Flashcards in Lesson 1: Introduction to Neuroanatomy Deck (173):
What are the two parts of the nervous system? What is each system composed of?
The nervous system consists of two parts:
1. The central nervous system (CNS). Consists of the cerebrum (cerebral hemispheres), brainstem (midbrain, pons and medulla), cerebellum, and spinal cord. Spinal cord transmits motor commands to body parts. Sensory info collected and sent to brain.
2. The peripheral nervous system (PNS).
Includes the cranial nerves, as well as the somatic (mediate skeltal muscle reflexes) and autonomic nervous systems (sympathetic and parasympathetic NS)
What is in the peripheral motor system? What is in the somatic nervous system?
What does the ANS consist of?
The cranial nerves are the peripheral motor and sensory nerves supplying the head and neck
Somatic nervous system includes those peripheral nerves that supply the limbs and trunk
The autonomic nervous system consists of sympathetic and parasympathetic divisions and supplies cardiac muscle, smooth muscle, and glands.
What is the term for information travelling toward/away from the central nervous system?
What type of info is it?
Info that travels towards the central nervous system is termed afferent, and it is usually sensory but not always. Information that travels away from the central nervous system is termed efferent, and is usually motor but not always.
What are the three types of fibre bundles connecting the parts of the nervous system?
Association Fibres: connecting areas within the same lobe; Projection Fibres: communicating between the cerebral cortex and lower centres in the brainstem and spinal cord;
Commissural Fibres: connecting centers in left and right cerebral hemispheres.
What is the central nervous system made up of? (structures)
Spinal cord, brainstem (medulla, pons and midbrain), cerebellum, and cerebral hemispheres (cerebrum).
What composes the Prosencephalon?
Telencephalon (cerebral cortex, basal ganglia, limbic system)
Diencephalon (thalamus and hypothalamus)
What composes the Mesencephalon?
Midbrain structures - red nucleus, substantia nigra, cerebral aqueduct
What composes the Rhombencephalon?
Metencephalon (pons and cerebellum, 4th ventricle)
What is the function of association and commissural fibres?
Association areas are directly connected to each other, whereas primary cortical area are indirectly connected through cortical association areas. Also serve as a hub through which primary cortical areas are indireclty connected.
What is the CNS responsible for?
Integrating all incoming and outgoing information and generating appropriate responses to the info received.
How is the CNS hierarchically organized?
Spinal cord is lowest level, serves simple sensorimotor functions in form of reflexes; Cerebral cortex is highest level, responsible for complex sensorimotor integration and higher mental functions.
What are the primary functions of the left and right hemisphere?
Left hemisphere - dominate language, speech and analytic processing, calculation, verbal memory; Right hemisphere - efficiency in emotions, musical skills, and paralinguistic functions, visual and spatial concepts
How is the brain topographically organized?
How is is portioned?
Spatial organization of neurons, tracts and terminals reflects the spatial relationship of the body surface and functionally related muscles groups with the projected brain areas. Accounts for somatosensory homunculus - Disproportionate representation of the head and mouth versus the lower limbs; more area for important structures. This organization occurs in both motor and sensory systems
What is neuroplasticity?
The brain's ability to change as a results of experience; ability to reorganize and gradually modify tissue functions when faced with pathologies
What does contralateral/ipsilateral mean?
Contralateral means opposite side and ipsilateral means same side.
What does rostral, caudal, dorsal and ventral mean in brain orientation?
(+ For the spinal cord and brainstem)
What does inferior/superior mean?
