Human Anatomy and Physiology: Nervous and Cardiovascular Systems

Comprehensive review flashcards covering nervous system organization, neurocytology, brain and spinal anatomy, sensory pathways of the ear, cardiac anatomy, blood pathways, cardiac conduction, hemodynamics, blood histology, and cardiovascular clinical conditions.

What is the primary difference in composition between white matter and gray matter in the central nervous system?

White matter consists of a dense collection of myelinated fibers, whereas gray matter consists of unmyelinated fibers and neuron cell bodies.

How do the afferent and efferent divisions of the peripheral nervous system (PNS) differ in directional signaling?

The afferent division brings sensory information away from sensory receptors toward the central nervous system (CNS), while the efferent division carries motor commands from the CNS to peripheral effectors (muscles and glands).

What are the contrasting physiological roles of the sympathetic and parasympathetic nervous systems?

The sympathetic nervous system drives the "fight or flight" response, elevating metabolic rate and alertness during stress. The parasympathetic nervous system (craniosacral division) controls "rest & digest" activities, conserving energy and lowering metabolic rate to regulate lacrimation, salivation, urination, digestion, and defecation.

Based on the provided illustration of neuron types, what structural characteristic distinguishes a pseudounipolar neuron from a bipolar neuron?

A pseudounipolar neuron has continuous dendrites and an axon with its cell body offset to the side, whereas a bipolar neuron has its soma positioned centrally between a single fused dendrite at one end and a single axon at the other.

What are the four primary functions of astrocytes in the central nervous system?

1. Controlling the interstitial environment by taking up $K^+$, $H_2O$, nutrients, and recycling neurotransmitters. 2. Maintaining the blood-brain barrier (BBB) by enveloping capillaries. 3. Providing a 3D structural framework, mechanical strength, and ATP production. 4. Repairing damaged neural tissue by forming scar tissue.

What specific roles do oligodendrocytes, microglia, and ependymal cells perform in the CNS?

Oligodendrocytes form myelin sheaths around CNS axons; microglia are mesoderm-derived phagocytes that act as a security force to eliminate debris and pathogens; ependymal cells line brain ventricles and the spinal central canal to circulate, monitor, and cushion neural tissue with cerebrospinal fluid (CSF).

According to the human brain development table, which secondary brain vesicles and adult brain regions develop from the primary vesicle prosencephalon?

The prosencephalon develops into two secondary vesicles: the telencephalon (which becomes the cerebrum) and the diencephalon (which remains the diencephalon at birth).

What major structures compose the diencephalon, and what are their respective functions?

The diencephalon consists of the epithalamus (contains the pineal gland and choroid plexus for CSF production), thalamus (the relay station for sensory and motor impulses), and hypothalamus (the visceral control center that regulates temperature, water balance, metabolism, emotions, pituitary gland activity, and produces ADH and oxytocin).

Through which anatomical passages does cerebrospinal fluid (CSF) flow from the lateral ventricles down into the spinal cord?

CSF moves from the lateral ventricles through the interventricular foramen (foramen of Monro) into the third ventricle, passes through the aqueduct of the midbrain (cerebral aqueduct) into the fourth ventricle, and then enters the central canal of the spinal cord or subarachnoid space.

What is the sequence of the cranial and spinal meninges from superficial to deep?

Dura mater (outer tough fibrous layer), arachnoid mater (middle web-like layer), and pia mater (innermost delicate layer adhering to the neural surface), remembered by the acronym DAP.

What are the daily production rate, total circulating volume, and replacement turnover time of cerebrospinal fluid (CSF)?

CSF is produced at approximately $500\,\text{mL/day}$, maintains a typical circulating volume of about $150\,\text{mL}$, and is completely replaced every $8\,\text{hours}$.

What types of nerve fibers travel through the dorsal root versus the ventral root of a spinal nerve?

The dorsal root (and dorsal root ganglion) contains sensory (afferent) nerve fibers, whereas the ventral root carries motor (efferent) nerve fibers, including somatic and visceral motor outputs.

In which spinal cord segments is the lateral gray horn present, and what functional fibers originate there?

The lateral horn is located in spinal cord segments T1–L2 and S2–S4, and it contains cell bodies of preganglionic autonomic nervous system (ANS) motor neurons supplying smooth muscle, cardiac muscle, and glands.

What are the six sequential steps of signal transmission at the neuromuscular junction (NMJ)?

1. An action potential reaches the motor neuron axon terminal. 2. Voltage-gated calcium channels open and $Ca^{2+}$ enters the terminal. 3. $Ca^{2+}$ entry triggers exocytosis of acetylcholine (ACh) vesicles. 4. ACh diffuses across the synaptic cleft and binds sarcolemma receptors. 5. Ligand-gated channels open, allowing $Na^+$ in and $K^+$ out to depolarize the membrane. 6. Acetylcholinesterase degrades ACh in the synaptic cleft, closing the channels.

What are the three auditory ossicles of the middle ear and their mechanical purpose?

