Neuroanatomy Midterm Flashcards
how have neuroscientists learned about the brain?
observation of how damage or lesions to specific areas of the brain affect behavior and other neural functions
The nervous system is divided into what 2 systems?
- Central nervous system-brain and spinal cord
- Peripheral nervous system-all the neurons in the body outside the cns, cranial nerves, spinal nerves, ganglia-further divided into somatic nervous system and autonomic nervous system
Somatic Nervous System
part of the peripheral nervous system, made up of:
- afferent neurons- convey information from the sense organs to the brain and spinal cord
- efferent- carry motor instructions to the muscles from the brain
Autonomic Nervous System
part of the peripheral nervous system, made up of:
- sympathetic nervous system- a set of nerves that activate “fight or flight” response, preparing the body for action.
- parasympathetic nervous system- prepares the body to rest and conserve energy
how many miles of fibers are in the nervous system
90,000 miles
how many receptors do you have
19,000
What are glial cells?
They are the non excitable cells of the nervous system, they provide support and protection to the neurons.
- smaller than neurons
- capable of mitosis
- do not transmit impulses
- physically protect and help nourish neurons
- provide the supporting framework for all nervous tissue
- far outnumber neurons
what are the glial cells of the cns?
Astrocytes, ependymal cells, microglia and oligodendrocytes
what are astrocytes?
make up 90% of glial cells in cns -star like shape -help form the blood-brain barrier-strictly controls the substances entering the nervous tissue in the brain from the bloodstream. Fx: -regulate tissue fluid composition -provide structural integrity -replace damaged neurons -assist in new neuronal development
what are ependymal cells?
cuboid ET-cilia on apical surface circulate cerebral spinal fluid
line internal cavities
make contact with other glial cells
help form choroid plexus
what are microglia cells?
smallest % of CNS glial cells phagocytic -move through tissue in response to infection -remove debris -like macrophages
what are oligodendrocytes?
CNS glial cells
they are large with big body and processes
form myelin sheaths-speeds up transmission
what are the glial cells of the PNS?
satellite cells-flattened cells, cover somas in ganglia, separate soma from surrounding tissue fluid-regulate exchange
neurolemmocytes (schwann cells)-PNS myelination
What is myelination?
process by which part of an axon is wrapped with a myelin sheath
-forms a protective fatty coating
-glossy white appearance
The myelin sheath- supports, protects and insulates the axon
Where do voltage changes occur in myelination?
Voltage change occurs at the nodes, it cannot occur across the membrane in the insulated portion of an axon
oligodendrocyte- produce sheath in CNS
neurolemmocyte-produce sheath in PNS
difference between myelinated vs. unmyelinated
myelinated axon:
-nerve impulse “jumps from neurofibril node to neurofibril node (saltatory conduction)
-requires less ATP
-Produce faster nerve impulse
unmyelinated axon:
-must travel entire length of axon (continuous conduction)
-take longer to reach end of axon
-conduct nerve impulses from pain stimuli
Types of Nerves
- sensory (afferent)-convey sensory info to CNS
- motor (efferent)-convey motor impulses from CNS to muscles and glands
- mixed-both sensory and motor
what are the organs of the PNS?
nerves
Where do axons terminate?
as they contact other neurons, muscle cells or gland cells
where do axons transmit nerve impulses?
at a specialized junction with another neuron called synapse
Neuron Structure (Nerve Cell)
- cell body-nucleus–genetic info
- dendrites-recieve info
- axon-carry info long distances; myelin
- axon terminals-transmit info
Facts about Axons
- tip of a growing axon consists of a blob or protoplasm called a growth cone and is studded with chemical receptors
- these receptors sense the local environment
- causing the growth cone to be attracted or repelled by various cellular elements–thus pulled in a particular direction at each point along its path
Axon path finding process to develop synapses
The growth cone navigates through the brain until it reaches its destination area–here other chemical cues cause it to begin generating synapses
Many thousands of genes give rise to proteins that influence the axonal path finding. The pool of neurons is largely in place at birth–but still continues to develop for a long time afterward.
