Chapter 6 and 10 Test Flashcards
The most abundant type of cartilage in the human body is hyaline cartilage.
A) True
B) False
A) True
Explanation: Hyaline cartilage is the most common type of cartilage found in the body. It is found in the nose, trachea, larynx, ends of the ribs, and on the ends of long bones in joints. It provides support and flexibility.
The structural unit of compact bone (osteon) resembles the growth rings of a tree trunk.
A) True
B) False
A) True
Explanation: The osteon, or Haversian system, is the fundamental functional unit of compact bone. It consists of concentric layers, or lamellae, of calcified matrix, which resemble the growth rings of a tree trunk.
An osteon contains osteocytes, lamellae, and a central canal, and is found in compact bone only.
A) True
B) False
A) True
Explanation: An osteon is composed of osteocytes (bone cells) housed in lacunae, lamellae (layers of bone matrix), and a central (Haversian) canal that contains blood vessels and nerves. Osteons are found in compact bone, not in spongy bone.
The periosteum serves to protect bone, but also to nourish it as it is supplied with nerves and blood vessels.
A) True
B) False
A) True
Explanation: The periosteum is a dense layer of vascular connective tissue enveloping the bones except at the surfaces of the joints. It serves to protect the bone, provide a channel for the blood supply and nutrients for bone tissue, and serve as an attachment for muscles and tendons.
The humerus is an example of long bone.
A) True
B) False
A) True
Explanation: The humerus, which is the bone of the upper arm, is classified as a long bone. Long bones are characterized by a cylindrical shaft and are longer than they are wide.
Which of the following statements about cartilage is not true?
A) The most abundant type of cartilage in the human body is hyaline cartilage.
B) The three types of cartilage are: hyaline, elastic and cutaneous.
C) The embryonic skeleton is comprised mostly of hyaline cartilage.
D) Cartilage has a flexible matrix that can accommodate mitosis of chondrocytes – this makes it an excellent scaffolding tissue upon which to build bone.
B) The three types of cartilage are: hyaline, elastic and cutaneous.
Explanation: This statement is false because there is no cutaneous cartilage. The correct types of cartilage are hyaline, elastic, and fibrocartilage.
The functions of the skeletal system include all of the following, except:
A) support
B) production of blood cells (hematopoiesis)
C) storage of minerals
D) movement
E) hormone production
F) All are functions of bones
F) All are functions of bones
Explanation: This is true because bones support the body structure, produce blood cells (hematopoiesis), store minerals such as calcium and phosphorus, facilitate movement by serving as points of attachment for muscles, and produce hormones such as osteocalcin.
The mitotically-active bone cells that secrete bone matrix (osteoid) are:
A) Osteoclasts
B) Osteoblasts
C) Bone Lining cells
D) Chondroblasts
B) Osteoblasts
Explanation: Osteoblasts are bone-forming cells that secrete the bone matrix (osteoid). They are responsible for the synthesis and mineralization of bone during both initial bone formation and later bone remodeling.
Think: Bone —> Blasts
Identify the structure labeled “A”
A) diaphysis
B) compact bone
C) medullary cavity
D) periosteum
E) epiphysis
E) epiphysis
Identify the structure labeled “B”
A) diaphysis
B) compact bone
C) medullary cavity
D) periosteum
E) epiphysis
A) diaphysis
Identify the structure labeled “G”
A) diaphysis
B) compact bone
C) medullary cavity
D) periosteum
E) epiphysis
C) medullary cavity
Identify the structure labeled “H”
A) diaphysis
B) compact bone
C) medullary cavity
D) periosteum
E) epiphysis
D) periosteum
Identify the bone structure labelled “E”
A) circumferential lamellae
B) osteon
C) lamellae
D) perforating (Volkman’s) canal
E) central (Herversian) canal
A) circumferential lamellae
Identify the bone structure labelled “A”
A) circumferential lamellae
B) osteon
C) lamellae
D) perforating (Volkman’s) canal
E) central (Herversian) canal
B) osteon
Identify the bone structure labelled “C”
A) circumferential lamellae
B) osteon
C) lamellae
D) perforating (Volkman’s) canal
E) central (Herversian) canal
E) central (Herversian) canal
Identify the bone structure labelled “D”
A) circumferential lamellae
B) osteon
C) lamellae
D) perforating (Volkman’s) canal
E) central (Herversian) canal
D) perforating (Volkman’s) canal
The term osteoid refers to the organic part of the matrix of compact bones.
A) True
B) False
A) True
Explanation: Osteoid is the unmineralized, organic portion of the bone matrix that forms prior to the maturation of bone tissue. It includes collagen and other proteins.
Bones stop interstitial growth at the end of adolescence, but appositional growth can continue throughout our lifetimes.
A) True
B) False
A) True
Explanation: Interstitial growth (lengthwise growth) ceases after the epiphyseal plates close at the end of adolescence, but appositional growth (growth in thickness) can continue throughout life.
Spongy bone does not contain osteons, though the trabeculae are aligned along stress lines.
A) True
B) False
A) True
Explanation: Spongy bone, also known as cancellous bone, lacks the osteon structure found in compact bone. Instead, it has trabeculae aligned along lines of stress to provide strength and support.
Parathyroid hormone increases osteoblast activity to release more calcium ions into the bloodstream.
A) True
B) False
B) False
Explanation: Parathyroid hormone (PTH) increases osteoclast activity, which breaks down bone tissue and releases calcium ions into the bloodstream, not osteoblast activity.
Think: osteoclasts for calcium
The most important hormone in regulating bone growth during youth is thyroid hormone.
A) True
B) False
B) False
Explanation: While thyroid hormone plays a role in bone growth, the most important hormone during youth is the growth hormone, which stimulates overall bone growth and development.
A deficiency of thyroid hormone during bone formation would cause what kind of defect?
A) Uneven proportions in long bones
B) Inadequate calcification of bone
C) Decreased remodeling activity
D) Decreased interstitial growth of long bones at the epiphyseal plate
A) Uneven proportions in long bones
Explanation: Thyroid hormone is crucial for proper development and proportionate growth. A deficiency can lead to disproportionate growth of bones, leading to uneven proportions.
Which of the following statements about bone growth is incorrect?
A) Interstitial growth requires the presence of cartilage at the epiphyseal plate.
B) During interstitial growth, the epiphyseal plate maintains a constant thickness as new bone grows on the distal end (i.e. closer to the epiphyses) while new cartilage grows on the proximal end (i.e. closer to the diaphysis) of the bone.
C) Interstitial bone growth ends at the end of adolescence.
