Lecture 24 - The Nervous System And Neuroglia Flashcards
Functions of the nervous system
Gathering sensory input from sensory receptors (take in info)
Processing and interpreting sensory input to decide on appropriate response - integration (analyze info)
Using motor output to activate effector organs, muscles and glands to cause a response (produce response)
The central nervous system
Brain and spinal chord
Control centre that interprets sensory input and dictates motor output
Peripheral nervous system
Portion on nervous system outside CNS
Consists mainly of nerves that extend from brain and spinal chord
Divisions of peripheral nervous system
Sensory (afferent) division
Somatic sensory fibres
Visceral sensory fibres
Motor (efferent) division
Sensory (afferent) division
carries impulses toward the central nervous system from sensory receptors located throughout the body
Somatic sensory fibres
Convey impulses from skin, skeletal muscles and joints to the CNS
Visceral sensory fibres
carry impulses from organs within the ventral body cavity
Motor (efferent) division
transmits impulses from the CNS to effector organs, such as muscles and glands. It has two subdivisions.
Motor (efferent) division of PNS- Somatic nervous system
Consists of somatic motor nerve fibres that conduct impulses from the CNS to skeletal muscles and allow conscious (voluntary) control of motor activities.
Motor (efferent) division of PNS- autonomic nervous system
an involuntary system consisting of visceral motor nerve fibres that regulate the activity of smooth muscle, cardiac muscle, and glands.
Two subdivisions, sympathetic- mobilizes body systems during activity
parasympathetic- rest and relaxation, conserves energy
Neurons
Nerve cells
Excitable cells that transmit electrical signals
Neuroglia
Glial cells
Small cells that protect neurons and help them to function
Four main Neuroglia of CNS
Astrocytes
Microglial cells
Oligodendrocytes
Ependymal cells
Astrocytes
regulate the chemical environment around neurons and play a role in exchanges between neurons and capillaries.
Most abundant,versatile and highly branched glial cells
Support and guide young neurons
Respond to nerve impulses
Etc.
Microglial cells
Monitor health and perform defence functions for neurons
Small,ovoid cells with thorny processes that touch and monitor neurons
Migrate toward injured neurons
Transform to phagocytize microorganisms and neuronal debris
Oligodendrocytes
Branched cells that wrap around CNS neuron fibres, forming insulating myelin sheath in thicker nerve fibres
Each oligodendrocyte can insulate dozens of nearby axons
Ependymal cells
Line the central cavities of brain and spinal cord and help circulate cerebrospinal fluid
Satellite cells
Surround neuron cell bodies
Function similarly to Astrocytes, but are in PNS
Schwann cells
Surround all peripheral nerve fibres and form myelin sheaths in thicker nerve fibres
Perform similar function as Oligodendrocytes
Vital to regeneration of damaged peripheral nerve fibres
Myelin sheath
a lipid-rich sheath of plasma membrane that wraps around part of axon and facilitates the transmission of electrical signals.
Proteins in the myelin help to hold the wrap together.
Axons and insulation
In CNS insulated by Oligodendrocytes
In PNS by Schwann cells
Myelin sheaths of PNS
formed by Schwann cells that wrap themselves around axon
have gaps called nodes of ranvier
Protect and electrically insulate axons (myelinated fibres) and increase the speed of nerve impulse transmission
Nodes of ranvier
Gaps in myelin sheath where axon collaterals can emerge
Non myelinated fibres
Do not contain sheath and conduct impulses more slowly
Myelin sheath in CNS
formed by oligodendrocytes
Myelin sheath gaps are present
White matter
Regions of brain and spinal cord with dense collections of myelinated fibres, usually fibre tracts
Grey matter
Mostly neuron cell bodies (soma) and non myelinated fibres
