THE PERIPHERAL NERVOUS SYSTEM Flashcards
(63 cards)
What are the nerves of the peripheral nervous system? (2)
consist of nerve fibres (axons and dendrons) arranged in bundles, protected by connective tissue sheaths.
what do the peripheral nervous system nerves consist of? (2)
-sensory neurones carrying impulses to the CNS
-motor neurones carrying impulses to muscles and glands
What is the somatic nervous system? (1)
the system of motor neurones carrying impulses to muscles controlling voluntary (conscious) actions
what is the autonomic nervous system? (1)
the network of motor neurones carrying impulses to the heart, smooth muscle and glands controlling involuntary (unconscious actions)
what are the parts of the ANS? (2)
-the sympathetic nervous system
-the parasympathetic nervous system
what are the roles of the sympathetic nervous system? (9)
-more active in times of stress to produce ‘fight or flight’ responses
-at their junctions with effector tissues the neurones release noradrenaline
what are the roles of the parasympathetic nervous system? (2)
-concerned with conservation of energy and the replacement of body reserves
-at their junctions with effector tissues the neurones release acetylcholine
what are the response of the sympathetic nervous system? (6)
-increases ventilation
-causes widening (ventilation) of the tissues
-has no effect on the tear glands
-has no effect on the salivary glands
-slows peristalsis
-constricts bladder sphincter muscles
what are the responses of the parasympathetic system? (6)
-decreases ventilation rate
-causes constriction (narrowing) of the pupils
-causes the secretion of tears
-cause the secretion of saliva
-accelerates peristalsis
-causes relaxation of the sphincter muscles of the bladder and contraction of the muscular wall of the bladder
what are the different types of neurones? (3)
-motor neurones
-interneurons
-sensory neurones
describe the structure of a motor neurone. (1)
have many dendrites which bring impulses towards the cell body, and a single long, axon, which carries impulses away from the cell body.
describe the structure of an interneuron. (1)
have numerous short fibres
describe the structure of sensory neurones. (1)
have a single long dendron, which brings impulses towards the cell body, and a single long axon, which carries impulses away
what surrounds neurones? (1)
different types of supporting cells called neuroglia cells
what is the most common surrounding cells? (1)
they care called schwann cells, these wrap themselves around the fibres, forming a structure called a myelin sheath, the junction is called a node of ranvier.
What is a node of ranvier? (1)
A small gap in the myelin sheath surrounding an axon.
What is an impulse? (1)
The impulse is not an electrical current, it is a momentary reversal in electrical difference in the membrane. It is a change in the amounts of positively and negatively charged ions between the inside and outside of the membrane of a nerve fibre.
What is an impulse transmitted? (1)
This reversal travels from one end of the neurone to the other in a fraction of a second, between conduction of cone impulse and the next, the neurone is said to be resting.
What occurs during a resting interval? (1)
The membrane of a neurone actively creates and maintains an electrical potential difference between the inside and the outside of the fibre.
What two processes produce the resting potential difference across the neurone membrane? (2)
-active transport
-facilitated diffusion
Describe the active transport process that produces the resting potential difference. (1)
Active transport of potassium ions in across the membrane, and of sodium ions out across the membrane. The ions are transported by a Na+ - K+ pump, with transfer of energy from ATP. so potassium and sodium ions gradually concentrate on opposite sides of the membrane, this makes no change to the potential difference across the membrane.
Describe the facilitated diffusion process to produce the resting potential difference. (1)
Facilitated diffusion of K+ ions out and Na+ ions back in, the membrane is more permeable to K+ions flowing out than to Na+ ions returning. This causes the tissue fluid outside the neurone to contain many more positive ions than are present in the cytoplasm inside. As a result, the inside becomes more and more negatively charged compared with the outside, the resting neurone is said to be polarised.
What is an impulse triggered by? (1)
An impulse, or action potential is triggered by a stimulus received at a receptor cell or sensitive nerve ending. The energy transferred by a stimulus causes a temporary and local reversal of the resting potential, the result is that the membrane is temporarily depolarised.
