Animal responses to the environment LIFE SCIENCES 2011

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

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 2

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 3

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 4

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

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

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 7

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 8

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 9

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 10

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 11

Central nervous system J Gerber and J Goliath 12

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 13

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 14

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 15

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 16

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 17

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 18

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 19

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 20

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 21

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 22

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 23

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 24

Generalised structure of a neuron J Gerber and J Goliath 25

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 26

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 27

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 28

Structure of a nerve J Gerber and J Goliath 29

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 30

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 31

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

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 33

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 34

Structure of a reflex arc J Gerber and J Goliath 35

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 36

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

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

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

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 40

Answers 1. 1 Reflex 1. 2 Reaction was quick/sudden; without even thinking about it/autonomic. 1. 3 J Gerber and J Goliath 41