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Describe the evolution of the brain.
- Embryonic development -> forebrain, midbrain, hindbrain
- forebrain -> telencephalon (cerebrum), diencephalon (thalamus & hypothalamus)
- midbrain -> mesencephalon (contains the corpora quadrigemina)
- hindbrain -> metencephalon (pons & cerebellum), myelencephalon (medulla oblongata)
Describe the matter composition of the brain.
- Cerebral cortex (outer surface) – gray matter (cell bodies and dendrites)
- inner surface – white matter (myelenated axons)
Describe meninges function and meninges structure
- Meninges function as layers of protection for the brain
- Structure of the meninges (from the inside out) – pia mater, arachnoid mater, dura mater
- Subarachnoid space (between arachnoid mater and pia mater) houses CSF
Describe the ventricles of the brain (function and structure)
- Ventricles are spaces inside the brain that contain CSF
- lateral ventricles (2), 3rd ventricle, and 4th ventricle.
Describe the flow of CSF through the brain
Continuous flow of CSF from lateral ventricles -> 3rd ventricle -> cerebral aqueduct -> 4th ventricle -> subarachnoid space -> reabsorption
General functions of the cerebrum
Sensory perception, motor control, language, emotion, memory
General information about the cerebrum
80% of total brain mass, corpus callosum (tract of axons) connects left and right hemispheres
Convolutions vs. sulci vs. gyri
- Convolutions – folds and grooves on the cerebral cortex
- Sulci – deep grooves on the cerebral cortex
- Gyri – high ridges on the cerebral cortex
Lobes of the cerebrum?
- Frontal, parietal, temporal, occipital
- Every lobe has left and right portion to correspond with the brain hemispheres
Major landmarks of the cerebrum? What do they define?
- Lateral fissure – separates the temporal lobe from the parietal and frontal
- Central sulcus – separates frontal lobe and parietal lobe
- Longitudinal fissure – separates right and left hemispheres of the brain
- Parieto-occipital sulcus - separates parietal lobe and occipital lobe
Frontal lobe structures with functions
- Primary motor cortex – located on the precentral gyrus, controls voluntary movement of skeletal muscle (concious control)
- Premotor cortex – anterior to precentral gyrus - coordinates multiple muscles used in a single movement, sends signal to primary motor cortex for execution
- Prefrontal area – anterior to precentral gyrus - complex cognitive functions/planning decision making/personality
- Broca’s area – (left only) inferior frontal lobe - motor speech control
Parietal lobe structures with functions
- Primary somatosensory cortex – located on the postcentral gyrus - all somesthetic senses are directed here (touch, pressure, heat, cold, pain) (concious recognition of stimulus)
- Somatosensory association cortex – posterior to postcentral gyrus - multimodal integration (ties together multiple senses), sensory memory. Allows you to “remember” all the attributes of an item (weight, color, smell) just from the way it feels in your pocket
Temporal lobe structures with function
Primary and association auditory cortex – perception and interpretation of all auditory information from the ear
Occipital lobe structures with function
- Primary and association auditory cortex – pereception and interpretation of all visual images from the eye
- Association area is what gives us 3D perception and what is responsible for response to optical illusions
Right hemisphere vs. left hemisphere specializations
- Right hemisphere – spatial organization and music
- Left hemisphere – language and analytical ability
Two principle areas of language w/ location, function, and effects of damage
- Broca’s area – left inferior frontal lobe, controls complex fine-motor functions involved in speech (lips, tongue, etc). Damage leads to Broca’s aphasia (slow, poorly articulated speech & inability to convey thoughts)
- Wernicke’s area – left superior temporal lobe, responsible for ability to comprehend language and formulate words. Damage leads to Wernicke’s aphasia (inability to comprehend spoke/written language, inability to coherently assemble words)
EEG name, setup, measures what, meaning?
- Noninvasive, electrodes in contact with the surface of the scalp detect differences in potential as compared to a reference electrode.
- Measures summed postsynaptic potentials (not APs) from numerous pyramidal neurons’ dendritic trees.
- Meaning unknown
Describe asynchronous brainwaves
High frequency, low amplitude. Results from numerous EPSPs and IPSPs cancelling each other out
What produces low amplitude brainwaves?
