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Last updated: October 1, 2026

1. Organization of the Nervous System

2. The Brain and Behavior

• Imaging the Brain
• Hindbrain
• Midbrain
• Forebrain
  • Cerebrum
    • Lobes

3. Right Brain/Left Brain: Cerebral Specialization

• Split Brain Research
• Hemispheric Specialization

 

  1. Organization of the Nervous System

What is "a nerve"? Nerve = "A nerve is a cable-like bundle of fibers (axons) in the peripheral nervous system that transmits electro-chemical impulses between the brain, spinal cord, and other body parts.'

A. The Peripheral Nervous System (PNS) = All the neural elements (nerves) which do NOT belong to the brain or spinal cord.

The Somatic Nervous System = Nerves which connect to the voluntary skeletal muscles and to sensory receptors

• Afferent fibers carry information TOWARD the CNS
• Efferent fibers carry information AWAY from the CNS

The Autonomic Nervous System  = Nerves which connect to the heart, blood vessels, smooth muscles, and glands.

• Walter Cannon (1871-1945): "Fight or Flight" response

1. Sympathetic System = This system mobilizes the body to deal with challenges

2. Parasympathetic System = This system conserves & restores body resources as it "tunes down" the body

B. The Central Nervous System (CNS)

The Spinal Cord

The Brain

Dr. Joseph P. Hornak (RIT). The Basics of MRI (2003).

• Spinal cord, Brain Stem, & Cerebrum
• Saggital Lumbar Spin

2. The Brain and Behavior
A. Selected Techniques to Measure & Image the Central Nervous System	Animal Research: Lesioning (Ablation) and Electrical Stimulation Lesion = injuring tissue, e.g., cutting, burning Ablation = cutting away tissue Human Research & Health Care
	CT (Computerized Tomography): 3-dimensional low energy x-ray scans of brain processed by computer
	MRI (Magnetic Resonance Imaging). Whole Brain Atlas (Harvard Medical School) Examples of MRI
National Institute on Drug Abuse	PET (Positron Emission Tomography)
	TMS (Transcranial Magnetic Stimulation)
	fMRI (Functional Magnetic Resonance Imaging) In the image to the left, two major areas of the brain are active when seeing something = primary visual cortex in the occipital lobe and the lateral geniculate nucleus of the thalamus

Brain 3 pounds about 86 billion (+/- 8 billion) neurons & about 84 billion glial cells
B. Hindbrain
	Cerebellum	Large, folded structure behind the brainstem. Coordination of movement & balance Smooth motion Fine (intricate) motor skills Conditioned learning NEW: role in cognition (thinking), language, & affect (emotion)
	brainstem = medulla & pons (below)
	Medulla	Regulation of fundamental bodily activities such as breathing and blood circulation. Major damage leads to death. Muscle tone Reticular Formation: runs in middle of medulla, pons, & into midbrain. Modulates breathing, pain, & centrally involved in sleep, awakening & arousal.
	Pons ("The Bridge")	Pathway between the Cerebellum and the Cerebrum (see below) Connects the Cerebrum above with the brain stem & the spinal cord below.
C. Midbrain	Segment of top of the brain stem lying between the pons and the forebrain. Sensitive to orientation of individual in space; works with voluntary muscle movement (e.g., moving head to respond to someone's call or a strange sound; tracking an object like a baseball to catch it)    Dopamine-releasing neurons project from the midbrain into the forebrain. The gradual death of these neurons is associated with the development of Parkinson's Disease.
D. Forebrain
i. Thalamus	Relay station for all incoming sensory information (vision, hearing, touch, etc.) except for smell. Information is passed on to cerebrum. Beginning of the integration of this information.
ii. Hypothalamus	Regulation of basic bodily needs & functions; maintains body's biological homeostasis (balance), e.g, temperature, heart rate, blood pressure Control of the autonomic nervous system: fighting vs. relaxation. Basic biological drives: feeding, thirst, sex Sends various signals to the pituitary gland to release hormones
iii. Limbic System	A loose network of structures which, together, appear to be involved in the regulation and expression of emotion and pleasure.
	Hippocampus Human memory processes. Long-term storage (consolidation) of memories. We learned this from Patient H.M. Amygala Evaluation of the environment vis-a-vis emotion Particularly involved in fear and anger responses Medial Forebrain Bundle (part of limbic system & passing through the hypothalamus) Olds & Milner (1954) discovery of self-stimulation centers in rats' brains = "pleasure centers" DA-rich neurons which, when stimulated, result in pleasure/reward
iv. Cerebrum	The largest and most complex part of the human brain.
	Cerebral Cortex = The outer layer of the cerebrum. Deeply folded and compacted Cerebral Hemispheres. Deep below the outer cortex, the two hemispheres are connected by a thick bundle of fibers called the corpus callosum.  Your instructor's brain via MRI
Lobes of the Brain	Frontal Lobe	Primary motor cortex: initiation of movement (pink color in diagram) Prefrontal cortex: area in front of motor cortex (deep red in diagram) Executive functions: Goal planning, making decisions, considering context
	Parietal Lobe	Primary processing area for sense of touch and the other somatosensory senses (temperature, pressure, proprioception, etc; darker blue in diagram.) Processes the spatial aspects of behavior (e.g., where the body is located in space; lighter blue in diagram)
	Temporal Lobe	Primary auditory processing area Comprehension of spoken language  Processes visual data to recognize faces, objects, and what they are called
	Occipital Lobe	Primary visual processing area

3. Right Brain/Left Brain: Hemispheric Specialization
Broca                      Wernicke
19th Century: Discovery of Hemispheric Dominance Paul Broca (1861) The area is now known as "Broca's Area" and patients with damage (lesions) to this area have difficulty actually pronouncing spoken language. This difficulty is also known as "Broca's aphasia" or "expressive aphasia". Carl Wernicke (1874) "Wernicke's aphasia" or "receptive aphasia" and the region of the cortex is usually called "Wernicke's area" Conclusion: By the 20th century, neurologists and psychophysiologists described the left hemisphere of the brain as dominant for language.
Split-Brain Research   Roger Sperry Nobel e-Museum	Effects of "split brain" operations These results support the notions of Language processing in the left hemisphere Continued visual processing in the right hemisphere
Hemispheric Specialization
Left Hemisphere	Verbal processing (speech, language, reading) Some evidence for analytic processing, that is, items in discrete parts
Right Hemisphere	Nonverbal processing -- spatial data Musical perception Visual object recognition Some evidence for synthetic processing, that is, recognizing the overall configuration or organization of perceptual data
Caution	In the normal human brain, both hemispheres are in direct and intensive contact with each other. The evidence that individuals use one hemisphere more than another ("I'm more of a right-hemisphere kind of person") is extremely weak or non-existent!!!

Reference

Pan, D., Patel, A. U., et al. (2025) Surgeons, physiatrists and neurologists speaking “EDX and nerve surgery”: A paradigm shift for nerve injured patients. JPRAS Open, 47, 3-20. https://dx.doi.org/10.1016/j.jpra.2025.11.004