OVERVIEW OF THE NERVOUS SYSTEM FELIX K. NYANDE

OUTLINE The nervous system Divisions Cells Central nervous system Peripheral nervous system Assessment

NERVOUS SYSTEM Highly specialised system responsible the control and integration of the body’s many activities. Divisions: central and peripheral NS – Central: brain and spinal cord – Peripheral: somatic and autonomic – Autonomic: sympathetic and parasympathetic

Central Nervous System (CNS) Brain Spinal Cord Peripheral Nervous System (PNS) Sensory Neurons Motor Neurons Somatic Nervous System voluntary movements via skeletal muscles Somatic Nervous System voluntary movements via skeletal muscles Autonomic Nervous System organs, smooth muscles Autonomic Nervous System organs, smooth muscles Sympathetic - “Fight-or-Flight” responses Sympathetic - “Fight-or-Flight” responses Parasympathetic - maintenance Parasympathetic - maintenance The Nervous System

Divisions of the autonomic nervous system

Cells of Nervous System Made up of two types of cells – Neurons – Neuralgia :

Neurons Come in different sizes and shapes. Characteristics Excitability: ability to generate a nerve impulse Conductivity: ability to transmit the impulse to other portions of the cell Ability to influence other neurons, muscle cells and glandular cells by transmitting impulses to them. Parts: body axon dendrites

Neurons Axon of another neuron Cell Body Dendrites Axon Myelin Sheath Dendrites of another neuron

Sensory (Afferent) vs. Motor (Efferent) e.g., skin e.g., muscle Gray’s Anatomy sensory (afferent) nerve motor (efferent) nerve Neurons that send signals from the senses, skin, muscles, and internal organs to the CNS Neurons that transmit commands from the CNS to the muscles, glands, and organs

Neuroglia Also known as glial cells. Provide support, nourishment and protection to neurons. Constitute almost half of brain and spinal cord mass 5-10 times more numerous than neurons.

CENTRAL NERVOUS SYSTEM The spinal cord: Continuous with the brain and exits from the cranium through the foramen magnum. The brain Divided into three components – Cerebrum – Brainstem – Cerebellum

Cerebrum Divided into left and right hemispheres Both hemispheres can further be divided into four major lobes – Frontal: controls higher cognitive function, memory retention, voluntary eye movement, voluntary motor movement and expressive speech – Temporal : contains the Wernicke’s area responsible for receptive speech and for integration of somatic, visual, and auditory data. – Parietal : sensory cortex, controlling and interpreting spatial information – Occipital : processing of sight Basal ganglia, thalamus, hypothalamus and limbic system located in the cerebrum

Brainstem Includes the midbrain, pons and medulla Reticular formation is located here Centres concerned with respiration, vasomotor and cardiac functions located here Contains centres for sneezing, coughing, hiccupping, vomiting, sucking and swallowing

Cerebellum Located in the posterior part of the cranial fossa under the occipital lobe. Main function is coordination of voluntary movement and maintenance of trunk stability and equilibrium

PERIPHERAL NERVOUS SYSTEM Includes all the neuronal structures that lie outside the CNS. Consists of the spinal and cranial nerves; their associated ganglia and portions of the ANS

Cranial nerves I- olfactory II-optic III-occulomotor IV-trochlear V-trigeminal VI-abducens VII-facial VIII-vestibulocochlear IX-gastropharyngeal X-vagus XI-accessory XII-hypoglossal

Autonomic nervous system Controls involuntary functions of cardiac muscles, smooth muscles and glands. SNS and PSNS function together to maintain a relatively balanced internal environment

Protective structures Meninges Skull Vertebral column

Assessment of the CNS Subjective data – History: past, family, present, etc – Life style: substance abuse, nutrition, physical and recreational activities, use of safety devices, control of chronic diseases, etc Objective data – Physical examination: mental status, function of CNs, motor function, cerebellar function, sensory function, and reflex function.

Diagnostic studies CSF analysis: composition, appearance, colour, Lumbar puncture Radiologic studies – Cerebral angiography: using contrast dyes – Skull and spine x-rays – CT scan – MRI EEG USG