Central Nervous System NTG
Central nervous system
• Contains the _________________ and ______________ ___________
• Control center of the body
• Receives, processes and interprets the messages then determines what
output occurs
The Brain
• Contains about 12 billion _______________ and weighs about 3 pounds
• Wrinkled like a walnut and has a consistency of oatmeal
• Four regions of the brain
– Cerebrum (cerebral hemispheres)
• __________________________ brain structure
– Diencephalon
• ___________________ to the brain stem in the center of the brain
– Brain Stem
• Connects brain to spinal cord
– Cerebellum
• ________________________ to the brain stem
Cerebrum (Cerebral Hemispheres)
• Superior and most superficial part of the brain
• Composed of two hemispheres - ____________________ and ________________________
• Largest mass of the brain (83%) and most complex
• Responsible for ________________________________ or conscious activities
• Divided into regions called ____________________________
• Four lobes named for the skull bones that cover them
– Frontal lobe
• Higher intellectual _____________________, complex memories, and language comprehension
• Primary motor cortex receives information and uses the information to carry out body
_________________________
– Parietal lobe
• Primary somatic sensory cortex processes tactile sensory information such as pressure, touch and pain
– Temporal lobe
• Primary auditory cortex interprets _________________________
– Occipital lobe
• Primary __________________________ cortex receives visual stimuli and information
• Cerebral cortex
– Superficial _________________ matter on the exterior of the cerebrum composed of nerve cell bodies and dendrites
– Allows us to be aware of surroundings, communicate, remember, understand and initiate voluntary movements
• Alzheimer’s disease
– Dementia producing lesions in the cerebral _________________________________
Structural Features of the Cerebral Cortex
•
____________ (__________________)
– Elevated ridges of tissues
•
__________________________ (_________________)
– Shallow grooves
•
___________________________________
– Deeper grooves
– Usually separate large parts of the brain
Some gyri, sulci and fissures are used for anatomical landmarks
– ________________________ fissure
• Separates the cerebral hemispheres in the
middle
– ________________________ fissure
• Separates the cerebrum from the cerebellum in
posterior part of the brain
– ________________________ sulcus
• Separates the frontal lobe and the parietal lobe
– ____________________-_______________ sulcus
• Separates the occipital lobe from the parietal
lobe
– _________________ sulcus (outlines the temporal lobe)
• Separates the temporal lobe from the parietal
lobe and the frontal lobe
– __________________________ gyrus
• Elevation just anterior to central sulcus
– _________________________ gyrus
• Elevation just posterior to central sulcus
Three functional areas of the cerebrum
 _______________________________ areas
 Receive and interpret impulses from sensory receptors
 _______________________________ areas
 Initiates impulses to skeletal muscles and glands
 _______________________________ areas
 Perform complex integrative functions, receive and send information to multiple areas of the cortex
 Majority of cortex is composed of association areas
Motor Areas of the Cerebrum
• Control voluntary ________________________________
• Located in the posterior part of the _______________________ lobes
1. __________________________motor area
2. __________________________area
3. __________________________area
Primary motor area
– Located in the __________________________ gyrus of each _____________________lobe
– Allow us to consciously move our skeletal muscles
– Body is represented in an upside down manner
– The right hemisphere receives input from the left side of the body
– Areas with greater need for _________________ control are larger like the face, mouth and hands
– Damage paralyzes the voluntarily, controlled muscles of those areas (left affects right side of body)
Premotor cortex
– Located anterior to the _________________ gyrus in the frontal lobe
– Controls learned motor skills of a patterned nature (playing a musical instrument)
– Coordinates the movement of several muscle groups
– Involved in _________________ movements
Broca’s speech area
– Located at the base of the precentral gyrus on the ________________ hemisphere only
– Special motor speech area that directs the muscles involved in speech planning and production
– Damage to this area causes inability to say words properly - ________________
– You know what you want to say, but you can’t vocalize the words
Sensory Areas of the Cerebrum
• Concerned with conscious awareness of _____________________________
• Occur in the parietal, temporal and occipital lobes
1. Primary (_________________________) sensory cortex
2. Visual cortex
3. Auditory cortex
4. Olfactory cortex
5. Gustatory (_______________________) cortex
Primary (somatic) sensory cortex
– Located in the _____________________gyrus of each parietal lobe posterior to the primary motor cortex
– Receives information from the cutaneous receptors in the ____________and proprioceptors in skeletal ___________
– Allows you to recognize pain, coldness or a light touch
– Determines the body region being stimulated
_____________________________________________ Man
– Body is represented in an upside-down manner
– Body regions with the most sensory receptors, the lips and fingertips, make up a large part of the sensory cortex
– The pathways are crossed which means the right hemisphere receives input from the left side of the body
Special sense organs are interpreted in other areas of the cerebrum
