Nervous Tissue SI Worksheet PDF

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KIN 2500 – Human Anatomy Nervous Tissue

SI: Matt Landry [email protected]

Structural Organization: The Central and Peripheral Nervous Systems  The central nervous system (CNS) is composed of the brain and spinal cord  The peripheral nervous system (PNS) is composed of the o Cranial nerves, which extend from the brain o Spinal nerves, which extend from the spinal cord o Ganglia, which are clusters of neurons outside the CNS Functional Organization: Sensory and Motor Nervous Systems  Together the CNS and PNS preform three general functions o Responding to information o Collect information o Processing and evaluating information  Sensory Nervous System o Is responsible for receiving sensory information from receptors and transmitting this information to the CNS o The sensory nervous system involves both CNS and PNS components:  Nerves in the PNS transmit the sensory information  Part of the brain and spinal cord in the CNS interpret the information o The sensory nervous system contains two parts:  The somatic sensory which has components for general somatic senses and special senses.  General Senses: touch, temperature, proprioception (sense of position and movement of the joints and limbs in relation to the body), pain, pressure and vibration  Special Senses: smell, vision, hearing, taste, and balance  The visceral sensory which has components that transmit nerve impulses from blood vessels and the viscera to the CNS.  The visceral senses primarily include: temperature and stretch  These functions are said to be involuntary  Motor Nervous System o The motor nervous system is responsible for transmitting motor impulses from the CNS to the muscles and glands  The motor division is divided into the somatic and autonomic motor components.  The somatic motor component (SNS): conduct nerve impulses from the CNS to the skeletal muscles causing them to contract

KIN 2500 – Human Anatomy Nervous Tissue

SI: Matt Landry [email protected]

o The SNS is often called the voluntary nervous system because the contraction of the skeletal muscles is under conscious control.  The autonomic motor component (ANS): innervate internal organs and regulates smooth muscle, cardiac muscle, and glands o The ANS is often called the involuntary nervous system. o Consists of two parts: sympathetic (fight or flight) and parasympathetic (rest and digest) division  The term different means inflowing, which indicates that nerve impulses are transmitted to the CNS. This is best associated with the sensory nervous system  The term efferent means conducting outward, which indicates that nerve impulses are transmitted from the CNS. This is best associated with the motor nervous system. Neurons  The basic structural unit of the nervous system is the neuron. There are several basic structural features: o The cell body serves as the neurons control center and is responsible for receiving, integrating, and sending nerve impulses.  The cell body is enclosed by a plasma membrane and contains cytoplasm surrounding a nucleus  The nucleus contains a prominent nucleiolus, reflecting the high metabolic activity of a neuron. o Dendrites tend to be shorter, smaller processes that branch off of the cell body  The function of dendrites is to conduct nerve impulses toward the cell body o Axons are the longer nerve cell process emanating from the cell body  The function of an axon is to transmit nerve impulse away from the cell body and toward another cell o An axon connects to the cell body at a triangular region called the axon hillock. o Most axons and their collateral branch extensively at their distal ends into an array of fine terminal extensions called axon terminals.  At the extreme end of these extensions are expanded regions called synaptic end knobs or end bulb  Neuron Classification 6 Types of Glial Cells

KIN 2500 – Human Anatomy Nervous Tissue Cell Type

Astrocyte

CNS or PNS CNS

Ependymal

CNS

Microglial

CNS

Oligodendrocyte

CNS

Neurolemmocyte s aka: Schwann Cells Satellite Cells

PNS

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Glial  

PNS

SI: Matt Landry [email protected] Functions

Most common type. Replaces damaged neurons and regulates synaptic transmission. Form the blood brain barrier and provides structural support Line ventricles of the brain and spinal chord. Assist in the production and circulation of CSF Defend against pathogens, remove debris, and phagocytizes waste Myelinates and insulate the CNS which allows for faster nerve impulses conduction through the axon. Myelinates and insulate the PNS which allows for faster nerve impulses conduction through the axon

Protection and regulates nutrients for cell bodies in ganglia. o Unipolar Neurons: have a short, shingle, neuron process that emerges from the cell body and branched like a T o Bipolar Neurons: two neuron processes that extend from the cell body (one axon and one dendrite) o Multipolar: multiple neuron processes (many dendrites and a single axon extending from the cell body) o Which of the three types is the most common? Multipolar Functional Classification o Sensory Neurons: conduct nerve impulses from the body to the CNS o Motor Neurons: conduct nerve impulses from the CNS to the muscles or glands o Interneurons:  Found only in the CNS  Facilitates communication between motor and sensory neurons Cells Also known as neuroglia; occurs in the CNS and PNS Glial cells differ from neurons in the respect that they o Are smaller and capable of mitosis (being able to reproduce) o Glial cells do not transmit nerve impulses, but they do assist neurons with their function o Glial cells far outnumber neurons

KIN 2500 – Human Anatomy Nervous Tissue

SI: Matt Landry [email protected]

