Animal Nervous Systems

Updated 2007-06-06 23:42


Animal Nervous Systems.


Nervous system-the system of nerves in an animal including the brain, spinal cord, nerves, and ganglia.
What is the main purpose of the nervous system?Coordinate the bodily functions of animals and to aid the animals in interacting with the environment.
Neural coordination occurs in all but…the simplest of animals
What coordinates movement in cnidarians (like jellyfish and hydra)?A nerve net
What is the Nervous system in annelids and arthropods composed of?A ventral nerve cord with segmental ganglia, a brain and well-developed sensory receptors
In some arthropods like cockroaches, where is the brain located?It is located throughout the body consisting of several ganglia.
Nervous system in flatworms consists of…widely separated ventral nerve cords
Who has the most complex nervous systems of all invertabrates?Chephalopods like squid with highly developed brains and very large nerve cells or neurons
Dendrite-branched extension of nerve cell that conducts impulses toward cell body
Axon-the appendage of the neuron that transmits impulses away from cell body
Neurons-any of the impulse conducting cells that constitute the brain, spinal column and nerves consisting of a nucleated cell body with one or more dendrites and a single axon.
What makes squid neurons so popular in neurophysiology research?The large size of their neurons
What are the two subdivisions of vertebrate nervous systems?The central nervous system and the peripheral nervous system
What is the central nervous system composed of?The brain and spinal cord
Brain-the part of the CNS enclosed in the cranium of humans and other vertebrates serving to control and coordinate the mental and physical actions
What is the peripheral nervous system composed of?Cranial and spinal nerves
Spinal cord-connecting link between brain and spinal nerves all over the body/the cord of nerve tissue extending through the spinal canal of the spinal column
Central nervous system-the part of the nervous system comprising the brain and spinal cord
Peripheral nervous system-the portion of the nervous system lying outside the brain and spinal cord
Cranial nerves-any of the nerves arising from the brainstem and exiting to the periphery of the head through skull openings like olfactory nerve, optic nerve etc.)
Where are cranial nerves located?The extend from the spinal cord to all parts of the body except the head.
Spinal nerve-any of a series of paired nerves that originate in the nerve root of the spinal cord and emerge from the vertebrae on both sides of the spinal column, each branching out to a region in the neck, trunk or limbs
What has the most advanced nervous system of all animals?mammals
What does the nervous system provide?Rapid coordination and control of body function by transmitting impulses over neuron processes
Impulse-a progressive wave of excitation over a nerve or muscle fiber having an either stimulating or inhibitory effect
Where do the impulses originate?Either the brain or receptors
Receptors-a specialized cell or group of nerve endings that responds to sensory stimuli
Where are the effectors carried to?Effectors
Effectors-where the action occurs (muscle and glands)
What two basic type of cells make up the neural system?Neurons and neuroglial cells
What do neurons do?Transmit impulses
What do neuroglial cells provide?Support and prevent contact of neurons except in certain sites
Nerves-bundles of many neurons
Cell body-(integrates incoming signals and generates signal to axon)enlarged portion of the neuron that contains the nucleus
Dendrites-(collect electrical signals)receive impulses from receptors or other neurons and carry them toward the cell body(many can exist on neuron)
Axons-(passes signals to dendrites of another cell or to an effector)carry impulses away from cell body (usually only one)
What are neuron processes of the peripheral nervous system enclosed by?A covering of Schwann cells
What is different in larger processes ?There’s a inner mycelin shealth and outer neurilemma
Shwann cells-provide a pathway for the regeneration of neuron processes and are essential for regrowth
Are there Schwann cells in CNS?No but neuroglial cells called oligdendrocytes form myelin sheath
Inner myelin sheath-a fatty insulating material in composed of multiple wrappings of Schwann cells in larger processes.
Myelin sheath-serves as insulator that speeds nerve impulses to muscles and effectors
Nodes of Ranvier-minute spaces between Schwann cells where the neuron process is exposed
Are impulses transmitted more rapidly with myelinated or unmyelinated fibers?Myelinated
Invertebrates have what kind of fiber and what do they do because of having unmyelinated fibers?Unmyelinated, so the impulses go slow. To compensate this, invertebrates have much larger neurons to speed up transmission.
Synapse-junction of an axon tip of one neuron and a dendrite of another neuron
Neurotransmitter-any chemical substance that transmits impulses across synapse to muscle, nerve, or gland and triggered by impulses passing along the axon
Synaptic knob-axon tip
Synaptic cleft-minute space between the neurons
What does the neurotransmitter bind with and what does this produce?Receptor on photo synaptic membrane, and this produces stimulation or inhibition of impulse formation
What inactivates the neurotransmitter immediately after stimulation or inhibition of impulse?Enzyme, which prevents continuous stimulation or inhibition.