Primary olfactory (_______________________) cortex
– Located deep on the medial side of each _____________________________ lobe
– Receives impulses from ___________________________ receptors in the nose
Primary visual cortex
– Located in the posterior, _____________________________ lobe
– Receives impulses from _________________________________ of the eye
Primary gustatory (______________________) cortex
– Located in each _____________________________ gyrus just superior to the lateral sulcus
– Receives impulses from the taste receptors
Primary auditory cortex
– Located in each __________________________lobe bordering the lateral sulcus and across from the gustatory area
– Receives impulses from auditory receptors
Association Areas of the Cerebrum
• Analyze sensory inputs from multiple senses
• Sends outputs to multiple motor areas
• Where sensations, thoughts, and emotions become conscious
• Information flows from: ___________________ receptors  primary ______________________________ cortex 
sensory ___________________________ cortex  ____________________________ cortex
Somatosensory, visual and auditory association
areas
– Larger areas next to the corresponding
sensory cortex
– Integrate sensory information from
sensory cortex with past experiences
– This allows us to identify objects by
touch or to identify sounds as music or
speech
Wernicke’s area
– Only in left ___________ lobe
– Recognizes spoken words, translates
words into thoughts and helps us sound
out strange or new words
– Comprehension of written and spoken
language
Lateralization of Cerebrum
• Both cerebral hemispheres appear identical but each hemisphere has unique abilities not shared by its partner – ___________
• Each half of the cerebrum deals mainly with the opposite side of the body
• One hemisphere tends to be more dominant for language, speech, logic and analytical skills – cerebral dominance
• The other hemisphere is more free-spirited, involved in visual-spatial skills, emotion and creativity
• 90% of people are _________________ hemisphere dominant and are usually right-handed
• 10% of people are _________________ hemisphere dominant and are usually left-handed
• Some “lefties” have a cerebral cortex that functions bilaterally and are called _______________________________
• The two hemispheres have perfect and almost instantaneous communication with one another via connecting fiber tracts
called the ____________________________ _____________________________
Diencephalon, Brain Stem and Cerebellum NTG
Diencephalon
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Located in the brain’s central area and surrounded by the cerebrum
Structures of the diencephalon
– Thalamus
– Epithalamus (pineal body)
– Hypothalamus
– Pituitary gland
Thalamus “inner room”
• Located on the top of the brain stem in the center of the cerebral hemispheres
• Functions
– “Grand central relay station”
– _________________ station for sensory impulses passing upward to the sensory cortex
– Filters out unnecessary sensory information
– Involved in consciousness, emotions, learning and memory
Hypothalamus
• Located below the thalamus and caps the brain stem
• Important nuclei (cell bodies) that control many involuntary functions and regulates homeostasis
1. Autonomic control center
• Regulates _________________ and _________________ muscle and secretion of glands
• Influences blood pressure, rate and force of heart beat, digestive tract motility, eye pupil size, etc
2. Center for emotional response
• Involved in perception of pleasure, fear, rage and biological rhythms and drives
• Initiates the physical expressions of ___________________________
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4.
5.
6.
7.
Controls body temperature
• Body’s _______________________________ is the hypothalamus
• Monitor blood temperature and receive input from __________________________________
• Initiates cooling (sweating) and heating (shivering) as needed
Regulates food intake
• Responds to changing blood levels of certain nutrients by regulating feelings of hunger
Regulates water balance and thirst
• ________________________________ regulate the concentration of water and stimulates thirst center
Regulates sleep-wake cycles
• Sets the timing of the sleep cycle in response to daylight-darkness cues received from visual pathways
Controls the pituitary gland
• Acts as the helmsman of the endocrine system by releasing and inhibiting hormones of the pituitary gland
Pituitary Gland
• Hangs from the anterior floor of the hypothalamus by a slender stalk
• Part of the endocrine system but located in the brain
• Controlled by the _________________
Epithalamus
• Superior and posterior to the ________________________
• Contains the pineal gland (secretes ______________________) and choroid plexus (makes the
_________________________ fluid (CSF))
Brain Stem
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About the size of a thumb in diameter and three inches long
Located between the cerebrum and the spinal cord
Three structures
1. Midbrain
2. Pons means “bridge”
3. Medulla oblongata
• Functions
– Provides a pathway for fiber tracts running between higher and lower neural centers
– Produces the programmed, automatic behaviors necessary for survival
– Associated with 10 of the 12 cranial nerves – provides main motor outputs and sensory inputs of the face and neck
Midbrain
• Small area located superior to the pons and inferior to the diencephalon
• ___________________________ reflexes that coordinate head and eye movement
• ___________________________ relay from the hearing receptors to the auditory cortex
• ___________________________ reflex which causes you to turn you head toward an unexpected sound
