Muscular System Gross Anatomy and Nervous Tissue Functional Organization

A comprehensive collection of 150 practice flashcards in question-and-answer format covering skeletal muscle anatomy, lever mechanics, fascicle arrangements, nervous system divisions, neuroglial biology, resting and graded potentials, action potential electrophysiology, and synaptic circuitry.

What is the origin (or head) of a skeletal muscle?

The muscle end attached to the more stationary of two bones.

What is the insertion of a skeletal muscle?

The muscle end attached to the bone with the greatest movement.

What is the belly of a skeletal muscle?

The largest portion of the muscle located between the origin and insertion.

What is the structural role of tendons in skeletal muscle anatomy?

Tendons attach muscles to bones.

What is an aponeurosis?

A cordlike or broad, flat tendon.

What is an antagonist muscle?

A muscle that works in opposition to an agonist.

How does the biceps brachii demonstrate the roles of both agonist and antagonist?

The biceps brachii functions as an agonist when lifting weights, but acts as an antagonist when moving a bowling ball backward to prepare to bowl.

What are synergist muscles?

Muscles that work together to cause a movement.

What is a prime mover?

The muscle that plays the major role in accomplishing a specific movement.

What is the function of a fixator muscle?

It stabilizes the joint or joints crossed by the prime mover and prevents movement of the origin of the prime mover.

What are the skeletal attachments (origins and insertion) of the biceps brachii?

It originates on the scapula and inserts on the radial tuberosity of the radius.

What are the skeletal attachments (origins and insertion) of the triceps brachii?

It originates on the scapula and humerus and inserts on the olecranon process of the ulna.

What is an example of a muscle named according to its anatomical location?

Pectoralis.

What are examples of terms used to name muscles based on size?

Maximus and minimus.

What is an example of a muscle named according to its shape?

Deltoid.

What are examples of descriptive terms used to name muscles according to fiber orientation?

Oblique and rectus.

What muscle is named specifically after its points of origin and insertion?

Sternocleidomastoid.

What are examples of terms used to name muscles based on their number of heads?

Biceps and triceps.

What is an example of a muscle named according to its primary function?

Flexor.

What defines a circular fascicle arrangement, and what are two clinical examples?

Fascicles arranged in a circle around an opening that act as sphincters to close the opening; examples include orbicularis oris and orbicularis oculi.

What defines a convergent fascicle arrangement, what is its muscle shape, and what are two examples?

Broadly distributed fascicles that converge at a single tendon to form a triangular shape; examples include pectoralis major and pectoralis minor.

What defines a parallel fascicle arrangement in skeletal muscle?

Fascicles lie parallel to one another and to the long axis of the muscle.

What are the three specific shapes and muscle examples listed for parallel fascicle arrangements in Table 10.1?

Trapezium (trapezius), rhomboidal (rhomboideus), and quadrate (rectus abdominis).

What is the general structural organization of pennate muscles?

Fascicles originate from a tendon that runs the length of the entire muscle in three different patterns.

What defines a unipennate muscle, and what are two examples?

Fascicles are positioned on only one side of the tendon; examples include palmar interosseus and semimembranosus.

What defines a bipennate muscle, and what is a representative example?

Fascicles are positioned on both sides of the tendon; an example is rectus femoris.

What defines a multipennate muscle, and what is an example?

Fascicles are arranged at many places around a central tendon and spread out at angles to many smaller tendons; an example is the deltoid.

What defines a fusiform muscle, and what are two examples?

Fascicles lie parallel to the long axis of the muscle, and the belly of the muscle is larger in diameter than the ends; examples include biceps brachii and triceps brachii.

Examine Table 10.1. What patterns of fascicle arrangement, muscle shapes, and examples are described?

It categorizes circular, convergent (triangular), parallel (trapezium, rhomboidal, quadrate), pennate (unipennate, bipennate, multipennate), and fusiform arrangements along with their functional muscle shapes and representative examples.

In human biomechanics, what anatomical structures act as the force, lever, fulcrum, and weight?

The force is the pull resulting from muscle contraction; the lever is a bone; the fulcrum is a joint; and the weight (resistance) is the body part or external load being moved.

What is the relative arrangement of components in a Class I lever system, and what mechanical device represents it?

The fulcrum is located between the force and the weight (Weight, Fulcrum, Force); an example is a seesaw.

In this lever diagram, which lever classes are depicted, and what anatomical actions do they illustrate?

