The Nervous System

By: Amor Colombres & Cellena Ward

Cnidaria: Hydra• Hydras have a nerve net that connects receptors with

muscle and gland tissues, but they do NOT have a brain or any nerve cords to connect their nervous system.

A Hydras Nervous System

• The neurons of a hydra are connected by the synapse and can be in either direction of the synapse.

• Unlike other animals the hydra does NOT have any grouping of cell bodies.

• The hydra also does NOT have any cells that are specialized for touch or chemical detection.

Annelida: EarthWorm

• An earthworm has both a central and peripheral nervous system• In the central nervous system the cerebral ganglion is connected to the

ventral nerve cord and runs the entire length of the body. Each segmental ganglion branches off of the ventral nerve cord, therefore connecting all of the segments to the brain.

Peripheral Nervous System

• The peripheral nervous system contains neurons that branch off of the central nervous system and each neuron transmit messages to the cerebral ganglion:

Sensory neurons carry impulses from receptors to the nerve cords.

Motor neurons carry impulses from the nerve cord to effectors.

The Adaptations of Earthworms

• The nervous system is very critical to the earthworms because it helps to coordinate with the nerve responses and allows the earthworm to survive.

• Over time the Earthworms have adapted receptors that make them sensitive to:

Light Pressure Vibrations Heat Chemicals

Arthropoda:Grasshopper

• Grasshoppers also have a central and peripheral nervous system.

• The peripheral nervous system consists of the sensory system. while the central nervous system consists of the ventral nerve cord.

• Since the grasshopper is a segmented insect each segment

has its own interganglionic.

The Advantages of Grasshoppers

• Grasshoppers have: Antennae Eyes Taste and Sound Organs

• Grasshoppers also have four important neurons that connect to the extensor muscle.

fast extensor tibiae slow extensor tibiae common inhibitor dorsal unpaired median

neuron of the extensor tibiae

Parkinson's Disease• Parkinson's disease is considered a motor system

disease because it affects the motor skills first.• Causes:

Old Age Genetics When the nerve cells in the brain that make

dopamine are slowly destroyed. Nerves that are not sensitive to dopamine

cause Parkinson in young children • Symptoms:

Tremor Difficulty swallowing Loss of automatic movements Rigid Muscles Change in Speech Impaired Posture or Balance

The Cures of Parkinson's

• Cures: Levodopa (L-dopa), Sinemet, levodopa and carbidopa (Atamet) Pramipexole (Mirapex), ropinirole (Requip), bromocriptine (Parlodel) Selegiline (Eldepryl, Deprenyl), rasagiline (Azilect) Amantadine or anticholinergic medications -- to reduce early or mild

tremors Entacapone -- to prevent the breakdown of levodopa Changes in lifestyle

Epilepsy

• Is a disease of the nervous system that affects the temporal lobe and causes repeated convulsions that eventually changes a person's attention or behavior.

•Causes: Damage to the brain tissue. Dementia Traumatic brain injury Infections of the nervous system Brain problems at birth Brain tumor Abnormal blood vessels in the brain

Continuation of Epilepsy

•Symptoms: Partial seizure Absence seizure

•Treatment: Vitamins and supplements Lifestyle changes Surgery to remove abnormal

brain cells Anticonvulsants Surgery to insert vagus

nerve stimulator

Embryonic Development of Vertebrates

• The central nervous system develops from the hollow, dorsal nerve chord. The central canal and ventricles form in the cavity of the nerve chord.

• These cavities are filled with cerebrospinal fluid.

Grey and White Matter

•Grey matter consists of neuron cell bodies, dendrites, and unmyelinated axons.

•White matter consists of bundled axons with myelin sheaths.

• In the spinal chord, the white matter surrounds the grey matter, so the function goes with the anatomy, linking the CNS with sensory and motor neurons of the PNS

Glia Cells

• Non-neural cells that form myelin, help maintain homeostasis, and provide support and protection for neurons in the cell.o Ependymal cellso Astrocyteso Oligodendrocyteso Schwann cellso Microglia

• In embryonic development, radial glia form a track for new neurons migrate from the neural tube, astrocytes later form junctions along these lines.

• In the blood-brain barrier these cells control the extracellular environment by restricting the entry of substances from the blood into the brain.

Autonomic Nervous System

• Part of the peripheral nervous system that regulates smooth and cardiac muscle.

