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The Nervous System Chapter 48

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1 The Nervous System Chapter 48
By: Julia Moen

2 Evolution The ability of cells to respond to the environment has evolved over billions of years Plants use signal-transduction pathways to recognize environmental signals and create cellular responses; they have impulses called action potentials that resemble the nervous system messages in animals (Chapter 39) Embryonic development of the vertebrate brain reflects the evolution from three anterior bulges of the neural tube (forebrain, midbrain and hindbrain)

3 Nervous systems range in complexity from simple nerve nets to highly centralized nervous systems having complex brains and central nerve cords. The nerve cord lies near the ventral body surface in invertebrates and near the dorsal surface in vertebrates.

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5 Why is the Nervous System Necessary?
The Nervous System is responsible for picking up stimulus and signals, processing them and creating a reaction (either voluntary or involuntary) The Central Nervous System (CNS) processes information The Peripheral Nervous System (PNS) communicates sensory and motor signals between the CNS and the rest of the body

6 The Nervous System Consists of Two parts
A. Central Nervous System (CNS) B. Peripheral Nervous System (PNS) I. Sensory II. Motor a. Somatic System b. Autonomic System i. Sympathetic ii. Parasympathetic

7 In terms of function, Somatic NS voluntary muscles and reflexes vs Autonomic NS visceral/smooth and cardiac muscle Sympathetic NS increases energy expenditure prepares for action Parasympathetic NS decreases energy expenditure gains stored energy these have the opposite effects on the same organs --OR-- In terms of location, Peripheral NS sensory and motor neurons vs Central NS (CNS) interneurons: brain and spine covered with three membranes, the meninges inflammation of these is called meningitis brain has gray matter on outside and white in center spine has white matter on outside and gray in center

8 Neuron Terminal Branch

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10 A. The Neuron cell body with a nucleus and other organelles
cytoplasmic extensions dendrites- can have hundreds; sensory; receive incoming messages from other cells and carry the electrical signal to the cell body axons- only one, but can be several feet long in large mammals; transmits an impulse from the cell body outward to another cell

11 A. The Neuron Myelin Sheath- speeds the passage of an impulse
Glial cells are essential for the normal functioning of neurons; there are many more glial cells than neurons Schwann cells- glial cells that form the myelin sheath Nodes of Ranvier-between myelin sheaths Terminal Branch-works with synapse to as the final point the impulse is in one neuron before going to the next

12 B. Types of Neurons Sensory neurons- receive an initial stimulus from a sense organ or from another neuron Motor neuron- stimulates effectors (muscles or glands) Interneuron or association neuron- within spinal chord and brain; receives sensory stimuli and transfers the info directly to a motor neuron or to the brain for processing Example of a sense organ- eyes or ears Motor neurons can stimulate muscles to contract

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14 Resting Potential Membrane potential---difference in electrical charge between the cytoplasm (negative ions) and extracellular fluid (positive ions) Measured in microelectrodes Potential should be between -50 mV and -100mV Polarized state (resting potential)--- neuron in an unstimulated state has a membrane potential of -70mV Nerves can only fire if the stimulus is large enough to overcome the resting potential Negative sign means that the inside of the cell is negative relative to the outside of the cell

15 Gated Channels The sodium-potassium pump maintains the polarization by actively pumping ions that leak across the membrane Gated-ion channels- in neurons; open and close in response to stimuli; help transmit electrical impulses Sodium ion-gated channels---when opened, sodium flows into the cytoplasm; decreases polarization (to about -60mV, usually); depolarized Potassium ion-gated channel----when opened, potassium levels are increased in the cell and the membrane becomes hyperpolarized and therefore harder for the neuron to fire Inside the cell Na+ has a lower concentration than K+

16 Action Potential Impulse Generated in axons
action potentials relay different intensities of information by changing the frequency of the action potential i.e. a strong stimulus sets up more action potentials than a weak one Wave of depolarization-reverses polarity of the membrane (Na+ in, K+ out) With this change, the message moves along the axon Refractory period-quickly (a few milliseconds) reverts back to correct potential When a stimulus is strong enough to overcome the membrane potential, the permeability of the membrane changes. Sodium channels open and sodium floods into the cell, down the concentration gradient. During the refractory period, another stimulus can not be responded to which makes sure the impulse moves in one direction only

