Nerves and Muscles Flashcards
______
- Structural and functional unit of nervous system
NEURON (NERVE CELL)
NEURON (NERVE CELL)
- ______ cells
Excitable
______
- Specialized cells that transmit chemical and electrical signals to facilitate communication between the brain and the body.
NEURON (NERVE CELL)
NEURON (NERVE CELL)
- Have ______ and all the ______ in cytoplasm.
nucleus, organelles
NEURON (NERVE CELL)
- More than ______ neurons in the human brain
10^12
NEURON (NERVE CELL)
Different from other cells by two ways:
Neuron has branches or processes called ______ and ______
axon, dendrites
NEURON (NERVE CELL)
Different from other cells by two ways:
Neuron does not have ______. So, it cannot undergo ______
centrosome, division
Neurons come in many different ______ and ______.
shapes, sizes
______
- Has the Ability to receive, process, integrate, and transmit information from external and internal sources to initiate most physiological behavior
NEURON (NERVE CELL)
______
- Produce sensation, thought, learning, movement, emotion, and many other processes.
NEURON (NERVE CELL)
NEURONS
Use ______ to transmit information within a single cell and ______ between cells.
electrical signals, chemical signals
At birth, the human brain consists of an estimated ______ neurons. Unlike other cells, neurons don’t ______ or ______. They are replaced by ______ only.
100 billion, reproduce, regenerate, neuroglia
BASIC COMPONENTS OF NEURON:
CELL BODY (SOMA/PERIKARYON)
DENDRITES
AXON
BASIC COMPONENTS OF NEURON:
______
- Contains the nucleus and DNA
CELL BODY (SOMA/PERIKARYON)
BASIC COMPONENTS OF NEURON:
______
- Multiple, short processes that extend outward from the cell body
DENDRITES
BASIC COMPONENTS OF NEURON:
______
- Contain Nissl bodies and neurofibrillae
DENDRITES
BASIC COMPONENTS OF NEURON:
DENDRITES
- “______” - receiving signals from other neurons via their synapses with axon terminals
Receptive Processes
BASIC COMPONENTS OF NEURON:
DENDRITES
Receptive Processes
- ______ - basophilic granules
Nissl Bodies
BASIC COMPONENTS OF NEURON:
DENDRITES
Receptive Processes
- ______ - consist of microfilament and microtubules
Neurofibrillae
BASIC COMPONENTS OF NEURON:
______
- Single, long process
AXON
BASIC COMPONENTS OF NEURON:
AXON
- Originates from a ______ of the cell body (______).
thickened area, axon hillock
BASIC COMPONENTS OF NEURON:
AXON
- The first portion of the axon is called the ______.
initial segment
BASIC COMPONENTS OF NEURON:
AXON
- Divides into ______ each ending in ______ that are also called ______.
presynaptic terminals, synaptic knobs, terminal buttons or boutons
BASIC COMPONENTS OF NEURON:
AXON
- ______ - cell membrane
Axolemma
BASIC COMPONENTS OF NEURON:
AXON
- ______ - cytoplasm
Axoplasm
BASIC COMPONENTS OF NEURON:
AXON
- ______ - A protein–lipid complex wrapped around the axon produced by Schwann cell
______ Neuron
______ Neuron
Myelin Sheath
Myelinated
Non-myelinated
BASIC COMPONENTS OF NEURON:
AXON
- ______ - gaps between two segments
Node of Ranvier
______
- Supporting cells present within the brain and spinal cord.
- Numerous
Neuroglia
NEUROGLIA TYPES:
MACROGLIA
MICROGLIA
NEUROGLIA TYPES:
______
- Large glial cells; ______ in origin.
- ______ (fibrous and protoplasmic astrocytes)
- ______.
MACROGLIA, ectodermal, Astrocytes, Oligodendrocytes
NEUROGLIA TYPES:
MICROGLIA
- Small glial cells; ______ in origin.
- More numerous in ______
- Act as ______
mesodermal, grey matter, phagocytes
Classification of Neurons
Based on functions:
SENSORY
MOTOR
Classification of Neurons
Based on functions:
SENSORY
- “______ nerve cells”
Afferent
Classification of Neurons
Based on functions:
______
- Carry sensory impulses from the periphery to the CNS.
SENSORY
Classification of Neurons
Based on functions:
______
- Short axon and long dendrites.
SENSORY
Classification of Neurons
Based on functions:
MOTOR
- “______ nerve cells”
Efferent
Classification of Neurons
Based on functions:
______
- Carry motor impulses from the CNS to the peripheral effector organs
MOTOR
Classification of Neurons
Based on functions:
______
- Very long axon and short dendrites.
MOTOR
Classification of Neurons
Based on the number of processes that emanate from their cell body:
Unipolar Cell
Bipolar Cell
Pseudounipolar Cell
Multipolar Cells
Classification of Neurons:
UNIPOLAR NEURONS
BIPOLAR NEURONS
PSEUDONIPOLAR CELLS
MULTIPOLAR CELLS
Classification of Neurons:
______
- One process, with different segments serves as receptive surface and releasing terminals.
UNIPOLAR NEURONS
Classification of Neurons:
______
- Two specialized processes:
______ that carries information to the cell
______ that transmits information from the cell.
BIPOLAR NEURONS, Dendrite, Axon
Classification of Neurons:
______
- Some sensory neurons are in a subclass of bipolar cells
PSEUDONIPOLAR CELLS
Classification of Neurons:
______
- A single process splits into two, function as axons:
One going to skin or muscle
Another to the spinal cord
PSEUDONIPOLAR CELLS
Classification of Neurons:
______
- One axon and many dendrites.
