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Bi Sci 001

Wednesday March 17, 1999
Announcements: Exam on Friday, remember assigned seating.

Lecture notes:

The Nervous System

Includes: The Central Nervous System (CNS): the brain and spinal cord.
The Peripheral Nervous System (PNS): the nerves and ganglia.

The Peripheral Nervous System

Includes: Nerves leading into the spinal cord and brain.
Nerves leading from the spinal cord and brain.
The ganglia

There are 31 pairs of spinal nerves in humans. (one for each side of the body)

There are 12 pairs of cranial nerves which connect directly with the brain.

Some cranial nerves have only sensory dendrites, others have both sensory and motor axons or dendrites.

The Central Nervous System

Includes: The Spinal cord: resides within a hollow tube formed by the vertebrate.

    1. It is covered by 3 layers of tissue called the meninges. Purpose: protection.
    2. Gray matter has cell bodies and dendrites involved with reflexes.
    3. White matter: axons of interneurons - some form reflex arcs, others are sensory dendrites on the way to the brain, or motor axons running in the opposite direction.
    4. The CNS is bathed in a fluid called cerebrospinal fluid.

Nerves that carry sensory input to the CNS are called afferent

Nerves that carry motor output away from the CNS are called efferent.

Two types of Efferent Nerves

  1. The Somatic system: efferent nerves leading to skeletal muscles.
  2. The Autonomic System: efferent nerves leading to the cardiac muscle, to smooth muscles and glands - "the viscera"

Two divisions of Autonomic System

  1. Parasymapthetic System: In general, it tends to slow down body activities and divert energy to "housekeeping" activities when the body isn't under stress.
  2. Sympathetic System: Under stress or in times of danger it prepares the body for "fight or flight"

Things to remember about the Autonomic Nervous System:

  1. Both systems send out signals at the same time. The effect on glands and muscles depends upon the sum of the opposing signal.
  2. Both systems can send out excitatory or inhibitory signals.
  3. There is also some level of "conscious" control over the Autonomic Nervous System. (biofeedback)

The brain

Hindbrain:

Medulla oblongata: controls reflex areas for vital functions such as heartbeat and respiration.

Cerebellum: coordination of motor activity, maintains posture, maintains spatial orientation.

Pons: (means bridge) area of connections of nerve tracts between the cerebrum and cerebellum and between the cerebrum and spinal cord.

Midbrain:

Tectum: integrates visual and auditory signals and send them on to higher centers. (Also called conduction center in humans)

Forebrain:

Thalamus: relays and coordinates sensory signals and sends to higher centers.

Hypothalamus: region concerned with neural-endocrine control of "visceral" activities such as temperature control, salt/water balance, reproduction, hunger.

Pituitary Gland: master endocrine gland. It is controlled by the hypothalamus. Its hormones control growth, reproduction and metabolism.

Pineal gland: located under the behind the thalamus. It secretes melatonin. The levels increase and decrease during a day/night cycle. It helps regulate the breeding season in some animals, its function in humans is unclear.

Cerebrum: higher brain centers: encoding and information processing.

Corpus Callosum: band of with matter that connects the two hemispheres of the brain.

Limbic system: interconnected areas of the forebrain that influence learning and emotional behavior.

Functional Regions:

Motor centers: originate instructions for motor responses

Sensory receiving centers

Association centers: integration of sensory input with memory to give meaning to sensory information.

Left Brain - Right Brian

Motor tracts cross in the medulla. Fibers from the right hemisphere cross and activate muscles on the left side of the body.

Usually one of the hemispheres is dominant.

The left hemisphere governs more strongly number skills, scientific skills, analyttical and logic skills, and governs right handedness.

The right hemisphere governs left handedness, and spatial awareness, imagination, insight, music awareness, and three dimensional form perception.

This dominance governs how we interpret the world, our skills, and the way we learn and interact with the world.

 
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