Overview
This lecture introduces the basics of the nervous system, covering its main functions, key structures, and divisions, with a focus on content essential for exams.
Functions of the Nervous System
- The nervous system enables the body to respond to external stimuli through a sequence: stimulus → receptor → integration → effector → response.
- Stimuli (e.g., light, pain, sound) are detected by sensory receptors (e.g., eyes, ears, skin).
- The central nervous system (CNS)—brain and spinal cord—integrates information and decides responses.
- Effectors (muscles or glands) carry out responses (e.g., moving, changing heart rate).
Structure of the Central Nervous System (CNS)
- The CNS consists of the brain and spinal cord.
- Meninges are protective layers around the brain and spinal cord: dura mater (outer), arachnoid (middle), and pia mater (inner).
- Cerebrospinal fluid provides lubrication and protection.
Regions of the Brain
- Cerebrum: largest part, responsible for voluntary movement, senses, memory, and intelligence.
- Cerebellum: coordinates movement, maintains muscle tone, posture, and balance.
- Corpus callosum: connects the left and right hemispheres for communication.
- Medulla oblongata: controls vital reflexes (breathing, heart rate), connects brain and spinal cord.
Structure and Function of the Spinal Cord
- Spinal cord has inner gray matter and outer white matter (color difference due to myelin).
- Composed of dorsal root (sensory input), ventral root (motor output), central canal (contains cerebrospinal fluid), and spinal nerves.
- Responsible for transmitting impulses and primitive reflexes (e.g., knee-jerk, pain withdrawal).
- Reflex arc: impulse enters via dorsal root, decision made in spinal cord, exits via ventral root.
Peripheral Nervous System (PNS)
- The PNS includes all nerves outside the CNS and is divided into the somatic and autonomic systems.
- Somatic nervous system: controls voluntary muscle movements and sensory information.
- Autonomic nervous system (ANS): regulates involuntary functions and divides into sympathetic and parasympathetic systems.
Autonomic Nervous System
- Sympathetic: "fight or flight"—increases heart rate, dilates pupils, slows digestion, provides quick responses.
- Parasympathetic: "rest and digest"—slows heart rate, constricts pupils, enhances digestion, provides slower, sustained responses.
Key Terms & Definitions
- Stimulus — external change detected by the nervous system.
- Receptor — sensory organ or cell detecting stimuli.
- Integrative function — decision-making process within the CNS.
- Effector — muscle or gland that executes CNS instructions.
- Meninges — protective membranes of brain and spinal cord (dura mater, arachnoid, pia mater).
- Cerebrum — part of brain for higher functions.
- Cerebellum — brain region for coordination and balance.
- Corpus callosum — tissue connecting brain hemispheres.
- Medulla oblongata — brainstem region controlling vital reflexes.
- Spinal cord — CNS extension transmitting signals and reflexes.
- Dorsal root — spinal cord entry for sensory nerves.
- Ventral root — spinal cord exit for motor nerves.
- Reflex arc — direct pathway for involuntary responses.
- Somatic nervous system — voluntary control of muscles.
- Autonomic nervous system — involuntary control; splits into sympathetic and parasympathetic divisions.
- Sympathetic division — activates emergency responses.
- Parasympathetic division — promotes relaxation and digestion.
Action Items / Next Steps
- Draw and label a diagram showing the divisions and structures of the nervous system.
- Review and create flashcards for all key terms.
- Prepare for deeper study of the reflex arc, the eye, and the ear in future lessons.