• Three parts:o Sympathetic division controls arousal

and energy generation i.e. heart beating faster

o Parasympathetic division controls calming and self-maintenance functions i.e. heart rate decreasing

o Enteric division regulates secretion and peristalsis. occurs in digestive tract,

pancreas, and gall blader

The Vertebrate Brain is Regionally Specialized

• Three regions:o Forebrain

o Midbrain

o Hindbrain

• The forebrain develops into two regions, the diencephalon and telencephalon.

• The midbrain develops into the mesencephalon.

• The hindbrain develops into the metencephalon and myelencephalon.

The Cerebrum

• Controls skeletal muscle contraction, center for learning, emotion, memory, and perception

• The cerebral cortex is vital for perception, voluntary movement, and learning.

• The corpus callosum is a structure that enables the right and left hemispheres to communicate.

• Deep in the white matter there are basal nuclei, which are centers for planning and learning movement sequences.

• Damage during embryonic development can cause Cerebral Palsy.

The Diencephalon

• Becomes the thalamus, hypothalamus, and epithalamus in children and adults.o Thalamus- main input

center for sensory information.

o Hypothalamus- the body's biological clock and thermostat. Partakes in regulation of systems.

o Epithalamus- in charge of the pineal gland, which produces serotonin.

The CerebellumMajor function is to coordinate movement and balance.

•Receives sensory information about the positions of joints and the lengths of muscles.

•Contains the center for the auditory and visual systems.

•Has a lot to do with hand-eye coordination.

The Brainstem• Receives and integrates sensory information to regions of the brain

• The Pons and medulla oblongata transfer information between the PNS and the midbrain or forebrain.

Arousal and Sleep

• Regulated by the brainstem and cerebrum.

•Arousal is a state of awareness of external stimuli.

•Sleep is a state where external stimuli are received but not perceived consciously.o active state when the brain

condenses memories and learning.

• Controlled mainly by the reticular formation, network of neurons in the core of the brainstem that acts like a sensory filter.

Biological Clock Regulation• Cycles of sleep and

arousal are examples of a circadian rhythm.

• molecular mechanism that regulates gene expression and cellular activity

• The hypothalamus contains a group of neurons, suprachiasmatic nucleus (SCN), that coordinate circadian rhythms.

Emotions

• Many structures control emotions like the amygdala, hippocampus, and thalamus, or the limbic system.

Feeling emotion requires other structures in the brain, like the brainstem and cerebrum.

• The amygdala stores emotions as memories.

Language and Speech

• Physician, Pierre Broca, discovered Broca's Area which controls muscles of the face.

• Karl Wernicke found that when damaged, Wernicke's area, suppressed the ability to comprehend speech, but not to actually speak.

• Two regions work together in reading, generating words, speaking words, and hearing words.

Lateralization of Cortical Function

• Left hemisphere functions:o math and logical operations

• Right hemisphere functions:o recognition of faces and patterns, spatial

relations, and nonverbal thinking.

• Hemispheres trade information through the corpus callosum.

Frontal Lobe Function

• Phineas Gage had a 3 cm rod enter his skull just under his left eye and exited through the top of his head. The rod destroyed a very large portion of his frontal lobe. He was able to recover, but his emotions changed.

• This left a connection with the frontal lobe and emotional responses.

Changes in Synaptic Connections

• Neurons need to compete for growth-supporting factors, which direct neuron growth.

• Synapse elimination occurs because neurons form extra synapses then needed for its function, about half of original synapses are destroyed by the end of embryonic development.

Neural Plasticity

• The ability of the nervous system to be remodeled.

• Reshaping occurs at synapses.

• The connections are strengthened or weakened depending on activity between neurons.

• Autism is due to a disruption remodeling of synapses.

Memory and Learning

• Keep memories in our short-term memory until it becomes irrelevant.

• When memories are remembered they are stored in our long-term memory.

• Both memories store information in the cerebral cortex.

Long-Term Potentiation (LTP)

• The increase of the strength of the flow of communication across synapses.

• For this to occur there needs to be a high-frequency series of action with a presynaptic neuron.

• Glutamate receptors in the postsynaptic membrane change in response to depolarization, allowing LTP by inserting glutamate receptors.

Stem Cells in the Brain

• Develop into neurons that mature and migrate to the hippocampus to be included into the nervous system.

• Researchers are trying to use neural stem cells to replace lost brain tissue.

Bibliography

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Board, A.D.A.M. Editorial. "Causes, Incidence, and Risk Factors." Epilepsy. U.S. National Library of Medicine, 18 Nov. 0000. Web. 25 Mar. 2012. <http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001714/>.

Reece, Urry, Cain, Wasserman, Minorsky, and Jackson. San Francisco: Pearson Education, 2011. Print.