MULTIPOLAR CELLS
Classification of Neurons:
______
- e.g motor neurons, hippocampal pyramidal cells, and cerebellar Purkinje cells
MULTIPOLAR CELLS
NEURON
Four Important Zones:
(1) A dendritic zone
(2) Site where action potentials are generated
(3) Axonal process
(4) Nerve endings
NEURON
Four Important Zones:
______
- Multiple local potential changes generated by synaptic connections are integrated;
A dendritic zone
NEURON
Four Important Zones:
______
- Initial segment in spinal motor neurons, the initial node of Ranvier in cutaneous sensory neurons
Site where action potentials are generated
NEURON
Four Important Zones:
______
- Transmits propagated impulses to the nerve endings;
Axonal process
NEURON
Four Important Zones:
______
- Action potentials cause the release of synaptic transmitters.
Nerve endings
______
- Property of nerve fibers
EXCITABILITY
______
- Response by generating a nerve signal when it is stimulated by a stimulus (______, ______, ______ or ______)
EXCITABILITY, mechanical, thermal, chemical, electrical
______
- Production of action potential
EXCITABILITY
______
- An active, self-propagating process
CONDUCTION
______
- Impulse moves along the nerve at a constant amplitude and velocity normally transmitted (______) along the axon to its termination.
CONDUCTION, conducted
CONDUCTION
- Neurons produce ______ or ______ potentials reflecting changes in the conduction of ions across the cell membrane.
nonpropagated, propagated
CONDUCTION
______ (______) potentials (Based on ______)
- Synaptic, generator, or electrotonic potentials
Nonpropagated, local, location
CONDUCTION
______ action potentials
- Primary electrical response and main form of communication
Propagated
Neurons send messages ______.
electrochemically
Chemicals in the body are “______” called ______.
electrically-charged, ions
______ caused when different ions cross the neuron membrane.
Action potential
Important ions in the nervous system
- ______ and ______ (both have 1 positive charge,+)
Sodium, potassium
Important ions in the nervous system
- ______ (has 2 positive charges,++)
Calcium
Important ions in the nervous system
- ______ (has a negative charge,-)
Chloride
Nerve cells are surrounded by a semi-permeable membrane that ______ some ions to pass through and ______ the passage of other ions.
allows, blocks
Action Potential process:
- Resting state
- Depolarising phase
- Repolarising phase begins
- Repolarising phase continues
______ is crucial for: Nerve function, Skeletal muscle function, Smooth muscle function, Heart function
Potassium homeostasis
______
- High potassium level in blood
Hyperkalemia
______
- Often caused by: Impaired kidney excretion due to renal failure, Adrenal insufficiency, Certain medical conditions
Hyperkalemia
______
- Symptoms: Muscle pain, Weakness, Cardiac arrhythmias, Nausea
Hyperkalemia
______
- Can lead to cardiac arrest and death
Severe hyperkalemia
______
- Rare genetic disorder
Hyperkalemic periodic paralysis (HYPP)
______
- Causes muscle paralysis due to high potassium levels
Hyperkalemic periodic paralysis (HYPP)
______
- Muscle membrane potential shifts, inactivating sodium channels and preventing action potential generation
Hyperkalemic periodic paralysis (HYPP)
______
- Lower than normal potassium level in the bloodstream
Hypokalemia
______
- Commonly caused by: Increased excretion of potassium (K+), Shift of potassium from extracellular to intracellular space
Hypokalemia
______
- Other causes: Rare genetic disorders (Bartter syndrome, Gitelman syndrome), Cushing syndrome, Potassium-wasting diuretics, Diabetic ketoacidosis, Renal tubular acidosis, Familial
Hypokalemia
______
- symptoms: Weakness, Fatigue, Constipation, Muscle cramping, Palpitations
Hypokalemia
______
- Psychological symptoms: Depression, Psychosis
Hypokalemia
Severe hypokalemia (below ______ mEq/L)
2.5
______
- Can lead to cardiac rhythm issues: Bradycardia, Tachycardia, Premature beats, Atrial or ventricular fibrillation
Severe hypokalemia
______
- Axoplasm, the cytoplasm of the neurons is in constant ______. The ______ is vital to nerve cell functions, since movements of various materials occur through it.
AXOPLASMIC TRANSPORT, motion, axoplasmic transport
The axoplasmic transport is of two types:
Anterograde transport
Retrograde transport
The axoplasmic transport is of two types:
______, i.e. transport of materials away from the cell body. Some materials travel ______-______mm a day along the axoplasm. ______ play an important role in this form of transport.
Anterograde transport, 100, 400, Microtubules
The axoplasmic transport is of two types:
______, i.e. axoplasmic flow towards the cell body, may also carry tetanus toxin and neurotropic viruses (e.g. polio, herpes simplex and rabies) along the axon into the neuronal cell bodies in the CNS. It has also been employed by the neuroanatomists for charting out neural pathways.
