Transcript Ch 31: Urinary System

Ch 12: The Central Nervous System
Section 1 – The Brain: A description
(p. 430)
The Brain: Description
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
Ch 12: The Central Nervous System
Section 2 – The Brain: Cerebral Hemispheres
(p.433-441)
Cerebral Hemispheres
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
The Brain – Cerebral Cortex
Posterior
Frontal Lobe:
Motor
Motor map in
precentral gyrus
- Site of Primary Motor Cortex
Anterior
(provides conscious control of precise, skilled, voluntary
movement of skeletal muscles)
- Site of Premotor Cortex
(controls learned or repetitious motor skills
& coordinates
Toes
simultaneous/sequential actions)
*Damage to primary motor cortex = paralysis of muscles
Jaw
controlled by that area
**Damage to Tongue
premotor cortexPrimary
= lossmotor
of motor skills…muscles
cortex
Swallowing
(precentral gyrus)
still functional, just cannot
be controlled correctly
The Brain – Cerebral Cortex
Frontal Lobe:
http://www.youtube.com/watch?v=_0aNILW6ILk&feature=related
- 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
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
Posterior
Parietal Lobe:
Sensory
Sensory map in
- Site of the Primary Somatosensory
Cortex
postcentral
gyrus
Anterior
(receives & interprets sensory information from skin, skeletal
muscles, & joints)
- Site of Somatosensory Association Cortex
(determines size, texture, & relationship of parts of objects
being felt)
Genitals
- Site of Vestibular Cortex
(responsible for conscious awareness of balance)
Primary somatosensory cortex
(postcentral gyrus)
Intraabdominal
The Brain – Cerebral Cortex
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
http://www.youtube.com/watch?v=lfGwsAdS9Dc&feature=related
Ch 12: The Central Nervous System
Section 3 – The Brain: Diencephalon
(p. 441-444)
The Brain – Diencephalon
Diencephalon:
- Found in center of brain
- Encased in cerebrum
- 3 subdivisions
1) Thalamus
2) Hypothalamus
3) 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
Ch 12: The Central Nervous System
Section 4 – The Brain: Brain Stem
(p. 445-449)
The Brain – Brain Stem
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, hiccuping, coughing, sneezing &
vomiting
Ch 12: The Central Nervous System
Section 5 – The Brain: Cerebellum
(p. 450-451)
The Brain – Cerebellum
Cerebellum:
- Plays a major role in coordination
- Gives you fine motor control
- Equilibrium, posture, & motor learning
- Plays role in word association & problem solving
Ch 12: The Central Nervous System
Section 6 – The Brain: Functional Brain
Systems (p. 451-453)
The Brain – Limbic System
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 – R.A.S.
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
Parts of the brain…review!!
Brain Layers Video
Ch 12: The Central Nervous System
Section 7 – The Brain: Higher Mental
Functions (p. 453-460)
Higher Mental Functions
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
Ch 12: The Central Nervous System
Cranial Nerves
Cranial Nerves
There are 12 Cranial Nerves having specialized functions:
Nerve name & #
Function
Sensory/Motor
Olfactory 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)
The CNS: Protection
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 cord
a) Dura mater
- Outermost layer; limits excessive brain movement
b) 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
Ch 12: The Central Nervous System
Section 9 – The Brain: Homeostatic
Imbalances (p. 451-453)
Homeostatic Imbalances of the Brain
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:
Warning!!!! Potentially
VERY disturbing
picture…PLEASE turn your
head if you wish!!!!!
- 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
Ch 12: The Central Nervous System
Section 10 – The Spinal Cord
(p. 466-476)
The Spinal Cord
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
Ch 12: The Central Nervous System
Section 11 – The Spinal Cord: Homeostatic
Imbalances (p. 466-476)
The Spinal Cord: Trauma
*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