Unit 19: Nervous System Flashcards
The central nervous system (CNS) is the “command center” which includes the brain and spinal cord. It processes and and integrates information. What is the peripheral nervous system (PNS) and how does it differ from the CNS?
The PNS consists of the cranial nerves and the spinal nerves. There are 2 divisions:
-Sensory/afferent division~> sensory receptors that detect stimuli
-Motor/efferent division~> convey impulses away from the CNS and innervates effectors (muscles & glands)
Explain the steps of touching a hot object and quickly withdrawing your hand
Sensory receptors detect the stimuli and signal the CNS, which then sends back a signal for motor neurons, which triggers the effector muscles to withdraw the hand
What are the 2 subdivisions of the motor neurons (PNS)?
Somatic: skeletal muscles
Autonomic: involuntary
-Sympathetic~> fight/flight
-Parasympathetic~> rest, relaxation
When a signal is passed through the CNS, it goes through the _______ center
integration
Describe the cell body of the neuron
Have typical organelles
(Rough ER called Nissl Bodies)
Groups/clusters in:
-CNS = nuclei (gray matter)
-PNS = ganglia
What do dendrites do?
Receive incoming messages and relay them to the cell body
What is the axon hillock?
Where the axon meets the cell body
What are Schwann cells?
Myelin sheath of the PNS
Gaps in the myelin sheath are called ______ __ ______.
Nodes of Ranvier
What are cells that support the neurons called?
Neuroglia (glial cells)
They can undergo mitosis (can cause brain tumours if uncontrolled)
Give the 4 types of neuroglia
that serve the CNS
-Oligodendrocytes: produce myelin
-Microglia: protective—can become phagocytic to inject foreign particles
-Astrocytes: surround capillaries to form part of the blood brain barrier
-Ependymal: neural epithelia, secretes cerebrospinal fluid (CSF)
Give the types of neuroglia that serve the PNS
Schwann cells: form myelin around axons in the PNS
Satellite cells: surround neuron cell bodies in the ganglia—protect/support
Structural/Anatomical and Functional are types of classification for what?
Neurons
In the context of neuron classification, what are the 3 types of structural/anatomical classification?
-Unipolar: 1 process that divides into 2: *CNS and *PNS (peripheral end has dendrites to be sensory receptors)
-Bipolar: 2 processes~> 1 axon, 1 process with dendrites (sensory for retina&nose)
-Multipolar: >2 processes, 1 axon and many dendrites (all interneurons and motor neurons)
The functional classification of neurons focuses on the direction of impulse conduction. What are the types?
Sensory/Afferent neurons: mostly unipolar, from sensory to CNS
Interneurons: within the CNS (between sensory & motor), mostly multipolar
Motor/Efferent neurons: CNS to effectors (all multipolar)
Neuronal, neuromuscular, and neuroglandular are all types of what?
Neuron junctions (synapses)
Neuronal: neuron to neuron
Neuromuscular: motor neuron to skeletal muscle
Neuroglandular: motor neuron to gland
What are the 4 parts that make up a chemical synapse between neurons?
Presynaptic neuron (brings impulse)
Axon terminal (has neurotransmitters)
Synaptic cleft
Postsynaptic neuron (receives impulse)
What are 5 things that serve as protective features for the CNS?
Bone (skull and vertebrae)
Meninges
Cerebrospinal fluid (CSF)
Blood Brain Barrier (BBB)
Cerebral Arterial Circle
The meninges are 3 layers of protective connective tissue around the brain and spinal cord. What are the layers?
Dura mater (outer)
——subdural space——
Arachnoid mater (middle)
——subarachnoid space——
Pia mater (on surface of brain and SC)
What are 2 characteristics of the dura mater layer that are different between the brain and spinal cord?
Brain dura mater (2 layers) is separated in some places to form venous (dural) sinuses, which contain blood
The dura mater layer of the spinal cord has the epidural space superficial to it, filled with fat, blood vessels, CT, etc.
The arachnoid mater layer is avascular and has an area deep to it called the _______ space, which contains _______ _______, and has web-like strands of CT to secure it to the pia mater. It has _______ _______ in the brain only, which projects into the dural sinuses.
subarachnoid, cerebrospinal fluid, arachnoid granulations
What is meningitis?
Inflammation of the meninges
Cerebrospinal fluid (CSF) surrounds the brain and spinal cord. It is in brain ventricles and the spinal canal. What are these ventricles?
2 lateral (1st & 2nd)~> in cerebrum
3rd ventricle~> in diencephalon
4th ventricle~> surrounded by pons, medulla oblongata, and cerebrum
This selectively permeable membrane is made of endothelial cells with tight junctions, wrapped around by astrocytes
Blood brain barrier
What is the cerebral arterial circle?
Arteries which form a circle at the base of the forebrain, which circles the pituitary gland and optic chiasma (where optic nerves cross). It unites the 2 major blood supplies to the brain to provide an alternate route for blood in the case of a blockage
Explain blood RETURN from the brain
Cerebral arteries
Capillaries
Cerebral veins
Dural sinuses
Superior vena cava