Chapter 3: Anatomy and Research Methods Flashcards
Neuroanatomy
anatomy of nervous system
Central nervous system
brain and spinal cord
Peripheral nervous system
controls brain and spinal cord to rest of body. Includes:
1. Somatic: controls voluntary muscles and conveys sensory info to the central nervous system
2. Autonomic: controls involuntary muscles
a. Sympathetic: expends energy
b. Parasympathetic: conserves energy
What does somatic nervous system do
consists of axons conveying messages from sense organs to CNS, and CNS to muscles
What does autonomic nervous system do
controls heart, intestines and other organs (has some cell bodies in brain and spinal cord)
Dorsal
Towards the top
Ventral
Towards the stomach
3 planes of the brain
horizontal, sagittal, and coronal
anterior
Toward the front
posterior
toward the back
Superior
Above another part
Inferior
Below another part
Lateral
toward the side
Medial
Toward the middle/midline
proximal
located close to the point of origin/attachment
distal
more distant to the point of origin/attachment
ipsilateral
Same side of body
contralateral
opposite side of body
coronal plane
brain structures as seen from the front
Sagittal plane
shows brain structures as seen from the side
horizontal plane
Shows brain structure from above
Lamina
row or layer of cell bodies separated from other cell bodies by a layer of axons and dendrites
Column
set of cells perpendicular to the surface of the cortex, with similar properties
tract
A set of axons within the CNS, also known as a projection. If axons extend from cell bodies in structure A to synapses onto B, we say that the fibers “project” from A onto B.
Nerve
A set of axons in the periphery, either from the CNS to a muscle or gland or from a sensory organ to the CNS
nucleus
A cluster of neuron cell bodies within the CNS
Ganglion
A cluster of neuron cell bodies, usually outside the CNS (as in the sympathetic nervous system)
sulcus
A fold or groove that separates one gyrus from another
gyrus
A protuberance on the surface of the brain
Fissure
Long, deep sulcus
Spinal cord
communicates w/ all sense organs and muscles except those of the head. Has sensory nerve and motor nerve
Dorsal root ganglia
cell bodies of sensory neurons in clusters of neurons outside spinal cord. Neuron cluster outside CNS is ganglion, cluster inside CNS called a nucleus
gray matter
packed w/ cell bodies and dendrites, send axons to brain or other parts of spinal cord through white matter, containing myelinated axons
What does spinal cord do
Each segment of spinal cord sends sensory info to brain and receives motor commands from brain. Info passes through tracts of axons in spinal cord
What does sympathetic nervous system do?
prepares organs for burst of vigorous activity. Consists of chains of ganglia to left and right of spinal cord’s central regions (thoracic and lumbar). Prepares axons for fight or flight. Act as single unit, in sympathy with one another
What does parasympathetic nervous system do
rest and digest system. Opposite function of sympathetic nervous system
preganglionic axons and postganglionic fibers
Unlike the ganglia in the sympathetic system, the parasympathetic ganglia are not arranged in a chain near the spinal cord. Rather, long preganglionic axons extend from the spinal cord to parasympathetic ganglia close to each internal organ. Shorter postganglionic fibers then extend from the parasympathetic ganglia into the organs themselves. Because the para- sympathetic ganglia are not linked to one another, they act more independently than the sympathetic ganglia do. Para- sympathetic activity decreases heart rate, increases digestive rate, and in general, conserves energy.
Do the two systems use the same transmitters
Two systems use different transmitters, certain drugs excite or inhibit one system or the other
what are the 3 major divisions of brain
hind brain, mid brain, fore brain
hind brain
posterior part of brain, consists of medulla, pons, and cerebellum. Constitute brainstem.
cranial nerves
- Olfactory: Smell
- Optic: Vision
- Oculomotor: Control of eye movements; pupil constriction
- Trochlear: Control of eye movements
- Trigeminal: Skin sensations from most of the face; control of jaw muscles for chewing and swallowing
- Abducens: Control of eye movements
- Facial: Taste from the anterior two thirds of the tongue; control of facial expressions, crying, salivation, and dilation of the head’s blood vessels
- Statoacoustic: Hearing; equilibrium
- Glossopharyngeal: Taste and other sensations from throat and posterior third of the tongue; control of swallowing, salivation, throat movements during speech
- Vagus: Sensations from neck and thorax; control of throat, esophagus, and larynx; parasympathetic nerves to stomach, intestines, and other organs
- Accessory: Control of neck and shoulder movements
- Hypoglossal: Control of muscles of the tongue
Medulla
enlarged extension of spinal cord
cranial nerves
Control reflexes
pons
bridge, allows for axons from each half of brain to cross to opposite side of the spinal cord, leads to left hemisphere controlling right side of body and vice versa
cerebellum
important for balance, coordination, shifting attention, learning and conditioning
Mid brain
roof is called tectum. Swelling on each side are superior colliculus and inferior colliculus. Both important for sensory processing. Tegmentum covers midbrain structures. Substantia nigra facilitates dopamine containing pathway that facilitates readiness for movement
Forebrain
2 cerebral hemispheres. Each hemisphere receives sensory info from opposite side of body. Controls movement of opposite side of body
Cerebral cortex
Outer portion. is a Latin word for “bark” or “shell.”) Under the cerebral cortex are other structures, includ- ing the thalamus and the basal gan- glia. Several interlinked structures, known as the limbic system, form a border (or limbus, the Latin word for “border”) around the brainstem.
