CH 13 - The Brain and Cranial Nerves Flashcards
Name the 4 major regions of the adult brain.
Cerebrum, diencephalon, brain stem, cerebellum
Describe the ventricles of the brain.
Lined with ependymal cells
Hollow chambers filled with CSF
Continuous with each other and with the central canal of the spinal cord
What structures protect the brain?
Skull bones, cranial meninges, CSF, blood-brain barrier
Name the layers from the scalp to the brain from most superficial to deep.
Scalp Periosteum Skull bone Periosteal layer (dura mater) Meningeal layer (dura mater) Subdural space Arachnoid mater Subarachnoid space Pia mater Brain
Dura mater “tough mother”
Strongest and most superficial meninx
Made of dense collagenous CT
Outer periosteal layer- fused to periosteum of skull bones
Inner meningeal layer- continuous inferiorly to form the spinal dura mater
Dural venous sinuses
The 2 layers of the dura mater are separated
Forms an interconnected series of chambers (superior/inferior sagittal sinus) that collect venous blood from the brain that drains into the internal jugular vein of the neck
Dural folds
Meningeal layers extend inward to form flat partitions that subdivide the cranial cavity
Provides additional stabilization and support to the brain by limiting excessive movement of the brain within the cranium
Name the 3 dural folds and their locations.
Falx cerebri- separates the two cerebral hemispheres
Falx cerebelli- separates the cerebellar hemispheres
Tentorium cerebelli- separates the cerebrum and cerebellum
Arachnoid mater
Consists of arachnoid membrane and arachnoid trabeculae (fibers that secure arachnoid mater to pia mater)
Arachnoid villus
Knob-like projection of the arachnoid mater that protrudes into the inner meningeal layer of the dura mater and extend into the superior sagittal sinus
Arachnoid granulation
Clusters of arachnoid villi
Subdural space (potential space)
A thin layer of fluid that separates the dura mater and the arachnoid mater
Subarachnoid space
The space beneath the arachnoid membrane that contains arachnoid trabeculae
Filled with CSF and blood vessels
Pia mater “delicate mother”
Highly vascularized delicate connective tissue that adheres directly to the brain via astrocytes
Follows every fold and groove of the brain
Hemorrhage
Bleeding due to a ruptured, damaged, leaky blood vessel
Hematoma
Blood that pools or collects outside of a blood vessel due to trauma, injury, or ruptured blood vessels
Epidural hematoma
Blood pools between the skull bones and the dura mater
Subdural hematoma
Blood pools in the subdural space
Intracerebral hematoma
Blood pools anywhere in the cerebrum
What is cerebrospinal fluid?
Clear fluid produced by the choroid plexus, found in the ventricles, that completely surrounds the CNS (brain and spinal cord)
What are the functions of CSF?
Mechanical protection:
- liquid cushion of the CNS
- shock absorption
- reduces brain weight by 97% from buoyancy
Transports chemical messengers, nutrients, and waste
Choroid plexus
Site of CSF production (500ml/day; 150ml replaced every 8 hours)
Consists of ependymal cells joined by tight junctions, permeable blood capillaries, and fenestrations (gaps between capillaries)
Describe the blood-CSF barrier.
Formed by ependymal cells
Surrounds blood capillaries of the choroid plexus
Limits movement of transferred compounds and allows the chemical composition of blood and CSF to differ
Hydrocephalus
The buildup of CSF in the ventricles
Extra CSF increases the size of the ventricles and puts pressure on the brain
How/where does CSF circulate?
Circulates from choroid plexus through ventricles and into central canal of spinal cord
Constant motion is aided by ependymal cell cilia in the ventricles
Describe the circulation process of CSF.
Lateral ventricle’s choroid plexus produces CSF and adds it to the lateral ventricles, flows through interventricular foramina to
Third ventricle’s choroid plexus produces CSF and adds it to the third ventricle, flows through cerebral aqueduct to
Fourth ventricle’s choroid plexus produces CSF and adds it to the fourth ventricle, flows through lateral and median apertures to
Subarachnoid space, then flows to arachnoid granulations of the superior sagittal sinus, then flows through venous blood in internal jugular veins to heart and lungs, then flows through arterial blood in internal carotid arteries and back to the choroid plexuses of the ventricles
Internal carotid arteries
Blood flow to the brain
Supplies nutrients and oxygen to the brain
Internal jugular veins
Blood flow out of the brain
Removes wastes and carbon dioxide from the brain
Cerebrovascular diesases
Disorders that interfere with blood circulation to or within the brain
Describe the blood-brain barrier (BBB).
Formed by tight junctions between ependymal cells that isolates CNS neural tissue from general circulation
Astrocytes selectively allow substances to cross after releasing chemicals that control endothelium permeability
*Lipid-soluble compounds, oxygen, carbon dioxide, and steroids will bypass the BBB
Describe the cerebrum.