D) Appositional growth can occur any time throughout life.
E) All are true statements
E) All are true statements
All the provided statements about bone growth are accurate. Interstitial growth requires cartilage, ends at adolescence, and appositional growth can occur throughout life.
Which of the following statements about pre-natal ossification is not true?
A) Endochondral ossification is responsible for most bone formation during development.
B) Intramembranous ossification produces the flat bones of the skull and clavicles.
C) In endochondral ossification, bone forms by replacing hyaline cartilage “models”
D) In endochondral ossification existing cartilage must first be broken down and then replaced by bone.
E) All are true statements
E) All are true statements
Explanation: All the provided statements about pre-natal ossification are accurate. Endochondral ossification forms most bones, intramembranous ossification forms flat bones, and cartilage is replaced by bone in endochondral ossification.
Which of the following statements about bone remodeling is not true?
A) Bone resorption occurs first, followed by the laying down of new bone.
B) Bone remodeling occurs throughout our lifetimes.
C) Remodeling is accomplished by the coordinated efforts of osteoblasts and osteoclasts.
D) Mechanical and gravitational forces acting upon bones play a role in remodeling.
E) Remodeling is regulated hormonally/chemically by growth hormone and blood Ca++ levels.
E) Remodeling is regulated hormonally/chemically by growth hormone and blood Ca++ levels.
Explanation: While bone remodeling is influenced by mechanical and gravitational forces and involves osteoclasts and osteoblasts, it is mainly regulated by parathyroid hormone (PTH) and calcitonin, not growth hormone.
What hormone is the most important regulator of bone growth during adolescence?
A) Growth hormone
B) Thyroid hormone
C) Calcitonin
D) Parathyroid hormone
E) Testosterone and estrogen
A) Growth hormone
Explanation: Growth hormone is the primary regulator of bone growth during adolescence, stimulating the growth of bone and cartilage, and is crucial for proper development during this period.
The material responsible for the hardness and resistance to compression seen in long bone are hydroxyapatites (mineral salts).
A) True
B) False
A) True
Explanation: Hydroxyapatites (primarily calcium phosphate) are mineral salts that make up about 65% of bone by mass and are responsible for the hardness and resistance to compression.
The hormone that is primarily involved in the control of bone remodeling is growth hormone.
A) True
B) False
B) False
Explanation: While growth hormone is important for bone growth, the primary hormone involved in the control of bone remodeling is parathyroid hormone (PTH), which regulates calcium levels in the blood.
Sixty-five percent (65%) of the mass of bone is a compound called hydroxyapatites (mineral salts).
A) True
B) False
A) True
Explanation: Hydroxyapatites, which include calcium phosphate, make up 65% of the bone’s mass and contribute to its hardness.
Osteoid is secreted by osteoclasts.
A) True
B) False
B) False
Explanation: Osteoid is secreted by osteoblasts, not osteoclasts. Osteoclasts are involved in bone resorption.
Think: B before C
Hematopoiesis refers to the formation of blood cells within the red marrow cavities of certain bones.
A) True
B) False
A) True
Explanation: Hematopoiesis is the process of forming new blood cells, which occurs in the red marrow of bones.
Cartilage is nourished solely by the perichondrium as it has no blood vessels.
A) True
B) False
A) True
Explanation: Cartilage lacks blood vessels and is nourished by diffusion from the perichondrium, a layer of dense irregular connective tissue.
Which of the following would be an example of an irregular bone?
A) Femur
B) Vertebrae
C) Carpals (wrist bones)
D) Parietal (skull) bone
B) Vertebrae
Explanation: Vertebrae are classified as irregular bones due to their complex shapes, unlike femur (long bone), carpals (short bones), and parietal bone (flat bone).
Flat cells found on bone surfaces where bone remodeling is not going on are called:
A) Chondroblasts
B) Osteoblasts
C) Osteoclasts
D) Bone Lining cells
D) Bone Lining cells
Explanation: Bone lining cells are flat cells found on bone surfaces where bone remodeling is not occurring, helping to maintain bone matrix.
Which of the following is the single most important stimulus for epiphyseal plate activity during infancy and childhood?
A) Thyroid hormone
B) Parathyroid hormone
C) Calcium
D) Growth hormone
D) Growth hormone
Explanation: Growth hormone is the primary stimulus for epiphyseal plate activity, promoting bone lengthening during infancy and childhood.
Which of the following statements about bone growth is incorrect?
A) Interstitial growth requires the presence of cartilage at the epiphyseal plate.
B) During interstitial growth, the epiphyseal plate maintains a constant thickness as new bone grows on the distal end (i.e. closer to the epiphyses) while new cartilage grows on the proximal end (i.e. closer to the diaphyses) of the bone.
C) Appositional growth can occur any time throughout life.
D) Interstitial bone growth ends at the time of birth.
E) During appositional growth, the buildup of new bones must be balanced by the degradation of old bone.
D) Interstitial bone growth ends at the time of birth.
Explanation: Interstitial bone growth continues until the end of adolescence, not until birth. Growth plates (epiphyseal plates) remain active until the end of puberty.
What kind of tissue is the forerunner of long bones in the embryo?
A) Fibrocartilage
B) Elastic connective tissue
C) Hyaline cartilage
D) Fibrous connective tissue
C) Hyaline cartilage
Explanation: Hyaline cartilage is the forerunner of long bones in the embryo, serving as a model for future ossification.
An osteon contains osteocytes, lamellae, and a central canal, and is found in compact bone only.
A) True
B) False
A) True
Explanation: Osteons, or Haversian systems, are structural units of compact bone consisting of concentric lamellae around a central canal containing blood vessels and nerves.
Collagen is the most common fiber found in bone tissue.
A) True
B) False
A) True
Explanation: Collagen fibers are the most abundant fibers in bone tissue, providing tensile strength and flexibility.
The periosteum serves to protect bone, but also to nourish it as it is supplied with nerves and blood vessels.
A) True
B) False
A) True
Explanation: The periosteum is a dense layer of vascular connective tissue enveloping bones, which protects and nourishes them through its rich supply of blood vessels and nerves.
Closure of the epiphyseal plate stops all bone growth in the body.
A) True
B) False
B) False
Explanation: Closure of the epiphyseal plate stops longitudinal (interstitial) growth, but bones can still increase in thickness (appositional growth) throughout life.
The lamellae and osteocytes of spongy bone are not arranged into osteons.
A) True
B) False
A) True
Explanation: In spongy bone, the lamellae and osteocytes are arranged into trabeculae rather than osteons, which are the structural units of compact bone.
Parathyroid hormone increases osteoclast activity to release more calcium ions into the bloodstream.