Rostral: location toward the nose (toward the brain)
Caudal: location toward the back of the brain (toward coccyx)
Dorsal: location toward the top of the brain (toward back of body) = posterior
Ventral: location toward the bottom of the brain near the jaw (toward abdomen) = anterior
Inferior: to below
Superior: to above
What are the planes of the brain? (9)
Sagittal: divides brain into left and right portions
Midsaggital: sagittal section at center separates the brain into two equal halves
Coronal: vertical section made perpendicular to the sagittal section, divides the brains into front and back parts
Horizontal: perpendicular to coronal and sagittal planes, divides brain into upper and lower parts
Transverse: right angle to longitudinal axis on a bend
Lateral: structures away from midsagittal plane
Medial: plane approaching midsagittal point
Proximal: structures close to a specific anatomic site of reference
Distal: structures farther from same anatomic site of reference
What are the terms related to limb movement? (8)
Flexion: bending movement of a limb
Extension: straightening movement of a limb
Abduction: limb moved away from central axis of body
Adduction: limb moved toward central axis of the body
Pronation: moves palm donward
Supination: turns palm upward
Protrusion: jaw out
Retraction: jaw in
What are the terms related to limb movement with brain pathology? (7)
Tremor: repetitive movement secondary to alternate contraction of opposing muscles (resting, action)
Akinesia: lack of voluntary motor activity
Bradykinesia: slowness of movement
Dystonia: atypical posture with abnormally sustained muscle contraction
Dyskinesia: any involuntary and abnormal movement
Tick: abrupt and transient stereotypical movements
Myoclonus: sudden and momentary contraction of one or a group of muscles
What are the 5 types of paralysis that can happen to muscles?
Monoplegia: upper or lower limb
Hemiplegia: paralysis of both upper and lower limbs on ons side
Triplegia: paralysis of three limbs
Quadriplegia: paralysis involving all four limbs
Paraplegia: paralysis of both lower limbs
Neuroanatomical Structure Terms:
What is Opercular?
Opercular: margins of cerebral convolutions serving as a cover
Commissure: band of fibres connecting part of brain or spinal cord on one side with same structures on opposite side of midline
Somatic: include most axial skeletal and associated muscles derived from somite
Viscera: internal organs containing nonstriated smooth muscles (digestive)
What is the difference between gray matter and white matter?
Gray matter is gross appearnce of cells in the brain, consist of nerve cells, supporting glia cells and unmyelinated fibres.
White matter is nerve fibres that form tracts and carry info from one brain site to another; white because of myelin lipid substance around it
What is a fasciculus?
Collection of nerve fibres that share a common origin as well as termination
What is stria?
Band of fibres that may differ in colour or texture
What is colliculus?
Small prominence of nervous system tissue
How does a cell become a tissue? What is the process of differential growth?
Cells divide repeatedly (proliferation). The developing nervous system then grows, by increasing the number and size of cells. Some areas grow more than others, causing "differential growth". Differential growth causes changes in shape.
How does the neural tube form?
Differential growth causes changes in shape. Imagine a flat plate in which two rows of cells begin to grow more rapidly, forming two furrows with a valley between, eventually folding to create a tube. This is how the hollow neural tube forms (see text). Individual cells begin to create junctions (synapses) with other neurons to communicate. At these synapses, chemicals called neurotransmitters are produced and released to make contact with special molecules called membrane receptors on the receiving cell. These are pre-and postsynaptic membranes, respectively. During development, some cells migrate (travel) to other parts of the nervous system to seed new colonies of cells.
Brodmann Areas Frontal Lobe: Where and what is their function?
4: Precentral gyrus - primary motor cortex
6, 8: Anterior to precentral gyrus - Premotor cortex
9-11: Prefrontal region - Cognitive association cortex
44, 45: Inferior frontal lobule - Frontal assocation language cortex; Broca area
Brodmann Areas Parietal Lobe: Where and what is their function?
3, 1, 2
3, 1, 2: Postcentral gyrus - primary sensory cortex
5, 7: Posterior to postcentral gyrus - Somatosensory association cortex
39: Angular gyrus - Reading and writing
Brodmann Areas Temporal Lobe: Where and what is their function?
22: Subtemporal and posterior temporal gyrus and planum temporale - posterior association language cortex; Wernicke area
41, 42: Gyri of Heschl - Primary auditory cortex
Brodmann Areas Occipital Lobe: Where and what is their function?