Largest part of the brain, split into two (left and right) cerebral hemispheres
Contains sensory, motor, and association areas
Name the 3 basic regions of the cerebrum.
Cerebral cortex, white matter, basal nuclei
Gyrus
Series of elevated ridges found on the surface of the cerebral hemispheres that increase the surface area
Sulcus
Shallow grooves that separate the gyri
Fissures
Deeper grooves that separate large regions of the brain
Longitudinal fissure- separates left and right cerebral hemispheres
Transverse fissure- separates the cerebrum and cerebellum
Lateral fissure- separates frontal and parietal lobes from the temporal lobe
Describe the cerebral cortex and its hemispheres.
Surface layer of the cerebrum (grey matter) that controls higher mental functions (executive suite; our conscious mind)
Each cerebral hemisphere receives info from and sends commands to the opposite side of the body (contralateral)
Cerebral hemispheres have alike structures, but different functions (functions are not exactly specific to the region)
Name the 4* lobes of the cerebral cortex.
Frontal lobe, parietal lobe, temporal lobe, occipital lobe
*Insula is sometimes considered a fifth lobe
What are the 4 kinds of functional areas found in the cerebral cortex?
Motor areas, sensory areas, association areas, integrative centers
What do motor areas do?
Control voluntary movement
Name the motor areas of the cerebral cortex.
Primary motor cortex (precentral gyrus)
Premotor cortex
Frontal eye field
Broca’s area (motor speech area)
Describe the primary motor cortex (precentral gyrus).
Contains pyramidal cells that allow for control of precise voluntary movement of skeletal muscle
*Long axons of pyramidal cells project to spinal cord, forming voluntary motor tracts called corticospinal tracts
Entire body is controlled spatially and contralaterally
Describe the premotor cortex.
A memory bank for skilled motor activities
Coordinates learned movements
Coordinates the movement of several muscle groups simultaneously or sequentially by sending impulses to the primary motor cortex
Plans movements by using sensory information
Describe the frontal eye field.
Controls voluntary eye movements
Describe broca’s area (motor speech area).
Special motor speech area that directs the muscles involved in speech production and regulates the patterns of breathing and vocalization needed for normal speech
Motor commands are adjusted by feedback from the auditory association area
Present in one cerebral hemisphere (usually left) and becomes active as we think and prepare to speak
What do sensory areas do?
Involved in the conscious awareness of sensation and other sensory information
Name the sensory areas of the cerebral cortex.
Primary sensory cortex (postcentral gyrus) Somatic sensory association area Visual areas -Primary visual cortex -Visual association area -Facial recognition area Auditory areas -Primary auditory cortex -Auditory association area Olfactory areas -Primary olfactory cortex -Olfactory association area Gustatory cortex
Describe the primary sensory cortex (postcentral gyrus).
Receives information from somatic sensory neuron receptors and proprioceptors
Once info is received, the neurons identify the body region being stimulated (spatial discrimination)
Describe the somatic sensory association area.
Monitors and integrates sensory input from the primary sensory cortex to produce an understanding of an object being felt
Stores memories of past sensory experiences
Describe the primary visual cortex.
Receives visual info from the retina of the eye
Involved in visual perception, or a sense of vision
Describe the visual association area.
Receives sensory impulses from the primary visual cortex and thalamus and interprets the results
Uses past/present visual experiences to interpret new stimuli
Describe the facial recognition area.
Receives impulses from visual association area
Stores info about faces and recognition of a person by their face
Describe the primary auditory cortex.
Receives auditory information from the inner ear and interprets pitch, loudness, and location
Describe the auditory association area.
Monitors and receives impulses from the primary auditory cortex
Involved in the perception and understanding of sounds
Stores memories of sounds heard in the past
Describe the primary olfactory cortex.
Receives impulses from sensory neuron smell receptors located in the superior nasal cavities that send impulses via the olfactory tract
Describe the olfactory association area.
Receives sensory impulses from the primary olfactory cortex, giving us conscious awareness of and the ability to differentiate between smells
Describe the gustatory cortex.
Receives info from sensory neuron taste receptors located in the tongue and pharynx
What do the association areas do?
Monitor and interpret information that arrives at the primary sensory areas of the cortex
Name the association areas of the cerebral cortex.
Premotor cortex
Sensory association areas- somatic sensory association area, visual association area, olfactory association area, auditory association area
What do the integrative centers do?
Receive info from many association areas
Direct extremely complex motor activities and perform complicated analytical functions
Name the integrative centers of the cerebral cortex.
Prefrontal cortex
Wernicke’s area
Describe the prefrontal cortex.
