The nervous system is a highly organized network of billions of nerve cells that functions as the body's control center by integrating sensory information, processing signals, and initiating motor responses through the central and peripheral nervous systems. It is composed of neurons, which communicate through electrical and chemical signals, and neuroglia, which provide support and insulation. The peripheral nervous system connects the central nervous system to the rest of the body and is divided into sensory and motor divisions that receive input and initiate output, respectively.
a quick visual understanding of what actually nervous tissue is made up of at cellular level its functions nerve cell types chemical synapse detailed structure of neuron
Peripheral Nervous System, Audumbar MaliAudumbar Mali
Peripheral Nervous System,
Types of PNS,
Spinal nerves,
Types of neuron (3 basic types),
Plexus,
Cranial nerves,
Autonomic nervous system,
Structure of Neuron,
Human Anatomy and Physiology-I,
Syllabus As per PCI,
B. Pharm-I
a quick visual understanding of what actually nervous tissue is made up of at cellular level its functions nerve cell types chemical synapse detailed structure of neuron
Peripheral Nervous System, Audumbar MaliAudumbar Mali
Peripheral Nervous System,
Types of PNS,
Spinal nerves,
Types of neuron (3 basic types),
Plexus,
Cranial nerves,
Autonomic nervous system,
Structure of Neuron,
Human Anatomy and Physiology-I,
Syllabus As per PCI,
B. Pharm-I
Nervous system PPT for grade 10 (basic concepts regarding human nervous system)AzkaSamreen
Human nervous system is highly complex, while reading in higher classes, we often mix up concepts. In this SlideShare I've tried to simplify the material for grade 10 students to better understand the concept.
Nervous system ( anatomy and physiology)Ravish Yadav
the topic contain function of nervous system, classification of nervous system, neurons anatomy, structural classification of neurons, functional classification of neurons, nerve impulse
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.
263778731218 Abortion Clinic /Pills In Harare ,sisternakatoto
263778731218 Abortion Clinic /Pills In Harare ,ABORTION WOMEN’S CLINIC +27730423979 IN women clinic we believe that every woman should be able to make choices in her pregnancy. Our job is to provide compassionate care, safety,affordable and confidential services. That’s why we have won the trust from all generations of women all over the world. we use non surgical method(Abortion pills) to terminate…Dr.LISA +27730423979women Clinic is committed to providing the highest quality of obstetrical and gynecological care to women of all ages. Our dedicated staff aim to treat each patient and her health concerns with compassion and respect.Our dedicated group ABORTION WOMEN’S CLINIC +27730423979 IN women clinic we believe that every woman should be able to make choices in her pregnancy. Our job is to provide compassionate care, safety,affordable and confidential services. That’s why we have won the trust from all generations of women all over the world. we use non surgical method(Abortion pills) to terminate…Dr.LISA +27730423979women Clinic is committed to providing the highest quality of obstetrical and gynecological care to women of all ages. Our dedicated staff aim to treat each patient and her health concerns with compassion and respect.Our dedicated group of receptionists, nurses, and physicians have worked together as a teamof receptionists, nurses, and physicians have worked together as a team wwww.lisywomensclinic.co.za/
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.
Knee anatomy and clinical tests 2024.pdfvimalpl1234
This includes all relevant anatomy and clinical tests compiled from standard textbooks, Campbell,netter etc..It is comprehensive and best suited for orthopaedicians and orthopaedic residents.
Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
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
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.
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
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
1. The Nervous System
• A network of billions of nerve cells linked
together in a highly organized fashion to
form the rapid control center of the body.
• Functions include:
– Integrating center for homeostasis,
movement, and almost all other body
functions.
– The mysterious source of those traits that we
think of as setting humans apart from animals
2. Basic Functions of the Nervous System
1. Sensation
• Monitors changes/events occurring in and outside the
body. Such changes are known as stimuli and the cells
that monitor them are receptors.
2. Integration
• The parallel processing and interpretation of sensory
information to determine the appropriate response
3. Reaction
• Motor output.
