chapter 16 - pathways and higher order functions

What are the two major functional categories of nerve pathways?

Ascending afferent (sensory) pathways and Descending efferent (motor) pathways

How do tracts (nerve pathways) often get their names?

The name often indicates the tract's origin and destination

Name the three major ascending (sensory) pathways

The posterior column pathway, the spinothalamic pathway, and the spinocerebellar pathway

How many neurons are typically involved in a sensory pathway?

Three neurons: First-order, Second-order, and Third-order

Which neuron carries sensory information from the thalamus to the cerebral cortex?

The Third-order neuron

How many neurons are typically involved in a motor pathway of the Somatic Nervous System (SNS)?

Two neurons: an Upper motor neuron and a Lower motor neuron

Which of the motor pathways includes the corticobulbar and corticospinal tracts?

The Corticospinal pathway

What two types of neurons make up the motor pathways of the Autonomic Nervous System (ANS)

A preganglionic neuron and a ganglionic neuron

Where are higher-order functions, such as consciousness and complex processing, primarily performed?

By the cerebral cortex

What characteristic of higher-order functions means they are subject to modification over time?

Learning

Which integrative region receives information from all sensory association areas and is usually present only in the left hemisphere?

The General interpretive area

What cortical area coordinates complex information and performs abstract intellectual functions?

The Prefrontal cortex

What is the conversion of a short-term memory into a long-term memory called?

Memory consolidation

What two structures of the limbic system are essential to memory consolidation?

The amygdaloid body and the hippocampus

Name one common anatomical change that occurs in the nervous system due to aging.

A reduction in brain size and weight, a reduction in the number of neurons, or a decrease in blood flow to the brain.

what does B and M stand for?

B stands for mixed and M stands for mixed

Fasciculus Gracilis & Cuneatus

These tracts are components of the Posterior Column Pathway, which is a primary ascending (sensory) pathway. They relay sensory information from the spinal cord to the brain

Corticospinal Tracts

These are components of the Corticospinal Pathway (a descending motor pathway). These tracts take a while to grow

State of Consciousness

High-level awareness and complex processing performed by the cerebral cortex. Functions in the diencephalon are almost exclusively subconscious

CSF Location

Cerebrospinal Fluid (CSF) is found in the Central Canal of the spinal cord, the ventricles of the brain (Lateral, Third, Fourth), and the surrounding subarachnoid space

Homunculus

A map representing the primary sensory and motor areas of the cerebral cortex. Certain parts of the body appear larger on this map due to a greater density of sensory or motor neuron innervation

Sensory Cortex Location

Sensory information (somatosensory) arrives at the post-central gyrus (Primary Somatosensory Cortex)

Motor Cortex Location

Motor commands for voluntary movement originate in the pre-central gyrus (Primary Motor Cortex)

General Thalamic Issues

Problems with the Thalamus affect its ability to act as a relay and integration center for nearly all sensory and motor information before it reaches the cerebral cortex

First-Order Neuron

The sensory neuron that relays information from the receptor to the Central Nervous System (CNS)

Second-Order Neuron

An interneuron located in either the spinal cord or the brain stem; it relays information from the First-Order neuron

Third-Order Neuron

Carries information from the thalamus to the primary sensory cortex of the cerebrum

Posterior Column Pathway

A major sensory (ascending) pathway. It involves the Fasciculus Gracilis and Fasciculus Cuneatus tracts (visualized as columns) that carry fine touch and proprioception to the brain

Spinothalamic Pathway

A major sensory (ascending) pathway that relays sensations such as pain and temperature toward the thalamus

Spinocerebellar Pathway

A major sensory (ascending) pathway that relays proprioceptive information to the cerebellum

Motor Pathway (General)

Motor pathways are descending tracts that carry commands from the brain to the spinal cord and typically contain two neurons

Upper Motor Neuron (UMN)

The motor neuron found within the Central Nervous System (CNS)

Lower Motor Neuron (LMN)

The motor neuron that extends from the CNS to the specific effector (e.g., skeletal muscle)

Corticospinal Pathway

A primary descending motor pathway that consciously controls skeletal muscle movements. The tracts of this pathway take a while to grow.

Spinal Cord End (Lowest CNS Part)

The spinal cord terminates inferiorly at the conus medullaris at vertebral levels L1 or L2

Dorsal Root

Contains purely sensory (afferent) axons

Dorsal Root Ganglion

Contains the cell bodies of sensory neurons, making it purely sensory

Ventral Root

Contains purely motor (efferent) axons

Spinal Nerves

Formed when the dorsal (sensory) and ventral (motor) roots meet at the intervertebral foramen. All 31 pairs of spinal nerves are therefore mixed (B)

Cholinergic

Neurons that use acetylcholine (ACh) as their neurotransmitter. All parasympathetic neurons are cholinergic

Adrenergic

Refers to neurons that use norepinephrine/epinephrine (catecholamines) as their neurotransmitter, primarily associated with the Sympathetic Division of the ANS

Decussation (Crossing Over)

The crossing over of motor tracts occurs at the level of the medullary pyramid (derived from notes). The Medulla Oblongata physically connects the brain with the spinal cord

Corticobulbar Tracts

These tracts are part of the Corticospinal Pathway. They are descending motor pathways that provide conscious motor control of skeletal muscles

Medial Pathway

A group of descending motor pathways. It includes the Vestibulospinal, Tectospinal, and Reticulospinal tracts

Lateral Pathway (Rubrospinal)

A group of descending motor pathways. It includes the Rubrospinal Tracts, which regulate subconscious muscle tone and movement, specifically of the upper limbs

Normal Consciousness

A state of high-level awareness and complex information processing. These functions are performed by the cerebral cortex

Somnolence

A state included within the spectrum of States of Awareness (Derived from notes: Description of being drowsy or excessively sleepy

Confusion

A state included within the spectrum of States of Awareness (Derived from notes: Description of reduced clarity and impaired thought)

Delirium

A state included within the spectrum of States of Awareness (Derived from notes: Description of acute destructive mental impairment)

Dementia

A state included within the spectrum of States of Awareness (Derived from notes: Description of chronic mental impairment)

Unconscious States

Includes states such as Asleep, Stupor, and Coma, which are classifications of States of Awareness

Chronic Vegetative State

A severe, long-term state included within the classifications of States of Awareness

Aging Brain

As we get older, common anatomical changes occur, including a reduction in brain size and weight and a reduction in the number of neurons