Nervous System Flashcards
What do multicellular organisms need?
Communication systems: body works as a whole and not as individual cells or organs.
What are the two communication systems?
The nervous system and hormonal system.
What does the nervous system do?
- sends messages using nerve cells or neurons, which produce quick short response: nerve message/impulse is electrical
- specialised organs called the brain and spinal cord.
What does the hormonal system produce?
Chemicals messages in the form of hormones: system is slower than nervous but the response is longer-lasting.
What does the central nervous system (CNS) consist of?
Brain and spinal cord.
In the mammalian system, what is the CNS system linked to?
The peripheral nervous system (PNS): neurons which connect the CNS to the whole body.
What are the type of neurons?
- sensory neurons: connect receptors: eyes, ears, skin which detect changes in the environment: stimuli, with central nervous system
- motor neurons connect the central nervous system to effectors: muscles which produce a response.
What are produced by glands?
Hormones that are chemicals: transported in blood: all organs of body are exposed to them but only affect target cells.
Hormonal systems: slower and longer examples:
- insulin is produced in pancreas: acts on liver, muscles and body cells take up glucose from blood
- oestrogen produced by the ovaries: sex hormone that controls development of adult female body at puberty and menstrual cycle.
What are neurons?
Cells are specialised for carrying nerve impulses: so they’re long.
What do neurons consist of?
Cell body, nucleus and a long axon.
What are the branches on the cell body called?
Dendrites: receive inputs from other cells (receptors and nerves) and conduct impulses towards cell body.
What is the axon?
Long extension of cytoplasm in a neuron: communicates with CNS or effector.
What is the myelin sheath?
Some axons are covered with an insulating fatty sheath.
What is the speed of the nerve impulse is affected?
- temperature: speed increases, faster in warm-blooded animals than cold-blooded animals
- diameter of axon: wider the axon, quicker the response
- myelin sheath: plus insulating neuron from neighbouring cells, presence of myelin sheath speeds up the nerve impulse: jump from gap to gap: travels faster.
