Chapter 14 - Brain & Cranial Nerves Flashcards
What are the 4 major parts of the brain?
- Brain stem
- Cerebellum
- Diencephalon
- Cerebrum
What does the brain stem consist of?
Medulla Oblongata
Pons
Midbrain
- continuous with the spinal cord
What does the diencephalon consist of?
Thalamus
Hypothalamus
Epithalamus
- superior to the brain stem
What does the cerebellum do?
Coordinates and regulates muscular activity
- located at the back of the skull
What does the cerebrum do?
Integration of complex sensory and neural functions
Initiation and coordination of voluntary activities
- the principal and most anterior part of the brain
What are the cranial meninges?
Protective layer of the brain
- consists of three layer
(Dura mater, arachnoid mater & pia mater)
- continuous with spinal meninges
What are the names of the three craninal meninges?
outer layer to inner layer
- Dura Mater
- Arachnoid Mater
- Pia Mater
What two things protect the brain?
- Cranial bones
2. Cranial meninges
How is the cranial dura mater different from the spinal cord dura mater?
Cranial has two layers instead of one
What are the two layers of the cranial dura mater called?
- Periosteal layer (external)
2. Meningeal layer (internal)
What separates the two hemispheres of the cerebrum?
Falx cerebri
What separates the two hemispheres of the cerebellum?
Falx cerebelli
What separates the cerebrum from the cerebellum?
Tentorium cerebelli
What does the blood-brain barrier consist of?
Mainly of tight junctions that seal together the endothelial cells of brain blood capillaries and a thick basement membrane that surrounds the capillaries
What substances can and cannot cross the BBB?
Yes - glucose - active transport
Yes - oxygen, carbon dioxide, alcohol - cross easily
Yes - urea, most ions - diffuse very slowly
No - proteins, antibiotics
What is cerebrospinal fluid? (CSF)
Clear, colourless liquid composed primarily of water
- protects the brain and spinal cord from chemical and physical injuries
Where is cerebrospinal fluid in the body?
Circulates continuously in cavities in the brain & spinal cord and in the sub-arachnoid space
What does the cerebrospinal fluid contain?
Small amounts of glucose, proteins, lactic acid, urea, cations (K+, Na+, Ca+2, Mg+2) and anion (Cl- and HCO3-)
- some white blood cells
What is the sub-arachnoid space?
Space between arachnoid and pia mater
What is the name for cavities in the brain that are filled with cerebrospinal fluid?
Ventricles
How many ventricles are in the brain?
Four
- Lateral ventricle - right hemisphere of cerebrum
- Lateral ventricle - left hemisphere of cerebrum
- Third ventricle - between the right and left halves of the thalamus
- Fourth ventricle - between brain stem and the cerebellum
What are the functions of cerebrospinal fluid?
- Mechanical protection - shock absorption
- Homeostatic function - pH of CSF affects pulmonary ventilation and cerebral blood flow
- Circulation - medium for minor exchange of nutrients & waste products
What is the choroid plexuses?
What does it do?
Networks of blood capillaries in the walls of the ventricles
- production of cerebrospinal fluid
What does the blood-cerebrospinal fluid barrier do?
Permits certain substances to enter the CSF but excludes others
- protects the brain & spinal cord from harmful substances
How is the blood-cerebrospinal fluid barrier formed?
Tight junctions of ependymal cells
How is the blood-brain barrier formed?
Tight junctions of brain capillary endothelial cells
Describe how the cerebrospinal fluid flows in the body.
- See summary on page 535
Produced in the choroid plexuses of each lateral ventricle - flows into third ventricle (through two narrow openings, called interventricular foramina)
- more CSF is added by the choroid plexsus of the third ventricle
- flows through aqueduct of the midbrain, into the fourth ventricle
- choroid plexsus of fourth ventricle adds more fluid
- enters subarachnoid space through three opening in the roof of the fourth ventricle
- then circulates the central canal of the spinal cord
What is the name of the opening(s) between the lateral (1st and 2nd) ventricles and the third ventricle?
Interventricular foramina
What is the name of the opening between the third and fourth ventricle?
Aqueduct of the midbrain (cerebral aqueduct)
What is the name of the opening(s) between the fourth ventricle and the sub-arachnoid space?
Three openings:
- single median aperture
- paired lateral apertures
Where is cerebrospinal fluid reabsorbed into the blood?
