Chapter 12- The central nervous system Flashcards
What are the 4 regions of the brain in adults?
- Cerebral hemispheres
- Diencephalon
- Brain stem
- Cerebellum
Gray matter
Short, nonmyelinated neurons and neuron cell bodies. Contains dendrites, cell bodies, and axon terminals. Gray matter is peripheral in the brain
Gray matter function
Function- all synapses are found in gray matter- motor controls, sensory perception, decision making, etc
White matter
Myelinated axons, mostly in fiber tracts (bundles of axons that save space). White matter is central in the brain.
White matter function
Function- passes “messages” between different areas of gray matter
Cortex
The outer layer of gray matter in the brain
How are gray and white matter distributed in the brain stem?
Scattered gray matter is found within white matter
How are gray and white matter distributed in the spinal cord?
Gray matter surrounds a central cavity with white matter external to it- similar to the brain
Ventricles
Hollow chambers found in the brain that are filled with cerebrospinal fluid (CSF) and lined with ependymal cells (produce, secrete, and circulate CSF). CSF circulates between all ventricles freely- all ventricles don’t produce their own personal CSF
Where are the ventricles located?
- 2 lateral ventricles- one in each cerebral hemisphere
- Third ventricle- found in diencephalon
- Fourth ventricle- found in the hindbrain, continuous with the central canal of the spinal cord.
All 4 chambers are continuous with one another
Cerebral aqueduct
How the fourth ventricle connects to the third ventricle
Cerebral hemispheres
Form the most superior portion of the brain, make up most of the brain by mass
Regions of the cerebral hemispheres (3)
- Gray matter (cerebral cortex)
- White matter
- Basal nuclei
Gyri
Characteristic ridges of the cerebral hemispheres
Sulci
Characteristic shallow grooves of the cerebral cortex, divides the cerebral hemispheres into lobes. Almost all lobes are named after the bones they are found under (except for the insula).
Longitudinal fissure
Fissure that separates the left and right hemispheres
Transverse cerebral fissure
Fissure that separates the cerebral hemisphere from the cerebellum
Central sulcus
Separates the frontal lobe and the parietal lobe
Parieto-occipital sulcus
Separates the occipital lobe from the parietal lobe
Lateral sulcus
Separates the temporal lobe from the frontal and parietal lobes
Where is the insular lobe located in the brain?
Insula are buried in the lateral sulcus, must cut into the brain to find the insular lobe
Cerebral cortex/gray matter functions (6)
The portion of the brain where the conscious mind is found
Function- provides self awareness, sensation, communication, memory, understanding/learning, initiation of voluntary movement
Functional areas of the cerebral cortex (3)
- Motor areas- control voluntary movement
- Sensory areas- conscious awareness of sensations
- Association areas- integrate diverse information
Contralateral
Describes the cerebral hemispheres- the right hemisphere is concerned with the sensory and motor functions of the left side of the body and vice versa (opposite side of the body from the brain structure).
Are the cerebral hemispheres completely equal in function?
Hemispheres are not completely equal in function- one hemisphere may have structure/function that the other side does not. Ex- Broca’s area (speech) is usually found in the left hemisphere but not the right
How do both sides of the cortex work together?
No functional area of the cortex works alone- conscious behavior involves the entire cortex. The left and right hemispheres interact and send information constantly, some functions require different parts of the brain to work simultaneously.
Motor areas of the cerebral cortex- location and function
Location- frontal lobe, function- controls voluntary movement
Motor areas of the cerebral cortex (4)
- Primary motor cortex
- Premotor cortex
- Broca’s area
- Frontal eye field
Primary motor cortex (motor area)
Function- allows for conscious control of skilled/precise voluntary movements. Two notable components include pyramidal cells and the motor homunculus.
Pyramidal cells
Pyramidal cells are large neurons typically found in primary motor cortex. Axons of these neurons project to the spinal cord, are bundled together to form corticospinal tracts. Neurons directly synapse with and stimulate motor neurons (responsible for motor responses)- help with voluntary movement
Motor homunculus
The body is represented spatially in the primary motor cortex of each hemisphere. The larger the body part, the more precise the movement and more neurons dedicated to that area.
