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    Ch11 Ppt Lect Ch11 Ppt Lect Presentation Transcript

    • Chapter 11- Nervous System II PowerPoint Presentation to accompany Hole’s Human Anatomy and Physiology, 10 th edition , edited by S.C. Wache for Biol2064.01
    •   You are responsible for the following figures and tables : Review Fig. 10.7. Differentiate CNS and PNS general tasks. Compare Fig. 11.5 - Structure of the CNS - the brain and spinal cord. Compare Tab. 11.9 and Fig. 11.29 - Components of the PNS Fig. 11.1 , 11.2 - meninges. Fig. 11.3, 11.4 - CSF. TB, blue box, p. 368 Clinical Applications 11.1 - Spinal tap. Fig. 11.6 - Structure of the spinal cord. Fig. 11.7 - Define 'reflex arc‘. Fig. 11.8, 11.9 - Examples: Knee-jerk reflex, withdrawal reflex. Tab. 11.2 - Study the parts of a reflex arc. Fig. 11.15, Tab. 11.7 - CNS/ Brain structure - Read p.388-391, endocrine functions. Fig. 11.16 - Note fissures, sulci, gyri. Fig. 11.17, 11.18 - Areas of the cerebrum. Tab. 11.5 - Functions of the cerebral lobes. Fig. 11.25. PNS / Cranial nerves . Fig. 11.26. The vagus nerve # X, is important. Fig. 11.6.- CNS/ Spinal cord structure. Fig. 11.29 - PNS/ Spinal nerves - (see table in the attached lecture handout). Fig. 11.35 - ANS innervates smooth muscle and glands. Fig. 11.40 - sympathetic / parasympathetic nerves (see diagram in the attached lecture).
    •  
    •  
      • The meninges are membranes that protect the brain and the spinal cord
      • Dura mater: outermost layer, composed of tough, white, dense connective tissue
      • Arachnoid mater: thin, weblike membrane, subarachnoid space contains the cerebrospinal fluid
      • Pia mater: thin membrane with nerves and blood vessels, attached to the brain and spinal cord
      Meninges
    • Ventricles
      • The ventricles are a series of interconnected cavities
      • continuous with the central canal of the spinal cord which
      • transport the cerebrospinal fluid (CSF).
      • Lateral ventricles : first and second ventricles located in the cerebrum
      • Third ventricle: located in the midbrain, connected to the fourth ventricle via the cerebral aqueduct
      • Fourth ventricle: located in the brain stem
    • Cerebrospinal Fluid (CSF)
      • CSF is a clear fluid with high Na + and glucose
      • and low K + concentration, compared to other body
      • fluids.
      • Choroid plexuses are specialized capillaries of the pia mater, secrete cerebrospinal fluid.
      • 500 ml of CSF are secreted each day, but only 140 ml circulates, due to reabsorption through the arachnoid granulations.
    •  
    • Spinal Cord
      • It begins where nervous tissue leaves the cranium at the foramen magnum .
      • It tapers to a point near the first and second lumbar vertebrae . Below this is the filum terminale and the cauda equina.
      • It consists of 31 segments each giving rise to a pair of spinal nerves.
      • The cervical and lumbar enlargements give off nerves to the upper and lower limbs respectively.
    •  
    • Note dorsal and ventral roots.
      • Anterior median fissure and posterior median sulcus are grooves dividing the cord into right and left halves.
      • Gray butterfly is the inner gray matter consisting of interneurons.
      • Anterior and posterior horn are the wings. Between them is the lateral horn.
      • The gray commissure connects the wings.
      • The central canal contains CSF.
      • The white matter contains the myelinated nerve tracts.
      Spinal Cord
    • Reflex Arcs
      • Definition: The simplest nerve pathway is a reflex arc
      • which is autonomically controlled.
      • Reflexes whose arcs pass through the spinal cord are spinal reflexes .
      • Reflexes are autonomic and subconscious .
      • They help maintain homeostasis by controlling heart rate, breathing rate, etc.
      • They carry out automatic actions such as swallowing, sneezing, coughing, vomiting.
    • Note the pathway that the impulse travels. neuron neuron neuron neuron
    • Parts of a Reflex Arc
      • Receptor: sensitive to a specific change
      • Sensory neuron: transmits nerve impulse from the receptor to brain or spinal cord
      • Interneuron: processing, conducts impulse from sensory to motor neuron
      • Motor neuron : transmits nerve impulse from CNS out to effector (muscle or gland)
      • Effector : responds to stimulation and produces the reflex action
    • (Fig. 11.8) Note the pathway that the impulse travels. neuron neuron
    • Knee-jerk Reflex (Fig. 11.8)
      • The knee-jerk or patellar tendon reflex is a monosynaptic reflex involving only two neurons.
