Response and Interaction Mechanisms

• These mechanisms facilitate an individual's response and interaction with their environment.

Receiving Mechanism (Receptor)

• Sensory organs (eyes, ears, nose, mouth, and skin) receive stimuli from the environment.
• Receptors detect stimuli like light, sound, chemicals, taste, and touch.
• Stimuli are converted into electrical signals for brain interpretation.

Connecting Mechanism (Connector)

• The nervous system, including the brain, spinal cord, and nerves, transmits signals.
• Neurons relay information to different parts of the brain for processing.
• Ensures accurate and efficient signal transmission to appropriate brain areas.

Reacting Mechanism (Reactors)

• Muscles and hormones of the glandular system react to brain-processed information.
• Reactions can be physical actions (e.g., moving from danger) or hormonal responses via the endocrine system.
• Reactors coordinate bodily responses based on receptor input and brain interpretation.

Receiving Mechanism/Receptor Details

Eyes

• Stimulus: Light rays
• Receptor: Retina
  • Rods: Function in low light, not sensitive to colors, connects to optic nerve.
  • Cones: Function in bright light, sensitive to colors, connects to optic nerve.
• Neural Processing: Occipital Lobe

Ears

• Stimulus: Sound waves
• Receptor: Cochlea
  • Organ of Corti: Hair cells act as specific hearing receptors (to auditory nerve).
  • Vestibular Portion/Semicircular Canals: Sense balance/equilibrium (to auditory nerve).
• Neural Processing: Temporal Lobe (both hemispheres)

Nose

• Stimulus: Chemical substances in a gaseous state
• Receptor: Olfactory Cells
  • Located in the nasal cavity; excitation leads to neural impulses (to olfactory nerve).
• Neural Processing: Temporal Lobe and Frontal Lobe

Tongue

• Stimulus: Chemical substances in a liquid state
• Receptor: Papillae
  • Contain taste buds with taste receptor cells, connects to facial and glossopharyngeal nerves.
• Neural Processing: Frontal Lobe and Insular Lobe (distinct lobe of cerebral cortex)

Skin

• Stimulus: Pressure, pain, temperature
• Receptors:
  • Meissner’s Corpuscles: Detect light touch and vibration.
  • Merkel’s Disks: Detect sustained pressure and texture.
  • Pacinian Corpuscles: Detect deep pressure and vibration.
  • Ruffini endings: Detect skin stretch and warmth.
  • Krause’s Corpuscle: Detect cold.
  • C-fibers/Free nerve endings: Detect pain, itch, and temperature changes.
• Neural Processing: Parietal lobe

Connecting Mechanism/Connector: The Nervous System

• A complex system of cells enables organisms to gain information and respond appropriately.
• Integrates messages throughout the body to build behavior.
• It is the organizer and regulator of behavior.

Basic Units: Neurons or Nerve Cells

• Neurons transmit nerve impulses.
  • Dendrites: Receive input signals from other neurons' axons, carrying signals to the cell body.
  • Cell body or soma: Contains genetic information.
  • Axons: Fibers that carry signals from the cell body to other nerve cells.
  • Myelin Sheath: Speeds up action potentials.
  • Action Potential: Electrical signal part.
  • Axon terminals: Relay information to the next neuron's dendrites.
• Synapse: Junction between neurons.
  • Nerve impulses transfer from a presynaptic neuron's axons to a postsynaptic neuron's dendrite via neurotransmitters.
  • Synaptic gap or synaptic cleft is the space.
  • Neurotransmitters are released as the action potential, or electrical signal, arrives at the axon's end.
  • Enables neurons to communicate.

Nerve

• Bundles of elongated axons numbered in the hundreds of thousands
• Glial cells hold nerves and nutrients in place.

Central Nervous System (CNS)

• Includes the brain and spinal cord
• Encased in bone for protection (skull and spinal column)
• Responsible for processing sensory information and sending signals for action
• Communicates through neurons via electrical signals

Spinal Cord

• A compact organ for nerve fibers connecting to the brain

Brain Stem

• Facilitates vegetative functions (heart rate, respiration) and instinctive behavior
• The lowest part of the brain

Functions of the Brain Stem

• It allows messages to travel between the upper brain and spinal cord.
• Functions: Breathing, blood pressure, heart rate, eye movement, and vomiting.

Brain

• The control system for the bodies of man and higher animals.
• Divided into the forebrain, midbrain, and hindbrain.

Forebrain (Prosencephalon)

• The most developed part/responsible for complex behavior and mental life

Diencephalon or Interbrain

• Thalamus: Controls sensory functions, affects visceral activity, acts as a relay station for sensory information (vision, hearing, touch, taste), and controls sleep and wakefulness.
• Hypothalamus: Regulates hunger, thirst, sex drives, endocrine activities, and homeostasis (temperature, heart rate, blood pressure); the seat of emotional behavior.

