Human Anatomy - Nervous System Overview

Vocabulary flashcards covering key terms and definitions from Human Anatomy lecture on the nervous system, spinal nerves, and cranial nerves.

Sensory (Afferent) Neurons

Specialized nerve cells that transmit impulses from sensory receptors in the skin, muscles, or organs toward the central nervous system ($CNS$) via the dorsal root.

Motor (Efferent) Neurons

Neurons that conduct electrical impulses away from the central nervous system ($CNS$) to effectors, such as muscles or glands, typically exiting via the ventral root.

Reflex Arc

The most basic functional unit of the nervous system, consisting of five components:

1. Receptor: Detects the stimulus.

2. Sensory neuron: Transmits the signal to the $CNS$.

3. Integration center: Process the info within the $CNS$.

4. Motor neuron: Conducts the response to the periphery.

5. Effector: The muscle or gland that performs the action.

Monosynaptic Reflex

A simple reflex pathway where the sensory neuron synapses directly onto the motor neuron with no interneurons involved (e.g., the patellar / knee-jerk reflex).

Polysynaptic Reflex

A complex reflex involving one or more interneurons between the sensory and motor neurons, often producing more sophisticated responses like the withdrawal (flexor) reflex.

Olfactory Nerve ($CN\ I$)

A purely sensory nerve dedicated to the sense of smell; it transmits chemical signals from the nasal mucosa to the brain.

Optic Nerve ($CN\ II$)

A purely sensory nerve responsible for vision; it carries visual information from the retina to the primary visual cortex.

Oculomotor Nerve ($CN\ III$)

A primarily motor nerve that controls four extraocular muscles, the muscle that lifts the eyelid, and parasympathetic fibers for pupil constriction.

Trochlear Nerve ($CN\ IV$)

A purely motor nerve that innervates the superior oblique muscle of the eye, facilitating downward and inward eye movement.

Trigeminal Nerve ($CN\ V$)

A mixed (both) nerve; the largest cranial nerve. It provides facial sensation and motor control for the muscles of mastication (chewing).

Abducens Nerve ($CN\ VI$)

A purely motor nerve that innervates the lateral rectus muscle, allowing the eye to move laterally (abduction).

Facial Nerve ($CN\ VII$)

A mixed (both) nerve responsible for muscles of facial expression, taste on the anterior $\frac{2}{3}$ of the tongue, and secretion from tear and salivary glands.

Vestibulocochlear Nerve ($CN\ VIII$)

A purely sensory nerve responsible for equilibrium (balance) and the sense of hearing.

Glossopharyngeal Nerve ($CN\ IX$)

A mixed (both) nerve that handles taste on the posterior $\frac{1}{3}$ of the tongue, swallowing movements, and monitoring blood pressure/chemistry.

Vagus Nerve ($CN\ X$)

A mixed (both) nerve with the widest distribution; it provides major parasympathetic innervation to the thoracic and abdominal viscera (heart, lungs, digestive tract).

Accessory Nerve ($CN\ XI$)

A purely motor nerve that controls the sternocleidomastoid and trapezius muscles, governing head and shoulder movements.

Hypoglossal Nerve ($CN\ XII$)

A purely motor nerve that innervates the muscles of the tongue for speech, manipulation of food, and swallowing.

Frontal Lobe

The anterior part of the cerebral cortex involved in higher-level functions, including voluntary motor control (primary motor cortex), decision-making, personality, and expressive language (Broca's area).

Parietal Lobe

The part of the brain located superiorly and posteriorly to the frontal lobe; it processes somatosensory information like touch, pressure, pain, and spatial awareness.

Temporal Lobe

Located on the lateral sides of the brain; it is primarily responsible for processing auditory information (hearing), language comprehension (Wernicke's area), and memory storage.

Occipital Lobe

The most posterior lobe of the brain, dedicated almost exclusively to processing visual information from the eyes.

Cerebellum

Located inferior to the occipital lobe; it coordinates voluntary movements, maintains posture, and ensures smooth, balanced muscular activity.

Thalamus

A deep brain structure that acts as the primary relay station for all sensory information (except smell) headed to the cerebral cortex.

Hypothalamus

A vital structure for homeostasis; it regulates the autonomic nervous system, body temperature, hunger, thirst, and controls the pituitary gland.

Medulla Oblongata

The lowest part of the brainstem; it contains vital reflex centers for heart rate, blood pressure, and breathing (respiratory rhythm).

Pons

The middle part of the brainstem that acts as a bridge between the cerebrum and cerebellum; it also contains centers that help regulate the depth of breathing.

Midbrain

The most superior part of the brainstem; it plays a role in visual and auditory reflexes (e.g., tracking moving objects or turning toward a loud sound).

Corpus Callosum

A large band of white matter (axons) that connects the left and right cerebral hemispheres, allowing them to communicate and share information.