PO2
• Increased cell mitochondria and cellular oxidative enzymes
83
What are the changes seen in natural acclimatization?
* Decreased Body Mass, Increased Chest Size
* Larger Hearts and Lungs
* Better O2 delivery (increased HgB, better O2 utilization)
84
What are the manifestations of acute mountain sickness?
• Acute Cerebral Edema
hypoxia -> cerebral vasodilation -> fluid leakage in the blood vessel -> edema
• Acute Pulmonary Edema
hypoxia -> pulmonary vasoconstriction (not all vessels constrict) -> increased capillary pressure in unconstricted vessels -> fluids are pushed outside -> edema
85
What are the manifestations of chronic mountain sickness?
• Pulmonary Vasoconstriction leading to R-sided heart failure
- increase pressure in lungs will lead to pulmonary HTN causing increase pressure in the right ventricle there by causing Right sided heart failure
86
Body in sitting position in an airplane is subject to
* Linear Acceleration
| * Centrifugal Acceleration
87
* a unit of force equal to the force exerted by gravity
| * used to indicate the force to which a body is subjected when it is accelerated
G Force
88
* Pilot pushed against his seat
* More dangerous
* Blood shunted to the Lower Extremities
* +6 to +10G -> blackouts, LOC, death
* +20G -> Vertebral Fracture
Positive G
89
```
• Pilot pushed against his seatbelt
• Less dangerous
• Blood shunted to the Head
*May result in “red-out” of the eyes and transient psychotic disturbances
• -20G -> death
```
Negative G
90
* the constant speed that a freely falling object eventually reaches when the resistance of the medium through which it is falling prevents further acceleration
* A skydiver would reach terminal velocity due to air resistance in 12 seconds, with a speed of 175 feet per second
Terminal Velocity
91
Use of a Parachute
• Opening shock load of 1200 lbs maybe felt
• Reduces speed of skydiver to 1/9th the terminal velocity
- Equivalent to speed of jumping from a height of 6 feet
- Fall to the ground with kneed bent, muscles taut to prevent fractures
92
SPACE
• Earlier Space Missions: 100% pure oxygen at 260mmHg
- Prone to fires
- Astronauts prone to small patches of lung atelectasis when mucus plugs are present
* Currently: 20% Oxygen at 760mmHg
* For space travel lasting months to years, oxygen recycling system must be used
- Electrolysis of water
- Bringing algae
93
Weightlessness/Microgravity in Space
• Gravity is still present!
- Acts on astronauts and the space shuttle in the same direction, same time, same acceleration
• If acute, little effect
- Motion sickness
- Translocation of fluids
- Diminished physical activity
94
Weightlessness/Microgravity in Space (If chronic, “deconditioning” may occur)
* Decreased blood volume
* Decreased RBC
* Decreased muscle strength
* Decreased maximum cardiac output
* Loss of calcium and phosphate from bones
95
Deep Sea Diving
• To keep the lungs from collapsing due to high water pressure, air used by divers are given in high pressures
- May lead to toxicities from high nitrogen, oxygen and carbon dioxide pressures
96
• nitrogen dissolves in fatty substances in neuronal membranes causing altered ionic conductance through membranes
HIGH NITROGEN PRESSURE
97
Effects of High Nitrogen Pressure:
* At 120 Feet: Joviality, loss of cares
* At 200-250 Feet: drowsiness
* Beyond 250 Feet: “raptures of the depths”
98
* Alveolar PO2 -> excess O2 will be buffered in the blood -> maintain PO2 pressure in tissues at 40mmhg -> does not affect tissues
* But if more excess -> cannot be buffered oxygen toxicities
* Breathing oxygen at 4atm (PO2=3040mmHg) will cause sudden brain seizures followed by coma [Due to Oxygen Free Radicals (O2- and H2O2)]
HIGH OXYGEN PRESSURE
99
* Happens only if diving apparatus has a malfunction
| * Severe respiratory acidosis, lethargy, narcosis
HIGH CARBON DIOXIDE PRESSURE
100
• Sudden ascent can lead to formation of nitrogen bubbles -> blocks blood vessels -> signs and symptoms
Decompression sickness
101
Decompression sickness: Manifestations
* “Bends” (Pain in the joints and muscles)
* “Chokes” (Dyspnea)
* Caisson’s Disease (Chronic Decompression Sickness
102
Decompression sickness: Treatment
• US Navy Decompression Tables
• Tank Decompression
• Use helium in very deep dives (>250 feet)
*Advantages of helium over nitrogen:
- 1/5 narcotic effect of nitrogen
- Less dissolved in body tissues and does not diffuse rapidly upon decompression
- Lower density
103
Decompression schedule for a diver who has been on the sea bottom for 60minutes at a depth of 190 feet:
* 10 minutes at 50 feet depth
* 17 minutes at 40 feet depth
* 19 minutes at 30 feet depth
* 50 minutes at 20 feet depth
* 84 minutes at 10 feet depth
104
SCUBA (Self-Contained Underwater Breathing Apparatus): Components
1. Compressed air tanks
2. Reducing valve
3. Inhalation demand valve and exhalation valve
4. Mask and tube system
105
Most important problem in use of SCUBA?
Limited amount of time one can remain beneath sea surface
106
```
• Escape from submarine at 300 feet possible,
• if with scuba, 600 feet
• prone to pulmonary gas embolism
• Hazards in internal environment:
- Radiation in atomic submarines
- Poisonous gases
```
SUBMARINE
107
• due to oxidizing properties used to treat gas gangrene, decompression sickness, arterial gas embolism, CO poisoning, osteomyelitis and MI
Hyperbaric oxygen therapy
108
OVERALL STRENGTH: MORE
STRENGTH PER SQUARE CENTIMETER OF X-SEC AREA : 3-4 KG/CM2
WORLD RECORDS : MARATHON
EFFECT OF HORMONES: TESTOSTERONE -> MORE MUSCLE
MEN
109
OVERALL STRENGTH: LESS
STRENGTH PER SQUARE CENTIMETER OF X-SEC AREA: 3-4 KG/CM2
WORLD RECORDS: LONG-DISTANCE SWIMMING
EFFECT OF HORMONES: ESTROGEN -> MORE FAT
WOMEN
110
What is the basis for muscle endurance?
Glycogen levels in the body
111
What is the best diet for muscle glycogen recovery?
High Carbohydrate Diet
112
How long does it take to recover muscle glycogen?
2 Days (High Carbohydrate Diet)
113
An increase in muscle strength is always due to what?