Motor innervation of the body is
Contralateral
Premotor cortex (motor area) functions (3)
- Helps plan movements by selecting and sequencing basic motor movements into more complex tasks
- Controls voluntary actions that depend on sensory feedback
- Sends activating impulses to primary motor cortex to coordinate the movement of several muscle groups
Damage to the premotor cortex can result in (2)
- People with damage to this area might have trouble understanding the physical actions of other people (why they’re moving a certain way)
- Trouble with learning how to do/planning a physical task
Broca’s area (motor area) functions (2)
- Specialized motor speech area that directs muscles involved in speech production
- Becomes active as we prepare to speak (plans speech) or as we plan other voluntary motor activities
Where is Broca’s area found in the brain?
In usually found on one side of the brain only (left side usually)
Damage to Broca’s area can result in (4)
- Being unable to produce speech
- Speech is halting (paused randomly)
- Repetitive speech (repeating the same entire words or sentences multiple times) 4. Disordered sentence structure (all the right words to say something, but the words are spoken in the wrong order)
Frontal area (motor area)
Function- controls voluntary movement of the eyes, important for allowing people to follow movement of objects
Damage to the frontal area causes
Damage= unable or less able to follow a moving object
Sensory area of the cerebral cortex general function
General function (of any area)- allows for conscious awareness of sensation
Parts of the sensory area of the cerebral cortex (8)
- Primary somatosensory cortex
- Somatosensory association cortex
- Visual areas (sight)
- Auditory areas (hearing)
- Vestibular cortex (balance/orientation)
- Olfactory cortex (smell)
- Gustatory cortex (taste)
- Visceral sensory area (sensations of internal organs)
Primary somatosensory cortex location
Parietal lobe
Primary somatosensory cortex function
Function- receive information from the general sensory receptors in skin, form proprioceptors- allows spatial discrimination (you can tell which part of the body is being stimulated). The more sensitive the body region, the bigger it is on the somatosensory homunculus.
Proprioceptors
inform the brain about the body’s position in space
Damage to the primary somatosensory cortex causes
Damage= difficulty perceiving touch in general or on the correct part of the body, have difficulty identifying objects by touch. Also have trouble recognizing parts of their own body
Somatosensory association cortex location
Parietal lobe
Somatosensory association cortex function
Function- integrates sensory input relayed to it via the primary somatosensory cortex- produces understanding of what is being felt (size, texture, relationship of its parts). Example- reaching into your purse and being able to tell your phone from your keys, etc.
Primary visual cortex
Largest cortical sensory area, located in the occipital lobe. Function- receives visual information that originates on the retina in the eye. Originally the image is upside down and backwards- the cortex fixes it
Visual association area
Location- occipital lobe. Function- uses past visual experiences to interpret visual stimuli- allows us to reorganize things
Visual areas of the cerebral cortex (2)
- Primary visual cortex
2. Visual association area
Auditory areas of the cerebral cortex (2)
- Primary auditory cortex
2. Auditory association area
Primary auditory cortex
Location- temporal lobe. Function- interpretation of sound from the inner ear as pitch, loudness, and location of sound in space
Auditory association area
Location- temporal lobe. Function- permits perception of sound stimulus and stores memories of sounds for reference. This is why you can remember songs or recognize people’s voices without seeing them
Vestibular cortex
Location- insula and adjacent parietal cortex (this is where it is believed to be- location is unclear). Function- allows for conscious awareness of balance/orientation
Olfactory cortex
Primary olfactory cortex is the main area. Location- temporal lobe. Function- conscious awareness of different odors, storage of memory so we can remember smells
Gustatory cortex
Location- insula. Function- perception of taste stimuli
Visceral sensory area
Location- insula. Function- allows conscious perception of visceral sensations. For example, you can feel a full stomach or bladder
Lateralization
The division of labor that exists between the two cerebral hemispheres.
