Lesson 4: The Nervous System
NERVOUS SYSTEM: The system made up of the brain, spinal cord, and all the nerves of the body that regulates the body’s response to stimuli. Nervous System
The 2 parts of the Nervous System are the: CENTRAL NERVOUS SYSTEM PERIPHERAL NERVOUS SYSTEM
The CENTRAL NERVOUS SYSTEM is made up of the brain and the spinal cord. It receives and transmits information to and from the peripheral nervous system.
BRAIN: Control center of the nervous system. SPINAL CORD: The part of the body that functions as a relay station to and from the body and the brain. Nerve impulses to the body from the brain must go through the spinal cord. The spinal cord could function on its own. Central Nervous System
REFLEX: An automatic behavior of the body that involves movement activated by the spinal cord. It does not use the brain. This movement occurs before one is aware of it. Ex: emergency situation: Swerving to avoid on oncoming car. Spinal cord acts before the brain gets a chance. Spinal neurons are short, direct and strong: They have very few synapses to show them down. The reflexes provide an automatic protective device for the body.
HOW A REFLEX WORKS: A stimulus to the skin sends a nerve impulse to the spinal cord. The spinal cord sends an impulse to the muscle causing it to contract.
The PERIPHERAL NERVOUS SYSTEM is made up of all the nerves of the body outside the brain and the spinal cord. It is all the nerves outside the Central Nervous System. Composed of the spinal and cranial nerves. These connect the CNS to the rest of the body. It sends information to and receives information from the Central Nervous System.
Most nerves in the PNS are SPINAL NERVES: Nerves that interact with the brain via the spinal cord. They connect the brain to the body. The others are CRANIAL NERVES: Nerves that interact directly with the brain located in the head, back and shoulders. They do not link via the spinal cord. They connect the brain to the head. Spinal Nerves LUMBAR
Cranial Nerves
The two parts of the Peripheral Nervous System are the: SOMATIC NERVOUS SYSTEM AUTONOMIC NERVOUS SYSTEM
The SOMATIC NERVOUS SYSTEM is the part of the Peripheral Nervous System that contains sensory nerves and motor nerves. It picks up SENSATION. It controls the skeletal muscles and voluntary (deliberate or conscious) MOVEMENT of the body.
SENSORY NERVES: They pick up sensation and bring it to the brain and spinal cord. MOTOR NERVES: They get instructions from the brain and spinal cord and put the muscles into action.
Autonomic means “automatic,” “independent,” “functions on its own,” and “without conscious control.” The Autonomic Nervous System controls most bodily activities are not under one’s control. It controls the automatic (unconscious or involuntary) internal bodily functions. This system runs much of the body all by itself. Ex: breathing, digestion, heartbeat, saliva production, movement of pupils, etc…
It carries nerve impulses from the brain and spinal cord to the glands, organs, etc… This system controls the following: Glands. Pupils. Liver. Lungs. Stomach. Heart. Other Vital Organs… The ANS can be overridden by the higher brain: Panic, shock, stress, etc… Survival mechanisms in a crisis.
The two parts of the Autonomic Nervous System are the: SYMPATHETIC NERVOUS SYSTEM PARASYMPATHETIC NERVOUS SYSTEM
They determine how much energy an organ should have and when it should have it. They balance the body when sudden changes in energy are needed. In the absence of an emergency, the two parts of the ANS balance each other. Their function is to produce a balanced response in the body when sudden changes in energy are needed. They both conduct nerve impulses from the CNS to the body’s internal organs.
SYMPATHETIC NERVOUS SYSTEM: The part of the ANS that energizes the body and prepares it for an emergency. It conducts nerve impulses from the CNS to the organs. It is made up of nerves that stimulate internal organs. Its purpose is to stimulate activity. It expends energy.
The SNS acts as an accelerator in an emergency. SNS increases heart rate, slows digestion, raises blood pressure, causes liver to make more sugar, dilates pupils, etc… Examples: A person who is running will see his body respond by increasing heart rate, stimulating lung capacity, etc… The reaction a body has when it is frightened, or in danger.
PARASYMPATHETIC NERVOUS SYSTEM: C alms the body down after an emergency. Para means “opposite of.” Counter (opposite) system to the SNS. It is made up of nerves that inhibit internal organs. Conserves body’s energy and gets the system back in balance after the SNS has been activated. It reduces or conserves energy. The PNS acts as a brake in an emergency; it is the braking mechanism that slows down the SNS.
If the spinal cord is severed, the parts of the body below the damage have no way of communicating with the brain: Those parts are immediately paralyzed. PARALYSIS: The loss of the ability to voluntarily move a part of the body. Often, it also involves a loss of sensation of that body part. It can be temporary or permanent. It can be partial or complete.
In order to move, a muscle must be stimulated by a nerve. Paralysis can be caused by damage to : Brain cells. Muscles. CNS (brain and spinal cord). PNS (other nerves in the body). Cut nerve cells do not regenerate and paralysis is permanent. The amount of the body paralyzed by an injury depends on the area of the spinal cord injured. Mike Utley Detroit Lions
Forms of Paralysis: (Plegia=paralysis) PARAPLEGIC: Paralyzed in the legs. Caused by spinal cord damage below the neck. Ex: Mike Utley (Los Angeles Rams Football Player). QUADRIPLEGIC: (4) Paralyzed in the arms and legs. Caused by spinal cord damage in the neck region. Damage to the brain stem can result in paralysis of muscles that control automatic functions of the body such as breathing and swallowing: Ex: Christopher Reeves. Christopher Reeves Superman