– The activation of muscles or glands (typically via the release
of neurotransmitters (NTs))
3. Nervous vs. Endocrine System
• Similarities:
– They both monitor stimuli and react so as to
maintain homeostasis.
• Differences:
– The NS is a rapid, fast-acting system whose
effects do not always persevere.
– The ES acts slower (via blood-borne chemical
signals called H _ _ _ _ _ _ _) and its actions
are usually much longer lasting.
4. Organization of the
Nervous System
• 2 big initial divisions:
1. Central Nervous System
• The brain + the spinal cord
– The center of integration and control
2. Peripheral Nervous System
• The nervous system outside of the
brain and spinal cord
• Consists of:
– 31 Spinal nerves
»
5. Peripheral Nervous System
• Responsible for communication btwn the CNS
and the rest of the body.
• Can be divided into:
– Sensory Division
• Afferent division
– Conducts impulses from receptors to the CNS
– Informs the CNS of the state of the body interior and exterior
– Sensory nerve fibers can be somatic (from skin, skeletal
muscles or joints) or visceral (from organs w/i the ventral body
cavity)
– Motor Division
• Efferent division
– Conducts impulses from CNS to effectors (muscles/glands)
– Motor nerve fibers
6. Motor Efferent Division
• Can be divided further:
– Somatic nervous system
• VOLUNTARY (generally)
• Somatic nerve fibers that conduct impulses from
the CNS to skeletal muscles
– Autonomic nervous system
• INVOLUNTARY (generally)
• Conducts impulses from the CNS to smooth
muscle, cardiac muscle, and glands.
7. Autonomic Nervous System
• Can be divided into:
– Sympathetic Nervous
System
• “Fight or Flight”
– Parasympathetic
Nervous System
• “Rest and Digest”
These 2 systems are antagonistic.
Typically, we balance these 2 to keep ourselves in a
state of dynamic balance.
We’ll go further into the difference btwn these 2
later!
8. 1.
Nervous Tissue
• Highly cellular
– How does this compare
to the other 3 tissue
types?
• 2 cell types
1. Neurons
2.
• Functional, signal
conducting cells
2. Neuroglia
• Supporting cells
9. Neuroglia
• Outnumber neurons by about
10 to 1 (the guy on the right had
an inordinate amount of them).
• 6 types of supporting cells
– 4 are found in the CNS:
1. Astrocytes
• Star-shaped, abundant, and
versatile
• Guide the migration of
developing neurons
• Act as K+ and NT buffers
• Involved in the formation of the
blood brain barrier
• Function in nutrient transfer
10. Neuroglia
2. Microglia
• Specialized immune cells that act
as the macrophages of the CNS
• Why is it important for the CNS to
have its own army of immune
cells?
2. Ependymal Cells
• Low columnar epithelial-esque
cells that line the ventricles of the
brain and the central canal of the
spinal cord
• Some are ciliated which
facilitates the movement of
cerebrospinal fluid
11. Neuroglia
4. Oligodendrocytes
• Produce the
myelin
sheath
which
provides the
electrical
insulation for
certain
neurons in
the CNS
12. Neuroglia
• 2 types of glia in the
PNS
1. Satellite cells
• Surround clusters of
neuronal cell bodies in the
PNS
• Unknown function
2. Schwann cells
• Form myelin sheaths
around the larger nerve
fibers in the PNS.
• Vital to neuronal
regeneration
13. • The functional and structural unit Neurons
of the nervous system
• Specialized to conduct information from one part of the
body to another
• There are many, many different types of neurons but most
have certain structural and functional characteristics in
common:
- Cell body (soma)
- One or more
specialized, slender
processes
(axons/dendrites)
- An input region
(dendrites/soma)
- A conducting
component (axon)
- A secretory (output)
region (axon terminal)
14. Soma
• Contains nucleus plus most
normal organelles.
• Biosynthetic center of the
neuron.
• Contains a very active and
developed rough endoplasmic
reticulum which is responsible
for the synthesis of ________. In the soma above, notice the small
black circle. It is the nucleolus, the site
– The neuronal rough ER is
of ribosome synthesis. The light
referred to as the Nissl body.
circular area around it is the nucleus.
