Neural Tissue The nervous system includes all the neural tissue in the body.

Structure of the nervous system

The Nervous System Central Nervous System Peripheral Nervous System Afferent Efferent Brain Spinal Cord Central Nervous System - brain, spinal cord, blood vessels, connective tissue PNS- delivers sensory information to the CNS Somatic Autonomic Sympathetic Parasympathetic

Peripheral Nervous System Afferent - bring sensory Efferent - carry commands

Efferent Division Somatic - skeletal muscle contractions (voluntary) & involuntary reflexes Autonomic (visceral motor system) -Involuntary (smooth muscles, cardiac muscle & glandular secretions)

Autonomic Nervous System Parasympathetic - nonstressful rest & digest Sympathetic – stressful fight or flight Antagonistic effects

Functional & Structural unit of the nervous system Neuron Functional & Structural unit of the nervous system

Multipolar Neuron Nissl bodies - Rough ER & free ribosomes dendrites perikaryon dendritic spines dendrites nucleus axon telodendria Nissl bodies mitochondria axon hillock Initial segment of axon telodendria axon Nissl bodies - Rough ER & free ribosomes perikaryon - cytoplasm Golgi apparatus synaptic terminals neurofilaments nucleolus nucleus Multipolar Neuron

Vocabulary dendrites - typically highly branched, carry messages axon - propagates an electrical impulse away from the cell body initial segment - base of an axon

Vocabulary cont. axon hillock - thickened region soma - cell body, houses organelles but lack centioles telodendria - fine extensions off the axon synaptic terminal - ends of the telodendria

Structural Classification of Neurons axonic - small, located in brain & special sense organs Bipolar - rare, special sense organs (sight, smell, hearing) Unipolar - most sensory neurons in PNS - longest is tip of toes to spinal cord multipolar - most common in CNS, all motor neurons, longest to muscles of toe anaxonic neuron bipolar neuron unipolar neuron multipolar neuron

Functional Classification of Neurons Sensory neurons (afferent) - from sensory receptors to CNS somatic sensory neurons - monitor the outside world & our position in it visceral sensory neurons - monitor internal conditions & the status of the organs

Sensory receptors proprioceptors interoceptors exteroceptors proprioceptors - monitor the position & movement of skeletal muscles & joints interoceptors - digestive, respiratory, cardiovascular, urinary, reproductive systems & taste, pain exteroceptors - touch, temp, pressure sensations, sight, smell and hearing proprioceptors interoceptors exteroceptors

Functional Classification of Neurons Motor Neurons (efferent) - carry instructions from the CNS to peripheral effectors

Functional Classification of Neurons Interneurons (association) - outnumber all other types mostly in brain & spinal cord situated between sensory & motor neurons

Cerebral Spinal Fluid (CSF) and the brain & spinal cord Ependymal Cells line the central canal & ventricles which house the brain & spinal cord, creates a barrier between the Cerebral Spinal Fluid (CSF) and the brain & spinal cord

Astrocytes Maintain the blood-brain barrier Create a 3-D framework for the CNS Repair damaged nerve tissue Guide neuron development Control the interstitial environment Maintain - isolates CNS from general circulation to keep out hormones & other chemical, form blankets around capillaries, Repair - structural repair to stabilize the tissue & prevent further damage, Guide - direct growth & interconnection in the embryonic brain, Control - regulate concentration of sodium ions & potassium ions & CO2, provide rapid transport of nutrients, ion & dissolved gases, controls the volume of blood flow, absorbs & recycles neurotransmitters, releases chemical that enhance or suppress communication across synaptic terminals

Form the myelin sheath along the length Oligodendrocytes Form the myelin sheath along the length of the axon myelin - increases the speed of the action potential along the axon myelin sheath - membrane wrapping around the axon internodes - area of the axon wrapped myelin (1 - 2 mm in length) nodes - small gaps (few micrometers) between internodes with no myelin white matter - CNS, areas with myelinated axons, high lipid content gray matter - areas containing neuron cell bodies, dendrites & unmyelinated axons

The Myelinated Axon

Microglia least numerous cleanup by engulfing cellular debris, waste products & pathogens