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level: 15.1 Neurones and nervous coordination

Questions and Answers List

level questions: 15.1 Neurones and nervous coordination

QuestionAnswer
The two main functions of coordination in animals- The nervous system - The hormonal system
The nervous system- Uses nerve cells to pass electrical impulses - Stimulate target cells by secreting neurotrans. directly on to them
The hormonal system- Produces hormones that are transported in the blood plasma to target cells - Target cells have specific receptors on cell-surface membrane - Change in the conc. of hormones stimulates them
Hormonal system Vs nervous system (HORMONAL SYSTEM)- Communication by chemicals, hormones - Transmission by the blood system - Transmission slow - Response slow - Response widespread - Response long-lasting - Effect may be permanent + irreversible
Hormonal system Vs nervous system (NERVOUS SYSTEM)- Communication by nervous impulses - Transmission by neurons - Transmission rapid - Response rapid - Response localised - Response short-lived - Effect is usually temporary + reversible
Neurones meaning- Specialised nerve cells - Adapted to rapidly carry electrochemical changes called nerve impulses from 1 part of the body to another
What motor neurones are made up of in mammals- A Cell body - Dentrons, dendrites - An axon - Schwann cells - A myelin sheath - Nodes of Ranvier
A cell body- Contains all the usual cell organelles - Nucleus + rough endoplasmic reticulum - Associated with the production of proteins + neurotransmitters
Dentrons, dendrites- Extensions of the cell body which subdivide into smaller branched fibres, dendrites - Carry nerve impulses towards the cell body
An axon- Single fibre that carries nerve impulses away from the cell body
Schwann cells- Surround axon, wrap themselves around it many times - Protecting it + providing electrical insulation - Carry out phagocytosis (the removal of cell debris), play part in nerve regeneration
A myelin sheath- Forms a covering to the axon - Made up of membranes of the Schwann cells - These membranes are rich in a lipid, myelin - Neurones with a myelin sheath are called myelinated neurons
Nodes of Ranvier- Constriction between adjacent Schwann cells - Where there is no myelin sheath - Constrictions are 2-3 micrometers long - Occur every 1-3 mm in humans
Different types of neurones- Sensory neurones - Motor neurones - Intermediate or relay neurones
Sensory neurones function- Transmit nerve impulses from a receptor to motor neurone - Have 1 dendron that is often very long - Carries impulse towards the cell body - 1 axon that carries it away from the cell body
Motor neurones function- Transmits nerve impulses from a relay neurone to an effector - Have long axon, many short dendrites
Intermediate or relay neurones function- Transmit impulse between neurones - Like from sensory to motor neurones