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The Brain (& CNS). Lecture 12a BIOL241. Final Exam (Exam 4). Chapters 11 – 15* 100 points Multiple choice, T/F, matching, fill in Short answer, essays (2 )* Labeling (brain [including functions], cranial nerves, spinal cord). Outline. Overview of the human brain

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the brain cns

The Brain (& CNS)

Lecture 12a

BIOL241

final exam exam 4
Final Exam (Exam 4)
  • Chapters 11 – 15*
  • 100 points
  • Multiple choice, T/F, matching, fill in
  • Short answer, essays (2)*
  • Labeling (brain [including functions], cranial nerves, spinal cord)
outline
Outline
  • Overview of the human brain
  • Tour through the brain – structures and functions
  • Cerebral hemispheres and higher mental functions
  • Meninges
  • Ventricles and CSF
  • Brain disorders
the human brain
The Human Brain
  • Composed of wrinkled, pinkish gray tissue
  • Surface anatomy includes cerebral hemispheres, cerebellum, and brain stem
  • Ranges from 750 cc to 2100 cc
  • Contains almost 98% of the body’s neural tissue
  • Average weight, adult: 1300 – 1400 gm (~3 lb)
  • 1010 to 1011 neurons
  • Trillions of connections
  • men = larger
  • Women = better connected
regions of the adult brain
Regions of the Adult Brain
  • Telencephalon (cerebrum) – cortex, white matter, and basal nuclei
  • Diencephalon – thalamus, hypothalamus, and epithalamus
  • Mesencephalon –midbrain (brain stem)
  • Metencephalon – pons (brain stem), cerebellum
  • Myelencephalon – medulla oblongata (brain stem)
basic pattern of the central nervous system
Spinal Cord

Central cavity surrounded by a gray matter core

External to which is white matter composed of myelinated fiber tracts

Brain

Similar to spinal cord but with additional areas of gray matter

Cerebellum has gray matter in nuclei

Cerebrum has nuclei and additional gray matter in the cortex

Basic Pattern of the Central Nervous System

Figure 12.4

some terms
Some terms
  • nucleus: collection of neuron cell bodies in the CNS
  • tract: collection of axons in the CNS
  • ganglia: collection of neuron cell bodies in the PNS
  • nerve: collection of axons in the PNS
    • Cranial nerves
    • Spinal nerves
tour of the brain
Tour of the brain
  • From caudal/inferior to rostral/superior
the brain stem
TheBrain Stem
  • Processes information between spinal cord and cerebrum or cerebellum
  • Controls automatic behaviors necessary for survival
  • Associated with 10 of the 12 pairs of cranial nerves (covered later)
  • Includes:
    • mesencephalon (midbrain)
    • pons
    • medulla oblongata
    • Note: some consider the diencephalon part of the brain stem as well
brain stem
Brain Stem

Figure 12.15a

anatomy brain stem
Anatomy:Brain stem

Most cranial nerves are located in the brain stem

brain stem1
Brain Stem

Figure 12.15b

medulla oblongata
Medulla Oblongata
  • Most inferior part of brain, connects brain to spinal cord
  • Relays information
  • Pyramids – two longitudinal ridges formed by corticospinal tracts
  • Regulates autonomic functions:
    • regulates arousal, heart rate, blood pressure, pace for respiration and digestion
  • Cranial nerves IX, X, XI, XII come off or enter
medulla oblongata1
Medulla Oblongata

Figure 12.16c

medulla nuclei
Medulla Nuclei
  • Cardiovascular control center – adjusts force and rate of heart contraction
  • Respiratory centers – control rate and depth of breathing
  • Additional centers – regulate vomiting, hiccupping, swallowing, coughing, and sneezing
slide21
Pons
  • Involved in somatic and visceral motor control
  • Contain the nuclei for cranial nerves V, VI, VII, VIII
  • Contains nuclei of the reticular formation
  • Control of respiration that modifies the info from the medulla
  • Nuclei and tracts passing through to the cerebellum (motor and somatosensory info)
  • Nuclei and tracts to other portions of the CNS (just passing through)
cerebellum1
Cerebellum
  • “little brain”
  • Second largest part of brain (~10% mass)
  • Provides precise timing and appropriate patterns of skeletal muscle contraction to coordinate repetitive body movements and help learning complex motor behaviors
  • Adjusts the postural muscles of the body, controls balance and equilibrium
  • Has 2 hemispheres, covered with cerebellar cortex
  • Recognizes and predicts sequences of events
  • Cerebellar activity occurs subconsciously (as does all processing that occurs outside the cerebral cortex)
cerebellum2
Cerebellum
  • Cerebellum receives impulses of the intent to initiate voluntary muscle contraction
  • Monitors all proprioceptive info and visual info about body position
  • Cerebellar cortex calculates the best way to perform a movement
  • Programs and fine tunes movements by detecting mismatches in intended and actual movements