How large is a new born baby’s brain and how many nerve cells are present, after 40 weeks of gestation?
2/3 the size of an adult brain with one million million nerve cells (1,000,000,000,000)–however the intercellular connections which brain function depends on are far from complete
how many synapses does one mature cortical nerve cell have?
10,000 synapses per mature cortical nerve cell
average number of synapses in the individual’s cortex
10 to the 15th power
what can cause mental difficulties in childhood?
if the mother severely undernourished or in extreme mental stress during critical brain growth periods in gestation, also infections, drinking alcohol, taking drugs and smoking while she is pregnant is all transferred to the unborn child via the placenta
Average weight and consistency of the the brain
between 2.87 and 3.1 lbs, made of a very soft tissue that is jello-like. Pinkish on the outside and mostly white on the inside
Blood Brain Barrier
Blood vessels evert the CNS throughout the perivascular space above the pia mater, their cells in the vessel wall are bound tightly to form the bbb, to protect the brain from toxins that might enter through the blood stream. It is the separation between the circulating blood and extra cellular fluid in the CNS, occurring along all capillaries and consists of extra capillaries that don’t exist in normal circulation. Endothelial cells are in charge of restricting things like bacteria and hydrophilic molecules, while letting hydrophobic ones like O2, Hormones and CO2 diffuse through. They actively transport metabolic products (like glucose) across the barrier necessary for brain fx.
Telencephalon Region
aka Cerebrum–Cerebral Hemispheres that are separated by a deep midline sagittal fissure. In the depth of this fissure lies the corpus callosum with is the bridge between L & R hemispheres. A 2nd horizontal fold of the dura mater (tentorium cerebelli) separates these hemispheres from the cerebellum.
Corpus Callosum
“tough body” in latin
Wide body of neural fibers that connect the cerebral hemispheres
facilitates the inter-hemispheric communication
-largest white matter structure of the brain
200-250 axonal projections
Gyri
the folds of the cerebral landscape with increase the surface area of the cerebral hemispheres they are separated from each other by small and large grooves
Sulci
small grooves that separate the gyri
Fissures
large grooves that separate the gyri
Functions of the Frontal Lobe
Executive Functions involving the ability to recognize:
-consequences resulting from current actions
-choosing between good and bad actions
-override and suppress unacceptable social responses
- determine similarities and differences between things or events
Involved in higher mental fx’s like: social interactions, functional movement, and verbal expression or languages
Broca’s area of the brain
Located in the frontal & parietal/temporal lobes
-production of languages have been linked to this area since Broca reported impairments in 2 patients who lost their ability to speak after injury to the posterior inferior frontal gyrus on the brain
Broca’s Aphasia vs Aphasia
Broca’s aphasia= deficit in language production, they know what they want to say but they can’t get it out
Aphasia= a language disorder that affects all modalities, reading, writing, speaking and listening, as a result of brain damage. A chronic condition affecting all areas of one’s life.
Age at which the frontal lobe reaches full maturity and whats associated with this?
Mid 20’s, this marks the cognitive maturity associated with adulthood
Pre-motor cortex functions
planning actions (in concert with basal ganglia) refining movements (with sensory input front he cerebellum)
What types of info must be received for the motor cortex to carry out goal-directed movements?
- info about body’s position in space (from parietal lobe)
- info about the goal to be attained and an appropriate strategy for attaining it (from anterior part of frontal lobe)
- info about memories of past strategies (from temporal lobe)
Basal Ganglia & their fx’s
A set of neural structures buried deep in cerebrum (caudate nucleus and globus pallidus)
- tightly interconnected to receive info from several diff. regions of the cerebral cortex.
