Animal responses to the environment

1. Animal responses to the environment LIFE SCIENCES 2011 J Gerber and J Goliath

2. Human nervous system Hormones and nerves enable animals to: • Respond to internal and external change • Co-ordinate the various activities of the body • Observations of the response of some invertebrates e.g wood lice, to light and humidity J Gerber and J Goliath

3. Human nervous system The need for a nervous system in humans in terms of: • Reaction to stimuli (external and internal) • Co-ordination of various activities of the body J Gerber and J Goliath

4. Central nervous system Location and functions of : • Cerebrum • Hypothalamus • Cerebellum • Medulla oblongata • Spinal cord • Model of human brain • Observe and draw the external structure of the brain J Gerber and J Goliath

5. Effects of drugs on the CNS • Dagga • Heroin • Ecstacy • Tik J Gerber and J Goliath

6. Human nervous system Peripheral nervous system • Location and function Autonomic nervous system • Location and function J Gerber and J Goliath

7. Disorders of the CNS • Causes, symptoms, treatment of ONE of the following diseases/disorders of the nervous system: • Alzheimer’s Disease OR • Attention Deficit Disorder OR • Depression J Gerber and J Goliath

8. Structure and function of a nerve • Generalised structure of a neuron including: nucleus, cell body, cytoplasm, myelin sheath, axon and dendrites • Labelled drawings to show the three types of neurons from microscope slides or micrographs • Structure and functions of the three types of neurons • The nerve is composed of nerve fibres held together by connective tissue • Transmission of nerve impulses along neurons and across synapses using neurotransmitters (no detail of electrical charges needed) J Gerber and J Goliath

9. Simple reflex arc • Difference between reflex arc and reflex action • Observe microscope slides and draw and LABEL the cross section through the spinal cord • Structure of a simple reflex arc (receptor, sensory neuron, dorsal root of spinal nerve, spinal cord, interneuron, motor neuron, ventral root of spinal nerve, effector) • Functioning of the reflex arc, use an example • Significance of a reflex arc J Gerber and J Goliath

10. Response of some invertebrates to light and humidity • Receptors on the skin of wood lice are sensitive to humidity and light • Wood lice move away from light and dry environments J Gerber and J Goliath

11. Coordinating systems in humans The systems below work together to respond to external and internal changes: • Nervous system • Endocrine system (hormones) J Gerber and J Goliath

12. Central nervous system J Gerber and J Goliath

13. CNS - Cerebrum Location • Largest part of the brain is situated in the skull. Functions • Centre of all voluntary actions • Contains areas that receive and interpret nerve impulses from the sense organs for the sensation of smell, sound, sight, taste and touch. • Centre of higher mental functions e.g memory, intelligence, emotions etc. J Gerber and J Goliath

14. CNS - Hypothalamus Location • Situated under the thalamus. Functions • Reflex control centre of mechanisms such as temperature, blood pressure, sleep and emotion • Produces certain hormones e.g. ADH which assist in maintaining water balance • Control centre for homeostasis J Gerber and J Goliath

15. CNS - Cerebellum Location • Situated behind and underneath the cerebrum Functions • Controls the co-ordination of voluntary movements • Contain the centres which control balance and equilibrium J Gerber and J Goliath

16. CNS – Medulla oblongata Location • Forms bottom part of the brain stem and is an extension of the spinal cord Functions • Transmitter of impulses between brain and spinal cord • Controls autonomic functions e.g. breathing, heartbeat, peristalsis, widening and narrowing of blood vessels J Gerber and J Goliath

17. CNS – spinal cord Location • Extends from the medulla oblongata through the vertebral canal to the lumber region Functions • Provides a pathway for nerve impulses to and from the brain • Contains reflex centres that initiate reflex actions J Gerber and J Goliath

18. Effects of certain drugs on CNS Dagga • Chemical substance in dagga combines with specific receptors (memory, concentration, movement) in the brain and inhibits the normal functioning of these receptors. Heroin • Has a depressive affect on the CNS, slows down breathing and suppresses pain. J Gerber and J Goliath

19. Effects of certain drugs on CNS Heroin • This drug has a depressive effect on the CNS, slows down breathing and suppresses pain. • Inhibits the activity of the medulla oblongata. J Gerber and J Goliath

20. Effects of certain drugs on CNS Ecstacy • Causes an excessive release of a certain neurotransmitter which over stimulates brain neurons which causes damage to the terminal branches of the axons • Negative effect on the emotions, memory and ability to learn. J Gerber and J Goliath

21. Effects of certain drugs on CNS Tik • Has a stimulating effect on the CNS e.g. accelerated breathing and heart rate. • Causes an excessive release of a certain neurotransmitter which over stimulates neurons in the brain and damage these neurons J Gerber and J Goliath

22. Peripheral nervous system Location • Nervous tissue found outside the CNS and is subdivided into the somatic and autonomic nervous systems. Consist of 12 pairs of cranial nerves and 31 pairs of spinal nerves Functions • Conduct nerve impulses from the receptors to the CNS, along the sensory neurons • Conduct nerve impulses from the CNS to the effectors, along the motor neurons J Gerber and J Goliath

