CH12 - Central Nervous System

List the four regions of an Adult Brain

1. Cerebral hemispheres (Cerebrum)

2. Diencephalon

3. Brain stem

   • Midbrain

   • Pons

   • Medulla

4. Cerebellum

Gray Matter vs White matter

• Gray matter

  • Short, non-myelinated neurons and cell bodies

• White matter

  • Myelinated and non-myelinated axons

Describe the basic pattern found in CNS in regards to brain regions and organization

• CNS (Brain & Spinal cord)

  • Central cavity surrounded by gray matter, white white matter external to gray matter

• Spinal cord

  • Exhibits this basic pattern → however pattern changes with ascent to brainstem

T/F: Most neuron cell bodies are located in PNS

→ False

• Most neuron cell bodies are located in CNS

  • Nuclei: clusters of neuron cell bodies in CNS

  • Ganglia: clusters of neuron cell bodies in PNS

Structural and Function of Ventricles

• STRUCTURE

  • Fluid-filled chambers that are continuous to one another and to central canal of spinal cord

    • Filled with cerebrospinal fluid (CSF)

    • Lined by ependymal cells (neuroglial cells)

      • Line the central cavities of the brain and spinal column

      • Produce cerebrospinal fluid (CSF)

  • Paired lateral ventricles (first and second) are large, C-shaped chambers located deep in each hemisphere

    • Pair is separated by membranous septum pellucidum

  • Third ventricle is in diencephalon

  • Fourth ventricle is between brain stem and connects with central canal of spinal cord

• FUNCTION

  • Produce and secrete cerebrospinal fluid to protect and maintain your central nervous system

  • CSF is constantly bathing the brain and spinal column, clearing out toxins and waste products released by nerve cells

• EXAMPLE

  • The waste product - Amyloid A-b peptide → increases the risk of Alzheimer’s disease if too much accumulates in the brain

Structural and Function of Cerebral Hemispheres (Cerebrum)

Regions of an Adult Brain (1/4)

• STRUCTURE

  • Left and right hemisphere

    • Accounts for 83% of brain mass

  • Separated by a groove, the longitudinal fissure

  • Each of these hemispheres has an outer layer of grey matter, the cerebral cortex

    • The cerebral cortex is supported by inner layer of white natter

  • The hemispheres are linked by the corpus callosum, a very large bundles of nerve fibers

• FUNCTION

  • Form superior part of brain

List the major lobes of the Cerebral Hemispheres (Cerebrum)

1. Frontal lobe

2. Parietal lobe

3. Temporal lobe

4. Occipital lobe

5. Insular lobe

   • Buried under portion of temporal, parietal and frontal lobes

Functions of Frontal Lobe

1. Executive functions

   • Planning, organizing, problem-solving, decision-making, attention, and self-control

2. Motor control

   • Initiating and coordinating voluntary movements

3. Langauge

   • Producing and understanding speech

4. Emotional regulation

   • Controlling emotions, such as anger, fear, and sadness

5. Personality

   • Expressing personality traits and social behavior

6. Working memory

   • Holding and manipulating information in the short term

7. Creativity and innovation

   • Generating new ideas and solutions

Functions of Parietal Lobe

1. Somatosensory perception

   • Processing sensations such as touch, pain, temperature, and proprioception (body awareness)

2. Spatial orientation

   • Understanding and interpreting the position and movement of objects in space

3. Attention and focus

   • Directing attention to specific stimuli and maintaining focus

4. Movement planning

   • Initiating and coordination voluntary movements

5. Language processing

   • Contributing to the understanding and production of language

6. Number and calculation

   • Processing numerical information and performing calculations

Functions of Temporal Lobe

1. Auditory Processing

   • The primary auditory cortex, which receives and processes auditory information

2. Language

   • Understanding and producing spoken language

3. Memory

   • Hippocampus, plays a vital role in forming and storing memories

4. Emotion

   • The amygdala processes and regulates emotions, including fear, pleasure, and anger

5. Visual Processing

   • Contributes to visual processing by aiding in object recognition, face recognition, and the integration of visual information with other sensory inputs

Functions of Occipital Lobe

1. Receiving visual information

   • Receives visual information from the retina via the thalamus

2. Mapping visual input

   • It helps with spatial reasoning and visual memory

3. Color determination

   • Helps determine the color of the items you see

4. Depth perception

   • It is involved in assessing distance, size, and depth

5. Object and face recognition

   • It plays a crucial role in identifying familiar faces and objects

6. Motion detection

   • The occipital lobe is also involved in processing motion

Functions of Insular Lobe

1. Interception

   • Integrates information about the internal state of the body, including pain, temperature, and visceral sensations

