last updated:

Feb 27, 2021

[Brain Image]    

PSY 340 Brain and Behavior

Class 10:  Structure of the Vertebrate Nervous System


Structure of the Nervous System

[Comparison of Animal Brains] 

Compare above the different types of mammal brains? What do you see?

Human Nervous SystemA. Terminology to Describe the Nervous System

Central Nervous System (CNS)

  • Brain
  • Spinal Cord

Peripheral Nervous System (PNS)

Any nerve that does not belong to the CNS

Somatic Nervous System (SNS)

  • Voluntary muscle control
  • Sensory Information to the CNS

Autonomic Nervous System (ANS)

  • Controls involuntary muscles & glands (heart, intestines, etc.)

Directions in the Nervous System

Planes of view in NS  

Orientation 2Orientation 1

Rostral = toward the nose or front: from ROSTRUM - A bird's beak [& the prow of a ship]

  • A conquering Roman admiral would address his forces from the prow of a ship captured in a sea battle. A ship's prow reminded people of a bird's beak. Hence, a rostrum became a place someone spoke from.

Dorsal = towards the back: from DORSUM - An animal or person's back

Ventral = toward the stomach or below:  from VENTER - The belly or abdomen

    • A ventriloquist speaks from the belly.

Caudal = towards the back or the tail:  from CAUDA - The tail of a horse

    • The origin of the word, coward, since one sees the tail of the horse when a horse rider flees from battle


Superior is ABOVE and Inferior is BELOW
Proximal is NEAR while Distal is FAR
Ipsilateral occurs on the same side
Contralateral occurs on the other side
Medial is toward the middle
Lateral is toward the side

Terms about the Parts of the Nervous System

Lamina (laminae, pl.) = layer of cell bodies separated from other cell bodies by layer of axons or dendrites

= a set of cells aligned perpendicular to the surface of the cortex which share in the same function or properties
Tract = a set of axons within the CNS which go from point A to point B. Also called a projection
Nucleus (nuclei, pl.) = a cluster of neurons within the CNS
Ganglion (ganglia, pl.) = a cluster of neurons outside the CNS
Gyrus (gyri, pl.) = a bulge or protuberance on the surface of the cortex
Sulcus (sulci, pl.) = a fold or groove which separates one gyrus from another
Fissure = a deep and long sulcus

              cordB. The Spinal Cord

According to the Bell-Magendie law, sensory information (carried by the afferent fibers TO the brain) enters into the spinal cord by way of the dorsal roots (in the back) and motor information to the muscles and glands (carried by the efferent fibers FROM the brain) exits from the spinal cord by way of the ventral roots (in the front).

Clusters of the bodies (soma) of sensory neurons are gathered together in an area outside the spinal cord itself. The area is called a dorsal root ganglion (ganglia, plural).

The central area of the spinal cord is shaped like an "H" and consists mostly of cell bodies (or, "gray matter"). The surrounding area consists mostly of insulated axons (or, "white matter") of the spinal cord.

Damage to the spinal cord usually prevents any information from being sent to or from the brain to areas of the body controlled by the spinal cord from the level of the damage downward.

C. Autonomic Nervous System (ANS)

"Nomos" in Greek is the word for "law" or "regulation" while "autos" is the word for "self." Hence, the automomic nervous system is the set of neurons which functions almost like a law unto itself. It sends commands to and receives information from internal organs, particularly the heart, intestines, digestive system, lungs, and other organs and glands.

1. Sympathetic Nervous System

The sympathetic branch of the ANS prepares the body for action: fight or flight. These include the heart (pumps more), lungs (breathes more), liver (releases nutrients into blood stream), stomach (stops digestion), muscles (constricts blood vessels), etc.

Cold medicines2. Parasympathetic Nervous System

The parasympathetic branch of the ANS helps to restore the body, build up energy & supplies needed in the future, and relax. So, its actions include increasing digestion in the stomach and intestines, slowing down the heart, and increasing the flow of secretions such as mucus or salivation.

Drugs & the ANS

The two parts of the ANS tend to use different neurotransmitters, e.g., acetylcholine in the parasympathetic NS and norepinepherine in the sympathetic NS.

Many "over-the-counter" (OTC) cold and flu medications target the ANS by blocking the parasympathetic and/or stimulating the sympathetic nervous system. Sinus flow is a parasympathetic activity. The side effects of OTC remedies often relate to their pro-sympathetic system activities, i.e., increasing heart rate while drying out the mouth.

D. The Brain: Divisions

  • HindbrainWhole
  • Midbrain
  • Forebrain
  • Thalamus
  • Hypothalamus & Pituitary Gland
  • Basal Ganglia
  • Basal Forebrain
  • Hippocampus


HindbrainMedulla (medulla oblongata)

  • Vital functions: breathing, heart rate, vomiting, coughing, sneezing.
  • Connections through the cranial nerves (sensation & motor nerves for head) and parasympathetic nervous system.

Pons (the "bridge")

  • Many nerves cross over from one side of the body to the other
  • Contains (within the medulla & pons) the reticular formation (including the raphe system)
    • Ascending reticular formation is also known as the ascending reticular activating system
      • sends output throughout the cerebral cortex and controls our overall level of arousal and attention. It has a role in regulating many basic automatic functions (e.g., sleeping & eating)
      • raphe syste axons project widely into the forebrain. Deeply involved in our sleep-wake cycle and our readiness to respond to stimuli. These neurons form the major system using serotonin as a a neurotransmitter. Pronounced "ray-fee"
You will NOT be responsible to learn the cranial nerves.