17: Calcarine cortex - Primary visual cortex
18, 19: Pericalcarine cortical area - Visual association area
What are the three main structures of the brain?
Cerebrum, brainstem (medulla, pons, midbrain), and cerebellum
What are the two classes of cells in the nervous system?
Neurons are excitable cells that communicate with one another. They have a resting potential and will depolarize, resulting in an action potential.
Glial cells support and nurture the neurons
What is the term for programmed cell death? Why is it important?
All cells in the body are programmed to die, but stops are in the way; some stops are pulled (cells are allowed to die) during development. This important process, programmed cell death (apoptosis) occurs throughout the embryo to shape organs and remove "mistakes".
What is myelination?
Results in insulation of the axon. Increases rate of conduction of action potential
What is proliferation and growth?
•proliferation - cell division (one way to increase size of organ)
•growth - increase in size (also differential growth) where some cells selectively grow, causing sheets to form bumps or layers to fold.
What is junction formation and migration?
•junction formation - attaches to other cells or adheres to the extracellular matrix
•migration - induced crawling of cells to other parts of system
What is differentiation?
•differentiation - to become different - specialization of cells means they can no longer undergo cell division
What are the two types of cells that the nervous system uses to process information?
General: info originates from the surface of the body and is processed by nonspecific and general receptors (pain, temperature)
Special: info mediated by specialized receptors to specialized functionally committed cells in the nervous system (smell, taste)
What are gyri and sulci?
Gyri: fold in cerebral cortex which is a hill
Sulci: fold in cerebral cortex which is a valley
What are the two fissures in the cortex?
Lateral fissure, longitudinal fissure
What are the structures that make up the neuroglia?
Includes microglia, Schwann cells, astrocytes, oligodendrocytes, and ependymal cells
What are the shapes neurons are classified into? (+Examples)
Multipolar (common, highly variable shape); Bipolar, (uncommon, typical in retina);
Unipolar, also called (pseudo-unipolar, typical peripheral sensory neuron).
What are the 4 main functions of neurons?
•communication: receive graded potentials (EPSP, IPSPs) and transmit (action potential) information
•integration of information - raise/lower threshold, alter probability of firing
•storage of information
•recovery of information
What is the function of ribosomes?
Rough endoplasmic reticuculum?
ribosomes for making proteins,
rough endoplasmic reticulum (RER) for protein export,
Golgi Apparatus for modifying proteins,
What is the function of the cytoskeleton?
cytoskeleton (microfilaments, microtubules and neurofilaments) for shape and transporting materials;
mitochondria for energy;
lysosomes to carry away cell waste;
cell membrane to contain the contents and for communication with other cells
What are dendrites in a neuron?
What does the axonal membrane do?
Protrusions from the cell body or perikaryon, with dendritic spines; with synapses for incoming signals but only ONE axon that carries materials away from the cell body with a specialized (excitable)
Axonal membrane that conducts an action potential (electrical signal)
What is the function of the axon terminus?
What is the Nissl body?
End of the axon, there are materials for the final synthesis and release of neurotransmitters.
Nissl body, is an accumulation of RER, is very abundant in neurons.
What is axonal transport? How does it correspond to the Action Potential?
Movement of organelles along the axon to supply the end terminus with materials for the release of neurotransmitters. It contrasts with the "action potential"which only occurs along the membrane and is the signal that causes release of the neurotransmitter.
What is the resting potential of a neuron?
A difference in charge between the inside and outside of the cell membrane) which will depolarize if stimulated, resulting in a wave of changing charge along the axon, ("action potential").
What is an EPSP/IPSP?
Excitatory Post Synaptic Potential (+): If the signal received is excitatory, the membrane of the receiving neuron (post-synaptic membrane) becomes depolarized increasing its likelihood to fire.
Inhibitory Post Synaptic Potential (-): If the signal is inhibitory (hyperpolarized), it is less likely to fire.
Where is axoplasmic transport?
Within the axoplasm (axon cytoplasm).
What are axons wrapped with? Why is it better to have a thicker axon?