Retrograde transport
An ______ (from Greek, ______), or nerve fiber is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action potentials away from the nerve cell body.
axon, axis
PARTS OF A NERVE FIBER:
Axon
Myelin Sheath
Nodes of Ranvier
Endoneurium
Perineurium
Epineurium
Axolemma
Axoplasm
PARTS OF A NERVE FIBER:
______: The central component of a nerve fiber, responsible for transmitting electrical impulses.
Axon
PARTS OF A NERVE FIBER:
______: A protective, insulating layer around the axon (found in ______ fibers) that increases the speed of nerve signal transmission. It is formed by ______ in the peripheral nervous system or ______ in the central nervous system
Myelin Sheath, myelinated, Schwann cells, oligodendrocytes
Some nerve fibers have no Myelin Sheath and are called ______.
Non-Myelinated Nerve Fibers
PARTS OF A NERVE FIBER:
______: Gaps in the myelin sheath along the axon, allowing for the rapid transmission of electrical signals via a process called ______.
Nodes of Ranvier, saltatory conduction
PARTS OF A NERVE FIBER:
______: A delicate connective tissue sheath surrounding each individual nerve fiber.
Endoneurium
PARTS OF A NERVE FIBER:
______, a layer of dense connective tissue that encloses a fascicle of nerve fibers, providing an effective barrier against penetration of the nerve fibers by foreign substances.
Perineurium
PARTS OF A NERVE FIBER:
______, a thick connective tissue sheath that surrounds and encloses a bundle of fascicles, forming the outermost covering of the nerve; it includes fatty tissue, blood vessels, and lymphatics.
Epineurium
PARTS OF A NERVE FIBER:
______: The outer membrane of the axon that maintains the electrical signal within the nerve fiber.
Axolemma
PARTS OF A NERVE FIBER:
______: The cytoplasm of the axon, which contains essential organelles and nutrients for axonal function and transport.
Axoplasm
______ fibers: Faster, insulated, used in rapid signal pathways.
Myelinated
______ fibers: Slower, lack insulation, used in slower or more steady processes.
Non-myelinated
MYELINATED NERVE FIBERS
Myelin Sheath: These fibers are wrapped in a fatty insulating layer called ______, produced by ______ in the peripheral nervous system (PNS) or ______ in the central nervous system (CNS).
myelin, Schwann cells, oligodendrocytes
MYELINATED NERVE FIBERS
Conduction Speed: The presence of myelin allows for ______ transmission of nerve impulses through a process called ______, where the electrical signal jumps from one ______ (gaps in the myelin sheath) to another.
faster, saltatory conduction, Node of Ranvier
MYELINATED NERVE FIBERS
Appearance: Myelinated fibers appear ______, which is why areas rich in these fibers are referred to as “______” in the brain and spinal cord.
white, white matter
MYELINATED NERVE FIBERS
Function: These fibers are typically found in pathways that require ______ transmission of signals, such as motor neurons and sensory neurons involved in ______ and ______.
rapid, touch, proprioception
NON-MYELINATED NERVE FIBERS
Lack of Myelin: These fibers do not have a myelin sheath, meaning the electrical signal travels continuously along the ______.
axon
NON-MYELINATED NERVE FIBERS
Conduction Speed: Signal transmission is ______ compared to myelinated fibers, as the impulse does not “______” but rather moves more gradually.
slower, jump
NON-MYELINATED NERVE FIBERS
Appearance: Non-myelinated fibers appear ______, contributing to what is called “______” in the nervous system.
gray, gray matter
NON-MYELINATED NERVE FIBERS
Function: Non-myelinated fibers are often involved in ______ processes, such as ______ (e.g., digestion) or ______ (C fibers).
slower, autonomic functions, pain transmission
PROPERTIES OF NERVE FIBERS: (7)
Excitability
Conductivity
Refractive period
Unfatiguability
All or none response
Accommodation
Summation
PROPERTIES OF NERVE FIBERS:
______:
• Nerve fibers are highly excitable tissues
Excitability
PROPERTIES OF NERVE FIBERS:
______:
• Respond to various stimulus
Excitability
PROPERTIES OF NERVE FIBERS:
______:
• Capable of generating electrical impulses
Excitability
PROPERTIES OF NERVE FIBERS:
______:
• Action potential is generated in the nerve fibers, which travels along its entire length to axon terminal
Conductivity
PROPERTIES OF NERVE FIBERS:
______:
• During action potential excitability of nerve becomes reduced
Refractive period
PROPERTIES OF NERVE FIBERS:
______:
• i-e a new impulse can not be generated during action potential
Refractive period
PROPERTIES OF NERVE FIBERS:
______:
• Nerve fibers can not be fatigued even when they are stimulated continuously.
Unfatiguability
PROPERTIES OF NERVE FIBERS:
______:
• Either all of action potential is seen or none at all
All or none response
PROPERTIES OF NERVE FIBERS:
______:
• If a stimulus of threshold strength is applied, action potential will be generated.
All or none response
PROPERTIES OF NERVE FIBERS:
______:
• Further increase in strength of stimulus or duration has no effect on amplitude of action potential but can effect frequency.
All or none response
PROPERTIES OF NERVE FIBERS:
______:
• Application of continuous stimuli may decrease the excitability of nerve fibers.
Accommodation
PROPERTIES OF NERVE FIBERS:
______:
• Application of sub threshold stimulus (a stimulus which is too small to produce action potential) does not evoke an action potential. However if sub threshold stimuli are applied in rapid succession they are added and they produce an action potential.
Summation
The ______ is the junction where neurons trade intormation. It is not a physical component of a cell but rather a name for the gap between two cells.
• the ______ (giving the signal) and the ______ (receiving the signal).
