Ch 12: The Central Nervous System
Section 1 – The Brain: A description
(p. 430)
Physical description of the brain: - About 2 fistfuls of pinkish, gray tissue - Wrinkled like a walnut - Consistency of cold oatmeal
Size of the brain: - Mass in average adult male = 3.5lbs - Mass in average adult female = 3.2lbs
*In terms of brain mass per body mass, male & female brains are equal…
The Brain: Description
The Brain is Divided into 4 Major Regions: - Cerebrum (left & right hemispheres) - Diencephalon - Brain stem - Cerebellum
The Brain: Description
Ventricles: - Cavities inside the brain that contain cerebrospinal fluid - Lined with ependymal cells - Connected to hollow tube running up center of spinal cord
The Brain: Description
Ch 12: The Central Nervous System
Section 2 – The Brain: Cerebral Hemispheres
(p.433-441)
Cerebral Hemispheres: - also known as “cerebrum” - account for about 83% of total
brain mass
Various surface markings: 1) Gyri – elevated ridges 2) Sulci – shallow grooves 3) Fissures – deep grooves
Cerebral Hemispheres
Cerebral Cortex: - thin (2-4mm), superficial layer around the cerebrum
Functions of cerebral cortex: - conscious mind awareness - sensory perception - voluntary motor initiation - communication - memory storage - understanding
Cerebral Hemispheres
Cerebral Cortex: - each hemisphere concerned with sensory/motor function of opposite side of body.
- no functional area acts alone; conscious behavior involves entire cortex in one way or the other
Divided into 4 lobes: - Frontal Lobe, Temporal Lobe, Parietal Lobe, Occipital Lobe
Cerebral Hemispheres
Frontal Lobe:- Site of Primary Motor Cortex
(provides conscious control of precise, skilled, voluntary movement of skeletal muscles)
- Site of Premotor Cortex(controls learned or repetitious motor skills & coordinates
simultaneous/sequential actions)
*Damage to primary motor cortex = paralysis of muscles controlled by that area
**Damage to premotor cortex = loss of motor skills…muscles still functional, just cannot be controlled correctly
The Brain – Cerebral Cortex
Toes
Swallowing
Tongue
Jaw
Primary motorcortex(precentral gyrus)
MotorMotor map inprecentral gyrus
Posterior
Anterior
Frontal Lobe:
- Site of higher intellectual functions…thinking, etc.- Site of Broca’s area…present in left hemisphere only
(motor speech area; directs muscles of tongue)
The Brain – Cerebral Cortex
http://www.youtube.com/watch?v=_0aNILW6ILk&feature=related
Temporal Lobe:- Site of major memory centers- Site of Primary Auditory Cortex
(interprets info from inner ear as pitch, loudness, & location)
- Site of Auditory Association Area(language comprehension; stores memories of sounds)
The Brain – Cerebral Cortex
Temporal Lobe:- Site of Olfactory Cortex
(gives conscious awareness of different odors)
- Site of Gustatory Cortex(involved in the perception of taste)
- Site of Visceral Sensory Area(provides conscious perception of visceral sensations; for
example, upset stomach or full bladder)
The Brain – Cerebral Cortex
Parietal Lobe:- Site of the Primary Somatosensory Cortex
(receives & interprets sensory information from skin, skeletal muscles, & joints)
- Site of Somatosensory Association Cortex (determines size, texture, & relationship of parts of objects
being felt)
- Site of Vestibular Cortex(responsible for conscious awareness of balance)
The Brain – Cerebral Cortex
Genitals
Intra-abdominal
Primary somato-sensory cortex(postcentral gyrus)
SensorySensory map inpostcentral gyrus
Posterior
Anterior
Occipital Lobe:- Site of the Primary Visual Cortex
(receives visual information from the eyes)
- Site of Visual Association Area(uses past visual experiences to interpret visual stimuli…color,
form, & movement)
The Brain – Cerebral Cortex
In general… Left Hemisphere - controls language, math, & logic
Right Hemisphere - used for insight, visual-spatial skills, intuition, & artistic skills
“Left-brained” people are typically analytical/calculating
“Right-brained” people tend to be more artistic/emotional
The Brain – Cerebral Cortex
Corpus Callosum:- Nerve tracts that connect right & left hemispheres- Allows for communication between both sides
The Brain – Cerebral Cortex
http://www.youtube.com/watch?v=lfGwsAdS9Dc&feature=related
Ch 12: The Central Nervous System
Section 3 – The Brain: Diencephalon(p. 441-444)
Diencephalon:- Found in center of brain- Encased in cerebrum- 3 subdivisions
1) Thalamus2) Hypothalamus3) Epithalamus
The Brain – Diencephalon
Thalamus:- Receives all sensory info from body- Redirects info to correct location in brain
Hypothalamus: - Site of pituitary gland…master endocrine gland - Helps regulate body temp - Controls metabolism & H2O balance - Emotional response center (perception of fear, pleasure, & rage) - Helps regulate sleep & the sleep cycle
The Brain – Diencephalon
Epithalamus: - Forms cerebrospinal fluid - Location of Pineal gland
Pineal gland - Secretes melatonin…also