The function of glial cells collectively is to physically protect and help nourish neurons and provide an organized, supporting framework for all the nervous tissue Myelination  Myelination is the process by which part of an axon is wrapped with a myelin sheath, the insulating covering around the axon consisting of concentric layers of myelin. Axon Regeneration  PNS axons are vulnerable to cuts, crushing injuries, and other types of trauma. A damaged axon can regenerate if the cell body remains intact and a critical amount of neurilemma is saved.  The success of PNS axon regeneration depends on two factors: o The amount of damage o the distance between the site of the damaged axon and the structure that it innervates  Neurolemmocytes play an active role in regeneration. This process goes as follows 1. The axon is severed by some type of trauma 2. The proximal end of each severed axon seals off and swells a. This process is known as Wallerian Degeneration 3. Neurilemma and the endoneurium form a regeneration tube. 4. Axon regeneration and remyelination occur 5. innervation to effectors is restored Nerves  A nerve is a cable like bundle of axons. Like a muscle, a nerve has three successive connective tissue wrappings. o An individual axon in a myelinated neuron is surrounded by neurolemmocytes and then wrapped in the endoneurium, a delicate layer of areolar connective tissue that separates and electrically insulates each axon. o Groups of axons are wrapped into separate bundles called fascicle by a cellular dense irregular connective tissue layer called the perinurieum o All of the fascicles are bundled together by a superficial dense irregular connective tissue covering called the epinurieum. This encloses the entire nerve providing support and protection. Synapses  Axons terminate as they contact other neurons, muscle cells, or glands at specialized junctions called synapses where the nerve impulse is transmitted to the other cell.  A typical synapse in the CNS consists of the close association of a presynaptic and postsynatic neuron region where plasma membranes are separated by a very narrow space called the _____. 

KIN 2500 – Human Anatomy Nervous Tissue

SI: Matt Landry [email protected]

A very precise sequence of events is required for the conduction of a nerve impulse from the presynaptic neuron to the postsynaptic neurons:  While this process is covered in greater detail in Human Physiology, Dr. Hargroder would like you to know the basis of this process. Put the following steps in logical order. A. An influx of sodium ions (Na+) moves into the postsynaptic cell through the open gate, affecting the charge across the membrane. B. A nerve impulse travels through the axon and reaches its synaptic knob. C. Change in the postsynaptic cell voltage causes a nerve impulse to begin in the postsynaptic cell. D. The arrival of the nerve impulse at the synaptic knob causes an increase in calcium ion (Ca2+) movement into the synaptic knob through voltage-regulated calcium ion channels in the membrane. E. Entering calcium ions cause synaptic vesicles to move to and bind to the inside surface of the membrane; neurotransmitter molecules within the synaptic vesicles are released into the synaptic cleft by exocytosis. F. The enzyme acetylcholinesterase (AChE) resides in the synaptic cleft and rapidly breaks down molecules of ACh that are released into the synaptic cleft. G. Neurotransmitter molecules attach to specific protein receptors in the plasma membrane of the postsynaptic cell, causing ion gates to open. H. Neurotransmitter molecules diffuse across the synaptic cleft to the plasma membrane of the postsynaptic cell.  The correct order is: B, D, E, H, G, A, C, B Neural Integration and Neuronal Pools  The nervous system is able to coordinate and integrate nervous activity in part because of billions of interneurons in the CNS grouped in complex patterns called neuronal pooles  In a converging circuit, nerve impulse converges at a single postsynaptic neuron. This neuron receives input from several presynaptic neuron o An example of this is vomiting  In a diverging circuit, information spreads from one presynaptic neuron to several postsynaptic neurons o An example of this is a few neurons in the brain control the movement of skeletal muscles during walking, also stimulating the back to maintain posture. A single or few inputs lead to multiple outputs.  In a reverberating circuit, feedback is used to produce a repeated, cyclical stimulation of the circuit. 

KIN 2500 – Human Anatomy Nervous Tissue

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SI: Matt Landry [email protected]

o Once activated, a reverberating circuit may continue to function either until an inhibitory stimuli or a synaptic fatigue breaks the cycle o An example of this is breathing In a parallel-after-discharge circuit, several neurons or neuronal pooles that process the same information at one time. o A single presynaptic neuron stimulates different groups of neurons, each of which passes the nerve impulses along a pathway that ultimately synapse with a commone post synaptic cell o An example of this is involved with higher order thinking, such as the type needed to preform precise mathematical calculations.

Clinical Connection Note: This exam contains a lot of clinical connections. Dr. Hargroder often fills this exam’s test bank with questions about clinical connections that were mentioned in class. This is one example of a clinical connection from the nervous tissue chapter. Be certain to review your notes and study all clinical connections mentioned in class.

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Multiple Sclerosis (MS) is a preogressive demyelination of neurons in the CNS accompanied by the destruction of oligodendrocytes.

As a result, the conduction of nerve impulses is disrupted leading to impaired sensory perception and motor coordination....