Cerebral dominance
One hemisphere “dominates” a particular task- does most of the work, but the other hemisphere will have involvement. This is usually in reference to language. For a small amount of people, the cerebral dominance is flip flopped- this is usually left handed people. For some people, there is no cerebral dominance- usually ambidextrous
Which functions are typically associated with the left side of the brain?
Language abilities, math, logic. Example- the left side of the brain is dominant while speaking publicly, memorizing information
Which functions are typically associated with the right side of the brain?
Visual-spatial skills, insightfulness, creativity. Example- the right side of the brain is dominant for new ideas, art, poetry, etc
Which structures allow both hemispheres to communicate?
Fiber tracts connect the left and right side of the brain- can share information almost instantaneously and allows complete functional integration
Cerebral white matter function
Communication in the CNS. Mostly consists of myelinated fibers bundled into tracts
How is cerebral white matter classified? (3)
- Association of fibers
- Commissural fibers
- Projection fibers
Association of fibers function
Connect different areas of the same hemisphere
Commissural fibers
Connect corresponding areas of different hemispheres. Benefit- allows hemispheres to function as a coordinated “team”
Projection fibers
Allow sensory information to reach cortex motor output to leave the cortex
Basal nuclei/ganglia location
Deep to the white matter in each hemisphere
Basal nuclei/ganglia function (2)
Functions- filters out incorrect or inappropriate responses relating to:
- Muscle movement- the basal nuclei ensures that your muscle movement is coordinated and more precise
- Emotions and cognition- ensures that you don’t react inappropriately as a result of that emotion.
Diencephalon structures (3)
- Thalamus
- Hypothalamus
- Epithalamus
Diencephalon location
Around third ventricle of the brain
Thalamus functions (6)
- Relays sensory information coming into the cerebral cortex
- Information is “edited” here- impulses with similar functions are grouped together and relayed to appropriate part of the cortex
- Motor activities
- Cortical arousal (sleep/wake cycles)
- Learning
- Memory
How does the thalamus relay sensory information that comes into the cerebral cortex?
Your body is constantly sending a stream of sensory information to the cortex- the thalamus sends relevant information to the correct part of the cortex. Like a mail person- the thalamus is not responsible for interpreting or integrating information- just sends it to the right place. Gives a general feeling of “I like this” or “I don’t like this” in response to the stimulus.
Hypothalamus general functions (7)
Main visceral control center in the body:
- Controls autonomic nervous system
- Initiates physical response to emotion
- Regulates body temperature- the body “thermostat”
- Regulates food intake
- Regulates water balance and thirst
- Regulates sleep-wake cycles
- Controls endocrine system function
Which autonomic nervous system functions does the hypothalamus control?
Things that occur without you thinking about them- blood pressure, rate and force of heartbeat, digestive tract mobility, pupil size of the eye, etc. The harder your heart beats, the higher your blood pressure will be. Digestive tract can contract to move things through or can be at rest.
How does the hypothalamus initiate a physical response to emotion?
Involves the limbic system. Involved in perception of pleasure, fear, rage, sex drive, sleep. Ex- pounding heartbeat, sweating, etc.
How does the hypothalamus regulate body temperature?
Monitors the body temperature and initiates cooling down or heat generating processes. The hypothalamus is in close contact to the blood supply- blood temperature indicates internal body temperature
How does the hypothalamus regulate food intake?
Monitors blood nutrient levels (glucose and amino acids, some hormones)
How does the hypothalamus regulate water balance and thirst?
Monitors concentration of body fluid. When concentration is high, thirst is activated
How does the hypothalamus regulate sleep wake cycles?
Uses daylight darkness cues from visual pathways. Visual pathways communicate with the hypothalamus, indicating levels of light. As it gets darker outside, we get more tired
How does the hypothalamus control endocrine system function?
Controls secretion of hormones by other glands (i.e. anterior pituitary)
Epithalamus
Contains the pineal gland, which secretes hormone melatonin. The pineal gland is pre set to release melatonin when it gets dark- you can’t reset it yourself
Why is melatonin secretion important?
