Neuro Parts 1-7 Combo

What are the five main regions of the CNS?

1. Spinal cord

2. Cerebrum

3. Diencephalon

4. Brainstem

5. Cerebellum

What is the primary function of the spinal cord in the CNS?

It serves as the communication highway between the periphery and the rest of the CNS through ascending sensory tracts and descending motor tracts and also mediates reflexes

What is the primary function of the cerebrum?

It is the largest part of the brain and handles:

• cognition

• voluntary movement

• sensation

• language

• memory

• emotion

• executive function

What is the primary function of the diencephalon?

The diencephalon is a deep relay and control area that helps:

• Process information

• Regulate body homeostasis

• Influence endocrine/melatonin function

• Contribute to movement circuits

through the:

• Thalamus

• Hypothalamus

• Epithalamus

• Subthalamus

What structures make up the brainstem?

1. Midbrain

2. Pons

3. Medulla

What is the primary function of the brainstem?

• Connects the cerebrum to the spinal cord and cerebellum

• Contains many cranial nerve nuclei

• Regulates vital functions

What is the primary function of the cerebellum?

It coordinates:

• movement

• posture

• balance

• motor learning

• compares intended movement with actual movement

What does the sagittal plane divide?

Left and right

What structures are seen in a mid-sagittal view of the brain?

• Corpus callosum

• third ventricle

• aqueduct

• fourth ventricle

• brainstem

• cerebellum

What does the coronal or frontal plane divide?

Anterior and posterior

What structures are commonly seen in a coronal view of the brain?

• Both hemispheres at once

• lateral ventricles

• corpus callosum

• thalamus

• basal ganglia

• internal capsule

What does the horizontal or axial plane divide?

Superior and inferior

What is a horizontal or axial plane useful for in brain imaging?

• common on CT and MRI

• shows rostral-to-caudal relationships, ventricles, deep nuclei, and anterior and posterior horns

What is found in gray matter?

• Neuron cell bodies

• dendrites

• synapses

• glia

• blood vessels

• mostly unmyelinated axons

What is the main role of gray matter?

Processing and integration of information

What is found in white matter?

Mainly myelinated axons

What is the main role of white matter?

Fast communication between cortical, subcortical, brainstem, and spinal cord regions

Where is gray matter located in the brain?

• On the surface/cortex

  • This is the outer layer of the cerebrum

• In deep nuclei

  • These are deeper collections of neuron cell bodies, like parts of the basal ganglia, thalamus, etc

Where is white matter located in the brain?

Deeper in the brain where it forms tracts such as the corpus callosum and internal capsule

How are gray matter and white matter arranged in the spinal cord?

Gray matter is central in an H or butterfly shape and white matter is on the outside

How does the arrangement of gray and white matter in the spinal cord compare to the cerebrum?

It is reversed or flipped compared with the cerebrum

Which spinal cord levels have the most white matter?

Cervical levels

Why do cervical spinal cord levels have the most white matter?

Because they carry nearly all ascending and descending tracts

Why do cervical spinal cord levels also have more gray matter?

Because they contain neurons for upper limb innervation

Which spinal cord levels contain the lateral horn?

Thoracic levels

What is the function of the lateral horn in the thoracic spinal cord?

It contains sympathetic autonomic neurons

At what spinal cord levels are sympathetic autonomic neurons found in the lateral horn?

T1 to L2

How does gray matter in the thoracic spinal cord compare with cervical and lumbar levels?

Thoracic levels have less gray matter

How does white matter in lumbar and sacral spinal cord levels compare with cervical levels?

Lumbar and sacral levels have less white matter than cervical levels

Why do lumbar and sacral spinal cord levels have less white matter?

Because fewer ascending and descending tracts remain

Why do lumbar and sacral spinal cord levels have proportionally more gray matter?

Because they contain more lower limb motor and sensory neurons

• Gray matter = the “thinking/processing centers”

Which spinal cord enlargements have more gray matter for limb innervation?

Cervical and lumbar enlargements

What is the key idea to remember about gray matter and limb innervation in the spinal cord?

Gray matter is increased where limb innervation is needed, especially in the cervical and lumbar regions

What are the four major lobes of the cerebrum?

1. Frontal

2. Parietal

3. Temporal

4. Occipital lobes

What is the main role of the frontal lobe?

• Voluntary motor function

• Motor planning

• Executive function

• Decision-making

• Personality

• Speech production

Which language area is found in the frontal lobe?

Broca’s area

What is Broca’s area responsible for?

Speech production

What is the main role of the parietal lobe?

The main role of the parietal lobe is sensory processing, especially body sensation and spatial awareness

• Somatic sensation

• Touch

• Pressure

• Temperature

• Pain

• Proprioception

• Spatial awareness

• Sensory integration

What is the main role of the temporal lobe?

• Auditory processing

• Language comprehension

• Memory

• Emotional processing

Which language area is found in the temporal lobe?

Wernicke’s area

What is Wernicke’s area responsible for?

Language comprehension

Which temporal lobe structure is important for memory?

Hippocampus

What is the main role of the hippocampus?

Formation of new memories and learning

What is the main role of the occipital lobe?

• Primary visual processing

• Visual perception

• Color recognition

• Orientation

• Depth perception

Where is the primary motor cortex located?

Precentral gyrus of the frontal lobe, anterior to the central sulcus

What does the primary motor cortex do?

Sends voluntary motor commands DOWN through descending motor pathways

Where is the primary somatosensory cortex located?

Postcentral gyrus of the parietal lobe

• Posterior to the central sulcus

What does the primary somatosensory cortex receive?

Touch, pain, temperature, and proprioceptive input UP from the body

How are the primary motor and primary sensory cortices organized?