• Contains many bundles of The mottled dark areas found
protein filaments (neurofibrils) throughout the cytoplasm are the Nissl
which help maintain the shape, substance.
structure, and integrity of the
cell.
15. Somata
• Contain multiple
mitochondria. Why?
• Acts as a receptive service for interaction
with other neurons.
• Most somata are found in the bony
environs of the CNS. Why?
• Clusters of somata in the CNS are known
as nuclei. Clusters of somata in the PNS
are known as ganglia.
16. Neuronal Processes
• Armlike extensions emanating from every neuron.
• The CNS consists of both somata and processes whereas
the bulk of the PNS consists of processes.
• Tracts = Bundles of processes in the CNS (red arrow)
Nerves = Bundles of processes in the PNS
• 2 types of processes that differ in structure and function:
– Dendrites and Axons
17. • Dendrites are thin, branched processes whose main
function is to receive incoming signals.
• They effectively increase the surface area of a neuron to
increase its ability to communicate with other neurons.
• Small, mushroom-shaped dendritic spines further increase
the SA
• Convey info towards the soma thru the use of graded
potentials – which are somewhat similar to action potentials.
Notice the multiple
processes extending
from the neuron on the
right. Also notice the
multiple dark circular
dots in the slide. They’re
not neurons, so they
must be…
18. • Most neurons have a single
axon – a long (up to 1m)
process designed to convey
info away from the cell body.
• Originates from a special
region of the cell body called
the axon hillock.
• Transmit APs from the soma
toward the end of the axon
where they cause NT release.
• Often branch sparsely, forming
collaterals.
• Each collateral may split into
telodendria which end in a
synaptic knob, which contains
synaptic vesicles –
membranous bags of NTs.
19. Axons
• Axolemma = axon
plasma membrane.
• Surrounded by a myelin
sheath, a wrapping of lipid
which:
– Protects the axon and electrically isolates it
– Increases the rate of AP transmission
• The myelin sheath is made by ________ in the CNS and by
_________ in the PNS.
• This wrapping is never complete. Interspersed along the
axon are gaps where there is no myelin – these are nodes
of Ranvier.
• In the PNS, the exterior of the Schwann cell surrounding an
axon is the neurilemma
21. • A bundle of processes in the PNS is a nerve.
• Within a nerve, each axon is surrounded by an
endoneurium (too small to see on the photomicrograph) –
a layer of loose CT.
• Groups of fibers
are bound
together into
bundles
(fascicles) by a
perineurium (red
arrow).
• All the fascicles
of a nerve are
enclosed by a
epineurium
(black arrow).
22. Communication
• Begins with the stimulation of a neuron.
– One neuron may be stimulated by another, by a receptor cell, or
even by some physical event such as pressure.
• Once stimulated, a neuron will communicate information
about the causative event.
– Such neurons are sensory neurons and they provide info about
both the internal and external environments.
– Sensory neurons (a.k.a. afferent neurons) will send info to
neurons in the brain and spinal cord. There, association
neurons (a.k.a. interneurons) will integrate the information and
then perhaps send commands to motor neurons (efferent
neurons) which synapse with muscles or glands.
23. Communication
• Thus, neurons need to be able to
conduct information in 2 ways:
1. From one end of a neuron to the other end.
2. Across the minute space separating one
neuron from another. (What is this called?)
• The 1st is accomplished electrically via APs.
• The 2nd is accomplished chemically via
neurotransmitters.
24. Resting Potential
• Recall the definition of VM from the muscle
lectures.
• Neurons are also highly polarized (w/ a VM of about
–70mV) due to:
» Differential membrane permeability to K+ and Na+
» The electrogenic nature of the Na+/K+ pump
» The presence of intracellular impermeable anions
• Changes in VM allow for the generation of
action potentials and thus informative
intercellular communication.
25. Graded Potentials
• Let’s consider a stimulus at the dendrite of a neuron.
• The stimulus could cause Na+ channels to open and this
would lead to depolarization. Why?
• However, dendrites and somata typically lack voltage-
gated channels, which are found in abundance on the
axon hillock and axolemma.
