Chapter 14 - Study Guide PDF

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Bio 201

Fall, 2020

Chapter 14 Study Guide Know major landmarks in brain – review terms from sheep brain dissection, word list for Lab Practical

Know basic development of brain. What happens at week 3? Week 4? Week 5? Know forebrain, midbrain, hindbrain, telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon. Know what each develops into. • Nervous system develops from ectoderm – by 3rd week, neural plate becomes a groove with neural folds along each side – by 4th week, neural folds join to form neural tube – lumen of the neural tube develops into central canal of spinal cord and ventricles of the brain – cells along the margin of the neural groove is called the neural crest • develop into sensory and sympathetic neurons and schwann cells – by 4th week, neural tube exhibits 3 anterior dilations • 4th week – forebrain – midbrain – hindbrain • 5th week – telencephalon – diencephalon – mesencephalon – metencephalon – myelencephalon

Meninges. Know the layers and how they differ in brain and spinal cord. Be able to locate the ventricles of the brain and know their names (There are 4 of them).

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Dura mater -- outermost, tough membrane – outer periosteal layer against bone – where separated from inner meningeal layer forms dural venous sinuses draining blood from brain – supportive structures formed by dura mater • falx cerebri, falx cerebelli and tentorium cerebelli

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– epidural space filled with fat in low back • epidural anaesthesia during childbirth Arachnoid and pia mater – as in spinal cord – subarachnoid and subdural spaces

Ventricles and cerebrospinal fluid: • Internal chambers within the CNS – lateral ventricles in cerebral hemispheres – third ventricle = single vertical space under corpus callosum – cerebral aqueduct runs through midbrain – fourth ventricle = chamber between pons and cerebellum

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– central canal runs down through spinal cord Lined with ependymal cells Choroid plexus produce CSF

CSF. Know where it is made, path it travels through brain, the 3 purposes it serves. What is the choroid plexus? Where is CSF absorbed? (arachnoid granulations) Cerebrospinal fluid: • Fills ventricles and subarachnoid space • Brain produces and reabsorbs 500 ml/day – Only about 100 - 160 ml present at a time – choroid plexus creates by filtration of blood • Functions – floats brain so it is neutrally buoyant – cushions from hitting inside of skull – chemical stability -- rinses away wastes • Escapes (4th ventricle) to surround brain • Absorbed into venous sinus by arachnoid villi Flow of cerebrospinal fluid:

Brain barrier system. Blood-brain barrier. How is it formed? (tight junctions of endothelial cells.) What purpose does it serve? What crosses the blood-brain barrier? What can’t cross the blood brain barrier? •

Blood-brain barrier is endothelium – permeable to lipid-soluble materials • alcohol, O2, CO2, nicotine and anesthetics

– circumventricular organs • in 3rd and 4th ventricles are breaks in the barrier where blood has direct access

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• monitors glucose, pH, osmolarity and others • route for HIV virus to invade the brain Blood-CSF barrier at choroid plexus is ependymal cells joined by tight junctions

Know the components of the brainstem. Medulla oblongata – what are pyramids? Cardiac center, vasomotor center, respiratory centers; other functions; Cranial nerves IX, X, XI, XII

Hindbrain- medulla oblongata: • Cardiac center – adjusts rate and force of heart • Vasomotor center – adjusts blood vessel diameter • Respiratory centers – control rate and depth of breathing • Many sensory and motor functions – Taste, chewing, coughing, sneezing, gagging, swallowing, vomiting, salivation, sweating, movements of tongue and head – Ascending and descending nerve tracts – Nuclei of sensory and motor CNs (IX, X, XI, XII) – Pyramids visible on surface

Pons – how is it connected to the cerebellum? Cranial nerves V, VI, VII, VIII; functions in pons include hearing, balance, sleep, others; Know anatomy of cerebellum – arbor vitae, folia, cerebellar hemispheres, vermis, cerebellar peduncles • Bulge in brainstem, rostral to medulla • Ascending sensory tracts • Descending motor tracts • Pathways in and out of cerebellum • Nuclei • concerned with posture, sleep, hearing, balance, taste, eye movements, facial expression, facial sensation, respiration, swallowing, and bladder control • cranial nerves V, VI, VII, and VIII

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Cross-section of pons:

Midbrain – cerebral peduncles, substantia nigra, cerebral aqueduct, corpora quadrigemina (superior colliculi and inferior colliculi) – know functions Reticular Formation – sleep and consciousness. If damaged, causes coma. Where is it located? What is habituation?

