Central Nervous System

What are the major parts of the adult brain?

1. Brain Stem: Midbrain, pons, and medulla oblongata

2. Cerebellum: Coordinates movement and balance

3. Diencephalon: Thalamus, hypothalamus, and epithalamus

4. Cerebrum: Two hemispheres responsible for higher cognitive functions

What are the ventricles?

• Fluid-filled cavities in the brain that contain cerebrospinal fluid (CSF)

Lateral Ventricles

• Located in the cerebral hemispheres

• horseshoe shaped

Third Ventricle

• In the diencephalon

• connected to lateral ventricles via the interventricular foramen.

Cerebral Aqueduct

• Connects the third and fourth ventricles.

Fourth Ventricle

• In the hindbrain

• connects to the central canal of the spinal cord

How is Gray Matter Organized in the CNS?

• contains neuronal cell bodies, dendrites, and short axons

• found in the cortex, cerebellum, and in nuclei

How is White Matter Organized in the CNS?

• consists of myelinated axons that connect different regions of the CNS

• found external to gray matter in the brain & internal in the spinal cord

Structures of the Brain Stem

1. Midbrain

2. Pons

3. Medulla Oblongata

Midbrain

• involved in visual & auditory reflexes

• motor control

• dopamine production

Pons

• acts asa bridge b/w midbrain & medulla

• motor control

• sensory integration

Medulla Oblongata

• controls autonomic functions

  • heart rate

  • respiration

  • reflexes

What are the Functions of the Brain Stem

• pathway for finer tracts b/w the cerebrum + spinal cord

• controls automatic survival behaviours & integral reflexes

What is the Structure of the Cerebellum?

• Cerebellar Cortex: Outer layer of gray matter.

• Arbor Vitae: Internal white matter.

• Deep Cerebellar Nuclei: Clusters of gray matter deep within the cerebellum.

What is the Role of the Cerebellum?

• coordinates voluntary movement, balance & posture

• Fine tunes motor commands

• compares intended mvmts w/ actual body position

What are the Divisions of the Diencephalon?

1. Thalamus: Relay station for sensory signals to the cerebral cortex.

2. Hypothalamus: Controls autonomic functions, emotions, and endocrine system (e.g., hunger, thirst, body temperature).

3. Epithalamus: Contains the pineal gland, which secretes melatonin and regulates circadian rhythms.

What are the Functions of the Diencephalon?

• Sensory relay

• autonomic regulation

• control of emotional & endocrine responses

What are the Major Lobes of the Cerebral Cortex?

• frontal lobe

• parietal lobe

• temporal lobe

• occipital lobe

• insular lobe

Frontal Lobe

• motor control

• planning

• reasoning

• decision making

Parietal Lobe

• sensory processing

• spatial awareness

Temporal Lobe

• auditory processing

• memory + language comprehension

Occipital Lobe

• visual processing

Insular Lobe

• emotion

• self awareness

• taste

Longitudinal Fissure

• separates the 2 cerebral hemispheres

Transverse Fissure

• separates cerebrum from the cerebellum

Central Sulcus

• separates the frontal & parietal lobes

Lateral Sulcus (Sylvian Fissure)

• separates the temporal lobe from the frontal & parietal lobe

What is the Role of the Thalamus in the Diencephalon?

• acts as a relay station for sensory signals

• directing them to the appropriate areas of the cerebral cortex

• also amplifies or tones down sensory signals.

What are the Functions of the Hypothalamus?

The hypothalamus regulates:

• Autonomic Functions: Heart rate, blood pressure, and digestion.

• Emotional Responses: Stress, fear, and aggression.

• Endocrine System: Controls hunger, thirst, body temperature, and sleep-wake cycles.

• Memory Formation: Plays a role in memory and learning.

What is the Role of the Epithalamus?

• contains the pineal gland

  • secretes melatonin

  • regulates circadian rhythms

What are the Key Features of the Cerebral Cortex?

• Gyri: Raised ridges that increase the surface area of the cortex.

• Sulci: Grooves that separate the gyri.

• Fissures: Deep grooves that divide the brain into lobes (e.g., longitudinal fissure, central sulcus).

• Brodmann Areas: 47 distinct regions with specific functions.

What Are the 3 Main Functional Areas of the Cerebral Cortex?

1. Sensory areas

   • process conscious sensory input

     • touch, vision + hearing

2. Association areas

   • control voluntary motor functions

3. Motor areas

   • integrate sensory & motor information for complex tasks links memory, language & decision-making

Where is the Primary Somatosensory Cortex Located?

• located along the postcentral gyrus in the parietal lobe

What is the Function of the Primary Somatosensory Cortex?

• processes general somatic senses

  • touch, pressure, pain

• spatial discrimination

What is the Role of the Primary Motor Cortex?

• located in precentral gyrus

• controls voluntary motor functions

• contains pyramidal cells that activate specific body areas

What is the Function of Broca’s Area?

• located in the left hemisphere

• controls speech production + language comprehension

What are the 3 Types of White Matter Tracts in the Brain?

1. Association Fibers

   • connect regions w/in the same hemisphere

2. Commissural Fibers

   • connect the 2 hemispheres

3. Projection Fibers

   • transmit info b/w the cerebral cortex & lower regions

What is the Function of the Corpus Callosum?

• a commissural fiber tract

• connects L and R cerebral hemispheres

• allowing communication b/w them

What is the Role of Projection Fibers?