• There are two types of possible reactions at the synapse ______ or ______.
synapse, presynaptic cell, postsynaptic cell, chemical, electrical
SYNAPSE REACTION:
• During a ______ reaction, a chemical called a neurotransmitter is released from one cell into another.
chemical
SYNAPSE REACTION:
• In an ______ reaction, the electrical charge of one cell is influenced by the charge an adjacent cell.
electrical
SYNAPSE REACTION
______ are chemicals that transmit signals from a neuron across a synapse to a target cell.
Neurotransmitters
CHEMICAL REACTION
• In a chemical synapse, ______ affect other neurons via a gap between neurons called a ______. Synapses consist of a ______, a ______, and a ______.
action potentials, synapse, presynaptic ending, synaptic cleft, postsynaptic ending
CHEMICAL REACTION
• When an action potential is generated, it’s carried along the axon to a ______. This triggers the release of chemical messengers called ______. These molecules cross the ______ and bind to receptors in the ______ of a dendrite.
presynaptic ending, neurotransmitters, synaptic cleft, postsynaptic ending
CHEMICAL REACTION
• Neurotransmitters can ______ the postsynaptic neuron, causing it to generate an action potential of its own. Alternatively, they can ______ the postsynaptic neuron, in which case it doesn’t generate an action potential.
excite, inhibit
ELECTRICAL REACTION
• Electrical synapses can only ______. They occur when two neurons are connected via a ______. This gap is much ______ than a synapse, and includes ion channels which facilitate the direct transmission of a ______ electrical signal. As a result, electrical synapses are much ______ than chemical synapses. However, the signal diminishes from one neuron to the next, making them less ______ at transmitting.
excite, gap junction, smaller, positive, faster, effective
SYNAPSES COMMON CHARACTERISTICS:
Presynaptic cell
Synaptic cleft
G-protein coupled receptors
Ligand-gated ion channels
Postsynaptic cell
SYNAPSES COMMON CHARACTERISTICS:
• ______: a specialized area within the axon of the giving cell that transmits information to the dendrite of the receiving cell.
Presynaptic cell
SYNAPSES COMMON CHARACTERISTICS:
• ______: the small space at the synapse that receives neurotransmitters.
Synaptic cleft
SYNAPSES COMMON CHARACTERISTICS:
• ______: receptors that sense molecules outside the cell and thereby activate signals within it.
G-protein coupled receptors
SYNAPSES COMMON CHARACTERISTICS:
• ______: receptors that are opened or closed in response to the binding of a chemical messenger.
Ligand-gated ion channels
SYNAPSES COMMON CHARACTERISTICS:
• ______: a specialized area within the dendrite of the receiving cell that is designed to process neurotransmitters.
Postsynaptic cell
Muscle cells can be excited ______, ______, and ______
chemically, electrically, mechanically
Muscle cells produce an ______ transmitted along their cell membranes
action potential
Muscle cells activate a ______ in response to stimuli
contractile mechanism
______ and ______ are abundant in muscle cells
Myosin, actin
______ and ______ are the primary structural components that bring about contraction
Myosin, actin
Muscle Types:
Skeletal Muscle
Cardiac Muscle
Smooth Muscle
Muscle Types:
______:
- Makes up somatic musculature
Skeletal Muscle
Muscle Types:
______:
- Cross-striations present
Skeletal Muscle and Cardiac Muscle
Muscle Types:
______:
- Requires nervous stimulation to contract
Skeletal Muscle
Muscle Types:
______:
- Lacks connections between individual fibers
Skeletal Muscle
Muscle Types:
______:
- Voluntary control
Skeletal Muscle
Muscle Types:
______:
- Functionally syncytial (cells connected, act as one unit)
Cardiac Muscle
Muscle Types:
______:
- Can contract rhythmically without external innervation due to pacemaker cells
Cardiac Muscle
Muscle Types:
______:
- Lacks cross-striations
Smooth Muscle
Muscle Types:
Smooth Muscle:
- Two types:
______: Functionally syncytial with irregular pacemakers
______: Not spontaneously active, resembles skeletal muscle in graded contractile ability
Unitary
Multiunit
SKELETAL MUSCLES
- consists of ______ (building blocks of the muscular system).
individual muscle fibers
SKELETAL MUSCLES
- fibers are arranged in ______ between ______, allowing additive force during contraction.
parallel, tendinous ends
SKELETAL MUSCLES
- each fiber is a ______, ______, ______ cell surrounded by a ______ (cell membrane).
multinucleated, long, cylindrical, sarcolemma
SKELETAL MUSCLES
- fibers are composed of ______, divided into ______, containing proteins like ______ and ______ that drive contraction.
myofibrils, myofilaments, myosin, actin
SKELETAL MUSCLE
STRIATIONS
______ of the parts of the skeletal muscle fibers have differences, which is why there are ______ seen when viewed under the microscope.
Refractive indexes, cross-striations
SKELETAL MUSCLE
STRIATIONS
The parts of the cross-striations are frequently identified by letters ______, ______, ______, ______, and ______.
A, H, I, M, Z
SKELETAL MUSCLE
STRIATIONS
The area between two adjacent Z-lines is called a ______.
sarcomere
SKELETAL MUSCLE
CONTRACTILE MACHINERY AND PROTEINS
Key proteins for contraction are ______, ______, ______, and ______ (______, ______, and ______).
myosin-II, actin, tropomyosin, troponin, troponin I, T, C
SKELETAL MUSCLE
CONTRACTILE MACHINERY AND PROTEINS
Additional structural proteins include ______ (binds actin to Z-lines), ______ (largest known protein, connects the Z-lines to the M-lines, provides scaffolding for the sarcomere, and provides muscle elasticity through its two kinds of folded domains), and ______ (binds Z-lines to the plasma membrane).
actinin, titin, desmin
SKELETAL MUSCLE
ELECTRICAL CHARACTERISTICS OF SKELETAL MUSCLE
Skeletal muscle electrical events are similar to nerve cells, with some differences:
Resting membrane potential: ______.