23. Autonomic nervous system Location • Consists of nerves which are connected to the CNS. Consists of the following systems i.e. sympathetic and parasympathetic. Functions • Controls all involuntary actions. • Conducts nerve impulses from the CNS to the effectors e.g. muscles and glands. • Sympathetic system prepares the body for emergency. • Parasympathetic system allows the body to return to normal after stimulation by the sympathetic system – antagonistic. J Gerber and J Goliath

24. Generalized structure of a neuron • Same basic structure as any other cell. • Cell body consists of cytoplasm and a nucleus. • Cytoplasm contains Nissl granules which are rich in RNA and play a role in protein synthesis. • Two types of outgrowths – dendrites and axons. • Dendrites conduct nerve impulses to the cell body. • Axons conduct impulses away from the cell body. • Axons are surrounded by a myelin sheath for protection. J Gerber and J Goliath

25. Generalised structure of a neuron J Gerber and J Goliath

26. Different types of neurons - structure • Neurons are classified based on the number of outgrowths projecting from the cell body. Structure of different neurons • Monopolar neurons – one outgrowth that branches into two, i,e, one dendrite and one axon. • Bipolar neurons – two outgrowths, i.e. a dendrite and axon. • Multipolar neurons – many outgrowths, a number of dendrites and one axon. J Gerber and J Goliath

27. Functions of neurons • Neurons are classified according to their function as follows: • Sensory or afferent neurons – conduct impulses from the receptors to the CNS and are mostly monopolar. • Motor of efferent neurons – conduct impulses from the CNS to the effectors and are multipolar. • Interneurons or connector neurons – connect sensory and motor neurons in the CNS and are multipolar. J Gerber and J Goliath

28. Structure of a nerve • Neurons are bundled together in the human body. • Small bundles of axons are called nerve fibres. • Nerve fibres are bundled together with some connective tissue. • Nerve fibres and connective tissue make up nerve tissue. J Gerber and J Goliath

29. Structure of a nerve J Gerber and J Goliath

30. Transmission of nerve impulses • Neurons are interconnected to form a continuous conduction system throughout the body. • The axon of one neuron connects with the dendrites of the next neuron. • Successive neurons are not directly connected to each other, but seperated by a small gap. • A physiological (functional) connection is formed known as a synapse. • The gap is called the synaptic cleft. J Gerber and J Goliath

31. Transmission of nerve impulses - continue • A receptor is stimulated by a change in the environment and produces impulses. • Dendrites of a sensory neuron conduct these nerve impulses to the cell body. • Nerve impulses are conducted from the cell body along a single axon to the terminal branches. • Ends of terminal branches do not touch the dendrites of the neurons in the spinal cord because of a gap. • Ends of terminal branches of axons contain neurotransmitters which are released into the synapse when the terminal branches of axons are stimulated by an incoming impulse. • Neurotransmitters play a role in the transmission of nerve impulses. J Gerber and J Goliath

32. Transmission of nerve impulses across a synapse using neurotransmitters J Gerber and J Goliath

33. Simple reflex arc • Reflex action – a quick, automatic movement/action by an effector, in response to a stimulus received by a recepto.r • Reflec arc – pathway along which nerve impulses are carried from a receptor to an effector to bring about a reflex action. J Gerber and J Goliath

34. Structure of a reflex arc • Receptor – detects a stimulus and converts into a nerve impulse. • Sensory neuron – conducts the nerve impulse to the grey matter of the spinal cord. • Interneuron – serves as a reflex centre in the grey matter of the spinal cord and conducts nerve impulses from the sensory neuron to the motor neuron. • Motor neuron – conducts the nerve impulses from the spinal cord to the effector. • Effector – reacts to the original stimulus. J Gerber and J Goliath

35. Structure of a reflex arc J Gerber and J Goliath

36. Functioning of the reflex arc e.g. somebody touches a hot plate • Heat stimulus received by a receptor and convert into a nerve impulse. • Nerve impulse is transmitted by the sensory neuron through the dorsal root of spinal cord. • Sensory nerve transmits the impulse to the interneuron in grey matter of spinal cord. • Neuron is connected synaptically to the motor neuron. • Axon of the motor neuron transmits the impulse through the ventral root to the effector. J Gerber and J Goliath

37. Significance of a reflex arc • Reflex arcs protect the body from dangerous situations from the external environment. J Gerber and J Goliath

38. Activity Instructions • Explanation of activity on a reflex arc. • After 10 minutes each pair/group/individual give feedback. J Gerber and J Goliath

39. Activity QUESTION 1 Tommy was keeping his finger over a burning candle. In about 0,2 seconds he pulled his finger away. 1.1 What type of action is Tommy’s reaction? 1.2 Explain your answer to QUESTION 1.1 J Gerber and J Goliath

40. Activity QUESTION 1.3 Diagram 1 below shows a cross section through Tommy’s spinal cord. Diagram 2 shows Tommy’s finger over the burning candle and a muscle in his arm. Draw the missing parts/structures and also indicate the path (use different colours if possible) followed by the impulse during the reaction named in QUESTION 1.1. J Gerber and J Goliath

41. Answers 1.1 Reflex 1.2 Reaction was quick/sudden; without even thinking about it/autonomic. 1.3 J Gerber and J Goliath