• carry motor & sensory info to & form cerebral cortex, brainstem + spinal cord

What are the 3 Main Components of the Basal Nuclei?

1. Caudate Nucleus

   • involved in movement + learning

2. Putamen

   • controls voluntary

3. Globus Pallidus

   • regulates muscle tone

What is the Role of the Basal Nuclei in Motor Control?

• help select appropriate muscles for tasks

• inhibit unwanted movements

• regulate movement via the substantia nigra

What is the Function of the Basal Forebrain Nuclei?

• part of the cholinergic system

• involved in arousal, learning, memory & motor control

• degeneration is linked to Alzheimer’s disease

What are the Main Components of the Limbic System?

1. Hippocampal formation

   • Memory

2. Amygdaloid body

   • Fear + Emotional Responses

3. Cingulate gyrus

   • Emotion & Pain Interpretation

4. Fornix

   • Connects limbic structures

What is the Function of the Reticular Formation?

• regulates alertness, arousal & consciousness through the reticular activating system

• also filters repetitive stimuli & modulates pain

What is the Role of the Amygdaloid Body?

• it processes emotions, particularly fear, & triggers emotional responses

What are the 3 Layers of the Meninges?

1. Dura Mater

   • tough outer layer

2. Arachnoid Mater

   • middle layer w/ CSF in the subarachnoid space

3. Pia Mater

   • thin, innermost layer that adheres to the brain

What is the Function of the Dura Mater?

• provides a tough protective barrier & encloses dural sinuses that drain blood and CSF

What is the Role of the Arachnoid Mater?

• contains arachnoid villi

  • facilitate the passage of CSF into dural venous sinuses

Where is the CSF Produced?

• produced by the choroid plexuses in the brain ventricles

• which are composed of ependymal cells + capillaries

What is the Pathway of CSF Circulation?

• produced in the choroid plexuses

• flows through the ventricles & into the subarachnoid space via the median & lateral apertures

• absorbed into the dural venous sinuses through arachnoid granulations

What are the Functions of CSF?

• cushions the brain & spinal cord

• nourishes the CNS

• removes waste products

• maintains a stable chemical environment

What is the Blood Brain Barrier?

• a selective, semi permeable barrier

• formed by capillaries

• present toxins from entering the brain while allowing nutrients & certain substances to pass through

What are the Main Anatomical Features of the Spinal Cord?

• conus medullaris

• filum terminale

• cervical & lumbar enlargements

• cauda equina

Where does the Spinal Cord Begin + End?

• begins at foramen magnum

• extends to L1/L2 vertebra w/in vertebral canal

What is the Function of White Matter in the Spinal Cord?

• consists of myelinated + nonmyelinated axons

• facilitate communication b/w brain + spinal cord

• organized into dorsal, lateral + ventral columns

What are the Main Regions of Grey Matter in the Spinal Cord?

• gray commissure

• dorsal horns

• ventral horns

• lateral horns

How are Neurons Organized in the Gray Matter of the Spinal Cord?

• dorsal horns

  • contain interneurons that process sensory input

• ventral horns

  • house motor neuron cell bodies that control skeletal muscles

• lateral horns

  • contain autonomic motor neurons that regulate involuntary functions

    • (heart rate, digestion)

What are the Functional Divisions of Gray Matter?

1. Somatic Sensory

   • sensory input from skin + muscles

2. Visceral Sensory

   • sensory input for internal organs

3. Visceral Motor

   • autonomic motor control for internal organs

4. Somatic Motor

   • motor output to skeletal muscles

What are the Major Ascending Tracts in the Spinal Cord, and What Do They Carry?

1. Spinothalamic Tracts

   • carry pain, temperature + crude touch sensations

2. Dorsal Column Tracts

   • carry fine touch, vibration + proprioception

3. Spinocerebellar Tracts

   • carry proprioceptive info to the cerebellum

What are the Major Descending Tracts in the Spinal Cord, and What Do They Control?

1. Corticospinal Tracts

   • control voluntary movement of skeletal muscles

2. Reticulospinal Tracts

   • regulate posture + muscle tone

3. Vestibulospinal Tracts

   • maintain balance + posture

4. Tectospinal Tracts

   • coordinate head + neck movements

What is the Spinothalmic Pathway and What Does it Do?

• transmits pain, temperature + crude touch sensations

• from spinal cord to thalamus then to primary somatosensory cortex

What is the Corticospinal Pathway, and What Does it Control?

• carries voluntary motor commands from the primary motor cortex to the spinal cord

• controls skeletal muscle movement

What is Paraplegia and What Causes It?

• paralysis of the lower limbs

• caused by spinal injury b/w T1 and L2

What is Parkinson’s Disease and What Causes It?

• degenerative brain disease

• caused by damage to basal nuclei

• leads to loss of motor control

What is a Stroke and What are the 2 Main Types?

• cerebrovascular accident caused by interrupted blood flow to the brain

  1. Ischemic Stroke: blocked blood vessel

  2. Hemorrhagic Stroke: burst blood vessel

What are the Effects of Aging on the CNS?

• Atrophy

  • shrinkage of the brain

  • especially the cerebral cortex

• Decline in Neuroplasticity

  • reduced ability to adapt to new info

• Increased Risk of Neurodegenerative Diseases

  • alzheimers

• Diminished sensation, balance + movement control

How Does Aging Affect the Hippocampus?

• hippocampus is involved in memory formation

• shrinks w/age

• leads to memory decline