Exam 1/No Quiz- Human Reflex Physiology/Micro. Anatomy/ Organization of Skeletal Muscle Flashcards
What is a reflex?
the communication by neurons in response to a stimulus that are rapid, predictable, and involuntary motor responses
Reflexes occur over neural pathways called ________.
Reflex Arcs
Autonomic (or Visceral) Reflexes are not subject to what?
Conscious control
What structures do Autonomic (or Visceral) Reflexes activate (affect)?
Activate smooth muscles, cardiac muscle, glands of the body
What do Autonomic (or Visceral) Reflexes regulate?
Regulate body functions such as digestion and blood pressure
Somatic Reflexes stimulate what?
Skeletal muscle
What is an example of a somatic reflex?
Rapid withdrawal of your foot from a piece of glass
What is another name for a sensory neuron?
Afferent neuron
What is another name for a motor neuron?
Efferent neuron
What are the five components of a reflex arc?
- Receptor
- Sensory neuron
- Integration center
- Motor neuron
- Effector (muscle or gland)
A nerve encompasses what 3 things?
- Nerve cell processes
- Connective tissue
- Blood vessels
Describe what a monosynaptic reflex is.
Direct communication between motor and sensory neuron (no interneuron)
Describe what a polysynaptic reflex is.
Interneuron facilitates sensory-motor communication
Somatic reflexes are also called what?
Spinal Reflexes
What are the 3 different types of somatic reflexes?
- Stretch Reflexes
- Superficial Cord Reflexes
- Cranial Nerve Reflex
Describe what a stretch reflex is.
Important postural reflexes that act to maintain posture, balance, and locomotion
How do stretch reflexes work?
Stimulates sensory receptors (muscle spindles) in the muscle and causes reflex contraction of the stretched muscle that resists further stretching of the muscle
What are 3 examples of stretch reflexes that we tested in class?
- Patellar reflex
- Jendrassik Maneuver
- Achilles reflex
- Calcaneal tendon reflex
What are 2 examples of superficial cord reflexes?
- Abdominal
2. Plantar reflexes
What receptors do superficial cord reflexes stimulate?
Stimulation of receptors in the skin and mucosae
What do superficial cord reflexes depend on? (brain or spinal cord)
Depend both on brain participation and on the cord-level reflex arc
What is Babinski’s sign?
Damage to the corticospinal tract
What are two cranial nerve reflex tests?
- Corneal Reflex
2. Gag reflex
What cranial nerve is responsible for the corneal reflex?
Trigeminal Nerve (CN V)
What cranial nerve is responsible for the gag reflex?
Cranial nerves IX and X
What are two examples of autonomic reflexes?
- Pupillary light reflex
2. Consensual reflex
When talking about autonomic reflexes, what is a contralateral response?
Reflex observed on one side of the body when the other side has been stimulated
When talking about autonomic reflexes, what is a ipsilateral response?
Reflex occurring on the same side that is stimulated
What is an example of a ipsilateral response?
Pupillary light response
Muscle cell is synonymous with what?
Fiber
Plasma membrane of a muscle cell is called what?
Sarcolemma
Smooth ER is synonymous with what?
Sarcoplasmic ER
Describe the structure of skeletal muscle.
Striated, Multinucleated and Voluntary
What is a sarcomere?
One contractile unit of the muscle
When contracting is length changing?
NO
What does the degree of contraction depend on?
How much the thin and thick filaments overlap
Thin filament is known as what?
Actin
Thick filament is known as what?
Myosin
Define Insertion.
Muscle’s more movable attachment
Define Origin.
Muscle’s fixed attachment
What are the 4 different types of muscles?
- Agonists (Prime movers)
- Antagonists
- Synergists
- Fixators
What are the 7 different ways you can name muscles? (parentheses are just some examples)
- Direction (Rectus, Transverse, Oblique)
- Relative size (Maximus, Minimus, Longus, Brevis)
- Location (Temporalis)
- Number of origins (Biceps, Triceps, Quadriceps)
- Location of muscle’s origin and insertion (Sternocleidomastoid muscle)
- Shape (Deltoid, Trapezius)
- Action (Adductor muscle)
Describe the receptor component of a reflex arc.
The receptor reacts to a stimulus
Describe the sensory neuron component of a reflex arc.
The sensory neuron conducts afferent impulses to the CNS.
Describe the integration center component of a reflex arc.
The integration center consist of one or more synapses in the CNS.
Describe the motor neuron component of a reflex arc.
The motor neuron conducts efferent impulses from the integration center to an effector.
Describe the effector component of a reflex arc.
The effector muscle fibers or glands respond to the efferent impulses by contracting or secreting a product respectively.
Is the patellar reflex monosynaptic or polysynaptic?
monosynaptic
Are most reflex arcs monosynaptic or polysynaptic?
polysynaptic
What are the sensory receptors in stretch reflexes?
Muscle spindles
What region of the spinal cord does the patellar reflex assess?
The L2-L4 level of the spinal cord
What region of the spinal cord does the calcaneal tendon reflex assess?