Increase in muscle size
114
Notes: Cell ATP, cell phosphocreatine
Onset and Duration: First 8-10 seconds
Example: 100m dash, jumping, diving
Phosphagen energy system
115
Notes: Anaerobic; reconstitute atp & phosphocreatine
Onset and Duration: For 1.3 to 1.6 minutes after phosphagen system used up
Example: Tennis, soccer
Glycogen-lactic acid system
116
Notes: Aerobic; reconstitute atp, phosphocreatine, glycogen-lactic acid cycle
Onset and Duration: For unlimited time as long as with energy supply (glycogen, fat, ketones, amino acids. Fats supply 50% energy requirements after 3-4 hours) after glycogen-lactic acid system used up
Example: Long-distance jogging
Aerobic system
117
EFFECT OF ATHLETIC TRAINING ON MUSCLES AND MUSCLE PERFORMANCE: Muscle Hypertrophy*
1. increased numbers of myofibrils, proportionate to the degree of hypertrophy;
2. 120 percent increase in mitochondrial enzymes;
3. 60 to 80 percent increase in the components of the phosphagen metabolic system
4. 50 percent increase in stored glycogen
5. 75 to 100 percent increase in stored triglyceride
118
Respiratory System in Exercise
• Maximal breathing capacity: 150-170L/min
• Pulmonary ventilation during maximal exercise: 100-110L/min
• Difference (50L/min) is used to compensate for:
- Exercise at high altitude
- Exercise under hot conditions
- Abnormalities of the respiratory sytem
119
Cardiovascular Effects of Exercise
* Muscle blood flow increases up to 20x during the most strenous exercise
* Cardiac Output also increases during exercise
- Athletes: 30L/min (Resting CO: 5L/min)
- Non-athletes: 20L/min (Resting CO: 5L/min)
• At Maximal Exercise
- CO is at 90% of its maximum
- Pulmonary ventilation is at 65% of its maximum
- Cardiovascular system: most limiting factor in delivery of oxygen to muscles during maximal muscle aerobic metabolism
120
Body Heat in Exercise
• Only 25% of nutrient energy is converted to muscle work
- Rest is released as Heat
• Heatstroke
- When T > 42 deg Celcius during exercise
- May damage neurons including temperature-regulating centers
- Doubles the rate of all intracellular reactions further compounding the problem
- Tx: remove clothing, sponge/spray with water, fan, give fluids
121
Body Fluids and Salts in Exercise
• 10 lbs of body weight (mainly water) maybe lost in one hour of athletic event
- May lead to muscle cramps, nausea, etc.
• Sodium and potassium lost with sweat
• Sweat glands may acclimatize to hot and humid conditions because of Aldosterone
122
Drugs and Athletes
* Caffeine: inconsistent results on effects on athletic performance
* Testosterone: increases muscle strength and aggressiveness; May also cause M.I. and strokes due to Hypertension, inc LDL, dec HDL
* Amphetamines and Cocaine: psychological effects only; may cause VFib
123
BODY FITNESS PROLONGS LIFE
• Mortality is 3x less in most fit people than in least fit people
• 2 evident reasons:
- Body fitness and weight control reduce cardiovascular disease
- Athletically fit people has more body reserves when he/she becomes sick
124
What is the Primary Organ of taste?
Tongue - Taste Buds
125
Colds and taste perception. Why?
* Taste is 80% smell
| * Texture and Temperature of food from Trigeminal nerve (CN V)
126
Primary Sensations of Taste
1. Sour
2. Salty
3. Sweet
4. Bitter
5. Umami
127
* Caused by ACIDS
* H+
* Hydrochloric Acid
* Hydrogen Ion concentration
* Intensity of taste is proportional to the logarithm of the hydrogen ion concentration
SOUR
128
* Caused by IONIZED SALTS
* Na+ (sodium ion concentration)
* Soduim Chloride
* Anions of salt also contribute to a lesser extent
SALTY
129
* Not caused by any single class of chemicals
* Caused by SUCROSE, sugars, glycols, alcohols, aldehydes, ketones, amides, esters, some amino acids, some small proteins, sulfonic acids, halogenated acids, and inorganic salts of lead and beryllium.
* Mostly ORGANIC CHEMICALS
SWEET
130
What substance first taste SWEET but has a BITTER aftertaste?
Saccharin - has a bitter aftertaste (dark chocolates has saccharin)
131
* Not caused by any single type of chemical agent
* Almost entirely ORGANIC SUBSTANCES
* QUININE
* Protection against POISONS or DEADLY TOXINS (alkaloids)
* *Rejection of the Food
BITTER
132
2 Substances likely to cause bitter sensation:
1. long -chain organic substances that contain Nitrogen
| 2. alkaloids
133
* Japanese word meaning “delicious”
* Usually foods containing L-glutamate
* Exact molecular mechanism: UNKNOWN
* Meat extracts, aging cheese
UMAMI
134
Threshold for Taste
SOUR: 0.0009N
SALT: 0.01M
SWEET: 0.01M
BITTER: 0.000008M
135
Bitter taste, more sensitive than the others. Why?
It has a protective function against dangerous toxins
136
Other taste factors
* Pain –pepper, mustard, ginger
* Cold receptors –Menthol, mint
* Heat receptors –Pepper
137
Hot vs Cold
* Hot food have stronger taste than Cold food
| * Molecules move faster and dissolve faster hence stronger taste
138
* Occurs in 15-30% of the population
* Reduction in sensitivity (Tt)
* Inability to taste different types of thiourea (CH4N2S) compounds
* Usually an autosomal recessive trait (tt)
Taste Blindness
139
* PTC is often used
* Phenylthiocarbamide
* You have two bags of test paper: Control Paper and PTC Paper
* Touch one of the paper strips from the bag labeled "Control Paper" to the tip of your tongue
* Touch one of the paper strips from the bag labeled "PTC Taste Paper" to the tip of your tongue
* Both papers just taste like paper = Non-Taster for PTC. If one tastes bitter and the other tastes like paper, you are a Taster.
Taste test
140
```
- Found on the:
• Papillae (Circumvallate, Fungiform, Foliate)
• Palate
• Tonsillar pillars
• Epiglottis
• Proximal Esophagus
```
Taste Bud
141
* found on the Walls of the troughs
* forms a V on the posterior surface of the tongue
* Usually 8-12 large papillae
* Bitter and sour
Circumvallate papillae/ Vallate
142
* Concentrated over the flat Anterior surface of the tongue
* MOST ABUNDANT Scattered among filiform papillae
* Mushroom-shaped
* Sweet and Salty
Fungiform papillae
143
* Both lateral surface of the tongue
| * 4-5 fold
Foliate papillae
144
Taste Bud vary according to age
• Adults have 3,000 to 10,000 taste buds
• Children have more taste buds = more sensitive!
