Control and Coordination

Science - Control and Coordination

Part 1 - Receptors and Stimuli

• The information that the body receives to cause a response is called a stimulus.

• Information (stimuli) about our external environment is collected by cells called receptors and sent to the central nervous system (brain.)

• The sense organs have highly specialised receptors to receive stimuli from the environment.

• These receptors are named according to the type of stimuli that they respond to.

• Receptors receive energy from the environment and convert this energy into a form that can be understood by the brain.

Olfactory Receptors

• Gaseous molecules from the air are breathed in through the nose, these gases dissolve into the mucus of the nasal cavity, and the hair like cilia of the nasal chemoreceptors are stimulated to send a message via the olfactory nerve to the brain to interpret it, giving the sensation of smell.

Touch

• Your skin contains a variety of types of receptors.

• Pain receptors and mechanoreceptors enable you to detect whether objects are sharp and potentially dangerous.

• There are also hot thermoreceptors that detect an increase in skin temperature above the normal body temperature (37.5°C) and cold thermoreceptors that detect a decrease below 35.8°.

• The sensitivity of these receptors can depend on how close together they are and the location in your skin.

Photoreceptors

• There are two types of photoreceptors that are sensitive to electromagnetic (light) energy.

• Cones are found in the retina, especially in the fovea at the back of the eye. They are involved in colour vision and visual activity (sharpness).

• Rods are found in the periphery of the retina, and are involved in night/low light vision.

Gustation (Taste)

• The tongue is the sense organ for taste (gustation).

• It was once thought taste buds in different regions of the tongue could detect particular flavours such as salty, sweet, bitter and savoury.

• New Scientific discoveries have disproved this model and it has now been replaced with a new model to explain how we gain our sense of taste.

New Discoveries

• In the new model, taste buds located within bumps called papilla across the tongue have the ability to sense all flavours.

• This is because each of these tastebuds contains taste cells with receptors for each type of flavour.

• Our brains are wired so that we enjoy sweet, savoury and salty foods so that we can obtain the energy, protein and nutrients that we need to survive.

• There are about 10,000 receptors in the mouth. Taste is dulled when you have a stuffy nose and taste is influenced by smell.

From mouth to brain

• Sensation begins when taste receptors in the mouth are stimulated by chemical molecules (dissolved in saliva) in food and drink.

• Any substance that is soluble in saliva can stimulate the taste receptors, located in the taste buds. Once taste receptors are stimulated, they convert sensory input (taste) into electrical impulses that are sent via facial cranial nerves from the mouth to the brain.

Part 2 - Neurons

• The nervous system is made up of specialized cells called neurons (nerve cells.)

• Neurons carry information around the body in the form of electrical impulses

• This occurs very fast.

• Impulses travel along the neurons in one direction only.

A bundle of neurons = a NERVE

• A neuron is a nerve cell that is the basic building block of the nervous system. Neurons carry electrical messages called nerve impulses.

• A nerve consists of a cell body, with branching dendrites (signal receivers) and a projection called an axon, which conducts the nerve signal to the end of the neuron.

Parts of the neuron

• Cell body: Contains the nucleus

• Dendrites: Branches from the cell body that receive messages from other neurons

• Axon: Nerve fibre that sends impulses away from the cell body

• Synaptic terminal: Passes message onto the dendrite of the next neuron

• Myelin sheath: Fatty layer that surrounds the axon of a neuron. It insulates the neuron and increases the speed of the nerve impulses.

Types of Neurons

• Sensory neurons carry messages from the sense organs (eg: eyes, tongue etc) TO CNS

• Interneurons are located in the CNS (connect sensory and motor neurons)

• Motor neurons carry information AWAY from the CNS to muscles and glands

Synapses

• Neurons are NOT connected

• There is a gap between each neuron called a synapse

• Neurons communicate with other neurons across these synapses.

• When an impulse reaches a synapse, the electrical signal of the presynaptic nerve is converted into a chemical signal called a NEUROTRANSMITTER.

• The neurotransmitter carries the signal across the gap and attaches to specific receptors on the postsynaptic neuron.

• The chemical signal is then converted back to an electrical signal in the postsynaptic neuron.

How a synapse works

Neurotoxins

• Neurotoxins are toxins that affect the function of the neurons.

• Botox is the most powerful toxin known to man, and is from the bacterium Clostridium botulinum. This neurotoxin prevents the release of neurotransmitters, therefore muscular contractions cannot occur.

• Tetanus is a disease caused by the bacterium Clostridium tetani.  When the bacteria enter the body, they release a neurotoxin that prevents the neurotransmitters being inhibited (stopped), therefore they continue to stimulate the contraction of the muscles

• Fly sprays work similarly to the tetanus toxin in that the chemical prevents neurotransmitters from becoming inhibited. Muscles in the insect continue to contract, leading to death by exhaustion and respiratory failure

Part 3 - Nervous System

• The Nervous system communicates between all parts of the body.

There are 2 parts of the nervous system:

• The Central Nervous System (CNS) made up of the brain and spinal cord

• The Peripheral Nervous system (PNS) made up of the nerves throughout the body.

The Central Nervous System

• The CNS receives information from all over the body from the PNS

• Processes that information

• Sends out messages telling the body how to respond

The Peripheral Nervous System

• The PNS is responsible for communicating between the internal and external environment (stimuli) to the CNS, as well as controlling your muscles and glands.

• Takes information to and from the CNS

The Brain

• The brain regulates body functions

The parts to the brain are:

• The cerebrum - controls conscious thought and voluntary movement

• The cerebellum - controls balance and coordination

• The brain stem - controls body's vital functions e.g heartbeat

The Cerebrum

• The body’s ultimate control and information processing center.

• Made up of two parts called the right and the left cerebral hemispheres.

• The right hemisphere controls the left side of your body and the left hemisphere controls the right side.

• If the damage affects the right side of the brain, the functions of the left side of the body (e.g. movement) could be affected (and vice versa).

• The cerebrum is divided into 4 sections called lobes.

Lobes of the Cerebrum

• Frontal Lobe: located at the front of the brain. Its functions include emotions, memory, movement and higher mental abilities such as reasoning and problem solving.