Class I lever is shown at the atlantooccipital joint (fulcrum = joint, force = posterior neck muscles, weight = head) depressing the back of the head, and Class II lever is shown at the metatarsophalangeal joint (fulcrum = joint, weight = body, force = calf muscles) lifting the body when standing on toes.

What is the relative arrangement of components in a Class II lever system, and what mechanical device represents it?

The weight is located between the fulcrum and the pull/force (Fulcrum, Weight, Force); an example is a wheelbarrow.

How does standing on your toes demonstrate a Class II lever system?

The metatarsophalangeal joint serves as the fulcrum, the body weight serves as the weight, the calcaneus serves as the lever, and the calf muscles provide the upward force to lift considerable weight a short distance.

What class of lever is illustrated in this diagram featuring a shovel and elbow flexion?

Class III lever system, where the pull/force (biceps brachii) is located between the fulcrum (elbow joint) and the weight (forearm and hand), representing the most common lever system in the body.

What are the five major physiological functions of the nervous system?

Maintaining homeostasis, receiving sensory input, integrating information, controlling muscles and glands, and establishing and maintaining mental activity.

What anatomical structures constitute the Central Nervous System (CNS) versus the Peripheral Nervous System (PNS)?

The CNS consists of the brain and spinal cord; the PNS consists of sensory receptors, nerves, ganglia, and plexuses.

What are the general operational functions of the CNS versus the PNS?

The CNS processes information, initiates responses, and integrates mental processes; the PNS detects stimuli and transports information to and from the CNS in the form of action potentials.

What are sensory receptors in the peripheral nervous system?

Endings of neurons or separate specialized cells that detect stimuli such as temperature, pain, touch, pressure, light, sound, and odors.

What is a nerve, and how many pairs of cranial and spinal nerves exist?

A bundle of axons extending from the CNS to the periphery; there are $12$ pairs of cranial nerves originating from the brain and $31$ pairs of spinal nerves originating from the spinal cord.

What is a ganglion in the peripheral nervous system?

A collection of neuron cell bodies located outside the CNS.

What is a plexus in the peripheral nervous system?

An extensive network of axons, and sometimes neuron cell bodies, located outside the CNS.

What is the functional difference between the sensory and motor divisions of the PNS?

The sensory (afferent) division transmits action potentials from sensory receptors toward the CNS, whereas the motor (efferent) division transmits action potentials from the CNS toward effector organs.

What are the defining characteristics of the somatic nervous system (SNS)?

It transmits impulses from the CNS to skeletal muscles under voluntary control via a single-neuron system whose cell bodies lie in the CNS and axons extend to the neuromuscular junction.

What is a synapse?

The junction of a nerve cell with another cell, such as a neuromuscular junction between a neuron and a skeletal muscle cell.

What are the defining characteristics of the autonomic nervous system (ANS)?

It provides involuntary/subconscious control from the CNS to smooth muscle, cardiac muscle, and certain glands via a two-neuron system (first neuron from CNS to ganglion; second neuron from ganglion to effector).

What is the primary role of the sympathetic division of the ANS?

It prepares the body for physical activity and stress ('fight or flight').

What is the primary role of the parasympathetic division of the ANS?

It regulates resting or vegetative functions and promotes a return to homeostasis ('rest and digest').

What is the enteric nervous system, and why is it classified under the ANS?

Plexuses within the wall of the digestive tract that can control digestion independently of the CNS, but are considered part of the ANS because sympathetic and parasympathetic neurons contribute to them.

What is the general sequential organization of information flow across the nervous system?

Receptor (\rightarrow) Sensory NS (\rightarrow) CNS (\rightarrow) Motor NS (\rightarrow) Effector.

What are the two primary cell types comprising nervous tissue?

Neuroglia (which support and protect neurons) and neurons (nerve cells that receive stimuli and transmit action potentials).

What are the three structural components of a typical neuron?

The cell body (soma), dendrites (input processes), and the axon (output process).

What is the functional role of neuron dendrites?

They act as input zones, carrying electrical information toward the cell body.

What is the functional role of a neuron axon?

It acts as an output pathway, transmitting electrical information away from the cell body.

What major organelles and specialized structures are located within the neuron cell body (soma)?

Nucleus, nucleolus, Nissl bodies (rough endoplasmic reticulum), Golgi apparatus, mitochondria, and neurofilaments.

What are dendritic spines?

Small protuberances on dendrites where axons form synapses.

What are the axon hillock and the trigger zone?

The axon hillock is the initial cone-shaped area where the axon begins; the trigger zone is the site where action potentials are generated.

What are axoplasm and axolemma?

