CNS AND PNS

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CNS AND PNS Copyright © 2006 by John Wiley & Sons, Inc.

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17-5 Spinal Cord Pathway for sensory input to brain and motor output from brain. Long (46cm), cylindrical, located in the vertebral canal. Foramen magnum to L1, L2 vertebrae. Thick in Cervical and Lumber region. Lower end has bunch of nerves called “Cauda Equina”. 31 Pair of nerve on either side.

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17-18 Reflex is an involuntary response to a stimulus, that is, an automatic action stimulated by a specific change of some kind. Spinal cord reflexes are those that do not depend directly on the brain, although the brain may inhibit or enhance them. Types of reflexes Unconditioned or inborn reflex (can not be ultered) a) Superficial reflex- Stimulus received by skin/ eye. b) Deep Reflex- received by tendon of muscle Knee jerk, ankle jerk. c) Visceral Reflex- by visceral organ GIT, Cerculatory etc.

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17-19 2. Conditioned/ Aquired Reflex:- - Modified by practice 1. Meat + Bail Salivation in Dog Only Bail Salivation in dog Sight or smell of food During infancy pronounsation is deficult Now Easy

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17-20 Reflex Arc: A reflex arc is the pathway that nerve impulses travel when a reflex is elicited, and there are five essential parts: 1. Receptors—detect a change (the stimulus) and generate impulses. 2. Sensory neurons—transmit impulses from receptors to the CNS. 3. Central nervous system—contains one or more synapses (interneurons may be part of the pathway). 4. Motor neurons—transmit impulses from the CNS to the effector. 5. Effector—performs its characteristic action.

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17-21 Types of Reflex Arc: Monosynaptic: One Synapse Disynaptic: Two Synapse One between afferent and intermidiate Another between efferent and intermidiate Polysynaptic: Involve many intermidiate and efferent

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THE BRAIN Copyright © 2006 by John Wiley & Sons, Inc.

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The Brain: In adult weight is 1.3Kg Brain has three basic function Detection and processing of sensory informations Orientation and control of movement by muscle Brain is seat of conciousness and mind is reflection of its activity. Mainly divided into three Parts Fore-brain: Cerebrum, Basal nuclei, Limbic system, Reticular formation, Thalamus, Hypothalamus. Mid-brain: Tectum, Tegmentum, Cerebral pendulum, Carpus stratum, Substantia nigra, Red nucleus etc. Hind –brain: Cerebellum, Pons, Medulla oblongata

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17-24 MEDULLA PONS MIDBRAIN/ Mesencephalon CEREBELLUM HYPOTHALAMUS Diencephalon THALAMUS CEREBRUM Frontal Lobes Parietal Lobes Temporal Lobes Occipital Lobes The brain consists of many parts that function as an integrated whole. The major parts are

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17-27 I. VENTRICLES The ventricles are four cavities within the brain: Two lateral ventricles, the third ventricle, and the fourth ventricle Each ventricle choroid plexus forms cerebrospinal capillary fluid (CSF) from network. blood plasma CSF = Tissue fluid of CNS

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17-29 MEDULLA From the spinal cord to the pons Anterior to the cerebellum. We cannot survive without the medulla. Why? Functions are (vital) Regulate Cardiac centers heart rate vasomotor centers diameter of blood vessels Respiratory centers breathing Reflex centers for coughing sneezing, swallowing vomiting.

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17-30 III. PONS Bulges anteriorly from the upper part of the medulla Function Two respiratory centers with medulla to produce a normal breathing rhythm ii. Bridge PONS Medulla brain.

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17-31 MIDBRAIN / Mesencephalon Extends from the pons to the hypothalamus Encloses the cerebral aqueduct (connects III and IV ventricles)

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1.Cerebral pendulum= anterior part having paired bundle of axon 2. Tectum= posterior part contain four rouded elevation i) Two superior colliculi (for visual activity) ii) Two inferior colliculi (for auditory activity) 3. Lt. and Rt. Substantia nigra = Neurons originate from this part releases dopamine. Loss of this neuron causes parkinson disease. 4. Lt. & Rt. Red nuclei= has blood and iron containing pigments hence red in colour. Axon from cerebellum and cerebral cortex form synapses in the red nucei. Thus controle some voluntory movement of limb.

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17-33 Functions: Several reflexes are integrated in the midbrain eg. 1)visual, 2)auditory reflexes & 3) righting reflexes 1) Insect flying toward you you automatically move (the head or body) quickly downwards or away or twist away; this is a visual reflex, as is the coordinated movement of the eyeballs. 2) Turning your head (ear) to a sound is an example of an auditory reflex. 3)Righting reflexes, those that keep the head upright and maintain balance or equilibrium.

