Overview
This lecture introduces the human nervous system, its main components and functions, the structure and protection of the brain and spinal cord, and the different types of neurons.
Introduction to the Nervous System
- The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS).
- The CNS consists of the brain and spinal cord, responsible for processing and decision-making.
- The PNS includes all nerves outside the CNS, responsible for carrying out CNS decisions.
- The PNS is further divided into the somatic (voluntary control) and autonomic (automatic functions) nervous systems.
- The autonomic system divides into sympathetic (fight or flight response) and parasympathetic (rest and digest).
Brain Structure and Function
- The cerebrum is responsible for thinking, memory, senses, and consciousness.
- The cerebellum controls balance, muscle tone, and coordinates voluntary movements.
- The medulla oblongata regulates heartbeat, breathing, and some reflexes.
- The corpus callosum connects the left and right brain hemispheres for communication.
- Ventricles are fluid-filled spaces that cushion and protect the brain with cerebrospinal fluid.
Protection of the Brain and Spinal Cord
- The brain and spinal cord are protected by bone (skull and vertebrae) and three membranes called meninges: dura mater (outer, tough), arachnoid (middle, blood vessels), and pia mater (inner, soft).
- Cerebrospinal fluid in ventricles and the central canal acts as a cushion.
Structure of the Spinal Cord
- The spinal cord has white matter (outer, myelinated, sensory and motor neurons) and gray matter (inner, non-myelinated, interneurons).
- Central canal in the spinal cord contains cerebrospinal fluid.
- Spinal nerves branch out from the spinal cord to the body.
Types and Structure of Neurons
- Three main types: sensory neurons (carry impulses from sense organs), interneurons (integration in CNS), motor neurons (carry impulses to muscles/glands).
- Sensory neuron: cell body in the middle of axon; found in receptors.
- Interneuron: cell body off to the side; located in brain and spinal cord.
- Motor neuron: cell body with dendrites around it; found in effectors (muscles/glands).
- A neuron’s main parts: dendrites (receive impulses), cell body (contains nucleus), axon (transmits impulses), myelin sheath (insulates and speeds impulses), synaptic knobs (transmit impulses to next neuron).
- Impulses travel from dendrites to axon to synaptic knobs, then to the next neuron.
Key Terms & Definitions
- Central Nervous System (CNS) — the brain and spinal cord, processing and integrating information.
- Peripheral Nervous System (PNS) — all nerves outside the CNS, carrying messages between CNS and body.
- Somatic Nervous System — controls voluntary movements.
- Autonomic Nervous System — controls involuntary functions.
- Sympathetic Nervous System — prepares body for action (fight/flight).
- Parasympathetic Nervous System — controls rest and maintenance functions (rest/digest).
- Meninges — three protective membranes around the brain and spinal cord.
- Dendrite — neuron extension that receives impulses.
- Axon — neuron extension that carries impulses away from cell body.
- Myelin Sheath — fatty layer insulating axons.
- Synaptic Knob — terminal part of neuron transmitting impulses to next cell.
Action Items / Next Steps
- Review the structure and function of CNS and PNS.
- Memorize the parts and functions of a neuron.
- Label diagrams of brain, spinal cord, and neurons for practice.
- Focus your studying on exam guideline requirements only.