Arachnoid villi
- fingerlike projections of the arachnoid that project into the dural venous sinuses
- absorbed as fast as it is produced
The brain stem consists of what three parts?
- Medulla oblongata
- Pons
- Midbrain
Where is the brain stem located?
Between the spinal cord and the diencephalon
What is the medulla oblongata continuous with?
The superior part of the spinal cord
It forms the inferior part of the brain stem
What does the medulla oblongata’s white matter contain?
All sensory (ascending) tracts and motor (descending) tracts that extend between the spinal cord and other parts of the brain
What are pyramids?
White matter that has formed bulges on the anterior aspect of the medulla
What are pyramids formed by?
Formed by the large corticospinal tracts that pass from the cerebrum to the spinal cord
- control voluntary movements of the limbs and trunk
What is the decussation of pyramids?
Where 90% of the axons cross over from the left/right and right/left sides
- why each side of the brain controls voluntary movements on the opposite side of the body
Where is the decussation of the pyramids located?
Just superior to the junction of the medulla oblongata with the spinal cord
What is the cardiovascular center?
Regulates the rate and force of the heartbeat and the diameter of the blood vessels
- in the medulla
What is the function of the respiratory medullary rhythmicity area of the respiratory center?
Adjusts the basic rhythm of breathing
- in the medulla
Where is the pons located?
Directly superior to the medulla and anterior to the cerebellum
What does the pons consist of?
Consists of both nuclei and tracts
- is a bridge that connects parts of the brain with one another
- connect left and right sides of the cerebellum
What are the two major structural components of the the pons?
- Ventral region - forms a large synaptic relay station consisting of scattered gray centers
- Dorsal region - consists of ascending and descending tracts along with nuclei of cranial nerves
What do the pneumotaxi and apneustic areas do?
Help control breathing
Where is the midbrain? (mesencephalon)
Extends from the pons to the diencephalon
- about 2.5 cm long
What is the function of the midbrain?
Portion of the CNS associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation.
What is the function of the pons?
Primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.
What is the function of the brain stem?
Regulation of heart rate, breathing, sleeping, and eating
What is the function of the medulla oblongata?
Responsible for the regulation of your heart rate, breathing, and blood pressure as well as reflexes such as vomiting, sneezing, and coughing.
What is the reticular formation?
Broad region where white matter and gray matter exhibit a netlike arrangement in the brainstem connecting the spinal cord, cerebrum, and cerebellum, and mediating the overall level of consciousness
What is the RAS (reticular activating system)?
Ascending portion of the reticular formation
- consists of sensory axons that project to the cerebral cortex, both directly and through the thalamus
- visual and auditory stimuli, mental activities, stimuli from pain, touch, and pressure receptors
What is the most important function of RAS (reticular activating system)?
Consciousness!
- a state of wakefulness in which an individual is fully alert, aware, and oriented
What are the other functions of the RAS?
- Consciousness
- Arousal & awakening from sleep
- Attention & alertness
- Prevents sensory overload
What is the cerebellum?
Occupies the inferior and posterior aspects of the cranial cavity
- highly folded surface area
- 1/10th of overall brain size but 1/2 the total neurons in the brain
What is the function of the cerebellum?
Cerebellum receives information from the sensory systems, the spinal cord, and other parts of the brain and then regulates motor movements.
Cerebellum coordinates voluntary movements such as posture, balance, coordination, and speech, resulting in smooth, balanced muscular activity.
What is the transverse fissure?
Deep groove which supports the superior part of the cerebrum and separates the cerebellum from the cerebrum
What is the vermis?
Central constricted area on the cerebellum
What are the cerebellar hemispheres?
The lateral “wings” or lobes of the cerebellum
What is the cerebellar cortex?
Superficial layer of the cerebellum
- consists of gray matter in a series of slender, parallel folds
What are folia?
Slender parallel folds of gray matter in the cerebellum
What are arbor vitae?
Tracts of white matter in the cerebellum
- deep to the gray matter (in the cerebellar cortex)
What is the diencephalon?
Central core of brain tissue just superior to the midbrain
- extends from brain stem to cerebrum and surround the third ventricle
What does the diencephalon consist of?
Thalamus (80%)
Hypothalamus
Epithalamus
What is the thalamus?