−90 mV
SKELETAL MUSCLE
ELECTRICAL CHARACTERISTICS OF SKELETAL MUSCLE
Skeletal muscle electrical events are similar to nerve cells, with some differences:
Action potential duration: ______, conducted at ______.
2-4 ms, 5 m/s
SKELETAL MUSCLE
ELECTRICAL CHARACTERISTICS OF SKELETAL MUSCLE
Skeletal muscle electrical events are similar to nerve cells, with some differences:
Refractory period: ______.
1-3 ms
SKELETAL MUSCLE
ELECTRICAL CHARACTERISTICS OF SKELETAL MUSCLE
Ionic fluxes: Depolarization driven by ______ and repolarization by ______.
Na+ influx, K+ efflux
SKELETAL MUSCLE
CONTRACTION
Muscle contraction involves both ______ (action potentials) and ______ events.
electrical, mechanical
SKELETAL MUSCLE
CONTRACTION
Depolarization begins at the ______ and triggers ______, leading to contraction.
motor endplate, Ca²⁺ influx
SKELETAL MUSCLE
CONTRACTION
A ______ is a brief contraction followed by ______, initiated by a single action potential.
muscle twitch, relaxation
SKELETAL MUSCLE
CONTRACTION
Twitch starts about ______ after membrane depolarization.
2ms
SKELETAL MUSCLE
CONTRACTION
Duration varies between “______” (______) and “______” (up to ______) muscle fibers.
fast, 7.5ms, slow, 100ms
SKELETAL MUSCLE
CONTRACTION
Contraction is due to the ______, increasing overlap.
sliding of thin filaments over thick filaments
SKELETAL MUSCLE
CONTRACTION
Myosin heads bind to ______, undergo a ______, and ______ in a cycle driven by ______.
actin, power stroke, detach, ATP hydrolysis
SKELETAL MUSCLE
CONTRACTION
______ and available ______ sustain this contraction cycle.
Elevated cytosolic Ca²⁺, ATP
SKELETAL MUSCLE
CONTRACTION
Depolarization initiates contraction by triggering ______ release from the ______ via ______.
Ca²⁺, sarcoplasmic reticulum, T-tubules
SKELETAL MUSCLE
CONTRACTION
The process by which membrane depolarization of the muscle fiber initiates contraction is called ______.
excitation–contraction coupling
SKELETAL MUSCLE
CONTRACTION
______ (______) in T-tubules activate ______ (______), causing Ca²⁺ release.
Dihydropyridine receptors, DHPR, ryanodine receptors, RyR
SKELETAL MUSCLE
CONTRACTION
______ is reduced in the muscle cell by the sarcoplasmic or endoplasmic reticulum ______ (______).
Cytosolic Ca2+ concentration, Ca2+ ATPase, SERCA
SKELETAL MUSCLE
CONTRACTION
The ______ uses energy from ATP hydrolysis to remove Ca2+ from the cytosol back into the ______ against its concentration gradient, where it is stored until released by the next action potential.
SERCA pump, terminal cisterns
SKELETAL MUSCLE
CONTRACTION
If transport of Ca2+ into the sarcoplasmic reticulum is inhibited, relaxation does not occur; the resulting sustained contraction is called a ______.
contracture
SKELETAL MUSCLE
CONTRACTION
TYPES OF MUSCLE CONTRACTION:
Isometric Contraction
Isotonic Contraction
SKELETAL MUSCLE
CONTRACTION
TYPES OF MUSCLE CONTRACTION:
______ (“same measure” or length): Muscle generates tension without shortening.
Isometric Contraction
SKELETAL MUSCLE
CONTRACTION
TYPES OF MUSCLE CONTRACTION:
______ (“same tension”): Muscle shortens while maintaining constant tension.
Isotonic Contraction
SKELETAL MUSCLE
STEPS IN CONTRACTION:
1 Discharge of motor neuron
2 Release of transmitter (acetylcholine) at motor endplate
3 Binding of acetylcholine to nicotinic acetylcholine receptors
4 Increased Na+ and K+ conductance in endplate membrane
5 Generation of endplate potential
6 Generation of action potential in muscle fibers
7 Inward spread of depolarization along T tubules
8 Release of Ca2+ from terminal cisterns of sarcoplasmic reticulum and diffusion to thick and thin filaments
9 Binding of Ca2+ to troponin C, uncovering myosin-binding sites on actin
10 Formation of cross-linkages between actin and myosin and sliding of thin on thick filaments, producing movement
SKELETAL MUSCLE
STEPS IN RELAXATION:
1 Ca2+ pumped back into sarcoplasmic reticulum
2 Release of Ca2+ from troponin
3 Cessation of interaction between actin and myosin
SKELETAL MUSCLE
SUMMATION OF CONTRACTIONS AND TETANUS
Repeated stimulation leads to ______, where contractions add together for a stronger response.
