The Brain And Nervous System Flashcards
Define cephalization
-the development of an anterior head where sensory organs and nervous tissues are concentrated
Nerve nets
-loose mesh of neurons found in radially symmetrical animals
Nerve cord
-bundle of nerves which extend from the central ganglia to the rest of the body
Ganglia
-functional clusters of neurons
What is the significance of bilateral symmetry
-body parts are mirror images on the either side of the midline
-organization of the nervous system such as paired nerves linking lobes in brain with specific muscles and receptors allows for sophisticated sensory processing
-Animals: coordinated, rapid movement to hunt prey, escape predators
Differential gene expression at…
-specific times (temporal) and in specific regions(spatially) gave rise to cell differentiation and cell determination(cell fates)
Neural tube
-the precursor of the CNS (brain and spinal cord)
Neural crest
-cells migrate and differentiate into a number of varied cell types
What is example of gene expression during neural tube formation
-cadherins (calcium dependent adhesion molecules)
-transmembrane proteins
-role in cell adhesion, ensures that cells within tissues are bound together
-dependent on Ca2+ to function
What are the main functions of the brain?
-Receive information
-integrate information
-send out information
-store information
-retrieve information
Blood brain barrier
-A separation of circulating blood and cebrospinal fluid (CSF)
-occurs along all capillaries and consists of tight junctions around the capillaries that don’t exist in normal circulation
Endothelial cells in Blood brain barrier….
-restrict the diffusion of microscopic objects(eg bacteria) and large or hydrophilic molecules inot the CSF
-allow the diffusion of small hydrophobic molecules (O2, hormones, CO2)
-cells of the barrier actively transport metabolic products such as glucose across the barrier with specific proteins
What are meninges and what are their function
-layers of connective tissue (membranes) covering the brain and spinal cord
-provide structural support for blood vessels
-serve as a “pad” between brain and skull
What are the three connective tissue layers of meninges
-pia(innermost), arachnoid, dura mater(outermost)
What is cerebrospinal fluid
-clear colorless fluid produced in the choroid plexus (a complex of glial cells-called ependymal cells)
-found in brain and spinal cord
-occupies the subarachnoid space(the space between the arachnoid mater and the pia mater) and the ventricular system
CSF circulates…
-nutrients and chemicals filtered from the blood and removes waste products from the brain
What is the function of CSF
-protect the brain from striking the cranium when the head is jolted
-CSF provides buoyancy and support to the brain against gravity
The buoyancy of CSF protects the brain because
-the brain and CSF are similar in density; this makes the brain float in neutral buoyancy, suspended in the CSF
-this allows the brain to attain a decent size and weight without resting on the floor of the cranium, which would kill nervous tissue
What are the ventricles
-cavities in the brain filled with CSF
-there are four ventricles, two lateral ventricles, the third ventricle, the fourth ventricle
What is a subdural haematoma
-swelling containing blood
-ventricle absorbs shock
Ventricular volume is significantly lower/higher in Alzheimer’s Disease patients compared to age-matched healthy subjects
-higher
What is the forebrain
-forms the cerebrum
-cerebrum has left and right hemispheres
What do the cerebral hemispheres correspond to and what are they connected with
-left cerebral hemisphere responds to sensory signals from the right side of the body and controls movements on right side of body.
-right hemisphere responds and controls movement on left side of body.
-connected by thick axon bundles (the corpus callosum) which enables the exchange of information between the hemispheres
What does the left hemisphere focus on?
-focus on details(such as recognizing a particular face in a crowd); spoken and written language, abstract reasoning math
-Wericke’s and Broca’s areas in left hemisphere
What does the right hemisphere focus on?
-focus on broad background (such as understanding the relative position of objects in space, intuitive thinking, conceptualization, music, art
Define lateralization
-the difference in function between the left and right hemisphere
Cerebral cortex
-outermost thin layer of grey matter (in mammals, comprised of 6 layers of neurons, 2-4mm thick in humans) covering a core of white matter
-convoluted folds to increase surface area
What does grey matter consist of
-neuron cell bodies and dendrites
What does white matter consist of
-axons (many axons have myeline sheaths)
What are the 4 brain lobes of the cerebrum
-frontal lobe, parietal lobe, temporal lobe, occipital lobe
Where is the frontal lobe and what does it control
-front of the brain
-controls executive function
-thinking, organizing, planning, problem solving, memory, Attention, movement
Where is the parietal lobe and what is its function
-sits behind frontal lobe
-deals with perception and integration of stimuli from the senses
Where is the occipital lobe and what is its function
-back of the brain
-vision
Where is the temporal lobe and what is its function
-runs along the side of the brain under the frontal and parietal lobes
-deals with the senses of smell and sound and the formation and storage of memories
What is the function of the cerebellum?