-- when learning to ride a bike, throw a curve ball or tie your shoe, cerebellum activity is high. When they become automatic, cerebellum is no longer involved

mesencephalon1
Mesencephalon
  • Also called midbrain
  • Processes sight, sound, and associated reflexes
  • Maintains consciousness
  • Cranial nerve nuclei III and IV
  • 2 basic divisions
    • tectum (roof)
    • tegmentum
mesencephalon2
Mesencephalon
  • Process of visual and auditory sensations
    • corpora quadrigemina(in tectum) = superior colliculi (visual reflex) and inferior colliculi (auditory reflex)
  • Substantianigra(in tegmentum)
    • Neurons inhibit activity of cerebral nuclei by releasing dopamine
    • If damaged, results in less dopamine released and muscle tone increases: muscle rigidity, difficulty initiating movement = Parkinson’s Disease
  • Reticular formation: maintain consciousness
midbrain nuclei
Midbrain Nuclei

Figure 12.16a

diencephalon
Diencephalon

Figure 12.12

diencephalon1
Diencephalon
  • Located under cerebrum and cerebellum
  • Links cerebrum with brain stem
  • Integrates sensory information and motor commands
  • Cranial nerve II
diencephalon2
Diencephalon
  • Pineal Gland
    • Secretes hormone melatonin
  • Thalamus:
    • relays and processes sensory information
  • Hypothalamus:
    • hormone production
    • emotion
    • autonomic function
diencephalon thalamus
Diencephalon: Thalamus
  • Paired, egg-shaped masses connected at the midline by the intermediate mass
  • Nuclei project to and receive fibers from the cerebral cortex

Figure 14–9

thalamus
Thalamus
  • Sensory Relay station
  • All sensory that is projected to the cerebral cortex stops here first except smell
  • Filters ascending sensory information for primary sensory cortex
  • Relays information between basal nuclei and cerebral cortex
  • Mediates sensation, some motor activities, cortical arousal (thus learning, and memory)
diencephalon hypothalamus
Diencephalon: Hypothalamus
  • Lies below

thalamus

Figure 14–10a

hypothalamus
Hypothalamus
  • Captain of the Autonomic nervous system, master overseer of homeostasis
    • Emotions and behavior: mediates perception of pleasure, fear, and rage
    • Regulation of body temperature, blood pressure, digestive tract motility, rate and depth of breathing, and many other visceral activities
    • Food intake (drives)
    • Water balance/thirst
    • Day/night rhythms
    • Endocrine functions- ADH and oxytocin
structures of the hypothalamus
Structures of the Hypothalamus
  • Mamillarybodies:
    • Relay station for olfactory information
    • control reflex eating movements
pituitary gland
Pituitary Gland
  • Major endocrine gland, controls all others
  • Connected to hypothalamus via infundibulum (stalk)
  • Interfaces nervous and endocrine systems because it is controlled by the hypothalamus
telencephalon
Telencephalon
  • Basal nuclei
  • Cerebrum
the basal nuclei ganglia
The Basal Nuclei (Ganglia)

Figure 14–14b, c

basal nuclei
Basal Nuclei
  • Also called basal ganglia
  • Masses of gray matter found deep within the cortical white matter
  • The corpus striatum is composed of three parts
    • Caudate nucleus
    • Lentiform nucleus = putamen and the globuspallidus
    • Fibers of internal capsule running between and through caudate and lentiform nuclei
  • Direct subconscious activities
functions of basal nuclei
Functions of Basal Nuclei
  • Are involved with:
    • Subconscious control of skeletal muscle tone
    • Regulate attention and cognition
    • Regulate intensity of slow or stereotyped movements (walking, lifting)
    • Inhibit antagonistic and unnecessary movement
    • Subconscious habit learning
    • May store simple movement patterns
basal nuclei1
Basal Nuclei