Most complicated cortical region
Integrates info from sensory association areas and performs abstract intellectual functions
Involved with intellect, complex learning abilities (cognition), recall, personality, abstract ideas, judgement, reasoning, persistence, planning, empathy, conscience, and mood
Closely linked with limbic system
Describe wernicke’s area
Interprets the meaning of speech by recognizing spoken words
Active during translation of words into thoughts
Works with broca’s area to contribute to verbal communication by adding emotional content
Hemispheric lateralization
Regional specialization of cortical functioning
Left and right cerebral hemispheres have different jobs
*The cerebral hemisphere that controls language is called the dominant hemisphere
What is the difference in white matter and grey mater?
White matter is mostly myelinated axons with some unmyelinated axons
Grey matter is neuron cell bodies and short unmyelinated neurons
What does white matter do?
Responsible for communication between cerebral areas, between cerebral hemispheres, and between cerebrum and spinal cord
Ascending tracts
Bundles of myelinated axons that enter the cerebral hemispheres from a lower area and travel upwards
Carry sensory input
Descending tracts
Bundles of myelinated axons that enter the cerebral hemispheres from a higher area and travel downwards
Carry motor output
Association fibers
Connections within the same hemisphere
Arcuate fibers
Short association fibers that connect one gyrus to another
Longitudinal fasciculi
Longer association fibers that connect one lobe to another
Commissural fibers
Bands of fibers connecting the two cerebral hemispheres
*Corpus callosum, anterior commissure, and posterior commissure
Projection fibers
Connect cerebrum with lower areas
*Diencephalon, brain stem, cerebellum, spinal cord
Internal capsule
Collection of projection fibers
A thick band of white matter that contains all ascending and descending fibers
Corona radiata
Internal capsule fibers that radiate outward through cerebral white matter to the cerebral cortex
Describe basal nuclei.
Nuclei deep within the cerebral white matter, or “islands of grey matter in an ocean of white matter”
Involved with the subconscious control of skeletal muscle tone and coordination of learned movement patterns and rhythm
Consists of: caudate nucleus, putamen, globus pallidus
Lentiform nucleus
Name used when referring to both the putamen and globus pallidus basal nuclei
Corpus striatum
Name used when referring to all three basal nuclei (caudate nucleus, putamen, globus pallidus)
Substantia nigra
A midbrain structure that releases dopamine to inhibit the basal nuclei
Without this, the basal nuclei would become more active, gradually increasing muscle tone and uncoordinated movements
Name the structures of the diencephalon.
Epithalamus, thalamus, hypothalamus
Pineal gland
Structure found in the epithalamus that secretes the hormone melatonin
Describe the thalamus.
The gateway to the cerebral cortex
Left and right thalami held together by the intermediate mass (a flat grey band of tissue)
Coordinates activities of basal nuclei and cerebral cortex by relaying info between them
Afferent impulses from all senses except smell and all body parts converge on the thalamus and synapse with at least one of its thalamic nuclei, is integrated and relayed to a specific association area of the cerebral cortex
All other inputs ascending to the cerebral cortex first go through thalamus
What is the hypothalamus, as part of the diencephalon?
ANS control center and overall body homeostasis regulator
What are the 6 functions of the hypothalamus?
Control ANS
- Adjust/coordinate ANS activities to regulate heart rate, blood pressure, respiration, urinary/digestive functions
- Axons extend from hypothalamus to parasympathetic/sympathetic nuclei in brain stem/spinal cord
Produce hormones
- Produces several hormones
- Connection with pituitary gland
Regulate emotions/behavior
-Part of limbic system
Regulate eating/drinking
-Feeding/satiety/thirst centers
Control body temperature
-Contains temperature regulating center
Regulates circadian rhythm/state of consciousness
-Regulates melanin secretion of pineal gland
What does the limbic system control?
Emotions
Also links feelings and thoughts
Name the main components of the limbic system.
Amygdala, cingulate gyrus, hippocampus, hypothalamus
Describe the amygdala.
Made of left and right amygdalae
Plays a central role in our emotional responses and in forming new memories related to fear
Attaches emotional content to our memories
Describe the cingulate gyrus.
Helps regulate emotions and pain
Involved in predicting and avoiding negative consequences
Describe the hippocampus.
Left and right parts
Important in learning and storage/retrieval of new long-term memories
Memory center of the brain, especially memories of a specific date/place or associated with various senses
New neurons are made from adult stem cells (neurogenesis)
Describe the hypothalamus as part of the limbic system.
Main ANS control center and part of emotional response
Chronic emotional upset can lead to physical ailments (psychosomatic illnesses)
Participates in expressions of rage, aggression, pain, pleasure, and sexual arousal behaviors
Fornix
A tract of white matter that connects the hippocampus to the hypothalamus
Describe the brain stem.
