Biology Class: Coordination and Hormones

Introduction

• Organisms perform various tasks requiring coordination and interaction among body parts.
• Organisms adapt to environmental changes, detecting changes, analyzing them, and issuing commands.
• Coordination is the process of different units working together for a function.

Stimulus

• A stimulus is a change in environment detectable by a sense organ.
• Stimuli trigger a response.
• Examples: heat, light, sound, gases, solids, liquids.
• Special cells/organs called receptors detect changes.

Response

• Response is the activity performed by an organism after analyzing a stimulus.
• Muscles and glands are effectors.
• Stimulus detected, analyzed, and a response is generated.

Types of Coordination

• Two main types of coordination: chemical and nervous.
• Chemical coordination involves signaling molecules (hormones) released by glands to stimulate or inhibit body cells.
• It is suitable for lower animals with simpler body plans.
• Nervous coordination uses neurons (nerve cells) to transmit electrochemical signals rapidly.
• It is a more advanced type of coordination found in animals.
• Both types often interact and work together.

Coordination in Lower Organisms and Plants

• Lower organisms (prokaryotes, protozoa, etc) and plants use chemical coordination (like hormones).
• Examples of responses include plant leaf movements, growth, metabolism and reproduction.

Human Nervous System

• The human nervous system is a centralized type (CNS).
• It receives stimuli from organs, integrates them in the CNS, and generates appropriate responses.
• CNS consists of the brain and spinal cord.

Brain

• The brain is the major control center.
• It has protective membranes called meninges and cerebrospinal fluid (CSF) for cushioning.
• Main parts include the cerebrum, hippocampus, amygdala, thalamus, hypothalamus, mid-brain, cerebellum and medulla oblongata.

Cerebrum

• It is the largest part of the brain, the seat of intelligence, memory, and conscious activities.
• It contains two hemispheres, each controlling the opposite side of the body.
• Divided into frontal, parietal, temporal, and occipital lobes, associated with different functions.

Thalamus

• Involved in sensory processing.
• Guides nerve signals to the correct parts of the brain.

Hypothalamus

• Regulates essential life-maintaining functions like blood pressure, body temperature, and hunger.

Hippocampus

• Related to long-term memory.

Amygdala

• Involved in emotions, pain, and pleasure.

Mid-brain

• Integrates visual and olfactory stimuli.
• Collaborates with the forebrain.

Cerebellum

• Involved in maintaining balance and precision in muscle movements.

Medulla Oblongata

• Controls autonomic functions like breathing, heart rate and blood pressure.

Spinal Cord

• Acts as a communication pathway between the brain and the rest of the body, enabling reflexes.
• It runs through the vertebral column.

Neurons

• Neurons (nerve cells) transmit information by electrochemical impulses.
• Neurons have a cell body (soma), dendrites (receive signals), and axon (transmit signals).
• Myelin sheath insulates the axon for faster signal transmission.

Reflex Action

• Reflex actions are involuntary, automatic responses to stimuli.
• They usually involve sensory neurons, interneurons, and motor neurons.
• The pathways are called reflex arcs.
• Examples : blinking, withdrawing from heat, knee-jerk reflex.

Receptors

• Specialized sensory cells or structures that detect stimuli.
• They convert stimuli into nerve impulses.
• Examples: eyes detect light, ears detect sound, skin detects touch and temperature.

Eye

• The eye is a complex structure resembling a camera.
• Light enters through the cornea, lens focuses light onto the retina, containing photoreceptor cells (rods and cones).
• Rods detect low light, while cones detect color.
• The ciliary muscles adjust lens shape for focusing.
• Pupil reflexes adjust to light intensity.
• Accommodation allows eye focusing.
• Role of vitamin A in vision.

Ear

• Outer ear collects sound waves.
• Middle ear transmits sound waves via ossicles (three small bones).
• Inner ear has hair cells on the cochlea, which transmit sound information to the brain.
• Semicircular canals help with balance.

Endocrine System

• Endocrine system uses hormones to coordinate body functions (chemical coordination).
• Hormones are chemical messengers released into the bloodstream.
• They affect target tissues/organs.

Pituitary Gland

• Important endocrine gland located in the brain.
• Anterior pituitary releases hormones that affect other glands.
• Posterior pituitary stores and releases hormones from the hypothalamus.

Thyroid Gland

• Located in the neck, secretes thyroxine regulating metabolic rate and growth.
• Calcitonin regulates calcium levels.
• Deficiency of iodine can lead to goiter.

Pancreas

• Both exocrine and endocrine gland.
• Islets of Langerhans secrete insulin and glucagon for sugar regulation.
• Insulin lowers blood sugar; glucagon raises it.

Diabetes Mellitus

• A disorder resulting from insufficient/no insulin.
• Glucose level in blood increases, and excess glucose is excreted.

Dietary Management of Diabetes

• Important to control blood sugar by a balanced diet, exercise, medication.
• Foods like whole grains, fruits, vegetables, and lean protein are recommended.

Blood Glucose Chart

• Chart used for measuring normal blood glucose levels in fasting and after eating.

Adrenal Gland

• Located on top of the kidneys, it has a cortex and medulla.
• Cortex produces steroid hormones for metabolism, salt balance, and immune response.
• Medulla produces adrenaline for the "fight or flight" response.

Gonads (Testes and Ovaries)

• Involved in reproduction and hormone production (testosterone in males, estrogen and progesterone in females).
• Hormones control secondary sexual characteristics (e.g., growth, voice, and physical appearance of breasts or facial hair).

Disorders of the Nervous System

• Examples : paralysis (caused by damage to parts of nervous system) and epilepsy (caused by unusual electrical activity in brain).