Figure 12.11b

cerebrum
Cerebrum
  • Largest part of brain (make up 83% of its mass)
  • Controls higher mental functions including all conscious thoughts and experience including all intellectual functions (more about this later)
  • Processes somatic sensory and motor information
  • Divided into left and right cerebral hemispheres
  • Surface layer of gray matter (cerebral cortex)
cerebral cortex
(Cerebral) Cortex
  • Gray matter covering cerebral hemispheres
  • Accounts for 40% of the mass of the brain
  • Folded surface increases surface area
  • Elevated ridges = gyri (gyrus)
  • Shallow depressions = sulci (sulcus)
  • Deep grooves = fissures
cerebral gray and white matter
Cerebral Gray and White Matter
  • Gray matter:
    • Cell bodies
    • Found in cerebral cortex and basal nuclei
  • White matter:
    • Fiber tracts (axons)
    • Deep to cerebral cortex
    • Surrounding basal nuclei
white matter of the cerebrum
White Matter of the Cerebrum
  • Myelinated fibers (axons)
    • Association fibers:
      • arcuate: local
      • longitudinal: within one hemisphere
    • Commissural: between hemispheres
    • Projection: link cerebral cortex with rest of CNS

Figure 14–13

examples
Examples
  • Projection Fibers: Internal capsule
    • all ascending and descending projection fibers to and from cerebral cortex, passes though basal nuclei
  • Commissural fibers: corpus callosum
    • Connect the two cerebral hemispheres
limbic system
Limbic System

Figure 12.18

the limbic system
The Limbic System
  • One of two networks of neurons working together and spanning wide areas of the brain – the other is the consciousness regulating reticular formation (where?)
  • A of the medial functional grouping of the medial cerebral hemispheres and diencephalon that:
    • establishes emotional states and drives
    • links conscious functions of cerebral cortex with autonomic functions of brain stem
    • Allows us to react emotionally to conscious understanding and to be aware of emotions
    • facilitates memory storage and retrieval
the limbic system1
The Limbic System

Figure 14–11a

components of the limbic system
Components of the Limbic System
  • Amygdala
    • deals with anger, danger, and fear responses, along with emotional smell memories
  • Limbic lobe of cerebral hemisphere:
    • Cingulate gyrus: plays a role in expressing emotions via gestures, and resolves mental conflict (emotion)
    • Hippocampus: convert new information into long-term memories (patient H.M.?)
components of the limbic system continued
Components of the Limbic System Continued
  • Fornix:
    • tract of white matter that connects hippocampus with hypothalamus
  • Diencepalic structures:
    • Portions of thalamus, hypothalamus
reticular formation
Reticular Formation

Sends impulses to the cerebral cortex to keep it conscious and alert

Figure 12.19

the cerebral corte x

4 Lobes:

Frontal

Parietal

Temporal

Occipital

The Cerebral Cortex

Figure 14–12b

cerebral cortex1
Cerebral cortex
  • It enables sensation, communication, memory, understanding, and voluntary movements
  • Temporal lobe: memory, hearing
  • Frontal lobe: executive function, language
  • Parietal lobe: sense of self
  • Occipital lobe: vision
cerebral cortex landmarks
Cerebral Cortex landmarks
  • Lateral sulcus
  • Longitudinal fissure
  • Central sulcus
  • Precentralgyrus (primary motor)
  • Postcentralgyrus (primary sensory)
  • Association areas are for integrating information
motor and sensory areas of the cortex
Motor and Sensory Areas of the Cortex
  • Central sulcus separates motor and sensory areas

