Lecture 3 - Nervous System 1 Flashcards
What is homeostasis?
The state of stability brought by the body’s tendency to stay in equilibrium.
What are the two major systems of the body that integrate and generate appropriate responses to maintain homeostasis?
Nervous System
Endocrine System
What are the three basic functions are performed by nervous systems?
1) Takes input from sensory receptors
2) Performs integration at the CNS
3) produces a signal for motor output
What are receptors and where are they found.
Receptors are the parts that would detect changes in the internal or external environmental for the body to react accordingly. Eyes, ears, tongue, tactile?
Give examples of sensory input (both internal and external)
pH, temperature, light, taste, haptic
Where is sensory information integrated?
In the Central Nervous System (Brain and Spinal Cord)
What is the response?
The electrical/chemical signal that is sent by the CNS after integration to invoke the necessary motor action to be done by organs.
What is the central nervous system composed of?
Brain & Spinal Cord
What is the function of the CNS?
Takes the input signal and then creates the output signal based on experiences, reflexes and current conditions
What is the peripheral nervous system composed of?
The surrounding nerves around the CNS are composed of ganglia, cranial nerves and spinal nerves.
What is the function of PNS?
To send signals to the CNS and also conduct information between CNS and the organs.
Define Ganglia?
Collection of nerve bodies
Cranial nerves
Facial nerves found near the brain
Spinal nerves
Nerves found near the spinal cord
How many cranial nerves are there?
N/A
What are the two subdivisions of the peripheral nervous system and what are their functions?
The afferent (sensory) division = collects signals from the receptors to send to the CNS The efferent (motor) division = sends signals from the CNS to the organs to perform output
What are the two subdivisions of the motor division?
1) Autonomic nervous system
2) Somatic Nervous System
What are the two subdivisions of the autonomic nervous system and what are their functions?
1) Parasympathetic division (involved in “rest and digest” system)
2) Sympathetic division (fight or flight action)
What are the two types of nervous tissue? Which is involved with transmitting signals and which can divide, which are far more numerous?
1) Neurons that transmit signals
2) Neuroglia that divides. Outnumbers neurons 10:1
Define Oligodendrocytes?
forms myelin sheath to insulate the axons. Found in CNS.
Define Microglia?
Phagocytes to protect CNS cells. (engulfs invaders)
Define Astrocytes?
functions in exchange of nutrients in the capillaries and repair the nervous system in CNS
Define Ependymal?
Cells that line the cerebral spinal fluid (CSF), excreted by the choroid plexus (types of ependymal cells)
Define Schwaan
Produce the myelin sheath around a single axon
Define Satellite?
thought to have the same function as astrocytes
Generally describe the characteristics of a neuron?
Functional unit of the NS must serve you for life. High metabolic rate and cannot stay alive for long without oxygen.
Function: generation and conduction of nerve impulse
What is in the structure of a neuron?
1) Dandrites – short and diffused branches. Receptive (input) regions. Conveys information to the soma. Messages are in electric signals called graded potential.
2) Soma – cell body where nucleus is located. Contains usual organelles except centrioles.
3) Axon – a single long extension
4) Axon terminal branched at the tip
What direction the impulse travels?
From dandrites to the axon terminal
Define Nuclei, Ganglia, Tract, Nerve
Nuclei: clusters of cell bodies inside the CNS
Ganglia: clusters of cell bodies in the PNS
Tract: Axons in the CNS
Nerve: Axons in the PNS
What is the synapse?
…
What is the myelin sheath?
Layering of fatty substance (myelin) and proteins to insulate nerves
Which cells form the myelin sheaths in the CNS and PNS?
Schwaan cells
Describe the formation of the myelin sheath by Schwann cells?
Rolling of layers by Schwaan cells
What is the neurilemma?
The myelin sheath that is the outermost of the Schawaan cell that covers the nucleus
What is the function of the myelin sheath
- Protects the axon
- Electrically insulates the axon so that ions cannot enter/exit the axon
- Speeds up nerve transmission
What is a node of Ranvier and why is it necessary
Gaps in between Schwann cells on the axon. Necessary because there would be no current and action potentials would only occur because of such nodes.
What is grey matter and white matter
White matter: nervous tissue that consist of myelinated axons (insulated by myelin sheath)
Grey matter: contains cell bodies, unmyelinated axons, axon terminals.
Know the structural classification of neurons (multipolar, bipolar and unipolar), which is most common, which is found only in some of the special sense organs –the eye, which is composed of a peripheral process and a central process and compose the cell type found in the PNS ganglia
1) Multipolar: very common. All motor and association neurons are this type. Found in CNS.
2) Bipolar: rare. Found only in some special receptor organs (the eye)
3) Unipolar: composed of a peripheral process and a central process and compose the cell types found in PNS ganglia
Know the functional classification of neurons, which has cell bodies located in the sensory ganglia outside the CNS, which make up over 99% of the neurons of the body and which has a cell body in the CNS
1) Sensory neurons (sensory ganglia)
2) Interneurons: makes up 99% of neurons
3) Motor neurons: cell body in CNS
