PSYC10006 Chap.10 Nervous System Divisions and Brain Anatomy
Nervous System Divisions and Brain Anatomy
The nervous system is one integrated network, and it is subdivided for description in two different ways: by structural landmark and by functional feature. Keeping track of which cut a term belongs to is most of what makes this material feel confusing, because the somatic and autonomic systems are both peripheral and yet clearly belong to a different scheme from central and peripheral.
The module then supplies the vocabulary every later location claim is written in. Directions are defined relative to the neural axis, which is why they hold across species and why they behave oddly in an upright human, where the axis bends.
After the terminology come the structures: the bridge between the hemispheres and what cutting it reveals, the subcortical structures and the function attached to each, and the four lobes with three topographic maps.
What this chapter covers
- 01
Two ways of cutting one network, and why the cuts do not line up
- 02
Central and peripheral, including the part of the eye that belongs to the first
- 03
Somatic against autonomic, and the two-way traffic the peripheral system carries
- 04
Sympathetic and parasympathetic as opposing influences on shared organs
- 05
The enteric system, and why independence of the brain earns it a name
- 06
Four surface direction terms, defined against the neural axis
- 07
Why dorsal means the top of the brain and the back of the spinal cord in one person
- 08
Four internal terms defined against the midline instead
- 09
The corpus callosum, homotopic and heterotopic connections, and callosotomy
- 10
Forebrain, midbrain and hindbrain, with the coverage the subject actually gives each
- 11
Subcortical structures and the function the subject attaches to each
- 12
Four lobes, the central sulcus rule, and retinotopic, tonotopic and somatotopic maps
Place a described structure in every scheme that applies
- 1Start with the structural division. It is inside the brain, so central nervous system, and within the cerebral hemispheres rather than the brainstem or cerebellum, so forebrain.
- 1Take the subdivision. Within the forebrain the telencephalon holds the cortex, the limbic system and the basal ganglia while the diencephalon holds thalamus and hypothalamus, and deep clusters within each hemisphere places it in the telencephalon.
- 1Use the tissue-type clue. Neuron cell bodies mean grey matter, and the subject makes exactly this point: the basal ganglia are grey matter although they are not cortex, which is why the description says so.
- 1Use the clinical clue to confirm rather than to identify. Tremor, rigidity and difficulty initiating movement are the features attached to basal ganglia dysfunction, consistent with the anatomy already established.
- 1Name it and distinguish the role. The basal ganglia control involuntary and highly automatised movement, which is a different job from primary motor cortex controlling voluntary muscle groups and from the cerebellum coordinating movement and balance.
Key terms
- Enteric nervous system
- The part of the peripheral nervous system governing the digestive tract, with its own reflexes and senses. It is the only part of the peripheral system that can act independently of the brain, and the other autonomic branches modulate rather than run it.
- Neural axis
- An imaginary line running through the spinal cord and forward into the brain, against which all anatomical directions are defined. It bends in an upright human, which is why one term has two everyday translations.
- Corpus callosum
- A large bundle of axons crossing between the hemispheres, carrying connections to the corresponding region on the other side and to different regions. Severing it stops seizure spread and also stops the hemispheres communicating.
- Basal ganglia
- Clusters of neuron cell bodies deep within each hemisphere, classified as grey matter although not part of the cortex. They control involuntary and highly automatised movement such as the coordinated limb movements of walking.
- Central sulcus
- The groove separating the frontal and parietal lobes. Primary motor cortex lies immediately in front of it and primary somatosensory cortex immediately behind, which makes it the most useful landmark in the module.
- Somatotopic map
- The orderly mapping of body surface onto a strip of cortex, with the face and hands allocated far more area than their physical size implies. It is one of three topographic maps the module names.
- Thalamus
- A diencephalic structure described as a major relay station for sensory input on its way to the cerebral cortex, divided into several nuclei.
Nervous System Divisions and Brain Anatomy FAQ
Is the eye part of the central or peripheral nervous system?
The retinal cells in the eyeball are stated to be part of the central nervous system, even though the eye sits outside the skull. The division is not really about being inside a bony case, which is how it is usually mis-remembered; the retina is central nervous tissue.
Why does dorsal mean two different things in one body?
Because direction terms are fixed to the neural axis rather than to upright posture, and the axis bends where a human head meets the spinal cord. Dorsal is therefore the upper surface of the brain and the posterior surface of the spinal cord. That is the rule working correctly, not an inconsistency.
Do sympathetic and parasympathetic take turns?
Not as a switch. Both innervate the same organs continuously and the balance between them shifts, which is why a threat response is described as sympathetic activity increasing and parasympathetic activity decreasing. Writing that one turns off converts a graded control system into a toggle.
How much detail does the subject give on the midbrain?
Almost none: it names a subdivision in a figure and develops no structures in its written pages, while covering forebrain and hindbrain in detail. Learn what is taught rather than filling the gap from elsewhere, and be aware that this is the thinnest area of an otherwise dense module.
What is the single most useful location fact here?
That motor cortex lies immediately anterior to the central sulcus and somatosensory cortex immediately posterior to it. Those two areas are adjacent, easily swapped, and support completely different functions, so a lesion item can be answered from that one landmark.
Assessment move
This is the module where recognition genuinely has to be automatic, because an item will give a description and four plausible labels rather than asking for a definition. Build the divisions as a tree you can redraw, and label each split as structural or functional so the two schemes stay apart.
Learn the eight direction terms in two groups of four, one defined against the neural axis and one against the midline, because trying to force all eight onto a single axis is what makes them feel arbitrary. Then drill localisation as a procedure: tissue type narrows the classification, depth narrows the division, and a clinical feature confirms rather than identifies.
Practise on descriptions you write yourself, and finish every answer by naming the neighbouring structures the description is not, which is where the last mark usually sits.
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