First two sacral segments of the spinal cord
What reflex arc is the gastrocnemius muscle involved in? (calf muscle)
calcaneal tendon reflex
Where are stretch reflex pathways initiated and completed?
Spinal cord level
In adults, what does the plantar reflex cause?
The toes to flex and move closer together
Where are the receptors for the plantar reflex?
Sole of the foot
What is the response produced with the Babinski’s sign in the plantar reflex?
The toes flare and the great toe moves upward
What does the absence of the corneal reflex indicate?
Damage to the brain stem
In both the pupillary light and consensual reflex (autonomic reflexes) what is the:
- Receptor
- Sensory (Afferent) Neuron
- Integration Center
- Motor (Efferent) Neuron
- Effector
- Retina of the eye
- Optic nerve (CN II)
- Many CNS centers
- Oculomotor nerve (CN III)
- Smooth muscle of the iris
Absence of the pupillary light and consensual reflex indicate what?
Late indication of severe trauma or deterioration of the vital brain stem tissue.
Are I bands light or dark?
Light
Are A bands light or dark?
Dark
What fills the interior of muscle cells?
Myofibrils
What are myofibrils made out of?
Myofilaments; even smaller thread like structures
What are Myofilaments composed of?
Contractile proteins; actin and myosin
What GENERAL 3 important events can be used to describe the contraction of skeletal muscle?
- Excitation of the fibers by an action potential traveling along their length
- Release of calcium ions from the sarcoplasmic reticulum into the sarcoplasm (in response to the action potential)
- Shortening of the muscle cell due to the sliding of the myofilaments inside of it
Define endomysium.
Delicate connective tissue sheath that encloses each muscle fiber.
Define perimysium. What do these form?
- Collagenic membrane that wraps several sheathed muscle fibers.
- Fascicle; fiber bundle
Define epimysium.
Encloses entire muscle; wraps several fascicles together.
What do epimysium blend together to form?
Tendons or sheetlike aponeuroses
What is the function of tendons/aponeuroses?
Attach muscles to each other or indirectly to bones
What is the function of all these connective tissue wrappings of muscle?
- Supporting and binding muscle fibers
- Strengthing the muscle
- Route for entry/exit of nerves and blood vessels that serve the muscle fibers
What is the junction between a nerve fiber (axon) and a muscle cell called?
Neuromuscular junction/End plate
Each motor axon breaks up into many branches called _____.
Axonal terminals
Define a motor unit.
A neuron and all the muscle cells that it simulates.
Define synaptic cleft.
Small fluid filled gap.
What are key words when describing the direction of muscle fibers?
rectus, transverse, and oblique
What are key words when describing the relative size of muscle?
Maximus, minimus, brevis, and longus
What are key words when describing the number of origins of muscles?
Biceps, triceps, or quadriceps
What do agonist/prime movers do?
Muscles that are primarily responsible for producing a particular movement
What do antagonist do?
Muscles that oppose or reverse a movement
When a prime mover is active, the fibers of the antagonist are what?
stretched and relaxed
What do synergist do?
Aid the action of prime movers by reducing undesirable or unnecessary movement
Fixtures are a form of what? What do they do?
- Synergist
2. Imobilize the origin of a prime mover so that all the tension is exerted at the insertion
Define T-tubule.
conveys action potential from sarcolemma deep into cell.
What is stored within the sarcoplasmic reticulum?
Ca++ ions
Describe in detail the early events of muscle stimulation, up to Ca++ release.
- Action potential of motor neuron arrives at axon terminal.
- Neurotransmitters are released from axon terminal by exocytosis. Main excitatory neurotransmitter for skeletal muscle is acetylcholine.
- Acetylcholine diffuses across synaptic cleft to bind to acetylcholine receptors on muscle sarcolemma.
- Sodium channels open on the sarcolemma. Na+ diffuses in which depolarizes sarcolemma membrane which in turn causes a spreading wave of opening sodium channels in a spreading action potential over the sarcolemma.
- The action potential runs down T-tubules. This causes Ca++ to be released from the sarcoplasmic reticulum through calcium channels.
Where is the binding site for myosin heads?
Thin filament
What is the function of troponin?
Protein that binds released Ca++. This causes troponin to change shape, and this causes movement of tropomyosin
What is the function of tropomyosin? When are they uncovered?
Proteins that cover the binding sites for myosin. These sites are uncovered when tropomysin moves
Describe in detail the steps of muscle contraction. (steps right after the Ca++ release)
- Calcium ions bins to troponin which changes shape, unblocking the receptor sites on tropomyosin. The actin active sites are now exposed. The myosin heads of the thick filaments will now bind to these active sites.
- Myosin cross bridge attaches to the actin myofilament
- Working stroke/Pivot stroke: Myosin heads moves thin filament toward the M line. This causes the release of ADP + P
- As a new ATP and Mg++ attaches to the myosin head the cross bridge detaches
- Hydrolysis of ATP to ADP + P occurs (which is what the Mg++ is required for- and it is released at this step) and the myosin head becomes cocked. The heads are now re-attracted to actin.
What does the sliding filament theory state?
Contraction of muscle fibers is caused by sliding of thin filaments over the thick filaments – increasing their amount of overlap.
