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How does the nervous system know what is going on?
Sensory receptors provide sensory input
Where does the sensory input come from?
-Outside and inside the body
-Environmental and visceral changes
Name 5 sensory receptors
Free nerve endings (pain and temperature receptors)
Meissner’s corpuscle (touch receptors)
Lamellar corpuscle (deep pressure receptor)
Golgi tendon organ (proprioceptor)
Muscle spindle (proprioceptor)
What happens to the sensory input?
Information travels to the integration centre to determine the appropriate response
What happens as a result of the sensory input and integration of the information?
- An appropriate response occurs
- (Eg. A muscle contracts or a gland secretes its product)
Major divisions of the nervous system and their components
1.Central Nervous System (CNS)
2. Peripheral Nervous System (PNS)
- i) cranial nerves
- ii) peripheral nerves
Structural Classification and functions of the Central nervous system (CNS)
Structure: organs, brain, spinal cord.
Function: integration, command center, interprets incoming sensory information, issues outgoing instructions
Structural Classification and function of the Peripheral Nervous System
Structure: nerves extending from the brain and spinal cord. spinal nerves—carry impulses to and from the spinal cord-cranial nerves—carry impulses to and from the brain
Functions: serve as communication lines amongsensory organs, the brain and spinal cord, and glands or muscles
3 Functions of the Nervous System
Sensory input—gathering information to monitor changes occurring inside and outside the body, changes = stimuli
Integration-to process and interpret sensory inputand decide if action is needed.
Motor output- a response to integrated stimuli.The response activates muscles or glands.
Functional Classification of the Peripheral Nervous System
- Sensory (afferent) division- nerve fibers that carry information to the central nervous system.
- Motor (efferent) division- nerve fibers that carry impulses away from the central nervous system
Motor (efferent) division: Two subdivisions
- Somatic nervous system: voluntary, consciously controls skeletal muscles.
- Autonomic nervous system: involuntary, automatically controls smooth and cardiac muscles and glands. Further divided into the sympathetic and parasympathetic nervous systems.
Nervous Tissue: Support Cells
Support cells in the CNS are grouped together as “neuroglia” or simply “glial cells”
Glial cells are capable of replication
General functions: support, insulate, protectneurons.
Abundant, star-shaped cells.
Functions: brace neurons, form barrier between capillaries and neurons, blood-brain barrier, control the chemical environment ofthe brain, and mop up leaked potassium.
Spider like phagocytes
Function: dispose of debris, bacteria, and dead brain cells.
Functions: line cavities of the brain and spinal cord, control composition of cerebrospinal fluid, ciliated, assist with circulation of cerebrospinal fluid.
Wrap around axons of neurons within the central nervous system, membranous extensions of the oligodendrocyte cell membrane, produce a fatty insulating cover for the axon called the myelin sheath.
- Form the myelin sheath in the peripheral nervous system,
- (differences between the CNS and PNS cells that produce the myelin sheath several cells are needed to form the myelin sheath of a single axon within the PNS)
Protect neuron cell bodies, found around ganglia of the peripheral nervous system.
A ganglion is a collection of nerve cell bodies found outside the central nervous system.
Neurons = nerve cells
Cells specialized to transmit messages.
Major regions of neurons- cell body: nucleus and metabolic center of the cell, processes:fibers that extend from the cell body.
What organelle would you expect to
see in the nerve cell body if replication were possible?
Neurons are unable to replicate because they lack centrioles.
conduct impulses toward the cell body, neurons may have hundreds of dendrites.
Conduct impulses away from the cell body, neurons have only one axon arising from the cell body at the axon hillock.
-End in axon terminals
- -contain vesicles with neurotransmitters
- -axon terminals are separated from the next neuron by a gap
- -synaptic cleft, gap between adjacent neurons
- -synapse, junction between nerves, junction between a nerve and a muscle cell
How is information propagated from one nerve cell to another ?
What allows the signal to be propagated quickly?
The signal is an electrical signal, causes changes in the polarity of the cell membrane of the neuron or muscle cell.
The myelin sheath.
Whitish, fatty material covering axons, schwann cells produce myelin sheaths in jelly roll-like fashion around axons (PNS), nodes of ranvier, gaps in myelin sheath along the axon.
Oligodendrocytes produce myelin sheaths around axons ofthe CNS.
Clusters of cell bodies
Basal nuclei within the white matter of the cerebrum of the central nervous system .
Ganglia collections of nerve cell bodies outside the central nervous system.
Dorsal root ganglia of the spinal cord sensory nerve cell bodies
Tracts-bundles of nerve fibers in the CNS
Nerves-bundles of nerve fibers in the PNS
White matter-collections of myelinated fibers
Gray matter-collections of mostly unmyelinated fibers and cell bodies
Interneurons (association neurons)
Found in neural pathways in the central nervous system, connect sensory and motor neurons
- -many extensions from the cell body
- -all motor and interneurons are multipolar having many dendrites and an axon
- -most common type of neuron
- -one axon and one dendrite
- -located in special sense organs such as nose and eye
- -have a short single process leaving the cell body
- -sensory neurons found in PNS ganglia
Functional Properties of Neurons
- -ability to respond to stimuli
- -ability to transmit an impulse