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Flashcards in The Nervous System Deck (30):
1

2 structural subdivisions of the nervous system

1. Central nervous system (brain & spinal cord)
2. Peripheral nervous system (cranial nerves, spinal nerves and ganglia)

2

Sensory Nervous system

-AKA

-what it does

-2 components

-aka afferent nervous system
-Receives sensory info from receptors in PNS & transmits to CNS
2 components;
1. Somatic sensory
-general senses such as touch, pain, pressure, vibration & proprioception
-special senses such as taste, vision, balance, hearing and smell
2. Visceral sensory:
-impulses from viscera (generally temp & stretch)

3

Motor Nervous System

-AKA

-what it does

-2 components

-AKA efferent nervous system
-sends impulses from CNS to muscles & glands
-2 components;
1. Somatic motor (Voluntary)
-impulses from CNS that cause contraction of skeletal muscles
2. Autonomic motor (Involuntary)
-impulses from CNS that regulate smooth & cardiac muscles (as well as glands)

4

2 cell types w/in nervous system

1. Neurons (nerve cells)
-electrically excitable cells that initiate, transmit & receive nerve impulses
-approx. 35-100 billion neurons
2. Glial cells (support cells)
-Nonexcitable cells that support and protect neurons -> provide an organized, supporting framework for all nervous tissue
-100 billion - 1 trillion glial cells
-capable of mitosis (neurons can't)

5

Neurons

-3 characteristics

-Basic structural unit of nervous system
-Conduct nerve impulses from one part of the body to another
CHARACTERISTICS;
-High metabolic rate (needs lots of O2, glucose)
-Extreme longevity (stay in body for whole life)
-Nonmitotic

6

Neuron structure

-3 main structural regions

-3 main structural regions;
-Cell body
-Dendrites
-Axon
-Sends electrical impulses unidirectionally

7

Neuron; Cell body

-contains typical organs such as Nucleus, nucleolus, mitochondria, free ribosomes & rough ER.
-aka soma
-is control centre
-responsible for receiving, integrating & sending nerve impulses

8

Neuron; Dendrites

-Input
-short processes that branch from cell body
-Receive nerve impulses & carry them to cell body
*more dendrites = more impulses that can be received
-many also have dendrite spines to increase SA

9

Neuron; Axons

-what they do

-axon hillock

-synaptic knobs

-Myelin

-Output
-Transmit nerve impulses away from cell body & transmit info to other cells
-axon hillock = region where axon connects to the cell body
-neurons have 1 or no axons
-Synaptic knobs = end of axons that transmit impulse to effector cells
-Often covered in Myelin (insulating concentric layers that allow for faster nerve impulses)

10

Neuron Classification (Structurally; 3 types)

3 types depending on number of cell processes emanating directly from cell body;
-Unipolar: Single, short process that branches like a T (most sensory neurons of PNS)
-Bipolar: Two processes, one dendrite & one axon (relatively uncommon in humans -> primarily linked w/ special senses)
-Multipolar: many dendrites and a single axon (most common neuron e.g. motor neuron)

11

Neuron Classification (Functionally; 3 types)

-what they do

-Sensory (Afferent): transmit impulses from sensory receptors to CNS
-Motor (Efferent): transmit impulses from CNS to muscles or glands
-Interneurons: Facilitate communication between sensory and motor neurons

12

Glial Cells

-aka
-where found
-features

-aka neuroglia
-Found in both CNS & PNS
-Smaller than neurons & capable of mitosis
-Physically protect & nourish neurons
-more numerous than neurons
-Brain tumors more likely to be derived from glial cells than neurons

13

Glial Cells of the CNS (4 types)

-Astrocytes (most common)
-Ependymal cells
-Microglial cells
-Oligodendrocytes (same structure in PNS but have another name)

14

Glial Cell of CNS; Astrocytes

-Functions

-Most abundant
FUNCTIONS
-Helping form Blood-brain barrier (protects brain from toxins)
-regulating tissue fluid composition
-helping regulate synaptic transmission
-forming structural network (aids in forming framework in brain)
-replacing damage neurons
-Assisting neuronal development

*hugs the capillary

15

Glial cells of CNS; Ependymal cells

-functions

-ciliated cuboidal epithelial cells that line ventricles of brain & central canal of spinal cord
-In conjunction w/ other glial cells, the ependymal cells produce cerebral spinal fluid (CSF) & form choroid plexus

