Nervous System Structure and organization of the nervous system CHAPTER 8 Structure and organization of the nervous system Functions of different parts of the nervous system Tools to study nervous system Dr. Hameed Al-Sarraf Dept. Physiology hameed@hsc.edu.kw

Nervous System

Nervous System Peripheral Nervous System (PNS) Central Nervous System (CNS) Brain: Memory Emotions Thoughts Body regulation and control Peripheral Nerves: Afferent (sensory) Efferent (motor) Spinal Cord: Place for many nerve pathways, Control of reflex activities

Relations Between CNS and PNS Sensory Receptors from: Skin, deep tissue, Eyes, ears, etc Interneurones Motor Effectors: Muscles and Glands

CNS (Brain and Spinal Cord)

Development of CNS PNS CNS

Cerebrospinal Fluid (CSF) - Fluid surrounding the brain and spinal cord. This fluid is mainly secreted by a structure in the brain called choroid plexus. CSF flows around the brain and in the cavities inside the brain (ventricles). CSF helps brain float in the skull reducing the weight of the brain by 30 folds. Choroid Plexus CSF

Brain Ventricles

Brain and its Divisions Brain is encased in cranial cavity, its divided into six parts: 1- Cerebrum 2- Diencephalon 3- Mesencephalon 4- Cerebellum 5- Pons 6- Medulla oblongata

Cerebrum - The largest portion of the brain (80%). Responsible for higher mental functions Consist of right and left hemispheres. Hemispheres are connected by a large fiber tract called corpus callosum.

Cerebral cortex - Outer layer of cerebrum is called cerebral cortex gray matter and white matter - Folds and grooves in cortex are called convolusions: Folds = Gyri (gyrus = single fold), Grooves = sulci (sulcus = single groove). - Deep sulci also called: Fissure. - Fissures divide cerebral cortex into 5 lobes: 1- frontal 2- pareietal 3- temporal 4- occipital, 5- insula

Cerebral cortex - Outer layer of cerebrum is called cerebral cortex gray matter and white matter - Folds and grooves in cortex are called convolusions: Folds = Gyri (gyrus = single fold), Grooves = sulci (sulcus = single groove). - Deep sulci also called: Fissure. - Fissures divide cerebral cortex into 5 lobes: 1- frontal 2- pareietal 3- temporal 4- occipital, 5- insula

Functions of the Cerebral lobes Frontal : Voluntary motor control, Speech, Personality, Higher intellectual processes (planning, concentration & decision making). Parietal : Sensory somatesthetic sensation, speech. Temporal : Interpretation of Auditory sensation, storage (memory) of auditory and visual experiences. Occipital : Vision, Movements of eyes. Insula : Memory, sensory (pain) and visceral integration.

Motor and Sensory areas of Cerebral cortex Postcentral Gyrus Precentral Gyrus

Tools for Studying the brain 1- Visualizing the Brain : a) X-ray Computed Tomography (CT-Scan) b) Positron-Emission Tomography (PET-Scan) c) Magnetic Resonance Imaging (MRI) 2- Detection of Electrical Waves : Electroencephalogram (EEG) EEG waves = alpha, beta, theta, and delta

PET- Scanner CT- Scanner MRI

Visualizing the Brain CT-Scan PET-Scan MRI

Recording EEG

EEG Waves Alpha waves- (10-12 cycles/sec) recorded in parietal and occipital regions while awake & relaxed. Beta waves- (13-25 cycles/sec) recorded in frontal lobs. Produced by visual stimuli and mental activity. Theta waves- ( 5-8 cycles/sec) recorded in temporal & occipital lobs. Common in infants (newborn) In adults it’s a sign of emotional stress. Delta waves- (1-5 cycles/sec) recorded in general pattern of cerebral Cortex. Observed during sleep. If seen in Awake person it’s a sign of damage.

Basal Nuclei Precentral Gyrus Nucleus = a collection of neuron cell bodies in the CNS. Basal nuclei = masses of gray matter (neuron cell bodies) located deep in white matter of cerebrum. Function of basal nuclei = Control of voluntary movements of body. Precentral Gyrus

Decussation = crossing over of fibers Each cerebral hemisphere controls movements (motor fibers) of the opposite side of the body. Also each cerebral hemisphere receives sensation (sensory fibers) from the opposite This is due to decussation (crossing over) of fibers. Both cerebral hemipheres also receive information from both sides of the body this is due to cerebral hemispheres are connected and communicated with each other by a large tract of fibers called corpus callosum.

Language Aphasias = speech and language disorders caused by damage to the brain (head injury/stroke) Broca’s aphasia – weakness in right arm and right side of face. They understand Speech but they are slow talkers and their speech is poorly articulated. Understand A sentence but have difficulty repeating it. Wernicke’s aphasia – rapid and fluid speech but without meanings (word salad). Comprehesion (written and spoken) is also impaired. Conduction aphasia- damage to arcuate faciculus which connects Broca and Wernicke. Fluent but nonsensical speech like Wericke’s aphasia. Inflect Angular gyrus damage- its an area between parietal, temporal and occipital lobs. Difficulty in writting and reading, but spoken language is understood.