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17-34 V. CEREBELLUM Posterior & Separated from the medulla and pons by the fourth ventricle Inferior to the occipital lobes of the cerebrum. The functions of the cerebellum are concerned with movement. Include Coordination of muscle tone Regulation of muscle tone Endpoint of movements the maintenance of posture and equilibrium.

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17-35 Transverse fissure along with tentorium cerebelli (Support) Vermis (Central constricted area) Cerebellar hemispheres i. Two anterior lobe ii. Two posterior lobe 3. Flocculonodular lobe (on inferrior surface) 4. Cerebellar cortex i. folia (gray matter) ii. Arbor vitae(deep to gray tracts of white matter) iii. Cerebellar nuclei (again deep gray matter has axon carring impulses to other brain center) 5. Cerebellar penduncles (bundle of white matter) i. Superior cerebellar penduncles ii. Middle cerebellar penduncles iii. Inferior cerebellar penduncles

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17-37 All are involuntary: permit brain to work without being overburdened. 1. Decide to pick up a pencil, for example, the impulses for arm movement come from the cerebrum. The cerebellum then modifies these impulses so that your arm and finger movements are coordinated, and you pick up a pencil. 2. Sensory functions eg. ? Close your eyes someone places a tennis ball in one hand and a baseball in the other, could you tell which was which? Ans: Yes. By the “feel” of texture and the weight

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17-38 VI. HYPOTHALAMUS Located superior to the pituitary gland Inferior to the thalamus The hypothalamus is a small area of the brain with many diverse function.

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17-39 Functions: 1. Production of antidiuretic hormone (ADH) and Oxytocin 2. Production of releasing hormones (also called releasing factors) 3. Regulation of body temperature by- a) Sweating in a warm environment or b) Shivering in a cold environment 4. Regulation of food intake - by fullness, and we tend to stop eating. 5. Integration (controle) of the functioning of the autonomic nervous system, 6. Stimulation of visceral responses during emotional situations. 7. Regulation of body rhythms such as secretion of hormones, sleep cycles, changes in mood, or mental Alertness i.e. circadian rhythms

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17-40 VII. THALAMUS Superior to the hypothalamus Inferior to the cerebrum. Third ventricle is a narrow cavity that passes through both the thalamus and hypothalamus.

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17-41 Many of the functions of the thalamus are concerned with sensation. 1)Sensory impulses to the brain (except those for the sense of smell) follow neuron Holding a cup of hot coffee generates impulses for heat, touch and texture, and the shape of the cup. 2) Unpleasant ones such as pain, are believed to be felt by the thalamus but can not localize the sensation (cerebrum are required for localization) 3) Suppress unimportant sensations If you are reading an enjoyable book, you may not notice someone coming into the room. 4) Parts of the thalamus are also involved in alertness and awareness. For these functions, as for others, the thalamus works very closely with the cerebrum.

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17-42 Cerebrum

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The Brain: In adult weight is 1.3Kg Brain has three basic function Detection and processing of sensory information Orientation and control of movement by muscle Brain is seat of consciousness and mind is reflection of its activity. Mainly divided into three Parts Fore-brain: Cerebrum, Basal nuclei, Limbic system, Reticular formation, Thalamus, Hypothalamus. Mid-brain: Tectum, Tegmentum, Cerebral pendulum, Carpus stratum, Substantia nigra, Red nucleus etc. Hind –brain: Cerebellum, Pons, Medulla oblongata

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17-44 MEDULLA PONS MIDBRAIN/ Mesencephalon CEREBELLUM HYPOTHALAMUS Diencephalon THALAMUS CEREBRUM Frontal Lobes Parietal Lobes Temporal Lobes Occipital Lobes The brain consists of many parts that function as an integrated whole. The major parts are

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17-47 Cerebrum

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17-48 VIII. Cerebrum Largest part of the human brain Two hemispheres separated by the longitudinal fissure At the base of this deep groove is the corpus callosum, has a band of 200 million neurons that connects the right and left hemispheres. Each hemisphere has lateral ventricle.

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17-49 Cerebral Cortex The surface of the cerebrum is gray matter called the cerebral cortex. Internal to the gray matter is white matter which connect the lobes of the cerebrum to one another and to all other parts of the brain. Cerebral cortex is folded Folds are called convolutions or gyri and the grooves between them are fissures or sulci Permits the presence of millions more neurons in the cerebral cortex.

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17-50 Animal such as a dog or cat does not have this extensive folding. This difference enables us to read, speak, write poetry and songs, So many other “human” things that dogs and cats cannot do.