16

Glial Cells of CNS; Microglial cells

-Function

-Small cells that are motile
-wander through the CNS & exhibit phagocytic activity, removing cellular debris from dead or dying cells
-aid in pathogen removal/detection

17

Glial cells of CNS; Oligodendrocytes

-where found
-what they do

-Associated w/ CNS axons only
-wrap themselves around axons like electrical tape
-produce myelin - is an insulator of electrical activity (allows faster electrical impulses along axon)

18

Glial Cells of PNS

-2 types

-functions

2 types;
1. Satellite cells: flattened cells arranged around neuronal cell bodies in ganglia
2. Neurolemmocytes: aka Schwann cells - associated w/ PNS axons only
-wrap themselves around axons like electrical tape, produce myelin which is an insulator of electrical activity
*same structure & function as oligodendrocytes

19

Myelination of Axons

-Affects ability of neurons to conduct nerve impulses, also called action potentials
-Formed by neurolemmocytes in PNS and oligodendrocytes in CNS
-serves as insulation

20

Axon regeneration

-Damaged axons can regenerate if cell body is intact and critical amount of neurilemma remains
-depends on extent and site of damage
-neurolemmocytes play important role in process

21

Wallerian Degeneration

-Trauma severs axons
-Proximal portion of each severed axon seals off and swells - distal portion disintegrate
-neurileema and endoneurium form regeneration tube
-axon regenerates and remyelination occurs
-innervation to effector is restored

22

Nerves
-what they are

-3 layers

-Cablelike bundle of parallel axons
-Surrounded by three CT wrappings;
1. Endoneurium (within): around each individual axon
2. Perineurium (around): around individual fascicles
3. Epineurium (upon): around the entire nerve

*between fasicles = blood vessels

23

Synapses

-what they are
-3 things a typical neuron consists of

-Specialized junctions b/w one axon and another neuron, muscle cell or gland cell
Typical neuron;
-Presynaptic neuron
-Postsynaptic neuron
-Synaptic cleft

*can be electrical or chemical

24

Autonomic Nervous system

-what it is

-is a complex system of nerves that govern involuntary actions
-works constantly w/ somatic nervous system to regulate body organs and maintain normal internal functions
-ANS and SNS both part of central nervous system & peripheral nervous system
-SNS operates under our conscious/voluntary control
-ANS operates under involuntary contraol - usu unaware of them

25

Comparison of Somatic & Autonomic Nervous system

-Both use sensory & motor neurons
-SNS: somatic motor neurons innverate skeletal muscle fibres, causing conscious voluntary movement
-Single lower motor neuron axon extends uninterrupted from spinal cord to one or more muscle fibers
-ANS motor neurons innervate smooth muscle fibers, cardiac muscle fibers or glands
-ANS motor neurons can either excite or inhibit cells in viscera
-two-neuron chain innervates muscles and glands

26

Two-neuron chain in ANS

-First neuron in ANS pathway is preganglionic neuron
-cell body in brain or spinal cord
-preganglionic axon extends to second cell body housed w/in autonomic ganglion in peripheral nervous system
-second neuron in pathway called ganglionic neuron
-a postganglionic axon extends from its cell body to effector cells
-two neuron chain vastly increases communication & control of ANS

27

ANS Subdivisions & what they do

-Sympathetic:
-mobilises body during extreme situations -> preparation of body for emergencies (fight or flight)

-Parasympathetic:
-maintenance activities and conserves body energy
-conservation of energy and replenishment of nutrient stores (rest and digest)

*two divisions counterbalance each other

28

Role of Sympathetic Division

-Fight or flight system
-E activities; Exercise, excitement, emergency & embarrassment
-promotes adjustment during exercise -> blood flow to organs is reduced

-e.g. HR increases, breathing rapid and deep, skin cold and sweaty and pupils dilate

29

Role of Parasympathetic Divison

-concerned w/ keeping body energy use low
-D activities; Digestion, defection and diuresis

-e.g. blood pressure, HR and respiratory rates low
-GI tract activity high
-skin is warm and pupils constricted

30

Autonomic nervous system

-Two systems of ANS service same visceral organs but work in opposition to each other (antagonistic)
-balanced to keep ourselves in a state of dynamic balance