Where is myelination done?
All axons are insulated (wrapped), by either oligodendrocytes (CNS) or Schwann cells (PNS).
The greater the number of wrappings, the thicker the axon. Myelin has the effect of speeding up the action potential, the thicker the axon, the faster the signal will travel.
Myelination is done by Schwann cells in the PNS and oligodendrocytes in the CNS.
What is a motor unit?****
A single alpha motor neuron and all the muscle fibres it innervates.
Where does the action potential begin, and what is the process?
Begins at axon hillock, travels down the axon and reaches the nerve terminus, vesicles of NT, are released from the end terminus to fuse with the pre-synaptic membrane for the release one "dose" of NT into the synaptic cleft. The NT binds (attaches to) receptors on the post-synaptic membrane producing either an EPSP or an IPSP
What are the two ways to cancel the signal created by the NT in the synaptic cleft - activating post-synaptic membrane?
1) re-uptake of the neurotransmitter into the presynaptic membrane or 2) release of an enzyme that blocks or destroys the neurotransmitter in the cleft. (acetylcholine is destroyed by acetylcholinesterase)
What is the disease where the acetylcholine receptors on muscle (on the post-synaptic membrane) are defective?
What is the term for EPSPs produced repeatedly in a short period of time that accumulate to increase the probability of firing an action potential?
What is the term for the additive effect of many EPSPs all over the cell membrane that accumulate to increase the probability of firing?
Circuit strategies: what is the term for stimuli from many neurons to excite a single neuron, converging in one area from many areas?
Circuit strategies: what is the term for spread of one neuron to many areas?
What is positive/ negative feedback?
Turns on signal to prolong it slightly after signal crosses the synapse.
Turns off signal more quickly by turning on an inhibitor right after the signal crosses the synapse.
Circuit strategies: what is the term for multiple synapses from one neuron on a second neuron to facilitate (enhance the intensity of) the signal. They occur together?
What is positive/negative feedforward?
Sends an additional +ive signal to interneurons before the signal crosses the synapse to extend the duration of the signal.
Sends an inhibitory signal before the signal crosses the synapse to turn the signal off even more quickly that through negative feedback.
Circuit strategies: what is the term for sends inhibitory signals to adjacent neurons to reduce their likelihood of firing and thereby sharpening or more accurately localizing the signal on the intended target?
If a peripheral nerve is cut, where does regeneration of the axon occur?
Regeneration of the axon starts from the point of injury as the scaffold is only damaged distal to the lesion
Where are ependymal cells located and what do they do
What can specialized ependymal cells form?
•lining of ventricles and spinal cord
•secretion from ependymal cells in choroid plexus produces cerebrospinal fluid
- Wrapped in capillaries form the choroid plexus and secrete the cerebral spinal fluid within the ventricles.
What are the 5 functions of astrocytes?
•regulate neural environment - buffer ions, glucose, remove neurotransmitters
•support - physical, nutritional and ionic
•nutrition transfer - from capillary to neurons
•divide rapidly- a source of fast growing tumours (astrocytomas)
•produce the scar tissue of the CNS Astrocytes form scar tissue in the brain.
Where are microglia derived from and what do they do?
•derived from (monocytes) blood cells that become major packman (phagocytes) clean up debris by engulfing them (phagocytosis), remodel scars etc.
Where is the central sulcus? What boundary does it mark?
Begins at top of brain and extend along dorsolateral surface in a downward, rostral direction, ends at lateral fissure.
Marks boundary between frontal and parietal lobes; separates primary motor cortex and primary sensory cortex
Where is the lateral fissure? What does it separate?
Begins rostrally below the frontal pole and extends posteriorly up toward inferior parietal lobe. Separates frontal and temporal lobes anteriorly
What does the parieto-occipital lobe separate?
Separates the parietal lobe from the occipital lobe
What are the 4 important gyri of the frontal lobe?
Where is the main gyrus located?
Are actvated motor acts controlled on the ipsilateral or contralateral half of the body?
