Neurobiology Module 4

The Peripheral Nervous System (PNS) is comprised of the:

1. Somatic Nervous System

  • Convey sensory information to the CNS.

  • Transmit messages for motor movement from the CNS to the body.

2. Autonomic Nervous System

The autonomic nervous system sends and receives messages to regulate the automatic behaviors of the body (heart rate, blood pressure, respiration, digestion, etc).

Divided into two subsystems:

  • The Sympathetic Nervous System. The sympathetic nervous system is a network of nerves that prepares the organs for rigorous activity:

    • increases heart rate, blood pressure, respiration, etc. (“fight or flight” response) comprised of ganglia on the left and right of the spinal cord

    • mainly uses norepinephrine as a neurotransmitter at the postganglionic synapses

  • The Parasympathetic Nervous System. The parasympathetic nervous system facilitates vegetative, nonemergency responses.

    • decreases functions increased by the sympathetic nervous system.

    • comprised of long preganglion axons extending from the spinal cord and short postganglionic fibers that attach to the organs themselves.

    • dominant during our relaxed states.

The process of relating skull anatomy to behavior is known as phrenology.

  • One of the first ways used to study the brain.

  • Yielded few, if any accurate results

Computerized Axial Tomography (CAT scan) involves the injection of a dye into the blood and a passage of x-rays through the head.

  • Scanner is rotated slowly until a measurement has been taken at each angle and a computer constructs the image

Magnetic Resonance Imaging (MRI) involves the application of a powerful magnetic field to image the brain.

Recording brain activity involves using a variety of noninvasive methods including:

  • Electroencephalograph (EEG) - records electrical activity produced by various brain regions.

  • Positron-emission tomography (PET) - records emission of radioactivity from injected radioactive chemicals to produce a high- resolution image

  1. Research has not supported that a larger brain is correlated with higher intelligence.

  2. Brain-to-body ratio research has some limited validity.

  3. Moderate correlation exists between IQ and brain size  Amount of grey and white matter may also play a role.

  4. IQ is correlated with amount of grey matter

  5. Greater resemblance among twins for both brain size and IQ

  6. For monozygotic twins, the size of one twin’s brain correlates significantly with the other twin’s IQ.

  7. Therefore, whatever genes that control brain also relate to IQ

  8. Men have larger brains than women but IQ is the same.

  9. Various differences in specific brain structures exist between men and women

  10. Left/right cortex, hippocampus and amygdala

  11. Explanations in differences in cognitive abilities can perhaps be better explained by interest than abilities