Ch 12 Nervous Tissue Flashcards
What are the two major anatomical divisions of the nervous system?
- Central Nervous System (CNS)
- Peripheral Nervous System (PNS)
What does the Central Nervous System (CNS) consist of?
Brain and spinal cord
What does the Peripheral Nervous System (PNS) include?
Nerves in anything not the brain or spinal cord, such as arms, legs, torso
What are the two types of afferent neurons in the PNS?
- Somatic Afferent neurons
- Visceral Afferent neurons
What is the function of Somatic Afferent neurons?
Carries sensory information to the CNS from the skin and muscles
What do Visceral Afferent neurons convey?
Information to the CNS from organs such as stomach, muscle, cardiac muscle, and structures
What are the two divisions of the peripheral nervous system?
- Sensory (Afferent) Division
- Motor (Efferent) Division
What does the Motor (Efferent) Division do?
Carries impulses from the CNS to effectors
What structures does the Autonomic Nervous System control?
Glands, cardiac muscle, smooth muscle, and involuntary structures
What is the role of the Autonomic Nervous System?
Includes reflexes and carries impulses to involuntary structures
What are the two divisions of the Autonomic Nervous System?
- Sympathetic Division
- Parasympathetic Division
What is the function of the Sympathetic Division?
Speeds up effectors
What is the function of the Parasympathetic Division?
Slows down effectors
Fill in the blank: The __________ is the division of the nervous system that includes voluntary structures.
Somatic Efferent Division
What is the Enteric Plexus?
Nerves in the walls of the digestive organs
What are the three functions of the nervous system
Sensory
Integration
Motor
What is sensory function of the nervous system
Has specialized cells called receptors that detect stimulation
What is the integration function of the nervous system
Determines an appropriate response( in the brain)
What is the motor function of the nervous system
Stimulates effectors
What are effectors
Anything that responds to a nerve?
Pertaining to neuron function what is excitability or irritability
The ability to respond to a nerve impulse
Pertaining to neuron functions, what is action potential
The ability of muscle cells to create an electrical current
Pertaining to the function of neurons what is secretion
The ability of a neuron to release a product
The product is a neurotransmitter
What is the Soma of a neuron
The main part of the cell (contains the nucleus)
What are neurofibrils?
Clusters of intermediate filaments made of protein
Their job is to maintain the cell shape
What are nissl bodies?
Clumps of rough ER in the cytoplasm
What do nissl bodies look like when they’re mature
They lack centrioles
So no spindles and no mitosis
What are inclusions?
Storage units in a neuron
Examples lipofuscin which is a waste product of autophagy meaning replacing worn out organelles
What are dendrites
Numerous and branched their job is to receive stimulation
What are somatic spines?
Extensions from the cell membrane that allow the cells to communicate
What is an axon hillock
Where the axon attaches to the Soma?
Triangle shaped
Single structure
What are axons
A single structure that is branched at the ends. The side branches that leave a 90° angles are called collateral branches. The branches at the end are terminal branches
What are terminal branches
Branches at the end of an axon
What is a synapse
Where two neurons meet but do not touch
What is axonal transport?
Two-Way movement of substances in the axon
What is the functional class? Sensory (afferent)
Carries impulses to the CNS
What is the functional class? Interneurons( association)
Link incoming sensory impulses to an outgoing motor neuron
Can test for spinal cord damage
Example is the knee-jerk reflex
What functional class? Motor(efferent)
Carrie’s impulses away from the CNS
What is a supportive cell in the CNS?
The neuroglia
How many neurons are there compared to neuroglia
There are about 1 trillion neurons in the body but they are outnumber 25 to 1 by glial cells
Do neurons or neuroglia conduct impulses?
Only neurons
Are neurons our neuroglia capable of mitosis?
Only neuroglia
What are the four types of neuroglia in the CNS
Oligodendrocytes
Astrocytes
Ependymal cells
Microglia(microgliocytes)
What is the job of oligodendrocytes?
Their job is to wrap around axons forming a myelin sheath
What is the job of astrocytes
They are star-shaped
Only lipid soluble substances can pass through this wrapping
They wrap around the capillaries in your brain creating the blood-brain barrier
They prevent toxic substances in your blood from entering your brain( doesn’t always work)
They break down glucose
They absorb excess neurotransmitters for recycling
In case of injury form hard areas in the brain called sclerotic plaque
They regulate the growth and migration of neurons in an embryo
Why do anesthetics have to be lipid soluble
They have to be able to get past the astrocytes which only allow lipid soluble substances to pass
Some examples of lipid soluble drugs
Aspirin alcohol THC( active ingredient in pot)
Ependymal cells or where and help with what
They line the cavities of the brain and spinal cord
Helps circulate CSF with cilia
What are microglia?
Small macrophages
They remove debris
They can form clusters if infection is present
What are the two types of supportive neuroglia cells in the pns?
Schwann cells
Satellite sales
What do Schwann cells do
Form the mile and sheath in the pns
What do satellite cells do in the PNS
Their job is to control the ion concentration in the brain so neurons will function properly
What is a myelin sheath made of
Fatty wrapping
When does the myelin sheath develop
Around the 14th week of gestation but isn’t complete until adolescence which is why dietary fat is important as children grow
What is the difference between myelinated and non-myelinated axons?
axons are the myelinated sheath are said to be myelinated and are called white matter
Unmyelinated axons are called gray matter and do not have a myelin sheath
In the CNS oligodendrocytes, reach out to what
Several axons because of their numerous extensions laying down many layers of its own
membrane with little cytoplasm forming the myelin sheath
What do Schwann cells in the PNS cover
Only one axon laying down several layers of its own cell membrane and forming a myelin sheath. The outermost wrap of the Schwann cell or contain organelles and cytoplasm forming the neurolemia
What is a neurolemia and what does it allow?
It is the outermost layer of a Schwann cell. It contains organelles and allows regeneration
Do oligodendrocytes form neurolemia
No so there is no regeneration tube?
What are the notes of rainvier or mylon sheath gaps?
There are gaps in the myelination of an axon
What are internodes?
myelin covered segments
What is the initial segment
The area between the axle and hillock and the first myelin segment
Which are faster. Myelinated axons or non-myelinated axons
Myelinated axons are faster