2. Taste

   • It’s involved in the perception and processing of taste sensations

3. Emotional Awareness

   • Experience and recognition of emotions, including happiness, sadness, fear, disgust, and empathy

4. Social Cognition

   • The insula contributes to social decision-making, trust, and other aspects of social behavior

5. Self-Awareness

   • The insula plays a role in our sense of our own body in space and our relationship to it, and awareness of self

6. Addiction

   • Implicated in the processes of addiction, including and reward-seeking behavior

Clinical - Explain Dementia

• Refers to a decline in cognitive function, including memory, thinking, and reasoning, to the point where it interferes with a person’s ability to perform daily activities

  • Dementia is not one specific disease, but rather a group of symptoms cause by various brain diseases

• While many diseases can cause dementia, Alzheimer’s disease is the most common

• Other causes include vascular dementia, Lewly body dementia, frontotemporal dementia, and Parkinson’s disease dementia

List and describe the Surface Markings on the Cerebral Hemispheres (Cerebrum)

1. Gyri

   • Ridges

2. Sulci

   • Shallow grooves

3. Fissures

   • Deep grooves

List the major Fissures of the Cerebral Hemispheres (Cereburm)

Fissure → deep grooves

1. Longitudinal fissure

   • Separates two hemispheres

2. Transverse cerebral fissure

   • Separates cerebrum and cerebellum

List the major Sucli that divide lobes

1. Central sulcus

   • Separates pre-central gyrus of frontal lobe and post-central gyrus of parietal lobe

2. Parieto-occipital sulcus

   • Separates occipital and parietal lobes

3. Lateral sulcus

   • Outlines temporal lobes

List the three basic regions of the Cerebral Hemisphere (Cerebrum)

1. Cerebral cortex of gray matter superficially

2. White matter internally

3. Basal nuclei deep within white matter

Structural and Function of Cerebral Cortex 

BASIC REGIONS of the Cerebral Hemisphere (Cerebrum) (1/3)

• STRUCTURE

  • Thin (2-4 mm) superficial layer of gray matter

  • Composed of neuron cell bodies, dendrites, glial cells, and blood vessels

  • 40% of mass of brain

• FUNCTION

  • Site of conscious mind

    1. Awareness

    2. Sensory perception

    3. Voluntary motor initiation

    4. Communication

    5. Memory storage

    6. Understanding

List the functional areas of the cerebral cortex 

BASIC REGIONS of the Cerebral Hemisphere (Cerebrum) (1/3)

No functional area of the cortex acts alone, and conscious bheavior involves the entire cortex in one way or another

1. Motor areas

   • Control voluntary movement

2. Sensory areas

   • Conscious awareness of sensation

3. Association areas

   • Integrate diverse information

     1. Visual areas

     2. Auditory areas

Responsible for complex processing that goes on between the arrival of sensory input cortices and the generation of behavior

T/F: All neurons in the cortex are interneurons

→ True

Explain Cerebral Cortex Domains

• Specific motor and sensory functions located in discrete cortical areas

• Higher functions are spread over many areas

• Shown on Functional imaging (PET and MRI)

Explain Contralateral vs Lateralization of cortical function 

1. EACH hemisphere is concerned with contralateral (opposite) side of body

2. Lateralization (specialization) of cortical function can occur in only ONE hemisphere

3. Conscious behavior involves entire cortex

Describe the location, function, structure of Motor Areas in Cerebral Cortex

Functional areas of the cerebral cortex (1/3)

• LOCATION

  • In frontal lobe

• FUNCTION

  • Motor areas act to control voluntary movement

• STUCTURE

  1. Primary motor cortex

  2. Premotor cortex

  3. Broca’s area

  4. Frontal eye field

List the components of Motor Area

Functional areas of the cerebral cortex (1/3)

Motor areas in Cerebral Cortex

1. Primary (somatic)Motor Cortex

   • LOCATION

     • In pre central gyrus of each frontal lobe

   • FUNCTION

     • Initiating voluntary movements

     • Somatotopy → All muscles of body can be mapped to area on primary motor crotex

     • Motor homunculi → Upside-down caricatures represent contralateral motor innervation of body regions

2. Premotor cortex

   • LOCATION

     • Anterior to the pre-central gyrus of each frontal lobe

   • FUNCTION

     • Helps to plan and coordinate complex movements

3. Broca’s area

   • LOCATION

     • Anterior to inferior premotor area

     • Present in one hemisphere (usually left)

