Chapter 15. regulatory mechanisms in animals
- 2. Hormones Are: • Produced in one part of the organism and pass through a transport system to target tissue • Specific – stimulus only affects certain hormone secreting cells – only certain cells can respond • Relatively slow
- 3. Endocrine Glands • Organs that produce and release hormones directly into the circulatory system • Fig 15.2 page 280
- 4. For a list of the glands and what they do see Table 15.1 page 281 of your text Note: Endocrine glands release hormones directly into the _____________ system
- 6. see figure 15.3 in your textbook pituitary hypothalamus
- 7. Pituitary Gland • Central role in overall endocrine regulation • Growth, lactation, reproductive state, skin pigmentation, fat tissue, kidney function & activity of thyroid and adrenal glands • Connected to the hypothalamus – Hypothalamus -collects info about the body’s state (water, food, pain, emotions) and releases releasing hormones to the pituitary – Pituitary- receives this info and releases hormones to regulate the body’s response • Fig 15.4 page 283
- 8. Thyroxin Hormone • Stimulates metabolic rate of cells • Involved in physical development
- 9. Anterior Pituitary Gland Thyroid Stimulating Hormone Thyroid Gland Thyroxine Target Cells (most cells in the body) via blood vessels Stimulates an increase in metabolic rate in cell Thyroid stimulating hormone releasing hormone Hypothalamus via blood vessels releases releases via blood vessels
- 10. Nervous Systems • More direct pathway of communication • Extremely rapid responses are possible • Functional unit is the neuron • Neurons communicate between – Sensory cells that detect a disturbance – Effector cells that produce the response • Specific receptors bring about highly precise responses • Expensive, require a lot of energy to run
- 11. Nervous Systems – Evolution Note development of a bundle of nerves at the front of the animal
- 12. Knee-Jerk Response – Simplest of all Stretch Receptor Effector Muscle Count the nerves!
- 13. Sensory Neuron? Receptors in Skin Effector Muscle Interneuron? Motor Neuron? Withdrawal Reflex Spinal cord
- 14. Nervous Response Environmental Disturbance (eg. hot plate) Sensory Cells (skin) Effector Cells (muscles) Neurons sensory, interneurone & motor Response (pull hand away)
- 15. Interneurons • Neurons that transmit information from one neuron to another • Allow more co-ordinated responses – Withdrawal reflex in hand • Triceps stay relaxed – Withdrawal reflex in foot • Opposing foot braces itself • Task try balancing on one foot.
- 16. The Reflex Response • A reflex is a rapid, unconscious response – hand on a stove – Stand on a pin • Brain registers the ‘pain’ but doesn’t facilitate the response (spinal cord does) • Knee-jerk response involves only 2 neurons!
- 17. Reflexes in Homeostasis • Baroreceptor-heart rate reflex maintains blood pressure • Also see Fig 15.10 page 287
- 19. Task • Draw a stimulus response model to represent the control of blood pressure
- 22. Cell Body Myelin sheath Axon Nerve endings Nucleus Dendrites THE STRUCTURE OF NEURONS Nerve Endings
- 23. Nerve endings
- 24. Mammalian Nervous Systems • Central nervous system (CNS) – ‘co- ordinating centre’ – Brain – Spinal cord • Peripheral Nervous System – ‘sensing and responding’ – Motor (muscular) neurons – Sensory neurons
- 26. Human Nervous System • See Fig 15.3 page 282 • Note location and function of: – Cerebral cortex – Hypothalamus – Cerebellum – Brainstem
- 27. Human Nervous System Central Nervous System (brain & spinal cord) Peripheral Nervous System Voluntary (somatic) -skeletal muscles Involuntary (autonomic) -unconscious responses See Table 15.2 page 288 Sensory (info to the CNS) Motor (signals to effector-organs)
- 28. Autonomic Nervous System (unconscious responses) • Sympathetic division – Increases energy use – Prepares body for action • Parasympathetic division – Conserves energy – Slows heart rate • Enteric division – Nerves specific to gut
- 29. Major Sense Organs Types of Receptors • Photoreceptors – Visible light, infrared radiation • Chemoreceptors – Taste, smell, communication – Oxygen, CO2, pH, water, salts etc • Mechanoreceptors – Hearing, balance, pressure, touch • Thermoreceptors – Heat and cold
- 30. Vision • Photoreceptor cells contain light-sensitive pigments that • The interaction of light with the pigment creates an electrical signal in a sensory nerve • Types of eyes – Simple – Compound (see fig 15.11 p 289)
- 31. Neurons • Cell body – Nucleus – Usual cell functions • Dentrites – Carry impulses towards cell body • Axons – Carry impulses away from cell body to next neuron • Synapse – Space across which one neuron makes contact with another • Myelin – Like insulation tape around a neuron (fatty)
- 33. Nerve endings
- 34. Neurons • Signals travel quickly along neurons an electrical impulses • The signals that travel between neurons, across the synapse are chemical
- 35. Nerve Bundles • See fig 15.12 p 291 • Many neurons group together forming a single nerve
- 36. Action Potentials “When a nerve is stimulated its cell membrane is depolarised so that the inside of the cell becomes less negative. The potential is conducted along the axon to the axon terminal. At the dendrite it stimulates the realease of a chemical transmitter, which diffuses across a synapse. The transmitter binds to receptor sites on the postsynaptic cell membrane to stimulate the generation of another impulse.” • My advice – carefully read and re-read page 291-293 when you have a quite period at home