Animal responses to the environment

LIFE SCIENCES2011

J Gerber and J Goliath 1

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


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


Location and functions of : Cerebrum Hypothalamus Cerebellum Medulla oblongata Spinal cord Model of human brain Observe and draw the external structure

of the brain


Dagga Heroin Ecstacy Tik


Peripheral nervous system Location and function

Autonomic nervous system Location and function


Causes, symptoms, treatment of ONE of the following diseases/disorders of the nervous system:

Alzheimer’s Disease OR Attention Deficit Disorder OR Depression


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)


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


Receptors on the skin of wood lice are sensitive to humidity and light

Wood lice move away from light and dry environments


The systems below work together to respond to external and internal changes:

Nervous system

Endocrine system (hormones)



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.


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


Location

Situated behind and underneath the cerebrum

Functions

Controls the co-ordination of voluntary movements

Contain the centres which control balance and equilibrium


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


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


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.


Heroin

This drug has a depressive effect on the CNS, slows down breathing and suppresses pain.

Inhibits the activity of the medulla oblongata.


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.


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


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


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.


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.



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.


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.


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.



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.


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.



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.


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.



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.


Reflex arcs protect the body from dangerous situations from the external environment.


Instructions Explanation of activity on a reflex arc. After 10 minutes each pair/group/individual give feedback.


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


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.


1.1 Reflex

1.2 Reaction was quick/sudden; without even thinking about

it/autonomic.

1.3


Documents

Animal responses to the environment