• >45 years taste buds begin to degenerate thus
- Decrease in taste sensitivity
145
Taste Bud
• One taste bud = One primary taste
- When in low concentration
• One taste bud = Two or more primary taste
- At high concentration
146
Stimulation of Taste Buds
• Lock and key system
• Tongue -> Papillae -> Taste buds (stimulated)
-> Taste cell -> depolarization -> impulse -> relayed to CNS
147
How is the stimulus removed?
Washed away by Saliva
148
REMEMBER (Gustatory)
* The type of receptor protein in each taste villus determines the type of taste which will be perceived.
* ION CHANNELS - Na, H+ (salty, sour)
* SECONDARY MESSENGER - Sucrose, quinine (sweet, bitter)
149
Nerve impulse (Gustation)
• Stimulus (within fraction of a second) ->Peak discharge from nerve fibers -> Adapts (within seconds) -> Weaker/Lower continuous signal
(as long as there is stimulus)
150
Transmission to CNS (Anterior Tongue)
• Anterior 2/3 tongue -> lingual nerve -> chorda tympani -> Facial Nerve (CNVII) -> Tractus Solitarus (NTS) -> VPM(thalamus) -> lower tip of the postcentral gyrus (parietal cortex) -> sylvian fissure -> opercular insular area
151
Transmission to CNS (Circumvallate papillae, Posterior mouth and Throat)
• Circumvallate papillae, Posterior mouth and Throat -> Glossopharyngeal nerve (CN IX) -> Tractus Solitarus (NTS) -> VPM -> lower tip of the postcentral gyrus) -> sylvian fissure -> opercular insular area
152
Transmission to CNS (Base of the tongue, epiglottis)
• Base of the tongue, epiglottis -> Vagus nerve ->Tractus Solitarus (NTS) -> VPM -> lower tip of the postcentral gyrus -> sylvian fissure -> opercular insular area
153
Transmission to CNS (From NTS)
• From the NTS divides into -> Superior salivatory nucleus and Inferior salivatory nucleus
then activates the -->>Submandibular, Sublingual and Parotid glands
154
* Choosing certain types of food over the other
* Helps control the diet he eats
* Usually changes in accordance to body’s needs
* Previous experience with unpleasant or pleasant taste plays a key factor
* Taste AVERSION: negative taste preference
Taste Preference
155
Experiments (TASTE):
1. Adrenalecomized, salt-depleted animals automatically select drinking water with high concentration of NaCl in preference to pure water
2. Animal given injections of insulin choses sweetest food among many samples
3. Calcium depleted parathyroidectomized animals choose water with high calcium chloride
156
* Least understood of our senses
* Subjective phenomenon
* Cannot be studied with ease in lower animals
* Smell is poorly developed in humans vs lower animals
* Pregnant women and young adults have higher sense of smell
* Olfactory receptors are the only sense that is not routed through the CNS
* Suggests that smell is more important than other senses
OLFACTION
157
* Located at the -Superior part of each nostril
* Medially: downward along the surface of the superior septum
* Laterally: folds over superior turbinate, upper surface of middle turbinate
* 2.4sq m per nostril
Olfactory Membrane
158
Olfactory Cells
• Receptor cells for smell sensation
• Bipolar nerve cells (derived originally from CNS)
- Each olfactory receptor is a neuron
• 100M olfactory cells (OC) in the olfactory epithelium
• Interspersed among sustentacular cell
• Ends of OC forms a knob from which 4 to 25 Olfactory Hairs (olfactory Cilia) project into the olfactory membrane
- Olfactory mucosa is the place in the body where NS is closest to the external world
• Interspersed among Bowman’s gland in the olfactory membrane
• The Olfactory portion of the brain were among the first brain structures developed in primitive animals, and much of the remainder of the brain developed around these olfactory beginnings.
• Limbic system –part of the brain that originally subserved olfaction
159
• reacts to odors in the air and stimulate olfactory cells, upper portion of nasal passages –contain the receptors
Olfactory cilia
160
• secrete mucus onto olfactory membrane
Bowman’s gland
161
* lies over the cribriform plate
| * one bulb has several thousand Glomeruli
Olfactory bulb
162
* separates the brain cavity form the upper nasal cavity
| * has several perforations through which nerves pass upwards to reach the olfactory bulb
Cribriform plate
163
* glomerular structure in olfactory bulb where short axons from olfactory cells terminate
* one bulb usually terminal for 25,000 axons from olfactory cells
* also the terminus for dendrites from ~25 large mitral cells and ~60small tufted cells
* different glomeruli different odor
Glomeruli
164
Olfactory Signal Transduction
1. Odorant binds to its receptor
2. Receptor activates G protein
3. G protein activates adenyl cyclase
4. cAMP opens a cation channel, allowing Sodium and Calcium influx causing depolarization
165
Importance of Olfactory Stimulation
* Multiplies even the weakest odorant
* Only volatile substances can be sniffed into the nostrils can be smelled
* Stimulating substance must be at least slightly water soluble so that it can pass through the mucus into the cilia
* Helpful if substance is slightly lipid soluble
166
Membrane potential
• Membrane potential of Unstimulated Olfactory cells = -55 millivolts
- Slow action potentials at 1 every 20 seconds; 2-3 per second
• Membrane potential of Stimulated Olfactory cells = -30 millivolts or less (can be positive)
- Action potential of 20-30 per second
167
• Olfactory receptors adapt 50% in the first second after stimulation
• After that they adapt Very little and Very Slowly
• Adapt almost to EXTINCTION within minutes
- Psychological adaptation
Rapid adaptation of olfactory sensations
168
3 Reasons for Rapid Adaptation
1. The Granule cell
- specialized inhibitory cell in the olfactory bulb
- from which a large number of centrifugal nerve fibers terminate on
2. Feedback inhibition by the CNS
- After a strong stimulus the CNS suppress the smell signals through the olfactory bulb
3. Odor receptors
- 1000 different types or more
169
7 odor system
1. Camphoraceous
2. Musky
3. Floral
4. Pepperminty
5. Ethereal
6. Pungent
7. Putrid
170
• Lack of the appropriate receptor protein in olfactory cells for that particular substance
Odor Blindness
171
Affective Nature of Smell
* Pleasant
* Unpleasant
* Previous experience affects sense of smell
172
* Organ is not well developed in humans
* Very well developed in rodents
* This organ is concerned with perception of odors that act as pheromones
Vemeronasal organ
173
Threshold for smell
* Methylmercaptan – can be smelled when only one 25 trillionth of a gram is present in each mililiter of air. (low threshold)
* Mixed with natural gas to give an odor to be detected in case of gas leaks
* Humans can recognize more than 10,000 different odors but determination of intensity is poor
* Smell is concerned more with the presence or absence of odors rather than with quantitative detection of their intensities
174
Role of Pain Fibers in the Nose
* Many trigeminal pain fibers are found in olfactory membrane
* They are stimulated by irritating substances
* Are responsible for initiating sneezing, lacrimation and other reflex responses.
