Human Anatomy and Physiology: Nervous System and Special Senses

Comprehensive flashcards reviewing human special senses, central and peripheral nervous systems, cranial nerves, autonomic nervous system divisions, and neurophysiology.

What is the range of wavelengths of visible light detected by the human eye?

Visible light spans wavelengths from $400\,nm$ (violet) to $700\,nm$ (red).

What accommodation mechanisms are shown in the provided diagram for focusing on close objects versus distant objects?

For close objects, the ciliary muscle contracts, relaxing the zonule fibers and making the lens rounded. For distant objects, the ciliary muscle relaxes, making the zonule fibers taut and flattening the lens.

What are the structural causes and corrective lens types for Myopia and Hyperopia?

Myopia (nearsightedness) is caused by an eyeball that is too long or a lens that is too strong, focusing images in front of the retina, and is corrected with a concave lens. Hyperopia (farsightedness) is caused by an eyeball that is too short or a lens that is too weak, focusing images behind the retina, and is corrected with a convex lens.

What anatomical feature characterizes the fovea of the retina?

The fovea is a pinhead-sized depression in the exact center of the retina that serves as the point of most distinct visual clarity and contains exclusively cone cells.

Based on the provided chart, how do rod cells and cone cells compare across retinal location, optimal light conditions, visual acuity, colour sensitivity, and pigment types?

Rod cells are located in the periphery, function best in dim light ('night' vision), have low resolution (many rods to one bipolar cell), sense all wavelengths (achromatic), and contain one pigment type (rhodopsin). Cone cells are concentrated in the fovea, function best in bright light ('day' vision), have high resolution (one cone to one bipolar cell), sense specific wavelengths (red, green, blue), and contain three different iodopsin pigments.

How does glutamate release from rod photoreceptors change between the dark state and exposure to light?

In the dark, rod cells continuously release glutamate, which acts as an inhibitor on bipolar cells. In the light, rod cells hyperpolarize and stop releasing glutamate, relieving inhibition and exciting the bipolar cells.

How does the basilar membrane differentiate between high-frequency and low-frequency sounds?

High-frequency sounds ($20,000\,Hz$) vibrate the short, stiff fibers near the base of the basilar membrane, whereas low-frequency sounds ($20\,Hz$) travel to vibrate the long, floppy fibers at the apex.

How do maculae and semicircular canals differ in their structural components and types of equilibrium monitored?

Maculae are located in the vestibule (utricle and saccule) and contain hair cells with kinocilia and calcium carbonate otoliths to monitor static equilibrium and linear forces. Semicircular canals contain ampullae and cupulae to monitor dynamic equilibrium and rotational movements.

What are the four functional types of lingual papillae, and which ones contain taste buds?

The four types are Vallate (V-shaped posterior, has taste buds), Fungiform (mushroom-shaped scattered, has taste buds), Foliate (side folds, most sensitive, has taste buds), and Filiform (filament-shaped, most numerous, lacks taste buds).

What molecular mechanism allows gustatory cells to transduce sour tastes?

Hydrogen ions ($H^+$) from acidic substances directly block or close potassium ($K^+$) channels, depolarizing the taste cell membrane.

What standard mnemonic represents the functional type (Sensory, Motor, or Both) for each of the 12 cranial nerves?

"Some Say Marry Money But My Brother Says Big Brains Matter Most", where S stands for Sensory, M stands for Motor, and B stands for Both (Sensory and Motor).

How do the origins and fiber lengths of the sympathetic and parasympathetic nervous systems differ?

The sympathetic system originates in the thoracolumbar region ($T_1\text{--}L_2$) with short preganglionic and long postganglionic fibers. The parasympathetic system originates in the craniosacral region (brainstem and sacral plexus) with long preganglionic and very short postganglionic fibers.

Which neurotransmitters are released by preganglionic and postganglionic neurons in the autonomic nervous system?

Both sympathetic and parasympathetic preganglionic fibers release acetylcholine (ACh). Parasympathetic postganglionic fibers release ACh onto muscarinic receptors. Most sympathetic postganglionic fibers release norepinephrine (NE) onto adrenergic receptors.

How does epinephrine affect blood vessels in the intestines versus blood vessels in skeletal muscle?

In intestinal blood vessels, epinephrine binds to $\alpha_1$ adrenergic receptors causing vasoconstriction. In skeletal muscle blood vessels, epinephrine binds to $\beta_2$ adrenergic receptors causing vasodilation.

What is the primary mechanism of action and therapeutic application of Albuterol?

Albuterol is a $\beta_2$-adrenergic agonist that mimics epinephrine to relax smooth muscle in the bronchioles, causing bronchodilation for respiratory disorders.

What are the five sequential components of a basic reflex arc?

1. Receptor, 2. Sensory (afferent) neuron, 3. Integration center (CNS), 4. Motor (efferent) neuron, 5. Effector (muscle or gland).

What connective tissue sheaths encapsulate peripheral nerves at different structural levels?