Axoplasm is the cytoplasm of the axon, and axolemma is the plasma membrane surrounding the axon.

What are telodendria, presynaptic terminals, and synaptic vesicles?

Telodendria are branches at the axon terminal; presynaptic terminals (terminal boutons) are their enlarged ends; and synaptic vesicles are membrane sacs inside terminals storing neurotransmitters.

What cargo is moved by anterograde axonic transport?

Proteins, organelles, and vesicles moving away from the cell body toward axon terminals for growth, repair, and renewal.

What cargo and pathogens can travel via retrograde axonic transport toward the cell body?

Damaged organelles, recycled plasma membrane, endocytosed substances, as well as rabies virus and herpes virus entering damaged skin.

What are the three functional classifications of neurons?

Sensory (afferent) neurons, motor (efferent) neurons, and interneurons (association neurons).

Identify the three structural types of neurons shown from left to right in this diagram.

(a) Multipolar neuron (many dendrites and one axon), (b) Bipolar neuron (one dendrite and one axon), and (c) Pseudo-unipolar neuron (single process extending from soma dividing into two axon branches).

What characterizes a multipolar neuron, and where is it predominantly found?

It possesses many dendrites and a single axon; it represents most neurons in the CNS as well as motor neurons.

What characterizes a bipolar neuron, and where is it located in the body?

It possesses one dendrite and one axon; it functions as a sensory neuron in the retina of the eye and the nose.

What characterizes a unipolar (pseudo-unipolar) neuron, and what is its role?

It has a single process dividing into two branches that function as a single axon with dendrite-like sensory receptors extending into the periphery.

What is the structural morphology of astrocytes, and what surfaces do their foot processes cover?

They are star-shaped cells whose foot processes cover the surfaces of blood vessels, neurons, and the pia mater membrane of the brain and spinal cord.

How do astrocytes contribute to the blood-brain barrier (BBB)?

They produce chemicals that promote tight junctions between endothelial cells of brain capillaries, creating a selective permeability barrier.

What are the permeability rules across the blood-brain barrier regarding polar and nonpolar substances?

Nonpolar (lipid-soluble) substances (e.g., nicotine, ethanol) pass freely, whereas polar (water-soluble) substances (e.g., amino acids, glucose) cannot pass without mediated transport.

Where are ependymal cells located in the central nervous system?

They line the ventricles (cavities) of the brain and the central canal of the spinal cord.

What are the two specialized roles of ependymal cells concerning cerebrospinal fluid (CSF)?

Ciliated ependymal cells help move CSF through brain cavities and the central canal, while ependymal cells on the surface of choroid plexuses secrete CSF.

What are microglia, and what is their primary function?

Small, mobile phagocytic neuroglial cells that act as the immune cells of the CNS.

What is the role of oligodendrocytes in the CNS?

They form insulating myelin sheaths around axons within the CNS, with a single oligodendrocyte wrapping portions of several axons.

What is the function and chemical nature of Schwann cells (neurolemmocytes)?

They form myelin sheaths around axons in the PNS; their cell membranes are primarily phospholipid-rich.

What are satellite cells in the peripheral nervous system?

Specialized neurolemmocytes that surround neuron cell bodies (soma) within ganglia to provide support and nutrients.

What six types of neuroglial cells and their functions are outlined in Table 11.1?

CNS: Astrocytes (structural support, BBB regulation), Ependymal cells (CSF movement/secretion), Microglia (phagocytosis), Oligodendrocytes (CNS myelin sheaths); PNS: Schwann cells (PNS myelin sheaths) and Satellite cells (ganglionic soma support).

What structural differences between myelinated and unmyelinated axons are shown in this diagram?

(a) Myelinated axons are wrapped by successive layers of Schwann cell membrane with exposed gaps called Nodes of Ranvier, whereas (b) unmyelinated axons rest in simple invaginations of Schwann cells without multiple wrapping layers.

At what age is the development of myelin sheaths typically complete in humans?

$1$ year.

Which clinical diseases are associated with the degeneration of myelin sheaths?

Multiple sclerosis and some cases of diabetes mellitus.

What characterizes unmyelinated axons in nervous tissue?

They rest in invaginations of Schwann cells or oligodendrocytes without wrapping repeatedly around the axon; they appear as gray matter.

According to this peripheral nerve injury diagram, what determines whether an injured axon successfully regenerates or leads to muscle atrophy?

If the two injured axon ends remain in close proximity, Schwann cells guide successful regeneration and the muscle undergoes hypertrophy; if the ends are not in close proximity, reinnervation fails and the muscle remains atrophied.

