B13

IGCSE biology: coordination, response, and hormones

What is stimuli?

Changes in organism’s environment

What are receptors?

Specialised cells that detect stimuli

What are effectors?

Muscles and glands that respond to stimuli

What does the central nervous system do? 

Coordinates the electrical impulses travelling through the neurones to regulate body functions

What does the endocrine system do?

Uses glands to secrete hormones, which are chemical messengers that travel through the bloodstream to target specific organs and tissues, controlling functions like growth, metabolism, and reproduction

What are neurons?

Electrical impulses travel through nerve cells

What are the neurons adaptations?

Long, thin fibres of cytoplasm to carry electrical signals quickly

What are dendrites? 

Shorter fibers that pick up electrical signals (nerve impulses) from nearby neurons. 

What is the axon?

The longest fiber that connects a neuron to another neuron after the signal from the dendrites passes to the cell body, then along the axon.

What is the myelin sheath? 

What insulates axons, allowing the impulses to travel faster 

What type of neuron is this?

Motor (effector) neurone

What does the motor neuron do?

Carries electrical impulses from the central nervous system (CNS), which is the brain and spinal cord, to effectors like muscles or glands

What type of neuron is this?

Sensory neuron

What does the sensory neuron do?

Transmits electrical impulses (nerve impulses) from a receptor in a sense organ to the central nervous system (CNS), which includes the brain and spinal cord.

What type of neuron is this?

Relay (connector) neuron

What does the relay neuron do?

Acts as a link, passing nerve impulses from a sensory neuron to a motor neuron, typically within the central nervous system (CNS) like the spinal cord or brain

What is CNS?

Stands for Central Nervous System, and it coordinates the electrical impulses traveling through the neurons to regulate body functions. It is the brain and spinal chord

What is PNS?

Stands for Peripheral Nervous System, and it consists of all the nerves outside the brain and spinal cord. Its main function is to carry nerve impulses between the CNS and the rest of the body, allowing it to sense the environment and respond to stimuli. It is the nerves and receptors

What is the relfex arc?

Instead of sending electrical impulses directly to the brain, they are sent to the spinal cord (Central Nervous System) to reduce reaction time. They are fast, automatic and involuntary actions

Use the example of touching a flame and explain what happens

If you touch a flame, impulse is picked up by a sensory neurone in your finger which then carries the impulses along its axon to the spinal cord. In the spinal cord, the impulse is passed to a relay neurone. Impulse passes to a motor neurone and then to an effector muscle so that the hand is pulled away

What is synapses? 

The small gap between neurons (synaptic gap). The ends of two neurones and the gap is called a synapse. 

What is a hormone?

A chemical substance produced by a gland and carried by the blood, which alters the activity of one or more target organs

What is the hypothalamus? 

Control center of hormones

What is the hormone produced and functions of the adrenaline glands?

It produces adrenaline and prepares the body for figh or flight

What is the hormone produced and functions of the pancreas?

It produces insulin (glucose) and it reduces blood gluose levels

What is the hormone produced and functions of the ovaries?

It produces estrogen, and it develops female secondary sexual traits & controls menstrual cycle

What is the hormone produced and functions of the testis?

It produces testosterone and it develops male secondary sexual traits

When adrenaline is relased into the body, explain the effect it has on the heart 

More oxygen and glucose to brain and muscles

When adrenaline is relased into the body, explain the effect it has on the breathing muscle 

More oxygen to brain and muscles

When adrenaline is relased into the body, explain the effect it has on the eyes 

More light enters so sharper eyesight 

When adrenaline is relased into the body, explain the effect it has on the liver  

More glucose is released, meaning more energy for muscles 

Compare the communication method between the nervous and endocrine system

Nervous system: nerve —> neurotransmitter

Endocrine system: glands —> hormones

Compare the target between the nervous and endocrine system

Nervous system: nerves, msucles, glands

Endocrine system: any celll with hormone receptor

Compare the respone time between the nervous and endocrine system

Nervous system: rapid (seconds/milliseconds)

Endocrine system: slower (seconds/minutes)

Compare the range of effect between the nervous and endocrine system

Nervous system: short-term (milliseconds)

Endocrine system: lower-term (mins/days/weeks)

Compare the duration of effects between the nervous and endocrine system

Nervous system: stops once the stimulus is removed

Endocrine system: may continue after stimulus is removed