Action potential By Dr. Mrs. Padmaja R Desai Physiology Dept
To study the Concept of Action Potential and describe the stages of action potential.
Ionic basis of Action Potential & its Propogation.
Properties of Action Potential.
Types action Potential
Action potential By Dr. Mrs. Padmaja R Desai Physiology Dept
To study the Concept of Action Potential and describe the stages of action potential.
Ionic basis of Action Potential & its Propogation.
Properties of Action Potential.
Types action Potential
This is about the membrane action potential.it involves the stages of action potential.
there are also resting membrane potential.
this ppt is for zoology 6 semester course code Z0L- 504
GCUF.
Nerve Impulse is defined as a wave of electrical chemical changes across the neuron that helps in the generation of the action potential in response to the stimulus. This transmission of a nerve impulse across the neuron membrane as a result of a change in membrane potential is known as Nerve impulse conduction.
Mechanism of Nerve Impulse Conduction
Nerve impulse conduction is a major process occurring in the body responsible for organized functions of the body. So, for conduction of nerve impulse there are two mechanisms:
Continuous conduction
Saltatory conduction
Why do ion channels not function like open poresWhat is membrane .pdfjaronkyleigh59760
Why do ion channels not function like open pores?
What is membrane potential?
How do K+ leak channels work? Why is the membrane potential of a resting cell negative?
What is patch clamp recording? What is one of the major insights gained from patch clamp
reporting experiments?
Compare and contrast the three types of gated ion channels.
Be familiar with the different parts of a neuron.
During an action potential, what happens to the membrane potential, voltage-gated Na+
channels, Na+ ions, voltage gated K+ channels, K+ ions, and Na+-K+ ion pumps?
When an action potential reaches a synapse, what happens to the Ca2+ channels, Ca2+ ions,
neurotransmitters, transmitter-gated ion channels, and the post synaptic neuron?
What effect do excitatory or inhibitory neurotransmitters have on postsynaptic cells?
What is an example of a mechanically gated ion channel?
Solution
1.Excitable cells, such as fast-acting neurons and muscle cells, have specialized channels that
open in response to a signal and permit rapid ion movement across the cell membrane. The
opening of just a single ion channel alters the electrical charge on both sides of the membrane.
The resulting charge differential then causes adjacent voltage-sensitive channels to open in
chain-reaction fashion, creating a self-propagating electrical signal that travels down the entire
length of the cell. Sometimes, this sequence of events is triggered when a chemical signal —
such as a neurotransmitter — binds to an ion channel receptor on cell\'s surface. Other times, a
cell\'s ion channels open in response to mechanical (rather than chemical) stimuli.
2.In cells of all types, there is an electrical potential difference between the inside of the cell and
the surrounding extracellular fluid. This is termed the membrane potential of the cell. When a
nerve or muscle cell is at \"rest\", its membrane potential is called the resting membrane
potential. In a typical neuron, this is about –70 millivolts (mV). The minus sign indicates that the
inside of the cell is negative with respect to the surrounding extracellular fluid.
3.The leak channels allow K+ to move across the cell membrane down their gradients (from a
high concentration toward a lower concentration).
With the combined ion pumping and leakage of ions, the cell can maintain a stable resting
membrane potential and create membrane potential of a resting cell negative.
4.Patch clamp recording is an extremely useful technique for investigating the biophysical
properties of the ion channels that control neuronal activation.
The procedure involves pressing a glass micropipette against a cell in order to isolate a small
“patch” of membrane that contains one or more ion channels.
The experimental setup further allows scientists to “clamp” the electrical environment of the
patched area by precisely controlling the voltage across the cell membrane, which, depending on
the ion channels present, impacts the flow of ions through the membrane and allow for int.
This is about the membrane action potential.it involves the stages of action potential.
there are also resting membrane potential.
this ppt is for zoology 6 semester course code Z0L- 504
GCUF.
Nerve Impulse is defined as a wave of electrical chemical changes across the neuron that helps in the generation of the action potential in response to the stimulus. This transmission of a nerve impulse across the neuron membrane as a result of a change in membrane potential is known as Nerve impulse conduction.
Mechanism of Nerve Impulse Conduction
Nerve impulse conduction is a major process occurring in the body responsible for organized functions of the body. So, for conduction of nerve impulse there are two mechanisms:
Continuous conduction
Saltatory conduction
Why do ion channels not function like open poresWhat is membrane .pdfjaronkyleigh59760
Why do ion channels not function like open pores?
What is membrane potential?
How do K+ leak channels work? Why is the membrane potential of a resting cell negative?
What is patch clamp recording? What is one of the major insights gained from patch clamp
reporting experiments?
Compare and contrast the three types of gated ion channels.
Be familiar with the different parts of a neuron.
