Neural Tissue Chapter 12 Flashcards
The Nervous System
includes all neural tissue in body
Neural Tissue
2 kinds of cell: neurons and neuroglia
Neurons
cells that send and receive signals
Neuroglia
glial cells that support and protect neurons
Organs of Nervous System
brain, spinal cord, sensory receptors and nerves
CNS includes:
spinal cord, brain, neural and connective tissue, blood vessels
Functions of the PNS
deliver sensory info to CNS, carry motor commands, all neural tissue outside CNS
Function of the CNS
are to process and coordinate: sensory data, motor commands, higher function of brain
Nerves
aka peripheral nerves: bundle of axons w/ CT and blood vessels, carry sensory info and commands to PNS
Cranial Nerves
connect to brain
Spinal Nerves
attach to spinal cord
Functional Divisions of PNS
afferent and efferent divisions
Afferent Divison
carries sensory info from PNS sensory receptors to CNS
Efferent Division
carries motor commands from CNS to PNS muscles and glands
Somatic Nervous System (SNS)
controls skeletal muscle contractions (reflexes)
Autonomic Nervous System (ANS)
controls subconscious actions, contractions of smooth and cardiac muscle and glandular secretions
Structure of Neurons
dendrites, nucleus, axon, cell body, synaptic terminal
The Multipolar Neuron
common in the CNS: cell body (soma), short, branched dendrites, long single axon
Axons
long, carries electrical signal (action potential) to target, critical to function
The Synapse
area where a neuron communicates with another cell
2 Types of Synapses
Neuromuscular junction: synapse b/w neurons and muscle. Neuroglandular junction: synapse b/w neuron and gland
Cell Interface
post/presynaptic cell, synaptic cleft/knob
Presynaptic Cell
neuron that sends messages
Postsynaptic Cell
cell that receives messages
Synaptic Cleft
small gap that separates pre/post synaptic membrane
Synaptic Knob
expanded area of axons, contains synaptic vesicles of neurotransmitters
3 Types of Sensory Receptors
Interoceptors, Exteroceptors and Proprioceptors
Interoceptors
monitor internal systems: digestive, respiratory, cardio, urinary. Internal sense: taste, deep pressure and pain
Exteroceptors
external sense: pressure, temp, touch. distance senses: sigh, smell, hear
Proprioceptors
monitor position and movement (skeletal muscle and joints)
Motor Neurons
carry instructions from CNS to peripheral effectors via efferent fibers (axons)
2 Major Efferent Systems
somatic nervous system (SNS) and autonomic nervous system (ANS)
Somatic Nervous System (SNS)
includes ALL somatic motor neurons that innervate skeletal muscles
Autonomic Nervous System (ANS)
visceral motor neurons innervate all peripheral effectors: smooth/cardiac muscle, adipose tissue, glands
Neuroglia of the Central Nervous System
half the volume of the nervous system and many types of neuroglia in CNS and PNS
4 Types of Neuroglia in the CNS
ependymal cells, astrocytes, oligodendrocytes, microglia
Ependymal Cells
highly branched processes and contact neuroglia directly
Astrocytes
large cell bodies and many processes
Oligodendrocytes
smaller cell bodies and fewer processes
Microglia
small and many fire branched processes
White Matter
regions of CNS with many myelinated nerves
Gray Matter
unmyelinated areas of CNS
Main Membrane Processes in Neural Activity
action potential: electrical impulse, graded potential and propogates along surface of axon to synapse
Sodium and Potassium Channels
membrane permeability to sodium and potassium determines transmembrane potential, either passive or active
Passive Channels
aka leak channels, always open, permeability changes w/ conditions
Active Channels
aka gated channels, open and closed in response to stimuli, rest potential most gated channels are closed
3 Conditions of Gated Channels
closed but can open, open activated, closed and not capable of opening (inactivated)
Depolarization
chemical stimulus applied, electrical impulse causes action potential
Repolarization
chemical ions removed, returned to their previous resting state, with relaxation
Hyperpolarization
increasing the negativity of the resting potential, result of opening a potassium channel, opposite effect, positive ions move out, not into cell
Action Potential
propagated changes in transmembrane potential, affect entire membrane, link graded potential at cell body w/ motor end plate actions
All -or-None Principle
if stimulus exceeds threshold amount: action potential same and no matter how large stimulus, eithered triggere or not
Propagation of Action Potentials
moves action potentials in axon hillock along axon and repeat, not passive flow
2 Methods of Propagating Action Potentials
continuous and saltatory propagation
Continuous Propagation
unmyelinated axons, affects 1 segment of axon at a time
Saltatory Propagation
faster and uses less energy than continuous, myelin insulates axon and prevents continuous propagation, current jumps from node to node, depolarization occurs at node only
Axon Diameter and Propagation Speed
ion movement is related to cytoplasm concentration, xon diameter affects speed, large diameter lower resistence
Type A Fiber
myelinated, large diameter, high speed, carry rapid info to/from CNS (position, balance, touch and motor impulses)
Type B Fiber
myelinated, medium diameter, medium speed, carry intermediate signals (sensory info & peripheral effectors)
Type C Fibers
unmyelinated, small diameter, slow speed, carry slower info (involuntary muscle and gland control)
2 Types of Synapses
electrical and chemical synapse
Chemical Synapse
signal transmitted across gap by neurotransmitters, found in most synapses, cells not in direct contact, action potential may or may not be propagated to postsynaptic cell depend on: amount of transmitters and sensitivity
Electrical Synapse
direct physical contact b/w cells
2 Classes of Neurotransmitters
excitatory and inhibitory neurotransmitters
Excitatory Transmitter
cause depolarization of postsynaptic membranes and promote action potentials
Inhibitory Transmitter
causes hyperpolarization of postsynaptic membranes and suppress action potentials
The Effect of a Neurotransmitter on Postsynaptic Membrane
depends on receptor and not on the neurotransmitter
The Effect of a Neurotransmitter on ACh
usually promotes action potential but inhibits cardiac neuromuscular junctions
Cholinergic Synapses
any synapse that release ACh all neuromuscular junctions w/ skeletal muscle fiber
Presynaptic Inhibition
action of an axoaxonal synapse at synaptic knob, decreases the neurotransmitter released by presynaptic membrane