      • Striking the patellar ligament pulls the quadriceps femoris group and activates stretch receptors.
      • The sensory neurons activate interneurons which transmit the impulse to a motor neuron .
      • The motor neuron innervates the quadriceps femoris which contracts, extending the leg .
    • Note the pathway that the impulse travels. neuron neuron neuron neuron
    • Withdrawal Reflex (Fig. 11.9)
      • Occurs in response to touching something painful,
      • such as pricking the finger.
      • Sensory impulses are activated by pressure receptors in the skin and send a message to the spinal cord.
      • Interneurons are stimulated and synapse with motor neurons.
      • Motor neurons signal flexor muscles.
    •  
    • Crossed Extensor Reflex (Fig. 11.10)
      • Occurs with the withdrawal reflex. This reflex
      • is due to interneurons within the reflex center
      • of the spinal cord.
      • Flexors are inhibited on the affected side (ipsilateral).
      • Extensors are stimulated on the opposite side (contralateral) allowing body weight to be supported.
    • Spinal Cord Nerve Tracts (Fig. 11.11)
      • Spinal cord ascending and descending nerve
      • tracts:
      • Ascending and sensory - conduct impulses to the brain.
      • Anterior/Posterior spino-cerebellar tract
      • Anterior/ Lateral spino-thalamic tract
      • Medial reticulo-spinal tract
      • Descending and motor - conduct motor impulses from the brain to muscle and glands.
      • Anterior/ Lateral cortico-spinal tract
      • Anterior/ Lateral reticulo-spinal tract
    • Note decussation area.
    •  
      • Cerebral hemispheres : largest part
      • Corpus callosum: connects the hemispheres
      • Falx cerebri : dura mater separating the hemispheres
      • Gyri : convolutions or ridges in hemispheres
      • Sulci : shallow grooves between gyri
      • Fissures : deep grooves between gyri
      Cerebrum (Figure 11.15) Cerebral Lobes (Figure 11.16)
      • Lobes: frontal, parietal, temporal, occipital
      • Insula: the lobe in the center of the cerebral hemisphere that is situated deeply between the lips of the sylvian fissure -- called also central lobe, island of Reil
    • Note the lobes, fissures and sulci.
    •  
    • cerebellum
    • Brain Areas and Their Functions (Tab. 11.5) visual association area / perceptions occipital lobes Wernicke’s speech comprehension area; primary auditory / hearing association area temporal lobe gustatory area parietal lobe / along lateral sulcus primary olfactory area, Broca’s speech motor area frontal lobe concerned autonomic functions , limbic system hypothalamus integrates neurons for short-term memory thalamus is part of the diencephalon short-term memory processing, limbic system (emotions and motivation) lateral ventricle hippocampus / internal frontal lobe areas Function Region of Brain
    • Cerebral Functions (Fig. 11.16)
    •  
      • Broca’s area : motor speech area
      • Frontal eye field : voluntary eye movements
      • Motor areas: primary motor areas contain pyramidal cells and contain synapses with descending spinal tracts.
      • Sensory Areas : contain synapses from ascending tracts
      • Association Areas : regions rich in interneurons that are neither motor or sensory, but interconnect with each other and other centers.
      • General interpretative area (Wernicke’s area): complex thought processing
      Cerebral Functions
    • Cerebral Lobes (Figure 11.18)
    • Fig. 11.18
      • Frontal lobes : motor areas for voluntary skeletal muscles, association areas
      • Parietal lobes : sensory areas of temperature, touch, pressure, pain, speech association
      • Temporal lobes: sensory area for hearing, sensory association areas
      • Occipital lobes : sensory area for vision, visual association area
      Cerebral Lobe Functions
    • Hemisphere Dominance
      • Both hemispheres participate in basic functions.
      • One side is usually the dominant hemisphere for some functions.
      • For 90% of the population the left side is dominant for language-related activities of speech, writing, reading.
    • Coronal Cut - Left Cerebral Hemisphere (Fig.11.19)
    • Memory
      • Short-term memory : patterns of synapses that change;
      • no permanent synapses formed.