A) True
B) False
A) True
Explanation: Parathyroid hormone (PTH) stimulates osteoclast activity, leading to increased bone resorption and the release of calcium ions into the bloodstream.
Which of the following statements about cartilage is not true?
A) Cartilage has a flexible matrix that can accommodate mitosis of chondrocytes – this makes it an excellent scaffolding tissue upon which to build bone.
B) The three types of cartilage are: hyaline, elastic and cutaneous.
C) The most abundant type of cartilage in the human body is hyaline cartilage.
D) The embryonic skeleton is comprised mostly of hyaline cartilage.
B) The three types of cartilage are: hyaline, elastic and cutaneous.
Explanation: The three types of cartilage are hyaline, elastic, and fibrocartilage. There is no cutaneous cartilage.
Which of the following statements about pre-natal ossification is not true?
A) Endochondral ossification is responsible for most bone formation during development.
B) Intramembranous ossification produces the flat bones of the skull and clavicles.
C) In endochondral ossification, bone forms by replacing hyaline cartilage “models.”
D) In endochondral ossification existing cartilage must first be broken down and then replaced by bone.
E) All are true statements.
E) All are true statements.
Explanation: All the provided statements accurately describe aspects of pre-natal ossification, including the processes and types of ossification.
Which of the following statements about bone remodeling is not true?
A) Bone resorption occurs first, followed by the laying down of new bone.
B) Bone remodeling occurs throughout our lifetimes.
C) Remodeling is accomplished by the coordinated efforts of osteoblasts and osteoclasts.
D) Mechanical and gravitational forces acting upon bones play a role in remodeling.
E) Remodeling is regulated hormonally/chemically by growth hormone and blood Ca++ levels.
E) Remodeling is regulated hormonally/chemically by growth hormone and blood Ca++ levels.
Explanation: Bone remodeling is primarily regulated by parathyroid hormone (PTH) and calcitonin, not by growth hormone.
Flat cells found on bone surfaces where bone remodeling is not going on are called:
A) Chondroblasts
B) Osteoblasts
C) Osteoclasts
D) Bone Lining cells
D) Bone Lining cells
Explanation: Bone lining cells are flat cells found on bone surfaces where remodeling is not occurring, helping to maintain bone matrix.
Which of the following is the single most important stimulus for epiphyseal plate activity during infancy and childhood?
A) Thyroid hormone
B) Parathyroid hormone
C) Calcium
D) Growth hormone
D) Growth hormone
Explanation: Growth hormone is the primary stimulus for epiphyseal plate activity, promoting bone lengthening during infancy and childhood.
Match the bone anatomy term with its best definition:
- Endosteum
- Lamellae
- Canaliculi
- Lacunae
A) Spaces found between concentric lamellae
B) Layers of bone matrix
C) The membrane lining the marrow cavity
D) Small channels that radiate through the matrix of bone
- Endosteum
C) The membrane lining the marrow cavity - Lamellae
B) Layers of bone matrix - Canaliculi
D) Small channels that radiate through the matrix of bone - Lacunae
A) Spaces found between concentric lamellae
Explanation:
-The endosteum lines the marrow cavity.
-Lamellae are the layers of bone matrix.
-Canaliculi are small channels that connect lacunae and allow for nutrient and waste exchange.
-Lacunae are the spaces that contain osteocytes.
What hormone is the most important regulator of bone growth during adolescence?
A) Parathyroid hormone
B) Growth hormone
C) Calcitonin
D) Testosterone and estrogen
E) Thyroid hormone
B) Growth hormone
Explanation: Growth hormone is the primary stimulus for bone growth during adolescence, promoting the lengthening of bones at the epiphyseal plates.
Which of the following statements about pre-natal ossification is not true?
A) Endochondral ossification is responsible for most bone formation during development.
B) Intramembranous ossification produces the flat bones of the skull and clavicles.
C) In endochondral ossification, bone forms by replacing hyaline cartilage “models.”
D) In both endochondral and intramembranous ossification, existing cartilage must first be broken down and then replaced by bone.
E) All are true statements.
E) All are true statements.
Explanation: Each statement accurately describes aspects of pre-natal ossification processes, including endochondral and intramembranous ossification.
The primary function of yellow bone marrow is:
A) Hematopoiesis
B) Fat storage
C) Mineral storage
D) Producing osteoblasts
B) Fat storage
Explanation: Yellow bone marrow is primarily involved in the storage of fats, which can serve as an energy reserve.
Which type of bone cell is responsible for bone resorption?
A) Osteoblast
B) Osteoclast
C) Osteocyte
D) Chondrocyte
B) Osteoclast
Explanation: Osteoclasts break down bone tissue, a process known as bone resorption, which is important for bone remodeling and calcium homeostasis.
The epiphyseal plate is responsible for:
A) Bone thickening
B) Lengthwise bone growth
C) Bone remodeling
D) Bone repair
B) Lengthwise bone growth
Explanation: The epiphyseal plate, or growth plate, is where new bone tissue is generated, leading to the lengthwise growth of bones during development.
Which type of cartilage is found at the ends of long bones in joints?
A) Hyaline cartilage
B) Elastic cartilage
C) Fibrocartilage
D) Articular cartilage
D) Articular cartilage
Explanation: Articular cartilage, a type of hyaline cartilage, covers the ends of long bones in synovial joints, reducing friction and absorbing shock.
Compact bone is characterized by:
A) Trabeculae
B) Osteons
C) Periosteum
D) Endosteum
B) Osteons
Explanation: Compact bone is dense and organized into structural units called osteons or Haversian systems.
Which hormone decreases blood calcium levels by inhibiting osteoclast activity?
A) Parathyroid hormone
B) Growth hormone
C) Calcitonin
D) Estrogen
C) Calcitonin
Explanation: Calcitonin, secreted by the thyroid gland, decreases blood calcium levels by inhibiting osteoclast activity and promoting calcium deposition in bones.
The long bone structure that stores fat and is lined with endosteum is the:
A) Medullary cavity
B) Epiphysis
C) Diaphysis
D) Periosteum
A) Medullary cavity
Explanation: The medullary cavity is the central cavity of bone shafts where yellow bone marrow (fat) is stored, and it is lined with the endosteum.
What is the name of the process by which bone forms directly from mesenchymal tissue?
A) Endochondral ossification
B) Intramembranous ossification
C) Bone remodeling
D) Calcification
B) Intramembranous ossification
Explanation: Intramembranous ossification is the process by which certain flat bones, like those of the skull and clavicles, form directly from mesenchymal tissue.
