Control and Coordination

• Control and coordination are vital for a well-harmonized body
• The chapter aims to answer questions about how the body functions in a coordinated way

Objectives

• Explain the roles of the nervous and hormonal systems in coordinating bodily activities
• Recognize and list the major components of the nervous system and their roles
• Explain how nerve cells (neurons) transmit nerve impulses
• Identify where the spinal cord is located and its function in reflex actions
• Analyze the role of endocrine glands in regulating growth and behavior
• Understand the importance of reflexes, voluntary/involuntary actions, and hormones in body function

Nervous and Endocrine Systems

• The nervous and endocrine systems ensure controlled and coordinated body functions
• The nervous system includes the brain, spinal cord, sense organs, and nerves
• The endocrine system uses hormones, which are chemicals produced by specialized glands and secreted into the blood
• The nervous and endocrine systems work together to integrate and coordinate organ systems

Daily Life Coordination

• Hunger is triggered when the body requires energy
• Eyes perceive food, then the brain initiates coordinated activities
• The nervous system guides hand and finger muscles to bring food to the mouth
• After sufficient food intake the brain signals fullness, ceasing eating
• Food enters the alimentary canal, where digestive juices are secreted under the influence of endocrine glands
• Digestion, followed by food absorption into the bloodstream, fulfills energy needs
• Both the nervous and endocrine systems control physical actions, thinking, and emotions
• These systems play a role in maintaining health and well-being

Reflex Actions

• Reflex actions are immediate responses to urgent or dangerous situations
• An example is removing a hand from a hot object
• The nervous and endocrine systems enable bodily functions

The Nervous System

• The nervous system relies on detecting and responding to stimuli from the internal or external environment
• A stimulus is an agent or environmental change that triggers a bodily response
• Stimuli types: physical (touch, pressure), auditory, chemical, radiant (light, heat/cold), or electrical

Neuron (Nerve Cell)

• Neurons communicate and transmit information throughout the body
• A neuron consists of dendrites, a cell body, and an axon
• Dendrites: Branched projections receiving impulses that trigger a chemical reaction, creating an electrical impulse passed to the cell body
• Cell Body: Contains the nucleus and cytoplasm, transmitting the impulse to the axon
• Axon: A long branch carrying impulses, often insulated by a fatty neurilemma sheath
• Node of Ranvier: Intervals lacking neurilemma, generating electrical activity and nerve impulse transmission
• Axon ends have bulbs storing neurotransmitters
• Synapse: The junction between two neurons
• Synaptic Cleft: The space separating two neurons
• Neurotransmitters released into the synaptic cleft facilitate impulse transfer
• Neurotransmitters cross the cleft and trigger an electrical impulse in the next neuron
• Neurons deliver impulses to muscle cells or glands
• Three neuron types exist

Sensory Neurons

• Sensory neurons carry impulses from receptors (sense organs) to the central nervous system (brain or spinal cord)

Motor Neurons

• Motor neurons carry impulses from the central nervous system to effectors (muscles or glands)

Association Neurons

• Association neurons are located in the brain and spinal cord, interconnecting sensory and motor neurons

Nerves

• Nerves are thread-like structures emanating from the brain and spinal cord
• A nerve consists of bundled nerve fibers (axons) in a tubular sheath
• Sensory Nerves: Contain sensory fibers, transmitting impulses from receptors to the brain or spinal cord. Example: Optic nerve
• Motor Nerves: Contain motor fibers, carrying impulses from the brain or spinal cord to effector organs. Example: Nerves to the eye muscles
• Mixed Nerves: Contain both sensory and motor fibers for mixed functions. Example: Spinal nerve

Sense Organs

• Receptor organs, like the nose and eyes, receive stimuli
• Stimuli reach the spinal cord and brain through sensory nerves
• The brain integrates the information
• Motor nerves send messages to the required muscles or glands to create a response

Central Nervous System (CNS)

• The central nervous system is the information processor
• CNS consists of the brain and spinal cord

Brain Protection

• The brain is protected by the bony cranium and three meninges (membranous coverings)
• Dura mater: The tough, fibrous outermost membrane
• Arachnoid: The thin, web-like middle layer
• Pia mater: The highly vascular innermost membrane
• Cerebrospinal fluid cushions the brain

Brain Areas

• Cerebrum: The largest brain portion, divided into two cerebral hemispheres with convoluted surfaces.
• Cortex: The outer layer with neuron cell bodies (gray matter)
• White matter: The inner portion contains axons
• The cerebrum handles thinking, reasoning, invention, planning, and memory functioning as the seat of intelligence
• Cerebellum: Located below the cerebrum, maintains balance and coordinates muscle activity.
• Medulla oblongata: The lowest brain portion controls visceral activities (e.g., heartbeat and breathing), injury can be fatal.

Spinal Cord

• The spinal cord extends from the medulla to the backbone and houses the vertebral column
• Gray matter lies on the inner side, white matter on the outer side
• Cerebrospinal fluid fills the central canal, providing a cushion and exchange medium

Spinal Cord Functions

• Controls reflexes below the neck
• Sends sensory impulses from the skin and muscles to the brain,
• Conducts motor responses from the brain to the trunk and limbs

Reflex Action Explained

• Reflex actions are immediate responses to dangerous situations
• Reflexes are spontaneous actions not requiring brain processing

Reflex Action - Examples

• Tearing up when particles enter the eye
• Instantaneously withdrawing a hand from a hot pan
• Shivering when cold
• Sweating when hot

Reflex Arc Representation

• Stimulus goes to receptor
• Receptor activated sensory neuron
• Sensory neuron to CNS
• CNS activates motor neuron
• Motor neuron evokes response from muscle/gland

Types of Reflexes

Natural Reflexes

• Natural reflexes do not need previous experience
• Examples are breathing, heartbeat, swallowing, coughing, and blinking

Conditioned Reflexes

• Conditioned reflexes develop through experience or learning
• An example is salivation at the smell of favorite food which occurs because brain associates aroma with the food
• This response is acquired

Peripheral Nervous System

• The peripheral nervous system connects the central nervous system to organs, muscles, and glands
• The peripheral nervous system includes sensory and motor nerves
• Somatic Nervous System: Conveys information to skeletal muscles and regulates voluntary actions
• Autonomic Nervous System: Controls involuntary actions of internal organs, smooth muscles, and glands

Somatic Nervous System

• Cranial Nerves: 12 pairs emerge from the brain. Examples: optic nerve and auditory nerve
• Spinal Nerves: 31 pairs emerge from the spinal cord.

Autonomic Nervous System

• The autonomic nervous system consists of a pair of nerve and ganglia chains along the backbone
• The ANS controls involuntary actions in internal organs
• Sympathetic Nervous System (SNS): More active during stress, preparing the body for 'fight-or-flight'
• Parasympathetic Nervous System: Controls actions not needing immediate response producing saliva

Endocrine System

• The endocrine system regulates changes and development from infancy to old age with special glands
• Endocrine glands produce chemical secretions called hormones
• Hormones aid in control, coordination, and the regulation of organ and tissue functions, hormones are regulated by feedback mechanisms
• Pituitary Gland: Located at the brain base, it regulates growth from puberty, secreting Gonad Stimulating Hormone which regulates the ovaries and testes
• Oestrogen and testosterone initiate secondary sexual character development
• Thyroid Gland: Dictates metabolism speed, crucial for life, growth, and development
• Pancreas: Insulin and glucagon regulate glucose metabolism