What structures compose gray matter, and what is its primary role?

Unmyelinated axons, cell bodies, dendrites, and neuroglia; it performs integrative functions.

What structures compose white matter, and what are nerve tracts?

Bundles of myelinated axons; nerve tracts are myelinated axons within the CNS that propagate action potentials from one CNS area to another.

How does the anatomical arrangement of gray and white matter differ between the brain and the spinal cord?

In the brain, gray matter forms the outer cortex and inner nuclei while white matter is deeper; in the spinal cord, white matter is on the outside and gray matter is deeper.

According to Table 11.2, what are the representative concentrations of potassium ($K^+$) in intracellular fluid (ICF) versus extracellular fluid (ECF)?

ICF concentration is $148\,mEq/L$ and ECF concentration is $5\,mEq/L$.

According to Table 11.2, what are the representative concentrations of sodium ($Na^+$) in intracellular fluid (ICF) versus extracellular fluid (ECF)?

ICF concentration is $10\,mEq/L$ and ECF concentration is $142\,mEq/L$.

According to Table 11.2, what are the representative concentrations of calcium ($Ca^{2+}$), chloride ($Cl^-$), and proteins in ICF versus ECF?

$Ca^{2+}$: $<1\,mEq/L$ (ICF) vs $5\,mEq/L$ (ECF); $Cl^-$: $4\,mEq/L$ (ICF) vs $103\,mEq/L$ (ECF); Proteins: $56\,mEq/L$ (ICF) vs $16\,mEq/L$ (ECF).

What does Table 11.2 show regarding the principal cations and anions in intracellular and extracellular fluids?

It shows that ICF has high $K^+$ ($148\,mEq/L$) and proteins ($56\,mEq/L$) totaling $200\,mEq/L$, while ECF has high $Na^+$ ($142\,mEq/L$) and $Cl^-$ ($103\,mEq/L$) totaling $155\,mEq/L$.

What two physiological processes maintain the ion concentration gradients across the plasma membrane?

The sodium-potassium ($Na^+/K^+$) pump and selective membrane permeability.

Why are intracellular protein anions trapped inside the plasma membrane?

They are synthesized inside the cell, are large, and do not dissolve in the phospholipid bilayer of the membrane.

Why do chloride ions ($Cl^-$) tend to exit the resting cell?

They are electrostatically repelled by the negatively charged intracellular proteins and exit through always-open nongated $Cl^-$ channels.

How does the resting membrane permeability to potassium ($K^+$) compare to that of sodium ($Na^+$)?

The plasma membrane is $50\text{--}100$ times more permeable to $K^+$ than to $Na^+$ due to the presence of many more $K^+$ leak channels.

What two opposing forces govern the diffusion of potassium ($K^+$) across the resting cell membrane?

The tendency of $K^+$ to diffuse out down its chemical concentration gradient is opposed by the electrical attraction pulling positive $K^+$ back toward negative intracellular proteins.

What is a ligand-gated ion channel, and what is an example of its operation?

A channel that opens or closes in response to a chemical ligand binding to a receptor glycoprotein, such as acetylcholine binding to its receptor on a $Na^+$ channel, allowing $Na^+$ to enter.

What is a voltage-gated ion channel, and what are the most common ions regulated by them?

A channel that opens or closes in response to small voltage changes across the cell membrane; the most common are $Na^+$ and $K^+$ channels.

In which muscle tissues are voltage-gated calcium ($Ca^{2+}$) channels particularly important?

Cardiac muscle and smooth muscle.

What specific stimuli activate touch receptors and temperature receptors in the skin?

Touch receptors respond to mechanical stimulation of the skin, whereas temperature receptors respond to temperature changes in the skin.

What is the typical potential difference across the plasma membrane of a resting neuron?

$-70\text{ to }-90\,mV$.

What is the pumping ratio and energy source of the sodium-potassium ($Na^+/K^+$) pump?

It pumps $3\,Na^+$ out of the cell in exchange for $2\,K^+$ into the cell, driven by ATP hydrolysis.

What nine characteristics responsible for the resting membrane potential are presented in Table 11.3?

High ICF $K^+$ and ECF $Na^+$, $50\text{--}100$x greater $K^+$ permeability via leak channels, trapped intracellular protein anions, $K^+$ diffusion out, negative charge development inside attracting $K^+$, equilibrium establishment, potential difference in millivolts, RMP proportional to potential for $K^+$ diffusion, and minimal ion flow at equilibrium.