A&P Chapter 12 Flashcards
Adult brains have how many regions?
Four
What are the four regions of the adult brain?
- Cerebral hemispheres
- Diencephalon
- Brainstem (Midbrain, pons, medulla)
- Cerebellum
What are ventricles?
Fluid-filled chambers that are continuous to one another and to the central canal of the spinal cord
What are ventricles filled with?
Cerebrospinal fluid (CSF)
What does gray matter contain?
Neuron cell bodies and short nonmyelinated neurons
What does white matter contain?
Mostly myelinated axons and some nonmyelinated axons
What are ventricles lined by?
Ependymal cells (neuroglial cells)
Paired lateral ventricles are what?
Large, C-shaped chambers located deep in each hemisphere
What are the lateral ventricles separated by?
Septum pellucidum
The third ventricle is connected by what?
Interventricular foramen
The fourth ventricle is connected by what?
Cerebral aqueduct
The meninges cover and protect what?
CNS
What are the three layers of meninges (external to internal)?
Dura mater, arachnoid mater, and pia mater
What is the subdural space?
In between the dura and arachnoid mater
What is the subarachnoid space?
In between the arachnoid and pia mater
What does the subarachnoid space contain?
CSF and the largest blood vessels of the brain
What is meningitis?
Inflammation of the meninges primarily due to bacterial or viral infection
If meningitis spreads to the CNS, what could happen?
Inflammation of the brain, referred to as encephalitis
How is meningitis usually diagnosed?
By observing microbes in a sample of CSF obtained via lumbar puncture
What are the symptoms of meningitis?
Fever, headache, vomiting, and stiff neck (more severe with bacterial infection)
Meningitis can result in what if untreated?
Brain damage and death
How can meningitis be prevented?
Vaccine for most common bacterial strains causing meningitis
What does the CSF form?
A liquid cushion of constant volume around the brain
What are the functions of CSF?
- Gives buoyancy to CNS structures (reduces weight of brain by 97% by floating it so it is not crushed under its own weight)
- Protects CNS from blows and other trauma
- Nourishes brain and carries chemical signals
What is the CSF composed of?
Watery solution formed from blood plasma, but with less protein and different ion concentrations from plasma
What is the choroid plexus?
Cluster of capillaries that hangs from roof of each ventricle, enclosed by the pia mater and surrounding layer of ependymal cells
CSF is filtered from the plexus at a ______ rate
Constant
Ependymal cells use ____ -___ to control the composition of CSF and helps cleanse the CSF by removing wastes
Ion pumps
What keeps CSF in motion?
Cilia of ependymal cells
What is the normal adult CSF volume, and how often is it replaced?
~150ml, and is replaced every 8 hours
What is the blood brain barrier?
Helps maintain stable environment for the brain and prevent neuron exposure to harmful substances.
What can pass the blood brain barrier?
Some drugs and alcohol
What are the 3 important features of the blood brain barrier?
- Tight junctions ensure substances pass through, not around endothelial cells
- Feet of astrocytes and smooth muscle-like pericytes surround endothelial cells
- Continuous basement membrane
What do the cerebral hemispheres form?
Superior part of the brain
What percentage of brain mass do the cerebral hemispheres form?
83%
What are the brain surface markings?
Gyri, sulci, fissures (longitudinal and transverse)
What are gyri?
Ridges
What is sulci?
Shallow grooves
What are fissures?
Deep grooves
What is the longitudinal fissure?
Separates two hemisphere
What is the transverse cerebral fissure?
Separates cerebrum and cerebellum
What are the 5 cerebral lobes?
- Frontal
- Parietal
- Temporal
- Occipital
- Insula
What does the frontal lobe do?
Voluntary motor functions, concentration, communication, decision making, planning, and personality
What does the parietal lobe do?
Serves general sensory functions
What is an example of what the parietal lobe does?
Evaluating shape and texture of objects
What does the temporal lobe do?
Hearing and smell
What does the occipital lobe do?
Functions in vision and visual memories
Where is the insula?
Deep to lateral sulcus
What does the insula do?
Functions in memory and sense of taste
What is the cerebral cortex known as?
Executive suite of the brain
What does the cerebral cortex do?
Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory, storage, and understanding
What is the cerebral cortex composed of?