Bone tissue remodeling is controlled by:
A) Osteoblasts and osteoclasts
B) Osteocytes and chondrocytes
C) Chondroblasts and fibroblasts
D) Osteoclasts and chondroblasts
A) Osteoblasts and osteoclasts
Explanation: Bone remodeling involves the coordinated activity of osteoblasts, which build bone, and osteoclasts, which resorb bone.
Which type of bone cell is derived from a hematopoietic stem cell?
A) Osteoblast
B) Osteoclast
C) Osteocyte
D) Chondrocyte
B) Osteoclast
Explanation: Osteoclasts originate from hematopoietic stem cells, the same lineage that produces macrophages, highlighting their role in resorption.
Muscle tissue is one of the four major tissue types.
A) True
B) False
A) True
Explanation: There are four primary tissue types in the human body: epithelial, connective, muscle, and nervous tissues. Muscle tissue is responsible for producing movement, maintaining posture, and generating heat among other functions.
The plasma membrane of a muscle cell is called the sarcoplasmic reticulum.
A) True
B) False
B) False
Explanation: The plasma membrane of a muscle cell is called the sarcolemma, not the sarcoplasmic reticulum. The sarcoplasmic reticulum is an organelle within the muscle cell that stores and releases calcium ions, which are critical for muscle contraction.
Another name for a muscle cell is a muscle fiber.
A) True
B) False
A) True
Explanation: Muscle cells are often referred to as muscle fibers due to their long, cylindrical shape. This term is commonly used in the context of skeletal muscle tissue.
Skeletal muscle requires nervous system stimulation to contract.
A) True
B) False
A) True
Explanation: Skeletal muscles are under voluntary control, meaning they require signals from the nervous system to contract. These signals are typically transmitted via motor neurons.
The epimysium is the connective tissue covering the exterior of a muscle.
A) True
B) False
A) True
Explanation: The epimysium is a layer of connective tissue that surrounds the entire muscle, providing structural support and protection. It is the outermost layer of the muscle’s connective tissue sheath.
Functions of muscle include:
A) movement of bones or fluid
B) maintaining posture and body position
C) stabilizing and strengthening joints
D) heat generation
E) forms valves
F) All of the above
F) All of the above
Explanation: Muscles perform several essential functions, including:
-Movement of bones or fluids (e.g., blood)
-Maintaining posture and body position
-Stabilizing and strengthening joints
-Generating heat during contraction
-Forming valves (e.g., sphincters in the digestive system)
Which of the following statements about the microscopic structure of muscle fibers is not correct:
A) The sarcoplasmic reticulum surrounds each myofibril in a muscle fiber.
B) At each A band-I band junction, the sarcolemma dives deep into the cells interior forming an elongated tube called the T tubule.
C) The T tubule is integrated with two terminal cisterns of the sarcoplasmic reticulum to form triads.
D) At the triad, T tubule proteins act as voltage sensors and change shape in response to voltage changes.
E) All are true statements
E) All are true statements
Explanation: All the statements given about the microscopic structure of muscle fibers are correct:
-The sarcoplasmic reticulum surrounds each myofibril in a muscle fiber, playing a crucial role in calcium storage and release.
-At each A band-I band junction, the sarcolemma (muscle cell membrane) dives deep into the cell’s interior, forming T tubules.
-The T tubule system is integrated with two terminal cisterns of the sarcoplasmic reticulum to form triads, which are critical for the excitation-contraction coupling process.
-At the triad, T tubule proteins act as voltage sensors and change shape in response to electrical signals, which then trigger the release of calcium from the sarcoplasmic reticulum.
During repolarization, Na+ channels close and voltage-gated K+ channels open – the K+ efflux rapidly restores negatively charged conditions inside cell.
A) True
B) False
A) True
Explanation: During the repolarization phase of an action potential, the sodium (Na+) channels close, and the voltage-gated potassium (K+) channels open. This allows K+ to exit the cell, which helps to restore the negative charge inside the cell, returning it to its resting membrane potential.
In a relaxed state, the thick and thin filaments overlap only in the I band.
A) True
B) False
B) False
Explanation: In a relaxed muscle, thick (myosin) and thin (actin) filaments overlap in the A band, not the I band. The I band contains only thin filaments and is the region that shortens during muscle contraction.
Once an AP is initiated, it is unstoppable and leads to a muscle fiber contraction.
A) True
B) False
A) True
Explanation: Once an action potential (AP) is initiated in a muscle fiber, it propagates along the sarcolemma and into the T tubules, triggering the release of calcium ions from the sarcoplasmic reticulum, which leads to muscle contraction. This process is often referred to as the “all-or-none” principle.
Each muscle fiber is individually innervated by its own axon terminal.
A) True
B) False
A) True
Explanation: Each muscle fiber is innervated by a motor neuron at a neuromuscular junction. The axon terminal of the motor neuron releases neurotransmitters that bind to receptors on the muscle fiber’s membrane, initiating muscle contraction.
During repolarization Na+ channels close and K+ channels open.
A) True
B) False
A) True
Explanation: This is a reiteration of the first question. During repolarization, the Na+ channels close, and the voltage-gated K+ channels open, allowing K+ to flow out of the cell, restoring the negative charge inside the cell.
Which of the following statements about the generation and propagation of action potentials initiated at the neuromuscular junction is not true:
A) The binding of neurotransmitters to receptors at the neuromuscular junction (NMJ) opens chemically (ligand) gated ion channels.
B) The opening of ligand gated channels at the NMJ allows the simultaneous diffusion of Na+ inward and K+ outward causing interior of cell to becomes less negative (a local depolarization).
C) Local depolarization spreads to adjacent membrane areas and causes additional voltage-gated Na+ channels to open.
D) Increasing Na+ influx further decreases membrane voltage toward critical voltage called threshold.
E) All are true statements.
E) All are true statements.
Explanation: All the statements given are true:
-The binding of neurotransmitters to receptors at the NMJ opens chemically (ligand) gated ion channels.
-The opening of these channels allows Na+ to diffuse inward and K+ to diffuse outward, causing a local depolarization.
-This local depolarization spreads to adjacent areas, causing additional voltage-gated Na+ channels to open.
-The increasing Na+ influx further depolarizes the membrane, reaching the threshold and generating an action potential.
Which is the correct sequence of events for the generation of an action potential?