Importance- helps regulate the sleep-wake cycle. Only want this to go so far, however-you stop secreting melatonin at some point during the night so you don’t sleep during the day
Regions of the brain stem (3)
- Midbrain
- Pons
- Medulla Oblongata
General functions of the brain stem (3)
- Produces rigidly programmed, automatic behaviors necessary for survival (involuntary behaviors)
- Provides space for fiber tracts running from higher brain centers (cerebral cortex) to lower brain centers
- Innervation of the head- 10 of the 12 pairs of cranial nerves are associated with the brain stem (depends on which part)
The functions of the brain stem occur automatically, we don’t need to think about them
Midbrain functions
- Regulates motor movement
- Regulates hearing and vision
- Alertness- cortical arousal- making you aware of your surroundings and what’s going on
- Temperature control
How does the midbrain regulate motor movement?
Limb flexion, coordinates eye and head movement while following a moving object
How does the midbrain regulate hearing and vision?
Auditory relay from ear to cortex, activate reflexive responses to sound (startle reflex- jumping/moving away from sudden sounds)
Pons functions (4)
- Respiratory control- respiratory rate and depth
- Bladder control- holding urine, controlling act of urination
- Swallowing
- Most functions associated with attached cranial nerves
Medulla oblongata functions
- Cardiovascular center- regulates heart rate and blood pressure
- Respiratory center- controls respiratory rhythm, depth of breath
- Regulation of vomiting, swallowing, coughing, sneezing. Controls the muscles in the esophagus that allow for swallowing and vomiting
Cerebellum location
Dorsal to the pons and medulla oblongata
What is the main function of the cerebellum?
Receives input from motor cortex, brain stem nuclei, and sensory receptors to provide precise timing and appropriate patterns of skeletal muscle tissue movement. Effect- allows smooth, coordinated movement required for everyday life
How does the cerebellum fine tune motor activity? (3 steps)
- Motor areas of the cerebral cortex “notify” cerebellum of intent to initiate voluntary movement (to plan and coordinate movement before the onset of action).
- Proprioceptors relay information to the cerebellum concerning body position, visual and equilibrium pathways send information as well- the cerebellum knows where the body is in space and where it’s going
- Cerebellar cortex “decides” best way to execute movement- force of movement, direction of movement, extent of muscle contraction
Other than coordinating movement, what other functions does the cerebellum have (3)
- Thinking
- Language
- Emotion
How does the cerebellum control thinking, language, and emotion?
The cerebellum collects information from various parts of the body, puts it together, and decides what to do with it to make an appropriate response. Compares expected vs. actual and making adjustments as necessary to ensure appropriate responses
Functional brain systems
Networks of neurons that work together, but span large distances in the brain- cannot be found in only one specific region of the brain
This is concerned with multiple regions of the brain working together.
Examples of functional brain systems (2)
- The limbic system (emotional brain)
2. The reticular formation
Regions of the limbic system (2)
- Amygdaloid body (amygdala)
2. Cingulate gyrus
Amygdala
Functions- response to perceived threats with fear or aggression. Damage= inability to feel fear
Cingulate gyrus functions (2)
- Expressing emotions through gestures- gestures are usually seen with more intense/stronger emotions.
- Resolving mental conflicts during times of frustration. Prevents us from making rash/bad decisions that are based on stronger emotions
Damage to the cingulate gyrus would cause
Expressing emotions inappropriately or not expressing them at all
Which brain system is responsible for emotional responses to smell?
The limbic system. This is adaptive- some smells could indicate toxic substances- they don’t smell good so you move away from them
Limbic system output is relayed through the
Hypothalamus. This has multiple effects, as hypothalamus is the main visceral control center of the body
Why can emotional stress cause visceral illnesses?
This is because limbic system output is relayed through the hypothalamus. Chronic high levels of stress leads to chronically high blood pressure- chronic stress can lead to kidney failure, people who are very sad/frustrated can experience abdominal pain
Psychosomatic illness
Illness with physical symptoms that results specifically from emotional causes.