      • Lateral ventricle hippocampus / internal frontal lobe areas : short-term memory processing.
      • Limbic system (emotions and motivation): thalamus integrates neurons for short-term memory
      • Long-term memory :
      • patterns of synapses that remain unchanged.
    • Basal Nuclei
      • Basal Nuclei: masses of gray matter which consists of unmyelinated interneurons within the cerebral hemispheres
      • Hippocampus: a curved elongated ridge that is an important part of the limbic system , extends over the floor of the descending horn of each lateral ventricle of the brain, and consists of gray matter covered on the ventricular surface with white matter;
      • a region of the cerebral cortex that performs repeated stimulations to strengthen synapses.
      • Caudate nucleus, putamen, globus pallidus:
      • Relay motor impulses and produce the inhibitory neurotransmitter, dopamine
    • Diencephalon
      • Thalamus : gateway for sensory impulses
      • Hypothalamus : controls anterior pituitary which, in turn, controls effector glands
      • Posterior and anterior pituitary gland (controls a variety of effector endocrine glands) attached to the hypothalamus via the infundibulum
      • Optic tract and optic chiasma ( cranial sensory nerve II )
      • Mammillary bodies
      • Pineal gland releases melatonin which controls the biorhythm / circadian rhythm
    • Limbic System
      • Composed of portions of the cerebral cortex, thalamus, hypothalamus, basal nuclei, and other deep nuclei
      • Controls emotional experiences
      • Produces feelings of fear, anger, pleasure
      • Interprets sensory impulses of smell / olfactory sense
    • Brain Stem-Midbrain
      • Connects brain stem and spinal cord with the CNS
      • Cerebral peduncles : motor and sensory pathways
      • Red nucleus : posture reflexes
      • Corpora quadrigemina
        • Superior colliculi: visual reflexes
        • Inferior colliculi: auditory reflexes
    • Fig. 11.20 midbrain Medulla oblongata
    • Brain Stem-dorsal view (Fig. 11.20)
    • Brain Stem
      • Midbrain: the middle division of the three primary divisions of the adult brain that includes a ventral part with the cerebral peduncles and a dorsal part with the corpora quadrigemina and that surrounds the aqueduct of Sylvius connecting the third and fourth ventricles
      • Pons: sensory impulses relayed to brain, works with the medulla oblongata
      • Medulla Oblongata: ascending and descending tracts pass through; contains the cardiac center which controls heart rate; contains the vasomotor center which controls blood pressure; contains the respiratory center which controls rate, rhythm, depth of breathing;
      • corticospinal tract: any of four columns of motor fibers of which two run on each side of the spinal cord and which are continuations of the pyramids of the medulla oblongata : PYRAMIDAL TRACT : a : LATERAL CORTICOSPINAL TRACT
      • b : VENTRAL CORTICOSPINAL TRACT
      • Reticular Formation (shown in green) :
      • Extends from the superior portion of the spinal cord into the diencephalon
      • Activates the cerebral cortex into a state of wakefulness
      • Filters incoming sensory impulses and regulates motor activities
    • Cerebellum
      • Integrates sensory information concerning positions of body parts, coordination of skeletal muscle activity, maintain posture
      • Two lateral hemispheres separated by the falx cerebelli , a layer of dura mater; the Vermis connects the hemispheres
      • Cerebellar cortex : gray matter on outside
      • Arbor vitae : treelike pattern of white matter
      • Cerebellar peduncles: - inferior
        • - middle
        • - superior
    • Fig. 11.22 Arbor vitae- ‘ tree of life’
    • Peripheral Nervous System
      • Cranial nerves and spinal nerves:
      • Somatic Nervous System : nerves that connect CNS to skin and skeletal muscles
      • Autonomic Nervous System : nerves that connect CNS to viscera, smooth muscle nad glands.