A)
1. Neurotransmitters are received at the neuromuscular junction
2. Neurotransmitter binding opens Na+/K+ channels
3. Na+ influx causes local depolarization of the cell membrane causing an end-plate potential
4. The end-plate potential spreads to adjacent membrane areas causing additional voltage gated Na+ channels to open
5. Action potential is generated
B)
1. Neurotransmitters are received at the neuromuscular junction
2. Neurotransmitter binding opens Na+/K+ channels
3. Na+ influx causes local depolarization of the cell membrane causing an end-plate potential
4. Action potential is generated
5. The end-plate potential spreads to adjacent membrane areas causing additional voltage gated Na+ channels to open
C)
1. Neurotransmitters are received at the neuromuscular junction
2. Action potential is generated
3. Neurotransmitter binding opens Na+/K+ channels
4. The end-plate potential spreads to adjacent membrane areas causing additional voltage gated Na+ channels to open
5. Na+ influx causes local depolarization of the cell membrane causing an end-plate potential
A)
1. Neurotransmitters are received at the neuromuscular junction
2. Neurotransmitter binding opens Na+/K+ channels
3. Na+ influx causes local depolarization of the cell membrane causing an end-plate potential
4. The end-plate potential spreads to adjacent membrane areas causing additional voltage gated Na+ channels to open
5. Action potential is generated
Explanation: This sequence accurately describes the steps leading to the generation of an action potential at the neuromuscular junction.
What is the correct sequence of events that occur at the neuromuscular junction?
A)
1. An action potential arrives at the axon terminal of a motor neuron.
2. Ach binding opens ions channels allowing Na+ in and K+ out of the muscle fiber.
3. Ach diffuses across the synaptic cleft and binds to receptors on the sarcolemma.
4. Voltage-gated Ca++ channels in the axon terminal open and Ca++ moves in
5. Ca++ entry causes the neurotransmitter acetylcholine (Ach) to be released by exocytosis.
B)
1. An action potential arrives at the axon terminal of a motor neuron.
2. Voltage-gated Ca++ channels in the axon terminal open and Ca++ moves in
3. Ca++ entry causes the neurotransmitter acetylcholine (Ach) to be released by exocytosis.
4. Ach diffuses across the synaptic cleft and binds to receptors on the sarcolemma.
5. Ach binding opens ions channels allowing Na+ in and K+ out of the muscle fiber.
C)
1. An action potential arrives at the axon terminal of a motor neuron.
2. Ca++ entry causes the neurotransmitter acetylcholine (Ach) to be released by exocytosis.
3. Ach diffuses across the synaptic cleft and binds to receptors on the sarcolemma.
4. Voltage-gated Ca++ channels in the axon terminal open and Ca++ moves in.
5. Ach binding opens ions channels allowing Na+ in and K+ out of the muscle fiber.
B)
1. An action potential arrives at the axon terminal of a motor neuron.
2. Voltage-gated Ca++ channels in the axon terminal open and Ca++ moves in
3. Ca++ entry causes the neurotransmitter acetylcholine (Ach) to be released by exocytosis.
4. Ach diffuses across the synaptic cleft and binds to receptors on the sarcolemma.
5. Ach binding opens ions channels allowing Na+ in and K+ out of the muscle fiber.
Which of the following statements about resting membrane potential is not correct:
A) The resting sarcolemma is polarized; that is the inside of the plasma membrane is negative relative to the outside.
B) There is more K+ inside the cell than outside the cell.
C) There is more Na+ outside the cell than inside the cell.
D) The presence of negatively charged proteins inside the cell contribute to the negative charge inside the cell.
E) All are true statements.
E) All are true statements.
Explanation: All the given statements about the resting membrane potential are correct:
-The resting sarcolemma is polarized, meaning the inside of the plasma membrane is negative relative to the outside.
-There is more K+ inside the cell than outside the cell.
-There is more Na+ outside the cell than inside the cell.
-The presence of negatively charged proteins inside the cell contributes to the negative charge inside the cell.
Excitation-contraction coupling is the connection between the electrical events of an action potential and mechanical events of a muscle contraction.
A) True
B) False
A) True
Explanation: Excitation-contraction coupling refers to the physiological process of converting an electrical stimulus (action potential) to a mechanical response (muscle contraction). This process involves the transmission of the action potential along the sarcolemma and down T-tubules, which triggers the release of calcium ions from the sarcoplasmic reticulum, leading to muscle contraction.
During cross bridge cycling, cross bridge attachments form and break several times during a contraction.
A) True
B) False
A) True
Explanation: During muscle contraction, the myosin heads bind to actin forming cross bridges, pull the actin filaments toward the center of the sarcomere, and then detach to bind again in a cyclical manner. This repeated formation and breaking of cross bridges is essential for muscle contraction.
Contraction is ultimately stimulated by the binding of calcium to troponin which then changes shape and removes the blocking action of tropomyosin.
A) True
B) False
A) True
Explanation: Calcium ions released from the sarcoplasmic reticulum bind to troponin, causing a conformational change that moves tropomyosin away from the myosin-binding sites on actin filaments, thus enabling cross bridge formation and muscle contraction.
The electrical signals of the action potential do not directly act upon myofilaments, instead a rise in intracellular Na+ concentrations trigger the actual muscle contraction.
A) True
B) False
B) False
Explanation: The electrical signal of the action potential causes a rise in intracellular Ca++ (not Na+), which is essential for muscle contraction. The rise in Ca++ levels leads to binding of calcium to troponin, which then initiates contraction.
ATP supplies the only energy for muscle contractions.
A) True
B) False
A) True
Explanation: ATP is the primary source of energy for muscle contractions. It is required for cross bridge formation, detachment, and the pumping of Ca++ back into the sarcoplasmic reticulum.
Which of the following is the correct sequence of events for excitation-contraction coupling:
A)
1. An action potential is generated at the NMJ and propagated down the sarcolemma
2. The action potential travels down the T tubules
3. Myosin binding to actin forms cross bridges and contraction (cross bridge cycling) begins
4. Ca++ binds to troponin and removes the blocking action of tropomyosin on actin
5. Change in voltage gated channels at the triad causes Ca++ release from the SR
B)
1. An action potential is generated at the NMJ and propagated down the sarcolemma
2. Myosin binding to actin forms cross bridges and contraction (cross bridge cycling) begins
3. Ca++ binds to troponin and removes the blocking action of tropomyosin on actin
4. The action potential travels down the T tubules
5. Change in voltage gated channels at the triad causes Ca++ release from the SR
C)
1. An action potential is generated at the NMJ and propagated down the sarcolemma
2. The action potential travels down the T tubules
3. Change in voltage gated channels at the triad causes Ca++ release from the SR
4. Ca++ binds to troponin and removes the blocking action of tropomyosin on actin
5. Myosin binding to actin forms cross bridges and contraction (cross bridge cycling) begins
C)
1. An action potential is generated at the NMJ and propagated down the sarcolemma
2. The action potential travels down the T tubules
3. Change in voltage gated channels at the triad causes Ca++ release from the SR
4. Ca++ binds to troponin and removes the blocking action of tropomyosin on actin
5. Myosin binding to actin forms cross bridges and contraction (cross bridge cycling) begins
Explanation: This sequence correctly outlines the steps from the initiation of an action potential to the start of muscle contraction.