helps regulate sleep cycles
The Brain – Diencephalon
Ch 12: The Central Nervous System
Section 4 – The Brain: Brain Stem
(p. 445-449)
Brain Stem:- Attaches brain to spinal cord- Controls automatic behaviors necessary for survival- Consists of Midbrain, Pons, & Medulla oblongata
The Brain – Brain Stem
Midbrain: - Located between diencephalon & pons - Contains the Corpora quadrigemina
Corpora quadrigemina - Four dome-like protrusions - Visual/auditory reflex centers 1) Superior colliculi = Visual reflex center 2) Inferior colliculi = Auditory reflex center
The Brain – Brain Stem
Pons: - Provides pathway between higher brain centers & spinal cord - Controls normal rhythm of breathing
The Brain – Brain Stem
Medulla oblongata: - Attaches brain to spinal cord - Regulates heart rate & blood pressure - Works w/ pons to regulate rate & depth of breathing - Controls swallowing, hiccupping, coughing, sneezing & vomiting
The Brain – Brain Stem
Ch 12: The Central Nervous System
Section 5 – The Brain: Cerebellum(p. 450-451)
Cerebellum:- Plays a major role in coordination- Gives you fine motor control- Equilibrium, posture, & motor learning- Plays role in word association & problem solving
The Brain – Cerebellum
Ch 12: The Central Nervous System
Section 6 – The Brain: Functional Brain Systems
(p. 451-453)
Limbic System: - area surrounding diencephalon & brain stem
- allows us to react emotionally to events - includes basal ganglia, amygdala, & hippocampus
The Brain – Limbic System
Basal Ganglia: Amygdala:- Skill learning - Emotion processing
- Anger, fear, danger, etc.
Hippocampus: - Long term memories - Damage does not erase memories…prevents new ones from being formed
The Brain – Limbic System
R.A.S.: - reticular activating system - sends impulses to cerebral cortex to keep it conscious/alert - filters out repetitive/weak stimuli to prevent sensory overload - damage to this will lead to coma
The Brain – R.A.S.
Parts of the brain…review!!Brain Layers Video
Ch 12: The Central Nervous System
Section 7 – The Brain: Higher Mental Functions
(p. 453-460)
Electroencephalogram (EEG): - records electrical activity that accompanies brain function
Brain Waves: - patterns of electrical activity in the neurons - unique for each individual - used to diagnose & localize brain tumors, epilepsy, sleep
disorders, & infections - flat EEG (no waves) indicates no electrical activity & is used
to determine “clinical death”
Higher Mental Functions
Consciousness: - involves the conscious perception of sensations - have ability to initiate voluntary movements - loss of consciousness is sign that brain function is impaired - defined based on how you behave in response to stimuli
1) Fainting- brief loss of consciousness- caused by loss of blood flow to brain or low BP
2) Coma- total loss of consciousness for long periods of time- incapable of being “woken up”
Higher Mental Functions
Sleep: - state of partial unconsciousness; capable of regaining consciousness fairly easily
Importance of sleep - considered a period of time where body restores itself - dreams considered a “reverse learning process” where mind is trying to work through daily activities; daily events that have no significant purpose are deleted from memory
Higher Mental Functions
Sleep disorders: 1) Narcolepsy - body falls into deep sleep from awake state w/o warning - usually lasts about 15 min
2) Insomnia - chronic inability to obtain amount/quality of sleep needed
3) Sleep apnea - breathing temporarily stops during sleep - often occurs when throat muscles lose tone allowing trachea to
become blocked
Higher Mental Functions
Memory: - the storage & retrieval of information
Two stages 1) Short-term memory (STM)
- also called “working memory”- temporary storage of information- limited to 7 or 8 pieces of information
2) Long-term memory (LTM)- limitless capacity- STM information used over & over becomes LTM
Higher Mental Functions
Factors that Affect Transfer of STM to LTM: 1) Emotional state
- takes place best if alert, motivated, or surprised
2) Rehearsal- repetition & practice promotes transfer
3) Association- tying new information to old memories
4) Automatic memory- some memories stored subconsciously- some events are powerful enough that you don’t have to try to remember them
Higher Mental Functions
Ch 12: The Central Nervous System
Cranial Nerves
There are 12 Cranial Nerves having specialized functions:
Cranial NervesNerve name & # Function Sensory/MotorOlfactory nerve (I) Smell Sensory
Optic nerve (II) Vision Sensory
Oculomotor nerve (III) Movement of eyes; constriction of pupils Motor
Trochlear (IV) Movement of eyes down & in Motor
Trigeminal nerve (V) Face sensation; chewing Sensory & Motor
Abducens nerve (VI) Movement of eyes laterally (away from nose) Motor
Facial nerve (VII) Taste; movement of face muscles Sensory & Motor
Vestibulocochlear nerve (VIII) Balance & hearing Sensory
