Chapter 15 - Nervous Coordination and Muscles Flashcards
Characteristics of the nervous system
Nerve cells transmit electrical impulses along their length
Impulse stimulates the secretion of neurotransmitters onto target cells
Short-lived, affect a small area
Characteristics of the hormonal system
Hormones transported in blood plasma to target cells
Slow, widespread, long-lasting effect
What is the cell body?
Contains organelles, produces neurotransmitters
What are dendrons?
Extensions of cell body
Divide into dendrites
Carry impulse TO cell body
What is an axon?
A long fibre that carries impulses FROM the cell body
Function of Schwann cells
Electrical insulation
Function of myelin sheath
Covers the axon
What are the nodes of Ranvier?
No myelin sheath
How does the nervous system control actions?
It uses nerve cells to pass electrical impulses along their length and stimulate target cells by secreting neurotransmitters.
What is the main benefit of control via the nervous system?
The response is very quick, reflex action
What is the main potential drawback of control via the nervous system?
The response is short lived and restricted to one part of the body.
How does the hormonal system have control over the body?
It produces hormones which are transported in the blood plasma to their target cells, which have specific receptors on the cell surface membrane, sensitive to hormone concentration.
What are the main parts of a nerve cell?
A cell body
Dendrons
An axon
Schwann cells//myelin sheath
What does the cell body contain?
It contains all the usual cell organelles, including a nucleus and large amounts of rough endoplasmic reticulum, associated with the productions of proteins and neurotransmitters.
What are the dendrons?
Extensions of the cell body which subdivide into smaller branched fibres called dendrites that carry nerve impulses towards the cell body.
What is the axon?
A single long fibre that carries nerve impulses away from the cell body
What do the Schwann cells do?
The surround the axon, protecting it and providing electrical insulation. They also carry out phagocytosis and play a part in nerve regeneration. They wrap around the axon many times so the layers build up.
What is the structure and function of the myelin sheath?
Covers the axon and is made up of the membranes of the Schwann cells. Membranes are rich in the lipid myelin.
What is the structure and function of the nodes of Ranvier?
Constrictions between adjacent Schwann cells where there is no myelin sheath. 2-3 micro metres long and occurs every 1-3mm in humans.
Describe the structure and function of Sensory neurones:
Transmit nerve impulses from a receptor to an intermediate or motor neurone. One dendron that is often very long, carries nerve impulse towards cell body and one axon carries away from cell body
What is the structure and function of motor neurones?
Transmit nerve impulses from an intermediate or ready neurone to an effector, such as a gland or muscle. Motor neurones have a long axon and many short dendrites.
What is the structure and function of intermediate neurones?
Transmit impulses between neurones. For example from sensory to motor neurones. Have numerous short processes.
What can a nerve impulse be described as?
A sell propagating wave of electrical activity that travels along the axon membrane
What are the two states of the axon?
Resting potential and action potential