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Central aqueduct CN III and IV  eye movement Cerebral peduncles – hold corticospinal tract Tegmentum – connects to cerebellum and helps control fine movements through red nucleus Substantia nigra – sends inhibitory signals to basal ganglia and thalamus (degeneration leads to tremors and Parkinson disease) Cerebral Crus - corticospinal nerve tracts Central gray matter = pain awareness Tectum (4 nuclei - corpora quadrigemina) – superior colliculus (tracks moving objects, blinking, pupillary and head turning reflexes) – inferior colliculus (reflex turning of head to sound)

Diencephalon – thalamus, hypothalamus, epithalamus. Hypothalamus – major control center of autonomic nervous system – hormone secretion, autonomic effects, thermoregulation, food and water intake, sleep and circadian rhythms, memory, emotion Thalamus – important “relay” station to and from brain –most ascending spinal cord tracts synapse here. Epithalamus – pineal gland.

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Hypothalamus – Walls and floor of 3rd ventricle – Functions • hormone secretion • autonomic NS control • thermoregulation • food and water intake (hunger and satiety) • sleep and circadian rhythms • memory (mammillary bodies) • emotional behavior Epithalamus – Epithalamus consists of pineal gland (endocrine) and the habenula (connects limbic system to midbrain)

Cerebellum – anatomy and functions. Cerebral hemispheres, vermis, folia, arbor vitae, cerebellar peduncles. Motor coordination, spatial perception, timekeeper (what does this mean?), scheduling tasks, detecting differences between similar sounding words (jasmine and Jazz man)

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Two hemispheres connected by vermis Cortex = surface folds called folia Output comes from deep gray nuclei granule and purkinje cells Sits atop 4th ventricle White matter (arbor vitae) visible in sagittal section Connected to brainstem by cerebellar peduncles – superior peduncle = output to midbrain, thalamus, and cortex – middle peduncle = input from cerebral cortex and inner ear – inferior peduncle = spinocerebellar tracts (proprioception) Cerebellum function: – Evaluation of sensory input – coordination and locomotor ability – spatial perception - role in 3-dimensional reasoning – Timekeeping center – predicting movement of objects – Distinguish pitch and similar sounding words – Planning and scheduling tasks

Cerebrum – know the lobes and what their general functions are. Cerebral white matter – know projection tracts, association tracts, commissural tracts. Gray matter on brain surface.

Functions of cerebrum: • Frontal – voluntary motor functions – planning, mood, smell and social judgement • Parietal – receives and integrates sensory information • Occipital – visual center of brain • Temporal – areas for hearing, smell, learning, memory, emotional behavior Tracts of cerebral white matter:

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Most of cerebrum is white matter Types of tracts – projection tracts • from brain to spinal cord, forms internal capsule – commissural tracts • cross to opposite hemisphere – corpus callosum – anterior and posterior commissures – association tracts • connect lobes and gyri within a hemisphere

Limbic system – centers of emotion and learning – composed of cingulate gyrus, hippocampus and amygdala: hippocampus – functions in short term memory. Has centers for gratification and aversion.

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Loop of cortical structures – amygdala, hippocampus and cingulate gyrus Role in emotion and memory – pleasure and aversion centers

Basal Nuclei: Deep in cerebral cortex – caudate nucleus, putamen, globus pallidus; involved in motor control. Important in starting and stopping intentional movement – these are disrupted in Parkinson Disease. Cognition: range of mental processes by which we gain and use knowledge; accomplished through networks in distributed association areas of the cerebral cortex; Parietal Lobe: perceive and attend to stimuli; Temporal lobe helps to identify stimuli; Frontal lobe – think about the world and plan appropriate behaviors. Lesions (damage) in temporal lobe can cause agnosia (inability to recognize familiar objects; prosopagnosia - cannot recognize faces. Memory: Learning = acquiring new information. Memory = information storage and retrieval. Forgetting = eliminating trivial information…this is as important as remembering. Hippocampus is the brain area most involved in creating new memories. New memories are linked to knowledge already acquired. Cerebellum is important in learning motor skills. Amygdala ties memories to emotions. Amnesia – inability to describe past events Review functional regions of cerebral cortex. Special Senses: o Vision associated with occipital lobes. o Hearing associated with temporal lobe and insula. o Equilibrium associated with cerebellum and brainstem.

