Exam 2 Flashcards
The Brain and The Senses
Neuroaxis
Imaginary line running up from spinal cord to the front of the brain.
Rostral
Towards the beak (anterior)
Caudal
Towards the tail (posterior)
Dorsal
Top surface (superior)
Ventral
Bottom surface (inferior)
Lateral
towards the side (away from neuroaxis)
Medial
towards the midline (towards the neuroaxis)
Ipsilateral
Same side (e.g. smell)
Contralateral
Opposite side
Transverse Plane
Perpendicular to ground and neuroaxis (coronal; slice of bread; front and back)
Sagittal Plane
Parallel to neuroaxis (hot dog bun; left and right)
Horizontal plane
parallel to the ground (hamburger bun; top and bottom)
Cortex
Collection of neurons forming a thin sheet of cells (e.g. cerebral cortex)
Nucleus
Distinguished mass of neurons usually deep within the brain (e.g. lateral geniculate nucleus)
Locus
Small, well-defined group of neurons (e.g. locus coeruleus)
Ganglion
Collection of neurons in the posterior nervous system (save one in the CNS); e.g. basal ganglia
Commissure
Collection of axons that connect two sides of the brain (e.g. anterior commissure)
Nerve
Bundle of axons in the posterior nervous system (save one in the CNS); e.g. optic nerve
Neurocranium
8 bones of skull encasing the brain
Suture
Fibrous joint of skull bones
Bregma
intersection of coronal suture and sagittal suture (reference landmark)
Meninges
Three layers of tissue (dura matter, arachnoid membrane, and pia matter) encasing the brain
Sphenopalatine Ganglioneuralgia
Brain Freeze; headache caused by rapid presentation of cold foods to palate, which induces dilation of internal carotid artery and eventually pain in the meninges.
Cerebrospinal fluid (CSF)
Yellowish fluid containing salts and nutrients that bathes central nervous system
Produced by choroid plexus
Cushions that provide nutrients
Blood brain barrier
Mechanism inhibiting most chemicals and pathogens from entering the brain (capillary endothelial cellls more tightly packed with CNS)
Cerebral blood supply
brain recieves 20% of blood supply (750-1000 mL of blood/minute); 3 cerebral arteries: anterior, middle, posterior
Brain divisions
Forebrain, midbrain, hindbrain
Ventricular System
Series of hollow, interconnected chambers filled with CSF
Hindbrain main structures
Medulla Oblongata, pons, cerebellum
Medulla Oblongata
Role in cardiovascular function (heartbeat and blood pressure); gateway to the brain; area postrema
Pons
Role in sleep and arousal; locus coeruleus (noradrenergic {NE} system)
Cerebellum
Receives incoming sensory and outgoing motor information; coordinates signals
Midbrain structures
Superior colliculus, raphe nuclei, substantia nigra, midbrain nuclei
Superior Colliculus
Involved in visual reflexes and foveation
Raphe Nuclei
Origin of serotonergic system
Substantia Nigra
Origin of dopaminergic (DA) system
Midbrain nuclei
Origin of cholinergic (ACh) system
Forebrain main sites
Corpus Callosum, thalamus, hypothalamus, basal ganglia, limbic system, cerebral cortex
Corpus callosum
Large bundle of axons that connects with the cerebral hemispheres (split-brain operation)
Thalamus
Inner chamber; relay system (LGN –> vision); massa intermedia (thalamic commissure)
Hypothalamus
Controls ANS; survival behaviors (four F’s); numerous subdivisions (dorsal and ventromedial hypothalamus)
Basal Ganglia
Brian areas mediating movement; primary structures: caudate nucleus; putamen; globus pallidus
Limbic system
Brain areas associated with emotional processing (e.g. amygdala) and memory funtion (hippocampus)
Cerebral cortex
layer of unmyelinated neurons (gray matter); size and convolution vary greatly among species; nooks and cranies.