– So what cannot occur on dendrites and somata?
• Thus, the question we must answer is, “what does this
depolarization do?”
26. Graded Potentials
• The positive charge carried by the Na+ spreads as a wave
of depolarization through the cytoplasm (much like the
ripples created by a stone tossed into a pond).
• As the Na+ drifts, some of it will leak back out of the
membrane.
– What this means is that the degree of depolarization caused by
the graded potential decreases with distance from the origin.
27. Graded Potentials
• Their initial amplitude may be of almost any size
– it simply depends on how much Na+ originally
entered the cell.
• If the initial amplitude of the GP is sufficient, it
will spread all the way to the axon hillock where
V-gated channels reside.
• If the arriving potential change is suprathreshold,
an AP will be initiated in the axon hillock and it
will travel down the axon to the synaptic knob
where it will cause NT exocytosis. If the
potential change is subthreshold, then no AP will
ensue and nothing will happen.
28. Action Potentials
• If VM reaches threshold, Na+ channels open and Na+ influx
ensues, depolarizing the cell and causing the VM to
increase. This is the rising phase of an AP.
• Eventually, the Na+ channel will have inactivated and the K+
channels will be open. Now, K+ effluxes and repolarization
occurs. This is the falling phase.
– K+ channels are slow to open and slow to close. This causes the VM
to take a brief dip below resting VM. This dip is the undershoot and
is an example of hyperpolarization.
29.
30. 1
Na Channels
+
• They have 2 gates.
– At rest, one is closed
(the activation gate) and
the other is open (the
inactivation gate).
– Suprathreshold
2
depolarization affects
both of them.
32. Absolute Refractory Period
• During the time interval between the opening of
the Na+ channel activation gate and the opening
of the inactivation gate, a Na+ channel CANNOT
be stimulated.
– This is the ABSOLUTE REFRACTORY PERIOD.
– A Na+ channel cannot be involved in another AP until
the inactivation gate has been reset.
– This being said, can you determine why an AP is said
to be unidirectional.
• What are the advantages of such a scenario?
33. Relative Refractory Period
• Could an AP be generated during the undershoot?
• Yes! But it would take an initial stimulus that is much,
much stronger than usual.
– WHY?
• This situation is known as the relative refractory period.
Imagine, if you will, a toilet.
When you pull the handle, water floods the bowl. This event takes a
couple of seconds and you cannot stop it in the middle. Once the
bowl empties, the flush is complete. Now the upper tank is empty. If
you try pulling the handle at this point, nothing happens (absolute
refractory). Wait for the upper tank to begin refilling. You can now
flush again, but the intensity of the flushes increases as the upper
tank refills (relative refractory)
34. In this figure, what do the red
and blue box represent?
VM
TIME
35. Some Action Potential Questions
• What does it mean when we say an AP is
“all or none?”
– Can you ever have ½ an AP?
• How does the concept of threshold relate
to the “all or none” notion?
• Will one AP ever be bigger than another?
– Why or why not?
36. Action Potential Conduction
• If an AP is generated at the axon hillock, it will
travel all the way down to the synaptic knob.
• The manner in which it travels depends on
whether the neuron is myelinated or
unmyelinated.
• Unmyelinated neurons undergo the continuous
conduction of an AP whereas myelinated
neurons undergo saltatory conduction of an AP.
37. Continuous Conduction
• Occurs in unmyelinated axons.
• In this situation, the wave of de- and repolarization
simply travels from one patch of membrane to the next
adjacent
patch.
• APs moved
in this fashion
along the
sarcolemma
of a muscle
fiber as well.
• Analogous to
dominoes
falling.
38. Saltatory Conduction
• Occurs in myelinated axons.
• Saltare is a Latin word meaning “to leap.”
• Recall that the myelin sheath is not completed. There exist
myelin free regions along the axon, the nodes of Ranvier.
39.
40. Rates of AP Conduction
1. Which do you think has a faster rate of AP
conduction – myelinated or unmyelinated axons?
2. Which do you think would conduct an AP faster –
an axon with a large diameter or an axon with a
small diameter?
