The Nervous System and Responding to Stimuli and Reflexes Flashcards
How do organisms respond to their environment to survive?
-they respond to changes in their EXTERNAL environment eg by avoiding places that are too hot or too cold.
What is the role of RECEPTORS and EFFECTORS?
RECEPTORS detect STIMULI and EFFECTORS produce a RESPONSE.
What are RECEPTORS?
RECEPTORS in the sense organs are a group of CELLS that detect EXTERNAL STIMULI.
Give 5 examples of sense organs.
Eyes, ears, nose, tongue and skin.
Give an example of RECEPTOR cells and their function.
Rod and cone cells in the eye detect changes in light.
Give an example of EFFECTOR cells.
They include muscle cells and cells found in glands eg the pancreas.
Give an example of a response that is produced by EFFECTOR cells
EFFECTORS respond in different ways - muscle cells CONTRACT and glands SECRETE HORMONES.
How do RECEPTORS communicate with EFFECTORS?
RECEPTORS communicate with EFFECTORS via the NERVOUS SYSTEM, the HORMONAL SYSTEM or sometimes both.
What is the nervous system made up of?
neurones (nerve cells)
What are the 3 main types of neurones?
Sensory, relay and motor neurones
What does the central nervous system consist of?
BRAIN and SPINAL CORD only
What do RECEPTORS do when they detect a stimulus?
They send electrical impulses along SENSORY NEURONES to the CNS
What does the CNS do?
It’s job is to co ordinate responses.
What do EFFECTORS do when they get a message from a MOTOR NEURONE?
They respond accordingly
What do co ordinated responses always need?
STIMULUS, RECEPTOR and EFFECTOR
How is the nervous system able to bring about very rapid responses
Because neurones transmit information using high speed electrical impulses
What is the connection between two neurones called?
A SYNAPSE (a gap)
How does a SYNAPSE work?
The nerve signal is transferred by CHEMICALS called NEUROTRANSMITTERS which diffuse across the gap. These CHEMICALS then set off a new ELECTRICAL signal in the next neurone
Why do organisms respond to changes in their environment?
It increases their chance of survival
What is a stimulus?
A change in the INTERNAL or EXTERNAL environment
How are STIMULI detected?
By the RECEPTOR CELLS
Give two types of EFFECTOR and how they respond
MUSCLE contracts or GLAND secretes a hormone
What is the purpose of a reflex action?
They are automatic responses not a conscious decision. They reduce the chance of being injured
Describe how a reflex arc works.
Candle burns finger, stimulation of the pain RECEPTOR,
Impulses travels along the SENSORY NEURONE, impulses are passed long a RELAY NEURONE, VIA a SYNAPSE, impulse sent along MOTOR NEURONE via a synapse, impulse reach muscle, it CONTRACTS, and moves hand away from candle.