Your brain cannot compete with modern supercomputers
MYTH; human brains can process better and faster; computer cannot do two things at the same time; brain fits into small spaces and can process emotion, heal itself, and recognize smell.
You are left or right brained
MYTH; the hemispheres are more alike than different; lateralization of function (functional asymmetries between the two hemispheres)
Neurophilosophy
Field of philosophy of studying the mind and mental phenomena
Your brain has a map of the body
NOT A MYTH; Primary somatosensory cortex, primary motor cortex
Mind-Brain Problelm
Relationship that exists between mental processes and physical processes.
You have a brain to perform movement
Myth?!?! All behaviors are movement; much of the brain is dedicated to movement
Your brain stays active after you get decapacitated
Maybe a myth? Who knows??
Charlotte Corday (1768-1793)
Robert White (1926-2010) -
Dr. Frankenstein
Localization of Function
Principle that specific functions are mediated by circumscribed brain locations; we know this by human data: Phineas Gage, animal research, brain imaging.
Experimental ablation
Destroy (lesion) or remove area of brain and observe possible changes in behavior or performance
Aspiration
Remove tissue via pipette connected to vacuum pump
Subcortical Brian Lesions
Radiofrequency (RF) lesion, excitotoxic lesion, reversible lesion
Radiofrequency lesion
produced by heat generated from current passing through electrode; kills everything in the area
Excitotoxic lesion
produced by intracerebral injection of an excitatory animo acid (e.g. kainic acid); kills neurons, not axons
Cannula
Tube inserted into the brain
Reversible lesion
temporary disruption produced by injecting a local anesthetic
Sham lesion
“placebo” procedure duplicating all steps of producing a brain lesion except for the one that actually causes the brain damage
Stereotaxic surgery
Brain surgery using a stereotaxic apparatus to position an electrode or cannula in a specified position of the brain.
Medial Forebrain Bundle (MFB)
Fiber bundle that runs rostral-caudal direction through the forebrain and lateral hippocampus
Bregma
Junction of sagittal and coronal sutures of the skull; used as a reference point for stereotaxic surgery
Stereotaxic atlas
Collection of drawings of brain sections for a particular animal with measurements that provide coordinates for stereotaxic surgery (relative to the bregma)
Stereotaxic apparatus
device that permits a surgeon to position an electrode or cannula into a specific locus of the brain
Histological Techniques
Procedures used to examine anatomy of the tissue; brain tissue is fixed, sliced, and stained.
Neuronal Labeling
Method in which a dye is injected into the brain, absorbed by neurons and transported within the cell; anterograde vs retrograde
Cerebrovascular accident
Accident, such as stoke, causing damage to cerebral blood flow
Stroke
Sudden appearance of a neurological deficit due to disruption in cerebral blood supply (aka CVA); 3rd leading cause of death in the U.S.
Modifiable Risk Factors of Stroke
Smoking, alcohol, weight
Unmodifiable Risk Factors of Stroke
Genes, age, male
2 Types of Strokes
Ischemic and Hemorrhagic
Ischemic Stroke
Death of brain tissue (cerebral infraction) due to inadequate supply of blood and oxygen because of a blockage; incidence = 80%; mortality = 40%
Thrombotic stroke and embolic stroke
Atherosclerosis
Condition characterized by a build up of plaque (lipid material covered with fibrous tissue) embedded in the artery wall.
