Updated BMS308 Exam 3 Review Questions

What are the two main branches of the Peripheral Nervous System (PNS)?

Sensory (afferent) and Motor (efferent)

What type of muscle does the somatic motor branch of the PNS control?

Skeletal muscle

Which muscles are controlled by the autonomic motor branch of the PNS?

Smooth and cardiac muscle, and glands

What are the two divisions of the autonomic nervous system?

Sympathetic and Parasympathetic

Where are the sympathetic nerves located?

From T1 to L2 of the spinal cord

Where do parasympathetic nerves originate?

From the brainstem and S2 to S4 of the spinal cord

What is the function of the conus medullaris?

It is the tapered end of the spinal cord.

What are the two types of matter found in the spinal cord?

White matter and Gray matter

What is the primary function of dorsal horns in the spinal cord?

Sensory processing

What type of neuron is primarily found in the sensory division of the PNS?

Unipolar neurons

What neurotransmitter is released by preganglionic neurons in both sympathetic and parasympathetic systems?

Acetylcholine (ACh)

What is the primary neurotransmitter used by postganglionic sympathetic neurons?

Norepinephrine (NE)

What are the major effects of the sympathetic nervous system?

Increased heart rate, bronchodilation, vasoconstriction of skin, and decreased GI motility.

What is the primary function of the parasympathetic nervous system?

Rest and digest functions

Which cranial nerve is responsible for pupil constriction?

Cranial Nerve III (Oculomotor nerve)

What is the role of the adrenal medulla in the sympathetic nervous system?

It releases epinephrine and norepinephrine for prolonged sympathetic effects.

What is the structure of the neuromuscular junction (NMJ)?

It is where a motor neuron communicates with a muscle fiber, always resulting in an excitatory postsynaptic potential (EPSP).

What triggers the release of acetylcholine at the neuromuscular junction?

The influx of calcium ions (Ca²⁺) into the presynaptic terminal.

What is the function of acetylcholinesterase (AChE) at the NMJ?

It breaks down acetylcholine to terminate the signal.

What are the three types of muscle tissue?

Skeletal, cardiac, and smooth muscle

What is the basic structural unit of a muscle fiber?

Sarcomere

What is the role of T-tubules in muscle fibers?

They carry action potentials inward to facilitate muscle contraction.

What is the primary function of the hypothalamus in relation to the autonomic nervous system?

It acts as the master controller of the ANS.

What is the difference in the number of neurons between somatic and autonomic pathways?

Somatic pathways have 1 neuron, while autonomic pathways have a 2-neuron chain.

What are the three types of filaments in a sarcomere?

Thick (myosin), thin (actin, troponin, tropomyosin), and elastic (titin).

What does the A band in a sarcomere consist of?

Thick and thin filaments (constant length).

What is the sliding filament theory?

Filaments slide past each other without shortening; the sarcomere shortens while the A band remains the same.

What is required for muscle contraction?

Calcium ions (Ca²⁺) and ATP.

What are the steps of the crossbridge cycle?

1. Myosin binds actin; 2. Power stroke occurs (ADP + Pi leave); 3. ATP binds and detaches myosin; 4. ATP hydrolysis recocks the myosin head.

What is the role of Ca²⁺ in excitation-contraction coupling?

Ca²⁺ binds to troponin, causing tropomyosin to move and allowing crossbridge formation.

What happens during muscle relaxation?

Ca²⁺ is pumped back into the sarcoplasmic reticulum via Ca²⁺-ATPase.

What distinguishes isometric from isotonic contractions?

Isometric: tension increases while length remains the same; Isotonic: tension is constant while length changes.

What is tetany in muscle physiology?

Sustained maximal contraction due to high levels of Ca²⁺.

What are the three main ATP sources for muscle contraction?

1. Creatine phosphate (immediate); 2. Anaerobic glycolysis (fast, low yield); 3. Oxidative phosphorylation (slow, high yield).

What are the functions of the cardiovascular system?

Transport oxygen, carbon dioxide, nutrients, hormones, and wastes; maintain blood pressure, pH, and temperature.

What is the path of deoxygenated blood through the heart?