Major relay station for most sensory impulses and motor signals
- regulation of consciousness and sleep
- gray matter organized into nuclei with interspersed tracts of white matter
Where is the thalamus located in the brain?
Just above the brain stem
- between the cerebral cortex and the midbrain
What is the hypothalamus?
Consists of 4 regions:
- Mammillary
- Tuberal -
- Supraoptic
- Preoptic
Where is the hypothalamus located?
Inferior to the thalamus
What are the functions of the hypothalamus?
- Control of ANS
- Production of hormones
- Regulation of emotional and behavioural patterns
- Regulation of eating and drinking
- Control of body temperature
- Regulation of circadian rhythms and states of consciousness
Where is the epithalamus located?
Small region superior and posterior to the thalamus
What does the epithalamus consist of?
- Pineal gland
2. Habenular nuclei
What is the pineal gland?
Part of the endocrine system
- part of epithalamus
What does the pineal gland secrete?
Melatonin
What is melatonin?
Hormone that contributes to sleepiness
- contributes to the setting of the body’s biological clock
What is the cerebrum?
“Seat of intelligence”
- ability to read, write, & speak
(calculations, compose music, remember, plan, imagine)
What does the cerebrum consist of?
- Outer cerebral cortex
- Internal region of cerebral white matter
- Gray matter nuclei deep within the white matter
What is the cerebral cortex?
Region of gray matter that forms the outer rim of the cerebrum
What does the cerebral cortex contain?
Billions of neurons arranged in layers
What are gyri?
Gyrus or convolution
The folds of the cortical region of the cerebrum
What are fissures?
Cerebrum
The deepest grooves between the folds (gyri) in the cerebrum
What are sulci?
Cerebrum
Shallower grooves between the folds (gyri) in the cerebrum
What is the most prominent fissure in the cerebrum?
Longitudinal fissure
- separates the cerebrum into right and left halves
What are the cerebral hemispheres?
The left and right sides of the cerebrum
separated by the longitudinal fissure
What is the corpus callosum?
Broad band of white matter containing axons that extend between the hemispheres
- connect left and right hemispheres of the cerebrum
Where is the central sulcus?
Separates the frontal lobe from the parietal lobe
Where is the frontal lobe?
Anterior aspect of the cerebrum
Where is the parietal lobe?
Directly posterior to the frontal lobe
Where is the precentral gyrus?
Located immediately anterior to the central sulcus
- contains the primary motor area of the cerebral cortex
Where is the postcentral gyrus?
Located immediately posterior to the central sulcus
- contains the primary somatosensory area of the cerebral cortex
Where is the lateral cerebral sulcus?
Separates frontal lobe from temporal lobe
Where is the temporal lobe?
Beneath the temporal bone
- above the ears
Where is the parieto-occipital sulcus?
Separates parietal lobe from occipital lobe
Where is the occipital lobe?
Beneath the occipital bone
- posterior aspect of the cerebrum
Where is the insula located?
Cannot be seen at the surface of the brain
- lies within the lateral cerebral sulcus
- deep to the parietal, frontal, and temporal lobes
What are the names of the lobes of the cerebrum?
- Frontal
- Parietal
- Temporal
- Occipital
Where is the cerebral white matter located?
Deep to the gray matter
What are the three kinds of tracts of cerebral white matter?
- Association tracts
- Commissural tracts
- Projection tracts
What are association tracts?
Contain axons that conduct nerve impulses between gyri in the same hemisphere
What are commissural tracts?
Contain axons that conduct nerve impulses from gyri in one cerebral hemisphere to corresponding gyri in the other hemisphere
What are projection tracts?
Contain axons that conduct nerve impulses from the cerebrum to lower parts of the CNS (thalamus, brain stem or spinal cord) or from lower parts of the CNS to the cerebrum
What are basal ganglia?
Basal nuclei
Three nuclei that are deep within each cerebral hemisphere
What is the function of basal ganglia?
Basal nuclei
Receive input from the cerebral cortex and provide output to motor parts of the cortex
- initiation and termination of movements
- regulate muscle tone
- subconscious contraction of skeletal muscles
- attention, memory, planning
What is the limbic system?
“Emotional brain”
- Primary role in pain, pleasure, docility, affection and anger/fear
- functions in memory
What do the sensory areas of the cerebral cortex receive and what are they involved in?
Receive sensory information
- involved in perception (the conscious awareness of a sensation
What do motor areas of the cerebral cortex control?