Limbic systems
Forms border around brainstem. Includes the olfactory bulb, hypothalamus, hippocampus, amygdala, and cingulate gyrus of the cerebral cortex
amygdala
part of the circuit that is most central for evaluating emotional information, especially with regard to fear
Thalamus
pair of structures in center of forebrain. Processes most sensory info. Sends output to the cerebral cortex
hypothalamus
Essential for control of eating/drinking, temperature, reproductive behavior. Near base of brain. Conveys messages to pituitary gland, altering release of hormones. Main source of input to the cerebral cortex. Damage to this area leads to abnormalities in motivated behaviors
pituitary gland
hormone producing gland attached to hypothalamus
basal ganglia
includes 3 structures; caudate nucleus, globus pallidus, putamen. Integrates motivational and emotional behavior to increase vigor of selected activities. Related to movement, learned habits
Basal forebrain
nucleus basalts. receives input from hypothalamus and basal ganglia. Sends axons that release acetylcholine. Important for arousal
Hippocampus
critical for certain types of memory (especially episodic memory). Important for monitoring where you are/where you are going
Ventricles
four fluid filled cavities in brain. Have choroid plexus, which produce cerebrospinal fluid (CSF). CSF goes to center canal of spinal cord, but more goes to meninges, membrane that surrounds brain and spinal cord. CSF cushions brain against mechanical shock when head moves and supports weight of brain. Provides reservoir of hormones and nutrition for brain and spinal cord
Cerebral cortex
cells on outer surface are gray matter, axons extending inward are white matter
meninges
membranes that surround the brain and spinal cord. In one of those narrow spaces, the subarachnoid space, the blood gradually reabsorbs the CSF. Although the brain has no pain receptors, the meninges do, and meningitis—inflammation of the meninges—is painful. Swollen blood vessels in the meninges are responsible for the pain of a migraine headache
Corpus callosum and anterior commissure
two bundles of axons which allow for communication of 2 hemispheres in cerebral cortex
Primate cerebral cortex
larger cerebral cortex, more folding, and more neurons per unit of volume when compared to other mammals
How many laminae do humans and other mammals have?
6 layers: cell bodies that are parallel to surface of the cortex and separated from each other by layers of fibers (P83). Vary in thickness and prominence from one part of cortex to another
1. Molecular layer: Mostly dendrites and long axons
2. External granular layer: Small pyramidal cells
3. Pyramidal layer cells: pyramidal cells
4. internal granular layer: Small cells; main site for incoming sensory information
5. Inner pyramidal layer: Large pyramidal cells; main source of motor output
6. multiform layer: spindle cells
4 layers of cerebral cortex
- Occipital
- Parietal
- Temporal
- Frontal
Occipital
Vision. posterior end of cortex. Main target for visual info. Striate cortex, primary visual cortex. Eyes provide the stimulus and occipital cortex provides visual experience
Parietal
Touch. body sensations. Postcentral gyrus has 4 representations of the body. b/w occipital lobe and central sulcus (deep groove in surface of cortex). Postcentral gyrus is primary somatosensory cortex, receives sensations from touch receptors, muscle-stretch receptors and joint receptors. Has 4 bands which receive sensory input from varying levels of touch/pressure. Parietal lobe monitors info related to spatial stimuli and numerical
Temporal
Hearing and complex aspects of vision, processing emotional info portion of hemisphere, near temples. Primary target area for auditory info. Left temporal important for spoken language. Also assists with vision (movement and faces). Often over stimulated when individuals report hallucinations. Important for emotional and motivational behaviors. Damage can lead to Kluver-Bucy syndrome.
frontal
includes precentral gyrus, controls fine movements. Includes prefrontal cortex, responsible for planning actions, working memory, certain aspects of emotion and decision making. primary motor cortex and prefrontal cortex, extends from central sulcus to anterior limit of brain. Precentral gyrus, posterior portion of frontal lobe, specialized for control of fine movements like moving a finger
Where is prefrontal cortex
Most anterior portion of frontal lobe
Regions of prefrontal cortex
- Posterior: associated with movement
- Middle zone: working memory, cognitive control, emotional reactions
- Anterior zone: Making decisions, evaluate which of several courses of actions is likely to lead to best outcome
Binding problem: large scale integration problem
How do various brain areas produce a perception of a single object?Binding caused by perceiving two sensations as happening at same time and approximately same place
primary function of cerebral cortex
elaborating sensory info and organizing sequences of behaviors
How is cortex organized
Cortex organized into columns of cells arranged perpendicular to laminae
Methods of relating brain structure to function
- Examine effects of brain damage: Limitation-few people have brain damage confined to one brain area
- Examine effects of stimulating a brain area
- Record brain activity during behavior
- Correlate brain anatomy w/ behavior (P91)
Ablation
removal of brain area w/ a surgical knife
Lesion
damage made into brain using stereotaxic instrument to explore tiny structures underneath surface of brain (using stereotaxic instrument)
Sham lesion
used in control group to ensure procedure doesn’t cause change in behavior
What else is used to cause brain damage to be observed?