summation
SKELETAL MUSCLE
SUMMATION OF CONTRACTIONS AND TETANUS
With rapidly repeated stimulation, activation of the contractile mechanism occurs repeatedly before any relaxation has occurred, and the individual responses fuse into one continuous contraction. Such a response is called ______ (______).
tetanus, tetanic contraction
SKELETAL MUSCLE
SUMMATION OF CONTRACTIONS AND TETANUS
______: Partial relaxation between stimuli.
Incomplete Tetanus
SKELETAL MUSCLE
SUMMATION OF CONTRACTIONS AND TETANUS
______: No relaxation, leading to continuous contraction and maximum tension.
Complete Tetanus
SKELETAL MUSCLE
MUSCLE CONTRACTION DYNAMICS:
Total tension
Passive tension
Active tension
Optimal resting length
SKELETAL MUSCLE
MUSCLE CONTRACTION DYNAMICS
______: the tension that a muscle develops when stimulated to contract isometrically
Total tension
SKELETAL MUSCLE
MUSCLE CONTRACTION DYNAMICS
______: the tension exerted by the unstimulated muscle
Passive tension
SKELETAL MUSCLE
MUSCLE CONTRACTION DYNAMICS
______: the difference between total and passive tension at any length, the amount of tension actually generated by the contractile process
Active tension
SKELETAL MUSCLE
MUSCLE CONTRACTION DYNAMICS
______: The length of the muscle at which the active tension is maximal.
Optimal resting length
SKELETAL MUSCLE
ENERGY SOURCES FOR MUSCLE CONTRACTION:
ATP
Phosphorylcreatine
SKELETAL MUSCLE
ENERGY SOURCES FOR MUSCLE CONTRACTION
______: Primary energy source, generated from carbohydrates and lipids.
ATP
SKELETAL MUSCLE
ENERGY SOURCES FOR MUSCLE CONTRACTION
______: Hydrolyzed to resynthesize ATP and provides short-term energy during exercise.
Phosphorylcreatine
SKELETAL MUSCLE
MUSCLE FIBERS
Skeletal Muscle: made up of ______ tissue composed of fibers that vary in myosin ATPase activity, contractile speed, and other properties
heterogeneous
SKELETAL MUSCLE
MUSCLE FIBERS
frequently classified into “______” and “______”, and contain a mixture of three fiber types:
Type I: ______
Type IIA: ______
Type IIB: ______
slow, fast, Slow-oxidative (SO), Fast-oxidative glycolytic (FOG), Fast glycolytic (FG)
SKELETAL MUSCLE
MUSCLE FIBERS
______ (______): 10 isoforms characterized.
Myosin Heavy Chains, MHCs
______
- striated muscle found only in the walls of the heart (______) and in some of the large vessels close to where they join the heart.
CARDIAC MUSCLE, myocardium
CARDIAC MUSCLE
- consists of a branching network of individual cells linked ______ and ______ to work as a unit.
electrically, mechanically
CARDIAC MUSCLE
- contractions are ______ than those of skeletal muscle and it is resistant to fatigue.
less powerful
CARDIAC MUSCLE
MORPHOLOGY
The striations in cardiac muscle are similar to those in ______, and ______ are present.
skeletal muscle, Z- lines
CARDIAC MUSCLE
MORPHOLOGY
______ provide a strong union between fibers, maintaining cell-to-cell cohesion, so that the pull of one contractile cell can be transmitted along its axis to the next.
Intercalated disks
CARDIAC MUSCLE
MORPHOLOGY
______ provide low-resistance bridges for the spread of excitation from one fiber to another.
Gap Junctions
CARDIAC MUSCLE
MORPHOLOGY
______ permit cardiac muscle to function as if it were a ______, even though no protoplasmic bridges are present between cells.
Gap Junctions, syncytium
CARDIAC MUSCLE
MORPHOLOGY
The ______ in cardiac muscle is located at the ______ rather than at the A–I junction, where it is located in mammalian skeletal muscle.
T system, Z-lines
CARDIAC MUSCLE
ELECTRICAL PROPERTIES
RESTING MEMBRANE & ACTION POTENTIALS
action potentials vary among the ______ in different regions of the heart (29 check), the action potential of a typical ______ can be used as an example
cardiomyocytes, ventricular cardiomyocyte
CARDIAC MUSCLE
ELECTRICAL PROPERTIES
RESTING MEMBRANE & ACTION POTENTIALS
______ proceeds rapidly and an overshoot of the zero potential is present, as in skeletal muscle and nerve, but this is followed by a ______ before the membrane potential returns to the baseline.
Depolarization, plateau
CARDIAC MUSCLE
ELECTRICAL PROPERTIES
RESTING MEMBRANE & ACTION POTENTIALS
______ is therefore not complete until the contraction is half over.
Repolarization
CARDIAC MUSCLE
ELECTRICAL PROPERTIES
RESTING MEMBRANE & ACTION POTENTIALS
As in other excitable tissues, changes in the ______ affect the resting membrane potential of cardiac muscle, whereas changes in the ______ affect the magnitude of the action potential.
external K+ concentration, external Na+ concentration
CARDIAC MUSCLE
ELECTRICAL PROPERTIES
RESTING MEMBRANE & ACTION POTENTIALS
The ______ and the ______ (______) are due to opening of voltage-gated Na+ channels similar to that occurring in nerve and skeletal muscle
initial rapid depolarization, overshoot, phase 0
CARDIAC MUSCLE
ELECTRICAL PROPERTIES
RESTING MEMBRANE & ACTION POTENTIALS
The ______ (______) is due to closure of Na+ channels and opening of one type of K+ channel
initial rapid repolarization, phase 1
CARDIAC MUSCLE
ELECTRICAL PROPERTIES
RESTING MEMBRANE & ACTION POTENTIALS
The subsequent prolonged ______ (______) is due to a slower but prolonged opening of voltage-gated Ca2+ channels.
plateau, phase 2
CARDIAC MUSCLE
ELECTRICAL PROPERTIES
RESTING MEMBRANE & ACTION POTENTIALS
______ (______) to the ______ (______) is due to closure of the Ca2+ channels and a slow, delayed increase of K+ efflux through various types of K+ channels.
