Neural Control and Coordination

Overview

This lecture covers the chapter "Neural Control and Coordination," focusing on the human nervous system, neuron structure and function, classification of the nervous system, nerve impulse transmission, synapse types, and an introduction to the brain and its parts.

Introduction to Control and Coordination

• The human body uses two main systems for control and coordination: the nervous system (neural system) and the endocrine system.
• The nervous system uses neurons for fast, point-to-point communication; the endocrine system uses hormones (chemical messengers).
• Coordination between organs is vital for proper body functioning.

Neurons and Their Functions

• Neurons are the structural and functional units of the nervous system.
• Neurons detect, receive, and transmit nerve impulses throughout the body.
• Main parts of a neuron: cell body (with nucleus and cytoplasm), dendrites (branch-like projections), and axon (long fiber).

Classification of the Nervous System

• CNS (Central Nervous System): comprises the brain and spinal cord.
• PNS (Peripheral Nervous System): includes all nerves outside CNS.
• PNS nerve fibers:
  • Afferent (sensory) fibers carry impulses from organs/tissues to CNS.
  • Efferent (motor) fibers carry impulses from CNS to target organs/tissues.
• PNS is divided into:
  • Somatic nervous system (controls skeletal muscles, voluntary actions).
  • Autonomic nervous system (controls involuntary actions, smooth/cardiac muscles, glands).

Autonomic Nervous System Subdivisions

• Sympathetic nervous system: initiates "fight or flight" response (increases heart rate, sweating).
• Parasympathetic nervous system: promotes "rest and digest" functions (calms the body).

Structure and Types of Neurons

• Neuron structure: dendrites, cell body, axon, myelin sheath, Schwann cells, nodes of Ranvier, axon terminal, synaptic knob.
• Types of neurons (based on axon/dendrite number):
  • Multipolar (1 axon, multiple dendrites; found in cerebral cortex)
  • Bipolar (1 axon, 1 dendrite; found in retina)
  • Unipolar (1 process; embryonic stage)

Myelinated vs. Non-Myelinated Nerves

• Myelinated fibers: have Schwann cell covering (myelin sheath); found in brain and spinal cord.
• Non-myelinated fibers: lack myelin sheath; found in autonomic and somatic nervous systems.

Generation and Conduction of Nerve Impulse

• At rest, neuron membrane is polarized: inside negative (more K⁺), outside positive (more Na⁺).
• Sodium-potassium pump maintains this gradient (3 Na⁺ out, 2 K⁺ in).
• Stimulus causes depolarization (Na⁺ enters, inside becomes positive), followed by repolarization (return to resting state).
• Resting potential: polarized (no impulse); action potential: depolarized (impulse present).

Synapse and Transmission of Nerve Impulse

• Synapse: junction between two neurons, involves pre-synaptic and post-synaptic membranes.
• Electrical synapse: direct current flow, very fast.
• Chemical synapse: uses neurotransmitters (e.g., acetylcholine) released into synaptic cleft, binds to receptors on post-synaptic neuron to transmit impulse.

Human Brain

• Brain is the central command and control organ, protected by the skull and three meninges (dura mater, arachnoid, pia mater).
• Divided into:
  • Forebrain (cerebrum, thalamus, hypothalamus): controls intelligence, memory, sensory/motor functions, hunger, temperature.
  • Midbrain: relay center for auditory and visual reflexes.
  • Hindbrain (pons, medulla oblongata, cerebellum): controls balance, involuntary actions, respiration, cardiovascular functions.
• Cerebrum shows gray matter (cell bodies; cerebral cortex) and white matter (fiber tracts with myelin).

Key Terms & Definitions

• Neuron — Basic structural and functional unit of the nervous system.
• CNS (Central Nervous System) — Consists of brain and spinal cord.
• PNS (Peripheral Nervous System) — All nerves outside CNS.
• Afferent fibers — Sensory nerves carrying impulses to CNS.
• Efferent fibers — Motor nerves carrying impulses from CNS.
• Somatic Nervous System — Controls voluntary muscle movements.
• Autonomic Nervous System — Regulates involuntary functions.
• Myelin Sheath — Fatty layer covering some axons, speeding up impulse conduction.
• Synapse — Junction between two neurons.
• Neurotransmitter — Chemical messenger transmitting signals across synapse.
• Resting Potential — Polarized state of neuron at rest.
• Action Potential — Depolarized state during nerve impulse.
• Gray Matter — Areas rich in neuron cell bodies; cerebral cortex.
• White Matter — Myelinated nerve fibers; deeper brain areas.

Action Items / Next Steps

• Revise diagrams of neuron structure and types.
• Review differences between CNS, PNS, and autonomic subdivisions.
• Practice drawing and labeling the human brain and its parts.
• Prepare main questions: neuron structure, myelinated vs. non-myelinated nerves, nerve impulse conduction, brain parts/functions.