During an action potential, what happens to the membrane potential, voltage-gated Na+
channels, Na+ ions, voltage gated K+ channels, K+ ions, and Na+-K+ ion pumps?
When an action potential reaches a synapse, what happens to the Ca2+ channels, Ca2+ ions,
neurotransmitters, transmitter-gated ion channels, and the post synaptic neuron?
What effect do excitatory or inhibitory neurotransmitters have on postsynaptic cells?
What is an example of a mechanically gated ion channel?
Solution
1.Excitable cells, such as fast-acting neurons and muscle cells, have specialized channels that
open in response to a signal and permit rapid ion movement across the cell membrane. The
opening of just a single ion channel alters the electrical charge on both sides of the membrane.
The resulting charge differential then causes adjacent voltage-sensitive channels to open in
chain-reaction fashion, creating a self-propagating electrical signal that travels down the entire
length of the cell. Sometimes, this sequence of events is triggered when a chemical signal —
such as a neurotransmitter — binds to an ion channel receptor on cell\'s surface. Other times, a
cell\'s ion channels open in response to mechanical (rather than chemical) stimuli.
2.In cells of all types, there is an electrical potential difference between the inside of the cell and
the surrounding extracellular fluid. This is termed the membrane potential of the cell. When a
nerve or muscle cell is at \"rest\", its membrane potential is called the resting membrane
potential. In a typical neuron, this is about –70 millivolts (mV). The minus sign indicates that the
inside of the cell is negative with respect to the surrounding extracellular fluid.
3.The leak channels allow K+ to move across the cell membrane down their gradients (from a
high concentration toward a lower concentration).
With the combined ion pumping and leakage of ions, the cell can maintain a stable resting
membrane potential and create membrane potential of a resting cell negative.
4.Patch clamp recording is an extremely useful technique for investigating the biophysical
properties of the ion channels that control neuronal activation.
The procedure involves pressing a glass micropipette against a cell in order to isolate a small
“patch” of membrane that contains one or more ion channels.
The experimental setup further allows scientists to “clamp” the electrical environment of the
patched area by precisely controlling the voltage across the cell membrane, which, depending on
the ion channels present, impacts the flow of ions through the membrane and allow for int.
NVBDCP.pptx Nation vector borne disease control programSapna Thakur
NVBDCP was launched in 2003-2004 . Vector-Borne Disease: Disease that results from an infection transmitted to humans and other animals by blood-feeding arthropods, such as mosquitoes, ticks, and fleas. Examples of vector-borne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria.
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
Prix Galien International 2024 Forum ProgramLevi Shapiro
June 20, 2024, Prix Galien International and Jerusalem Ethics Forum in ROME. Detailed agenda including panels:
- ADVANCES IN CARDIOLOGY: A NEW PARADIGM IS COMING
- WOMEN’S HEALTH: FERTILITY PRESERVATION
- WHAT’S NEW IN THE TREATMENT OF INFECTIOUS,
ONCOLOGICAL AND INFLAMMATORY SKIN DISEASES?
- ARTIFICIAL INTELLIGENCE AND ETHICS
- GENE THERAPY
- BEYOND BORDERS: GLOBAL INITIATIVES FOR DEMOCRATIZING LIFE SCIENCE TECHNOLOGIES AND PROMOTING ACCESS TO HEALTHCARE
- ETHICAL CHALLENGES IN LIFE SCIENCES
- Prix Galien International Awards Ceremony
Report Back from SGO 2024: What’s the Latest in Cervical Cancer?bkling
Are you curious about what’s new in cervical cancer research or unsure what the findings mean? Join Dr. Emily Ko, a gynecologic oncologist at Penn Medicine, to learn about the latest updates from the Society of Gynecologic Oncology (SGO) 2024 Annual Meeting on Women’s Cancer. Dr. Ko will discuss what the research presented at the conference means for you and answer your questions about the new developments.
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...VarunMahajani
Disruption of blood supply to lung alveoli due to blockage of one or more pulmonary blood vessels is called as Pulmonary thromboembolism. In this presentation we will discuss its causes, types and its management in depth.
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micro teaching on communication m.sc nursing.pdfAnurag Sharma
Microteaching is a unique model of practice teaching. It is a viable instrument for the. desired change in the teaching behavior or the behavior potential which, in specified types of real. classroom situations, tends to facilitate the achievement of specified types of objectives.
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
Acute scrotum is a general term referring to an emergency condition affecting the contents or the wall of the scrotum.
There are a number of conditions that present acutely, predominantly with pain and/or swelling
A careful and detailed history and examination, and in some cases, investigations allow differentiation between these diagnoses. A prompt diagnosis is essential as the patient may require urgent surgical intervention
Testicular torsion refers to twisting of the spermatic cord, causing ischaemia of the testicle.