Final repolarization, phase 3, resting membrane potential, phase 4
CARDIAC MUSCLE
ELECTRICAL PROPERTIES
RESTING MEMBRANE & ACTION POTENTIALS
______ contain at least two types of voltage-gated Ca2+ channels (______), but the Ca2+ current is mostly due to opening of the slower ______ Ca2+ channels.
Cardiac myocytes, T- and L-types, L-type
CARDIAC MUSCLE
______ (______) is defined as a prolongation of the QT interval observed on an electrocardiogram. It can lead to irregular heartbeats and subsequent fainting, seizure, cardiac arrest, or even death.
Long QT syndrome, LQTS
CARDIAC MUSCLE
______
- more frequently associated with genetic mutations in a variety of cardiac-expressed ion channels.
LONG QT SYNDROME
CARDIAC MUSCLE
MECHANICAL PROPERTIES
CONTRACTILE RESPONSE
The ______ of cardiac muscle begins
just after the start of depolarization and lasts about ______ times as long as the action potential
contractile response, 1.5
CARDIAC MUSCLE
MECHANICAL PROPERTIES
CONTRACTILE RESPONSE
The role of Ca2+ in ______ is similar to its role in skeletal muscle.
excitation–contraction coupling
CARDIAC MUSCLE
MECHANICAL PROPERTIES
CONTRACTILE RESPONSE
However, it is the influx of ______ through the ______ or ______ in the ______ that triggers Ca2+-induced Ca2+ release through the RyR at the sarcoplasmic reticulum.
extracellular Ca2+, voltage-sensitive DHPR, voltage-gated Ca2+ channels, T system
CARDIAC MUSCLE
______ drugs like ______ increase cardiac contraction by inhibiting Na, K ATPase in cardiomyocytes. This leads to increased intracellular Na+, decreased Na+ and Ca2+ transportation, and increased intracellular Ca2+. While effective, excessive inhibition can cause toxicity, including depolarization and arrhythmias.
Glycosidic, ouabain
______
- are non-striated muscles
SMOOTH MUSCLES
______
- are characterized by absence of the typical cross-striated pattern seen in the skeletal muscles.
SMOOTH MUSCLES
______
- involuntary muscles, because of their activity through the autonomic nervous system
SMOOTH MUSCLES
Smooth muscle cells are ______ and ______, grouped into bundles or ______, which form layers of varying thickness. These muscles can exist as sheets or bundles
Each cells arranged with thick ______ of one cell opposite the thin ends of adjacent cells.
long, fusiform, fasciculi, central parts
SMOOTH MUSCLE
TYPES OF SMOOTH MUSCLE:
SINGLE UNIT SMOOTH MUSCLES
MULTIUNIT SMOOTH MUSCLES
SMOOTH MUSCLE
TYPES OF SMOOTH MUSCLE
______ SMOOTH MUSCLES
- Also called visceral smooth muscles
SINGLE UNIT
SMOOTH MUSCLE
TYPES OF SMOOTH MUSCLE
______ SMOOTH MUSCLES
- They are present in the walls of hollow viscera such as such as ______, and ______.
SINGLE UNIT, gastrointestinal tract, respiratory tract
SMOOTH MUSCLE
TYPES OF SMOOTH MUSCLE
______ SMOOTH MUSCLES
- Are made up of multiple individual units without interconnecting bridges, i.e. ______ in character.
MULTIUNIT, non-syncytial
SMOOTH MUSCLE
TYPES OF SMOOTH MUSCLE
MULTIUNIT SMOOTH MUSCLES
- These are located in most ______, ______, ______ and ______.
blood vessels, iris, ciliary body, piloerector muscles
SMOOTH MUSCLE
ELECTRICAL & MECHANICAL ACTIVITY
______ Smooth Muscle
- Exhibits an unstable membrane potential with no true resting value. It is less negative when the tissue is ______ and more negative when ______.
Unitary, active, inhibited
SMOOTH MUSCLE
ELECTRICAL & MECHANICAL ACTIVITY
______ Smooth Muscle
- Shows continuous, irregular contractions independent of nerve supply, known as ______.
Unitary, tonus
SMOOTH MUSCLE
ELECTRICAL & MECHANICAL ACTIVITY
______ Smooth Muscle
- Electrical Activity features slow sine wave-like fluctuations and spikes that may exceed ______. Spikes last about ______, with some tissues displaying prolonged plateau phases during repolarization
Unitary, zero potential, 50 ms
SMOOTH MUSCLE
ELECTRICAL & MECHANICAL ACTIVITY
______ Smooth Muscle
- Nonsyncytial, meaning contractions do not spread widely.
Multiunit
SMOOTH MUSCLE
ELECTRICAL & MECHANICAL ACTIVITY
______ Smooth Muscle
- Produces more discrete, fine, and localized contractions compared to unitary smooth muscle.