-coordinates/refines body movements by information integration and comparison
-receives sensory input from: receptors in muscles and joints, balance receptors in the inner ear, touch, vision, and hearing receptors
-this yields information about body position, the directions of movement of limbs or trunk
What is the brainstem comprised of and what does it connect to?
-comprised of 3 structures: the medulla, pons, midbrain
-connects the forebrain with the spinal cord
What are the functions of the brainstem
-heart and respiration rate
-blood pressure
-blood vessel dilation
-digestive system reflexes(vomiting)
What is the function of the midbrain?
-smallest region of the brain
-acts as a relay station for auditory and visual information
-controls eye movement
What is the Ventral Tegmental Area(VTA)
-part of midbrain
-has both dopamine and serotonin producing neurons
-involved in pleasure pathway/reward circut
What is the substantia nigra
-part of the midbrain
-involved in the control of body movement
What disease would you see a dimineshed substanstia nigra?
-Parkinson’s Disease
What is the reticulur formation in the brain
-network of neurons in the brain stem that connect the thalamus to the spinal cord
-integrate incoming sensory information
-filters incoming information
Ascending reticular formation
-sends stimulatory signals to the thalamus to activate the cerebral cortex
-produces different levels of alertness or consciousness
-filters incoming stimuli to discriminate irrelevant background stimuli
Descending reticular formation
-receives information from the hypothalamus
-connects with interneurons of the spinal cord that control skeletal muscle contraction
What is the thalamus derived from, where is it located and what is its function
-derived from the forebrain
-structure between the cerebral cortex and midbrain
-functions include: relaying signals from the special senses and motor signals to the cerebral cortex
-regulates consciousness, sleep and alertness
What is the hypothalamus derived from, where is it located and what is its function
-located below the thalamus just above the brainstem
-synthesizes and secretes hormones(neurohormones)
-links the nervous system to the endocrine system via the pituitary gland
-controls body temp, hunger, thirst, fatigue, circadian cycles, triggers sweating and shivery
-monitors the osmotic balance of blood
-example: makes ADH which is then released by the the pituitary gland
What are the basal ganglia(basal nuclei), where are they located, and what is their function
-a group fo nuclei of varied origin in the brains of vetebrates that act as a cohesive functional unit (the substantia nigra is a component of the basal ganglia)
-location surrounding the thalamus
-involved with voluntary movement
What can result from the damage of basal ganglia(basal nuclei)
-damage to the basal nuclei or loss of dopaminergic neurons in the substantia nigra can lead to muscle rigidity, tremors, inability to start or stop intended movements
-Parkinson’s
What is the limbic system and some of its components
-functional network with a number of components
-parts of the thalamus, hypothalamus, basal nuclei
-amygdala (emotion, fear)
-hippocampus(memory)
-olfactory bulbs(smell)
The limbic system is often called
-the emotional brain
-involved with emotional behavior: fear, anger, anxiety, motivation, satisfaction, pleasure
What is the hippocampus
-part of the limbic system; plays important roles in the consolidation of information from short term to long term memory and spatial navigation
In Alzheimer’s disease the…. Is one of the first regions of the brain to suffer
-hippocampus
-early symptoms: memory loss, disorientation
Describe the brain circut: reward pathway
-VTA (ventral tegmental area ) releases dopamine
-nucleus accumbens contains dopamine sensitive cells
-causes feelings of pleasure
-amygdala and hippocampus plays role in memory and whether experience is desirable
-prefrontal cortex coordinates all the information and determines behavior of individual
-pathway the same for opiates, methamphetamines, and nicotine
What are the two major divisions of the nervous system
-CNS: brain and spinal cord
-PNS nerves outside the CNS; main function of the PNS is the connect the CNS to the limbs and organs
What are the 2 major subdivisions of the PNS
-afferent system and efferent system
Afferent neurons transmit signals
-to the CNS
-includes sensory neurons that transmit sensory information from receptors to the CNS
Efferent neurons transmit signals
-from the CNS
-carry signals front the CNS to the muscles and glands(or effectors)
What are the two divisions of the efferent system
-somatic and autonomic systems
What is the the somatic system
-mostly voluntary; controls body movements that are conscious (mostly)
-some contractions of skeletal muscle are involuntary: shivering, reflexes, muscle that control posture
-utilizes motor neurons
-carries efferent signals from the CNS to the skeletal muscles
What is the ANS (autonomic nervous system)
-refers to collections of motor neurons (ganglia) situated in the head, neck, thorax, abdomen, and pelvis
-and the the axonal connections of these neurons
-functions below the level of consciousness (involuntary)
-controls visceral (organs of the gut) functions
ANS (Autonomic nervous system) effects
-heart rate, digestion, respiration rate, salivation, perspiration, diameter of pupils, urination, sexual arousal, smooth muscle contractions
What are the two division of the ANS (autonomic nervous system)
-sympathetic and parasympathetic
What does the sympathetic division do?