Precentral gyrus and three horizontal gyri. Precentral gyrus is rostral to central sulcus, its anterior boundary marked by the precentral sulcus. Is the site of the primary motor cortex (area 4), contains homunculus
Activating and controlling motor acts on contralateral half of body
Frontal lobe: Premotor cortex - what does it do?
Premotor cortex is rostral to precentral sulcus (area 6), involved with complex and skilled movements. Areas within that control speech, hand and finger movements.
Frontal lobe: Prefrontal cortex - what does it do?
Prefrontal cortex (area 10-12) – contributes to personality and mood, regulation of cognitive function (reasoning, abstract thinking, self-monitoring, decision making)
What are symptoms of a lesion in the prefrontal cortex?
Difficulty planning, thinking, reasoning, performing executive functions.
What are the main functions of the parietal lobe?
Concerned with spatial orientation, cross-modality integration, memory, recognition and expression of emotions
Parietal lobe: What is the name for the primary sensory cortex?
Where are sensations recognized in awareness?
How are senses represented?
Postcentral gyrus (area 3, 1, 2); sensations are recognized as awareness in parietal sensory association cortex – areas 5 and 7. Sensory representation is disproportionate
What would a lesion to the parietal lobe cause?
Lesion to somesthetic association cortex?
Contralateral sensory loss – tactile recognition, constructional skills, spatial orientation and memory
– Agnosia and asterognosis
What are the main structures of the occipital lobe?
Contains the primary (area 17) and secondary (area 18) visual cortical areas
Occipital lobe: what is the function of the calcarine sulcus?
Divides the primary visual cortex (area 17) into upper and lower operculum.
Occipital lobe: what does the visual association cortex do?
Is involved with elaboration, recognition, and appreciation of visual stimuli
What is the result of a lesion in the primary visual cortex?
Lesion in visual association area?
Lesion in primary visual cortex causes blindness in the opposite visual field;
Bilaterally results in visual agnosia, colour agnosia, alexia
Which structures contribute to the "where" and "what" nature of stimuli?
“where” = superior occipital lobe and its parietal projections contribute to the visual processing
“what” = the lower occipital region with its projections to the temporal cortex for nature of stimuli
What are the main functions of the temporal lobe?
Serves audition, memory, through elaboration, comprehension of spoken and written language, and olfaction.
Temporal lobe: What three gyri form the primary auditory cortex?
Superior, middle and interior temporal gyri.
Temporal lobe: What three structures form the pyriform cotex?
Uncus, parahippocampal gyrus, amygdaloid nuclear complex
What is the result of a lesion in the temporal cortex?
Significantly affects auditory perceptual function and skills for phonemic discrimination
Temporal lobe: What happens with pathology to the language association cortex?
In dominant hemisphere (Wernicke area, area 22) results in receptive spoken and written language and word-finding deficit.
What is the function of the orbitofrontal region, and olfactory bulb?
Orbitofrontal region serves emotions, personality and inhibition.
Olfactory bulb and tract in the olfactory sulcus, serve sense of smell.
Where are the following structures located: are inferior temporal gyrus, occipitotemporal gyrus, lingual gyrus, collateral sulcus, parahippocampal gyrus and uncus, (hippocampus parahippocampus)
Temporal and occipital lobes
What three structures make up the limbic lobe?
Parahippocampal gyrus, isthmus, cingulate gyrus
What does the corpus callosum do? Where is it located?
Interconnects most cortical areas of both hemispheres. - Memories, experiences, and actions of both hemispheres are shared and integrated by way of the corpus callosum Located in the floor of the longitudinal (interhemispheric) fissure.
What are the 4 main parts of the corpus callosum?
(Rostral to caudal end) rostrum - most anterior, genu – anterior bend, body – large portion caudal to genu, splenium – posterior region
What structure is this: separates corpus callosum from overlying cingulate gyrus?
What structure is this: marks inferior boundary of frontal lobe
What structure is this: part of limbic brain, circles corpus callosum and posteriorly curves ventrally to continue as paraphippocampal gyrus in MTL
What does the septum pellucidum mark?