175
• enters the brain at the anterior junction between the mesencephalon and cerebrum
• Divides into:
- Medial olfactory area
- Lateral olfactory area
Olfactory tract
176
* The Very Old Olfactory System
* Subserves basic olfactory reflexes
* Consists of a group of nuclei located at the midbasal portion of the brain immediately anterior to the hypothalamus and other primitive portions of the brain’s limbic system
* Concerned with basic behavior.
Medial Olfactory area
177
* The Less old olfactory system
* Composed of prepyriform and pyriform cortex plus the cortical portion of the amygdaloid nuclei.
* Some signal pathways from LOA also feed into the Paleocortex (anteromedial portion of the temporal lobe)
* Only area in the entire cerebral cortex where sensory signals pass directly to the cortex without passing first through the thalamus.
* Has many connections to the limbic system!
* Its connection with the hippocampus is important in learning to like or dislike certain foods.
* Automatic but partially learned control of food intake and aversion to toxic and unhealthy foods
* Odor memory
Lateral Olfactory Area
178
Removal of lateral olfactory areas in animals:
* did not affect more primitive responses to olfaction such as licking of the lips, salivation and other feeding responses caused by the smell of food or primary emotional drives associated with smell
* Abolishes more complicated olfactory conditioned reflexes
179
The Newer Pathway
* Helps in the conscious analysis of odor (studies in monkeys)
* Passing through the Thalamus -> dorsomedial thalamic nucleus -> lateroposterior quadrant of the orbitofrontale cortex
* Comparable to other cortical systems
* Used for conscious perception and analysis of olfaction
180
Centrifugal Control of Activity in the Olfactory Bulb by the CNS
* Brain to the olfactory tract to the olfactory bulb. Hence OUTWARD direction.
* i.e. CENTRIFUGALLY from the brain to the periphery
* These tracts terminate on granule cells located among mitral and tufted cells in the olfactory bulb.
* Granule cells send inhibitory signals to Tufted and Mitral cells.
181
Neonatal Physiology
* Switch from intrauterine life to extrauterine life
* “Immaturity” of systems
* Higher metabolic needs (anabolism)
* Rapid period of growth and development
182
At Birth...
* Loss of placental support
* Needs own source of nourishment
* Changes in respiratory function
183
Onset of Breathing
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• Begins to breathe within seconds
• Normal respiratory rate within 1 min
• Initiated by sudden exposure to the outside world:
- Slightly asphyxiated state
- Cooled skin
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184
Delayed or abnormal breathing at birth (Risk for Hypoxia)
• Causes: 1) Umbilical cord compression, 2) Premature separation of the placenta, 3) Excessive contraction of the uterus, 4) Excessive anesthesia
Hypoxia
• Can be tolerated by the neonate up to 10 minutes
• 4 minutes ONLY in the adult
• Permanent brain damage may occur after at least 8 minutes
185
Expansion of lungs at birth
• Need to overcome the surface tension from the viscid fluid that fills the lungs
186
Changes in Fetal Circulation After Birth
* Closure of the Foramen Ovale (right to left atrium)
* Closure of the Ductus Arteriosus (connection between aortic arch)
* Closure of the Ductus Venosus (at the liver)
187
Neonatal Nutrition
* Blood glucose concentration frequently falls the first day = 30 to 40 mg/dl of plasma (less than half the normal value)
* Has stored fats and proteins for metabolism until mother's milk can be provided 2 to 3 days later
* Special problems: adequate fluid supply to the neonate because the infant's rate of body fluid turnover averages seven times that of an adult, and the mother's milk supply requires several days to develop.
* Physiologic weight loss = decrease of 5 -10 % (as much as 20%) within the first 2 to 3 days of life due to fluid loss
188
Special Functional Problems in the Neonate
| Due to:
* Instability of various hormonal and neurogenic control systems
* Immaturity of the organ systems
* Ongoing adjustments to extrauterine life
189
Respiratory System (Neonates)
* Normal Respiratory Rate = 40 breaths per minute
* Tidal Volume = 16 mL
* Total Minute Respiratory Volume = 640 ml/min, (about twice as great in relation to the body weight as that of an adult)
* The functional residual capacity of the infant's lungs is only one-half that of an adult in relation to body weight
* Causes excessive cyclical increases and decreases in the newborn baby's blood gas concentrations if the respiratory rate becomes slowed because it is the residual air in the lungs that smoothes out the blood gas variations
190
Circulatory System (Neonates)
• Blood Volume = about 300 mL
• Additional 75mL if the infant is left attached to the placenta for a few minutes after birth or if the umbilical cord is milked (RBCs are valuable to the neonate)
• Next few hours, fluid is lost into the neonate's tissue spaces
- increased hematocrit
- eventually returns to the normal value of about 300 milliliters
191
Circulatory System (Neonates) 2
* Cardiac output = averages 500 ml/min (twice as much in relation to body weight as in the adult)
* Arterial Pressure
- First day after birth: ave. 70/50 mmHg
- Increases slowly during the next several months to about 90/60
- Much slower rise during the subsequent years until the adult pressure of 115/70 is attained at adolescence
192
Blood Characteristics (Neonates)
* RBC count = 4M per cubic millimeter
* If blood is stripped from the cord into the infant, RBC count increases to 0.5-0.75 million during the first few hours of life
* Few new RBCs are formed in the infant during the first few weeks of life, presumably because the hypoxic stimulus of fetal life is no longer present to stimulate red cell production.
* Physiology Anemia = at 6-8 weeks of age, less than 4 M per cubic millimeter ; returns to normal within 2-3 mos.
* WBC count = 45,000 per cubic millimeter, which is about five times as great as that of the normal adult
193
Liver Function in the Neonate
* Liver functions poorly in the first week of life
* Incapable of conjugating bilirubin with glucuronic acid for excretion in the bile
* Conjugates bilirubin with glucuronic acid poorly and therefore excretes bilirubin only slightly during the first few days of life
* Deficient in forming plasma proteins (15 – 20% less than that for older children); may develop hypoproteinemic edema
* Incapable of effective gluconeogenesis results in low glucose levels
* Forms too little of the blood factors needed for normal blood coagulation
194
Physiological Hyperbilirubinemia vs Pathologic Jaundice
* Physiological Hyperbilirubinemia - the plasma bilirubin concentration rises from a normal value of less than 1 mg/dl to an average of 5 mg/dl during the first 3 days of life and then gradually falls back to normal as the liver becomes functional.