Thrombotic Stroke
Blood flow reduction due to atherosclerosis in cerebral blood vessel that eventually occludes it (50% of all strokes)
Embolic Stroke
Reduction of blood flow when an embolus travels to cerebral artery and forms a plug (30% of all strokes)
Hemorrhagic stroke
Loss of blood flow when cerebral blood vessel ruptures
Incidence = 20%; mortality = 80%
Edema
Accumulation of fluid; congestion, flat gyri, narrow sucli
Cerebral Aneurysm
Dilation or swelling of cerebral blood vessel due to weakness in vessel wall; congenital vascular malformation or hypertension
Umbra
area of tissue death from CVA (Ischemic core)
Penumbra
Region surrounding immediate damage; cells survive at least temporarily after stroke
Neuroplasticity
Altering or modification of neurons, their network, or their function due to experience (or trauma)
Regrowth of axons
PNS - 1 mm per day
CNS - 1-2 mm max
Synkinesis
involuntary movement accompanying a voluntary one due to miswiring of nerves following trauma.
Collateral Sprouting
Newly formed branch by uninjured axon to replace synapses vacated by injured neuron; sometimes useful, sometimes useless.
Reorganization of representations
E.g. Somatosensory cortex after amputation; visual cortex after blindness
Kennard Principle
Maxim suggesting that the earlier in life damage occurs, the better the recovery (Margaret Kennard)
Extraocular Muscles
Six muscles that mediate movement of the eye (plus a seventh that moves the eyelid)
Micronystagmus
Undetectable movement of the eye.
Sclera
Tough, outermost coat of the eyeball comprised of densely packed fibers (white of the eye)
Cornea
Transparent, dome-shaped element covering front of eyeball that refracts (i.e. focuses) light toward posterior eyeball. (~80% of the eye’s optical power)
Iris
Pigmented muscular membrane that dilates and constricts to regulate amount of light entering through the pupil. (eye color; controlled by autonomic nervous system)
Lens
elliptical optical element that refracts light towards back of eyeball (20% of optical power)
Emetropia
Ideal focus of image on back of the eyeball (20/20 vision)
Myopia
Image focus in the front of the retina
Hyperopia
Image focus behind the retina
Vitreous Humor
Maintains Intraocular pressure; holds retina down
Retina
Photosensitive tissue lining posterior of eyeball consisting of interconnected nerve cells, including photo receptors (rods and cones)
Fovea
Fixation locus
Optic disk
Location where ganglion cell axons converge and exit the eyeball (starting the optic nerve); devoid of photoreceptors; aka “blindspot”
Photoreceptors
Sensory neurons that absorb and transduce light energy into a neutral signal
Rods (100 M) and cones (25 M)!!
Photopigments
light-absorbing molecule embedded in a membrane disk (rod) or a membrane fold (cone) in the outer segment
4 Types of Photopigments (3 cones and 1 rod)
Visible spectrum
~400-700 nm
Trichromacy vs dichromacy
Trichromacy - 3 cones
Dichromacy - 2 cones
Light Absorption…
- Causes physical change in the photopigment
- Activates a second messenger (transducin) that closes NA+ channels
- Hyper-polarization of membrane potential
- Stops release of neurotransmitter
- Depolarizes membrane of bipolar cells
- Action potential(s) in ganglion cell
Optic Nerve
Bundle of about 1 million ganglion cell axons that conveys visual signals to receptors of the brain; start of the visual pathway.
Optic Chiasm
Region where fibers serving nasal retinae cross over; contralateral processing
Acromegaly
Endocrine disorder in which pituitary gland overproduces the growth hormone; enlarged hands, feet, and facial features, coarse and oily skin, muscle weakness, and painful mobility, skin tags, and excessive sweating.
- e.g. Andre the Giant
Most commonly caused by a benign tumor in the pituitary gland
Diplopia
Double vision
Bitemporal Hemianopia
Blindness in outer half of visual fields.
Lateral Geniculate Nucleus
Thalamic structure where ~90% of ganglion axons project
Other 10% of visual signals:
Super colliculus
Superchiasmatic nucleus
- sleep and body temp; hypothalamus structure
Edinger-Westphal Nucleus
- midbrain cell group mediating pupillary light reflex
Primary Visual Cortex
Cortex along calcarine fissure that recieves visual input from retina via LGN (aka Area V1 and striate cortex)
Retinotropic map
Spacial arrangement of cells that corresponds or aligns to retinal cell arrangement.