Either low activity or asynchronous activity (can’t differentiate between active/inactive brains)
What produces high amplitude brainwaves?
Synchronous activation (physiological significance unknown)
What significance does brainwave frequency have?
High frequency indicates alertness and low frequency indicates sleep
How can epileptic seizure brainwaves be characterized?
- Abnormal, highly synchronous EEGs
- -------*\/\/\/\/\/\ (*indicates start of seizure)
Brainwave activity during sleep cycles
REM/awake brainwave activity vs. NREM brainwave activity
- REM/awake brainwave activity has asynchronous waves (high frequency, low amplitude)
- NREM brainwave activity has synchronous waves (low frequency, high amplitude).
Other name for REM, why?
Paradoxical sleep, because the brainwaves are identical to awake brainwaves
Waking state brainwaves – resting vs. attentive
- Alpha rhythms occur with relaxed wakefulness, eyes closed. (frequency 8-12Hz). Synchronous.
- Beta rhythms occur with attention and concentration. (frequency > 13Hz). Asynchronous.
Limbic system components?
Cingulate Gyrus, Cerebral Nuclei (amygdala and hippocampus), and hypothalamus
Functions of limbic system w/ related structures
- Agression (amygdala)
- fear (amygdala and hypothalamus)
- sex drive (various areas + hypothalamus)
- goal-directed behavior (various areas + hypothalamus)
Where do most epileptic seizures begin
Ventral landmarks of the limbic system +what do they define? Medial landmarks?
- Ventral: The parahippocampal gyrus (superficial to the hippocampus), Uncus (medially projecting bump on the parahippocampal gyrus that is superficial to the amygdala)
- Medial: Cingulate gyrus (defines itself, can only be seen medially with a sagittal cut)
Two forms of memory w/ description and related structures
- Short term: <30 sec [hippocampus required for retention]
- Long term: >30 sec [stored in various regions (eg. Visual in temporal lobe, etc)]
- -Non-delcarative: memory of simple skills and conditioning (tying shoelaces)
- -Delcarative: memory of facts and events (memorizing all shoe models from a company)
What parts of the brain are involved in memory consolidation? What does it involve?
- Medial temporal lobes (contain amygdala and hippocampus) are involved in converting short-term memory in the hippocampus to long-term declarative memory in the cerebrum.
- Appears to involve changes in synaptic transmissions in specific neural pathways (especially in association cortices)
- Premotor area stores nondelcarative memories.
What is Alzheimer’s effect on the brain?
Degeneration begins in medial temporal lobes (hippocampal region), continues throughout brain over time (shrinking of gryi)
Describe the H.M. case study
Surgical destruction of the hippocampus caused partial retrograde amnesia. He was unable to form new episodic memories and could not remember events just before surgery, but retained memories from years earlier
Describe the motor circuit. Role of substantia nigra?
- Axons from the cerebral cortex synapse with basal nuclei and the cerebellum (via the pons). The basal nuclei send inhibitory signals to the thalamus. The cerebellum sends excitatory signals to the thalamus. The thalamus sends signals back to the motor cortex.
- The substantia nigra also synapses with the basal nuclei and partially controls their inhibition of the thalamus through dopamine release
What are the effects of the motor circuit?
To maintain purposeful motor activity while suppressing unwanted motor activity, and to monitor and coordinate slow sustained contractions
Parkinson’s effects on the brain? Temporary treatment? Physical effects?
- Damage to substantia nigra results in decreased dopamine to the basal ganglia.
- L-DOPA works as a temporary treatment.
- Effects on the body include tremors, shuffling walk, and absolute rigidity when sitting
Huntington’s effects on the brain? Temporary treatment? Physical effects?
- Damage to the basal ganglia (genetic).
- No treatment available.
- Results in uncontrolled movements
Structures of the diencephalon?
- Thalamus (80% of total diencephalon)
- part of the pituitary gland
- Receives and relays all sensory input (except olfaction) to the appropriate area of the cerebral cortex.
- Relays motor signals from the basal ganglia and cerebellum to the motor cortex
Hypothalamus functions? (categories & specific examples)
- Motivational behavior – hunger, thirst, body temperature, etc
- Emotion – anger, fear, pleasure (w/ amygdala)
- Neural control of pituitary hormone release
- Control of autonomic nervous system (sympathetic and parasympathetic)
- Control of circadian rhythms
How are circadian rhythms regulated?