Prefrontal cortex functions (4)
planning, complex behaviors, personality, social behaviors
Effects of the limbic system interaction with the prefrontal cortex
Intimate relationship between our feelings and our thoughts. We react emotionally to things we consciously understand to be happening, are consciously aware of our emotions, and our brain combines what we are feeling with how we are feeling it. Communication here explains why emotions sometimes override logic (good decision making) or why reason can stop us from expressing emotion inappropriately
Bad decisions result from
The limbic system overriding the prefrontal cortex. The prefrontal cortex can override the limbic system to prevent us from doing something inappropriate (saying something rude in response to anger).
Reticular activating system functions
- Sends a continuous stream of impulses to the cerebral cortex.
- Filters out repetitive, familiar, or weak signals not perceived by the cortex
Why does the cerebral cortex need to receive a continuous stream of impulses
The cortex will be awake as a result of continuous impulses so it can integrate important sensory information. The cerebral cortex is kept alert and excitability is enhanced. Severe injury to the RAS results in a permanent coma (unconscious state- not responsive to stimuli)
Why is it necessary for the RAS to filter out weak or repetitive signals?
The brain doesn’t need to get familiar or weak information constantly- need to focus on more important information. Effect- prevention of sensory overload. About 99% of incoming information is filtered out
What inhibits the RAS?
RAS is inhibited (slowed down) by sleep centers (decreases cortical arousal), depressed by alcohol (why drunk people fall asleep/pass out), sleep inducing drugs, and tranquilizers
What makes the RAS more active?
Certain drugs can make the RAS more active than normal- people on LSD are much more aware of sensations
Which regions of the brain are responsible for language? (3)
- Association cortex
- Broca’s area
- Wernicke’s area
Wernicke’s area
Language comprehension, “speaking clearly”, also usually only found on the left side of the brain. More responsible for understanding spoken and written language than producing it, responsible for coordinating speech.
Functions of the corresponding side of the right hemisphere for speech
- Understanding and interpreting nonverbal components of language (body language)
- Understanding emotional components of language (understanding someone’s tone of voice- using different tones for the same sentence will cause it to mean different things).
Memory
The storage and retrieval of information/past experiences. There are 2 stages: short term (working) memory and long term memory.
Short term/working memory
Stores small amounts of information for short periods of time
Long term memory
Stores large amounts of information for longer periods of time- this does not mean we never forget something that was stored in LTM, depends on the information and how much you use it. Must store information in STM and then transfer it to LTM. Ability to store and retrieve information in LTM declines with age
Transfer from STM to LTM depends on (4)
- Emotional state- heightened emotional state (alert, motivated, shocked, etc) leads to almost instantaneous memory formation and storage.
- Rehearsal- repeating information enhances memory. Cramming is not effective- rehearsal needs to be long term
- Association- linking new information to old information that is already stored in LTM increases memory formation
- Automatic memory- unconscious formation of memory in LTM- memorizing useless things (trivia, fictional characters) that aren’t really important.
Declarative memory
Learning explicit information (factual information). Involves ability to manipulate symbols and language. Example- names and dates. Most of the stuff stored in short and long term memory is declarative
Nondeclarative memory
Procedural memory, motor memory, emotional memory. Memory acquired through repetition and accessed through performance rather than retrieval. Memories acquired through repetition are difficult to “unlearn”. Ex- riding a bike, playing an instrument, etc
Forms of protection for the brain (4)
- Skull
- Meninges
- Cerebrospinal fluid (CSF)
- Blood-brain barrier
Meninges
Connective tissue membranes that surround and protect the brain. Functions- covers and protect the CNS, protect blood vessels around the CNS and enclose venous sinuses, contain CSF, form partitions in the skull (ensures that separate brain structures stay separate).
3 layers of the meninges
- Dura mater- most external layer. Contains two sublayers
- Arachnoid mater
- Pia mater- innermost meningeal layer- clings to the brain surface and is highly vascularized
Dura mater layers (2)
- Periosteal layer- attaches to the inner surface of the skull- most external of the layers. Holds the dura in place, preventing it from moving around inside the skull
- Meningeal layer forms the true external covering of the brain
Subarachnoid space
Beneath the membrane is the subarachnoid space- contains spider web like projections to secure arachnoid mater to the underlying pia mater
Pia mater function
Responsible for allowing blood vessels to pass through that will drain and supply nervous tissue.