Marks medial walls of anterior horns of two lateral ventricles
What is the function of the fornix?
Important in regulating the limbic brain functions of emotions and memory
What is the function of the thalamus/hypothalamus?
sensorimotor integration and speech-language-hearing; controls endocrine, autonomic, regulatory and drive emotions
What does the massa intermedia do?
Connects two thalami
What is the funtion of the pituitary gland?
Secretes hormone that regulate systems involved in sex drive, pain, emotional drive, temp control
What does the pineal body do?
Secretes NT – serotonin, melatonin, norepinephrine
Which structure is this: site at which optic fibers from medial retina of each eye cross midline, join uncrossed fibers of lateral retina and continue to opposite hemisphere
Where is the insular lobe and what does it do?
Inside lateral fissure by overgrowth of opercula of frontal, parietal, and temporal lobes. Has long and short gyri. Known for nonelaboration of function, related to limbic and sensorimotor functions
Where is the caudate nucleus found?
Rostrally, the head forms the lateral wall of the anterior horn of lateral ventricle into which it bulges. Tail extends caudally form the head, curves around ventricular trigone, enters inferior horn, ends at level of amygdala
Where is the putamen, globus pallidus, claustrum, amygdaloid nucleus?
within subcortical white core of the brain; medial to putamen; in white matter between insular cortex and lateral margin of lenticular nucleus; rostral-medial temporal lobe
What does the brainstem connect? What does it consist of?
Connects diencephalon and spinal cord. Consists of midbrain, pons medulla
What is the function of the brainstem?
Monitors all brain outputs. Processes automatic control systems that are genetically acquired.
Functions of the reticular formation?
Facilitate, inhibit, modify and regulate all cortical functions. Also essential for regulating visceral, sensorimotor, and neuroendocrine activities.
What is the function of the midbrain?
Contains all incoming sensory and outgoing motor fibers and important reticular and CN nuclei.
What do the midbrain superior and inferior colliculi do?
Superior colliculi - reflexive control of eye movement
Inferior colliculi - mediate transmission of auditory impulses form ear to thalamus and auditory cortex.
Midbrain: Functions of the tectum, tegmentum, and basis pedunculi?
Tectum: connection between third and fourth ventricles, role in survival – 3D orientation map; also mediates visual reflexes
Tegmentum: several nuclei, reticular formation, medial lemniscal fibres, fibres to cerebellum
Basis pedunculi: ventral to tegmentum, consists of the pes pedunculi).
Midbrain: What does the substantia nigra do?
Contains group of nuclei that produce dopamine
What structures make up the pons?
All descending motor fibers and ascending sensory fibers, cranial nuclei, reticular formation, transverse fibers that form the middle cerebellar peduncle (attaches cerebellum to brainstem)
What structure is this in the pons: Contains ascending and descending fibres and numerous diffusely scattered pontine reticular nuclei
What structure is this in the pons: responsible for mediating fine discriminative touch in the body
What structure is this in the pons: contain cortical descending fiber tracts, pontine nuclei, and pontorcerebellar fibers.
What structures does the medulla contain?
Contains all motor fibers that descend to the spinal cord and all the sensory fibers that carry sensory information from the body to more rostral brain areas.
Major structures of the medulla?
ventral median sulcus pyramidal tract, inferior olivary nucleus, dorsal tubercula
What does the pyramidal tract do in the medulla?
Carries motor info from motor cortex to spinal cord for activation of skeletal muscles.
What structures are these in the medulla: carry fine discriminatory sensory info from body to medulla and then to thalamus
gracile fasciculus and cuneate fasciculus
What does the cerebellum do?
Coordinates and modifies tone, speed and range of muscular executions in motor function
How is the cerebellum divided?
Divided into cerebellar hemispheres. Structures of midline portion grouped into the vermis. Each hemisphere divided into three lobes: anterior, posterior, flocculondular.