* Associated with mild jaundice (yellowness) of the infant's skin and especially of the sclerae of its eyes for a week or two (physiologic jaundice)
* Vs. Pathologic Jaundice – appears within the 1st 24 hours of life
195
Fluid Balance, Acid-Base Balance, and Renal Function (Neonates)
* The rate of fluid intake and fluid excretion in the newborn infant is 7x as great in relation to weight as in the adult
* The rate of metabolism in the infant is 2x as great in relation to body mass as in the adult; tendency toward acidosis in the infant
* Functional development of the kidneys is not complete until the end of about the first month of life; can concentrate urine to only 1.5 times the osmolality of the plasma
* Most important problems of infancy: acidosis, dehydration, and, more rarely, overhydration
196
Digestion, Absorption, and Metabolism of Energy and Food (Neonates)
• Secretion of pancreatic amylase in the neonate is deficient
- The neonate uses starches less adequately than do older children
• Absorption of fats from the gastrointestinal tract is somewhat less than that in the older child
- Milk with a high fat content, such as cow's milk, is frequently inadequately absorbed
• The glucose concentration in the blood is unstable and low
197
Increased Metabolic Rate (Neonates)
- The normal metabolic rate of the neonate in relation to body weight is about twice that of the adult:
- =2x cardiac output
- = 2x minute respiratory volume in relation to body weight in the infant
198
Poor Body Temperature Regulation (Neonates)
- Results from large body surface area in relation to body mass
- Heat is readily lost from the body
- The body temperature of the neonate, particularly of premature infants, falls easily
199
Need for Calcium and Vitamin D (Neonates)
- Rapid ossification of its bones at birth needing a ready supply of calcium throughout infancy is necessary
- Ordinarily supplied adequately by the usual diet of milk
- GIT absorb calcium less effectively (especially preterm infants) than those of normal infants; needs Vitamin D to facilitate absorption
200
Necessity for Iron in the Diet (Neonates)
- May have stored enough iron to keep forming blood cells for 4 to 6 months after birth
- If the mother had anemia, severe anemia is likely to occur in the infant after about 3 months of life
- May feed infant with egg yolk or give iron supplement by the second or third month of life
201
Vitamin C Deficiency in Infants
- Ascorbic Acid: Required for proper formation of cartilage, bone, and other intercellular structures of the infant
- Not stored in significant quantities in the fetal tissues
- Little amount only found in milk (human milk > cow’s milk)
- Orange juice or other sources of ascorbic acid are often prescribed by the third week of life
202
Immunity (Neonates)
• Passive Immunity from the mother
(through the placenta and colostrum in milk)
- Can protect the infant for about 6 months against most major childhood infectious diseases, including diphtheria, measles, and polio
- Decrease of antibodies to less than half at age 1 month
- Gradual return of gamma globulin concentration to normal by the age of 12 to 20 months
203
Allergy (Neonates)
* The newborn infant is seldom subject to allergy
* May become sensitive several months later,
* May result in serious eczema, gastrointestinal abnormalities, and even anaphylaxis
* As the child grows older and still higher degrees of immunity develop, these allergic manifestations usually disappear
204
Endocrine Problems: Neonates (1)
• Ordinarily, the endocrine system of the infant is highly developed at birth
• Special cases occur due to the exposure of the child to hormones coming from the mother:
- A female child exposed to androgenic hormone or if an androgenic tumor develops in the mother during pregnancy: high degree of masculinization of her sexual organs (a type of hermaphroditism)
- May cause the neonate's breasts to form milk during the first days of life
205
Endocrine Problems: Neonates (2)
• Infants born to diabetic mothers
- Hypertrophy and hyperfunction of pancreatic islets leading to low blood glucose levels
- Macrosomal babies (large babies) born to Type II DM mothers
* The high levels of insulin are believed to stimulate fetal growth and contribute to increased birth weight
* Increased supply of glucose and other nutrients to the fetus may also contribute to increased fetal growth
- In the mother with uncontrolled type I diabetes (caused by lack of insulin secretion), fetal growth may be stunted because of metabolic deficits in the mother and growth and tissue maturation of the neonate are often impaired.
206
Endocrine Problems: Neonates (3)
• Hypofunctional adrenal cortices, often resulting from agenesis of the adrenal glands or exhaustion atrophy, which can occur when the adrenal glands have been vastly overstimulated.
• Infant born to a hyperthyroid mother is most likely to be temporarily hypothyroid; reverse is true
- In a fetus lacking thyroid hormone secretion, the bones grow poorly and there is mental retardation (cretinism)
207
Immature Development of the Premature Infant
Respiration
• FC And FRC are small in relation to size of infant
• Low FRC = Cheyne-strokes (breathing pattern)
• Decreased or absent surfactant = RDS (respiratory distress syndrome)
Gastrointestinal Function
• Poor absorption of fat
• Difficulty in absorbing Calcium
Function of other organs
• Immaturity of the Liver, Kidneys, bone marrow and lymphoid syste
208
Instability of the Homeostatic Control Systems in the Premature Infant
* Acid-base balance
* Protein concentration (hypoproteinemic edema)
* Calcium ion concentration
* Blood glucose concentration
209
Instability of Body temperature (Infants)
* Temperature approeaches that of surroundings
| * Temp below 96F (35.5C) is associated with high incidence of death
210
Oxygenation in Prematurity
* Excessive oxygenation may cause Blindness
* Increased Oxygen stops growth of new blood vessels in the retina
* Once oxygenation is stopped increased blood vessel formation up to vitreous humor blocking light from pupil to retina. These Blood vessels are replaced with fibrous tissue hence further contributing to blindness.
* Retrolental fibroplasia
211
Growth and Development of the Child
* Male and Female Same growth rate up to 10yrs
* 11-13y.o, female estrogen, growth spurt up to 14-16y.o
* 13-17y.o, male testosterone, growth spurt more delayed than females hence tend to be taller.
212
Behavioral Growth (Infant)
* Immature Nervous system (incompletely myelinated)
* Nervous system not fully functional at birth
* At birth infant Brain mass is only 26% of adult brain mass and 55% at 1 yr. Reaches adult proportion at 2 yrs.
