Exam Review: Nervous System and Special Senses (Ch. 11-13)

Ch. 11: The Nervous System

Neuronal Physiology

The nervous system relies on the rapid transmission of electrical signals through neurons. Understanding the properties of neurons and their signaling mechanisms is essential for grasping nervous system function.

• Absolute Refractory Period: The period during which a neuron cannot initiate another action potential, regardless of stimulus strength. This ensures one-way transmission of nerve impulses.

• Anatomy of a Neuron: Neurons consist of a cell body (soma), dendrites (receive signals), and an axon (transmits signals).

• Action Potential Creation: Involves the movement of ions (Na+, K+) across the neuronal membrane, leading to depolarization and repolarization.

• Neuroglial Cells: Support cells in the nervous system, such as astrocytes, oligodendrocytes, microglia, and Schwann cells, each with distinct functions.

• Neurotransmitters: Chemical messengers released at synapses; examples include acetylcholine, dopamine, and serotonin.

• Intracellular vs. Extracellular Fluid: The intracellular fluid is inside the neuron, rich in K+; extracellular fluid is outside, rich in Na+.

• Graded Potential vs. Action Potential: Graded potentials are small, local changes in membrane potential; action potentials are large, all-or-none electrical impulses.

• General Function and Anatomy of the ANS: The autonomic nervous system regulates involuntary functions (e.g., heart rate, digestion) and consists of sympathetic and parasympathetic divisions.

• EPSP and IPSP: Excitatory postsynaptic potentials (EPSP) depolarize the membrane, increasing likelihood of action potential; inhibitory postsynaptic potentials (IPSP) hyperpolarize, decreasing likelihood.

• Ganglia vs. Nuclei: Ganglia are clusters of neuron cell bodies in the peripheral nervous system; nuclei are clusters in the central nervous system.

Ch. 12: Central and Peripheral Nervous System

Brain and Spinal Cord Anatomy

The central nervous system (CNS) includes the brain and spinal cord, each with specialized regions and functions.

• White vs. Gray Matter: White matter consists of myelinated axons; gray matter contains neuron cell bodies and dendrites.

• CNS Anatomy: Includes the cerebrum, cerebellum, brainstem, and spinal cord.

• Primary Auditory Cortex: Located in the temporal lobe; processes auditory information.

• Limbic System: Involved in emotion, memory, and motivation; includes structures such as the hippocampus and amygdala.

• Thalamus: Acts as a relay station for sensory information.

• Medulla and Pons: Control vital functions such as breathing and heart rate.

• Basal Nuclei: Involved in movement regulation.

• Location of Major Brain Structures: Know the anatomical positions of the thalamus, medulla, pons, and basal nuclei.

• Function of the Limbic System: Emotional processing and memory formation.

• Function of the Thalamus: Sensory relay to the cerebral cortex.

• Function of the Medulla and Pons: Autonomic control of respiration and cardiovascular function.

• Basal Nuclei: Modulate voluntary motor activity.

Ch. 13: Peripheral Nervous System and Special Senses

Peripheral Nerves and Receptors

The peripheral nervous system (PNS) connects the CNS to limbs and organs. It includes various types of nerves and receptors that detect and respond to stimuli.

• Types of Receptors: Mechanoreceptors (touch, pressure), nociceptors (pain), chemoreceptors (chemical stimuli).

• Major Nerves Involved in Motor Control:

  • Musculocutaneous

  • Median

  • Radial

  • Ulnar

  • Axillary

  • Femoral

  • Tibial (part of the Sciatic)

  • Common Fibular (part of the Sciatic)

• Cranial Nerves: Twelve pairs, each with specific sensory and/or motor functions. Some have parasympathetic functions (e.g., vagus nerve).

• Brachial Plexus: Network of nerves supplying the upper limb; includes subdivisions and major nerves.

• Afferent vs. Efferent Nerves: Afferent nerves carry sensory information to the CNS; efferent nerves carry motor commands from the CNS.

• Lumbar Plexus: Supplies nerves to the lower limb.

• "Funny Bone": Refers to the ulnar nerve at the elbow; impact causes tingling sensation.

• Bell's Palsy: Condition involving facial nerve dysfunction, leading to facial muscle weakness.

Table: Major Nerves of the Brachial Plexus

Nerve	Function	Region Supplied
Musculocutaneous	Motor to anterior arm muscles; sensory from lateral forearm	Arm, forearm
Median	Motor to forearm flexors; sensory from lateral palm	Forearm, hand
Radial	Motor to posterior arm and forearm; sensory from posterior limb	Arm, forearm, hand
Ulnar	Motor to hand muscles; sensory from medial hand	Hand
Axillary	Motor to deltoid and teres minor; sensory from shoulder	Shoulder

Additional info:

• Action potentials are governed by the equation: $V = IR$ (Ohm's Law), where $V$ is voltage, $I$ is current, and $R$ is resistance.

• Neurotransmitter release at synapses is a key mechanism for neuronal communication.

• Bell's Palsy is often temporary and may resolve without treatment.