Meningitis
Inflammation of the meninges, caused by viruses or bacteria. Viral meningitis is more contagious but less of a threat
Bacterial form is a threat- kills people very quickly (in less than 48 hours)- the bacteria spreads from the meninges into the brain
Cerebrospinal fluid (CSF)
liquid surrounding the brain and spinal cord
What part of the brain forms CSF?
Formed from choroid plexus in the ventricles. The ependymal cells produce and secrete CSF, but they get the raw materials from blood vessels in the choroid plexus.
CSF functions
- Forms liquid cushion- protection from physical trauma
- Gives buoyancy to CNS structures- reduces brain weight by about 97%. Without CSF, your brain would crush itself
- Nutrient and chemical messenger carrier
What creates the blood brain barrier?
Tight junctions between cells making up capillary walls in the CNS- nothing can pass between these junctions. There are also astrocytes and pericytes surrounding the capillary. If something leaks out of the capillary, it must pass by an astrocyte before getting to a neuron. Astrocytes can decide if the substance should go back to the blood supply.
Blood brain barrier functions
Provides a constant environment for CNS tissue operation
Why is it important for the CNS to have a constant environment?
You want to keep the environment as static as possible. Large chemical fluctuations could cause neurons to fire uncontrollably.
You also don’t want neurons exposed to free ions, especially potassium (this could change the resting potential and make it easier or more difficult for action potentials to be fired).
What 2 ways can substances move across the blood brain barrier?
- Simple diffusion allows lipid soluble substances to pass freely
- Specific transport mechanisms move substances important to the brain
Which substances can move across the blood brain barrier by simple diffusion? (6)
Fatty acids, fats, oxygen, carbon dioxide, etc. Most drugs that affect the brain are lipid soluble (alcohol, anesthetic, etc).
Which specific transport mechanisms are used to bring substances into the brain?
Facilitated diffusion- glucose, amino acids, specific ions (no potassium, could be sodium or calcium). This uses a transport protein- no ATP. Transcytosis moves large substances into/out of CNS tissue
Which substances are not allowed entry to the CNS? (6)
Bloodborne metabolic waste, protein, certain toxins, most drugs, nonessential amino acids, potassium ions.
Why are waste products/toxins not allowed to enter the CNS?
Don’t want waste products or toxins building up in the CNS and interfering with neuron functions
Why are proteins not allowed to enter the CNS?
Proteins can build up and form plaques that affect the function of the neurons.
Why are potassium ions not allowed to enter the CNS?
Potassium ions can be catastrophic if they influence resting membrane potential. If they build up, RMP will be more negative.
Why is the blood brain barrier variable in structure and thickness throughout the brain?
In some areas, the barrier is incomplete or absent completely. Function- some parts of the brain need easy access to blood to measure several variables.
Why doesn’t the vomiting center of the brain have a blood brain barrier?
No barrier here allows monitoring of blood for poisonous chemicals/substances
Why doesn’t the hypothalamus have a blood brain barrier?
The hypothalamus monitors blood closely for temperature changes, water balance, and various metabolic activities.
Concussion
alteration in brain functions following a physical blow to the head
This alteration is usually temporary, but multiple concussions will produce cumulative damage- the symptoms of the concussion add together and become more permanent in nature. Can become so severe that the individual becomes suicidal.
Concussion symptoms (6)
Victim may be dizzy or lose consciousness, headache, pressure in the head, confusion, amnesia about what happened before, during, or after injury.
When do symptoms of a concussion become a serious cause for concern?
If the person has severely dilated pupils, especially in bright light, or if the pupils are different sizes and slurred speech.
Contusion
Permanent neurological damage resulting from bruising of the brain. If you’re hit in the head on one side, you will have trauma on that side, but the brain will bounce off your skull and cause trauma on the other side as well.
Contusion symptoms
Symptoms can vary but are generally more severe than concussions. If the brain stem has a contusion, it will cause a coma. Individuals usually lose consciousness.
