IGCSE Biology: Coordination and Response Part 1 Explained

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in this video you are going to learn part 1 of topic 14 coordination and response

organisms require proper coordination between various organs and systems to work together to keep them alive

they have to be able to sense changes in their environment and respond to them appropriately

the nervous system plays a key role in the coordination and regulation of body functions

it is responsible for receiving and processing information from the environment and from within the body and

then generating appropriate responses to maintain homeostasis or the stable internal environment of the body

for example when you are exposed to cold temperatures your neurons detect the drop in temperature and send a signal to

your brain which then triggers a response to generate heat through shivering to maintain your body

temperature the nervous system consists of millions of neurons or nerve cells

information is sent through the nervous system as electrical impulses that travel along neurons for quick

communication a bundle of neurons is known as a nerve the mammalian nervous system is composed

of the central nervous system which consists of the brain and the spinal cord shown in yellow

and the peripheral nervous system consisting of all of the nerves in the body outside of the brain and the spinal

cord shown in pink there are three types of neurons Sensory neurons carry impulses from the

sense organs to the central nervous system that is the brain or the spinal cord

relay neurons are found inside the central nervous system and connect sensory and motor neurons

and motor neurons carry impulses from the central nervous system to effectors that is the muscles or glands

so you are expected to identify in diagrams and images sensory relay and motor neurons so as you can see Sensory

neurons are long and have a cell body in the middle of the Axon relay neurons are short and have a small

cell body at one end with many dendrites branching off it and motor neurons along with a large

cell body on one end and long dendrites branching off it next we must learn the meanings of a

stimulus receptor and effector in order to understand the pathway of an Impulse in the nervous system

a stimulus is any change in the environment that can be detected by Sensory neurons such as light sound

touch temperature or chemicals so let's consider fire for this example a receptor is a structure that can

detect a stimulus it generates an electrical impulse when it detects a stimulus which is then sent to the

central nervous system so in this Example The receptors are in the skin of the hand

an effector is a structure often a muscle or a gland that responds to a signal from the nervous system resulting

in a specific action or behavior so in this case the effector will be the muscles of the arm which will carry out

the response by pulling the arm away from the fire let's understand what a voluntary and

involuntary response is before moving on to the reflex arc a voluntary response is a conscious

action something you do on purpose because you choose to so this response begins from your brain

an example of a voluntary response is deciding to raise your hand to answer a question in class

an involuntary response on the other hand is a quick and automatic reaction to a stimulus that happens without us

having to think about it therefore the brain is not needed to coordinate the response

so in this type of response you are not aware that you carried it out until after it has happened

these quick responses are very important for survival since voluntary responses take longer

an example of an involuntary response is when we touch something hot and our hand quickly pulls away before we even

realize it's hot so as we just learned an involuntary or reflex response is a fast and automatic

reaction that doesn't involve the brain and it helps protect the body from harm a reflex arc refers to the pathway that

a nerve impulse follows in an involuntary or reflex response so for example let's say we accidentally

touch fire the stimulus will be the fire the receptor cells on the skin will

detect the stimulus the sensory neuron sends electrical impulses to the spinal cord the

coordinator the sensory neuron passes it on to the relay neuron in the spinal cord

the relay neuron connects to the motor neuron and passes the impulse on the motor neuron carries the impulse to

a muscle in the arm that is the effector the muscle will contract and pull the arm away from the fire this is the

response here's a simple diagram to show the reflex arc

the stimulus is detected by a receptor and converted into an electrical impulse the electrical impulse travels along the

sensory neuron it then passes on to the relay neuron which connects to the motor neuron

and the motor neuron carries the impulse to the effector and the effector carries out the

response therefore a reflex action is a means of automatically and rapidly integrating

and coordinating stimuli with the responses of effectors that is muscles and glands

next synapses a synapse is a junction between two neurons neurons never touch each other so they

have gaps in between them called synapses let's look at the structure of a synapse

these are vesicles containing neurotransmitter molecules this is the synaptic gap

and these are receptor proteins so what happens at a synapse neurons have vesicles containing

neurotransmitter molecules neurotransmitters are chemical Messengers so this is the only part of

the nervous system where messages are chemical instead of electrical an Impulse travels along the first

neuron Neuron a and stimulates the release of neurotransmitter molecules from vesicles into the synaptic gap

the neurotransmitter molecules diffuse across the gap neurotransmitter molecules bind with

receptor proteins on the next neuron an Impulse is then stimulated in the next neuron

synapses ensure that impulses travel in One Direction only so that concludes part 1 of chapter 14

coordination and response hope this video helped you please share your thoughts and suggestions in the

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