Feature detectors
neurons that respond selectively to specific features of a stimulus
David Hubel and Torsten Wiesel
Presented spots of light to a cat and measured action potentials
Discovered:
- Simple Cells
- Complex Cells
Simple cells
In primary visual cortex; respond to lines of a particular orientation; arranged in columns
Complex cells
In primary visual cortex; respond to moving stimuli (lines); specific orientation moving in particular direction
Extra striate cortex
areas of cortex that process visual signals beyond V1
V3, V4, and V5
Visual Agnosia
Rare neurological condition in which an individual cannot perceive or recognized some aspect of a visual scene
Apperceptive visual agnosia
Failure to perceive objects (forms) despite normal acuity; damage to area V3; difficulty distinguishing between apple and strawberry
Cerebral Achromatopsia
Inability to discriminate different colors (damage to area V4)
Akinetopsia
Inability to determine velocity or direction of movement; motion agnosia; damage to area V5; e.g. running water looks frozen.
Binding problem
Problem of how neural activity in separated areas of the brain is combined to create a coherent perception; e.g. rolling yellow ball (form in V3, color in V4, motion in V5) perception happens almost instantly.
Kinetosis
Transient, deliberating condition characterized by dizziness, vertigo and nausea
Motion Sickness!!
Treatments for kinetosis
View horizon and anticipate movements
Move to center axis of vehicle
Full stomach?
Antimetics (ACh antagonists, e.g. dimenhydrinate)
Vestibular system
3 organs: saccule, utricle, and semicircular canals
Adjacent to inner ear that mediate posture, balance, and sense of orientation
Otolith Organs
2 fluid filled sacs (organs) that register gravity plus vertical (saccule) or horizontal (utricle) movement.
Otoliths
calcium particles suspended in endolymph - inner ear fluid
Macula
Patch of receptive tissue
Saccule ~19 K hair cells on the wall (vertical)
Utricle ~ 33 K hair cells on the floor (horizontal)
Otolith Organs process (motion sickness)
- Weight causes endolymph to move as head orientation changes
- Movement produces shearing force on cilia
- Bending of cilia affects release of neurotransmitters
Semicircular canals
3 fluid-flled toroidal tubes that lie above the inner ear at right angles to each other and register rotary motion of head
3-coordinate system: roll, pitch (yes), yaw (no)
Cupula
Tongue shaped gelatinous mass in ampula (spherical arrangement) containing tufts of hair from vestibular nerve
Sways in response to flow of endolymph; affected by inertia of endolymph (like water in a glass)
Capula displacement causes increase or decrease in action potentials
Vestibular Nerve
Part of vestibulocochlear nerve (cranial nerve VIII) conveying vestibular signal to the brain.
Medulla and cerebellum (no exclusive primary cortex)
Oculomotor nucleus
Group of midbrain cells that mediate eye movements, relative to head position and movement (Edinger-Westphal Nucleus)
Vestibulo-Ocular Reflex (VOR)
Reflexive eye movement initiated when the head or body moves to stabilize position of the eyes relative to a target
Compensates for jarring from walking to running to heartbeat and breathing
Vestibular system’s function is to serve visual system in motion!
Caloric Reflex Test
VOR test for nystagmus (involuntary eye movement) induced by irrigating auditory canal with cold or warm water.
Test integrity of the brain stem and vestibular system in unconscious patient
COWS: cold opposite, warm same
Sensory Conflict Theory
Periods of unusual passive motion cause disruption of the usual close correspondence between visual system and vestibular system concerning spacial orientation
Vestibular input DOES NOT equal visual input
Result is motion sickness
Vomiting Center
Cell groups in dorsal-lateral medulla that mediate vomiting reflex
Cerebellum (mismatch between vision and vestibular sense) –> chemoreceptor trigger zone –> vomiting center