Where does input/output from the cerebellum come from?
Input: afferents from motor cortex by way of the pons through fibres of middle cerebellar peduncle.
Output: Projects predominantly to opposite motor cortex, through superior cerebellar peduncle
What does the spinal cord do?
-Bidirectional pathway, transmits motor impulses from brain to visceral organ and muscles and carries sensory information from the body to the brain.
What are the three layers of the spinal cord?
Pia, arachnoid, and dura. The internal anatomy is composed of gray matter and white matter.
What does the gray and white matter contain?
-Gray matter: all spinal nerve cells, surrounded by -
White matter: ascending and descending fibers, divided into three myelinated funiculi: dorsal, lateral and ventral.
What is the composition of the white matter?
Has two dorsal horns (contain nerve cells that receive sensory information from the body through dorsal root fibres) and two ventral horns (motor nerve cells whose axons leave cord through anterior roots to activate visceral and skeletal muscles and glands)
What is the function of interneurons?
interneurons communicate with each other and LMNs of the muscles).
What are the 5 divisions of the spinal cord?
Cervical, thoracic, lumbar, sacral, coccygeal.
Which cranial nerve: sensory; responsible for perception of smell; originated from receptor cells in mucosa of nasal cavity and synapses in olfactory bulbs on orbital surface of frontal lobe, axons travel in olfactory tract and terminate in cortical olfactory area of temporal lobe
Which cranial nerve: brain tract concerned with visual sensation; originate from retina in both eyes, unit at optic chiasm, crossed and uncrossed optic fibers continue in tract, via thalamus project info form each eye to visual cortex in occipital lobes
Which cranial nerve: motor; controls 4/6 muscles responsible for moving eyeball; emerges from ventral surface of midbrain medial to pes pedunculi. Also innervates levator palpebrae – lifts upper eyelid
Which cranial nerve: motor; controls muscle responsible for eye movement; exists from brainstem below inferior colliculus
Which cranial nerve: originate in tegmentum (pons); mixed nerve; sensory for the face, head and oral structures and motor nerve for jaw movements; roots leave brainstem from ventrolateral surface of pons
Which cranial nerve: motor; controls lateral rectus muscle (turns eye away from the nose); originate in tegmentum and emerge ventrally from junction of pons and medulla
Which cranial nerve: primarily motor; controls all muscles of the facial expression, serves sense of taste from anterior two thirds of tongue; fibers exit from ventrolateral surface of pons
Which cranial nerve: sensory; has vestibular (concerned with position of head in space) and acoustic (concerned with hearing).; fibers enter brainstem at ventrolateral surface of the pons at its junction with medulla; location is the landmark of the pontomedullary junction
Which cranial nerve: sensory and motor; originates in medulla; sensory processes sensation of touch and taste from posterior third of the tongue and oral pharynx, motor function to contribute to process of swallowing; fibers leave medulla below acoustic nerve
Which cranial nerve: primarily sensory; fibers leave brainstem from lateral medulla just below point of exit for glossopharyngeal nerve; has motor component – activates muscles of pharynx, larynx, and soft palate.
Which cranial nerve: motor; innervates muscles for controlling head movement; spinal roots exit from four cervical segments and contribute to innervation of neck and shoulder muscles.
Which cranial nerve: motor; innervates muscles of the tongue; nucleus in the medulla, fibers exit medulla just lateral to pyramid; branches innervate intrinsic and extrinsic muscles of the tongue
What are the 3 primary elements of the neuron?
What do they do?
Cell body, dendrites, and axon
-Cells receive impulses via dendrites and initial segment of axons. Cells conduct impulses through axonal fibers, which travel distances and synapse on receptive ends of other nerve cells and target organs
Are dendrites afferent/efferent? What do they do?
Dendrites are afferent, transmitting info to the cell body from other cells via synaptic sites.
Are axons afferent/efferent? What do they do?
Axons are efferent structures that transmit info away from cell body to other neurons or target organs.
What produces myelin in the CNS? What are the breaks in the sheath?
