VCE BIOLOGY

www.drlakshmisharma.comDr Lakshmi Sharma

NO LIMITS TO LEARNING! BELIEVE & YOU CAN ACHIEVE!

Regulatory Mechanisms in Animals

Regulatory Mechanisms in Animals

What do we mean by Regulatory Mechanisms in

Animals ???

Hormone released from glands, neurotransmitters released from nerve endings

Mammals well developed – maintain a stable internal environment with changing conditions HOMEOSTASIS involves –ve feedback.

Maintaining Equilibrium

Communication within an animal requires mechanisms: Hormonal Nervous

Negative Feedback

Nervous & Hormonal system

promoting stability of internal environment

Stimulus Response Mechanism

the response reduces original stimulus

(–ve effect on stimulus)

Negative Feedback

Hormones -Slower than nervous responses

Synthesised from fatty acids

Small & lipid-soluble, easily pass thro membranes – nucleus-act on genes

Steroid hormones – testosterone & oestrogenAmino Acid Hor Fatty Acid Hor

Hormones -Slower than nervous responses

Synthesised from amino acids

Water soluble, cannot pass through membranes – bind to receptors plasma membrane, responses in cell. Adrenaline & growth hormonesAmino Acid Hor Fatty

Acid Hor

Endocrine glands release hormones directly into the circulatory system

Pituitary Gland

Central role in overall endocrine regulation

Growth, lactation, reproductive state, skin pigmentation, fat tissue, kidney function & activity of thyroid and adrenal glands

Pituitary Gland

Hypothalamus -collects info the body’s state (water, food, pain, emotions), releases releasing hormones to pituitary

Pituitary- receives info, releases hormones regulate body’s response

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

Thyroid stimulating hormone releasing hormone

Hypothalamus

via blood vesselsreleases

releases

via blood vessels

Sequence of hormones in release of thyroxine from the thyroid gland

Hormones Video

Endocrine System

Please go to dnatube.com - excellent video resource

Endocrine - Mr Anderson

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

Requires a lot of energy to run

Nervous Systems – Evolution

Note development of a bundle of nerves at the front of the animal

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

Stretch Receptor

Effector Muscle

Receptors in Skin

Withdrawal Reflex

Spinal cord

Nervous Response

Environmental Disturbance

(eg. hot plate)

Sensory Cells (skin)

Effector Cells

(muscles)

Neurons sensory, interneuro

ne & motor

Response

(pull hand away)

Interneurons

Neurons that transmit information from one neuron to another (97% of human neurons are interneuron)

Allow more co-ordination & integration

Tread on nail, can’t withdraw your foot interneurons instruct muscles of opposite leg to bear weight

Try balancing on one foot.

Reflexes in Homeostasis Baroreceptor-heart rate reflex maintains blood

pressure

Neurons

Signals travel quickly along neurons as electrical

impulses

The signals that travel between neurons, across the

synapse are chemical

Nerve Bundle - many neurons group together

forming a single nerve

Types of Neurons

THE STRUCTURE OF NEURONS

Synapse

Nerve Bundle

Action Potentials

Nerve impulse or action potential is a wave of electrical change along the

axon membrane stimulation

At the dendrite it stimulates the release 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

The Nervous System

Mammalian Nervous Systems

Central nervous system (CNS) – ‘co-ordinating centre’ BrainSpinal cord

Peripheral Nervous System – ‘sensing and responding’

Motor (muscular) neuronsSensory neurons

The Central Nervous System

Human Nervous System

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

VisionPhotoreceptor cells contain

Light sensitive pigments

Light with the pigment creates

an electrical signal

in a sensory nerve

Colour Blindness Inherited & affects more boys than girlsLack one or more of the cone cells.

The Nervous System Video

The nervous system

The nervous system short video

Mind Maps of the Nervous System

The following are nervous system mind maps to help you – read through the ppt & devise your own mindmap

HOPE YOU ENJOYED THE LESSON !

ANY QUESTIONS ???!