Psychology Ch. 2 The Biological Basis for Behavior The Central Nervous System

The Nervous System

The Central Nervous System The central nervous system consists of the brain and the spinal cord. It is protected by enclosing sheathes called the meninges. In addition, the central nervous system is bathed in its own special nutritive “soup,” the cerebrospinal fluid. The cerebrospinal fluid nourishes the brain and provides a protective cushion for it.

The Spinal Cord “We talk of the brain and the spinal cord as two distinct structures, but in fact, there is no clear boundary between them; at its upper end the spinal cord enlarges into the brain stem.” The spinal cord connects the brain to the rest of the body through the peripheral nervous system. The spinal cord can be considered an extension of the brain. It runs from the base of the brain to just below the level of the waist.

Spinal cord- Def.- Complex cable of neurons that runs down the spine, connecting the brain to most of the rest of the body.

“Our communications superhighway” - Connects “information” to all locations within the body.

250,000 Americans- partially or fully paralyzed Accidents & Injuries: 250,000 Americans- partially or fully paralyzed ½: Trauma- car accidents, falls or gunshot wounds ½: Medical conditions- tumors, infections, disorders (M.S. or A.L.S.), diseases (polio) or birth defects (spina bifida). There are about 10,000 new spinal cord injuries every year; the majority of them (82%) involve males between the ages of 16-30. These injuries result from motor vehicle accidents (36%), violence (28.9%), or falls (21.2%). Quadriplegia is slightly more common than paraplegia.

Notes Extra: -The average age of spinal cord injured person is 31. -SCI injuries are most commonly caused by: Vehicular accidents 37% Violence 28% Falls 21% Sports-related 6% Other 8% -The most rapidly increasing cause of injuries is due to violence; vehicular accident injuries are decreasing in number. -89% of all SCI individuals are discharged from hospitals to a private home, 4.3% are discharged to nursing homes. -Only 52% of SCI individuals are covered by private health insurance at time of injury.

Notes Extra: Paralysis means you’ve completely lost muscle function. Your muscle is paralyzed (doesn’t move) no matter how hard you want it to.  Your muscle paralysis happens when something goes awry with the passage of messages between your brain and muscles. A paralyzed muscle is caused by a loss or impairment to a neural or muscular mechanism

Notes Extra: A cause of paralysis may affect an individual muscle or, more commonly, an entire region. Paralysis can be complete, partial, localized or widespread. The types of paralysis are classified into these regions: hemiplegia ~ one side monoplegia ~ only one limb paraplegia ~ both legs & trunk quadriplegia ~ legs, arms & trunk diplegia ~ same body region on both sides

Spinal Cord Injury: - Damage to the spinal cord that results in a loss of function such as mobility or feeling. - The spinal cord does not have to be severed. -“Broken back” or “broken neck” mean damage to the vertebrae.

Types of Spinal Cord Injury: Cervical injuries: Neck Patients with C-1 to C-4 spinal cord injuries generally use diaphragm function and require a ventilator to breathe. Other complications may include: Bowel and bladder dysfunction Difficulty regulating heart rate, blood pressure, sweating, and body temperature Neuropathic pain Muscle atrophy

Thoracic injuries: Chest Individuals with T-9 to T-12 injuries typically have control of their hands and arms, as well as good control of their abdominal muscles and trunk. Control of the hip flexors and legs is compromised, but sitting balance is usually good.

The spinal cord is made up of soft, jellylike bundles of long axons, wrapped in insulting myelin and surrounded and protected by the vertebral bones. Physical Description: In human anatomy, the spine is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs. It houses and protects the spinal cord in its spinal canal.

3 basic functions: 1. To carry motor impulses to the internal organs and muscles. 2. To carry information from the extremities and internal organs to the brain. 3. To permit reflex movement.

Upper motor neurons: The nerves inside the spinal cord. Functions: to carry messages back and forth from the brain to the spinal nerves along the spinal cord. Lower motor neurons: The nerves that enter and exit at each vertebral level and communicates with specific body parts.

Notes Extra: What Do Spinal Cord Injuries Really Cost? Length of initial hospitalization following personal injury in acute care units: 15 days Average stay in rehabilitation unit: 44 days Initial hospitalization costs following injury: $140,000 Average first year expenses for a SCI injury (all groups): $198,000 First year expenses for paraplegics: $152,000 First year expenses for quadriplegics: $417,000 Average lifetime costs for paraplegics, age of injury 25: $428,000 Average lifetime costs for quadriplegics, age of injury 25: $1.35 million Percentage of SCI individuals who are covered by private health insurance at time of injury 52% Percentage of SCI individuals unemployed eight years after injury 63%. (Note: unemployment rate when this article was written was 4.7%) Source: The University of Alabama National Spinal Cord Injury Statistical Center - March 2002

The Nervous System *Peripheral Nervous System

The Peripheral Nervous System The peripheral nervous system is made up of all those nerves that lie outside the brain and spinal cord. Nerves are bundles of neuron fibers (axons) that are routed together in the peripheral nervous system. - This portion of the nervous system is just what it sounds like: the part that extends outside the central nervous system.

The Peripheral Nervous System has two major divisions: 1. Somatic Nervous System Def.- The part of the peripheral nervous system that carries messages from the senses to the central nervous system and skeletal muscles.

The Somatic Nervous System is made up of nerves that connect to voluntary skeletal muscles and to sensory receptors. - All the things we can sense- sight, smell, hearing, taste and touch. - All our voluntary actions- eating, drinking, writing, etc.

2. Autonomic Nervous System Def.- The part of the peripheral nervous system that carries messages between the central nervous system and the internal organs. The autonomic nervous system is made up of nerves that connect to the heart, blood vessels, muscles, and glands. - Crucial to body functions, breathing, digestion, circulation, heart rate, perspiration, etc. - Mediates physiological reactions to emotions.

The Autonomic nervous system consists of two branches: Parasympathetic division: Def.- Branch of the Autonomic nervous system- it calms and relaxes the body. Sympathetic division: Def.- Branch of the Autonomic nervous system- it prepares the body for an emergency or reaction to stimuli. -mobilizes the body’s resources for fight or flight.