Ch 12: The Central Nervous System

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


Ventricles: - Cavities inside the brain that contain cerebrospinal fluid - Lined with ependymal cells - Connected to hollow tube running up center of spinal cord



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 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


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)


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)


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)


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)


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)


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


Corpus Callosum:- Nerve tracts that connect right & left hemispheres- Allows for communication between both sides


http://www.youtube.com/watch?v=lfGwsAdS9Dc&feature=related

http://www.youtube.com/watch?v=lfGwsAdS9Dc&feature=related


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


Epithalamus: - Forms cerebrospinal fluid - Location of Pineal gland

Pineal gland - Secretes melatonin…also

helps regulate sleep cycles



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


Pons: - Provides pathway between higher brain centers & spinal cord - Controls normal rhythm of breathing


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



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


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

http://www.learner.org/discoveringpsychology/brain/brain.191.swf


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”


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


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


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


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



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


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


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


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


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


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


Warning!!!! Potentially VERY disturbing picture…PLEASE turn your head if

you wish!!!!!


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


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


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


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


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Ch 12: The Central Nervous System