Glossopharyngeal nerve (IX) Taste; movement of pharynx Sensory & Motor
Vagus nerve (X) Pharynx & larynx sensation/movement Sensory & Motor
Accessory nerve (XI) Muscles of neck & upper back Motor
Hypoglossal nerve (XII) Movement of tongue Motor
Ch 12: The Central Nervous System
Section 8 – The Brain: Protection
(p. 460-464)
Brain & Spinal Cord Physically Protected in 3 Ways:1) Bony armor
- Skull protects the brain- Vertebral column protects the spinal cord- Considered the first line of defense
The CNS: Protection
Brain & Spinal Cord Physically Protected in 3 Ways:2) Meninges
- 3 layers of connective tissues…wrap brain & spinal corda) Dura mater
- Outermost layer; limits excessive brain movementb) Arachnoid mater
- Middle layer; weblike c) Pia mater
- Inner layer; very delicate; highly vascularized
WARNING!!! Some fairly graphic pictures ahead…
The CNS: Protection
Brain & Spinal Cord Physically Protected in 3 Ways:3) Blood-brain barrier
- Capillaries of brain unlike those in rest of body…resist diffusion of substances other than O2 & CO2
- Other substances that can get through…alcohol, nicotine, & anesthesia
The CNS: Protection
Cerebrospinal fluid (CSF): - fluid between meningeal layers that provides cushioning - also nourishes the brain & spinal cord
The CNS: Protection
Ch 12: The Central Nervous System
Section 9 – The Brain: Homeostatic Imbalances
(p. 451-453)
Traumatic Brain Injuries:- Leading cause of accidental death
1) Concussion- Slight brain injury…no permanent damage
2) Contusion- Bruising of brain tissue…blood destroys tissue- Permanent damage…tissue does not regenerate
3) Cerebral edema- Swelling of brain tissue- May compress brain & cause death of tissue
Homeostatic Imbalances of the Brain
Cerebrovascular Accident (CVA):- More commonly called a stroke- Result of blocked blood vessel in brain- Brain tissue that is supplied with O2 from that blood
vessel will die- Leads to loss of function or possible death
Aneurysm:- Blood vessel bursts in the brain
Homeostatic Imbalances of the Brain
Alzheimer’s Disease:- Progressive, degenerative brain disease- Mostly seen in elderly…usually begins in middle age- Causes structural changes in the brain…abnormal
protein deposits & twisted neurons- Memory loss, irritability, confusion, hallucinations,
death
Homeostatic Imbalances of the Brain
Hypersomnia: - condition where individuals sleep as much as 15hrs/day
Microcephaly: - formation of a small brain - most children with this will experience mental retardation
Hydrocephalus: - build-up of CSF due to some kind of obstruction - skull becomes noticeably enlarged due to increased fluid pressure & incomplete fusion of skull bones
Homeostatic Imbalances of the Brain
Anencephaly: - means “without brain” - when cerebrum & part of brain stem never develop - child is completely vegetative - cannot see, hear, or process sensory inputs - voluntary muscle movements are impossible - death occurs very soon after birth
Homeostatic Imbalances of the Brain
Warning!!!! Potentially VERY disturbing picture…PLEASE turn your head if
you wish!!!!!
Ch 12: The Central Nervous System
Section 10 – The Spinal Cord
(p. 466-476)
Spinal Cord:- Extends from medulla oblongata
down to T12 vertebra- Cervical enlargement = Nerves
to arms- Lumbar enlargement = Nerves
to legs- Below T12 = Cauda equina
The Spinal Cord
Spinal Cord:- Provides 2-way communication to & from brain- Contains spinal reflex centers- All sensory information enters back of spinal cord through
dorsal root- All motor signals leave the front of spinal cord through
ventral root
The Spinal Cord
Ch 12: The Central Nervous System
Section 11 – The Spinal Cord: Homeostatic
Imbalances (p. 466-476)
*The spinal cord is elastic and can stretch easily…However, it is incredibly sensitive to pressure.
Parasthesias:- damage to the cord that causes sensory loss
Paralysis:- damage to the cord that causes loss of motor function
The Spinal Cord: Trauma
Transection:- complete cut/break through the spinal cord- results in total motor/sensory loss below the cut
1) Paraplegia- loss of sensory/motor function of lower limbs- caused by a transection of cord between T1 & L1
2) Quadriplegia- loss of sensory/motor function of all four limbs- caused by a transection in the cervical region
The Spinal Cord: Trauma
Poliomyelitis: - destruction of motor neurons leaving the spinal cord - caused by the poliovirus - begins as muscle pain/weakness & muscles begin to atrophy - in time, death occurs due to either paralysis of respiratory
muscles or to cardiac arrest
The Spinal Cord: Trauma
Amyotrophic Lateral Sclerosis (ALS): - also called “Lou Gehrig’s disease” - leads to destruction of motor neurons leaving spinal cord - causes loss of ability to speak, swallow, & breathe - death is inevitable; usually within 5 years
Cerebral palsy: - voluntary muscles become poorly controlled or paralyzed - largest single cause of physical disability in children
The Spinal Cord: Trauma