    • Fig. 11.24 Epineurium : outer layer of connective tissue Perineurium : sleeve of looser connective tissue surrounding a fascicle Endoneurium : loose connective tissue surrounding each nerve fibers
      • Twelve pairs of nerves which originate from brain stem and cerebrum
      • Pass through foramen magnum in the skull
      • Mixed nerves and special senses; some motor nerves
    • Cranial Nerves
      • I: Olfactory : sense of smell
      • II: Optic : sense of vision
      • III: Oculomotor : eye movement, focusing
      • IV: Trochlear : eye movement
      • V: Trigeminal : mixed nerve - ophthalmic: sensory: accessory eye structures
        • - maxillary: sensory: teeth, gum, lip, face
        • - mandibular: sensory: scalp, jaw, teeth, lip
      • VI: Abducens : eye movement
      • VII: Facial : mixed: taste, facial expression
      • VIII: Vestibulocochlear - vestibular branch: sense of equilibrium
        • - cochlear branch: sense of hearing
      • IX: Glosspharyngeal : mixed: pharynx
      • X: Vagus: mixed: speech, swallowing, autonomic nervous system to viscera
      • XI: Accessory : - cranial branch: motor to pharynx and larynx
        • - spinal branch: motor to neck and back
      • XII: Hypoglossal : tongue movement
    • Spinal Nerves
      • Thirty-one pairs of 2-inch long mixed nerves which
      • originate from the spinal cord and provide communication
      • between the spinal cord and the peripheral nerves which
      • transport impulses to the periphery of the human
      • body.
      • AM-PS:
      • Ventral ( a nterior) root : m otor
      • Dorsal ( p osterior) root : s ensory; dorsal root ganglion = cell bodies of sensory nerves
      • Cervical nerves: 8 pairs, C1-C8
      • Thoracic nerves: 12 pairs, T1-T12
      • Lumbar nerves: 5 pairs, L1-L5
      • Sacral nerves: 5 pairs, S1-S5
      • Coccygeal nerves: 1 pair, C0
      Fig. 11.30
    • Plexuses
      • Cervical : first four cervical nerves [C1-C4]
      • Brachial : lower four cervical nerves and first thoracic nerve [C5-C8 and T1]
      • Lumbosacral : last thoracic nerve and lumbar, sacral, and coccygeal nerves [T12-S5]
      PNS - Autonomic Nervous System
      • Functions independently, involuntary / subconscious control
      • Controls visceral activities by regulating smooth and cardiac muscles and glands
      • Regulates heart rate, blood pressure, breathing, body temperature and other homeostatic mechanisms
      • Responds to stress
    • Note : nerve cells are neurons. Note the spelling !!! Also note the pathway that the impulse travels !
    • Sympathetic Division of Motor Nerves Fig. 11.37 – note the dorsal and ventral roots.
    • Fig. 11.36 – note the meninges, dorsal and ventral roots. Note that the spinal nerves are mixed function nerves [AM-PS].
    • Parasympathetic Division of Motor Nerves
      • Fibers arise from brain stem and sacral spinal cord.
      • The vagus nerve (X) carries 75% of the parasympathetic fibers.
      • Fibers travel to terminal ganglia close to viscera.
      • Postganglionic fibers travel to specific muscles or glands.
    • Neurotransmitters (Tab. 11.10)
      • Acetylcholine functions to maintain homeostasis.
      • Preganglionic fibers are cholinergic and secrete acetylcholine :
      • Preganglionic sympathetic fibers of the ANS arise from the thoracic and lumbar regions of the spinal cord.
      • Preganglionic parasympathetic fibers of the ANS arise from the brain and sacral region of the spinal cord.
      • Postganglionic parasympathetic and sympathetic fibers of sweat glands are also
      • cholinergic .
      • Norepinephrine and epinephrine function to
      • respond to stress
      • All other postganglionic sympathetic fibers are adrenergic and secrete norepinephrine
    • Fig. 11.38 – ANS preganglionic sympathetic fibers arise from the thoracic and lumbar regions of the spinal cord.
    • Fig. 11.40 – ANS preganglionic parasympathetic fibers arise from the brain and sacral region of the spinal cord.
    • Neurotransmitter Receptors
      • Acetylcholine binds to two cholinergic receptors:
        • muscarinic receptors: effector cells at parasympathetic postganglionic terminals
        • nicotinic receptors: synapses between pre- and postganglionic fibers and at neuromuscular junctions of skeletal muscles
      • Epinephrine and norepinephrine bind to two adrenergic receptors:
      • - alpha and beta receptors, which give different
      • responses at the target organ
    • Fig. 11.40 – note that most sympathetic fibers in the thoracic and lumbar regions are adrenergic and secrete norepinephrine / epinephrine
      • Programmed cell death ( apoptosis ) begins at birth and is a natural control point within the cell cycle (G o , G 1 , S, G 2 , mitosis/meiosis, apoptosis or G o ).
      • Loss of neurons does not always mean loss of function.
      • Signs of aging: fading memory, slowed responses and reflexes, and other changes.
      Life-Span Changes