Execution of voluntary movements
What do association areas of the cerebral cortex deal with?
More complex integrative functions such as memory, emotions, reasoning, will, judgement, personality traits and intelligence
What is the function of the primary somatosensory area?
Receives nerve impulses for touch, pressure, vibration, itch, tickle, temperature (cold/warm), pain and proprioception (joint & muscle position)
- allows you to pinpoint where somatic sensations originate (able to swat a mosquito)
Where is the primary somatosensory area located?
Directly posterior to the central sulcus of each cerebral hemisphere
What is the function of the primary visual area?
Receives visual information and is involved in visual perception
Where is the primary visual area located?
At the posterior tip of the occipital lobe
- next to the longitudinal fissure
What is the function of the primary auditory area?
Receives information for sound and is involved in auditory perception
Where is the primary auditory area located?
In the superior part of the temporal lobe
- near the lateral cerebral sulcus
What is the function of the primary gustatory area?
Receives impulses for taste and is involved in gustatory perception and taste discrimination
Where is the primary gustatory area located?
At the base of the postcentral gyrus
- superior to the lateral cerebral sulcus in the parietal cortex
What is the function of the primary olfactory area?
Receives impulses for smell and is involved in olfactory perception
Where is the primary olfactory area located?
In the temporal lobe on the medial aspect
- not visible in figure in text
What is the function of the primary motor area?
Each region within the primary motor area controls voluntary contractions of specific muscles or groups of muscles
- any point in primary motor area will cause contraction of OPPOSITE side of body
Where is the primary motor area located?
In the precentral gyrus of the frontal lobe
What is the function of the Broca’s speech area?
Involved mainly in producing speech, writing, and also in language processing and comprehension.
Where is the Broca’s speech area located?
In the LEFT (97% of the population) frontal lobe, close to the lateral cerebral sulcus
What is the function of the somatosensory association area?
Allows you to determine the exact shape and texture of an object by feeling it
- compare current sensations with previous experiences
- allows you to recognize a paperclip simply by touching it
Where is the somatosensory association area located?
Just posterior to the primary somatosensory area
What is the function of the prefrontal cortex?
Frontal association area
Concerned with the makeup of a person’s personality, intellect, complex learning abilities, recall of information, initiative, judgement, foresight, reasoning, conscience, intuition, mood, planning for the future, abstract ideas
Where is the prefrontal cortex area located?
Frontal association area
Extensive area in the anterior portion of the frontal lobe
What is the function of the visual association area?
Receives sensory impulses from the primary visual area and the thalamus
- relates past and present visual experiences
- recognizing and evaluating what is seen
Where is the visual association area located?
In the occipital lobe
What is the function of the auditory association area?
Allows you to recognize a particular sound as speech, music or noise
Where is the auditory association area located?
Inferior and posterior to the primary auditory area in the temporal cortex
What is the function of the Wernicke’s area?
Posterior language area
Interprets the meaning of speech by recognizing spoken words (LEFT side)
- contribute to verbal communication by adding emotional content to spoken words (RIGHT side)
Where is the Wernicke’s area located?
Posterior language area
Broad region of the LEFT temporal and parietal lobes
What is the function of the common integrative area?
Receives nerve impulses from somatosensory, visual and auditory association areas
- Integrates sensory interpretations from the association areas
- formation of thoughts based on a variety of sensory inputs
Where is the common integrative area located?
Bordered by somatosensory, visual and auditory association areas
What is the function of the frontal eye field area?
Voluntary movements of the eye
Where is the frontal eye field area located?
Frontal cortex
What are the language areas of the brain?
- Broca’s speech area
2. Wernicke’s area
What is the function of the medulla oblongata?
- regulates heart beat & blood vessel diameter
- regulates breathing
What is the function of the pons?
- relay nerve impulses from motor areas of cerebral cortex to cerebellum
What is the function of the midbrain?
- coordinate movements of the head, eyes and trunk in response to visual/auditory stimuli
What is the function of the cerebellum?
- smooths and coordinates contractions of skeletal muscles
- regulates posture and balance
What is the function of the thalamus?
- relays almost all sensory input to cerebral cortex
- maintains consciousness
What is the function of the hypothalamus?
- controls and integrates activities of autonomic nervous system
- produces hormones
- regulates emotional and behavioral patterns
- temperature, feeding and thirst regulation centre
What is the function of the epithalamus?