The answer to #1 is a myelinated axon. If you can’t see why, then answer this
question: could you move 100ft faster if you walked heel to toe or if you
bounded in a way that there were 3ft in between your feet with each step?
The answer to #2 is an axon with a large diameter. If you can’t see why, then
answer this question: could you move faster if you walked through a hallway
that was 6ft wide or if you walked through a hallway that was 1ft wide?
41. Types of Nerve Fibers
1. Group A
– Axons of the somatic sensory neurons and motor neurons
serving the skin, skeletal muscles, and joints.
– Large diameters and thick myelin sheaths.
• How does this influence their AP conduction?
2. Group B
– Type B are lightly myelinated and of intermediate diameter.
3. Group C
– Type C are unmyelinated and have the smallest diameter.
– Autonomic nervous system fibers serving the visceral organs,
visceral sensory fibers, and small somatic sensory fibers are
Type B and Type C fibers.
42. Now we know how signals get from one end of an axon to the
other, but how exactly do APs send information?
– Info can’t be encoded in AP size, since they’re “all or none.”
In the diagram on
the right, notice
the effect that the
size of the
graded potential
has on the
frequency of AP’s
and on the
quantity of NT
released. The
weak stimulus
resulted in a
small amt of NT
release
compared to the
strong stimulus.
43. Chemical Signals
• One neuron will transmit info to another neuron or to a
muscle or gland cell by releasing chemicals called
neurotransmitters.
• The site of this chemical interplay is known as the synapse.
– An axon terminal (synaptic knob) will abut another cell, a neuron,
muscle fiber, or gland cell.
– This is the site of transduction – the conversion of an electrical
signal into a chemical signal.
44. Synaptic
Transmission
• An AP reaches the
axon terminal of the
presynaptic cell and
causes V-gated Ca2+
channels to open.
• Ca2+ rushes in, binds to
regulatory proteins &
initiates NT exocytosis.
• NTs diffuse across the
synaptic cleft and then
bind to receptors on
the postsynaptic
membrane and initiate
some sort of response
on the postsynaptic
cell.
45. Effects of the Neurotransmitter
• Different neurons can contain different NTs.
• Different postsynaptic cells may contain different
receptors.
– Thus, the effects of an NT can vary.
• Some NTs cause cation channels to open, which
results in a graded depolarization.
• Some NTs cause anion channels to open, which
results in a graded hyperpolarization.
46. EPSPs & IPSPs
• Typically, a single synaptic
interaction will not create a
graded depolarization
strong enough to migrate
to the axon hillock and
induce the firing of an AP.
– However, a graded depolarization will bring the neuronal VM
closer to threshold. Thus, it’s often referred to as an excitatory
postsynaptic potential or EPSP.
– Graded hyperpolarizations
bring the neuronal VM farther away
from threshold and thus are
referred to as inhibitory
postsynaptic potentials or
IPSPs.
47. Summation
• One EPSP is usually
not strong enough
to cause an AP.
• However, EPSPs may
be summed.
• Temporal summation
– The same presynaptic
neuron stimulates the
postsynaptic neuron
multiple times in a brief period. The depolarization
resulting from the combination of all the EPSPs may be
able to cause an AP.
• Spatial summation
• Multiple neurons all stimulate a postsynaptic neuron resulting
in a combination of EPSPs which may yield an AP
48. • Communication btwn
neurons is not typically a
one-to-one event.
– Sometimes a single neuron
branches and its collaterals
synapse on multiple target
neurons. This is known as
divergence.
– A single postsynaptic neuron
may have synapses with as
many as 10,000 postsynaptic
neurons. This is
convergence.
– Can you think of an
advantage to having
convergent and divergent
circuits?
49. • Neurons may also form reverberating
circuits.
• A chain of neurons where many give off collaterals
that go back and synapse on previous neurons.
– What might be a benefit of this arrangement?
50. Neurotransmitter Removal
• Why did we want to
remove ACh from
the neuro- muscular
junction?
• How was ACh
removed from
the NMJ?
• NTs are removed
from the synaptic cleft
via:
– Enzymatic
degradation
– Diffusion
– Reuptake