WEEK 11 Anatomy

What are the three main structural components of a neuron?

Dendrites, soma (cell body), and axon.

What is the function of dendrites?

To receive neural signals from other neurons.

What is the function of the soma (cell body)?

To integrate incoming signals and maintain cellular function.

What is the function of the axon?

To conduct electrical impulses away from the soma.

What is the role of axon terminals?

To transmit signals to other neurons or target tissues via synaptic release.

What are the two major structural types of neurons?

Multipolar neurons and unipolar (pseudounipolar) neurons.

What is a multipolar neuron?

A neuron with one axon and multiple dendrites; common in the CNS.

What is a unipolar (pseudounipolar) neuron?

A neuron with one process that branches into peripheral and central axons; found in sensory ganglia.

What are the two major functional divisions of the nervous system?

The somatic nervous system and the autonomic nervous system (ANS).

What does the somatic nervous system control?

Voluntary skeletal muscle activity.

What does the autonomic nervous system regulate?

Involuntary functions such as heart rate, digestion, and respiratory rate.

Where are sympathetic preganglionic neuron cell bodies located?

In the lateral horn of the spinal cord grey matter at T1–L2.

Through what nerves do sympathetic preganglionic axons exit the CNS?

Spinal nerves at T1–L2 levels.

Where are parasympathetic preganglionic neuron cell bodies located?

In cranial nerve nuclei in the brainstem and sacral spinal cord grey matter.

Through what do parasympathetic axons exit the CNS?

Cranial nerves and pelvic splanchnic nerves.

What is the effect of sympathetic activation on the heart?

Increases heart rate and contractility.

What is the effect of parasympathetic activation on the heart?

Decreases heart rate.

What is the effect of sympathetic activation on the GI tract?

Decreases motility and secretion.

What is the effect of parasympathetic activation on the GI tract?

Increases motility and secretion.

What is the function of cranial nerve IX (Glossopharyngeal)?

Sensation from the pharynx and posterior tongue; taste; motor to stylopharyngeus; parasympathetic to parotid gland.

What is the function of cranial nerve X (Vagus)?

Sensory and motor to thoracic and abdominal viscera; regulation of heart, lungs, and digestive tract.

What extraocular muscle does the lateral rectus control, and what nerve innervates it?

Moves eye laterally; innervated by CN VI (abducens).

What extraocular muscle does the medial rectus control, and what nerve innervates it?

Moves eye medially; innervated by CN III (oculomotor).

What does the levator palpebrae superioris muscle do, and what innervates it?

Elevates the upper eyelid; innervated by CN III (oculomotor).

What is the function of the vestibular nuclei?

Process balance and spatial orientation from the inner ear.

Where is the oculomotor nucleus located and what does it control?

Midbrain; controls most extraocular muscles.

What is the function of the Edinger-Westphal nucleus?

Parasympathetic control of pupil constriction and lens accommodation.

What is the function of the trochlear nucleus?

Innervates superior oblique muscle (CN IV) for downward and lateral eye movement.

What does the trigeminal motor nucleus control?

Muscles of mastication.

What is the function of the abducens nucleus?

Controls lateral rectus muscle via CN VI.

What does the facial motor nucleus control?

Facial expression muscles via CN VII.

What is the pathway for visual information in the brain?

Retina → Optic nerve → Optic chiasm → Optic tract → Lateral geniculate nucleus → Visual cortex.

What is the function of upper motor neurons (UMNs) in the lateral corticospinal tract?

Initiate and modulate voluntary muscle contractions by acting on LMNs.

Where are UMNs of the lateral corticospinal tract located?

Primary motor cortex; they descend through the internal capsule and decussate at the medulla.

What is the function of lower motor neurons (LMNs)?

Directly innervate skeletal muscles to cause contraction.

Where are LMNs located?

In the anterior horn of the spinal cord and cranial nerve nuclei in the brainstem.

What does the posterior semicircular canal detect?

Angular acceleration of the head in the coronal plane (e.g., side-bending).

What does the horizontal semicircular canal detect?

Angular acceleration in the transverse plane (e.g., head turning).

What does the anterior semicircular canal detect?

Angular acceleration in the sagittal plane (e.g., nodding).

What is the function of the saccule?

Detects vertical linear acceleration.

What is the function of the utricle?

Detects horizontal linear acceleration.