Electric lesion crude technique rarely used. Instead might use chemical that kills neurons or disables them temporarily. Can also inject chemical that disables particular type of synapse. Gene-knockout approach another option, which directs a mutation to a gene that regulates one type of cell, transmitter or receptor
Transcranial magnetic stimulation
Application of magnetic stimulation to a portion of scalp, can stimulate neurons in the area below the magnet, if stimulation is sufficiently brief and mild. Strong stimulation inactivates neurons and produces virtual lesion
optogenetics
using light to control limited pop of neurons. Requires 3 steps:
1. Discover/invent protein that responds to light by producing electrical current. Certain microbes do produce such proteins, which researchers have found ways to modify . One protein reacts to light by opening a sodium channel, exciting the neuron, and another reacts by opening a chloride channel, producing inhibition
2. Develop viruses that insert one of these proteins into a certain type of neuron, or one part of neuron, such as axon or dendrites
3. Develop thin optical fibers that can shine right amount of light onto neurons in a narrowly targeted brain area
electroencephalograph (EEG)
records electrical activity of brain through electrodes. Measure activity at any given moment for pop of cells under electrode. Useful for wakefulness and various stages of sleep. Same device can record brain activity in response to stimulus, called evoked potentials/responses.
magnetoencephalography
measures faint magnetic fields generated by brain activity
Positron-emission tomography (PET)
high resolution image of activity in living brain by recording emission of radioactivity from injected chemicals. fMRI used as replacement to PET (functional magnetic resonance imaging. fMRI detects amount of hemoglobin w/ oxygen
When brain area becomes more active, what changes occur?
- Blood vessels dilate to allow more blood flow to area (P94-95)
- As brain uses more oxygen, percentage of hemoglobin w/ oxygen decreases (P95). Based on comparison of brain activity during activity of interest and other activity
Computerized axial tomography (CAT scan)
used to examine detailed brain anatomy in living people (P96), Helps detect structural abnormalities
MRI: Magnetic Resonance Imaging
Forms image of the brain
How to study effects of brain damage
- lesion
- ablation,
- gene knockout approach
- transcranial magnetic stimulation
Examine effects of stimulating a brain area
- stimulating electrodes: Invasive; used with laboratory animals, rarely with humans
- Optogenetic stimulation: Mostly with laboratory animals; can indicate function of a particular type of cell
Record brain activity during behavior
- Record from electrodes in the brain: Invasive; used with laboratory animals, rarely with humans
- Electroencephalograph: Records from scalp; measures changes by milliseconds, but with low resolution of location of the signal
- Evoked potentials: Similar to EEG but in response to stimuli
- Magnetoencephalograph (MEG)
Similar to EEG but measures magnetic fields - Positron Emission Topography (PET): Measures changes over both time and location but requires exposing brain to radiation
- Functional magnetic resonance imaging (fMRI): Measures changes over about 1 second, identifies location within 1 to 2 mm
Correlate brain activity with behavior
- Computerized axial tomography (CAT): Maps brain areas, but requires exposure to X-rays
- Magnetic resonance imaging: Maps brain areas in detail, using magnetic fields
Haemodynamic
study of how blood flows through cardiovascular system
principles of fMRI
- Noninvasive
- Availability increasing
- High spatiotemporal resolution
- Capacity to demonstrate entire network of brain areas engaged when subjects undertake particular tasks
Disadvantages of fMRI
Measures surrogate signal whose spatial specificity and temporal response are subject to both physical and biological constraints
Limitations due to mass action and not hardware or acquisition methods
fMRI excellent tool for formulating intelligent, data-based hypotheses, but only in certain cases can it be really useful for selecting one of them, or for explaining detailed neural mechanism underlying studied cognitive capacities* Combo of fMRI and other techniques will be most effective for understanding brain function
BOLD: Blood oxygen level dependent
allows for effectiveness of neuroimaging
Signal specificity
ensures that maps generated reflect actual neural changes
spatial temporal resolution
determine our ability to discern elementary units of activated networks and the time course of various neural events. Spatiotemporal resolution likely to increase w/ optimization of pulse sequences, improvement of resonators, application of high magnetic fields, invention of intelligent strategies such as parallel imaging
Feedforward and feedback cortical processing
bottom up and top down
Microcircuits
- final response of each neuron determined by all feedforward, feedback and modulatory synapses
- transient excitatory responses may result from leading excitation
- net excitation/inhibition might occur when afferents drive overall inhibition-excitation balance in opposite directions
- responses to large sustained input changes may occur while maintaining well balanced excitation-inhibition
What alters fMRI signaling
changes in excitation-inhibition balance affect the regional metabolic energy demands and the concomitant regulation of cerebral blood flow