Which of the following statements about excitation/contraction coupling is not true?
A) Excitation-contraction links the electrical events of an action potential to the mechanical events of a muscle contraction.
B) The electrical signal of the action potential does not directly act upon the actin and myosin proteins, instead it causes a rise in intracellular Ca++.
C) During excitation-contraction coupling, an action potential is transmitted across the sarcolemma and down the T tubules.
D) Changes in the shape of voltage-sensitive proteins in the T tubules stimulate Ca++ release from SR.
E) All are true statements
E) All are true statements
Explanation: All the statements (A, B, C, D) correctly describe aspects of excitation-contraction coupling, from linking electrical and mechanical events to the role of intracellular Ca++.
Which of the following statements about the cessation of an action potential is not correct:
A) When the action potential ceases, the voltage-sensitive tubule proteins return to their original shape, stopping the release of Ca+ into the sarcoplasm.
B) Ca+ levels in the sarcoplasm fall as Ca+ is pumped back into the extracellular space.
C) In the absence of Ca++, the blocking action of tropomyosin is restored.
D) When actin and myosin can’t bind, relaxation of the myofibrils occurs.
B) Ca+ levels in the sarcoplasm fall as Ca+ is pumped back into the extracellular space.
Explanation: Calcium is not pumped back into the extracellular space but rather back into the sarcoplasmic reticulum. The other statements correctly describe the cessation process.
What opens in response to the action potential traveling down the T tubule?
A) ligand gated Na+/K+ channels
B) voltage-gated Na+ channels
C) voltage-sensitive Ca++ gates
C) voltage-sensitive Ca++ gates
Explanation: The action potential traveling down the T-tubules causes voltage-sensitive Ca++ channels in the sarcoplasmic reticulum to open, releasing Ca++ into the sarcoplasm.
By which method is ATP regenerated during exercise?
A) Direct phosphorylation of ADP by creatinine phosphate
B) anaerobic respiration
C) aerobic respiration
D) All of the above
D) All of the above
Explanation: ATP is regenerated through various pathways during exercise: direct phosphorylation of ADP by creatine phosphate, anaerobic respiration (glycolysis), and aerobic respiration (oxidative phosphorylation).
Smooth muscle fibers do not exhibit myofibrils or sarcomeres, but do have T tubules.
A) True
B) False
B) False
Explanation: Smooth muscle fibers do not have myofibrils or sarcomeres, which are characteristic of skeletal and cardiac muscle. Instead, they have a more irregular arrangement of actin and myosin. Additionally, smooth muscle fibers lack T tubules. They rely on caveolae, small invaginations of the plasma membrane, to facilitate the influx of Ca2+.
Smooth muscle tissue usually has two layers – longitudinal and circular.
A) True
B) False
A) True
Explanation: Smooth muscle tissue typically has two layers: an outer longitudinal layer and an inner circular layer. These layers enable the contraction and relaxation necessary for the movement of substances through organs like the intestines and blood vessels.
Skeletal muscle does not require nervous system stimulation to contract, whereas smooth muscle does.
A) True
B) False
B) False
Explanation: Skeletal muscle requires nervous system stimulation to contract, via motor neurons and neuromuscular junctions. Smooth muscle, however, can contract in response to various stimuli, including autonomic nervous system input, hormones, and local factors, and can also generate spontaneous contractions (myogenic activity).
One of the unique features of smooth muscle is its ability to divide and increase its number of cells.
A) True
B) False
A) True
Explanation: Smooth muscle cells have the capacity to undergo hyperplasia, which is an increase in the number of cells. This is different from most skeletal muscle cells, which primarily grow through hypertrophy (increase in cell size).
During smooth muscle excitation-contraction coupling, the protein calmodulin binds Ca++ instead of troponin.
A) True
B) False
A) True
Explanation: In smooth muscle, the protein calmodulin binds to Ca2+ ions. This complex then activates myosin light-chain kinase (MLCK), which is necessary for muscle contraction. This mechanism is different from skeletal muscle, where Ca2+ binds to troponin.
Which of the following statements about smooth muscle innervation is not true:
A) Smooth muscle contains neuromuscular junctions.
B) Smooth muscle does not require nervous system stumulation to contract.
C) Autonomic (involuntary) nerve fibers innervate smooth muscle at diffuse junctions.
D) Bulbs of nerves called varicosities store and release neurotransmitters into synaptic clefts in the general area of the cells.
A) Smooth muscle contains neuromuscular junctions.
Explanation: Smooth muscle does not have traditional neuromuscular junctions like skeletal muscle. Instead, it is innervated by autonomic nerve fibers that release neurotransmitters from varicosities along the length of the nerve fibers, creating diffuse junctions.
Which of the following statements about smooth muscle contractions is not true:
A) The final trigger for contraction is an increase in intracellular Ca2+.
B) Actin and myosin filaments interact by sliding filament mechanism.
C) Smooth muscle cells are electrically isolated from one another.
D) Smooth muscles exhibit slow, synchronized contractions.
C) Smooth muscle cells are electrically isolated from one another.
Explanation: Smooth muscle cells are often connected by gap junctions, which allow electrical signals to pass between cells, facilitating coordinated contractions. This is different from skeletal muscle fibers, which are electrically isolated and each require direct innervation.
Which of the following is unique to smooth muscle contraction? (i.e. does not also occur in skeletal muscle)
A) The trigger for contraction is a rise in intracellular calcium.
B) The protein calmodulin binds calcium.
C) ATP energizes the sliding process.
D) Actin and myosin interact by the sliding filament mechanism.
B) The protein calmodulin binds calcium.
Explanation: In smooth muscle, Ca2+ binds to calmodulin, whereas in skeletal muscle, Ca2+ binds to troponin. This binding difference is a key distinction in the contraction mechanisms of these muscle types.
Which of the following is a characteristic unique to smooth muscle cells?
A) The ability to not only increase in size, but to divide and increase in numbers as well.
B) The ability to stretch then adapt to new length, while retaining its ability to recoil.
C) The ability to contract when between half and twice its resting length which allows hollow organs to tolerate tremendous change in volume.