Endoneurium encloses individual axons, Perineurium bundles nerve fibers into fascicles, and Epineurium surrounds all fascicles to form a complete nerve.

How do tonic receptors differ from phasic receptors in their adaptation properties?

Tonic receptors adapt slowly or not at all to constant stimuli, providing sustained signaling (such as pain and proprioception). Phasic receptors adapt rapidly and signal changes in stimulus intensity.

What structural locations and stimulus types differentiate Tactile (Meissner's) corpuscles from Lamellar (Pacinian) corpuscles?

Tactile (Meissner's) corpuscles reside in dermal papillae of hairless skin and detect light touch and low-frequency vibration. Lamellar (Pacinian) corpuscles reside deep in the dermis/hypodermis and detect deep pressure and high-frequency vibration.

How do NSAIDs relieve pain and inflammation at the chemical level?

NSAIDs block cyclooxygenase (COX) enzymes (such as COX-2) to prevent the synthesis of prostaglandins, which normally lower the activation threshold of nociceptors and promote vascular permeability.

What causes referred pain, such as left arm pain during a heart attack?

Referred pain occurs because visceral and somatic sensory fibers travel along the same spinal pathways; the brain projects the source of sensory input to the somatic region rather than the visceral origin.

What are the primary functional differences between Pyramidal cells and Stellate cells in the cerebral cortex?

Pyramidal cells act as primary output neurons involved in motor processes that send signals away from the cortex. Stellate cells act as input/processing neurons (often interneurons) that process local signals from neighboring neurons.

What distinct roles do Broca's area and Wernicke's area play in language function?

Broca's area (in the frontal lobe) directs the motor execution and planning of speech production. Wernicke's area (in the temporal lobe) is responsible for language comprehension and word interpretation.

What neurochemical deficiency causes Parkinson's disease, and what are its primary clinical signs?

Parkinson's disease is caused by an inadequate level of dopamine in the basal nuclei. Clinical signs include rigidity (increased muscle tone), resting tremors, slowness in coordinating motor activity, and poor gait.

What are the four general classes of brain waves shown in this EEG chart, and what mental or physical state does each represent?

Alpha waves ($8\text{--}13\,Hz$): awake but relaxed state; Beta waves ($14\text{--}30\,Hz$): awake, alert state; Theta waves ($4\text{--}8\,Hz$): common in children, light sleep, or deep meditation; Delta waves ($\le 4\,Hz$): deep sleep or suppressed reticular activating system.

How do flaccid paralysis and spastic paralysis differ following spinal cord trauma?

Flaccid paralysis results from severe damage to ventral root or ventral horn cells, preventing nerve impulses from reaching muscles (causing atrophy and loss of voluntary/involuntary control). Spastic paralysis results from damage to upper motor neurons in the primary motor cortex, keeping spinal reflex arcs intact so muscles contract reflexively without voluntary control.

What four types of neuroglia are located in the central nervous system (CNS), and what are their functions?

1. Astrocytes: support neurons, anchor to capillaries, and regulate chemical environment. 2. Microglia: phagocytize microorganisms and neuronal debris. 3. Ependymal cells: line CSF cavities and circulate CSF via cilia. 4. Oligodendrocytes: form myelin sheaths around CNS axons.

According to this diagram, what sequence of ion channel additions and transport mechanisms builds and maintains the resting membrane potential of $-70\,mV$?

First, abundant $K^+$ leakage channels allow $K^+$ efflux, establishing a negative potential toward $-90\,mV$. Second, adding a few $Na^+$ leakage channels allows $Na^+$ entry, slightly reducing negativity to $-70\,mV$. Third, $Na^+\text{--}K^+$ pumps transport $Na^+$ out and $K^+$ in to compensate for leaking ions and maintain concentration gradients.

How do Graded Potentials differ from Action Potentials in travel distance, amplitude, and gating mechanisms?

Graded potentials operate over short distances (dendrites/soma), decay with distance, vary in amplitude with stimulus strength, and depend on chemically or mechanically gated channels. Action potentials travel long distances down axons, do not decay (all-or-none), maintain constant amplitude, and depend on voltage-gated $Na^+$ and $K^+$ channels.

What channel events drive the depolarization, repolarization, and hyperpolarization phases of an action potential?

Depolarization is driven by the opening of voltage-gated $Na^+$ channels and rapid $Na^+$ influx. Repolarization occurs as $Na^+$ channels inactivate and voltage-gated $K^+$ channels open for $K^+$ efflux. Hyperpolarization results from lingering open $K^+$ channels causing excess $K^+$ efflux before resetting.

How does temporal summation differ from spatial summation in postsynaptic neurons?

Temporal summation occurs when a single presynaptic neuron fires rapidly in high frequency, causing successive EPSPs to add together in time. Spatial summation occurs when multiple presynaptic neurons fire simultaneously at different locations on the postsynaptic cell, combining their graded potentials.