   • FUNCTION

     • Motor speech area that directs muscles of speech production

     • Active in planning speech and voluntary motor activities

Clinical - Examples to damages to area Primary Motor Cortex

• Damage to areas of primary motor cortex, as seen in a stroke, paralyzes muscles controlled by those areas

• Paralysis occurs on opposite side of body from damage

• Only voluntary control is lost, however, as the muscles can still contract reflexively

Clinical - Examples to damages to area Premotor Area

• Muscle strength or ability to PERFORM discrete individual movements is not impaired; ONLY CONTROL over movements is lost

• EX: Damage to premotor area controlling movement of fingers would still alllow fingers to move, but voluntary control needed to type would be lost

  • Other premotor neurons can be reprogrammed to rake over skill of damaged neurons

  • Would require practice, just as the initial learning process did

Describe the location, function, structure of Sensory areas in Cerebral Cortex

Functional areas of the cerebral cortex (2/3)

• LOCATION

  • Occur in parietal, insular, temporal, and occipital lones

• FUNCTION

  • Areas of cortex concerned with conscious awareness of sensation

• STUCTURE

  • Primary somatosensory cortex

Location and function of Primary somatosensory cortex

Functional areas of the cerebral cortex (2/3)

Sensory areas in Cerebral Cortex

• LOCATION

  • In postcentral gyri of parietal lobe

• FUNCTION

  • Receives sensory information from skin and proprioceptors of skeletal muscle, joints, and tendons

  • Capable of spatial discrimination → identification of body region being stimulated

  • Somatosensory homunculus → upside-down caricatures represent contralateral sensory input from body regions

Describe the location, function, structure of Assoication areas in Cerebral Cortex

Functional areas of the cerebral cortex (3/3)

Visual association areas in Cerebral Cortex

• LOCATION

  • Surronds primary visual cortex

• FUNCTION

  • Uses past-visual experiences to interpret visual stimuli (color, form, or movement)

    • EX ability to recognize faces

  • Complex processing involves entire posterior half of cerebral hemispheres

• STRUCTURE

  • Primary visual (striate)

    • Cortex located on extreme posterior tip of occipital lobe

Auditory association areas in Cerebral Cortex

• LOCATION

  • Located posterior to primary auditory cortex

• FUNCTION

  • Stores memories of sounds and permits perception of sound stimulus

• STRUCTURE

  • Primary auditory cortex

    • Superior margin of temporal lobes

    • Interprets information from inner ear as pitch, loudness, and location

Clinical - Damage to the Primary Visual Cortex

• Primary visual cortex → results in blindness

• Visual association area → can see, but they do not comprehend what they are looking at

Describe the general structure function of the Cerebral White Matter

BASIC REGIONS of the Cerebral Hemisphere (Cerebrum) (2/3)

• STURCURE

  • Second of three basic regions of cerebral hemispheres

  • Consists of myelinated fibers bundled into large tracts

• FUNCTION

  • Responsible for communication between cerebral areas and between cortex and lower CNS

  • Classified according to direction they run”

    1. Association

    2. Commissural

    3. Projection fibers

Describe the general structure function of the basal nuclei (basal ganglia) 

BASIC REGIONS of the Cerebral Hemisphere (Cerebrum) (3/3)

• STRUCTURE

  • Third of the three basic regions of cerebrum

• FUNCTION

  • Influence muscle movements

  • Play role in cognition and emotion

  • Filter out incorrect/inappropriate responses

Clinical - Disorders of the basal nuclei

1. Parkinson’s disease

   • Brain disorder that causes unintended or uncontrollable movements, such as shaking, stiffness, and difficulty with balance and coordination

2. Huntington’s disease

   • An inherited disorder that causes nerve cells (neurons) in parts of the brain to gradually break down and die

Describe the location of the diencephalon and the name its subdivisions  

• Consists of three paired gray matter structures:

  1. Thalamus

  2. Hypothalamus

  3. Epithalamus

• LOCATION

  • All three enclose third ventricle

Describe the structure and function of the Thalamus

Diencephalon Subdivision (1/3)

• STRUCTURE

  • Bilateral egg-shaped nuclei that form superolateral walls of third ventricle

  • Makes up 80% of diencephalon

• FUNCTION

  • Act as relay station for information coming into cortex

  • Sorts, edits, and relays ascending input such as:

    1. Impulses from hypothalamus for regulating emotion and visceral function

    2. Impulses for memory or sensory integration

  • Overall it acts to mediate sensation, motor activities, cortical arousal, learning, and memory

