Unit 8 - Nervous System Flashcards
What are the four functions of the nervous system?
- sensory functions: detect sensations such as hot, cold, touch, pain, pressure
- integrative functions: gathering information, processing information, sending a response to alter/control the body
- motor functions initiate and regulate movement of body parts
- regulate secretions from glands
What is a nerve cell called?
neuron
What do neurons produce?
neurotransmitters which are chemical messengers
Where do neurotransmitters send signals to?
other neurons
What is synapses?
the short distance of travelling of a message from a neuron to a neurotransmitter to another neuron
What does the short travel of neurotransmitters allow for?
quick reaction of the system
What are the drawbacks to limited supplies of neurotransmitters?
does not allow it to sustain individual activities for a long period of time
What can the nervous system be divided into?
central nervous system (CNS)
- brain
- spinal cord
peripheral nervous system (PNS)
- cordlike nerves that link the CNS with the rest of the body
What does the PNS do?
gathers information about the external and internal environments
What does the CNS do?
receives and integrates information from PNS and initiates appropriate movements of body parts, glandular secretion or behaviour in response
What are the different parts to the neuron?
- dendrites
- central body/soma/perikaryon
- axons
- myelin sheath
What are dendrites?
short, multi-branched projections extending from the central cell body
What are the functions of the dendrites?
- receive impulses from other neurons
- conducts the impulse to the central body
What can the dendrites be referred to as?
afferent processes because they conduct impulses toward the cell body
What is the function of the central body?
- receives information or pulse brought by dendrites
- process or integrates the impulse
- sends this impulse on to the axon depending on the strength of the signal
What are the functions of the axons?
- other type of process from the neuron cell body
- conduct nerve impulses away from the cell body toward another neuron or another cell
- each neuron gives rise to only one axon which usually branches
What is the main difference in cells between dendrites and axons?
dendrites - contain granules
axons - granules are absent
How are neurons classified?
morphologically according to their number of nerve processes
What are the different types of neurons?
unipolar neurons
bipolar neurons
pseudo unipolar neurons
multipolar neurons
What is a unipolar neuron?
only one process, seen during development and can not be seen in adult vertebrate
What is a bipolar neuron?
contains two processes, one dendrite and one axon (common in sensory systems)
What is a pesudo unipolar neuron?
have their single dendrite and axon fused so as to give the appearance of a single process
What is a multipolar neuron?
have a number of dendrites in addition to their single axon, most neurons are multipolar in nature
What is the myelin sheath and what is it made out of?
- sheath of fatty substance that covers the axons
- is made of the cell membranes of specialized glial cells called oligodendrocytes in the brain and the spinal cord and schwann cells in the nerves outside of the brain and spinal cord
What are the two types of glial cells that a myelin sheath can be made out of?
oligodendrocytes - brain and spinal cord
schwann cells - nerves outside
How many oligodendrocytes take up the axon?
multiple oligodendrocytes, lined up end to end to cover the entire length of the axon
What are the gaps in the myelin sheath called
nodes of ranvier
What do te oligodendrocytes and the nodes of ravier do?
work together to enhance the speed of conduction of nerve impulses along the axon
What do neuroglia cells do?
provide mechanical support, protection and nutrients to the nerve cells
What are astrocytes?
a type of neuroglia cells, they are cells with long projections that surround the blood vessels within the CNS
What are the functions of astrocytes?
contributes to the blood-brain barrier which prevents the brain of blood toxic substances in the blood, and harmful compounds from the brain to the bloodstream
What are microglia?
a type of neuroglia, the smallest, act as a immune cell of the CNS
What is the function of microglia?
fight off and phagocytize viruses, bacteria, and other foreign invaders, they remove cellular debris to facilitate wound repair
What are ependymal cells?
a type of neuroglia, line all the cavities within CNS
What does the CNS deal with?
central or cranial/caudal axis of the body
What are the two types of PNS nerves?
cranial nerves: PNS nerves that originate from the brain
spinal nerves: PNS nerves that originate from the spinal cord
What are afferent vs efferent nerves?
afferent nerves: carries nerve impulses towards CNS
- includes sensory nerves which carry sensations from sensory receptors in the skin and other parts of body
efferent nerves: carries nerve impulses away from the CNS towards muscles and other organs
- called motor nerves as will cause skeletal muscle contractions
What is the autonomic nervous system?
sensory neurons - afferent (carry towards CNS)
- includes involuntary nerve function
motor neurons - efferent (carry away from CNS)
- includes contraction of intestines, change in heart rate in response to a threat, stimulate secretions of digestive juices etc.
What is the somatic nervous system?
sensory neurons - afferent (carry towards CNS)
- includes conscious or voluntary control of skeletal muscles
motor neurons- efferent (carry away from CNS)
- includes impulses sent from receptors in the muscle, skin, eye and ear to CNS which are consciously perceived by the brain
What is happening inside/outside the cell at resting state of the neuron?
Inside: higher concentration of potassium ions, lower concentration of sodium ions, presence of negative charges inside (e.g. proteins, Cl-)
Outside: higher concentration of sodium ions, lower concentration of potassium ions, presence of negative charges outside
When is the cell membrane of a neuron polarized?
keeping the sodium on the outside and the potassium on the inside, the cellular membrane separating the two is said to be polarized, it has two distinct poles of ions on either side of the membrane
What does the sodium-potassium pump do in the resting state of the neuron?
- specialized structure to help maintain cell resting state
- pumps Na2+ to the outside and pumps K+ to the inside
- pumps against the concentration gradient