Pons “bridge”
• Pons “bridge”
• Located superior to the medulla oblongata and just below the midbrain
• Bulging brain stem region
• Mainly composed of fiber tracts connecting the brain to the spinal cord
• Controls normal rhythm of _______________________________
Medulla Oblongata
• Most inferior part of the brain stem
• Merges into the spinal cord without any obvious change in structure
• Automatic _________________________ control centers for heart rate, blood pressure, breathing, swallowing, and vomiting
Cerebellum
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Second largest part of the brain
Located _____________________ to the cerebrum and posterior to the medulla
Provides precise timing for skeletal muscle activity
Regulates equilibrium and balance
Produces smooth and coordinated skilled skeletal muscle movements
Like an “automatic pilot” comparing intentions with actual performance
Protection of the Central Nervous System
• Brain and spinal cord are in three layers of connective tissue called the ____________________
• Three layers
– Dura mater – double-layered external covering
– Arachnoid - middle layer
– Pia mater – internal layer; clings to the surface of the brain
• ____________________ – bacterial/viral inflammation of meninges, causes headache, fever, sore throat, back and neck pain
Homeostatic Imbalances of the Brain
• Cerebrovascular Accidents (CVA) – Stroke
– Caused by hemorrhage from cessation of blood flow through cerebral blood vessels
– Blood circulation to a brain area is blocked (blood clot, hemorrhage) and vital brain tissue dies
– Can cause injury to upper motor neurons
• Dementia – “forgetfulness”
– Loss of brain function that occurs with certain diseases
– General term of destruction of neurons of brain
– Degenerative - nonreversible
– Affects memory, language, attention span, intellect, personality, cognitive skills
– Most common type is Alzheimer’s
– Parkinson’s disease, multiple sclerosis, or Huntington’s disease are a few other diseases that can lead to dementia
• Amyotrophic lateral sclerosis (ALS) “Lou Gehrig’s Disease”
– Disease of the motor neurons in the CNS that control voluntary movements
– Motor neurons degenerate or die and can no longer send messages to muscles
– Condition gets worse and usually ends in paralysis and death in about 3-5 years
– Cause is unknown (about 10% are genetic)
– Amyotrophic
• Muscle without nourishment
– Sclerosis
– Hardening of tissue
Spinal Cord
• Enclosed within the vertebral column
• Extends from the foramen magnum (skull) to the first or second vertebra
• About 42 cm (17 inches) long and 1.8 cm (3/4 inch) thick
• Provides a two way conduction pathway to and from the brain (white matter)
• It is a major reflex center (gray matter)
• Protected by bone, cerebrospinal fluid and meninges
• 31 pairs of spinal nerves attach to the cord by paired roots
• Each nerve exits from the vertebral column on the top of the vertebra and travels to the body region it serves
• The cord does not extend the entire length of the vertebral column
• The collection of nerve roots at the inferior end is named the cauda equina because it resembles a horse’s tail
Cross Section of Spinal Cord
• The gray matter is located in its core and the white matter surrounds it
• Gray matter
• Looks like a butterfly or the letter H
• All neurons are multi-polar
• Neurons with specific functions can be found in the gray matter
• Two posterior or dorsal projections of gray matter called dorsal horns
• Contain interneurons and cell bodies
• Sensory neurons carry impulses from the sensory receptors to the dorsal roots and into the dorsal horn
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Cell bodies of the associated sensory
neurons are found in an enlarged region
called the dorsal root ganglion
Two anterior or ventral projections of gray
matter called ventral horns
Contain some interneurons but mainly
house somatic motor neurons
Motor neurons send impulses from the
ventral horn out the ventral roots to the
spinal nerve
The dorsal and ventral roots fuse to
become the spinal nerves
White matter
• Composed of myelinated and
unlyelinated nerve fibers
• Allow communication between different parts of the spinal cord and between the cord and the brain
• Run in three directions
• Ascending – up to higher centers (sensory inputs)
• Descending – down to the cord from the brain (motor outputs)
• Transversely – across from one side of the cord to the other
Bundles of axons with the same direction are called tracts
Organization of the Gray Matter
• Gray matter of the spinal cord is divided into sensory half dorsally and motor half ventrally
Homeostatic Imbalances
• Spinal cord trauma
– Any localized damage to the spinal cord or its roots leads to some functional loss
• Paralysis – loss of motor function
• Paresthesias – loss of sensory function
• Transection of the spinal cord at any level results in total motor and sensory loss in body regions below the site of damage
– Paraplegia - if the transection occurs between T1 and L1 both lower limbs are affected
– Quadriplegia – if the transection occurs in the cervical region all four limbs are affected
• Poliomyelitis (polio)
– Inflammation of the spinal cord
– Results from destruction of ventral horn motor neurons by the poliovirus
– Symptoms include fever, headache, muscle pain and weakness
– Later paralysis develops and muscles atrophy
– Victim may die from paralysis of the respiratory muscles or from cardiac arrest
– Most cases, the virus enters the body in feces contaminated water
– Vaccines have nearly eliminated this disease and a global effort is ongoing to eradicate it completely from the world