SVC/IVC → Right Atrium → Tricuspid Valve → Right Ventricle → Pulmonary Valve → Pulmonary Arteries → Lungs.

What is the difference between arteries and veins?

Arteries carry blood away from the heart (usually oxygenated), while veins carry blood toward the heart (usually deoxygenated).

What are the two main types of heart valves?

Atrioventricular (AV) valves and semilunar valves.

What is the cardiac cycle?

The sequence of events in one heartbeat, including systole (contraction) and diastole (relaxation).

What is the role of the SA node in heart rate regulation?

The SA node generates action potentials that initiate heartbeats.

What are the characteristics of cardiac muscle cells?

Striated, branched, involuntary, with intercalated discs and calcium sourced from both the sarcoplasmic reticulum and extracellular fluid.

What is the significance of intercalated discs in cardiac muscle?

They contain desmosomes (prevent cells from pulling apart) and gap junctions (allow electrical coupling).

What is the mean arterial pressure (MAP) formula?

MAP ≈ diastolic pressure + 1/3 pulse pressure.

What is hyperemia?

Increased blood flow due to heightened metabolic activity or restoration of blood flow after occlusion.

What is the tunica media in blood vessels?

The middle layer composed of smooth muscle, responsible for vasoconstriction and blood pressure control.

What is the primary determinant of total peripheral resistance (TPR)?

Vessel radius is the most important factor affecting resistance.

What are the three types of muscle fibers?

1. Slow Oxidative (Type I) - fatigue-resistant; 2. Fast Glycolytic (Type IIb) - fatigues quickly; 3. Fast Oxidative (Type IIa) - intermediate characteristics.

What is the role of the papillary muscles and chordae tendineae?

They prevent AV valve prolapse during ventricular contraction.

What is the significance of the left ventricle's thickness?

It is the thickest chamber because it pumps blood against systemic resistance.

What structures extend inferiorly from the conus medullaris?

The filum terminale and cauda equina.

Where are the cervical and lumbar enlargements of the spinal cord located?

Corresponding to the origin of nerves for the upper and lower limbs, respectively.

How are the spinal cord meninges related to the brain meninges?

They are continuous.

How many segments of the spinal cord are there for each region?

C8, T12, L5, S5, Co1.

What is white matter in the spinal cord composed of?

Myelinated tracts, including ascending sensory and descending motor pathways, organized into funiculi.

What are the three types of gray matter horns in the spinal cord?

Dorsal (sensory), Ventral (somatic motor), and Lateral (autonomic motor, T1-L2).

Which root does afferent (sensory) information enter the spinal cord through?

The dorsal root.

Which root does efferent (motor) information exit the spinal cord through?

The ventral root.

What is the dominant neuron type in the motor division of the PNS?

Multipolar neurons.

What neurotransmitter is used by parasympathetic postganglionic neurons?

Acetylcholine (ACh) acting on muscarinic receptors.

What neurotransmitter is used by sympathetic postganglionic neurons?

Norepinephrine (NE) acting on adrenergic receptors (alpha/beta).

What is the exception for sympathetic postganglionic neurotransmitters?

Sweat glands are innervated by sympathetic neurons releasing ACh acting on muscarinic receptors.

Where are sympathetic chain ganglia located?

Running alongside the vertebrae, primarily innervating the thorax and body wall.

Where are collateral ganglia (celiac, superior mesenteric, inferior mesenteric) located?

In the abdomen and pelvis, innervating abdominal and pelvic organs.

What role do the pelvic splanchnic nerves (S2-S4) play in parasympathetic innervation?

They innervate the bladder, reproductive organs, and distal colon.

Why does the sympathetic nervous system's effects last longer than the parasympathetic's?

Sympathetic effects are mediated by NE (and circulating Epi), which are broken down slower than ACh, and Epi has a longer duration of action.

What are the major brain centers that regulate the ANS?

Hypothalamus (master controller), reticular formation (autonomic centers), spinal cord (reflexes), and limbic system (emotion).

What are the primary functions regulated by the hypothalamus?

ANS, endocrine system (pituitary), temperature, hunger/thirst, emotional responses, and sleep/wake cycles.