Testicular torsion results from inadequate fixation of the testis to the tunica vaginalis producing ischemia from reduced arterial inflow and venous outflow obstruction.
The prevalence of testicular torsion in adult patients hospitalized with acute scrotal pain is approximately 25 to 50 percent
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdfAnujkumaranit
Artificial intelligence (AI) refers to the simulation of human intelligence processes by machines, especially computer systems. It encompasses tasks such as learning, reasoning, problem-solving, perception, and language understanding. AI technologies are revolutionizing various fields, from healthcare to finance, by enabling machines to perform tasks that typically require human intelligence.
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
2. Graded Potentials
Action Potential
Objectives: Student should know
1. Graded potential
2. Types of graded potentials
3. Action potential
4. Three stages of action potential
5. Types of action potential
6. Generation of action potential
7. Properties of action potentials
8. Differences – graded vs action potential
3. Graded Potentials
A. Subthreshold electrical stimuli that do not produce a
true action potential but do generate electrical signals
B. Stimuli may be electrical, chemical, or mechanical
C. Stimuli produce two types of physiochemical
disturbances
4. Graded Potentials
1. Local, graded, non propagated potentials called
receptor or generator potentials, synaptic potentials or
electrotonic potentials
2. Action potentials (complete depolarization) or nerve
impulses which are propagated down the axon to cause
the release of neurotransmitters
8. Graded Potentials Local Response
A. Subthreshold response
B. Characteristics of graded potentials
1. It is Local - changes in membrane potential are confined
to relatively small regions of the plasma membrane
2. It is graded - Refers to the magnitude of the potential
change and that the signal can be reinforced.
9. Graded Potentials Local Response
A. Magnitude can
vary (is graded) with
the magnitude of the
stimulus
B. Graded events can
be hypopolarizing
(depolarizing -
decrease in potential
difference) or
hyperpolarizing
10. Graded Potentials Local Response
3. Graded potentials
are conducted with
decrement.
(conduction
magnitude falls off
the further you get
from the point of
origin)
11. Graded Potentials Local Response
A. Charge is lost across the membrane because of “leaky” channels and
the magnitude of the potential decreases with distance from the site of
origin (charge density falls).
B. Graded potentials and the local current they generate can function
as signals over very short distances
C. Graded potentials die out in 1 - 2 mm of the origin
12. Types of Graded Potentials
1. Characteristics of Graded Potentials
a. Only type of communication by some neurons
b. Play an important role in the initiation and integration of
long distance signals by neurons and other cells
13. Types of Graded Potentials
2. Specific types of graded potentials
a. Receptor (Generator) potentials
1) Sensory receptors respond to stimuli from mechanoreceptors,
thermoreceptors, nociceptors (pain), chemoreceptors, and
electromagnetic receptors (vision)
a) Graded potential from stimuli is
called receptor potential
b) If graded potential reached
threshold an action potential is
generated and sensory information is
sent to the spinal cord and brain
14. Types of Graded Potentials
b. Pacemaker potential - heart
1) Specialized coronary muscle
cells in the cardiac pacemaker
region (SA node) have “leaky” ion
channels graded potentials can
potentially induce a true cardiac
action potential
2) Graded potential is responsible
for cardiac automaticity
15. Types of Graded Potentials
c. Postsynaptic membrane potentials
1) Graded potentials that develop
on the postsynaptic membrane
during synaptic transmission
(stimuli from other nerves - can be
stimulatory or inhibitory)
2) If graded potentials reach
threshold action potential develops
16. Types of Graded Potentials
D. EPP End Plate Potential
Post synaptic graded potential that develops at the
neuromuscular junction (always stimulatory and always reach
threshold if generated by an action potential in the
innervating alpha motor neuron). Postsynaptic membrane
potentials are important in AP generation in nerve to nerve
and nerve to muscle communication.
17. Action Potential
Generation
Graded Potentials which reach threshold generate action
potentials
1. Much larger response - Membrane polarity reverses
(complete depolarization)
2. AP are propagated without decrement
a. Size and shape of AP are constant along nerve fiber
18. Action Potential
Generation
All or None Response - Size
and shape of AP are not
influenced by the size of the
stimulus
Action Potential - Rapid but transient change in a
membrane potential - Change in local membrane polarity
-
Polarized___Depolarized___Polarized
20. Action Potential
Generation
The Action Potential
Characteristics of action potentials
1. Requires specific voltage- gated ion channels
2, AP are the result of rapid changes in ion conductance
3. AP occur only on regions of cell membranes that are electrically excitable
4. AP generally are a standard size and shape for a specific cell type
5. All or none - when membrane reaches threshold an AP is generated (Not-
Graded)
21. Action Potential Generation
The Action Potential
6. Time - AP not only have a specific size and shape but also
exists within a specific time frame , ave. 1 to 5 msec.- (ie time
duration of the action potential is always the same for a
specific tissue)
Specific to transport protein cycle times
22. Action Potential
Generation
Importance of Action Potentials
Nerve traffic, muscle contraction,
hormone release, G.I. secretions,
Cognitive thought, etc.
