Nervous System

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Presentation Transcript

Nervous System: 

Nervous System Basic Structure & Function

Functions:: 

Functions: Sensory – detect changes Integrate – make decisions Motor - respond

General Structure: 

General Structure

Structure - The Neuron: 

Structure - The Neuron Cell body – contains organelles Dendrite – receives information Axon – transmits information Difficult to culture Key to treatment of disease

Classifying Neurons: 

Classifying Neurons Structure Bipolar Unipolar Multipolar Function Sensory Interneurons motor

Bipolar: 

Bipolar One axon One dendrite Found in eyes, ears, nose

Unipolar: 

Unipolar One fiber extends from cell body Fiber then divides into Dendrite Axon Cell body found outside of CNS ganglia

Multipolar: 

Multipolar Many fibers arise from cell body One is an axon Many dendrites Cell bodies found within CNS

Neurons based on function:: 

Neurons based on function:

Neuroglia (glial cells): 

Neuroglia (glial cells) Central Nervous System Astrocytes Oligodendrocytes Microglia Ependymal cells Peripheral Nervous System Schwann cells

Schwann cells: 

Schwann cells Wrap around some axons Form myelin sheath Assists in transmission of impusles Found in PNS

Astrocytes: 

Astrocytes Star-shaped Connect neurons and blood vessels Transfer nutrients Support/scaffold Aid in metabolism of substances

Oligodendrocytes: 

Oligodendrocytes Star shaped Smaller than astrocytes Form myelin sheath around multiple axons Found in CNS

Microglia: 

Microglia Relatively small Few processes Support neurons in CNS Phagocytize bacteria and debris

Impulse conduction: 

Impulse conduction Movement of Na and K ions causes electrical current Stimulates adjacent membranes in wave-like fashion

Impulse conduction: 

Impulse conduction Myelinated faster than unmyelinated Increase in diameter increases speed High K+ = convulsions Low K+ = paralysis Anesthesia blocks flow of ions – no transmission of pain

The Synapse: 

The Synapse Impulse travels from dendrite To cell body To axon (presynaptic neuron) Releases neurotransmitters Neurotransmitters diffuses across synaptic cleft Influences the next neuron (postsynaptic) or effector

Neurotransmitters: 

Neurotransmitters Can have excitatory or inhibitory effects Summation of effects determines if impulse is triggered in next neuron Key to many nervous system disorders

The NerveIs it an organ?: 

The Nerve Is it an organ?

Types of Nerves: 

Types of Nerves Sensory Carry impulse to CNS Motor Carry impulse to effector (muscle or gland) Mixed Contains both types of fibers

Nerve Pathways: 

Nerve Pathways Reflex Arc Simple Components Receptor Sensory neuron Interneuron(s) Motor neuron Effector Nerve Tracts Bundles of nerve fibers Ascending (sensory) Descending (motor)

Nerve Tracts: 

Nerve Tracts

Reflexes: 

Reflexes Automatic response to stimuli Maintains homeostasis Heart rate, breathing rate, blood pressure, digestion, swallowing, sneezing, coughing, and vomiting Used for diagnosis

Reflexes: 

Reflexes

Meninges: 

Meninges Lie between bony coverings & nervous tissue Protect, nourish Dura mater Arachnoid Mater Pia Mater

Dura Mater: 

Dura Mater Outermost Tough fibrous connective tissue Blood vessels Nerves Forms partitions between lobes Continues into spinal canal

Slide29: 

Epidural space Subdural hematoma

Arachnoid Mater: 

Arachnoid Mater Thin Weblike No blood vessels Subarachnoid space Cerebrospinal fluid

Pia Mater: 

Pia Mater

Spinal Cord: 

Spinal Cord From foramen magnum To second lumbar vertebrae Cervical enlargement – to upper limbs Lumbar enlargement – to lower limbs

Spinal Nerves: 

Spinal Nerves 31 spinal cord segments = 31 pair of spinal nerves

Cross section of spinal cord: 

Cross section of spinal cord Core of gray matter Anterior, posterior and lateral horns Gray commissure Central canal (CSF) Some cell bodies of motor neurons Mostly interneurons Surrounded by white matter Mylenated nerve tracts

Function of Spinal Cord: 

Function of Spinal Cord Conducting nerve impulses Two way communication between brain and body parts Center for spinal reflexes

The Brain: 

The Brain 100 billion multipolar neurons Four portions Cerebrum Diencephalon Brainstem Cerebellum

Structure of cerebrum: 

Structure of cerebrum Cerebral hemispheres Corpus callosum Lobes (frontal, parietal, temporal and occipital) Surface Convolutions (gyri) Grooves (sulci and fissures) Cortex – gray matter (cell bodies) White matter – myelinated axons

Functions of Cerebrum: 

Functions of Cerebrum Provides higher brain functions Interprets sensory impulses Initiates voluntary movements Memory Reason Intelligence Personality

Functions of Cerebrum: 

Functions of Cerebrum Motor areas Sensory areas Association areas

Hemisphere Dominance: 

Hemisphere Dominance Controls the ability to use and understand language 90% left hemisphere dominant

Diencephalon: 

Diencephalon Thalamus Relay station for sensory impulses General awareness of sensations Hypothalamus Maintains homeostasis Visceral activities Endocrine system communication Limbic system (thalamus & hypothalamus) Controls emotional experience and expression (fight or flight)

Brainstem – connects cerebrum to spinal cord: 

Brainstem – connects cerebrum to spinal cord Midbrain Pons Medulla Oblongata

Cerebellum: 

Cerebellum