213
• A process of gradual and spontaneous change, resulting in maturation through childhood, puberty, and young adulthood and then decline through middle and late age
Aging
214
• The process by which the capacity for cell division, growth, and function is lost over time, ultimately leading to an incompatibility with life
Senescence
215
Life Expectancies of Filipinos
* At birth, females: 73.24 years
| * At birth, males: 68.93 years
216
Maximum Life Potential
* The oldest age to which any human has ever lived
* The oldest fully authenticated age to which any human has ever lived is 122 years and 164 days, by Jeanne Louise Calment.
* She was born in France on February 21, 1875, and died at a nursing home in Arles, Southern France on
* August 4, 1997.
217
• Demonstrated by fibroblasts in vivo
• Fibroblasts will continue to divide until they are dense enough and come in contact with one another (Contact Inhibition)
• Explained by: Telomeres
- stretches of DNA at the end of chromosomes
- serve as handles by which chromosomes are moved during the telophase of meiosis.
- Irreversibly shortened each time a cell divides
- When the telomeres become too short, the cell can no longer divide
Hayflick’s Limit or Phenomenon
218
• Entropy-producing agents slowly disrupt cellular macromolecular constituents
- Free Radicals - modify macromolecules primarily through oxidation (oxidative damage)
- Glucose - nonenzymatic attachment to proteins and nucleic acids
Loose Cannon Theory
219
• Smaller mammals tend to have high metabolic rates and thus tend to die at an earlier age than larger mammals.
Rate of Living Theory
220
* A specific physiologic system--usually the neuroendocrine or immune system--is particularly vulnerable (presumably to entropic processes) during senescence.
* Failure of the weak system accelerates dysfunction of the whole organism.
Weak Link Theory
221
• Errors in DNA transcription or RNA translation eventually lead to genetic errors that promote senescence.
Error Catastrophe Theory
222
* One of the oldest theories of aging and no longer has high credibility
* Aging is under direct genetic control.
* It suggests that the rate of aging within each species has developed for the good of each species.
* Individual variation develops because of maladaption, exposure, and lifestyle.
* In the wild, such maladapted individuals tend to die out and the well-adapted ones persist, altering longevity in the best interest of the species.
Master Clock Theory
223
* Refers to the common complex of diseases and impairments that characterize many of the elderly.
* However, persons age very differently: some acquire diseases and impairments, and others seem to escape specific diseases altogether and are said to have died of old age. The latter may maintain an active healthy life until death.
Normal Aging
224
• Refers to a process by which deleterious effects are minimized, preserving function until senescence makes continued life impossible
Successful (Healthy) Aging
225
Changes in the Organ Systems (The Integumentary System: Skin Aging)
Intrinsic Aging vs Photoaging
Intrinsic Aging:
• subtle but important alterations of cutaneous function that are presumed to be due to time alone
Photoaging
• due to preventable chronic exposure to ultraviolet (UV) radiation superimposed on intrinsic aging
226
Functional changes characteristic of aged skin include declines in:
* cell replacement - barrier function
* wound healing
* immunologic responsiveness
* thermoregulation
227
Epidermis (Aging)
• Decreased epidermal turnover rates = 30-50%
• Decreased linear growth rates for hair and nails
• Consistent flattening of the epidermal-dermal junctions
- Compromises communication and nutrient transfer from the dermis to the epidermis
- Greater epidermal-dermal separation = skin prone to breaks
• Decline in Vitamin D production
228
Dermis (Aging)
* 20% Loss of dermal thickness
* 50% Loss of mast cells
* 30% Loss of venular cross-sectional area
Resulting in:
• Decreased inflammatory response
• 60% Decreased basal and peak cutaneous blood flow
- Pallor, decreased temperature, impaired thermoregulation
- Senescence of eccrine, apocrine and sebaceous glands
• Dysregulation of collagen synthesis and degradation
• Loss of elasticity
```
• Alteration of mucopolysaccharides
Resulting in:
- Fragmentation
- Impaired wound healing
- Loss of skin turgor
```
229
Subcutaneous Fat (Aging)
• Overall loss of volume of subcutaneous fat
Results in:
- Impaired thermoregulation
- Impaired cushioning; decreased ability to diffuse pressure over bony prominences = increased risk for sores, bruising
230
Appendages (Aging)
• Decreased density of cutaneous sensory end organs
Resulting in:
- Reduction in sensations of light touch, vibration, corneal sensitivity, two-point discrimination, and spatial acuity
- Increase in cutaneous pain threshold by about 20%
231
Changes in the Aging Skeletal System
* Wear and tear
* Thinning of cartilage pads between joints; less lubricating fluid
* Changes in the curvature of the spine
* More bone resorption than deposition
232
Muscular System: Sarcopenia (Aging)
* Decreased muscle bulk A decrease in muscle bulk is common and is not significant unless accompanied by a loss of function.
* Hand muscles are particularly affected; the interosseous and thenar muscles of the hands atrophy with age.
233
Changes in the cardiovascular system (Aging)
* Decreased heart rate (as low as 40bpm)
* Decrease in cardiac output
* Hardening of the arteries
* Increased pressure inside the blood vessels
* Immobilization and inactivity increases the risk of thrombosis
* More affected by gravitational and postural changes
234
Changes in the Nervous System: Senility is inevitable…myth or fact?