Thin (2-4mm) superficial layer of gray matter composed from neuron cell bodies, dendrites, glial cells, and blood vessels
What does the cerebral cortex not contain?
Axons
What percentage of brain mass does the cerebral cortex make up?
40%
What are the features of the cerebral cortex?
- Contains three types of functional areas (motor, sensory, association)
- Each hemisphere is concerned with contralateral (opposite) side of body
- Lateralization (specialization) of cortical function can only occur in one hemisphere
- Conscious behavior involves entire cortex in one way or another
What are the three types of functional areas of the cerebral cortex and what do they do?
Motor areas = controls voluntary movement
Sensory areas = conscious awareness of sensation
Association areas = integrate diverse information
What do motor areas of the brain contain?
Primary motor cortex, premotor cortex, frontal eye field, Broca’s area
Where is the primary (somatic) motor cortex?
Located in the precentral gyrus of the frontal lobe
What does the primary (somatic) motor cortex do?
Allows conscious control of skilled voluntary movement of skeletal muscles
What is somatotopy?
All muscles of the body can be mapped to area on the primary motor cortex
What is the motor homunculi?
Upside-down caricatures represents contralateral motor innervation of body regions
What is Broca’s area?
Motor speech area that directs muscles of speech production, also active in planning speech and voluntary motor activities
Where is Broca’s area?
Present in one hemisphere (usually the left)
What does the frontal eye field contain?
Controls voluntary eye movements
Damages to areas of the primary motor cortex (like in a stroke) does what?
Paralyzes muscles controlled by those areas
Paralysis occurs on the _____ side of the body from the damage
Opposite
What is not impaired in damage to the primary motor cortex?
Muscle strength or ability to perform discrete individual movements is not impaired
What is an example of damage to the primary motor cortex?
Damage to the premotor area controlling movement of the fingers would still allow the fingers to move, but voluntary control needed to type would be lost
Other premotor neurons can be _______ to take over the skill of damage neurons?
Reprogrammed
What is FAST for a stroke?
(F)ace drooping
(A)rm weakness
(S)peech difficulty
(T)ime to call 911
What does the sensory areas and related association areas contain?
Primary somatosensory cortex, somatosensory association cortex, gustatory cortex, vestibular cortex, Wernicke’s area, primary visual cortex, visual association area, auditory association area, primary auditory cortex
What does the primary somatosensory cortex recieve?
General sensory information from skin and proprioceptors of skeletal muscle, joints, and tendons
What is the primary somatosensory cortex capable of?
Spatial discrimination
What is spatial discrimination?
Identification of body region being stimulated
What is the somatosensory homunculus?
Upside-down caricature represent contralateral sensory input from body regions
What is lateralization?
Hemispheres are not identical
What is cerebral dominance?
Refers to hemisphere that is dominant for language
What percentage of humans have left-sided dominance?
90%
What does left-sided dominance usually result in?
Right-handedness
The roles of hemispheres are reversed in what percentage of humans?
10%
What does the left hemisphere do?
Controls language, math, and logic
What does the right hemisphere do?
Visual-spatial skills, intuition, emotion, artistic and musical skills
Hemisphere communicates almost instantaneously via what?
Fiber tracts and functional integration
What are the cerebral white matter tracks responsible for?
Responsible for communication between cerebral areas, and between cortex and lower CNS
What does the cerebral white matter tracks consist of?
Myelinated fibers bundled into large tracts
How are cerebral white matter classified?
According to the direction they run
What are the classifications of cerebral white matter?
Association, commissural, and projection fibers
What are association fibers?
Horizontal running fibers that connect different parts of the same hemisphere
What are commissural fibers?
Horizontal fibers that connect gray matter of two hemisphere
What is an example of commissural fibers?
Corpus callosum
What are projection fibers?
Vertical fibers that connect hemispheres with the lower brain or spinal cord
What is Huntington disease?
Hereditary disease affecting the cerebral nuclei
What is the physiology of Huntington’s?
Mutated Huntingtin protein (HTT), which is toxic to neurons
What are some symptoms of Huntington’s?
Rapid, jerky, involuntary movements and intellectual deterioration
What is the prognosis of Huntington’s?
Fatal within 10-20 years after onset
What is the physiology of Parkinson’s disease?
Decreased dopamine production and death of neurons in the substantia nigra
What does Parkinson’s disease affect?