Multiunit
SMOOTH MUSCLE
MOLECULAR BASIS OF CONTRACTION
Sequence of events in contraction and relaxation of smooth muscle:
Binding of acetylcholine to muscarinic receptors
Increased influx of Ca2+ into the cell
Activation of calmodulin-dependent myosin light chain kinase
Phosphorylation of myosin
Increased myosin ATPase activity and binding of myosin to actin
Contraction
Dephosphorylation of myosin by myosin light chain phosphatase
Relaxation, or sustained contraction due to the latch bridge and other mechanisms
SMOOTH MUSCLE
MOLECULAR BASIS OF CONTRACTION
______ smooth muscle contracts when stretched in the absence of any ______ innervation. Stretch is followed by a decline (______) in membrane potential, an increase in the frequency of ______, and a general increase in ______.
Unitary, extrinsic, depolarization, spikes, tone
SMOOTH MUSCLE
MOLECULAR BASIS OF CONTRACTION
______/______: Causes hyperpolarization (more negative membrane potential), decreased spike frequency, and muscle relaxation.
Epinephrine, Norepinephrine
SMOOTH MUSCLE
MOLECULAR BASIS OF CONTRACTION
______: Leads to depolarization, increased spike frequency, and heightened muscle activity, resulting in greater tonic tension and rhythmic contractions.
This effect is mediated by ______, which generates IP3, facilitating Ca2+ release.
Acetylcholine, phospholipase C
SMOOTH MUSCLE
MOLECULAR BASIS OF CONTRACTION
______ smooth muscle, like unitary smooth muscle, is highly responsive to chemical mediators such as ______ and ______. ______ often leads to sustained firing after a single stimulus, resulting in an ______ rather than a single action potential. When a single twitch occurs, it resembles skeletal muscle twitch but lasts about ______ times longer.
Multiunit, acetylcholine, norepinephrine, Norepinephrine, irregular tetanus, ten
SMOOTH MUSCLE
RELAXATION
Smooth muscle has mechanisms for both ______ and ______, which are vital for regulating blood flow in arteries.
contraction, relaxation
SMOOTH MUSCLE
RELAXATION
The arterial wall consists of three layers:
______: Contains endothelial cells.
Intima
SMOOTH MUSCLE
RELAXATION
The arterial wall consists of three layers:
______: Composed mainly of smooth muscle cells.
Media
SMOOTH MUSCLE
RELAXATION
The arterial wall consists of three layers:
______ (______): Made up of connective tissue.
Externa, Adventitia
SMOOTH MUSCLE
RELAXATION
Endothelial cells in the intima release an ______, which has been identified as ______.
endothelium-derived relaxing factor (EDRF), nitric oxide
SMOOTH MUSCLE
RELAXATION
Once produced, NO diffuses into the smooth muscle and activates soluble ______. This enzyme converts GTP into ______, a second messenger.
guanylyl cyclase, cyclic guanosine monophosphate (cGMP)
SMOOTH MUSCLE
RELAXATION
cGMP activates ______ that regulate ion channels, calcium homeostasis, and phosphatases, leading to the relaxation of smooth muscle.
protein kinases
SMOOTH MUSCLE
FUNCTION OF THE NERVE SUPPLY TO SMOOTH MUSCLE
The effects of Acetylcholine and norepinephrine on unitary smooth muscle has two important properties:
Spontaneous Activity
Sensitivity to Chemicals
SMOOTH MUSCLE
FUNCTION OF THE NERVE SUPPLY TO SMOOTH MUSCLE
The effects of Acetylcholine and norepinephrine on unitary smooth muscle has two important properties:
______: It can contract on its own without nervous stimulation.
Spontaneous Activity
SMOOTH MUSCLE
FUNCTION OF THE NERVE SUPPLY TO SMOOTH MUSCLE
The effects of Acetylcholine and norepinephrine on unitary smooth muscle has two important properties:
______: It responds to local chemical agents and those in circulation.
Sensitivity to Chemicals
SMOOTH MUSCLE
FUNCTION OF THE NERVE SUPPLY TO SMOOTH MUSCLE
Unitary smooth muscle typically receives ______ from both divisions of the autonomic nervous system. The role of this nerve supply is to ______, not initiate.
In some organs, the effects of ______ and ______ stimulation are reversed, highlighting the complexity of their interactions.
dual nerve supply, modify, noradrenergic, cholinergic
SMOOTH MUSCLE
FORCE GENERATION & PLASTICITY OF SMOOTH MUSCLE
______: Uses about ______% of myosin content and ______ times less ATP than skeletal muscle, they can generate ______ force per cross-sectional area.
Smooth Muscle Efficiency, 20, 100, similar
SMOOTH MUSCLE
FORCE GENERATION & PLASTICITY OF SMOOTH MUSCLE
______: Due to unique myosin isoforms and contractile-related proteins expressed in smooth muscle and their distinct regulation.
Slower Contractions
SMOOTH MUSCLE
FORCE GENERATION & PLASTICITY OF SMOOTH MUSCLE
______: When stretched, tension in smooth muscle initially ______ but gradually ______ if held at that length, sometimes dropping below the original level.
Tension Response, increases, decreases
SMOOTH MUSCLE
FORCE GENERATION & PLASTICITY OF SMOOTH MUSCLE
______ is a behavior that makes smooth muscle resemble a viscous mass, since it is impossible to correlate length and developed tension accurately, and no resting length can be assigned.
Plasticity