Subdural/subarachnoid hemorrhage
Bleeding from ruptured blood vessels in/around meninges.
What are the effects of a subarachnoid/subdural hemorrhage on the brain?
Pools of blood increase intracranial pressure and compresses brain tissue. The skull is a hard structure and can’t expand, so blood pushes in on the soft tissue.
Pressure can push the brain stem through the foramen magnum and causes a simultaneous loss of heart rate, respiratory rate, and blood pressure and results in a permanent coma.
Symptoms of a subdural or subarachnoid hemorrhage
Symptoms vary depending on the area of the brain involved. Victim appears lucid immediately after the accident, but progressively becomes worse with time. Symptoms typically present several hours later.
Subdural/subarachnoid hemorrhage treatment
Treatment- surgically removing blood pools and repairing broken blood vessels
Cerebral edema
Swelling of brain tissue by the buildup of fluid (the fluid is not blood) in the brain. Cerebral edema can have different effects: it can aggravate the original head trauma- the damaged part of the brain will be pushed on by the fluid- or it can be fatal on its own
Cerebrovascular accidents (strokes)
The most common cause is a blood clot that blocks the cerebral artery- blood circulation to the brain is blocked and tissue dies. Happens to one side of the brain- the neurons will not receive nutrients or oxygen and will die quickly. The fibers of the brain/spinal cord are contralateral, so a stroke on the left side of the brain would produce symptoms on the right side of the body.
Symptoms of a CVA (3)
Hemiplegia (paralysis on one side- left or right), sensory deficits, trouble vocalizing and/or understanding speech. These effects are not necessarily permanent- depends on severity of the stroke as well as how much physical therapy an individual is willing to go through. However, they won’t get back all of the function they had before
Degenerative brain disorders
Disorders characterized by killing off/breaking down neurons, causes more and more loss of function over time.
Alzheimer’s Disease
Proteins called senile plaques are found throughout the brain and form a wall in between neurons. This prevents neuron communication and eventually also results in cell death due a lack of nutrients. This disease occurs later in life (age 50-60), and survival after diagnosis ranges from 2 years up to 25 years (rarely).
Symptoms of Alzheimer’s Disease
Early symptoms- memory loss (especially recent events), shortened attention span, disorientation.
Long term symptoms- language loss, dementia, changes in personality/mood. Individuals can forget relatives and have sudden mood swings- can become very angry very quickly.
Parkinson’s Disease
Caused by degeneration of dopamine releasing cells in the substantia nigra of the midbrain. The basal nuclei become overactive without dopamine, which has a calming effect on neurons, and will keep firing over and over. People are usually diagnosed around age 60 and can live 10-20 years after diagnosis.
Symptoms of Parkinson’s Disease (3)
Consistent tremors at rest, stiff facial expression, forward-bent walking posture
Huntington’s Disease
Caused by accumulation of huntingtin protein and eventual tissue death- degeneration of the basal nuclei and cerebral cortex. Proteins will block neurons from communicating and from nutrient access, and neurons will die. Individuals live about 20 years after diagnosis
Symptoms of Huntington’s Disease
Early symptoms- jerky, continuous involuntary “flapping” movements called chorea. Late symptoms- marked mental deterioration as large amounts of neurons are killed off. Results in a loss of cognitive and motor functions.
Functions of the spinal cord (2)
- Conduction pathway- carries impulses to and from the brain
- Major reflex center- spinal reflexes are initiated and completed at the spinal cord level
What structures protect the spinal cord (3)?
- Bone- vertebrae
- Meninges- single layered dura mater, arachnoid mater, and pia mater
- Cerebrospinal fluid
Where in the vertebral column is the spinal cord located?
The spinal cord extends from the foramen magnum to L1 or L2
Conus medullaris
Tapered, cone shaped structure where the spinal cord ends
Filum terminale
Fibrous (not nervous- doesn’t send electrical impulses) extension of conus medullaris that extends to the coccyx. Function- helps to hold the spinal cord in place.
Where are the meninges located in the spinal column?