Describe the structure and function of the Hypothalamus

Diencephalon Subdivision (2/3)

• STRUCTURE

  • Located below thalamus

  • Forms cap over brain stem and forms inferolateral walls of third ventricle

  • Contains many important nuclei such as:

    1. Mammillary bodies → paired anterior nuclei that act as olfactory relay stations

    2. Infundibulum → stalk that connects to pituitary gland

• FUNCTION

  • Main visceral control and regulating center that is vital to homeostasis

  • Chief homeostasis controls:

    1. Controls autonomic nervous systems

       • EX: BP, rate and force of heartbeat, digestive tract motility, pupil size

    2. Initiates physical responses to emotions

       • Part of limbic system → perceives pleasure, fear, rage, biological rhythms, and sex drive

    3. Regulates body temp

       • Sweating or shivering

    4. Regulates hunger and satiety in response to nutrient blood levels or hormones

    5. Regulates sleep-wake cycle s

       • Suprachiasmatic nucleus of thalamus sets out biological clock

    6. Controls endocrine system function

       • Secretions of anterior pituitary gland

       • Production of posterior pituitary hormones

Describe the structure and function of the Epithalamus

Diencephalon Subdivision (3/3)

• STRUCTURE

  • Most dorsal portion of dicencephalon

  • Forms roof of third ventricle

  • Contains pineal gland (body)

    • Extends from posterior border

• FUNCTION

  • Pineal gland → secretes melatonin that helps regulate sleep-wake cycle

List the three regions of the Brain Stem

1. Midbrain

2. Pons

3. Medulla oblongata

Describe the strucutre of the Brain stem

• Similar in structure to spinal cord BUT contains nuclei embedded in white matter

• Contains fiber tracts connecting higher and lower neural centers

• Nuclei are associated with 10 of the 12 pairs of cranial nerves

Describe the structure and function of the Midbrain

Brain Stem (1/3)

• STRUCTURE

  • Midbrain nuclei scattered throughout white matter include:

    • Substantia nigra → functionally linked to basal nuclei

      • Parkinson’s disease is degeneration of this of this area

Describe the structure and function of the Medulla Oblongata

Brain Stem (2/3)

• STRUCTURE

  • Blends into spinal cord at foramen magnum

  • Contains fourth ventricle

    1. Continuation of central canal of spinal cord

    2. Medulla and pons from ventral wall

    3. Contains choroid plexus → capillary-rich membrane that forms cerebral spinal fluid

• FUNCTION

  • Medulla is an autonomic reflex center

  • Many functions overlap with hypothalamus → hypothalamus relays instructions via medulla

List the functional groups of Medulla Oblongata

1. Cardiovascular center:

   • Force and rate of heart contraction

     • Vasomotor center adjusts blood vessel diameter for BP regulation

2. Respiratory centers

   • Generate respiratory rhythm

   • Control rate of depth of breathing

3. Various other centers regulate:

   • Vomiting

   • Hiccuping

   • Swallowing

   • Coughing

   • Sneezing

Describe the structure and function of the cerebellum 

• STRUCTURE

  • 11% of brain mass

  • Located dorsal to pons and medulla

• FUNCTION

  • Processes input from cortex, brain stem, and sensory receptors to provide precise, coordinated movements of skeletal muscles

  • Plays a major role in balance

List structures that protect the brain

1. Meninges

   • Dura mater

   • Arachnoid mater

   • Pia mater

2. Cerebrospinal fluid (CSF)

3. Blood barrier

List the layers of Meninges from external to internal

1. Dura mater

2. Arachnoid mater

3. Pia mater

Describe how the cerebrospinal fluid, meninges protect the brain 

1. Dura mater

   • STRUCTURE

     • Made up of two layers of fibrous connective tissue → two layers are mostly fused, but separate in certain areas to form dural venous sinuses

   • FUNCTON

     • Strongest meninx

     • Sinuses collect venous blood from brain, empty into jugular veins of neck

     • Extends inward in several areas to form flat partitions that divide cranial cavity

       • Partitions referred to as dural septa

       • Act to limit excessive movement of brain

2. Arachnoid mater

   • STRUCTURE

     • Middle layer with spiderweb-like extensions

     • Separated from dura mater by subdural space

     • Subarachnoid space contains CSF and largest blood vessels of brain

     • Arachnoid granulation protrude through dura mater into superior sagittal sinus

   • FUNCTION

     • Arachnoid granulation → permit reabsorption pf CSF back into venous blood

3. Pia mater

   • STRUCTURE

     • Delicate connective tissue that clings tightly to brain, following every convolution

