B9.1 : Nervous system Flashcards
Stimuli
- A stimulus can be any change in the environment to which the body needs to respond.
- e.g. Changes in day light, Wind speed, Temperature, Movement, Availability of food, etc
- The stimulus/stimuli is detected by a receptor.
Receptors
- These are the cells that detect the stimuli
- e.g. taste buds detect chemicals in your food
- Receptors are found all over the body.
- They detect the change in the environment and initiate (start) a signalling process within the body.
- The signal is picked up by a neurone (nerve cell).
Effectors
- These are the organ, such as glands and muscles that bring about the responses.
- An effector is a muscle or gland that brings about an action in response to the change in the internal or external environment.
Responses
- This is the action taken by the effector muscle/gland/organ to avoid the harmful situation
- E.g. Muscles contracting e.g. biceps to remove your hand from a hot object.
- e.g. Glands secreting useful substances.
Coordination flow chart
- Stimulus > Receptor > Coordination > Effector > Response
2. Information is transmitted around the body across nerves by electrical impulses.
Human nervous system
- The role of the nervous system is to protect an organism from harm by responding to changes in the internal and external environment.
- It does this by coordinating communication between different parts of a multicellular organism.
- Consists of the central nervous system and the peripheral nervous system
What the human nervous system is made of
- Brain
- Spinal cord
- The neurones
PNS and CNS
Brain (CNS)
- The brain is one of the components (parts) of the central nervous system (CNS).
- The CNS coordinates the response of effectors.
- Effectors are muscles or glands that act in response to a change in the internal or external environment.
- Protected by the skull
Spinal Cord (CNS)
- The spinal cord is the other component (part) of the CNS.
- It is also important in coordinating the response of effectors to changes in the environment.
- Protected by the vertebral column
The neurones (PNS)
- Neurones (nerve cells) carry electrical impulses (signals) between receptors, the central nervous system (CNS) and effectors.
- Neurones make up the peripheral nervous system.
Reflex actions
- Reflex actions allow us to respond to dangerous situations rapidly and automatically by integrating and coordinating stimuli with the responses of effectors.
- Reflex actions do not involve conscious thought (i.e. they are involuntary actions).
- e.g. sneezing, blinking, dropping hot objects etc
- Involuntary actionsR
PNS
- Peripheral Nervous System
2. The peripheral nervous system refers to the nerves that connect to both the spinal cord and the brain.
CNS
- central nervous system
2. brain and spinal cord
Categories of nerves
- Part of the peripheral nervous system
- Cranial Nerves
- Spinal nerves
Cranial nerves
These link the brain with all the organs in the head and some in the thorax and abdomen
Spinal nerves
These nerves link the brain to the arms, thorax, abdomen and legs.
Nerves
Nerves are made up of nerve cells or neurones surrounded by a protective fibrous tube.
reflex arc
For reflex actions, the nervous system responds to stimuli (events or things) via a reflex arc
Parts of a reflex arc
- stimulus
- receptor
- Neurones
- Effector
- Response
- Nerve Cells
Neurones
- together they make up a nerve
3 types:
- Sensory neurone
- Relay neurone
- Motor neurone
Sensory neurone
The sensory neurone, which receives then carries the signal in the form of an electrical impulse to the central nervous system (CNS).
Relay neurone
The relay neurone (in the CNS) relays the electrical impulse from the sensory neurone to the appropriate motor neurone.
Motor neurone
The motor neurone is another type of nerve cell that carries the electrical impulse from the CNS to an effector.