Telencephalon

• Largest part of the forebrain, also called the cerebrum.
• Limbic System controls instinctive behaviors.
• Hippocampus plays a vital role in memory.
• Cerebral Hemisphere: Two halves
  • Right hemisphere: Controls sensory and motor activities on the left side of the body, artistic brain controls music appreciation, arts, fantasy, perception dance, and other skills.
  • Left hemisphere: Controls sensory motor activities on the right side of the body, the technical brain controls math, language, science, writing, and logic.
  • Corpus Callosum: Connects the two brain hemispheres and coordinates activity.
• Cerebral Cortex: Outer surface of the cerebral hemisphere
  • Referred to as gray matter
  • Contains nerve cell bodies and unmyelinated nerve fibers.

Four Areas of the Cortex

• Frontal Lobe: Controls thinking, action, speech, and voluntary movements
• Parietal Lobe: Contains the centers at which incoming sensory impulses like heat, cold, touch, pain, and the body's sense of movement arrives
• Temporal Lobe: Contains auditory centers; taste and smell centers in the lower parts
• Occipital Lobe: Contains the visual center and lies under the back of the skull

Midbrain (mesencephalon)

• Relays information from the eyes, ears, and skin
• Controls certain types of automatic behavior

Hindbrain (Rhombencephalon)

• An extension of the spinal cord inside the skull

Medulla Oblongata

• Located at the base of the brain
• Continuous with the spinal cord
• Controls blood pressure, heart rate, breathing, reflexes, feedback systems, swallowing, and vomiting

Cerebellum

• A large independent structure, lying just below the occipital lobe
• Functions include making our movements smooth and accurate, posture and balance by making use of vestibular and kinesthetic impulses

Peripheral Nervous System (PNS)

• Includes nervous system parts outside the brain and spinal cord
• Responsible for transmitting sensory information to the CNS
• Responsible for and transmitting motor commands from the CNS to the rest of the body.

Autonomic Nervous System

• Controls involuntary, self-regulating body functions
  • Sympathetic Nervous System: Energizes internal organs during emotional excitation or activity, preparing the body for "fight or flight" by increasing heart rate, dilating airways, and redirecting blood flow.
  • Parasympathetic Nervous System: Dominant during rest, relaxation, or sleep, maintaining bodily functions and conserving resources by slowing heart rate and promoting digestion.

Somatic Nervous System

• Organizes voluntary body movements
• Makes the body aware of external stimuli
• Relays sensory information from the environment
• Transmits motor commands from the brain

Reacting Mechanism/Reactors: The Glandular System

• Critical for secreting hormones that regulate physiological processes

Exocrine Glands (Duct Glands)

• Pour secretions onto the surface through a duct (e.g., tear, salivary, sweat glands).
• Manifest reactions to emotions.

Endocrine Glands (Ductless Glands)

• Secrete hormones directly into the bloodstream to regulate various bodily functions
• Hormones secreted in normal quantities

Pituitary Gland (Hypophysis)

• Location: Base of brain
• Secretes: Growth hormones
• Function: Controls body growth.
• Malfunctions: Oversecretion – giantism, undersecretion – dwarfism.

Thyroid Gland

• Location: Base of the throat near the Adam’s apple
• Secretes: Thyroxin
• Function: Controls basal metabolism.
• Malfunctions: Oversecretion – hyperthyroidism(overstimulated, overactive, nervous, and irritable); undersecretionhypothyroidism (mental and physical growth arrested).

Parathyroid Glands

• Location: Back portion of the thyroids
• Secretes: Parathormone
• Function: Regulates calcium phosphate metabolism.
• Malfunctions: Undersecretion - Tetany (a state of spasm of muscles).

Adrenal Glands

• Location: Atop each kidney

• Secretes: Corticosteroids and adrenaline

• Essential for normal body functions

• Malfunctions: Decreased Activity (Weight loss, Low blood pressure, weakness), Increased Activity (Obesity, high blood pressure, increase in blood sugar level, weakening of bones)

Gonads

• Location: Testes
• Testosterone stimulates the development of Male Secondary Sex Characteristics .
• Location: Ovaries, Secretes; Estrogen and Progesterone
• Stimulates development of Female Secondary Sex Characteristics, and also maintains pregnancy.
• Over/Under malfunctions can affect reproduction functions.

Pancreas

• Location: Behind the stomach
• Secretes: insulin
• Function: Regulates the metabolism of blood glucose (sugar).
• Malfunctions: Undersecretion-Hypoglycemia (low blood sugar), Oversecretion Hyperglycemia (high blood sugar)