I.Composed of neural tissue, blood vessels, and connective tissue 2.Read General Functions of the...

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I. Composed of neural tissue, blood vessels, and connective tissue



2. Read General Functions of the Nervous System and take notes.

A. The central nervous system is made up of the brain and spinal cord

B. The Peripheral nervous system is made up of the nervesC. Nerve tissue is made up of NEURONS(nerve cells) and

NEUROGLIA (supporting cells)

B. Functional differences of neurons

1. SENSORY neurons carry impulses from body to the brain via spinal cord.

2. INTERNEURONS form links between neurons by directing sensory neurons to appropriate processing regions or transferring impulses to motor neurons.a. Found in brain and spinal cord

3. MOTOR neurons (efferent neurons) carry impulses to EFFECTERS (muscles and glands).

MAKE MOTOR NEURON POSTERS NOW

C. SCHWANN cells (neuroglia) surround peripheral nerves fiber to make MYELIN SHEATH (speeds up impulse conduction).





D. Astrocytes (neuroglia) are often found between neurons and blood vessels. They support and hold structures together, help metabolism of certain substances, regulate ion concentrations, form scar tissue to fill gaps in the brain caused by injury, and may have a nutritive function.

E. OLIGODENDROCYTES form myelin in the brain and spinal cord. Unlike Schwann cells, oligodendrocytes can myelinate more than one axon.

F. MICROGLIA are found in the CNS and help phagocytize bacterial cells and cellular debris.



G. EPENDYMAL cells are ciliated and form the inner lining of the central canal of the spinal cord. They also cover the VENTRICLES of the brain. They help to circulate cerebrospinal fluid.

III. After injury, peripheral nerves are much more capable of regeneration than nerves in the CNS.



V. Resting potential (non-stimulated neuron)

IV. Cell membrane potential (potential difference in charges)

A. Cell membranes are polarized (charged) with a more positive outside and negative inside.

B. Results from Na+/K+ pump

C. K+ found intracellularly and Na+ found extracellularly.

A. Na+ and K+ diffuse. The outside is slightly positive because the membrane is more permeable to Na+

B. ATP is used to pump Na+ and K+ (further charge separation)

C. Local potential changes

1. Neurons get excited by stimuli, causing membrane gates to open and ions to flow

a. HYPERPOLARIZATION (inside becomes more negative)

or

b. DEPOLARIZATION (becomes more positive)

Changes depend on the intensity of the stimulus

2. If neurons depolarize enough, the membrane potential reaches a THRESHOLD POTENTIAL and an ACTION POTENTIAL will begin

a. Oftentimes SUMMATION (combined effects from more than one stimulus) is needed for an action potential.

VI. Action potential

A. At resting, Na+ channels are closed. They open briefly when the threshold is reached and increase Na+ permeability. Na+ rushes inward and intracellular fluid becomes more positive (DEPOLARIZATION).



B. Once a particular voltage is reached, gated Na+ ions close.

C. At the same time, slower gated K+ channels open. K+ diffuses outward and the neuron becomes negative again (REPOLARIZATION).

D. Neuron remains in resting potential until it is stimulated again.

E. Action potentials happen at the axons, but not at the dendrites.



VII. Nerve impulses are all or none.

F. An action potential in one neuron can stimulates the adjacent neurons to its threshold level.

VIII. After a nerve impulse, there is a REFRACTORY period when when a threshold stimulus will not trigger another impulse.

A. During the ABSOLUTE REFRACTORY PERIOD (last 1/12500 of a second) the membrane is changing in Na+ permeability and cannot be stimulated.

B. A RELATIVE REFRACTORY PERIOD follows in which the membrane is is finishing repolarization. Only a high intensity stimulus will trigger an impulse.

IX. Speed of nerve impulses



X. Nerve impulses pass from one neuron to the next at the synapse.

A. Myelinated axons send messages more quickly than non-myelinated ones.

B. Axons with greater diameter send impulses more quickly.

A. There are SYNAPTIC KNOBS at the AXON TERMINALS full of SYNAPTIC VESICLES.

1. Synaptic vesicles are full of NEUROTRANSMITTER chemicals that send signals from one neuron to the next.



A. When a nerve impulse reaches a synaptic knob, voltage sensitive Ca+ channels open as Ca+ flows inward. This causes synaptic vesicles to fuse with the membrane and release neurtotransmitters that bind with receptors on adjacent neurons.

B. Endocytosis eventually returns neurotransmitters to the cytoplasm.

1. Enzymes may break down neurotransmitters to stop signal transmission.

2. Some neurotransmitters are taken back to the synaptic knob in a process called reuptake.

I. The central nervous system - brain and spinal cord connected by brainstem.



A. The organs of the central nervous system are surrounded by bones, membranes, and fluid that offer protection.

II., The spinal cord is continuous with the brain.

A. Each of its 31 segments gives rise to a pair of spinal nerves (communication).

III. The CEREBRUM

A. Largest part of the brain.

B. Made of two CEREBRAL HEMISPHERES connected by a bridge of nerve fibers called the CORPUS CALLOSUM

1. In the frontal lobe: concentrating, planning, complex problem solving, emotional behavior and realization of consequences.

C. The cerebrum provides higher brain functions: interpreting impulses from sense organs, initiating voluntary muscular movements, storing information as memory, and retrieving this information in reasoning.



D. Lobes of the cerebral hemispheres are named for the underling bones (FRONTAL, PARIETAL, TEMPORAL, OCCIPITAL, INSULA)

2. In the parietal lobes: understand speech and reading, store memories of visual scenes, music, and other complex sensory patterns.

3. In the occipital lobes: analysis of visual patterns and recognition.

4. The WERNICKE’S AREA, where the parietal, temporal, and occipital association areas join, plays the primary role in complex thought processes


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1. Although both cerebral hemispheres participate in basic functions, most people have a dominant hemisphere.

IV. The BASAL NUCLEI deep in the cerebral hemisphere inhibits dopamine to inhibit muscular functions.

V. The DIENCEPHALON is located between the cerebrum and the brainstem and is made up of the THALAMUS, HYPOTHALAMUS, and the PINEAL and PITUITARY gland.



A. The thalamus is a selective gateway for sensory impulses. It acts as both a messenger and an editor.



B. The hypothalamus maintains homeostasis by regulating heart rate and blood pressure, body temperature, water and electrolyte balance, control of hunger and body weight, control of movements and secretions of the intestines and stomach, sleep and wakefulness, and production of substances that stimulate the pituitary gland.

VI. The LIMBIC SYSTEM is made of parts of the diencephalon, hypothalamus, thalamus, basal nuclei, and cerebrum and controls emotional experiences and expression.





VII. The BRAINSTEM connects the brain to the spinal cord and is made of the MIDBRAIN, PONS, and MEDULLA OBLONGATA.

A. The midbrain has reflex centers.

B. The pons transmits impulses from the cerebrum to centers within the CEREBELLUM.

C. The medulla oblongata controls heart rate, regulation of smooth muscles, and rate, rhythm, and depth of breathing.

X. A complex network of nerves called the RETICULAR FORMATION extends throughout the medeulla oblongata, pons, and midbrain. When it gets stimulated, it cause the cerebral cortex to “wakeup”.

XI. The cerebellum coordinates skeletal muscles and maintains balance.



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