-utilized in situations involving stress, strenuous physical activity, danger, excitement
-fight or flight
-result in increased force and rate of heartbeat
-increase in blood pressure(constricts blood vessels, dilates bronchioles
What does the parasympathetic division do?
-used for ‘housekeeping’ functions (digestion)
-utilized during quiet, low stress times
-rest and digest
-nerves of the parasympathetic division (optic nerves, cranial nerves, spinal nerves) are located around the sympathetic nerves
Describe the vagus nerve
-extends down below the head, to the neck, chest, and abdomen, where it contributes to the innervation of the viscera
-besides output to the various organs in the body the vagus nerve conveys sensory information about the state of the body’s organs to the central nervous system
-80-90% of the nerve fibers in the vagus nerve are afferent sensory nerves communicating the state of the viscera (internal organs such as those in abdominal regions)
The Vagus Nerve is responsible for
-heart rate, gastrointestinal peristalsis, sweating, some muscle movements in the mouth, including speech and keeping the larynx open for breathing
The spinal cord
-carries impulses between the brain and PNS
-sensory info is transmitted up to the brain
-motor info transmitted from brain to periphery
-contains interneuron circuits that control motor reflexes
What is the primary somatosensory area
-located in the parietal lobes of each hemisphere
-integrates information regarding touch/pressure, temperature, pain
-if you stimulate portions of the primary somatosensory area, it causes tingling in related body parts on the opposite side of the body
What is the primary motor area
-located anterior to primary somatosensory area
-stimulation of portions of the primary motor area causes movements of specific body parts of the opposite sides of the body
What is the homunculus “little man”
-representation of the correlation between areas of the body from which sensory information projects to areas in the primary somatic sensory cortex
-in this type of representation, the size of various regions in the primary somatic sensory cortex is related to the number of sensory receptors in the corresponding part of the body.
Association areas: integration
-these areas surround the sensory and motor areas
-function in: integrating information from the sensory area; formulate responses, transmit the responses to the motor cortex
What are the association areas for language
-wernicke’s area : understanding languages
-Broca’s area: expressing languages
To speak the word you see
-the word is seen in the visual cortex, information concerning the word is understood in Wernicke’s area, and information from Wernicke’s area is transferred to Broca’s area, information is transferred from Broca’s area to the primary cortex
Broca’s area
-expressing language, involved in the coordination of the lips, tongue, and jaw. Initiates the complex series of movements necessary for speech.
Damage to Broca’s area
-don’t speak well few words, poorly pronounced (but can comprehend written and spoken words.
Broca’s Aphasia
-expressive aphasia: characterized by hesitant and distorted speech
Wernicke’s area
-understanding and formulating coherent speech
-coordinates input from auditory and visual area
Damage to Wernicke’s area
-people can speak, but words make no sense
Wernicke’s aphasia
-characterized by fluent language with made-up or unnecessary words with little or no meaning to speech, difficulty understanding other’s speech and unawareness of one’s own mistakes. When corrected, these individuals will repeat their verbal paraphasias and have trouble finding the correct word
Define memory
-storage and retrieval of a sensory or motor experiences
Short term memory
-depends on transient changes in neurons, such as changes in membrane potential(EPSP, IPSP) and/or reversible changes in ion transport (cause by indirect neurotransmitters)
Long term memory
-storage of memories for days, years
-permanent biochemical, molecular or structural changes that establish signal pathways that cannot be easily terminated
LTP: Long term potentiation
-caused by a short bursts of repetitive firing in the presynaptic neurons such that when there is single action potential later, it will evoke a greatly enhanced response in the post synaptic cells
How long does the effect of Long term potentiation last? When does it occur?
-effect can last hours, days, weeks according to the number and intensity of bursts of repetitive firing
-LTP occurs when a presynaptic cell fires at a time when the post synaptic membrane is strongly depolarized(due to recent repetitive firing of the same presynaptic cell or other means
What are the permanent alterations of Late LTP
-in the number and area of synaptic connections
-in the number and branching of dendrites
- in the gene transcription
-protein synthesis
What is learning
involves a change in the response to a stimulus based on information or experiences stored in memory
Store memory
When a stimulus is encountered, scan you memories
Modify you response accordingly -you “learn”
What is consciousness
-Awareness of ourselves and our surroundings
-Alert—semi conscious(sleep)—–unconscious