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17-51 Cerebrum is divided into lobes that have the same names as the cranial bones Each hemisphere has a frontal lobe, parietal lobe, temporal lobe and occipital lobe

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17-52 Central Sulcus (frontal & parital) Precentral gyrus (contain motor area) Postcentral gyrus (somatosensory area) Lateral Cerebral sulcus/ fissure(frontal and temporal) Perito- occipital sulcus (parital occipital) Insula

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17-53 Cerebral White Matter Cerebral white matter contain myelinated axon in three types of tracts (Zone/ Area) Association Tracts Conduct nerve impulses between gyri in the same hemisphere 2. Commissural Tracts Conduct nerve impulses gyri of one hemisphere to corresponding gyri in the other cerebral hemisphere. Three important tracts are: Corpus collasum Anterior commissure Posterior commissure 3. Projection Tracts Conduct nerve impulses from Crebrum to lower part of brain or wise versa.

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17-55 ALL THE BEST FOR MID-SEM

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17-56 EEG Limbic System Reticular Activation and Inhibiting System PNS (Cranial &Spinal Nerve) Physiology and Functions of ANS CNS Disorders

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Limbic System Encircling the upper part of the brain stem and the carpus callosum

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The main component of limbic systems are 1. Limbic lobe includes a. cingulate gyrus lie above the corpus callosum, b. parahippocampal gyrus which is in the temporal lobe bellow c. hippocampus is a portion of the parahippocampal gyrus dental gyrus lie between hippocampus &parahippocampal gyrus amygdala located close to to the tail of the caudate nucieus

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Septal nuclei located within septal area formed by carpus callosum and cerebral gyrus. Mammillary bodies of the hypothalamus two round masses close to the midline near the cerebral pendulum Anterior nucleus and medial nucleus of thalamus Olfactory bulb Fornix, stria terminalis, stria medullaris, medial forebrain bundle and mammillothalamic tract.

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Functions Called as “Emotional Brain” because play a primary role in emotions (pleasure, pain, docility (respect), affection (friend), fear and anger) Olfactory and memmory A person whose amygdala is removed or damaged, fail to recognize fearful expression in others or to express fear in appropriate situations.

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Reticular Activation and Inhibiting System It is ill defined mass of nerve cells that passes through the upper portion of the spinal cord, brain stem and diencephalon. The reticular activating system (RAS) is an area of the Brain (including the reticular formation and its connections) responsible for regulating arousal and sleep-wake transitions. Function 1. Attention The reticular activating system also helps mediate transitions from relaxed wakefulness to periods of high attention. There is increased regional blood flow (presumably indicating an increased measure of neuronal activity) in the midbrain reticular formation (MRF).

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2. Regulating Sleep-Wake Transitions Main is to modify thalamic and cortical function such that Electroencephalogram (EEG). The physiological change from a state of deep sleep to wakefulness is reversible and mediated by the RAS. Inhibitory influence from the brain is active at sleep onset, likely coming from area of the hypothalamus. During sleep, neurons in the RAS will have a much lower firing rate; BUT they will have a higher activity level during the waking state. REGULATION low frequency inputs (during sleep/ Descending RAS) from the RAS to the area of the hypothalamic neurons result in an excitatory influence and higher activity levels (awake/ Ascending RAS) will have inhibitory influence.

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Basal Ganglia Three nuclei within each hemisphere collectively termed as basal ganglia. Two of the basal ganglia are side by side (collectively called as lentiform nucleus) a. Globus pallidus (closure to thalamus) b. putamen (closer to cerebral cortex) Third basal ganglia is caudate nucleus (has large head and smaller tail) Together lentiform and caudate nuclei are known as Corpus striatum.

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Three nuclei within each hemisphere collectively termed as basal ganglia. Two of the basal ganglia are side by side (collectively called as lentiform nucleus) a. Globus pallidus (closure to thalamus) b. putamen (closer to cerebral cortex) Third basal ganglia is caudate nucleus (has large head and smaller tail) Together lentiform and caudate nuclei are known as Corpus striatum.

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FUNCTION Receive input from the cerebral cortex Provide output back to motor area of cerebral cortex Help in initiating and terminating movement of body Suppress unwanted movement and regulate muscle tone

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EEG Brain generate millions of nerve impulses (A P). This electrical signals are called as brain waves. Brain waves generated in cerebral cortex can be detected by sensors called as Electrodes placed in forehead and scalp. Record of such waves are called as Electroencephalogram. EEG is important in studying normal brain functioning. Changes occur in diseases like epilepsy (to seize), tumors (neoplasm), hematomas (collection of blood outside the blood Vessels), metabolic abnormality. It is also used to confirm that brain death occur or not.

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Four types of brain waves

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Alpha Waves: Frequency is 8-13 cycles per second. Present in all individuals when they are awake and resting with their closed eyes Not present during sleep. 2. Beta Waves: 14-30 Hz Appears during sensory input and mental activity. 3.Theta Waves: 4-7 Hz During emotional stress in children and adults 4. Delta Waves: 1-5 Hz During deep sleep in adult but if present in an awake adult then indicate brain damage. But normal in awake infants.

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CRANIAL AND SPINAL NERVE

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SPINAL NERVE

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CRANIAL NERVE