   • FUNCTION

     • Contain many tiny blood vessels that feed brain

Clinical - Meningitis & Encephalitis

• Meningitis: Inflammation of the meninges

  • May spread to CNS → which would lead to inflammation of the brain → encephalitis

• Meningitis is usually diagnosed by observing microbes in sample of CSF obtained via lumbar puncture

Explain how cerebrospinal fluid (CSF) is formed and describe its circulatory pathway 

1. The choroid plexus of each ventricle produces CSF

2. CSF flows through ventricles and into the subarachnoid space via the median and lateral apertures

   • Arachnoid mater

3. CSF flows through subarachnoid space

   • Arachnoid mater

4. CSF is absorbed into the dural venous sinuses via the arachnoid granulations

   • Dura mater

Describe how the blood-brain barrier protect the brain 

• STRUCTURE

  • Substances from blood must first pass through continuous endothelium of capillary walls before gaining entry into neurons

    1. Tight junctions ensure substances pass through, not around endothelial cells

    2. Feet of astrocytes and smooth muscle-like pericytes surround endothelial cells → Help to promote thigh junction formation in endothelial cells

• FUNCTION

  • Helps maintain stable environment for brain

    • Chemical variations could lead to uncontrollable neuron firings

List how substances move through endothelial cells

1. Simple diffusion

   • Allows lipid-soluble substances, as well as blood gases to pass freely through cell membrane

2. Specific transport mechanism

   • Facilitated diffusion moves substances important to the brain such as glucose, amino acids and specific ion

   • Transcytosis moves larger substances into and out of brain

What is the last part of Blood-Brain Barrier substances must pass through?

• Thick basement membrane surrounding capillaries is last part of barrier substances must pass through

  • Contains enzymes that destroy certain chemicals that would activate brain neurons

• Absent in some areas, such as vomiting center and hypothalamus

  • Necessary to monitor chemical composition and temperature of blood

List and describe the types of Brain Injuries

1. Concussion

   • Alteration in brain function, usually temporary, following a blow to the head

2. Contusion

   • More serious concussion can bruise brain

3. Cerebrovascular Accidents (CVAs)

   • Also referred to as “strokes”; tissue deprived of blood supply, leading to death of brain tissue (ischemia)

   • Can be caused by blockage of cerebral artery by blood clot

Describe the cause (if known) and symptoms of Concussion vs Contusions, and cerebrovascular accidents (strokes) 

1. Concussion

   • Widespread damage to the brain

   • CAUSE

     • Only caused by head trauma

   • SYMPTOMS

     • Some cause bleeding in the brain but not alll

     • Often experience cognitive and psychological effects such as memory loss and irritability

2. Contusion

   • Localized injury that damages a limited area of the brain

     • Typically more severe

   • CAUSE

     • Mostly caused by head trauma but can also be the result of having high BP as a older person, bleeding problems, taking blood thinning medicines or some illegal drugs

   • SYMPTOMS

     • Causes bleeding, clotting and pooling of blood int he brain

3. Cerebrovascular Accidents (CVAs)

   • Strokes

   • CAUSE

     • Hemiplegia (paralysis on one side) or sensory and speech deficits

   • SYMPTOMS

     • Loss of sensation

     • Seizures

     • Speech and Associated problems

Describe the structure and function Spinal cord

• STRUCTURE

  • Spinal cord is enclosed in vertebral column

    • Begins at the foramen magnum

    • Ends at L₁ or L₂ vertebra

• FUNCTION

  • Provides two-way communication to and from brain and body

  • Major reflex center → reflexes are initiated and completed at spinal cord

How is Spinal Cord protected?

1. Protected by bone, meninges, and CSF

2. Spinal dura mater is one layer thick

   • Does not attach to vertebrae

Describe the gross structure of the spinal cord

1. Epidural space

2. Conus medullaris

3. Filum terminale

4. Spinal nerves

5. Cauda equina

Structure and function of Epidural space

Gross Anatomy of the Spinal Cord

• STRUCTURE

  • CSF fills subarachnoid space between arachnoid and pia maters

  • Dural and arachnoid membranes extend to sacrum, beyond end of cord at L1 or L2

    → Site of lumbar puncture or tap

• FUNCTION

  • Cushion of fat and network of veins in space between vertebrae and spinal dura matter

Describe the gross and microscopic structure of the spinal cord