REGULATION Part I Nervous Regulation (the nervous system)

I. Regulation is the life function by which organisms coordinate and control of their own life activities to maintain life. Regulation includes both nerve control (animals only) & chemical control (all organisms). A. Nerve control- nerve control depends mainly on the functioning of the neurons (nerve cells).

1. Stimulus is any change that occurs in the external or internal environment of an organism that initiates an impulse. Ex) light, sound & chemical change 2. Impulse an electro-chemical charge generated along a neuron 3. Response is a reaction to a stimulus a. Receptors - structures specialized to detect only 1 type of stimuli ex.) Eye for light, ears for sound, skin for touch, nose for smell, tongue for taste b. Effectors - organs of response such as muscles or glands

Basic Sequence of Events 1. Stimulus activates a receptor 2. Receptor triggers impulse in a nerve pathway 3. Impulse is received by effector that responds B. Structure of NEURON A cell specialized for the transmission of nerve impulses from place to place in the body. It is composed of:

1) DENDRITES fibers that detect the stimulus and generate impulses toward the cyton. 2) CYTON cell body containing the nucleus. 3) AXON- - a fiber that transmits the impulse away from the cyton toward the terminal branches 4) MYELIN SHEATH layers of white, fatty substances produced by Schwann cells that surround some axons 5) TERMINAL BRANCHES - ends of the axons which secrete neurotransmitters (consists of synaptic knobs)

C. Synapse is a junction between adjacent neurons or between neuron and effector D. Neurotransmitters are special chemicals, produced and secreted by the neuron's synaptic knob (located at a terminal branch) that serves to carry impulses from 1 neuron to the next. ex) acetylcholine E. Types of Neurons (nerve cells) nerves are bundles of axons or dendrites that are bound together by connective tissue.

1. Sensory Neurons carry impulses from receptors toward the spinal cord and brain (longest) 2. Interneurons -(also called associative neurons) carry impulses from one neuron to another in the brain and spinal cord (short) 3. Motor Neurons - carry impulses from the brain and spinal cord to the effectors.

How a Nerve Impulse is sent through a neuron... II. Resting Neuron A. Transmission of nerve impulse is made possible by a difference in electrical charge between the outer (+) and inner (-) nerve cell membrane. III. Nerve Impulse A. As an impulse is carried in a neuron, there is a reversal of polarity (the outside becomes negative and the inside becomes positive.) B. This reversal of polarity occurs in a small area of the membrane where the impulse is.

C. Once the impulse passes, ions pass from the inside back to the outside and the polarity is returned back to that of the resting neuron. IV. Transmission at the synapse A. During impulse (electrical energy), a neurotransmitter, acetylcholine and norepinephrine, is released into the synaptic cleft (space between 2 neurons). B. The electrical impulse is now converted into a chemical response that stimulates the adjoining neuron to receive the transmitted impulse. C. Once the impulse has been transmitted, cholinesterase break down the acetylcholine to clear the way for new signals.

Human- the human central nervous system consists of a highly developed brain and dorsal nerve cord (found in all chordates) that permit impulses to travel over definite pathways. There is also many highly developed receptors. One disease (caused by a virus) associated with the destruction of nerve cells is polio.

I. CENTRAL NERVOUS SYSTEM (CNS): -made up of brain & spinal cord which are protected by cranium & vertebrae -also protected by: 1) meninges- 3 tough membranes that enclose & protect brain + spinal cord 2) cerebral spinal fluid- liquid that cushions nervous tissue from shock and fills space between meninges, in ventricles (4 spaces with in brain),& in spinal canal of spinal cord

A. BRAIN 1. receives 20% of blood from the heart (glucose is the major energy source) 2. has 3 divisions, each having specialized functions a. Cerebrum- largest part (2/3 of brain); center of intelligence & awareness; controls thought, memory, learning, emotions, seeing, hearing, taste, smell, touch -these are examples of voluntary movements b. Cerebellum- controls balance & muscular behavior c. Medulla- controls breathing, heartbeat, digestive tract movements; gland secretions, coughing, sneezing, swallowing, vomiting -these are examples of involuntary movements

CEREBRAL CORTEX- (outermost layer) has 3 functions 1. sensory areas -receives and interprets impulses from sense receptors 2. motor areas- - initiates impulses for all voluntary movement 3. associative areas - responsible for memory, learning, and thought

B. SPINAL CORD 1. lies within the column of the vertebrae that is continuous with the brain. 2. inner layer of cord has "H" shaped gray matter and white matter surrounding it 3. it has two main functions a. connecting brain to the peripheral nerves b. controls reflexes

Receptor --> Sensory --> Interneuron --> motor

a. Reflexes- involuntary, automatic responses to a given stimulus (no brain involvement) ex.) knee jerk, withdrawal reflexes b. instincts- complex inborn behavior patterns consisting of senses or a chain of reflexes ex.) building a nest, spinning a web

II. PERIPHERAL NERVOUS SYSTEM {located outside CNS} -cranial nerves (nerves connect to the brain; 12 pairs) -spinal nerves (nerves that connect to the spinal cord; 31 pairs) -it consists of 2 specialized nervous systems A. Somatic Nervous System controls voluntary muscles 1. consists of sensory & motor neurons

B. Autonomic Nervous System made of nerves that control cardiac muscle, glands & smooth muscle. It coordinates involuntary actions. -consists of motor neurons 1) Parasympathetic Nervous System 2) Sympathetic Nervous System -both parts of the autonomic nervous. system. are antagonistic to each other

III. Some ANOMALIES of the Nervous System A. Cerebral Palsy A congenial (existing at birth but not hereditary) disease characterized by a disturbance of the motor functions. B. Meningitis - inflammation of the membranes surrounding the brain & the spinal cord. C. Stroke- A disease resulting from a cerebral hemorrhage or a blood clot in the cerebral vessel which may result in brain damage. D. Polio - A viral disease of the CNS which may result in Paralysis and is preventable through immunization. E. Rabies- A contagious infection of the CNS, caused by specific virus that enters the body through the bite of an animal.