- consists of pineal gland (secretes melatonin)
What is the function of the cerebrum?
- involved in perception of sensory information
- motor areas control voluntary movements
- association areas deal with higher processing
(memory, personality, intelligence)
What is hemispheric lateralization?
Functional asymmetry
- each hemisphere specializes in performing certain unique functions
What is the significance of hemispheric lateralization?
LEFT - reasoning, numerical & scientific skills, spoken & written language
RIGHT - musical & artistic awareness, spatial & pattern recognition, recognition of faces & emotional content
What are brain waves?
Millions of nerve impulses (action potentials) from brain neurons
- electrical signals
What is an electroencephalogram?
EEG
Detects brain waves in the cerebral cortex
- uses electrodes placed on the forehead & scalp
What are EEG’s useful for?
Studying normal brain functions
- diagnosing a variety of brain disorders
- epilepsy, tumors, trauma, hematomas, diseases
What are the four types of brain waves?
- Alpha waves
- Beta waves
- Theta waves
- Delta waves
What are alpha waves?
Present in normal individuals when they are awake, resting with their eyes closed
- disappear during sleep
- 8-13 cycles per second
What are beta waves?
Present when nervous system is active
- during periods of sensory input or mental activity
- 14 - 30 Hz
What are theta waves?
Occur in child and adults experiencing emotional stress
- occur in many disorders of the brain
- 4-7 Hz
What are delta waves?
Occur during deep sleep in adults
- are normal in awake infants
- when produced by an awake adult = brain damage
- 1-5 Hz
How many cranial nerves do we have?
12 pairs
- pass through various foramina in the bones of the cranium
- arise from the brain inside the cranial cavity
- part of the PNS
- there is a 13th!
What are the special sensory nerves?
Cranial nerves I, II and VIII
- associated with smelling, sensing & hearing
What are the mixed nerves?
Cranial nerves V, VII, IX and X
- contain axons of both sensory neurons entering the brain stem and motor neurons leaving the brain stem
What is the name and function of Cranial nerve I?
Olfactory
- smell
What is the name and function of Cranial nerve II?
Optic
- vision
What is the name and function of Cranial nerve III?
Oculomotor
- control some of the muscles moving the eyeballs, changes in size of pupil and shape of lens
What is the name and function of Cranial nerve IV?
Trochlear
- control some of the muscles moving the eyeballs
What is the name and function of Cranial nerve V?
Trigeminal
- carry nerve impulses associated with head sensations and chewing muscles
What is the name and function of Cranial nerve VI?
Abducens
- control some of the muscles moving the eyeballs
What is the name and function of Cranial nerve VII?
Facial
- carry nerve impulses associated with taste, salivation, and muscles of facial expression
What is the name and function of Cranial nerve VIII?
Vestibulocochlear
- carry nerve impulses associated with hearing and equilibrium
What is the name and function of Cranial nerve IX?
Glossoparyngeal
- carry nerve impulses associated with swallowing, salivation and taste
What is the name and function of Cranial nerve X?
Vagus
- carry nerve impulses to and from many organs in the thoracic and abdominal cavities
What is the name and function of Cranial nerve XI?
Accessory
- control head and shoulder muscles
What is the name and function of Cranial nerve XII?
Hypoglossal
- control tongue muscles
What is the name and function of Cranial nerve 0?
Located anterior to the olfactory nerves (I)
- Vomeronasal organs
- might detect pheromones
What is a cerebrovascular accident (CVA)?
Stroke or brain attack
- most common brain disorder
- abrupt onset of persisting neurological symptoms
(paralysis or loss of sensation) that arise from destruction of brain tissue - common causes: intracerebral hemorrhage, emboli (blood clot) & atherosclerosis
What is a transient ischemic attack (TIA)?
Episode of temporary cerebral dysfunction caused by impaired blood flow to part of the brain
- dizziness, weakness, numbness, paralysis in a limb, drooping of one side of the face
- no permanent effects
What is alzheimer disease (AD)?
Disabling senile dementia
- loss of reasoning and ability to care for oneself
- cause is still unknown
What is dementia?
Permanent or progressive general loss of intellectual abilities
- impairment of memory, judgement, abstract thinking and changes in personality
What is encephalitis?
Acute inflammation of the brain
- cause by either direct attack by any of several viruses or an allergic reaction