Muscle movement and balance
What are symptoms of Parkinson’s disesase?
Stiff posture, slow voluntary movements, resting tremor
What does the diencephalon contain?
The epithalamus, thalamus, and hypothalamus
What does the diencephalon do?
Provides relays and switching centers for sensory, motor, and visceral pathways
What is the epitalamus?
The most dorsal portion of the diencephalon that forms the roof of the third ventricle
What does the epithalamus contain?
The pineal gland (body)
Where is the pineal gland in the epithalamus?
Extends from the posterior border
What does the pineal gland do?
Secretes melatonin that helps regulate the sleep-wake cycle
What is the main thalamic function?
Acts as relay station for information coming into the cortex
The thalamus sorts, edits, and relays ascending input such as what?
- Impulses from hypothalamus for regulating emotion and visceral function
- Impulses from cerebellum and basal nuclei to help direct motor cortices
- Impulses for memory or sensory integration
What does the thalamus do overall?
It acts to mediate sensation, motor activities, cortical arousal, learning, and memory
What is an example of what the thalamus does?
Filters background noise in a crowded room
What is the hypothalamus?
Control center of the body
What is the infundibulum?
Stalk that connects to the pituitary gland and controls hormone release
What are some things that the hypothalamus regulates?
Body temperature, regulates, hunger, thirst, and sleep-wake cycles
What does the hypothalamus control?
Autonomic nervous system
What are some examples of things that the hypothalamus controls that are a part of the autonomic nervous system?
Blood pressure, rate and force of heartbeat, digestive tract, motility, and pupil size
The hypothalamus initiates physical responses to ______
Emotions
As a part of the limbic system, what are some examples of the hypothalamus initiating physical responses to emotions?
Perceives pleasure, fear, rage, biological rhythms, and drives (like the sex drive)
What makes up the midbrain?
Corpora quadrigemina and the cerebral aqueduct
What makes up the brainstem (superior to inferior)?
Midbrain, pons, medulla oblongata
What does the brain stem control?
Controls autonomic behaviors necessary for survival
What does the midbrain connect
Connects cerebrum, diencephalon, and cerebellum to the spinal cord
What is the midbrain?
Relay center for visual and auditory
Midbrain nuclei scattered throughout white matter include what?
Corpora quadrigemina and substantia nigra
What is the corpora quadrigemina?
Paired dorsal protrusions
What is the substantia nigra?
Functionally linked to basal nuclei
What disorder involces the substantia nigra?
Parkinson’s
Where is the pons?
Located between the midbrain and medulla oblongata
What does the pons connect?
Higher brain centers and spinal cord
The functions of the medulla oblongata overlap with what?
The hypothalamus
What are some functions of the medulla oblongata?
Rate and depth of breathing, force and rate of heart contraction and cardiac output, blood vessel diameter and blood pressure
What does the medulla oblongata regulate?
Vomiting, hiccupping, swallowing, coughing, and sneezing
Cerebrellar hemispheres are connected by what?
Vermis
What does the cerebellum do?
Processes input from the cortex, brain stem, and sensory receptors to provide precise coordinated movements of skeletal muscles
What does the cerebellum do?
Processes input from the cortex, brain stem, and sensory receptors to provide precise coordinated movements of skeletal muscles
The cerebellum plays a major role in what?
Balance
What does the limbic system do?
Processes and experiences emotion
What is the limbic system called?
The emotional brain
What makes up the limbic system?
Cingulate gyrus, hippocampus, amygdaloid body, olfactory bulbs, olfactory tracts, olfactory cortex
What is does the cingulate gyrus do?
Expressing emotion via gestures, resolves mental conflict
What does the hippocampus do?
Helps form long-term memories
What does the amygdaloid body do?
Involved in many aspects of emotion and emotional memory, especially fear, extreme happiness or sadness
What does the olfactory bulbs, tracts and cortex do?
Process ordors that can provoke emotions
Analysis of higher mental functions include what?
- Language
- Memory
- Brain waves and EEGs
- Consciousness
- Sleep and sleep-wake cycles
The language implementation system involves association cortex of which hemisphere?
Left
What are the main language areas?
Broca’s area and Wernicke’s area
Broca’s area is involved in what?
Speech production
Patients with lesions in Broca’s area do what?