Cerebellum (Animated)Cerebellum ("little cerebrum" or "little brain") [Much of this is NOT in book]

  • Complexly connected with the cerebral cortex. We are only beginning to understand its full range of functions.
  • Known functions with very good evidence:
    • Control of movement & balance
    • Time-related behaviors such as shifting attention for alternating sensory data (e.g., judging rhythm; playing the drums)
    • Forms of simple learning & conditioning (associating stimuli with responses)
  • NEW: role in cognition, language, & affect (emotion)
  • The functions above have been generally assigned to two different regions of the cerebellum [see diagram on left; Marien et al. (2014)]
    • Anterior: involved in motor and movement functions
    • Posterior: involved in cognitive & affective (emotional) functions
  • The cerebellum probably contributes to the rapid building of models of the body interacting with the world around it (= predictive brain & embodied cognition). We can therefore respond unconsciously and automatically to shifting conditions (Koziol et al. 2011)
  • Most densely packed area of brain with neurons: ca. 70 billion
Three Strange Cases: Born with a Cerebellum (Agenesis of the Cerebellum)

1. Chase Britton - Boy Without a Cerebellum (and Pons)

                Britton      Chase Britton Missing Cerebellum  Chase with
                Older Brother, Dec. 2019
  • Update on 9/17/2013: Chase is now 6 years old, has begun 1st grade (he was in kindergarten 2012-13), plays with his older brother Alex on his iPad, can count to 30, reads short words, and has a service lab/great dane dog named "Missa". 
  • Update on 8/14/2014: Chase attended and met with Lady Antebellum at the Erie County Fair this year.
  • Updates in Dec. 2019 & May 2020. Chase is now 12 or 13 years old, uses both a wheelchair and a special walker. His father, David E. Britton, unfortunately died of stomach cancer at age 50 in May, 2020.

2. Chinese Woman, 24, Found to Lack Cerebellum (2014)
  • In what seems to be only the 9th documented case in medical history in 2014, a 24-year-old woman in China went to the hospital complaining of a headache and was found to have been born without a cerebellum (Feng Yu et al. 2014
No Cerebellum

cerebellar agenesis3. Indian Man, 45, Found to Lack Cerebellum (2018)
  • A 45-year-old man in India who had a head injury was found to lack any cerebellum in a CT scan after his accident.
  • Neurologists reported that his "birth was by a normal vaginal delivery. There  was no history of any difficulty in walking or in carrying out routine daily activities. The clinical and neurological  examination revealed no motor impairment. No evidence of  ataxia [loss of muscle control & balance], dysarthria [inability to speak clearly because of muscle weakness], nystagmus [repetitive & rapid eye movements to the side], or intention tremor [shaking of the arm/hands in reaching toward an object] was noted. The Romberg’s test [inability to maintain balance because of loss of proprioception] was negative and deep tendon reflexes were normal" (Omair et al., 2018; emphasis & descriptors within brackets [] added")


MidbrainTectum ("roof")

Tegmentum ("floor covering" or "rug")

Substantia Nigra ("dark substance")


ForebrainOuter surface = Cortex (Latin = Bark of tree) [in next class]

Limbic System (linked set of structures beneath the cortex including olfactory bulb, hypothalamus, hippocampus, amygdala, & cingulate gyrus)

Thalamus ("antechamber")

Hypothalamus ("beneath the thalamus")

Pituitary Gland

Basal Ganglia

  • subcortical structures lateral to the thalamus
  • caudate nucleus, putamen, globus pallidus
  • multiple connections with frontal lobe cortex
  • planning sequences of behaviors (movements), memory, emotions
  • Basal Forebrain

    Hippocampus ("sea horse")

    Lobes of the Cerebral Cortex - Covered in next class

    Ventricles {W}

    Ventricles (1)  Ventricles (2)

    The ventricles are spaces within the brain itself that are filled with a clear fluid (cerebrospinal fluid [CSF]). CSF is very much like blood plasma.

    Hydrocephalus: Blockage of the flow of CSF in brain of infant causing swelling of head and, usually, mental retardation.

    Animated cerebellum image above: By Polygon data were generated by Database Center for Life Science(DBCLS)[2]. (Polygon data are from BodyParts3D[1]) [CC BY-SA 2.1 jp (http://creativecommons.org/licenses/by-sa/2.1/jp/deed.en)], via Wikimedia Commons


    Koziol, L. F., Budding, D. E., & Chidekel, D. (2011). From movement to thought: Executive function, embodied cognition, and the cerebellum. Cerebellum. Published online Nov. 9, 2011. DOI 10.1007/s12311-011-0321-y

    Marien, P., Ackermann, H., Adamaszek, M., et al. (2014) Consensus paper: Language and cerebellum: An ongoing enigma. Cerebellum, 13, 386-410 doi:10.1007/s12311-013-0540-5

    Omair … (2018) Primary cerebellar agenesis in a normal man. Neurology India, 66, 871-873.  doi: 10.4103/0028‑3886.232287

    Yu, F., Jiang, Q., Sun, X., & Zhang, R. (2014). A new case of complete primary cerebellar agenesis - Clinical and imaging findings in a living patient. Brain, 138(6). doi: 10.1093/brain/awu239

    Visible Human images from <http://www.nlm.nih.gov/research/visible/vhpconf98/>

    This page was first posted February 6, 2005