FACT:
• Not all elderly are senile
• We will be forgetful
• Forgetfulness Vs. Alzheimer’s disease
235
Cognitive Decline in the Elderly
• Changes in the Brain
- Less neurons
- Less synapses
- Decreased neurotransmitters
236
Respiratory System (Elderly)
* Decreased respiratory rate (12-16bpm)
| * Decreased lung volumes and capacities
237
Digestive System (Elderly)
```
• Loss of dentition
• Loss of taste buds
• Less GI secretions - Difficulty in swallowing
• Decreased capacity of stomach
• Decreased peristalsis
- Constipation
- ...At risk for malnutrition
```
238
Immune System (Elderly)
• Decreased capacity of the innate system to provide protection
- Altered skin and mucous membranes
- Decreased saliva
```
• Decreased circulating lymphocytes
• More prone to some infectious diseases
• With increased morbidity and mortality (poorer outcomes)
• Immunizations needed
- Flu vaccine yearly
- Pneumococcal vaccine
- Tetanus vaccine
- Zoster vaccine
```
239
Excretory System (Elderly)
```
• Loss of nephrons
• Shrinking of kidneys
• Decline in kidney function
• More pliant urinary bladder
- Lower threshold
- Weak muscles -> Urinary Incontinence
```
240
Endocrine System (Elderly)
* Decrease in the activity of glands
* Decrease in circulating hormones
* Increased resistance of receptors
241
Male Reproductive System (Elderly)
* Prostate gland starts to increase at age 40
* Andropause
* Decreased libido
* Sexual dysfunction: Erectile dysfunction and Retrograde ejaculation
242
Female Reproductive System (Elderly)
* Changes associated with menopause
* Atrophy of the uterus and ovaries
* Atrophy of the lining of the vaginal canal
* Decrease in lubrication
* Prolapse – weakening of the pelvic floor
243
WALL OF THE EYE: 3 concentric layers
A. Outer layer - fibrous coat: cornea, conjunctiva, sclera
B. Middle layer - vascular coat: iris and choroid
C. Inner layer - neural layer: retina
244
- connective tissue and covers the posterior 5/6 of the globe
- Connected to the dura mater
- Maintains the shape of the globe
Sclera
245
* Major refractive area; most anterior portion of the eye
| * first contact with the light wave
Cornea
246
• Junction of Iris and Sclera
Limbus
247
* Thin, transparent mucus membrane
* Covers posterior surface of the eye lids and anterior surface of the sclera
* Bulbar and palpebral
Conjunctiva
248
• Rich in blood vessels
Choroid
249
* Has papillary dilator and sphincter muscle
| * Controls the entry of light through the pupil
Iris
250
• Transparent, contains nerves
• Covers the posterior of the eye except the “blind spot”
• Visual Acuity is highest at central part (Macula Lutea)
• 2 main blood supplies of the retina
*Central retinal artery and the choroidal arteries
Neural Coat: Retina
251
* Biconvex, crystalline structure
* Covered by a capsule
* Suspended from the ciliary body by the Zonule Fiber or Suspensory ligaments.
LENS
252
* Help maintain the shape of the eye
* Maintains sufficient pressure in the eyeball to keep it distended
* Divided into two portions as separated by the lens
FLUID SYSTEM OF THE EYE
253
* Clear fluid
* Composed of water and ions
* Other: protein, glucose, ascorbic
* Osmotic pressure is higher than plasma
* Formed as a secretion by the epithelium of Ciliary Process
Aqueous humor
254
* Posterior surface of the lens and retina
* Gelatinous mass
* Containing collagen and hyaluronic acid
* Slow diffusion and little flow of fluid
Vitreous humor
255
Flow of Aqueous Humor
Ciliary processes -> anterior chamber ->
| pupil -> trabecular meshwork -> Canal of Schlemm
256
* Production vs drainage of aqueous humor
* Any abnormality: Increased Ocular pressure
* Normal IOP: 10-20 mmHg (±2mmHg)
INTRAOCULAR PRESSURE
257
* eye condition that lead to damage to the optic nerve
* IOP pathologically high
* Could lead to blindness
* Tunnel vision
* Primary symptoms: headache, nausea, vomiting
GLAUCOMA
258
* VISIBLE light- tiny portion of the electromagnetic spectrum of energy
* Ranges from 380-760 that can stimulate the photoreceptors of the human retina to produce a visual response.
* Light rays travel differently with different substance
Refraction of Light
259
Different media = different refractive indices
* Air > solid/ fluid
* If Beam is PERPENDICULAR = no deviation of course, only a decrease in velocity
* If Beam is ANGULATED = refraction of ray
260
• bending of light rays at an angulated interface
REFRACTION
261
• Ratio of the speed of light in the air to a speed of light to a substance
REFRACTIVE INDEX
262
Two factors that affect the amount of refraction:
* Difference in the R.I. of the 2 media
| * Degree of angulation of medium
263
Convex Lens vs Concave Lens
• Convex lens
- converge light
- Thicker at the middle
• Concave lens
- diverge light
- Thinner at the middle
264
Lens system will pass
1. Air and anterior surface of cornea
2. Posterior surface of cornea and Aqueous humor
3. Aqueous humor and anterior surface of lens
4. Posterior surface of lens and vitreous humor
265
Optics of the eye
• The greater the lens bends light rays, the greater the refractive power
• Refractive power is measured in DIOPTERS
• Lens refractive power = 1 meter divided by the focal length of a converging lens
• Total refractive power= 59
• Cornea: greatest refractive power (2/3)
• Aq. Humor/lens/vit humor: minimal refractive power
• Power of the lens = 20 Diopters
However, the LENS addresses errors through ACCOMMODATION
266
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• the adjustment power of the lens to maintain clear focus. (Up to 34 Diopters)
• MECHANISM:
1. Parasympathetic Innervation
2. Ciliary Muscle Contraction
3. Zonular suspensory ligaments
4. Increase AP diameter of lens
5. Subject can focus on near objects because of INCREASES IN FOCAL POWER
• Decreases as we age
- 14D up to 40 years
- 2D at 40-50 years
- 0 D at 70 years
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Accommodation
267
• lack of accommodation with age which requires + lens to increase
Presbyopia
268
* Defects of focusing = discrepancy between the size of the eye & refractive power of dioptic media
* Emmetropia- normal vision
Errors of Refraction
269
• Far sightedness
- Image is focused behind the retina
- Due to: poor refractive power or short axial length
- Correction: Converging lens
Hyperopia
270
• Shortsightedness
- Far objects focused in front of retina
- Due to: lens with too much refractive power or the eyeball is too long
- Correction: Diverging lens
Myopia
271
• lack of accommodation with age which requires + glass to increase
Presbyopia
272
* too great a curvature of the cornea in one plane of the eye
* Multiple focal points
Astigmatism
273
* Rods and cones
| * Photosensitive cells that convert chemical energy into electrical energy
Receptor cells
274
* horizontal direction
* Photoreceptors to bipolar cell
* Always inhibitory
* Mechanism for lateral inhibition
* High visual accuracy in transmitting contrast borders in the visual image
Horizontal cells
275
* Vertical direction
| * From rods, cones and horizontal cells to the ganglion and amacrine cells
Bipolar cells
276
• interneurons that analyze visual signals before they leave retina
• 2 directions
- Vertically : Bipolar to ganglion cells
