Book contents
- Frontmatter
- Contents
- List of Abbreviations
- Dedication
- Preface
- A Change in Posture
- Acid-Base
- Action Potentials
- Adrenal Cortex I
- Adrenal Cortex II – Clinical Disorders
- Adrenal Medulla
- Arterial Pressure
- Autonomic Nervous System (ANS)
- Carbon Dioxide Transport
- Cardiac Cycle
- Cardiac Output (CO)
- Cell Signalling
- Cerebrospinal Fluid (CSF) and Cerebral Blood Flow
- Colon
- Control of Ventilation
- Coronary Circulation
- Fetal Circulation
- Glomerular Filtration and Renal Clearance
- Immobilization
- Liver
- Mechanics of Breathing I – Ventilation
- Mechanics of Breathing II – Respiratory Cycle
- Mechanics of Breathing III – Compliance and Elastance
- Mechanics of Breathing IV – Airway Resistance
- Microcirculation I
- Microcirculation II
- Micturition
- Motor Control
- Muscle I – Skeletal and Smooth Muscle
- Muscle II – Cardiac Muscle
- Nutrition: Basic Concepts
- Pancreas I – Endocrine Functions
- Pancreas II – Exocrine Functions
- Potassium Balance
- Proximal Tubule and Loop of Henle
- Pulmonary Blood Flow
- Renal Blood Flow (RBF)
- Respiratory Function Tests
- Small Intestine
- Sodium Balance
- Sodium and Water Balance
- Starvation
- Stomach I
- Stomach II – Applied Physiology
- Swallowing
- Synapses I – The Neuromuscular Junction (NMJ)
- Synapses II – Muscarinic Pharmacology
- Synapses III – Nicotinic Pharmacology
- Thyroid Gland
- Valsalva Manoeuvre
- Venous Pressure
- Ventilation/Perfusion Relationships
Synapses I – The Neuromuscular Junction (NMJ)
Published online by Cambridge University Press: 06 January 2010
- Frontmatter
- Contents
- List of Abbreviations
- Dedication
- Preface
- A Change in Posture
- Acid-Base
- Action Potentials
- Adrenal Cortex I
- Adrenal Cortex II – Clinical Disorders
- Adrenal Medulla
- Arterial Pressure
- Autonomic Nervous System (ANS)
- Carbon Dioxide Transport
- Cardiac Cycle
- Cardiac Output (CO)
- Cell Signalling
- Cerebrospinal Fluid (CSF) and Cerebral Blood Flow
- Colon
- Control of Ventilation
- Coronary Circulation
- Fetal Circulation
- Glomerular Filtration and Renal Clearance
- Immobilization
- Liver
- Mechanics of Breathing I – Ventilation
- Mechanics of Breathing II – Respiratory Cycle
- Mechanics of Breathing III – Compliance and Elastance
- Mechanics of Breathing IV – Airway Resistance
- Microcirculation I
- Microcirculation II
- Micturition
- Motor Control
- Muscle I – Skeletal and Smooth Muscle
- Muscle II – Cardiac Muscle
- Nutrition: Basic Concepts
- Pancreas I – Endocrine Functions
- Pancreas II – Exocrine Functions
- Potassium Balance
- Proximal Tubule and Loop of Henle
- Pulmonary Blood Flow
- Renal Blood Flow (RBF)
- Respiratory Function Tests
- Small Intestine
- Sodium Balance
- Sodium and Water Balance
- Starvation
- Stomach I
- Stomach II – Applied Physiology
- Swallowing
- Synapses I – The Neuromuscular Junction (NMJ)
- Synapses II – Muscarinic Pharmacology
- Synapses III – Nicotinic Pharmacology
- Thyroid Gland
- Valsalva Manoeuvre
- Venous Pressure
- Ventilation/Perfusion Relationships
Summary
1. Outline the stages of synaptic transmission.
The action potential arrives at the presynaptic neurone, which causes the opening of voltage-gated Ca2+-channels concentrated at the presynaptic membrane
There is an influx of Ca2+ into the presynaptic terminal, increasing the intracellular [Ca2+]. This is the trigger for the release of transmitter into the synaptic cleft by exocytosis
Note that the neurotransmitter substance is stored in vesicles found at the nerve terminal. Each vesicle contains a ‘quantum’ of transmitter molecules
The neurotransmitter diffuses across the synaptic cleft, and binds onto specific receptor proteins located on the postsynaptic membrane
An action potential is generated in the postsynaptic cell
The transmitter substance is degraded, and its component parts may be recycled through uptake at the presynatic nerve terminal
2. What are the names for the changes in membrane potential caused by binding of the transmitter to the synaptic receptors?
These transient changes in the membrane potential are called ‘synaptic potentials’. A transient depolarisation of the postsynaptic cell is an ‘excitatory postsynaptic potential’ (EPSP). Similarly a transient hyperpolarisation is termed ‘inhibitory postsynaptic potential’ (IPSP).
3. What is meant by the terms ‘temporal’ and ‘spatial’ summation when referring to excitation of the postsynaptic membrane?
If the EPSP triggered by receptor binding is of sufficient magnitude, an action potential is triggered, withan influx of Na+ or Ca2+. This build up of EPSPs at the postsynaptic membrane is called ‘summation’. It may occur through two mechanisms:
Temporal summation: a rapid train of impulses from a single presynaptic cell causes EPSPs to add up, triggering an action potential in the postsynaptic cell
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- Applied Surgical Physiology Vivas , pp. 158 - 160Publisher: Cambridge University PressPrint publication year: 2004