Neuroscience Basics Quiz

Welcome to PSL300 Section 4: CNS and Senses

• Instructor: Douglas Tweed
• Testable material: Facts and concepts from the slides only.
• Excluded material: Text printed in gray on the slides.
• Additional resources: Watch lectures for longer explanations, and read Silverthorn's Human Physiology.

Central Nervous System (CNS)

• The CNS includes the brain and spinal cord.
• The brain accounts for approximately 86 billion neurons.
• The spinal cord contains roughly 1 billion neurons.
• The enteric nervous system has an estimated 100–600 million neurons.
• Glial cells support and protect neurons.

Question of the Day

• Why are only 4% of brain neurons active at any given moment? (This is a question, not information)

Outline

• Overview of the CNS: Anatomy and energy supply.
• Spinal cord: Structure, nuclei, tracts, and reflexes.
• Brain: Divisions (including brain stem and cerebrum).

Overview of the CNS (cont.)

• The CNS is the brain and spinal cord. Diagrams show a human brain and spinal cord.

Peripheral Nervous System (PNS)

• Neurons outside the CNS comprise the PNS.
• The PNS includes the somatic (voluntary actions) and autonomic nervous systems.
• The enteric nervous system is part of the autonomic system and controls digestion It's independent.

CNS Composition

• The brain and spinal cord have a vast number of neurons.
• Most neurons reside within the CNS.
• The CNS and PNS also include glial cells, with abundance comparable to the neurons.

CNS Ventricles

• The CNS contains ventricles filled with cerebrospinal fluid (CSF).
• The ventricles include: Lateral ventricles, Third ventricle, Fourth ventricle and Central canal of spinal cord

Gray and White Matter

• Gray matter: nerve cell bodies, unmyelinated axons, and dendrites.
• White matter: myelinated axons in bundles (called tracts)
• Ganglia are clusters of neurons (in the peripheral nervous system)

CNS Energy Use

• The CNS uses a significant amount of energy.
• It has a high metabolic rate, using roughly 15% of cardiac output, and half the body's glucose, despite only being 2% of the body's mass.
• Compared to computers, the CNS consumes very little energy, around 40 watts.

Spinal Cord

• The spinal cord has 31 segments each with a pair of spinal nerves.
• Each spinal nerve has a dorsal root (incoming sensory signals) with a dorsal root ganglion, containing cell bodies of the sensory neurons.
• The ventral root (outgoing, motor signals) connects to skeletal muscles.

Spinal Reflexes

• A spinal reflex provides a quick response to a stimulus without the brain's direct involvement, as in the knee jerk reflex.
• Sensory fibers carry stretch signals relayed via interneurons towards the ventral horn which activates signals to leg muscles to counter the stretch.

Brain

• The brain has six major divisions: Cerebrum, Diencephalon, Midbrain, Pons, Medulla, and Cerebellum

Brain Stem

• The medulla, pons, and midbrain form the brain stem.
• The brain stem is central to autonomic functions like breathing, swallowing, and regulating blood pressure.
• Cranial nerves III–X and XII emerge from the brain stem.

Cranial Nerves

• Cranial nerves connect to the brain, not the spinal cord.
• There are 12 pairs.

Diencephalon

• The diencephalon comprises the thalamus, hypothalamus, pituitary, and pineal glands.
• The thalamus processes sensory information routed to the cerebral cortex.
• The hypothalamus regulates behavioral drives and homeostasis. The pituitary and pineal glands secrete hormones.

Cerebrum

• The cerebrum is divided into two hemispheres joined by the corpus callosum.
• Gray matter in the cerebrum includes the cortex, limbic system (aimed at emotion, motivation, and memory) and deep structures like basal ganglia related to movement control.

Cerebral Lateralization

• The two hemispheres exhibit specialization in function (left and right brain).

Lobes of the Cerebrum

• Each hemisphere has four lobes (frontal, parietal, temporal, and occipital.)

Limbic System

• The limbic system is a group of brain regions including the cingulate gyrus, amygdala, and hippocampus, related to emotion, memory, and motivation.

Reading in Silverthorn's Human Physiology

• Consult specific sections in Silverthorn's Human Physiology 8th edition. The chapters specified in pages 274, 289–290, and relevant sections 9.4 and 9.5 provide details on CNS. Similar guidance for 6th and 7th edition is also described.