D) All of the above.
D) All of the above.
Explanation: Smooth muscle cells have several unique characteristics:
-They can divide and increase in number (hyperplasia).
-They can stretch and adapt to new lengths while retaining the ability to recoil.
-They can contract over a wide range of lengths, which is crucial for the function of hollow organs that undergo significant volume changes.
Which is the correct sequence of events in the excitation-contraction coupling of smooth muscle?
A)
1. Calcium ions (Ca2+) enter the cytosol from the ECF via Ca2+ channels, or from the scant SR.
2. The activated kinase enzymes catalyze transfer of phosphate to myosin, activating the myosin ATPases
3. Activated calmodulin activates the myosin light chain kinase enzymes
4. Ca2+ binds to and activates calmodulin
5. Activated myosin forms cross bridges with actin of the thin filaments. Muscle contraction begins.
B)
1. Calcium ions (Ca2+) enter the cytosol from the ECF via Ca2+ channels, or from the scant SR.
2. Ca2+ binds to and activates calmodulin.
3. Activated calmodulin activates the myosin light chain kinase enzymes.
4. Activated myosin forms cross bridges with actin of the thin filaments. Muscle contraction begins.
5. The activated kinase enzymes catalyze transfer of phosphate to myosin, activating the myosin ATPases.
C)
1. Calcium ions (Ca2+) enter the cytosol from the ECF via Ca2+ channels, or from the scant SR.
2. Ca2+ binds to and activates calmodulin
3. Activated calmodulin activates the myosin light chain kinase enzymes
4. The activated kinase enzymes catalyze transfer of phosphate to myosin, activating the myosin ATPases
5. Activated myosin forms cross bridges with actin of the thin filaments. Muscle contraction begins.
C)
1. Calcium ions (Ca2+) enter the cytosol from the ECF via Ca2+ channels, or from the scant SR.
2. Ca2+ binds to and activates calmodulin
3. Activated calmodulin activates the myosin light chain kinase enzymes
4. The activated kinase enzymes catalyze transfer of phosphate to myosin, activating the myosin ATPases
5. Activated myosin forms cross bridges with actin of the thin filaments. Muscle contraction begins.
Explanation:
-Calcium ions (Ca2+) enter the cytosol from the extracellular fluid (ECF) via Ca2+ channels or from the scant sarcoplasmic reticulum (SR).
-Ca2+ binds to and activates calmodulin.
-Activated calmodulin activates the myosin light-chain kinase (MLCK) enzymes.
-The activated kinase enzymes catalyze the transfer of phosphate to myosin, activating the myosin ATPases.
-Activated myosin forms cross-bridges with actin of the thin filaments, and muscle contraction begins.
Which of the following is NOT part of the neuromuscular junction?
A) Sarcoplasmic reticulum
B) Junctional fold of the sarcolemma
C) Axon terminal
D) Synaptic cleft
E) Synaptic vesicles containing neurotransmitters
A) Sarcoplasmic reticulum
Explanation: The neuromuscular junction is the synapse or junction between a motor neuron and a skeletal muscle fiber. It includes the axon terminal, synaptic cleft, and the junctional folds of the sarcolemma where neurotransmitter receptors are located. The sarcoplasmic reticulum is involved in muscle contraction but is not part of the neuromuscular junction itself.
During prolonged duration exercise, muscles use:
A) Anaerobic respiration
B) ATP stored in muscle cells
C) Creatine phosphorylation
D) Aerobic respiration
D) Aerobic respiration
Explanation: During prolonged exercise, muscles primarily use aerobic respiration, which is efficient in producing ATP for long-duration activities. ATP stored in muscle cells and creatine phosphorylation provide energy for short, quick bursts of activity, while anaerobic respiration is used when oxygen is scarce.
Which of the following statements about the cessation of an action potential is not correct:
A) When the action potential ceases, the voltage-sensitive tubule proteins return to their original shape, stopping the release of Ca++ into the sarcoplasm.
B) Ca++ levels in the sarcoplasm fall as Ca++ is pumped back into the sarcoplasmic reticulum.
C) In the absence of Ca++, the blocking action of tropomyosin is restored.
D) When actin and myosin can’t bind, relaxation of the myofibrils occurs.
E) All are correct statements
E) All are correct statements
Explanation: All the provided statements accurately describe what happens when an action potential ceases. The voltage-sensitive tubule proteins return to their original shape, Ca++ is pumped back into the sarcoplasmic reticulum, the blocking action of tropomyosin is restored, and myofibrils relax when actin and myosin can’t bind. Therefore, the answer is “All are correct statements.”
Skeletal muscle does not require nervous system stimulation to contract.
A) True
B) False
B) False
Explanation: Skeletal muscles do require nervous system stimulation to contract. This is in contrast to cardiac muscle, which can contract without nervous stimulation due to its intrinsic pacemaker activity.
Smooth muscle tissue usually has two layers – longitudinal and circular.
A) True
B) False
A) True
Explanation: Smooth muscle tissue typically has two layers: an inner circular layer and an outer longitudinal layer. These layers help propel contents through organs and vessels by contracting in a coordinated manner.
A T tubule and two terminal cisterns of the sarcolemma form a triad.
A) True
B) False
B) False
Explanation: A triad in muscle cells consists of a T tubule and two terminal cisternae of the sarcoplasmic reticulum, not the sarcolemma.
Smooth muscle does not exhibit sarcomeres, myofibrils, or T tubules.
A) True
B) False
A) True
Explanation: Smooth muscle lacks the striated structure seen in skeletal and cardiac muscle, meaning it does not have sarcomeres, myofibrils, or T tubules. Instead, it has a more irregular arrangement of actin and myosin filaments.
Which of the following is NOT part of the neuromuscular junction?
A) Sarcoplasmic reticulum
B) Junctional fold of the sarcolemma
C) Axon terminal
D) Synaptic cleft
E) Synaptic vesicles containing neurotransmitters
A) Sarcoplasmic reticulum
Explanation: The neuromuscular junction includes the axon terminal, synaptic cleft, and junctional folds of the sarcolemma. The sarcoplasmic reticulum, while crucial for muscle contraction, is not part of the neuromuscular junction.
During prolonged duration exercise, muscles use:
A) Anaerobic respiration
B) ATP stored in muscle cells
C) Creatine phosphorylation
D) Aerobic respiration
D) Aerobic respiration
Explanation: During prolonged exercise, muscles primarily use aerobic respiration to generate ATP efficiently over long periods.
Which of the following statements about the cessation of an action potential is not correct:
A) When the action potential ceases, the voltage-sensitive tubule proteins return to their original shape, stopping the release of Ca++ into the sarcoplasm.