17 Synapse Electrical Chemical In crustaceans
Impulses travel from neuron to neuron with no delay Much less common Chemical Uses Ca2+ Synaptic vesicles contain thousands of neurotransmitters (substance is released as an intercellular messenger) Acetylcholine is a common example (see page 1037) The cytoplasm at the terminal branch of the presynaptic neuron contains many vesicles, each containing thousands of molecules of neurotransmiter. Ca molecules rush into terminal branch and stimulates vesicles to fuse with the presynaptic membrane and release the neurotransmitter by exocytosis into the synaptic cleft. The neurotransmitter either inhibits or excites the postsynaptic cell. The enzyme esterase destroys the neurotransmitter

18 Synapse

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20 The Nervous System Consists of Two parts
A. Central Nervous System (CNS) B. Peripheral Nervous System (PNS) I. Sensory II. Motor a. Somatic System b. Autonomic System i. Sympathetic ii. Parasympathetic Sensory- conveys info from sensory receptors or nerve endings

21 Autonomic System Sympathetic Parasympathetic Fight or flight response
Increases heart and respiratory rate Liver converts glycogen to glucose Bronchi of lungs dilate and increase gas exchange Adrenalin raises blood glucose levels Opposes the sympathetic system Calms the body Decreases heart and respiratory rate Enhances digestion

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23 See page 1041

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26 The Brain Brainstem-contains the Medulla and pons, and the midbrain; control areas include movement of the eyes and mouth, relaying sensory messages, hunger, respirations, consciousness, cardiac function, body temperature, involuntary muscle movements, sneezing, coughing, vomiting, and swallowing Pons-A deep part of the brain, located in the brainstem; contains many of the control areas for eye and face movements Medulla- The lowest part of the brainstem; contains important control centers for the heart and lungs; extremely vital

27 The Brain con’t Thalamus- main input center for sensory information; incoming info sorted in thalamus Cerebellum- back of the head; coordinates voluntary muscle movements and maintains posture, balance, and equilibrium. Hypothalamus-posterior pituitary hormone and releasing hormones; regulates temperature, hunger, thirst and other basic survival mechanisms; circadian rhythms

28 Cerebrum Frontal Lobe-The largest section of the brain located in the front of the head; involved in personality characteristics and movement. Parietal lobe-The middle part of the brain; helps to identify objects and understand spatial relationships; also involved in interpreting pain and touch in the body. Occipital lobe-back part of the brain; involved with vision. Temporal lobe-The sides of the brain; involved in memory, speech, and sense of smell.

29 Cerebrum Different regions are specialized for different functions
Main functions of Cerebrum include Language and Speech, Emotions (Limbic System), Memory and Learning, Human Consciousness etc.

30 Interdependence The nervous system often works with the endocrine and immune systems to regulate body functions and behavior In all systems many functions are started because of signals to either voluntary or involuntary systems Respiratory, Muscular, Digestive

31 Main Points Nervous systems gather, process and respond to information from stimuli Networks of neurons work together to form the nervous system Every cell has a membrane potential that must be overcome to transport a signal The signal is passed as an impulse along axons The same neurotransmitter can produce different effects on different types of cells The nervous system is composed of the CNS and the PNS The separate parts of the peripheral nervous system interact in maintaining homeostasis The cerebrum is the most highly evolved structure in mammal’s brains

32 Diseases and Disorders
There are many common diseases and disorders because the nervous system is such a complex system- there is much that can go wrong The list of Neurological diseases and disorders include Parkinson’s Disease, Cerebral Palsy, Multiple Sclerosis, Alzheimer’s Disease, Stroke, Epilepsy/Seizures,

33 Multiple Sclerosis A chronic disease of the nervous system that can affect young and middle-aged adults. The myelin sheaths surrounding nerves in the brain and spinal cord are damaged, which affects the function of the nerves involved. The underlying cause of the nerve damage remains unknown. Multiple Scerosis affects different parts of the brain and spinal cord, resulting in typically scattered symptoms. These can include: Unsteady walk and shaky movement of the limbs Rapid involuntary movements of the eyes Defects in speech pronunciation Inflammed optic nerve

34 Cerebral Palsy Non-progressive disorder
results from damage to the brain before , during or directly after birth The most common disability is a spastic paralysis. Sensation is often affected, leading to a lack of balance and intelligence posture and speech are frequently impaired. Other associated features include epilepsy, visual impairment, squint, reduced hearing, and behavioral problems.

35 Sciatica Often refers to any pain in lower back, which is relatively common Caused by compression of, or damage to, a nerve or nerve root Stiff pain felt down the back and outer side of the thigh, leg and foot Numbness and weakness in the leg

36 Really informational! 
Nervous System Really informational! 

37 Works Cited http://www.dsart.com/Gallery/brain.htm
Barron’s AP Biology Study Guide Biology 6th Ed. Campbell and Reece Google images


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