Understand words, but cannot speak
What is the Wernicke’s area involved in?
Understanding spoken and written words
Patients with lesions in Wernicke’s area do what?
Can speak, but words are nonsensible
Corresponding language areas on the right side are involved with what?
Nonverbal language components
What is memory?
Storage and retrieval of information
What are the different kinds of memory?
Declaritive, procedural, motor, and emotional memory
What is declarative memory?
Facts
What are some examples of declarative memory?
Names, faces, words, and dates
What is an example of procedural memory?
Playing piano
What is an example of motor memory?
Riding a bike
What is emotional memory?
Memory of experiences linked to an emotion
What is an example of emotional memory?
Heart pounding when you hear a rattlesnake
What are the two stages of declarative memory storage?
Short-term memory and long-term memory
What is short-tem/working memory?
Temporary holding of information, limited to seven or eight pieces of information
What is the capacity of long-term memory?
Limitless
What causes amnesia?
Damage to the hippocampus or surrounding temporal lobe structures on either side result in only slight memory loss
What causes widespread amnesia?
Bilateral destruction
What is retrograde amnesia?
Loss of memories formed in the distant past
What is anterograde amnesia?
Consolidated memories are not lost, but new inputs are not associated with old ones
How does a person with anterograde amnesia live?
Lives in the here and now
WHat is an example of anterograde amnesia?
Memory of conversations from just 5 minutes before would not be remembered
What is Alzheimer’s disease?
Progressive degenerative disease of the brain that results in dementia
When does Alzheimer’s occur?
After age 65
What are symptoms of Alzheimer’s?
Memory loss, short attention span, disorientation, eventual language loss, irritability, moodiness, confusion, and hallucinations
What is an early sign of Alzheimer’s?
Loss of sense of smell
What causes Alzheimer’s?
Beta-amyloid plaques and neurofibrillary tangles
What is beta-amyloid plaques?
Peptides form in the brain
What are neurofibrillary tangles?
Inside neurons interfere with transport neurons, eventually killing the neuron
As brain cells die, what happens to the brain?
The brain shrinks
What is an epileptic seizure?
Torrent of electrical discharges by groups of neurons that prevents any other messages from getting through
Victims of epilepsy may experience what?
Loose consciousness, fall stiffly, and have uncontrollable jerking
Epilepsy is not associated with what?
Intellectual impairments
How often does epilepsy occur?
1% of the population
What are risk factors of epilepsy?
Brain injuries, stroke, infections, or tumors, as well as genetic factors
What is a febrile seizure?
A convulsion ina child caused by a spike in body temperature, often in infection
Who gets febrile seizures?
Young children with normal development without a history of neurological symptoms
Children typically grow out of febrile seizures by what age?
6
What are the types of brain injury?
- Concussion
- Contusion
- Subdural/Subarachnoid hemorrhage
- Cerebral edema
What is a concussion?
Temporary alteration in fuction
What is a contusion?
Permanent damage
What can a subdural/subarachnoid hemorrhage cause?
Pressure from blood may force brain stem through foramen magnum, resulting in death
What is cerebral edema?
Swelling of brain associated with traumatic head injury
What are the 4 subdivisions of the spinal cord?
- Cervical
- Thoracic
- Lumbar
- Sacral
The spinal cord terminates at what?
Conus medullaris
What is the filum terminale?
Extension of pia mater that extends to coccyx and anchors spinal cord
What are cervical and lumbar enlargements?
Areas where nerves servicing upper and lower limbs arise from the spinal cord
What are paired spinal nerves?
A part of the PNS, and attach to the spinal cord by 31 paired roots
What is cauda equina?
Collection of nerve roots at the inferior end of the vertebral canal
The spinal cord is enclosed in what?
Vertebral column
Where does the spinal cord begin?
Foramen magnum
Where does the spinal cord end?
L1 or L2 vertebra
What are the functions of the spinal cord?
- Provides two-way communication to and from brain and body
- Major reflex center: reflexes are initiated and completed at the spinal cord
How thick is the spinal dura mater?
One layer thick
Does the spinal dura mater attach to the vertebrae?
No
What is the epidural space?
Cushion of fat and network of veins in the space between vertebrae and spinal dura mater
CSF fills what space?
Subarachnoid space between arachnoid and pia maters
Dural and arachnoid membranes extend to where?
