chapter 15. regulatory mechanisms in animals
TRANSCRIPT
Regulatory Mechanisms in Animals
Chapter 15
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
Endocrine Glands• Organs that produce and release
hormones directly into the circulatory system
• Fig 15.2 page 280
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
see figure 15.3 in your textbook
pituitary
hypothalamus
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
Thyroxin Hormone
• Stimulates metabolic rate of cells
• Involved in physical development
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
Hypothalamusvia blood vessels
releases
releases
via blood vessels
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
Nervous Systems – EvolutionNote development of a bundle of nerves at the front of the animal
Knee-Jerk Response – Simplest of all
Stretch Receptor
Effector Muscle
Count the nerves!
Sensory Neuron?
Receptors in Skin Effector Muscle
Interneuron?Motor Neuron?
Withdrawal Reflex
Spinal cord
Nervous Response
Environmental Disturbance
(eg. hot plate)
Sensory Cells (skin)
Effector Cells
(muscles)
Neurons sensory,
interneurone & motor
Response
(pull hand away)
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.
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!
Reflexes in Homeostasis• Baroreceptor-heart rate reflex maintains
blood pressure
• Also see Fig 15.10 page 287
Task
• Draw a stimulus response model to represent the control of blood pressure
Cell Body
Myelin sheath
Axon
Nerve endings
Nucleus
Dendrites
THE STRUCTURE OF NEURONS
Nerve Endings
Nerve endings
Mammalian Nervous Systems• Central nervous system (CNS) – ‘co-
ordinating centre’ – Brain– Spinal cord
• Peripheral Nervous System – ‘sensing and responding’– Motor (muscular) neurons– Sensory neurons
Human Nervous System
• See Fig 15.3 page 282• Note location and function of:
– Cerebral cortex– Hypothalamus– Cerebellum– Brainstem
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)
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
Major Sense OrgansTypes 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
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)
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)
Cell Body
Nerve Endings
Nerve endings
Neurons• Signals travel quickly along neurons an
electrical impulses
• The signals that travel between neurons, across the synapse are chemical
Nerve Bundles• See fig 15.12 p 291
• Many neurons group together forming a single nerve
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