How does the direction of neural impulses across a synapsis go?Axon to dendrite because only axon tips can release neurotransmitters onto another neuron.
Name 2 stimulating neurotransmitters-acetylcholine and nor epinephrine
Name 2 inhibiting neurotransmitters-GABA and glycine
Spinal cord-the cord of nerve tissue extending through the spinal canal of the spinal column
What is the spinal cord covered by?Meninges
Meninges-3 layers of protective membranes
Where is spinal cord located?Extends from brain stem down to the vertebral canal
What does the spinal cord act as?The connecting point of the brain and spinal nerves
Gray matter-located in interior of spinal cord and composed of neuron cell bodies and unmyelinated neuron processes
White matter-located around gray matter and composed of myelinated neuron processes
What makes it a white color?Myelin
What happens in the white matter?Impulses are carried up and down the spinal cord by neuron fibers.
How many spinal nerves o humans have?31
What does spinal nerve carry(2 things)?Sensory neuron fibers and motor neuron fibers
Sensory neuron fibers-carry impulses from sensory receptors to the spinal cord
Motor neuron fibers-carry impulses from the spinal cord to an effector
How do spinal nerves join the spinal cord?Via a dorsal root and ventral root
Dorsal root-the more posterior of the two nerve fiber bundles of a spinal nerve that carries sensory info to the central nervous system
Ventral root-part of spinal nerve consisting of motor fibers that arises from the anterior section of the spinal cord
Dorsal root ganglion-a swelling on the dorsal root that contain sensory neuron cell bodies
Where are the motor neuron cell bodies located?In the gray matter of the spinal cord
Brain-control center of the nervous system
What is the brain covered with?menings
Cerebrospinal fluid-fluid between the brain and menings which provides cushion to absorb shock
How many cranial nerves are attached to the brain?12 all but one innervates (supplies) structures in head and neck
What nerves innervate internal organs?Vagus nerves
Cerebrum-largest part of the brain
What does cerebrum consist of?Right and left cerebral hemispheres separated by a median of longitudinal fissure
Longitudinal fissure-deep groove that divides the cerebrum into right and left hemispheres
Corpus callosum-mass of neuron fibers which enables impulses to pass between the 2 hemispheres
Cerebral cortex-outside portion of cerebrum that is gray matter composed of neuron cell bodies with unmyelinated neuron processes
Gyri-ridges on cerebral cortex that inc surface area
Sulci-grooves on cerebral cortex that inc surface area
What does the cerebrum initiate?Voluntary action and interpretation of sensations (in humans its for will memory and intelligence)
Cerebellum-below cerebrum which is for muscle tone and muscular coordination (subconscious) and divided into left and right hemispheres by a shallow fissure
What is spinal cord covered by?Meninges (three layers of protective tissue)
What is the spinal cords purpose?Connects the brain and spinal nerves
What makes the white matter white?Myelin
Where are impulses carried up and down through?The spinal cord by neuron fibers in white matter
How many pairs of spinal nerves are there?31
Where do sensory neuron fibers enter?The spinal cord via the dorsal root
Where are sensory neuron cell bodies located?Dorsal root ganglion
How do motor neuron cell bodies exit?Via the ventral root
Where are motor neuron cell bodies located?In gray matter of spinal cord
What is the mammalian brain covered by?Menings
How many pairs of cranial nerves are there in the brain?12
All but one pair of cranial nerves innervate (stimulate) structures in the head and neck except this one. Vargus nerves that stimulate the internal organs
Question Answer
How is the surface area in the cerebral cortex increased?Gyri and sulci
Frontal cerebral lobeanterior to central suclcus for voluntary muscle movements and intellect
Parietal cerebral lobebetween frontal and occipital lobes for interpreting sensations from skin and speech
Temporal cerebral lobeinferior to frontal and parietal lobes for hearing and interpreting auditory sensations
Occipital cerebral lobeposterior part of cerebrum for vision
Hypothalamus-located just above the brain stem and functions as the main control center for the autonomic nervous system (hormones and homeostasis)
Hypophysis/pituitary gland-a major endocrine gland which is attached to the wall of the hypothalamus
Optic chiasma-anterior to the pituitary gland where optic nerve fibers cross to the opposite side of the brain
Brain stem-functions in linking of higher and lower brain areas
Pineal body-(in brain stem)secretes melatonin which helps regulate sleep/wake cycles and reproduc. Cycles
Pons-a rounded bulge on ventral side of brain stem which is the connecting pathway or higher functions like respiration and urination
Medulla oblingata-controls heart rate, blood pressure and breathing
EEG-a recording of the brain’s activity through electrodes
Ventricle-cavities four within brain… first 2 are thick third while last two are narrow
What is secreted in the ventricles?Cerebrospinal fluid
Alpha waves-most prominent in adults who are awake but relaxed and have their eyes closed
Beta waves-smaller than alpha waves and occurs when individuals exert specific mental effort like concentrating
Delta/theta waves-generally absent in awake adults but are prominent in sleep