B) Ca++ levels in the sarcoplasm fall as Ca++ is pumped back into the sarcoplasmic reticulum.
C) In the absence of Ca++, the blocking action of tropomyosin is restored.
D) When actin and myosin can’t bind, relaxation of the myofibrils occurs.
E) All are correct statements
E) All are correct statements
Explanation: All statements accurately describe the processes that occur when an action potential ceases.
Skeletal muscle does not require nervous system stimulation to contract.
A) True
B) False
B) False
Explanation: Skeletal muscles require nervous system stimulation to contract, unlike cardiac muscle which has its intrinsic pacemaker.
Smooth muscle tissue usually has two layers – longitudinal and circular.
A) True
B) False
A) True
Explanation: Smooth muscle tissue typically has an inner circular layer and an outer longitudinal layer.
A T tubule and two terminal cisterns of the sarcolemma form a triad.
A) True
B) False
B) False
Explanation: A triad in muscle cells consists of a T tubule and two terminal cisternae of the sarcoplasmic reticulum.
Smooth muscle does not exhibit sarcomeres, myofibrils, or T tubules.
A) True
B) False
A) True
Explanation: Smooth muscle lacks the striated structure seen in skeletal and cardiac muscle, meaning it does not have sarcomeres, myofibrils, or T tubules.
Each muscle fiber is individually innervated by its own axon terminal.
A) True
B) False
A) True
Explanation: Each skeletal muscle fiber is innervated by its own axon terminal from a motor neuron.
A T tubule is an extension of the sarcoplasmic reticulum that reaches deep into the muscle fiber.
A) True
B) False
B) False
Explanation: A T tubule is an invagination of the sarcolemma (muscle cell membrane) that helps conduct action potentials into the muscle fiber. It is not an extension of the sarcoplasmic reticulum.
Creatine phosphate functions in the muscle cell by:
A) Storing energy that will be transferred to ADP to resynthesize ATP
B) Inducing a conformational change in the myofilaments
C) Forming a chemical compound with actin
D) Forming a temporary chemical compound with myosin
A) Storing energy that will be transferred to ADP to resynthesize ATP
Explanation:
Creatine phosphate serves as a rapid reserve of high-energy phosphates in muscle cells to quickly regenerate ATP from ADP during the initial stages of exercise.
What structure in skeletal muscle cells functions in calcium storage?
A) Sarcoplasmic reticulum
B) Myofibrillar network
C) Intermediate filament network
D) Mitochondria
A) Sarcoplasmic reticulum
Explanation: The sarcoplasmic reticulum stores calcium ions, which are released during muscle contraction.
The major function of the sarcoplasmic reticulum in muscle contraction is to:
A) Provide a source of ATP for the contraction process
B) Make and store glycogen
C) Store and release calcium ions
D) Synthesize proteins needed for muscle contractions
C) Store and release calcium ions
Explanation: The sarcoplasmic reticulum stores and releases calcium ions, which are essential for muscle contraction.
What is the correct sequence of events that occur at the neuromuscular junction?
(This is the correct answer)
1. An action potential arrives at the axon terminal of a motor neuron.
2. Voltage-gated Ca++ channels in the axon terminal open and Ca++ moves in.
3. Ca++ entry causes the neurotransmitter acetylcholine (Ach) to be released by exocytosis.
4. Ach diffuses across the synaptic cleft and binds to receptors on the sarcolemma.
5. Ach binding opens ion channels allowing Na+ in and K+ out of the muscle fiber.
- An action potential arrives at the axon terminal of a motor neuron.
- Voltage-gated Ca++ channels in the axon terminal open and Ca++ moves in.
- Ca++ entry causes the neurotransmitter acetylcholine (Ach) to be released by exocytosis.
- Ach diffuses across the synaptic cleft and binds to receptors on the sarcolemma.
- Ach binding opens ion channels allowing Na+ in and K+ out of the muscle fiber.
Explanation: This sequence accurately describes the steps that occur at the neuromuscular junction from the arrival of an action potential to the initiation of a muscle contraction.
Which is the correct order of fuel use during intense, short duration exercise:
A) ATP Immediately available in muscle cells
B) Phosphorylation of creatine phosphate
C) Anaerobic respiration
A) ATP Immediately available in muscle cells
Explanation: During intense, short-duration exercise, muscles use ATP stored in muscle cells first, followed by creatine phosphate phosphorylation, and finally anaerobic respiration.
After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction?
A) The action potential stops going down the overloaded T tubules
B) Calcium ions returning to the terminal cisternae
C) The tropomyosin blocking the myosin once full contraction is achieved
D) Acetylcholinesterase destroying the ACh
D) Acetylcholinesterase destroying the ACh
Explanation: Acetylcholinesterase is an enzyme that breaks down acetylcholine in the synaptic cleft, stopping the signal for muscle contraction.
Excitation-contraction coupling is the connection between the electrical events of an action potential and mechanical events of a muscle contraction.
A) True
B) False
A) True
Explanation: Excitation-contraction coupling describes how an electrical signal (action potential) leads to muscle contraction.
During smooth muscle excitation-contraction coupling, the protein calmodulin binds Ca++ instead of troponin.
A) True
B) False
A) True
Explanation: In smooth muscle, calmodulin binds to Ca++, initiating the contraction process, unlike skeletal muscle where troponin binds to Ca++.
The perimysium is the connective tissue covering the exterior of a muscle.
A) True
B) False
B) False
Explanation: The perimysium surrounds bundles of muscle fibers (fascicles), not the exterior of the muscle. The epimysium covers the exterior of the muscle.
After an action potential, repolarization restores only the electrical conditions of the cell, the ionic conditions inside a cell must be restored by Na+/K+ pumps.
A) True
B) False
B) False
Explanation: Repolarization restores the electrical state of the cell membrane, but the Na+/K+ pumps are needed to restore the ionic conditions to their resting state.
During repolarization, Na+ channels close and voltage-gated K+ channels open - the K+ efflux rapidly restores positively charged conditions inside the cell.
A) True
B) False
A) True
Explanation: During repolarization, Na+ channels close, and K+ channels open, allowing K+ to leave the cell, restoring the membrane potential to a negative state inside.
The electrical signals of the action potential do not directly act upon myofilaments, instead a rise in intracellular Ca++ concentrations trigger the actual muscle contraction.
A) True
B) False
A) True
Explanation: The action potential leads to the release of Ca++ from the sarcoplasmic reticulum, and this increase in Ca++ triggers muscle contraction by interacting with the myofilaments