Somatotopically as a homunculus

What side of the body do the motor and sensory cortices mostly control or process?

The contralateral side of the body

What is the limbic system involved in?

A network of brain structures involved in:

• Emotion

• Memory

• Motivation

• Drive

• Threat response

What is the role of the amygdala (part of limbic system)?

The amygdala helps process emotion, especially:

• Fear/threat detection

• Fight-flight-freeze responses

• Aggression

• Emotional memory

What structures help link emotion with autonomic and visceral responses?

• Cingulate cortex

• Insula

• Hypothalamus

Where is the motor homunculus located?

Precentral gyrus of the frontal lobe, just anterior to the central sulcus

Where is the sensory homunculus located?

Postcentral gyrus of the parietal lobe, just posterior to the central sulcus

What part of the homunculus represents the lower limb and foot?

Medial cortex

What part of the homunculus represents the trunk, upper limb, hand, face, lips, and tongue?

More lateral cortex

Why do the hands, lips, and face have large cortical areas on the homunculus?

They require more complex and important motor or sensory control, not because they are physically larger

What lesion could cause right leg weakness from motor homunculus damage?

Left ACA stroke affecting the medial left precentral gyrus

• L damage → R leg weakness

In a left ACA stroke causing right leg weakness, what part of the homunculus is damaged?

Lower limb region of the motor homunculus

What lesion could cause right facial droop and right arm weakness?

Left MCA stroke affecting the lateral precentral gyrus

In a left MCA stroke causing right facial droop and right arm weakness, what part of the homunculus is damaged?

Face and upper limb region of the motor homunculus

What lesion could cause left hand numbness or poor hand proprioception?

Right parietal lesion affecting the lateral postcentral gyrus

In a right parietal lesion causing left hand numbness, what part of the homunculus is damaged?

Hand region of the sensory homunculus

What lesion could cause left leg sensory loss?

Right medial postcentral lesion

In a right medial postcentral lesion causing left leg sensory loss, what part of the homunculus is damaged?

Lower limb region of the sensory homunculus

What are the four cortical lesion syndromes known as the 4 A’s?

1. Aphasia

2. Apraxia

3. Agnosia

4. Astereognosis

What is aphasia?

Impaired language due to damage to language areas of the brain

What functions can aphasia affect?

• Speaking

• Understanding

• Reading

• Writing

What is Broca’s aphasia?

• Language comprehension is relatively intact, but speech is slow, effortful, and nonfluent

• Broca = Broken speech

What is Wernicke’s aphasia?

• Speech may be fluent and smooth BUT does not make sense, and language comprehension is impaired

• Wernicke = Word salad

What is “word salad” associated with?

Wernicke’s aphasia

What is apraxia?

Difficulty planning or sequencing learned movements even when strength and basic sensation may be adequate

How can apraxia affect function?

Apraxia impairs motor planning, so the person may:

• Struggle with speech

• Fine motor tasks

• Gross motor tasks

• Functional activities

Even when strength and basic sensation are intact

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Apraxia = “A-practice-ia”
Like they can’t properly “practice/perform” a learned motor skill on command

What is agnosia?

Inability to process or recognize sensory information despite intact basic sensation

• Example: they can see an object but cannot identify what it is

What can a person with agnosia have trouble identifying?

Agnosia is the inability to recognize or interpret sensory information, such as objects, people, sounds, shapes, smells, or visual input, despite the basic sense being intact

What is astereognosis?

Inability to recognize a familiar object by touch alone

What does astereognosis usually reflect?

Impaired somatosensory association or integration

What brain area is often involved in astereognosis?

Parietal cortex

Can basic touch still be intact with astereognosis?

Yes, basic touch may still be felt even though the object cannot be recognized by touch alone

What structures make up the diencephalon?

1. Thalamus

2. Hypothalamus

3. Epithalamus

4. Subthalamus

What is the thalamus?

Two egg-shaped collections of nuclei in the diencephalon

What is the main role of the thalamus?

It acts as a major relay station to the cerebral cortex for sensory and motor information

What other functions is the thalamus involved in?

• Memory

• Emotion

• Consciousness,

• Arousal

• Attention

• Sleep-wake regulation

What is the hypothalamus?

The homeostasis center of the brain

What body functions does the hypothalamus regulate?

• Body temperature

• Hunger

• Thirst

• Metabolic rate

• Fluid and chemical balance

• Autonomic function

• Pituitary hormone release

What is the epithalamus?

A diencephalon structure that includes the pineal gland

What does the epithalamus influence?

Melatonin secretion and endocrine/circadian rhythms, mainly through the pineal gland

• Epi-thalamus = evening thalamus

  because melatonin rises at night

What structure is included in the epithalamus?

Pineal gland

What is the subthalamus involved in?

Basal ganglia motor control circuits

What is the role of the subthalamic nucleus?

It helps control movement and stop unwanted movement

Which diencephalon structure is most associated with sensory and motor relay to the cortex?

Thalamus

Which diencephalon structure is most associated with homeostasis?

Hypothalamus

Which diencephalon structure is most associated with melatonin secretion?

Epithalamus

Which diencephalon structure is most associated with stopping unwanted movement?

Subthalamic nucleus

What is the main role of the basal ganglia?

To modulate movement by:

• Helping start desired movements

• Suppress unwanted movements

• Rapidly stop actions when needed

What are the three major basal ganglia motor pathways?

1. Direct pathway

2. Indirect pathway

3. Hyperdirect pathway

What is the nickname for the direct pathway?

Go pathway

• to be direct…GO! GO! GO!

What does the direct pathway do?

Facilitates desired movement

How does the direct pathway facilitate movement?

It disinhibits (removes the brake from) the thalamus, allowing the thalamus to excite/activate the motor cortex