Action Potentials are required for the
senses - Sight, hearing, and touch are
all dependent on action potentials for
transmission of information to the brain
Threshold stimuli (Graded Potential)
cause the.generation of an action
potential
23. Action Potential
Generation
Three Stages of the Action Potential
1. Resting stage - Polarized stage - This is the normal resting
membrane potential and varies with the cell type nerve = -
90 mV, heart pacemaker = -60 mV, and skeletal muscle = -83
mV
2. Depolarization stage - Sodium ions (Na+) flow into the
cell as the threshold for voltage gated Na+ channels are
exceeded.
24. Action Potential
Generation
3. Repolarization stage - Potassium (K+) ions flow out of the
cell as voltage gated K+ channels are opened and the cell
membrane potential moves back toward the resting
membrane potential.
30. Action Potential
Generation
Components of an Action Potential
1. Threshold - Membrane potential at which voltage gated
channels will open
2. Rising phase - as Na+ channels open membrane potential
begins to shift toward the equilibrium potential for Na+
(Nernst Potential for Na+)
3. Overshoot - The point at which the membrane potential
becomes positive. The greater the overshoot
potential the further the membrane will
stay above threshold
31. Action Potential
Generation
4. Peak - At the peak of the action potential the sodium
conductance begins to fall (Closure of the slow gate)
5. Repolarization - Inactivation of sodium channels and
opening of the K+ channels (Opening of the K+ voltage
channel slow gate) causes repolarization
6. Threshold - As the membrane potential passes back
through threshold the voltage gated channels reset (both the
Na+ and K+ channels)
32. Action Potential
Generation
7. After - hyperpolarization - The Na+ voltage gated
channels have a fast gate and a slow gate passage of the
membrane potential back through threshold causes the fast
gate to close too rapidly for any Na+ ions to pass while the
slow gate opens. The K+ voltage gate with it’s single slow
gate begins to close slowly so for a period of time K+ still
flows out of the cell hyperpolarizing the cell. Return to
resting membrane voltage is due to Na+K+ATPase
35. Action Potential Generation
Properties
Properties of Action
Potentials -
Refractory periods
are times when it is
either impossible or
more difficult than
normal to generate
a second action
potential.
36. Action Potential Generation
Properties
Absolute Refractory
During this period the
voltage gated
channels responsible
for the action
potential have not
reset and therefore,
do not respond to
stimulation.
37. Action Potential Generation
Properties
Relative Refractory
This period
corresponds to the
positive after
potential period and
due to the
hyperpolarization of
the cell it is more
difficult to generate a
second action
potential.
38. Action Potential
Generation
Properties
Voltage Inactivation - If a cell membrane is
maintained at a voltage potential above
threshold than the voltage gated channels
are not reset and, hence, inactivated and
no action potentials can be generated.
Accommodation to Slow Depolarization -
If a slow depolarization occurs the voltage
gated channels do not respond and no
action potential occurs.
40. Definition
Hypoxia is the commonest pathological
process,which is defined as that cells can
not obtain enough oxygen or can not fully
utilize oxygen,thus leading to changes in
their metabolism,function,or structure.
Hypoxia
42. Partial pressure of oxygen(PO2)
1.Definition:the tension produced by oxygen
molecules physically dissolved in plasma.
2.Normal value: PaO2=13.3kPa(100mmHg)
PvO2=5.33kPa(40mmHg)
Hypoxia
43. Oxygen binding capacity (CO2max)
1. Definition:It is the maximum amount of
oxygen that can be combined to hemoglobin in
100 ml of blood.
2.Normal value: 20ml/dl
Hypoxia
45. Arteriovenous oxygen content (Ca-vO2)
19ml/dl 14ml/dl
5ml/dl
O2 O2 O2 O2 O2
A V
Definition: It is the difference of oxygen
content between arterial blood and mixed
venous blood.
Normal value: 5ml/dl
46. Definition: It is the percentage of
hemoglobin present as oxyhemoglobin.
Oxygen saturation (SO2)
Normal value:SaO2=95%; SvO2=70%
CO2-dissolved O2
CO2max
100%
=
SO2
Hypoxia
47. P50
Definition: P50 is a parameter reflecting
the affinity of Hb to oxygen; it is the O2
pressure required to sturate 50% of Hb.
Normal value:26~28 mmHg