Sacrum, beyond the end of cord at L1 or l2
Where is the site of lumbar puncture or tap?
Dural and arachnoid membranes
Two lengthwise grooves that run the length of the cord partially divide it into right and left halves, what are they called?
Ventral (anterior) median fissure and dorsal (posterior) median sulcus
Where is gray matter located in the spinal cord?
Core (H and horns)
Where is white matter located in the spinal cord?
Funiculi
The central canal runs where?
Length of the cord
What is the central canal filled with?
CSF
What are ventral roots?
Bundle or motor neuron axons that exit the spinal cord
What are dorsal roots?
Sensory input to cord
What are the dorsal root (spinal) ganglia?
Cell bodies of sensory neurons
What are spinal nerves?
Formed by fusion of dorsal and ventral roots
What is gray matter made of?
Neuron cell bodies, dendrites, unmyelinated axons and glial cells
What do anterior horns house?
Cell bodies of somatic motor neurons
What do lateral horns house?
Cell bodies of autonomic motor neurons
Lateral horns are only present where?
T1-L2
What do posterior horns house?
Axons of senosry neurons and cell bodies of interneurons
What is the gray commissure?
Horizontal band of gray matter surrounding the canal
What does the gray commissure contain?
Unmyelinated axons connecting left and right gray matter
White matter runs in what three directions?
Ascending, descending, and transverse
What is the ascending direction?
Up to higher centers
What is the descending direction?
From brain to cord or lower cord levels
What is the transverse direction?
From one side to another
What is the ascending direction associated with?
Sensory inputs
What is the descending direction associated with?
Motor outputs
What is the transverse direction associated with?
Commissural fibers
Spinal pathways are _____ or ______
Sensory or motor
Sensory pathways ______ toward the brain
Ascend
Motor pathways ________from the brain
Descend
What are the common pathway characteristics?
- Cell locations
- Each pathway is made of a chain of two or more neurons
- Pathways are paired (left & right)
- Most pathways are decussate
What are the cell locations in conduction pathways?
Axons are in the spinal cord tracts, cell bodies are in the ganglia, spinal cord gray horns, and brain gray matter
What does decussate mean?
Axons cross the midline so brain processes information for the contralateral side
Uncrossed pathways work on the ________ side of body
Ipsilateral (same side)
What is spinal cord trauma?
Localized injury to the spinal cord or its roots leads to functional losses
What is paresthesia caused by?
Caused by damage to dorsal roots or sensory tracts
What does paresthesia lead do?
Sensory function loss
What is paralysis caused by?
Damage to ventral roots or ventral horn cells
What does paralysis lead to?
Motor function loss
Transection/cross sectioning of the spinal cord at any level results in what?
Total motor and sensory loss in regions inferior to the cut
What is paraplegia?
Transection between T1 and L1
What is quadriplegia?
Transection in cervical region
What is poliomyelitis?
Destruction of ventral horn motor neurons by poliovirus causing muscle atrophy
What is the prognosis of polio?
Death may occur from paralysis of respiratory muscles or cardiac arrest
What is Amyotrophic lateral sclerosis/ Lou Gehrig’s disease?
Destruction of ventral horn motor neurons and fibers of pyramidal tract
What are the symptoms of ALS?
Loss of ability to speak, swallow, and breathe
What is the prognosis of ALS?
Death typically occurs within 5 years
What is cerebral palsy?
Neuromuscular disability involving poorly controlled or paralyzed voluntary muscles
What causes cerebral palsy?
Brain damage, possibly from lack of oxygen during birth
What is seen in cerebral palsy?
Spasticity, speech difficulties, and motor impairments
Some patients that have cerebral palsy can have what?
Seizures, intellectual impairment, and deafness
What is common in cerebral palsy?
Visual impairment
What is anencephaly?
Cerebrum and parts of the brain stem never develop because neural folds fails to fuse
How does the child appear in anencephaly?
Vegatative
What is the prognosis of anencephaly?
Death occurs soon after birth
What is spina bifida?
Incomplete formation of vertebral arches, typically involves lumbosacral region
What is spina bifida occulata?
Least serious, involves only one or few missing vertebrae and usually causes no neural problems
What are two signs of spina bifida occulata?
Sacral dimple or patch of hair