Where is the hypothalamus located?

In the diencephalon.

Where is the reticular formation located?

In the brainstem, from the midbrain to the medulla.

What is autonomic dysreflexia?

A condition characterized by excessive sympathetic activation, often seen in spinal cord injuries above T6.

What is neurogenic shock?

A type of distributive shock caused by damage to the nervous system, leading to loss of sympathetic tone and vasodilation.

What is the effect of excitatory postsynaptic potentials (EPSPs) on a motor neuron?

They depolarize the motor neuron, making it more likely to fire an action potential.

What is the effect of inhibitory postsynaptic potentials (IPSPs) on a motor neuron?

They hyperpolarize the motor neuron, making it less likely to fire an action potential.

What is the neurotransmitter and receptor at the NMJ, and what is the resulting potential?

Acetylcholine (ACh) acting on nicotinic receptors, always resulting in an EPSP.

How does the size of a motor unit relate to muscle control?

Small motor units provide fine control (e.g., eyes, fingers), while large motor units provide strength (e.g., legs).

What are the five characteristics of muscle tissue?

Contractile, Excitable, Conductive, Extensible, and Elastic.

What is the structural hierarchy of a muscle?

Muscle → fascicle → fiber → myofibril → sarcomere → filaments.

What are the key components of a muscle fiber's internal structure?

Sarcolemma (membrane), sarcoplasm (cytoplasm), sarcoplasmic reticulum (SR) for Ca²⁺ storage, T-tubules (carry AP inward), and terminal cisternae (SR enlargements forming triads).

Why do muscle fibers have multiple nuclei?

Due to the fusion of multiple myoblasts during development.

What are the three types of filaments within a sarcomere?

Thick filaments (myosin), thin filaments (actin, troponin, tropomyosin), and elastic filaments (titin).

What defines a sarcomere?

The region between two Z discs.

Describe the process of excitation-contraction coupling.

A muscle AP travels down T-tubules, activating DHP receptors which trigger ryanodine receptors on the SR to release Ca²⁺. Ca²⁺ binds troponin, moving tropomyosin to expose actin binding sites, allowing crossbridge formation.

How does muscle relaxation occur?

Ca²⁺ is actively pumped back into the sarcoplasmic reticulum by Ca²⁺-ATPase pumps.

What are the three phases of a muscle twitch?

Latent period (EC coupling), Contraction (crossbridge cycling), and Relaxation (Ca²⁺ reuptake).

What is temporal summation in muscle physiology?

Increased frequency of action potentials leading to a stronger contraction due to incomplete relaxation between stimuli.

What is motor unit summation?

Recruiting additional motor units to increase the force of contraction.

What factors influence the force of muscle contraction?

Number of motor units recruited (size principle: small to large), size of individual muscle fibers, optimal length for filament overlap, and load.

What ATP source is primarily used during light to moderate exercise?

Oxidative phosphorylation.

What ATP source is primarily used during intense exercise?

Fast glycolysis, leading to lactate production.

What are serous membranes?

Membranes that line closed body cavities (pleura, pericardium, peritoneum) and produce fluid to reduce friction.

What are mucous membranes?

Membranes that line cavities open to the outside environment (respiratory, digestive, urinary, reproductive tracts).

What is the cutaneous membrane?

The skin.

What is the pericardial sac?

A double-layered serous membrane surrounding the heart, consisting of the parietal and visceral pericardium, which reduces friction, anchors the heart, and prevents overfilling.

Trace the path of oxygenated blood through the heart and systemic circuit.

Pulmonary veins → Left Atrium → Mitral Valve → Left Ventricle → Aortic Valve → Aorta → Body.

What are the receiving chambers of the heart?

The atria.

What are the distributing chambers of the heart?

The ventricles.

What action causes the AV valves to close and semilunar valves to open?

Ventricular contraction.

What action causes the semilunar valves to close and AV valves to open?

Ventricular relaxation.

What is systole?

The phase of the cardiac cycle involving contraction of the heart chambers.

What is diastole?

The phase of the cardiac cycle involving relaxation of the heart chambers.