The malleus (hammer), incus (anvil), and stapes (stirrup); they amplify and transduce sound wave vibrations from the air of the tympanic membrane to the fluid-filled oval window of the inner ear.

Identify the inner ear sensory structure shown and explain its sensory function.

This is the macula of the otolith organs (utricle and saccule). It senses static equilibrium, gravity, and linear acceleration as movement causes otoconia (statoconia) on the otolithic membrane to shift, bending hair cell stereocilia and kinocilia to depolarize the vestibular branch of CN VIII.

Based on the diagram of the semicircular canal ampulla, how does the cupula mediate dynamic equilibrium?

Rotational or angular movement of the head displaces endolymph within the semicircular canal, deflecting the gelatinous cupula within the crista ampullaris, which bends the hair cells' stereocilia and kinocilium to alter afferent nerve firing.

What fluid fills the cochlear duct (scala media), and which sensory structure does it house?

The cochlear duct is filled with endolymph (rich in $K^+$) and houses the spiral organ of Corti, where hair cell mechanoreceptors contact the tectorial membrane.

According to the lecture notes, which cranial nerves innervate the superior oblique and lateral rectus extrinsic eye muscles?

The superior oblique is innervated by cranial nerve IV (CN IV), and the lateral rectus is listed as innervated by CN IV.

What is the complete anatomical pathway of blood flow through the heart and lungs starting from systemic deoxygenated return?

Venae Cavae $\rightarrow$ Right Atrium $\rightarrow$ Tricuspid Valve $\rightarrow$ Right Ventricle $\rightarrow$ Pulmonary Valve $\rightarrow$ Pulmonary Artery $\rightarrow$ Lungs (oxygenated) $\rightarrow$ Pulmonary Veins $\rightarrow$ Left Atrium $\rightarrow$ Mitral Valve $\rightarrow$ Left Ventricle $\rightarrow$ Aortic Valve $\rightarrow$ Aorta $\rightarrow$ Systemic Arteries.

According to the conducting system timeline diagram, what specific electrical and mechanical event occurs between $50\,\text{msec}$ and $150\,\text{msec}$?

Atrial contraction begins while the AV node delays the electrical impulse by $100\,\text{msec}$ before allowing activity to proceed to the AV bundle.

What electrical events in the cardiac cycle correspond to the P wave, QRS complex, and T wave on an electrocardiogram?

The P wave represents atrial depolarization prior to atrial contraction; the QRS complex represents ventricular depolarization and masking atrial repolarization; the T wave represents ventricular repolarization.

What mechanical heart events produce the characteristic "lub" and "dup" heart sounds?

The "lub" sound is caused by the closure of the atrioventricular (AV) valves at the onset of ventricular systole, and the "dup" sound is caused by the closure of the semilunar valves at the end of ventricular systole.

What are the three structural tunics of arteries and veins, and what is the primary role of each?

1. Tunica intima: innermost endothelium providing a slick, low-friction surface. 2. Tunica media: middle layer of smooth muscle and elastic fibers regulated by the sympathetic nervous system to adjust vessel diameter. 3. Tunica externa: outermost fibrous connective tissue sheath providing structural support.

What are the standard physical and chemical characteristics of human blood (viscosity, temperature, pH, and volumes)?

Blood is $5\times$ more viscous than water, has an average temperature of approximately $100.4\,^{\circ}\text{F}$, a pH between $7.35\text{--}7.45$, and a typical volume of $5\text{--}6\,\text{L}$ in males and $4\text{--}5\,\text{L}$ in females.

What are the three major classes of plasma proteins, their relative abundance, and their primary functions?

1. Albumins ($60\%$): maintain colloid osmotic pressure. 2. Globulins ($35\%$): act as immunoglobulins (antibodies) and transport binding proteins. 3. Fibrinogen ($4\%$): converted into insoluble fibrin strands for blood clot formation.

What are the three primary phases of hemostasis, and what enzyme mediates final clot dissolution (fibrinolysis)?

The three phases are: (1) Vascular phase (vascular spasm lasting $\sim 30\,\text{minutes}$), (2) Platelet phase (platelet aggregation forming a plug), and (3) Coagulation phase (fibrin clot formation). Clot dissolution is achieved when tissue plasminogen activator (t-PA) converts plasminogen into plasmin, an enzyme that digests fibrin.

What distinguishes systolic heart failure from diastolic heart failure regarding ejection fraction and ventricular pathology?

Systolic heart failure is a pumping defect with an ejection fraction $<40\%$ caused by weakened or scarred myocardium unable to contract effectively. Diastolic heart failure is a filling defect where the ventricular wall becomes stiff, noncompliant, or hypertrophied, preventing adequate ventricular filling despite preserved contractility.

How do first-degree and second-degree heart blocks present on an electrocardiogram?

First-degree heart block presents with a fixed, consistent prolongation of the PR interval. Second-degree heart block presents either with progressive prolongation of the PR interval until a QRS complex is dropped (Type 1), or intermittent dropped QRS complexes without progressive PR lengthening due to failed AV node conduction (Type 2).