Chapter 12 - Nervous tissue and Nervous system Flashcards
Nervous System
THE master control and communications center in the body
Communication occurs via electrical signals
Three overlapping functions
Three overlapping functions of the Nervous System
Sensory receptors monitor changes
Integration (processing and interpreting)
Response (motor output)
Central Nervous System (CNS)
Brain and spinal cord
Integrative and control centers
Peripheral Nervous system (PNS)
Cranial nerves and spinal nerves
Communication lines between the CNS and the rest of the body
2 Divisions: Sensory and Motor
Sensory (afferent) division
Carry signals TO brain/spinal cord
Somatic and visceral sensory nerve fibers
Conducts impulses from receptors to the CNS
Motor (efferent) division
Carry signals FROM brain/spinal cord
Motor nerve fibers
Conducts impulses from the CNS to effectors (muscles and glands)
2 systems: Somatic nervous system & autonomic nervous system
Somatic nervous system
Structures external to visceral cavity Somatic motor (voluntary) Conducts impulses from the CNS to skeletal muscles
Autonomic nervous system (ANS)
Visceral motor (involuntary)
Conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands
2 divisions: Sympathetic division & Parasympathetic division
Sympathetic division
Mobilizes body systems during activity
Parasympathetic division
Conserves energy
Promotes house-keeping functions during rest
Visceral
Organs
4 combinations of Basic Divisions of Nervous System
Somatic snsory
Somatic motor (voluntary)
Visceral sensory
Visceral motor (involuntary ANS)
Basic Divisions of the Nervous System
Sensory
Motor
Somatic
Visceral
Neurons comprised of…
Cell body
Dendrites
Axons
Cell body
Contains one nucleus
Group of cell bodies in CNS = nucleus
Group of cell bodies in PNS = ganglia
Metabolic center of neuron (contains organelles)
Group of cell bodies in CNS
nucleus
Group of cell bodies in PNS
ganglis
Dendrites
Branched processes that extend from cytoplasm of cell body
RECEIVE stimuli and conduct impulses TO CELL BODY
Axons
Conduct impulses AWAY FROM CELL BODY
If myelinated or large, have increased electrical conduction speed
Lengths vary; have axon terminals at end (bulbs)
Is a cytoplasmic extension from cell body
Synapses
Junction that controls information transfer from one neuron to the next
Can be excitatory or inhibitory
Presynaptic neuron
Conducts signal towards synapse
Postsynaptic neuron
Conducts signal away from synapse
Neurons structure
Multipolar
Bipolar
Unipolar
Multipolar neuron
Most of body’s neurons
Many dendrites and an axon
Motor neurons, most interneurons
Bipolar neuron
Processes extend from two sides of body
Rare, sensory
Unipolar neuron
One process that divides like a “T”
sensory neurons
Neuron function
Sensory
Motor
Interneuron
Sensory (afferent) neurons
carry signal TO CNS
Motor (efferent) neurons
Carry signal AWAY from CNS
Interneurons (association neurons)
Between sensory and motor neurons
Located ONLY in CNS
Neuroglia
Support cells
Have central cell body and branching processes, are smaller than neurons
Outnumber neurons 10-1 in CNS
Consist of half of brain’s mass
Can divide throughout life
Provide scaffold of support for neurons and cover non-synaptic parts (insulate and keep them from interfering with each other)
Types of CNS Neuroglia
Astrocytes
Microglia
Ependymal cells
Oligodendrocytes
Types of PNS Neuroglia
Satellite cells
Schwann cells
Astrocytes
Most abundant neuroglia
Key component of blood brain barrier
-regulate passage of molecules from blood to brain
-only allow small molecules through to brain
Microglia
Smallest and least abundant neuroglia
Phagocytes, thorny-looking
Ependymal cells
Form simple epithelial layer that lines central cavity of brain and spinal cord
Oligodendrocytes
Produce myelin sheath around nerve cell axons
Fewer branches than astrocytes
Satellite cells
Surround cell bodies in ganglia
Schwann cells (neurolemmocytes)
surround all axons in PNS
produce myelin sheath (gaps=nodes of Ranvier)
Nerves
Collection (bundle) of neurons outside CNS
Naked eye can see a nerve, but not a neuron
Composed of many axons
Nerves often contain both sensory and motor neurons (mixed nerves)
Some are sensory or motor only though (cranial nerves)
Neurons are held together by CT
Endoneurium
Surrounds each axon
loose CT
Perineurium
Surrounds bundle of axons
fascicle
Epineurium
Surrounds entire nerve
bunch of fascicles
Reflex Arcs
Chains of neurons that create reflexes
Unlearned and involuntary
Somatic or visceral
Monosynaptic or Polysynaptic
Reflex
rapid, automatic, motor response to a stimulus
5 components of reflex arcs
Receptor Sensory neuron Integration center Motor neuron Effector
Receptor
site where stimulus acts
Sensory neuron
transmits signal to CNS
Integration center
one or more synapses
Motor neuron
Conducts impulse from integration center
Effector
muscle or gland that responds
Polysynaptic
one or more interneurons are part of reflex pathway
most contain one interneuron (are 3-neuron reflexes)
monosynaptic
one synapse is involved
fastest of all reflexes
classic example is knee jerk
Gray matter
cell bodies
H-shaped in spinal cord
-dorsal half has bodies of interneurons and venral half has bodies of motor neurons
White matter
axons
often myelinated
tracts
bundles of axons
multiple sclerosis (MS)
Most common neural disability in young adults
progressive, destroys patches of myelin
cause is not well understood-autoimmune