-Oligodendroglia cells produce myelin sheath in CNS, sheath formed in small segments with breaks called Nodes of Ranvier
What produces myelin in the PNS?
In PNS, the myelin sheath is produced by Schwann cells, which are located along the axons
What is the synapse?
-Space between presynaptic terminal and the postsynaptic cells, includes presynaptic terminal synaptic cleft and postsynaptic cell
What's in the synaptic terminal?
Contains vesicles filled with NTs that mediate communication between cells.
How does communication happen at the synapse?
Occurs through a NT released from the terminals. Presynaptic cell is stimulated to release its NT by action potential travelling down axon. Depolarization causes vesicles at axon terminals to release NT into cleft area.
What causes an action potential?
If depolarization is large enough to cause membrane potential to reach threshold, the cell will fire an action potential
What are the 3 types of nerve cells?
Nerve cells are multipolar (CNS cells), bipolar or unipolar.
Neuroglial cells: what is an astrocyte?
Protect brain by forming external and internal limiting membranes, contribute to blood-brain barriers, regulate extracellular concentration of ions
Neuoglial cells: what do oligodendroglia cells do?
Oligodendroglia cells form and maintain the myelin sheath in CNS.
What type of neurglia is this: line the inner surface of the ventricles, form internal limiting membrane
What type of neuroglia is this: scavengers of CNS, proliferate and migrate to the injury site – transform into macrophages
What happens in an action potential? (ions)
Initially sodium flow into cell, causing depolarization (>0mV); sodium channels close rapidly, allowing return to resting potential. Repolarization occurs with opening of voltage-gated potassium channels that allow more K to flow down concentration gradient. Cell becomes hyperpolarized, K channels close, cell can establish resting potential again
-Absolute refractive period – after action potential cell is unable to produce another action potential. They are all or nothing responses.
What creates the greatest conduction velocity in a neuron?
Large diameter axons
In development of the nervous system, what gives rise to the endoderm and mesoderm?
Epiblastic cells (week 3)
What forms the neural plate in development of the nervous system?
Neuroectoderm overlying midline notochord thickens (day 18)
What does the neural tube develop into in development of the nervous system?
Neural tube develops into brain and spinal cord
What does the neural crest develop into in development of the nervous system?
Neural crest develops into the cranial and spinal ganglia, nerve sheaths, postganglionic autonomic nerves
What happens by week 4 of development?
Rostral two-thirds of neural tube represents future brain, and caudal third represents future spinal cord (eventually close).
A pair of lateral outgrowths from forebrain appears – optic vesicles are primordial for the retinas and optic nerves
What happens after the neuropore closes?
Three primary brain vesicles form – prosencephalon, mesencephalon, and rhombencenpahlon.
What happens in the telencephaon at week 4 of development?
Vesicles give rise to: olfactory lobe, corpus striatum (caudate nucleus and lentiform nucleus) and cerebral cortex
What happens to the prosencephalon in development?
Lateral outgrowths from forebrain appears – optic vesicles are primordial for the retinas and optic nerves
Telencephalic vesicle appear and grow into cerebral hemispheres, each with lateral ventricle
What does the caudal forebrain develop into?
Develops into diencephalon. Cavity is third ventricle – epithalamus, thalamus, metathalamus, hypothalamus and subthalamus develop in lateral walls of third ventricle
What does the midbrain develop into?
Tegmentum – includes red nuclei, substantia nigra, reticular nuclei and nuclei of oculomotor nerve and trochlear nerve
What does the hindbrain develop into?
Pons and cerebellum, and myelencephalon (medulla oblongata), cavity develops into 4th ventricle and central canal, going into spinal cord
myelencephalon: - Medulla oblongata
What happens to the spinal cord in development?
-Neural tube closes, its walls thicken and stratify. Three layers – inner ependymal, middle mantle and external marginal become differentiated.
What parts of the ANS are derived from the neural tube?
-Motor nuclei for all cranial and spinal nerves and all preganglionic neurons