- they process this info and return it to motor cortex via thalamus
- one likely fx of this loop is to select and initiate well coordinated voluntary movements, this is damaged in patients with diseases like parkinson’s)
Fx’s of the cerebellum
It is the internal “clock” which precisely regulates the sequence and duration of elementary movements. It refines movements to ensure they are smooth. When it is impaired you will see clumsiness and balance problems. It receives the info about intended movement from sensory and motor cortex and sends back the info about required direction, force and duration of movement to motor cortex.
Parietal Lobe Fx’s
Integrating sensory info from various parts of the body
- knowledge of numbers & their relations
- manipulations of objects
- visuospatial processing (comprehending visual representations and their spacial relationships)
Temporal Lobe Fx’s
- Superior temporal gyrus includes an area where auditory signals from the cochlea first reach the cerebral cortex (this is the primary auditory cortex involved in hearing)
- the adjacent parts superior, posterior and lateral are involved in high level auditory processing
- including speech(left temporal lobe)
- Wernicke’s area spans between temporal and parietal lobes and plays a key role in tandem with Broca’s area
- left temporal fx’s include low level perception, comprehension, naming and other language fx’s
- underside (ventral) is involved with high level visual processing (faces and scenes, anterior=object perception and recognition)
- medial involved in episodic and declarative memory
Fx’s of hippocampi deep inside temporal lobe
- essential for memory fx
- particularly the transference from short to long term memory
- control of spacial memory and behavior
- damage in this area results in anterograde amnesia or loss of ability to form new memories
Occipital Lobe Fx’s
visual processing center of the brain (it contains most of the visual cortex–there is some in each hemisphere of the brain) Left receives signal from right visual field and right hemisphere from the left visual field.
Agraphia
neural disorder affecting a person’s ability to write and spell
-due to injury or lesions in multiple lobes
Agnosia
loss of ability to recognize objects, person, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss
Diencephalon
- complex structure that serves to process all sensory input to the cortex (except olfactory)
- profound influence on motor control and cognitive fx
- known as interbrain, it is located beneath the cerebral hemispheres
- the part of the forebrain that contains: thalamus, hypothalamus, pineal gland and portions of the pituitary gland and limbic system
Limbic System
Complex set of brain structures that lies on both sides of the thalamus, right under cerebrum
- not a separate system but a collection of structures from telencephalon, diencephalon, and mesencephalon
- it includes the hippocampus, amygdala, anterior thalamic nuclei, septum and limbic cortex and fornix.
Limbic Systems Involvement in Emotions and Motivations
Those related to survival in particular. Fear, anger, social interactions, sexual behavior, pleasure.
Memory=Pain or Pleasure
-amygdala and hippocampus play important roles in memory
-amygdala=choses what memories are stored and where
based on the emotional response invoked by an event
-hippocampus=sends important memories out to appropriate part of cerebral hemisphere for long term storage and retrieves them when necessary. Damage here can result in inability to form new memories
Amygdala
emotional reactions
cingulate gyrus
links motivation and behavioral outcomes
fornix
bundle of axons
hippocampus
memory indexer (where to put memories)
hypothalamus
regulates hormones for vital fx’s
pituitary gland
regulates homeostasis including growth and bp
pineal gland
produces melatonin and modulation of sleep
thalamus
regulates motor fx’s
Thalamic Astasia
unable to maintain independent upright postural control and tends to fall backward or toward the side (contralateral to lesion)
-cant find a balance point
Effects of Drugs and Alcohol on the Brain
They disrupt the brain’s tools for judgment in the short term, but also with the long term developmental process, especially in teens. Their brains have not yet finished making the connections to fx like an adult until their mid20’s, signals from their primal emotions are still getting the upper hand and alcohol can interfere with the final round of organization and development of these connections that are necessary for the next 80 years of their lives.
Dopamine
neurotransmitter that helps control the brain’s reward and pleasure centers.
- helps regulate the movement and emotional responses, ability to see rewards and take action to move towards them
- dopamine def results in parkinson’s disease, and are more likely to be prone to addiction
- in teens their reward system (excess dopamine) is hyperactive affecting their decision making process
Clinical Depression
described as feeling sad, blue, unhappy, miserable or down in the dumps
TRUE clinical depression is a mood disorder–feelings of sadness, loss anger, or frustration interfere with everyday life for a period of time.
