Peripheral Nervous System Flashcards
Learn about the PNS
what does the Peripharal nervous system (PNS) do?
co-ordinates the transmission and receiving of Impulses, to and from the central nervous system (CNS)
What is does a Neurone do
?
Co-ordinates the transmission and
receiving of impulses, to and from the
central nervous system.
What does the peripheral Nervous system consist of?
31 pairs of spinal nerves, 12 pairs of cranial nerves, the autonomic nervous system.
What is a neurone
Highly modified cell, capable of initiating, relaying and redirecting electrical impulses.
How does a neuron initiate and relay?
By converting chemical energy into electrical energy
What are the functions of a neurone
Controlling muscle activity, regulating glands, supporting and protecting the nervous system.
What is an Dendrite?
an extension of the cell body that carries impulses towards the cell body.
what is an axon?
an extension of the cell body that carries impulses away from the cell body.
what is the node of Ranvier?
narrow , non-insulated part of the neurone that boosts the strength of the impulses as it passes along.
What do Schwann cells do?
produce and secrete neurilemma, which forms the outer layer of the neuron myelin sheath.
What do Boutons do?
They are small end bulbs from which chemical transmitters are released and found in the Axon terminal.
how does a neurone transmit an impulse?
signal transmitted –> Myelin sheath covering the axon allows ions to leak through. potassium and sodium ions change places creating an electrical signal that travels along the membrane. when impulses reach the synapse the vesicles inside discharge chemical transmitters which transmit the impulse next to the neuron.
what does acetycholine do?
binds to sodium and potassium which depolarizes the membrane and a nerve impulse is generated, causing muscle fibres to contract.
What happens to chemical transmitters if the body goes into alkalosis?
PH of 7.8 can cause cerebral convulsions.
What happens if the body goes into acidosis?
PH below 6.5 will depress neural activity causing a coma.
What are most of the nerves involved in the PNS composed of?
Sensory nerves fibres that are afferent (bearing or conducting inwards) and motor nerve fibres that are efferent (conducting outwards from a part or organ)
what are the efferent nerves divided into?
Somatic (Voluntary)
Autonomic (Involuntary)
What are afferent neurones ?
they are sensory.
- usually unipolar
-they convey information from receptors in the periphery
- skin and sense organs to the CNS or the connector neurons of the reflex arc
how many spinal nerves are there?
31 pairs of spinal nerves.
-8 cervical
-12 thoracic
-5 lumbar
-5 sacral
-1 coccygeal
What is a reflex?
a motor response with no intervention from the brain.
Reflex actions are specific responses to a
sensory stimulus with no conscious control
What 5 things are required for a reflex action?
A receptor
A sensory neurone
An associated neurone
A motor neurone
An effector
what are the types of reflexes?
Spinal Reflex:
Sensory impulse for quick action
Cortical Reflex:
Overrides spinal reflex under conscious control
Coordinating Reflex:
Modifies movement and coordinates
Autonomic Reflex:
Immediate reaction to situations
Over rules conscious decisions
how does the autonomic nervous system work?
The effects of autonomic control are mainly
stimulation or depression of glandular secretions
and contraction of cardiac and smooth muscle
tissue
What are examples of what the autonomic nervous system controls?
Rate and force of the heartbeat
Secretions of glands of the alimentary tract
Vasoconstriction or dilation
Change in the size of the pupils of the eyes
what is sympathetic?
Fight or Flight
Adrenaline
&
Noradrenaline
what is parasympathetic?
Sleep, rest and
digestion
Acetylcholine
