Chapter 12, 13 Nervous Tissue, Spinal Cord

Divisions of NS 1.CNS-central nervous system A.Brain B.Spinal Cord 2.PNS-peripheral nervous system- primarily nerves of body A. Spinal nerves- 31 pairs B. Cranial nerves- 12 pairs

Divisions of PNS a. Somatic- controls skeletal muscle, skin b. Autonomic-controls smooth, cardiac muscle 1. Sympathetic- fight/flight, emergencies 2. Parasympathetic-relaxation, “vegetative” reflexes

3 Basic Functions 1.Sensory (afferent) Receptors send impulses to CNS 2.Motor (efferent) CNS sends impulses to effectors (muscles or glands) 3. Integrated Functions- intelligence, creativity, personality, etc.

Organelles in a neuron 1.Nucleus 2.Granular ER(Nissl bodies) 3.Mitochondria 4.Neurofibrils(microtubules) 5.No centrioles -

Classification of Neurons P365 1.Anaxonic- located in brain, special sense organs 2.Bipolar-special sense organs 3.Unipolar-sensory neurons of PNS 4.Multipolar- most common

Neuroglia 2. Neuroglia in PNS A. Satellite Cells- similar to astrocytes B. Schwann Cells- similar to oligodenedrocytes, produce myelin sheath in PNS

Neuroglia 1.Neuroglia in CNS A. Astrocyte- function in creating blood- brain barrier, provide structure B. Oligodendocyte- produce myelin sheath C. Microglia- immune cells of CNS, similar to macrophages D. Ependymal- found in ventricles of brain, produce cerebrospinal fluid

Synapse A specialized site where neurons communicate with one another pse.htmlhttp://faculty.washington.edu/chudler/syna pse.html

Myelin Acts like electrical insulation Nodes of ranvier-gaps between schwann cells on axon; allows nerve impulse to jump between nodes; leads to high conduction speeds= 100m/s Locations- A. All motor neurons B. All spinal nerves C. 99% of brain

Unmyelinated Slow conductions speed,.5 m/s Located A. In autonomic nervous system

Spinal Cord- Chapter 13 Length= 18”, width=.5” Extends from base(foramen magnum) of skull to 2 nd lumbar vertebra “carrot shaped” conus medullaris- many nerves exit and form cauda equina 2 enlargements=cervical and lumbar- where more nerves enter and leave the cord

# of spinal nerves-31 Cervical- 8 Thoracic-12 Lumbar-6 Sacral-5

Organization 1.White matter- myelinated sections on outermost parts can be ascending- going to brain -carry sensory info -called afferent Can be descending- coming from brain - carry motor info - called efferent

Root- where nerve enters or exits cord dorsal root=sensory/afferent ventral root= motor/efferent ** In back door out front door**

Organization 1.Gray matter- unmyelinated sections forming H pattern in the interior posterior horns- contain afferent neurons anterior horns- contain efferent neurons “cross bar”=commissure

Plexuses Plexus- interwoven network of nerves 1.Cervical plexus 2.Brachial plexus 3.Lumbar plexus 4.Sacral plexus

Reflexes Rapid automatic response to a specific stimuli Work through a reflex arc- a simple neural pathway 1.reception 2. transmission via sensory neuron 3. integration 4. transmission via motor neuron 5. response

Classifying Reflexes p By response A. Somatic reflex- involves skin, skeletal muscle, function in protection B.Visceral reflex- involves cardiac, smooth muscle, glands, bl.v, function in homeostasis

2.By development A. Innate- w/drwal fr. pain, suckling, tracking objects w/ eye B. Acquired- driving, sports

3. By processing site A.Spinal- patellar reflex B.Cranial- sudden noise, bright light, respiration 4.Complexity of circuit A.Monosynaptic- B.Polysynaptic