Circadian rhythms are controlled by the suprachiasmatic nuclei (2) in the hypothalamus. These nuclei act as an internal clock, and are affected by daylight
Hypothalamus interaction with pituitary gland
- Posterior pituitary – ADH, oxytocin created by the hypothalamus, transported to posterior pituitary via axons. Release directly controlled by hypothalamus via neurons.
- Anterior pituitary – creates its own hormones. Release indirectly controlled by hypothalamus via hormones
What structures does the brainstem comprise?
Midbrain + hindbrain
Midbrain (mesencephalon) location?
Located between diencephalon and hindbrain
Nuclei of the midbrain + functions?
- Corpora quadrigemina – auditory path and visual reflexes
- Substantia nigra – nigrostriatal dopamine system (motor input to basal ganglia)
- Mesolimbic dopamine system – input to the nucleus accumbens (pleasure center) (goal-directed behavior)
- Cranial Nerves III-IV originate here
Corpa quadrigemini detailed visual reflexes vs. auditory pathway
- Superior colliculi (top 2 bumps) – visual reflexes (motor reflexes associated with vision)
- Inferior colliculi (bottom 2 bumps) – auditory pathway
- -when viewing from dorsal view of midbrain w/o cerebellum and cerebral cortex
Hindbrain (metencephalon) structures/functions?
- Pons – regulation of breathing, relay between cerebral cortex and cerebellum, contains cranial nerves V-VIII
- Cerebellum – proprioceptor input (sensors in muscles/tendons/joints), coordinates movements, maintains posture/balance, learned motor skills. Works with basal ganglia and the motor cortex. Important for learned motor skills. (Receives sensory input from many locations and has much ouput, although primary output to motor cortex)
Hindbrain (myelencephalon) structures/functions?
- Medulla oblongata – relay for ascending/decending pathways between brain and spinal cord (decussation for some pathways). Nuclei (reticular formation) control basic survival functions.
- Cranial nerves VIII-XII
Medulla oblongata nuclei + functions
- Cardiac center – regulates heartrate and contractive force of heart
- Respiratory center – regulates respiration
- Vasomotor center – controls blood vessel diameter and blood pressure
Reticular activating system (RAS) description
- RAS is an arousal system that is controlled by the reticular formation
- Determines the overall activity level of the brain
How does RAS work?
- RAS is activated by receipt of sensory information and induces nonspecific arousal to cerebrum (promotes wakefulness).
- RAS is inhibited by GABA-releasing neurons in the hypothalamus (decreases wakefulness).
Cranial nerve locations?
- Other I-II
- Midbrain III-IV
- Pons V-VIII
- Cerebellum VIII-XII
Function of spinal cord? Number of spinal nerves? Spinal nerves motor or sensory?
- To link the brain to most of the PNS.
- 31 pair of spinal nerves.
- Spinal nerves are “mixed nerves” because they have both motor and sensory fibers.
Role of spinal cord in spinal reflexes?
Spinal cord acts as an integrating center for spinal reflexes (reactions that occur without going to the brain)
Composition + structure of spinal cord. Protection?
- Outer surface – white matter (ascending/descending tracts of axons
- Interior – gray matter (cell bodies of motor and association neurons)
- Protected by the vertebral column and meninges.
How do spinal nerves join with spinal cord (detailed)?
- Spinal nerves join spinal cord through spinal nerve roots.
- dorsal root – carries afferent (sensory) axons into spinal cord
- -dorsal root ganglion – group of sensory (unipolar) cell bodies outside the spinal cord
- ventral root – carries efferent (motor) axons out of spinal cord to muscles/glands
Ascending tracts vs descending tracts? Examples (not detailed)? Organization?
- Ascending tracts carry sensory information from receptors to brain (spinothalamic tract, fine touch and proprioception pathway)
- Descending tracts carry motor information from brain to motor neurons (corticospinal (pyramidal) tract)
- All tracts are topographically organized by modality and location of receptors/effectors.
Spinothalamic tract detailed
- Three neuron pathway. Carries pain and temperature sensations from receptors to thalamus.