Provides pathways for tracts running between higher and lower brain centers
Produces programmed, automatic behaviors (visceral reflexes) necessary for survival
Brain stem nuclei associated with cranial nerves 3-12
Centers
Clusters of nuclei (grey matter)
Name the structures of the brainstem.
Midbrain (mesencephalon), pons, medulla oblongata
Describe the midbrain (mesencephalon).
Regulates auditory/visual reflexes and controls alertness
Ventral side- 2 Cerebral peduncles (tracts)
Dorsal side- corpora quadrigemina
Connects primary motor cortex and somatic motor neurons of spinal cord via corticospinal motor tracts
Connects to cerebellum via the superior cerebellar peduncle
Describe the corpora quadrigemina.
Sensory nuclei (grey matter)
Consists of superior/inferior colliculi
Describe the superior colliculi.
Receives visual inputs from retina and responds
Visual reflex centers: control the reflex movement of the eyes/head/neck in response to visual/auditory stimuli coming from inferior colliculi
Describe the inferior colliculi.
Part of the auditory relay (hearing receptors in ear, inferior colliculi, thalamus, primary auditory cortex)
Auditory reflex centers: initiate reflex responses to auditory stimuli and communicates to superior colliculi
Describe the pons.
Contains pons nuclei (grey matter), ascending/descending tracts, and transverse fibers
Linked to the cerebellum by the middle cerebellar peduncle
Pontine respiratory group
Nuclei involved with respiration
Modifies the respiratory rate by communicating with medullary respiration center
Pontine storage center & pontine micturition center
Nuclei involved in urination
Micturition: process of urinating
Interacts with cerebral cortex and sacral regions of the spinal cord
Describe the medulla oblongata.
Tracts through the medulla oblongata allow communication between the brain and spinal cord
The crossing-over of its pyramids results in contralateral motor movement
Connected to cerebellum by the inferior cerebellar peduncle
Contains centers for coordination and control of visceral (autonomic) functions/reflexes
Name the centers that relate to the medulla oblongata.
Cardiovascular centers
- Cardiac centers: regulate heart rate and force of contraction
- Vasomotor centers: regulate distribution of blood flow
Medullary respiratory center: controls the rate/depth of breathing (regulated by input from PRG of the pons)
Vomiting center
Deglutition (swallowing) center
Other reflex centers (coughing, sneezing)
Describe the cerebellum.
Provides instructions to motor centers for smooth/coordinated/timely skeletal muscle movement
Responsible for balance and posture by making rapid adjustments to the postural muscles of the body
Electroencephalogram (EEG)
Monitors brain waves and prints a report of the electrical activity of the brain
Name the four types of brain waves seen in an EEG.
Alpha, beta, theta, delta
Describe alpha waves.
Found in healthy/awake adults at rest with closed eyes
Appears as a relatively regular/rhythmic/low amplitude wave that disappears during sleep or concentration
Describe beta waves.
Higher frequency waves found in adults who are intensely concentrating or mentally active
Describe theta waves.
Found in children, intensely frustrated adults, or adults with brain disorders
Describe delta waves.
Found in awake infants, sleeping adults, or adults with severe brain damage
Ataxia
A neurogenerative disease of the nervous system that results in the loss of coordinated movement of skeletal muscle, limbs, and mouth
Cerebral palsy
Refers to any of the neurological disorders that appear in infancy/childhood that permanently affect body movement and muscle coordination
Caused by brain abnormalities/damage/infections
Seizure
A temporary cerebral disorder with varying symptoms that changes the appearance of an EEG
Concussion
A brain injury that can cause headaches, altered levels of alertness, loss of memory, unconsciousness, and/or hematomas
Stupor
A state of near-unconsciousness
Potential causes include abuse/overdose of drugs/medications or extreme heat exposure
Alzheimer’s disease
An irreversible, progressive brain disease caused by the formation of abnormal clumps (amyloid plaques), tangled bundles of fibers (neurofibrillary tangles), and the loss of connections between neurons in the brain
Symptoms include memory loss, language problems, and unpredictable behavior
Most common cause of dementia
Dementia
Chronic disorder of the mental processes caused by brain disease or injury
Marked by memory disorders, personality changes, and impaired reasoning
Parkinson’s disease
A motor system disorder caused by the loss of dopamine-producing neurons in the substantia nigra of the midbrain
Symptoms include tremors, rigidity, slow movement, and postural instability
Huntington’s disease
An inherited disease that causes certain neurons to die
Symptoms don’t appear until middle age, but include uncontrolled movement/balance issues that progress into the inability to walk/talk/swallow, memory disorders, personality changes, and impaired reasoning
Chronic traumatic encephalopathy
A progressive and eventually fatal disease caused by repeated traumatic brain injuries with inevitable dementia