The dural and arachnoid membranes continue past conus medullaris to the sacral vertebrae, the pia stops after the spinal cord. This allows a site for spinal tap to withdraw CSF without spinal cord injury.
Where does the spinal cord enlarge?
The width of the spinal cord is fairly consistent along its length, but there are cervical and lumbar enlargements that mark where nerves serving upper and lower limbs arise
How many pairs of spinal nerves are there?
31
Cauda equina
Collection of nerve roots at the end of the vertebral canal
What are the two grooves that partially divide the spinal cord into left and right halves?
- Ventral median fissure
2. Dorsal median fissure
Central canal of the spinal cord
Located at the very center of the spinal cord, serves the spinal cord with CSF. It is enclosed by the gray commisure.
Gray commisure
Thin layer of gray matter that encloses the central canal of the spinal cord
Where is the gray and white matter of the spinal cord located?
Gray matter is internal, white matter surrounds gray matter (is more superficial)
Dorsal horns
Projections of gray matter on the dorsal side of the spinal cord, consists of interneurons. Efferent function- receives somatic and visceral sensory input
Ventral horns
Projections of gray matter on the ventral side of the spinal cord, consists of interneurons and somatic motor neurons. Function- motor output
Lateral horn
Projection of gray matter found only in thoracic and superior lumbar segments. Function- contains sympathetic neurons that serve visceral organs, neurons travel through the ventral roots to get to their destination
Ventral roots
Where axons of ventral horn motor neurons (efferent fibers) exit the spinal cord.
Dorsal roots
Where axons of sensory receptors (afferent fibers) enter the spinal cord
Dorsal root ganglia
Swelling of a portion of the dorsal root where cell bodies of sensory neurons are found
How are spinal nerves formed?
Dorsal and ventral roots fuse laterally to form the spinal nerves
Somatic sensory subdivision
Dorsal horn subdivision. Function- receive input from somatic sensory neurons
Visceral sensory subdivision
Dorsal horn subdivision. Function- receive input from visceral sensory neurons
Visceral motor subdivision
Ventral horn subdivision. Function- conduct impulses to smooth muscle, cardiac muscle, and glands
Somatic motor
Ventral horn subdivision. Function- conduct impulses to skeletal muscle tissue
Damage to the dorsal roots/sensory tracts causes
Loss of sensation or paresthesia (abnormal sensation- tingling like when the arm falls asleep). This is just a loss of information for what is passing through the spinal cord at that point
Damage to the ventral roots/motor tracts causes
Paralysis (loss of motor function)
2 types of paralysis
- Flaccid paralysis
2. Spastic paralysis
Flaccid paralysis
Injury to the spinal cord or ventral roots prevents impulses from reaching skeletal muscle tissue. Effect- muscles innervated by damaged portions cannot move voluntarily or involuntarily
Spastic paralysis
Caused by head trauma (not spinal trauma). Upper motor neurons of primary motor cortex are damaged- they are responsible for voluntary movement. Spinal motor neurons are still intact- spinal reflexes can still occur. Effect- muscle can still move, but it is completely involuntary.
Transection of the spinal cord
Complete cross-sectioning of the spinal cord- neurons can’t jump the gap between the spinal cord ends or send impulses that will jump the gap. Effect- complete sensory and motor loss below the point where the spinal cord was severed, causing quadriplegia or paraplegia
Paraplegia
Transection between T1 and L1
Effect- loss of lower limb functioning
Quadriplegia
Transection anywhere in cervical region
Effect- loss of function in all limbs- legs and arms
Amyotrophic Lateral Sclerosis (Lou Gehrig’s Disease)
Progressive and degenerative condition caused by destruction of ventral horn motor neurons and fibers, usually by genetic factors (a very small percentage inherit the mutation from their parents) with some environmental factors. The majority of the time it is caused by a random mutation.
Results in a loss of skeletal muscle function- individuals have a loss of ability to speak, swallow, and breathe, condition is fatal within about 5 years. The diaphragm is skeletal muscle tissue that must contract and relax for breathing- this is the most fatal part of ALS.