Figure 14–15a

functional areas of the cerebral cortex
Functional Areas of the Cerebral Cortex
  • The three types of functional areas are:
    • Motor areas – control voluntary movement
    • Sensory areas – conscious awareness of sensation
    • Association areas – integrate diverse information
motor areas
Motor Areas
  • Precentralgyrus of frontal lobe:
    • directs voluntary movements
  • Primary motor cortex:
    • is the surface of precentralgyrus
sensory areas
Sensory Areas
  • Postcentralgyrus of parietal lobe:
    • receives somatic sensory information (touch, pressure, pain, vibration, taste, and temperature)
  • Primary sensory cortex:
    • surface of postcentralgyrus
association areas
Association Areas
  • Any brain region that receives input from more than one sensory modality
  • aka “integrative areas” or higher level association areas
  • Relative abundance determines intellectual capacity
  • Include:
    • Prefrontal cortex
    • Language areas
    • General (common) interpretation area
    • Visceral association area
functional principles of the cerebral hemispheres
Functional Principles of the Cerebral hemispheres
  • Each cerebral hemisphere receives sensory information from, and sends motor commands to, the opposite side of body
  • The 2 hemispheres have somewhat different functions although their structures are alike
  • Correspondence between a specific function and a specific region of cerebral cortex is not precise
  • No functional area acts alone; conscious behavior involves the entire cortex
higher level prefrontal cortex
Higher level: Prefrontal Cortex
  • Most complicated region, coordinates info from all other association areas
  • Important in intellect, planning, reasoning, mood, abstract ideas, judgement, conscience, and accuratley predicting consequences
  • Phineas Gage?
phineas gage1
Phineas Gage
  • In 1848 in Vermont, had a 3.5-foot-long, 13 lb. metal rod blown into his skull, through his brain, and out of the top of his head. Gage survived. In fact, he never even lost consciousness.
  • Friends reported a complete change in his personality after the incident. He lost all impulse control.
hemispheric lateralization
Hemispheric Lateralization
  • Functional differences between left and right hemispheres
  • In most people, left hemisphere (dominant hemisphere) controls:
    • reading, writing, and math, decision-making, logic, speech and language (usually)
  • Right cerebral hemisphere relates to:
    • recognition (faces, voice inflections), affect, visual/spatial reasoning, emotion, artistic skills
brain waves
Brain Waves
  • Alpha waves – regular and rhythmic, low-amplitude, slow, synchronous waves indicating an “idling” brain (drifting off)
  • Beta waves – rhythmic, more irregular waves occurring during the awake and mentally alert state
  • Theta waves – more irregular than alpha waves; common in children but abnormal in adults
  • Delta waves – high-amplitude waves seen in deep sleep and when reticular activating system is damped
ventricles
Ventricles
  • Lined by ependymal cells which help to form the choroid plexus
  • There are two lateral ventricles in the cerebral hemispheres
  • Third ventricle is located in the diencephalon
  • Fourth ventricle is located between the pons and the cerebellum
cranial meninges
Cranial meninges
  • Dura mater consists of an outer (endosteal layer) and an inner (meningeal layer)
    • In between the layers find the dural sinus
  • Arachnoid membrane covers the surface of the brain, have a subarachnoid space
  • Pia mater is anchored to the brain by astrocytes, wraps brain tightly like saran wrap
inter layer spaces just like in the brain
Inter-Layer Spaces – just like in the brain
  • Subdural space:
    • between arachnoid mater and dura mater
  • Subarachnoid space:
    • between arachnoid mater and pia mater
    • contains collagen/elastin fiber network that’s “spiderweb-like” (arachnoid trabeculae)
    • filled with cerebrospinal fluid (CSF)

Subdural, subarachanoid spaces are frequent sites of intracranial bleeding

cerebrospinal fluid csf
Cerebrospinal Fluid (CSF)
  • Surrounds all exposed surfaces of CNS
  • Cushions, supports, and transports
  • Interchanges with interstitial fluid of brain
  • Like plasma or interstitial fluid elsewhere except much more pure
  • Arachnoid villi protrude superiorly into dural sinus and permit CSF to be absorbed into venous blood
choroid plexuses
Clusters of capillaries lined by ependymal cells that form tissue fluid filters, which hang from the roof of each ventricle

Have ion pumps that allow them to alter ion concentrations of the CSF

Help cleanse CSF by removing wastes

Choroid Plexuses
blood supply to the brain
Blood Supply to the Brain
  • Supplies nutrients and oxygen to brain
  • Delivered by internal carotid arteries and vertebral arteries
  • Removed from dural sinuses by internal jugular veins
blood brain barrier
Blood–Brain Barrier
  • Isolates CNS neural tissue from general circulation
  • Formed by network of tight junctions between endothelial cells of CNS capillaries and by feet of astrocyte processes
  • Astrocytes control blood–brain barrier by releasing chemicals that control permeability of endothelium
blood brain barrier1
Blood–Brain Barrier
  • Lipid–soluble compounds (O2, CO2), steroids, and prostaglandins diffuse into interstitial fluid of brain and spinal cord
  • Other things have to be transported in
cerebrovascular disease
Cerebrovascular Disease
  • Disorders interfere with blood circulation to brain
  • Stroke or cerebrovascular accident (CVA):
    • shuts off blood to portion of brain
    • neurons die
  • Tissue plasminogen activator (TPA) is the only approved treatment for stroke (except aspirin)
  • Transient Ischemic Attach (TIA)
degenerative brain disorders
Degenerative Brain Disorders
  • Alzheimer’s disease – a progressive degenerative disease of the brain that results in dementia (usually frontotemporal)
  • Parkinson’s disease – degeneration of the dopamine-releasing neurons of the substantianigra
  • Huntington’s disease – a fatal hereditary disorder caused by accumulation of the protein huntingtin that leads to degeneration of the basal nuclei