- First order neuron – sensory receptor for pain or temperature synapses with second order neuron in dorsal horn.
- Second order neuron – cell body in dorsal horn, axon crosses the spinal cord midline to the opposing anterolateral white matter (diagonally) and ascends the spinal cord toward the brain. Synapses with third order neuron in the contralateral thalamus (decussated in the spinal cord).
- Third order neuron – sends axon to appropriate area in primary somatosensory cortex
Fine touch and proprioception pathway detailed
- Three neuron pathway. Carries fine touch and proprioceptive information from receptors to thalamus. Receptors include muscle spindles and golgi tendon organs (limb position) and cutenous receptors (touch, pressure, vibration)
- First order neuron – sensory axons enter spinal cord through the dorsal root and ascend (ipsilaterally) through the posterior white matter (posterior funiculus) until synapsing with second order neuron in the medulla oblongata.
- Second order neuron – cell body in medulla oblangata, axons decussate and ascend in medial lemniscus (a tract), synapse with third order neuron in thalamus
- Third order neuron – cell body in the contralateral thalamus (decussated in medulla) sends axons to the appropriate location in the primary somatosensory cortex
Corticospinal (pyramidal) tract detailed
- Two neuron pathway. Carries response information from brain to skeletal muscle.
- Upper motor neuron (interneuron) – originates in motor cortex, decussates at medullary pyramids, synapses with lower motor neuron in spinal cord
- Lower motor neuron (motor neuron) – cell body in contralateral posterior horn (decussated in medulla), exits through posterior root and synapses with skeletal muscle.
How can you determine whether damage is to an upper motor neuron or lower motor neuron?
- The babinski sign (toes fan/big toe extends upward in response to sole stimulation) indicates upper motor neuron damage. Lower motor neuron damage would result in no response
- (babinkski sign is normal in babies)
specific areas of the primary motor cortex or primary somatosensory cortex that process information for specific regions of the body, organized into a homunculus
amount of cortex dedicated to a body region is unrelated to size of region (hand/lips have more cortex space than legs/back).
the right hemisphere of the brain controls the left side of the body and vice versa
specialized functions divided by right and left side
(basal nuclei) nuclei deep within the cerebrum that are part of the motor circuit
a dopamine precursor that has the ability to cross the blood-brain barrier
biological clock for humans, body has two (L/R), located in hypothalamus
a network of neurons in the medulla, pons, and midbrain. Loosely connected cell bodies (not tightly held into a nucleus) that control vital functions
The pyramids are the part of the corticospinal fibers at the level of the medulla. They form a column-like bulge on the ventral surface of the medulla and then they decussate at the medullary-spinal border
The olive is an olive pit-like bulge just lateral to the medullary pyramids. It indicates an underlying inferior olivary nucleus that serves as a relay for action potentials traveling into the cerebellum
Precentral gyrus organization (medial -> lateral)
Foot/ toes, lower leg, upper leg, pelvis, trunk, upper arm, lower arm, thumb/ fingers/ hand, facial expression, salivation/ vocalization/ mastication, swallowing
Postcentral gyrus organization (medial -> lateral)
Genitals, foot/ toes, lower leg, upper leg, pelvis, trunk, neck, upper arm, lower arm, hand/ fingers/ thumbs, upper face, lips, teeth/ gums, tong/ pharyx
Describe an MRI
A non-invasive brain scanning technique that allows you to see the inner structures of the brain through what appears to be many cuts/sections of the brain
What is a stroke? Different types?
- A stroke results from a section of the brain being starved of oxygen (blood).
- It can occur from either a burst blood vessel or a blockage of a blood vessel.
Sections of the body (planes)?
Sagittal – separates left and right sides of bodyTransverse – separates top and bottom parts of bodyCoronal – separates front and back parts of body
Trace the steps in the corticospinal tract (detailed)
- Upper motor neuron – Primary motor cortex -> internal capsule -> cerebral peduncle -> pyramid -> lateral corticospinal tract
- Lower motor neuron – Ventral root -> Spinal nerve -> neuromuscular junction
What is a tract?
- Specialized sections of the white matter in the spinal cord which correspond to a single function.
- eg – lateral corticospinal tract is the section of white matter than takes motor impulses from brain to effector.