- Horizontally: within the inner plexiform layer
Amacrine cells
277
* Axons generate to the optic nerve
| * Send repetitive action potentials to the CNS
Ganglion Cells
278
Rods and Cones
Rods
• Generally narrower and longer
• scoptic vision
• Low threshold for detecting light
Cones
• photopic vision
• High threshold for light
• For high VA and color vision
279
Peripheral vs. Central Retina
• Higher visual acuity in the central retina
- Longer and fewer rods and cones in the center and as the fovea is approached rods disappear
- Number of optic nerve fibers leaving this part of the retina is almost equal to the number of cones
• Greater sensitivity of peripheral retina to weak light
- Rods are more sensitive to light than cones
- More rods in the periphery
- As many as 200 rods converge on a single optic nerve fiber
280
• Transduction of signal requires hyperpolarization of rods and cones
• Light energy is absorbed to be detected by the retina (Visual pigment: rhodopsin)
• Rhodopsin = 11-cis retinal + opsin
• After absorption of light
- 11-cis retinal -> 11-trans retinal
- Retinal -> retinol
Visual Transduction
281
Photosensitive chemical: rhodopsin
Location: Outer segment
Opsin: scotopsin
Chromophore: 11 cis retinal
Rods
282
Photosensitive chemical: Color pigments
Location: Outer segment
Opsin: photopsin
Chromophore: 11 cis retinal
Cones
283
Pathway 1 (light state)
Precursor: All trans Retinal
Enzyme: Retinal isomerase
Final Product: 11 cis retinal
284
Pathway 2 (dark state)
Precursor: Retinol
Enzyme: Isomerase
Intermediate Product: 11 cis retinol
Final Product: 11 cis retinal
285
• Poor night vision due to deficiency of Retinol
• Retinol (Vitamin A) is derived from carotenoids
- cannot be synthesized
• Rhodopsin contains retinal (an aldehyde of retinol)
NIGHT BLINDEDNESS
286
Visual Transduction: DARKNESS
* Slightly depolarized
* cGMP-gated Na+ channels are open
* Continuous current of Na+ influx = Dark Current
* Glutamate is tonically released in the synapses
287
Visual Transduction: BRIGHT
* Light is absorbed
* photoisomerization of rhodopsin -> activates G protein transluscent -> activates cyclic guanosine monophosphate phosphodiesterase -> hydrolyzes cGMP to 5'-GMP
* lowers the cGMP concentration
* closing of the cGMP-gated Na+ channels
* hyperpolarization of the photoreceptor membrane
288
* Visual area seen by an eye at a given instant
* Nasal side – temporal field of vision
* Temporal side – nasal field of vision
Visual Field
289
• Charting of the field of vision
• Blind spot
- Lack of rods and cones in the retina over optic disc
- 15 degrees lateral to the central point of vision
Perimertry
290
* Damage to the optic nerve
* Glaucomas, immune reactions in the retina or toxic conditions
* Blind spot in portions other than the optic disc
SCOTOMA
291
* Degeneration of parts of retina
* Excessive melanin deposits
* Blindness in the peripheral field of vision first and then gradually on the central area
RETINITS PIGMENTOSA
292
Visual Pathway
Visual Field -> Retina ganglion -> Optic Nerve
-> Optic Chiasm -> Optic Tract -> Lateral Geniculate Nucleus -> Optic Radiations -> Primary Visual cortex (BA 17/Striate cortex)
293
(Visual Pathway and Visual Defects)
Target is reversed in the retina by the lens system
* Left Visual Field: L nasal and R temporal
| * Right Visual Field: R nasal and L temporal
294
(Visual Pathway and Visual Defects)
Projection may be crossed or uncrossed
* Axons at temporal: uncrossed
| * Axons at nasal: crossed at optic chiasm
295
(Visual Pathway and Visual Defects)
Some fibers go to temporal lobe as Meyer’s Loop
• Lower retinal quadrant: superior visual field
296
(Visual Pathway and Visual Defects)
Fibers that pass through parietal lobe
• Contralateral lower visual field
297
(Visual Pathway and Visual Defects)
Optic radiation ends in the Stiate Cortex
Cuneus
- Dorsal of fissure
- upper part of hemiretina
Lingual gyrus
- Ventral of fissure
- lower part of hemiretina
298
* Lies in the calcarine fissure extending towards the occipital pole
* Medial to each occipital cortex
* Brodmann’s area 17
Primary Visual Cortex
299
* Visual association areas
* Where analysis and meaning to visualized objects occur
* Lateral, anterior, superior and inferior to the primary visual cortex
* Brodmann’s area 18
Secondary Visual Cortex
300
* Helps the eye adapt to extremely rapidly changing light conditions
* Impulses from retina are sent to Edinger-Westphal nucleus causing constriction of iris.
* Darkness: inhibition of reflex causing mydriasis
Pupillary Light Reflex
301
Miosis vs Mydriasis
Miosis - Parasympathetic stimulation; sphincter muscle to constrict the pupil
Mydriasis - Sympathetic stimulation ; radial fibers to cause dilatation
302
Direct vs. Consensual
Direct reflex: shining light directly on pupil will constrict it
Consensual reflex: shining light on one pupil will constrict the other pupil as well
303
* Only 3 types of color pigments: Blue, Green, Red
* Selectively sensitivity to different colors
* Opsin of cones- photopsin
* color-sensitive pigment- retinal +photopsin
Color Vision
304
Tricolor Mechanism of Color Detection
* Spectral sensitivities of the 3 types of cones
| * Ratio of cones stimulated
305
Perception of White Light
* Equal stimulation of all red, green, blue cones
* No single wavelength of light
* Proper combination of the 3 cones about equally
306
* Unable to distinguish some colors from others
* Absence of a single group of cones
* X-linked genetic disorder- exclusively in males
COLOR BLINDNESS
307
Types of Color Blindness
• Protanope
- loss of red cones
- Shortened wavelength
• Deuteranope
- loss of green cones
- Normal wavelength
• Blue weakness
- rare; blue cones are missing
308
Depth Perception (Based on 3 things)
1. Images of known objects
2. Moving parallax
3. Stereopsis- binocular vision
a. One eye is approximately 2 inches from the other causing a difference in what the two retinas perceive
b. Better judge of distance and depth when objects are nearby (vs one eye only)
c. Useless for depth perception at 50-200 feet
309
a. If one knows that a person being viewed is 6 feet tall, one can determine how far away the person is simply by the size of the person’s image on the retina.
b. brain has learned to calculate automatically
Images of known objects
310
a. As we move our heads or bodies, nearby objects appear to move more quickly than distant objects
b. Relative distances on different objects
Moving parallax
311
a. One eye is approximately 2 inches from the other causing a difference in what the two retinas perceive
b. Better judge of distance and depth when objects are nearby (vs one eye only)
c. Useless for depth perception at 50-200 feet
Stereopsis- binocular vision
312
* Proprioception+ vestibular function +vision
* VISION
- most significant contributor to balance
- bigger role than either of the two other intrinsic mechanisms
• Visual factors affecting balance
- clarity with which an individual can see
- size of the visual field
- susceptibility of the individual to light and glare
- poor depth perception
Balance
313
* Light resets the biological clock in accordance with the phase response curve (PRC).
* Can advance or delay the circadian rhythm, depending on the timing
Sleep-Wake Cycle