- demonstrated for at least 2 weeks of depressed mood or loss of interest inline activities along with 4 other characteristic symptoms
-exact cause unknown
Teen vs Adult Depression
Symptoms more common in Teens:
-irritable or angry mood (rather than sadness) is often the predominate mood; grumpy, hostile, easily frustrated, or prone to angry outbursts
-unexplainable aches and pains (headaches or stomachaches)
-extreme sensitivity to criticism, feelings of worthlessness
-withdraw from certain people: socialize less, pull away from parents, hang out with a different crowd
Adults:
-sadness predominant
-isolate
-loss of interest in activities
Facts of Teens and Alcohol/Drug use
- 72% of students have consumed alcohol by the end of high school
- 37% consumed alcohol by the end of 8th grade
- 32% of all traffic related deaths are accounted by teen alcohol impaired MVA’s
- MVA’s are the leading cause of death for 15-20 year olds
Structures and Fx’s that make up the brain stem
Mesencephalon (midbrain)
Pons
Medulla Oblongata
Neurological fx’s necessary for: survival (breathing, digestions, heart rate, bp), arousal (being awake and alert), and reward
-most cranial nerves come from the brain stem
Substantia Nigra
latin for black substance
- appear darker than neighboring areas due to high levels of melanin in dopaminergic neurons (require dopamine to fx normally)
- play important role in: reward, addiction and movement
- part of basal ganglia–mesencephalic gray matter portion
Basal Ganglia Role
needed for motor control, but also involved in the control of behavior, at the level of MOTIVATION, Parkinson’s disease involves this degenerating
Pons
latin word for “bridge”, located on brain stem
between midbrain and medulla oblongata
-it is the bridge that links different parts of the brain and serves as relay station from medulla oblongata to higher cortical structures of the brain
-origin of many cranial nerves
fx’s: respiration, swallowing, bladder control, shearing, equilibrium, taste, eye movement, facial expressions, facial sensation, posture, sleep
Medulla Oblongata
lower half of the brain stem, part of relay station for the crossing of motor tracts between spinal cord and brain
-controlling autonomic fx’s: respiration, cardiac center, vasomotor center, reflex center for vomit, cough, sneeze and swallowing.
Cerebellum
latin for “little brain”
important role in motor fx and in some cognitive fx’s (attention and language), also involved in some emotional fx’s (regulating fear and pleasure responses)
-motor relations are most clearly understood-coordination, precision and accurate timing, receives sensory info and uses it to fine tune motor activity
Ischemic Stroke
When blood vessel that supplies blood to the brain is blocked by a blood clot
- Thrombotic Stroke-when a clot (thrombus) forms in an artery that is already very narrow and completely blocks the artery.
- Embolic Stroke- when a clot from another place in the blood vessels of brain or other part of the body (embolism) breaks off and travels up to the brain to block a smaller artery.
- these are often from atherosclerosis-the hardening or narrowing of attires; fat, cholesterol and other substances can collect on the walls of arteries forming sticky plaque.
Hemorrhagic Stroke
blood vessel in part of the brain becomes weak and bursts open causing blood to leak into the brain and damages brain cells
Warning Signs of Strokes
- sudden numbness or weakness of face, armor leg, especial on one side of body
- sudden confusion, trouble speaking or understanding
- sudden trouble seeing in one or both eyes
- sudden trouble walking, dizziness, loss of balance or coordination
- sudden, severe headache with no know cause
Stroke in Cerebral Cortex impairments
aphasia, dysarthria, apraxia
Stroke in Cerebellum impairments
altered movement coordination, vertigo, disequilibrium
Stroke in Brain Stem impairments
breathing, heartbeat, taste, hearing, vision
How long can a stroke patient continue to improve
months or even years after the stroke
