L18 The Nervous System And Its Cells Flashcards
What is the Central Nervous System?
Sensory and motor signals are combined and coordinated, consciousness, memory, and emotion manifests.
Includes: brain and spinal cord
What is the Peripheral Nervous System
- All the nervous tissue outside the brain and spinal cord, like sensory receptors and peripheral nerves.
- Communication between CNS and body
What does the peripheral nervous system divide into?
1) Afferent division
2) Efferent division
What is Afferent division?
- Comunicates incoming sensory signals to CNS
- Composed of sensory neurons
What do sensory neurons monitor?
Somatic and visceral stimuli (External and Internal)
What is Efferent Division?
- Communicates outgoing motor signals
- Composed of motor neurons
What signals do motor neurons send?
Send somatic signals and autonomic signals
What does the Autonomic nervous system do?
Controls involuntary responses
What does the Somatic nervous system do
Controls voluntary movement
Which effectors receive somatic signals?
To voluntary effectors (skeletal muscle)
Which effectors receive autonomic signals?
Involuntary effectors (smooth, cardiac muscles, and glands)
What are autonomic signals divided into?
Signals
1) Sympathetic (fight or flight - mobilises body systems)
2) Parasympathetic (rest and digest - conserves energy)
What are the major functions of the nervous system?
1) Monitor internal and external environments
2) Integrate(Combine) sensory information
3) Coordinate responses from all organ systems
What are the major cell types of the nervous system
1) Neurons
2) Neuroglial cells
What are neurons responsible for?
Neurons are building blocks of the nervous system. They transmit electrical signals (action potentials) to communicate and coordinate body functions.
What are the 3 major cellular structures of the neurons?
1) Cell body
2) Dendrites
3) Axon(s)
What does the cell body contain?
- Major organelles
- Rough ER (Nissl bodies)
- Grey matter (because of rough ER)
What is the role of dendrites?
Monitor external and internal sensory stimuli
What is within the Axons?
- Axon hillock (absence of Nissl bodies)
- Collaterals (branching)
- Axon termini (ends of branching and synapse onto other neurons or effectors)
What is the direction of the action potential ?
1) Dendrites
2) Cell body
3) Axon
What happens to the centrioles of neurons?
Disappear at around 1 y.o, making cell division impossible afterwards
What do we call the axon plasma membrane?
Axolemma
What do we call the cytoplasm of the axon?
Axoplasm (does not apply to dendrites or cell body)
What are the 3 shapes of neurons?
1) Multipolar
2) Unipolar
3) Bipolar
What are multipolar neurons?
- Found in the CNS
- Multiple projections (dendrites) leave cell body
- Their Axons leave brain or spinal cord and can connect to other neurons or effectors
What are Unipolar neurons?
- Sensory neurons with one projection
- Dendrites detect stimuli
- Axon sends signals to CNS
- Single projection leaves cell body
What are Bipolar neurons?
- Rare
- Eyes, ears, and olfactory bulbs
- One dendrite and one axon connected to the cell body
What is the characteristics of sensory neurons by their function?
- Afferent
- Collect sensory info & transport them to CNS
- Unipolar and rarely bipolar
What is the classification of motor neurons and there function?
- Efferent
- Transmit info to PNS from CNS
- Multipolar
What is the characteristics of association or interneurons and there function?
- Connect neurons in CNS
- Multipolar
What are the characteristics of afferent neurons?
- Receive sensory info
- Receive external and internal environment info
- Carry signals towards brain or spinal cord to synapse on neurons in CNS
- Unipolar
- Cell bodies cluster into ganglia
Characterstics of efferent neurons
- Synapse onto effector cells (muscles and glands)
- Carry info away from brain and spinal cord
- Multipolar
- Cell bodies clustered into grey matter of CNS
- Axons exit into PNS
What are the characteristics of interneurons?
- Most abundant neurons
- Found in CNS only
- Connect neurons to each other (sensory and motor)
- Complex stimuli transmited along more interneurons to manifest the brains higher functions
What are the different type of neuroglia and which system are they in?
CNS
- Astrocytes
- Oligodendrocytes
- Microglia
- Ependymal cells
PNS
- Satellite cells
- Schwan cells
What is the organization of cells in the nervous tissue?
In Gray matter
- Cell bodies
- Dendrites
- Axons of neurons
In White matter
- Axons of neurons
Neuroglia present in both matter types
What are the characteristics of the astrocytes neuroglia? (CNS)
- Largest and most numerous in CNS
- Create 3D framework in nervous tissue
- Nervous tissue repair
- Maintain blood brain barrier (BBB) by wrapping their processes around the capillaries
What does BBB do?
- Filters blood to limit what reaches brain and spinal cord
- Creates unique interstitial fluid in nervous tissue
What are the characteristics of the oligodendrocytes neuroglia? (CNS)
- Myelin sheath (wrap their plasma membranes around axons)
- Each oligodendrocyte wraps around multiple axons, forming myelin for several neurons.
What does myelin do?
- Lipid rich
- Insulates axons to speed up electrical transmission by preventing ion loss
- Makes up most of white matter
What are the characteristics of microglia neuroglia? (CNS)
- Smallest and least common
- Phagocytic
- Protect against chemical and infectious agents by englufing wastes, pathogens, and debris
Why are microglia important?
- CNS is an immune privileged zone, inflammation not included
- inflammation in the CNS causes swelling, but the brain and spinal cord are enclosed in bone with no room to expand.
What are the characteristics of the ependymal cells? neuroglia CNS
- Line cavities that carry cerebrospinal fluid
Ex: central canal of the spinal cord and ventricles (chambers of the brain - Create, monitor and circulate cerebrospinal fluid via cilia
Cancer… What types of tumours can we find in the CNS?
1) Primary tumours
2) Secondary CNS tumours
What is a primary tumour?
- Tumours originating in CNS
- In adults: abnormal neuroglial cell division
Why? because neurons cease cell division at ~1y.o - Found typically in young children
What is secondary CNS tumours?
- Metastasis of other cancers
- Cell appear and behave as those of the parent tissue
What are the characteristics of Satellite cells neuroglia? (PNS)
- Surround & support cell bodies of unipolar neurons in PNS (found in ganglia)
- Mirror function of astrocytes
What are the characteristics of Schwann cells neuroglia? PNS
- Cover all axons in PNS (mirroring the oligodendrocytes)
- Surrounds ONLY short stretch of axon
- Along unmyelinated axons wrap their cell membranes around one or more axons
- Along myelinated axons myelin sheat occurs in many layers