o Taste (gustation) associated with postcentral gyrus of parietal lobe and insula. Smell (olfaction) medial temporal lobe and frontal lobe. General senses: Touch, pressure, stretch, movement (and proprioception) heat and cold, pain o What is the primary somatosensory cortex? POST-CENTRAL GYRUS Where is it? PARIETAL LOBE o NOTE: post central is posterior to the central sulcus – so in parietal lobe o What is the sensory homunculus? Area of cortex dedicated to sensations of body parts is proportional to the sensitivity of that body part (# of receptors)

o What is somatotopy? The topographic association of positional relationships of receptors in the body via respective nerve fibers to their terminal distribution in specific functional areas of the cerebral cortex o Where and what is the primary motor area? PRE-CENTRAL GYRUS, IN FRONTAL LOBE o NOTE: pre central is anterior to the central sulcus – so frontal lobe. o Most of the neurons in the primary motor area control body areas having the FINEST motor control o The motor association area? PRE-CENTRAL GYRUS (relays signals to spinal cord) o The somatic sensory area is at the POST-CENTRAL GYRUS o The body is represented in an upside down matter in the sensory area o Body regions within most sensory receptors send impulses to neurons that make up a large part of the sensory area o The left side of the brain receives impulses form the right side of the body o What is the motor homunculus? o The body map on the motor cortex o The body is represented upside down o Pathways are crossed o PROPORTIONAL TO NUMBER OF MUSCLE MOTOR UNITS IN A REGION o What are upper motor neurons? Lower motor neurons? (Review basal nuceli and cerebellum). o UPPER MOTOR NEURONS  PYRAMIDAL CELLS; SUPPLIES MUSCLES OF CONTRALATERAL SIDE

 ORIGINATE IN THE CEREBRAL CORTEX  TERMINATES IN BRAINSTEM OR SPINAL CORD  ARE APART OF THE CNS o LOWER MOTOR NEURONS  ORIGINATE IN THE BRAINSTEM (CRANIAL NERVES) OR SPINAL CORD (SPINAL NERVES)  TERMINATES AT THE NERUOMUSCULAR JUNCTION (MUSCLES)  ARE APART OF THE PNS  Motor or sensory neurons with cell bodies located OUTSIDE of the brain and spinal cord correspond to LOWER motor neurons

Wernicke and Broca areas. What are their functions? What is aphasia? Broca's and Wernicke's areas are cortical areas specialized for production and comprehension, respectively, of human language. o Broca's area is found in the left inferior frontal gyrus – PRODUCTION OF SPEECH o Broca’s (expressive or motor) aphasia:  Damage to a discrete part of the brain in the left frontal lobe of the languagedominant hemisphere has been shown to significantly affect the use of spontaneous speech and motor control. Words may be uttered very slowly and poorly articulated. Speech may be labored and consist primarily of nouns, verbs or important adjectives. People with Broca’s aphasia have great difficulty with repetition and severe impairment with writing. o Wernicke's area is located in the left posterior superior temporal gyrus. – COMPREHENSION/UNDERSTANDING SPEECH  Damage to the posterior superior areas of the language dominant temporal lobe (wernicke’s area) has been show to significantly affect speech comprehension. Information cannot be sufficiently “translated”. Able to talk volubly and gestures freely.  This pattern of receptive apashia is marked by:  Poor comprehension  Pharaphasic errors (calling a spoon a “fork”, calling a spoon a “spood”  Nonsense words

Cranial nerves. For each, know numbers, names, site of origin (midbrain, pons, medulla oblongata), basic functions, whether it is sensory, motor, or both; know consequences of dysfunction (eg can’t smell, blind, etc.).

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12 pair of nerves – arise from brain – exit through foramina leading to muscles, glands and sense organs in head and neck Input and output ipsilateral except CN II and IV

Know trigeminal neuralgia and Bell palsy. (See Insight 14.4) • Trigeminal neuralgia (tic douloureux) – recurring episodes of intense stabbing pain in trigeminal nerve area (near mouth or nose) – pain triggered by touch, drinking, washing face – treatment may require cutting nerve • Bell palsy – disorder of facial nerve causes paralysis of facial muscles on one side – may appear abruptly with full recovery within 3-5 weeks...